I think I used cement that had partially hydrated 50%. So, in effect, I
might have a made a mix that was 6 to 1 or perhaps worse than that. It
certainly was not good enough. When I mixed it I did not know about
hydration. So, that's why the cement was so sandy and weak.

What's happening is that I have a small room that's 118 Cm wide. I'm
putting up shelves 118 Cm wide by  x 61 Cm deep. The distance
between each shelf is 42 Cm. Each shelf will rest on two pieces of
wood one bolted onto the left hand wall and one on the right hand
wall. I'm using M6 x 115mm bolts anchor bolts to bolt the wood
to the walls.

The right hand wall is a concrete wall. The left hand wall I believe is
breese block.

If I chuck out my old cement and get new, I think a 3 sand to 1 cement
mix should be good enough, unless anyone says different.

Now the shelves will have books on and a shelf will be be completely
filled from top to  bottom. So, we have a situation where a shelve
has to hold up a volume of books that is 42 Cm high x 118 Cm
wide and 61 Cm deep. Not sure of the weight but that would
amount to quite a heavy weight on a shelf.

Should I chisel out holes in the breese block and fill these holes with 
mortar. Then drill that out to hold the anchor bolts? TIA.

On 2008-07-17 12:45:09 +0100, "Rich"  said:

> I think I used cement that had partially hydrated 50%. So, in effect, I
> might have a made a mix that was 6 to 1 or perhaps worse than that. It
> certainly was not good enough. When I mixed it I did not know about
> hydration. So, that's why the cement was so sandy and weak.
> 
> What's happening is that I have a small room that's 118 Cm wide. I'm
> putting up shelves 118 Cm wide by  x 61 Cm deep. The distance
> between each shelf is 42 Cm. Each shelf will rest on two pieces of
> wood one bolted onto the left hand wall and one on the right hand
> wall. I'm using M6 x 115mm bolts anchor bolts to bolt the wood
> to the walls.
> 
> The right hand wall is a concrete wall. The left hand wall I believe is
> breese block.
> 
> If I chuck out my old cement and get new, I think a 3 sand to 1 cement
> mix should be good enough, unless anyone says different.
> 
> Now the shelves will have books on and a shelf will be be completely
> filled from top to  bottom. So, we have a situation where a shelve
> has to hold up a volume of books that is 42 Cm high x 118 Cm
> wide and 61 Cm deep. Not sure of the weight but that would
> amount to quite a heavy weight on a shelf.
> 
> Should I chisel out holes in the breese block and fill these holes with 
> mortar. Then drill that out to hold the anchor bolts? TIA.

A much better solution, because of the weight and the weakness of 
breeze blocks would be to use resin injection fittings.    Using these 
involves the use of metal studs of size and length suitable for the 
application.  Holes are drilled for them typically 2mm larger than the 
stud and thoroughly cleaned out.    A two part injection resin, which 
can be applied from a self mixing dispenser or a mastic gun is then 
injected into each hole and the studs inserted immediately afterwards.  
After 4 -24 hrs, depending on the resin, you will have fixings that 
will deal with this application very well and without the attendant 
risks of a poorly filled or crumbly material.

Rich wrote:
> I think I used cement that had partially hydrated 50%. So, in effect, I
> might have a made a mix that was 6 to 1 or perhaps worse than that. It
> certainly was not good enough. When I mixed it I did not know about
> hydration. So, that's why the cement was so sandy and weak.
> 
> What's happening is that I have a small room that's 118 Cm wide. I'm
> putting up shelves 118 Cm wide by  x 61 Cm deep. The distance
> between each shelf is 42 Cm. Each shelf will rest on two pieces of
> wood one bolted onto the left hand wall and one on the right hand
> wall. I'm using M6 x 115mm bolts anchor bolts to bolt the wood
> to the walls.
> 
> The right hand wall is a concrete wall. The left hand wall I believe is
> breese block.
> 
> If I chuck out my old cement and get new, I think a 3 sand to 1 cement
> mix should be good enough, unless anyone says different.
> 
> Now the shelves will have books on and a shelf will be be completely
> filled from top to  bottom. So, we have a situation where a shelve
> has to hold up a volume of books that is 42 Cm high x 118 Cm
> wide and 61 Cm deep. Not sure of the weight but that would
> amount to quite a heavy weight on a shelf.
> 
> Should I chisel out holes in the breese block and fill these holes with 
> mortar. Then drill that out to hold the anchor bolts? TIA.
> 
> 

Suggest resin fixings. Someone else will be along soon to explain more. 
I think I would try many things including wall bolts, multi monty 
screws, before using cement.

In the meantime have a look here:

<http://screwfix.com/prods/25733/Fixings/Injection-Fixing/Injection-Resin-150ml>

... and lots of related products:

<http://screwfix.com/cats/100071/Fixings/Injection-Fixing>

If nothing else, the resin sets quickly (minutes or maybe a few hours) 
where the cement mix will take much longer to be sound enough to take a 
heavy load safely.

-- 
Rod

Hypothyroidism is a seriously debilitating condition with an insidious 
onset.
Although common it frequently goes undiagnosed.
<www.thyromind.info> <www.thyroiduk.org> <www.altsupportthyroid.org>

Rich coughed up some electrons that declared:


> The right hand wall is a concrete wall. The left hand wall I believe is
> breese block.

Breeze block or is it thermalite (also aircrete and various other names)?

IME breeze is crumbly and black/dark grey. The other stuff is light grey and
tends to powder if it's anything like my house.

> 
> If I chuck out my old cement and get new, I think a 3 sand to 1 cement
> mix should be good enough, unless anyone says different.
> 
> Now the shelves will have books on and a shelf will be be completely
> filled from top to  bottom. So, we have a situation where a shelve
> has to hold up a volume of books that is 42 Cm high x 118 Cm
> wide and 61 Cm deep. Not sure of the weight but that would
> amount to quite a heavy weight on a shelf.


> Should I chisel out holes in the breese block and fill these holes with
> mortar. Then drill that out to hold the anchor bolts? TIA.

I used these on thermalite blocks, with a slight smear of epoxy (araldite)
to stop them twisting in the hole when undone:

http://apps.fischer.de/poc/default.aspx?page=details&layertype=Z&sprache=EN&kat=$MART-HK-$MKAT-HK-$MPG-G2-$MZG-FUR-$MUG-F20&ekat=$EKAT-HK-EN

The context was holding up slotted shelf rail, using about 5 fixings per
vertical rail. I would have though they would have been adequate for your
use, providing most of the load is downwards shear and not pull. They are
very long and have lots of toothed grip area, unlike a lot of cheap frame
fixings. They do not have to be used in "frame fixing mode" - I sunk mine
flush with the wall, but that only really works providing the screw head to
wall distance isn't much over about 1/2".

Regarding expanding bolts, I suspect they will be fine in the bare block. If
they actually do up tight rather than letting you turn the bolt forever, it
means they are holding rather than pulling through the block.

If it were me, I'd do a trial with a scrap of wood and a couple of fixings
to see how they behave.

HTH

Tim

Rich wrote:

> I think I used cement that had partially hydrated 50%. So, in effect, I
> might have a made a mix that was 6 to 1 or perhaps worse than that. It
> certainly was not good enough. When I mixed it I did not know about
> hydration. So, that's why the cement was so sandy and weak.

Well 6 to 1 is not bad for a bricklaying mortar anyway. Remember cement 
mixes can take anything up to a month to achieve full cure strength.

A C20 concrete mix (which is a reasonably strong mix) would usually be 
1:2:4 using sand and gravel or 1:6 using all in one ballast.

> What's happening is that I have a small room that's 118 Cm wide. I'm
> putting up shelves 118 Cm wide by  x 61 Cm deep. The distance
> between each shelf is 42 Cm. Each shelf will rest on two pieces of
> wood one bolted onto the left hand wall and one on the right hand
> wall. I'm using M6 x 115mm bolts anchor bolts to bolt the wood
> to the walls.
> 
> The right hand wall is a concrete wall. The left hand wall I believe is
> breese block.
> 
> If I chuck out my old cement and get new, I think a 3 sand to 1 cement
> mix should be good enough, unless anyone says different.

What else is in this wall; Blocks, bricks, rubble etc? If its mostly 
just cement and rubble, you may need to wait a week or so before you go 
drilling it - otherwise it will crumble.

> Now the shelves will have books on and a shelf will be be completely
> filled from top to  bottom. So, we have a situation where a shelve
> has to hold up a volume of books that is 42 Cm high x 118 Cm
> wide and 61 Cm deep. Not sure of the weight but that would
> amount to quite a heavy weight on a shelf.

The weight is actually not that important in this case - the loading is 
almost all in shear - i.e. it will attempt to push the fixings down 
through the wall rather than pull them out. You would probably find 
fixing simply resting in a hole would keep the shelf and its content up!

> Should I chisel out holes in the breese block and fill these holes with 
> mortar. Then drill that out to hold the anchor bolts? TIA.

Depends on what you mean by "breese block" - there are many things that 
get called this, ranging from lightweight thermalite blocks to dense 
concrete ones.

Resin anchors as has been suggested in other posts would work fine. You 
would probably also be ok with longish screws in plugs - say 4" 12 gauge 
  screws.

-- 
Cheers,

John.

/=================================================================\
|          Internode Ltd -  http://www.internode.co.uk            |
|-----------------------------------------------------------------|
|        John Rumm - john(at)internode(dot)co(dot)uk              |
\=================================================================/

Rich wrote:

> 
> What's happening is that I have a small room that's 118 Cm wide. I'm
> putting up shelves 118 Cm wide by  x 61 Cm deep. The distance
> between each shelf is 42 Cm. Each shelf will rest on two pieces of
> wood one bolted onto the left hand wall and one on the right hand
> wall. I'm using M6 x 115mm bolts anchor bolts to bolt the wood
> to the walls.
<snip>
> 
> Now the shelves will have books on and a shelf will be be completely
> filled from top to  bottom. So, we have a situation where a shelve
> has to hold up a volume of books that is 42 Cm high x 118 Cm
> wide and 61 Cm deep. Not sure of the weight but that would
> amount to quite a heavy weight on a shelf.
> 
> Should I chisel out holes in the breese block and fill these holes with 
> mortar. Then drill that out to hold the anchor bolts? TIA.
> 

As others have said, the fixings are in almost pure shear, so I think 
all this exotic resin anchor stuff is ott.  Screw the shelves down into 
the battens and that will remove the last bit of tendency for the 
battens to twist away from the wall.

Could you use timber sides, so the weight is taken on the floor? And 
what sort of shelf do you have in mind to take that sort of weight? 
Could you fit timber uprights between the shelves, again going down to 
the floor, to halve the span? Even a batten along the rear wall would 
help, although the front of the shelf might still droop unless you 
stiffen it with e.g. a bit of 2x1 on edge.

-- 
Kevin Poole
****Use current date to reply (e.g. jun2008@mainbeam.co.uk)****

On 2008-07-17 16:34:14 +0100, Kevin Poole  said:

> 
> 
> Rich wrote:
> 
>> 
>> What's happening is that I have a small room that's 118 Cm wide. I'm
>> putting up shelves 118 Cm wide by  x 61 Cm deep. The distance
>> between each shelf is 42 Cm. Each shelf will rest on two pieces of
>> wood one bolted onto the left hand wall and one on the right hand
>> wall. I'm using M6 x 115mm bolts anchor bolts to bolt the wood
>> to the walls.
> <snip>
>> 
>> Now the shelves will have books on and a shelf will be be completely
>> filled from top to  bottom. So, we have a situation where a shelve
>> has to hold up a volume of books that is 42 Cm high x 118 Cm
>> wide and 61 Cm deep. Not sure of the weight but that would
>> amount to quite a heavy weight on a shelf.
>> 
>> Should I chisel out holes in the breese block and fill these holes with 
>> mortar. Then drill that out to hold the anchor bolts? TIA.
>> 
> 
> As others have said, the fixings are in almost pure shear, so I think 
> all this exotic resin anchor stuff is ott.

What could be exotic about drilling a hole in the wall, cleaning it, 
squirting in a resin filler and pushing in a stud?

Very quick, simple and effective.


>   Screw the shelves down into the battens and that will remove the last 
> bit of tendency for the battens to twist away from the wall.
> 
> Could you use timber sides, so the weight is taken on the floor? And 
> what sort of shelf do you have in mind to take that sort of weight? 
> Could you fit timber uprights between the shelves, again going down to 
> the floor, to halve the span? Even a batten along the rear wall would 
> help, although the front of the shelf might still droop unless you 
> stiffen it with e.g. a bit of 2x1 on edge.

I would say that all this added carpentry is OTT.

On 17 Jul, 16:34, Kevin Poole  wrote:
> Rich wrote:
>
> > What's happening is that I have a small room that's 118 Cm wide. I'm
> > putting up shelves 118 Cm wide by  x 61 Cm deep. The distance
> > between each shelf is 42 Cm. Each shelf will rest on two pieces of
> > wood one bolted onto the left hand wall and one on the right hand
> > wall. I'm using M6 x 115mm bolts anchor bolts to bolt the wood
> > to the walls.
> <snip>
>
> > Now the shelves will have books on and a shelf will be be completely
> > filled from top to  bottom. So, we have a situation where a shelve
> > has to hold up a volume of books that is 42 Cm high x 118 Cm
> > wide and 61 Cm deep. Not sure of the weight but that would
> > amount to quite a heavy weight on a shelf.
>
> > Should I chisel out holes in the breese block and fill these holes with
> > mortar. Then drill that out to hold the anchor bolts? TIA.
>
> As others have said, the fixings are in almost pure shear, so I think
> all this exotic resin anchor stuff is ott.  Screw the shelves down into
> the battens and that will remove the last bit of tendency for the
> battens to twist away from the wall.
>
> Could you use timber sides, so the weight is taken on the floor? And
> what sort of shelf do you have in mind to take that sort of weight?
> Could you fit timber uprights between the shelves, again going down to
> the floor, to halve the span? Even a batten along the rear wall would
> help, although the front of the shelf might still droop unless you
> stiffen it with e.g. a bit of 2x1 on edge.
>
> --
> Kevin Poole
> ****Use current date to reply (e.g. jun2...@mainbeam.co.uk)****

Very longs screw screwed straight into thermalite is good (e.g.
100mm !) If it comes out the other side, so much the better !!
Also, the fancy twist fixings - can't think of the name. They have
very good pullout resistance, but you probably dont need this for
shelves.
Simon.

Andy Hall wrote:
> On 2008-07-17 16:34:14 +0100, Kevin Poole  said:
> 
>>
>>
<snip>

>> As others have said, the fixings are in almost pure shear, so I think 
>> all this exotic resin anchor stuff is ott.
> 
> What could be exotic about drilling a hole in the wall, cleaning it, 
> squirting in a resin filler and pushing in a stud?
> 
> Very quick, simple and effective.
>
Also expensive and requiring PPE to use.  An engineer does, for a penny, 
what any damn fool can do for a pound.

> 
>>   Screw the shelves down into the battens and that will remove the 
>> last bit of tendency for the battens to twist away from the wall.
>>
>> Could you use timber sides, so the weight is taken on the floor? And 
>> what sort of shelf do you have in mind to take that sort of weight? 
>> Could you fit timber uprights between the shelves, again going down to 
>> the floor, to halve the span? Even a batten along the rear wall would 
>> help, although the front of the shelf might still droop unless you 
>> stiffen it with e.g. a bit of 2x1 on edge.
> 
> I would say that all this added carpentry is OTT.
> 

Indeed, if the OP uses an intrinsically stiff enough shelf.  If, for 
reasons of availability, aesthetics, or even (dare I mention it?) cost, 
he wishes to use materials commonly used for shelves, he may find they 
sag more than some would regard as acceptable.


-- 
Kevin Poole
****Use current date to reply (e.g. jun2008@mainbeam.co.uk)****

On 2008-07-17 17:06:18 +0100, Kevin Poole  said:

> 
> 
> Andy Hall wrote:
>> On 2008-07-17 16:34:14 +0100, Kevin Poole  said:
>> 
>>> 
>>> 
> <snip>
> 
>>> As others have said, the fixings are in almost pure shear, so I think 
>>> all this exotic resin anchor stuff is ott.
>> 
>> What could be exotic about drilling a hole in the wall, cleaning it, 
>> squirting in a resin filler and pushing in a stud?
>> 
>> Very quick, simple and effective.
>> 
> Also expensive and requiring PPE to use.  An engineer does, for a 
> penny, what any damn fool can do for a pound.

One needs to look at the context of the project.

These are not an expensive fixing at all.    The whole exercise can be 
done with one tube of resin and probably two boxes of studs.

The important point is the implication of three shelf loads of books 
tumbling down and damaging them plus somebody taking down a book.

Mechanical screwed fixings into breeze blocks can easily cause them to 
crumble or to split.    For this amount of weight, it would be very 
unwise indeed to use them,



> 
>> 
>>>   Screw the shelves down into the battens and that will remove the last 
>>> bit of tendency for the battens to twist away from the wall.
>>> 
>>> Could you use timber sides, so the weight is taken on the floor? And 
>>> what sort of shelf do you have in mind to take that sort of weight? 
>>> Could you fit timber uprights between the shelves, again going down to 
>>> the floor, to halve the span? Even a batten along the rear wall would 
>>> help, although the front of the shelf might still droop unless you 
>>> stiffen it with e.g. a bit of 2x1 on edge.
>> 
>> I would say that all this added carpentry is OTT.
>> 
> 
> Indeed, if the OP uses an intrinsically stiff enough shelf.  If, for 
> reasons of availability, aesthetics, or even (dare I mention it?) cost, 
> he wishes to use materials commonly used for shelves, he may find they 
> sag more than some would regard as acceptable.

That would depend on the material, construction and support.

Andy Hall wrote:
> On 2008-07-17 17:06:18 +0100, Kevin Poole  said:
> 
>>
>>
>> Andy Hall wrote:
>>> On 2008-07-17 16:34:14 +0100, Kevin Poole  said:
>>>
>>>>
>>>>
>> <snip>
>>
>>>> As others have said, the fixings are in almost pure shear, so I 
>>>> think all this exotic resin anchor stuff is ott.
>>>
>>> What could be exotic about drilling a hole in the wall, cleaning it, 
>>> squirting in a resin filler and pushing in a stud?
>>>
>>> Very quick, simple and effective.
>>>
>> Also expensive and requiring PPE to use.  An engineer does, for a 
>> penny, what any damn fool can do for a pound.
> 
> One needs to look at the context of the project.
> 
> These are not an expensive fixing at all.    The whole exercise can be 
> done with one tube of resin and probably two boxes of studs.
> 
> The important point is the implication of three shelf loads of books 
> tumbling down and damaging them plus somebody taking down a book.

High anxiety!

> 
> Mechanical screwed fixings into breeze blocks can easily cause them to 
> crumble or to split.    For this amount of weight, it would be very 
> unwise indeed to use them,

Unwise my arse! A kitchen cupboard full of plates hangs quite happily on 
a couple of 2" screws.

On 2008-07-17 18:46:06 +0100, stuart noble  said:

> Andy Hall wrote:
>> 
>> The important point is the implication of three shelf loads of books 
>> tumbling down and damaging them plus somebody taking down a book.
> 
> High anxiety!

You would probably hink so if they fell on your bonce.


> 
>> 
>> Mechanical screwed fixings into breeze blocks can easily cause them to 
>> crumble or to split.    For this amount of weight, it would be very 
>> unwise indeed to use them,
> 
> Unwise my arse!

That I can imagine.

> A kitchen cupboard full of plates hangs quite happily on a couple of 2" screws.

Having very considerably less weight than a shelf full of books.

Andy Hall wrote:
> On 2008-07-17 18:46:06 +0100, stuart noble  
> said:
> 
>> Andy Hall wrote:
>>>
>>> The important point is the implication of three shelf loads of books 
>>> tumbling down and damaging them plus somebody taking down a book.
>>
>> High anxiety!
> 
> You would probably hink so if they fell on your bonce.
> 
> 
>>
>>>
>>> Mechanical screwed fixings into breeze blocks can easily cause them 
>>> to crumble or to split.    For this amount of weight, it would be 
>>> very unwise indeed to use them,
>>
>> Unwise my arse!
> 
> That I can imagine.
> 
>> A kitchen cupboard full of plates hangs quite happily on a couple of 
>> 2" screws.
> 
> Having very considerably less weight than a shelf full of books.
> 
> 

Funny, I always thought china weighed more than paper

Andy Hall wrote:

> On 2008-07-17 12:45:09 +0100, "Rich"  said:
> 
>> I think I used cement that had partially hydrated 50%. So, in effect, I
>> might have a made a mix that was 6 to 1 or perhaps worse than that. It
>> certainly was not good enough. When I mixed it I did not know about
>> hydration. So, that's why the cement was so sandy and weak.
>>
>> What's happening is that I have a small room that's 118 Cm wide. I'm
>> putting up shelves 118 Cm wide by  x 61 Cm deep. The distance
>> between each shelf is 42 Cm. Each shelf will rest on two pieces of
>> wood one bolted onto the left hand wall and one on the right hand
>> wall. I'm using M6 x 115mm bolts anchor bolts to bolt the wood
>> to the walls.
>>
>> The right hand wall is a concrete wall. The left hand wall I believe is
>> breese block.
>>
>> If I chuck out my old cement and get new, I think a 3 sand to 1 cement
>> mix should be good enough, unless anyone says different.
>>
>> Now the shelves will have books on and a shelf will be be completely
>> filled from top to  bottom. So, we have a situation where a shelve
>> has to hold up a volume of books that is 42 Cm high x 118 Cm
>> wide and 61 Cm deep. Not sure of the weight but that would
>> amount to quite a heavy weight on a shelf.
>>
>> Should I chisel out holes in the breese block and fill these holes 
>> with mortar. Then drill that out to hold the anchor bolts? TIA.
> 
> 
> A much better solution, because of the weight and the weakness of breeze 
> blocks would be to use resin injection fittings.    Using these involves 
> the use of metal studs of size and length suitable for the application.  
> Holes are drilled for them typically 2mm larger than the stud and 
> thoroughly cleaned out.    A two part injection resin, which can be 
> applied from a self mixing dispenser or a mastic gun is then injected 
> into each hole and the studs inserted immediately afterwards.  After 4 
> -24 hrs, depending on the resin, you will have fixings that will deal 
> with this application very well and without the attendant risks of a 
> poorly filled or crumbly material.

An added attraction to this idea is that the stud is only loaded in 
shear and has no tension on it. I would think your idea would be fine 
for this job.

Dave

stuart noble wrote:
<>
> 
> Funny, I always thought china weighed more than paper

In terms of density, it is usually denser.

(In kg per cubic metre.)
Porcelain – 2403
Paper – 1201
Cardboard - 689
Couldn't find 'china' - thought porcelain reasonable approximation.)

But it is very rare to see solid china wall-to-wall along a shelf. Most 
china is hollow or flat-ish and round - neither of which packs 
particularly well. You might just about manage it with something like 
bricks. Whereas books can very nearly fill the total space available 
between two shelves.

What we care about is surely the weight of a shelf-load of books versus 
china. And I would put a small wager on Andy being right.

-- 
Rod

Hypothyroidism is a seriously debilitating condition with an insidious 
onset.
Although common it frequently goes undiagnosed.
<www.thyromind.info> <www.thyroiduk.org> <www.altsupportthyroid.org>

On 2008-07-17 19:23:22 +0100, stuart noble  said:

> Andy Hall wrote:
>> On 2008-07-17 18:46:06 +0100, stuart noble  said:
>> 
>>> Andy Hall wrote:
>>>> 
>>>> The important point is the implication of three shelf loads of books 
>>>> tumbling down and damaging them plus somebody taking down a book.
>>> 
>>> High anxiety!
>> 
>> You would probably hink so if they fell on your bonce.
>> 
>> 
>>> 
>>>> 
>>>> Mechanical screwed fixings into breeze blocks can easily cause them to 
>>>> crumble or to split.    For this amount of weight, it would be very 
>>>> unwise indeed to use them,
>>> 
>>> Unwise my arse!
>> 
>> That I can imagine.
>> 
>>> A kitchen cupboard full of plates hangs quite happily on a couple of 2" screws.
>> 
>> Having very considerably less weight than a shelf full of books.
>> 
>> 
> 
> Funny, I always thought china weighed more than paper

Which is heavier?   A kilo of feathers or a kilo of lead?

"Andy Hall" <andyh@hall.nospam> wrote in message news:487f9832@qaanaaq...


> Which is heavier?   A kilo of feathers or a kilo of lead?
> 
>

Either depending on how they are stored.

dennis@home wrote:
> 
> 
> "Andy Hall" <andyh@hall.nospam> wrote in message news:487f9832@qaanaaq...
> 
> 
>> Which is heavier?   A kilo of feathers or a kilo of lead?
>>
>>
> 
> Either depending on how they are stored.

Unless you are playing at quirky things like one being stored on the ISS 
and the other on the desk, the change in moisture content of feathers, 
or similar unlikely ideas, I do not understand what storage method has 
to do with it.

-- 
Rod

Hypothyroidism is a seriously debilitating condition with an insidious 
onset.
Although common it frequently goes undiagnosed.
<www.thyromind.info> <www.thyroiduk.org> <www.altsupportthyroid.org>

Dave wrote:
> Andy Hall wrote:
>> A much better solution, because of the weight and the weakness of
>> breeze blocks would be to use resin injection fittings.    Using
>> these involves the use of metal studs of size and length suitable
>> for the application. Holes are drilled for them typically 2mm larger
>> than the stud and thoroughly cleaned out.    A two part injection
>> resin, which can be applied from a self mixing dispenser or a mastic
>> gun is then injected into each hole and the studs inserted
>> immediately afterwards.  After 4 -24 hrs, depending on the resin,
>> you will have fixings that will deal with this application very well
>> and without the attendant risks of a poorly filled or crumbly
>> material.
>
> An added attraction to this idea is that the stud is only loaded in
> shear and has no tension on it. I would think your idea would be fine
> for this job.

Indeed - you can't beat resin for strong breezeblock fixings.

"Rod"  wrote in message 
news:6e9nr4F62mhgU1@mid.individual.net...
> dennis@home wrote:
>>
>>
>> "Andy Hall" <andyh@hall.nospam> wrote in message news:487f9832@qaanaaq...
>>
>>
>>> Which is heavier?   A kilo of feathers or a kilo of lead?
>>>
>>>
>>
>> Either depending on how they are stored.
>
> Unless you are playing at quirky things like one being stored on the ISS 
> and the other on the desk, the change in moisture content of feathers, or 
> similar unlikely ideas, I do not understand what storage method has to do 
> with it.

Well for one a kilo of feathers would be more buoyant than lead in most 
cases so it would weigh less.
For instance a kilo of hydrogen would weigh negative under normal 
conditions.

Andy Hall wrote:

> Which is heavier?   A kilo of feathers or a kilo of lead?

Probably the lead - slightly.


-- 
Cheers,

John.

/=================================================================\
|          Internode Ltd -  http://www.internode.co.uk            |
|-----------------------------------------------------------------|
|        John Rumm - john(at)internode(dot)co(dot)uk              |
\=================================================================/

John Rumm wrote:

> Andy Hall wrote:
> 
>> Which is heavier?   A kilo of feathers or a kilo of lead?
> 
> 
> Probably the lead - slightly.

But a kilo of each was specified. If they were both measured on the same 
set of scales, how could they weigh differently?  :-)

Dave

dennis@home wrote:
> 
> 
> "Rod"  wrote in message 
> news:6e9nr4F62mhgU1@mid.individual.net...
>> dennis@home wrote:
>>>
>>>
>>> "Andy Hall" <andyh@hall.nospam> wrote in message 
>>> news:487f9832@qaanaaq...
>>>
>>>
>>>> Which is heavier?   A kilo of feathers or a kilo of lead?
>>>>
>>>>
>>>
>>> Either depending on how they are stored.
>>
>> Unless you are playing at quirky things like one being stored on the 
>> ISS and the other on the desk, the change in moisture content of 
>> feathers, or similar unlikely ideas, I do not understand what storage 
>> method has to do with it.
> 
> Well for one a kilo of feathers would be more buoyant than lead in most 
> cases so it would weigh less.
> For instance a kilo of hydrogen would weigh negative under normal 
> conditions.

the lead will also occupy a smaller volume and hence will likely have a 
lower centre of gravity, so G (m1 m2 / d^2) will be larger, making it 
heavier even without taking into account the buoyancy.

-- 
Cheers,

John.

/=================================================================\
|          Internode Ltd -  http://www.internode.co.uk            |
|-----------------------------------------------------------------|
|        John Rumm - john(at)internode(dot)co(dot)uk              |
\=================================================================/

> >> Which is heavier?   A kilo of feathers or a kilo of lead?
> > Probably the lead - slightly.
> But a kilo of each was specified. If they were both measured on the same 
> set of scales, how could they weigh differently?  :-)

I know which one i'd rather have thrown at me :-p

On Fri, 18 Jul 2008 00:25:40 +0100, Dave 
wrote:

>John Rumm wrote:
>
>> Andy Hall wrote:
>> 
>>> Which is heavier?   A kilo of feathers or a kilo of lead?
>> 
>> 
>> Probably the lead - slightly.
>
>But a kilo of each was specified. If they were both measured on the same 
>set of scales, how could they weigh differently?  :-)
>
It all depends on what you mean by a 'kilo'.

-- 
Frank Erskine

On Jul 17, 12:45 pm, "Rich"  wrote:

> I think I used cement that had partially hydrated 50%. So, in effect, I
> might have a made a mix that was 6 to 1 or perhaps worse than that. It
> certainly was not good enough. When I mixed it I did not know about
> hydration. So, that's why the cement was so sandy and weak.
>
> What's happening is that I have a small room that's 118 Cm wide. I'm
> putting up shelves 118 Cm wide by  x 61 Cm deep. The distance
> between each shelf is 42 Cm. Each shelf will rest on two pieces of
> wood one bolted onto the left hand wall and one on the right hand
> wall. I'm using M6 x 115mm bolts anchor bolts to bolt the wood
> to the walls.
>
> The right hand wall is a concrete wall. The left hand wall I believe is
> breese block.
>
> If I chuck out my old cement and get new, I think a 3 sand to 1 cement
> mix should be good enough, unless anyone says different.
>
> Now the shelves will have books on and a shelf will be be completely
> filled from top to  bottom. So, we have a situation where a shelve
> has to hold up a volume of books that is 42 Cm high x 118 Cm
> wide and 61 Cm deep. Not sure of the weight but that would
> amount to quite a heavy weight on a shelf.
>
> Should I chisel out holes in the breese block and fill these holes with
> mortar. Then drill that out to hold the anchor bolts? TIA.



Fixings might be an issue, and the perfectionist's answer is surely
resin fixings. But it should be ok with plugs & screws (use plenty
of).

What will undoubtedly be an issue is shelf sag. It would take an
exceptionally strong material not to sag with just end supports with a
42cm high 2' deep stack of books. You'll need to support these on all
4 sides, not just 3. 2x2 should do.

This should help to avoid the problem:
http://www.woodbin.com/calcs/sagulator.htm


NT

John Rumm wrote:
> dennis@home wrote:
>>
>>
>> "Rod"  wrote in message 
>> news:6e9nr4F62mhgU1@mid.individual.net...
>>> dennis@home wrote:
>>>>
>>>>
>>>> "Andy Hall" <andyh@hall.nospam> wrote in message 
>>>> news:487f9832@qaanaaq...
>>>>
>>>>
>>>>> Which is heavier?   A kilo of feathers or a kilo of lead?
>>>>>
>>>>>
>>>>
>>>> Either depending on how they are stored.
>>>
>>> Unless you are playing at quirky things like one being stored on the 
>>> ISS and the other on the desk, the change in moisture content of 
>>> feathers, or similar unlikely ideas, I do not understand what storage 
>>> method has to do with it.
>>
>> Well for one a kilo of feathers would be more buoyant than lead in 
>> most cases so it would weigh less.
>> For instance a kilo of hydrogen would weigh negative under normal 
>> conditions.
> 
> the lead will also occupy a smaller volume and hence will likely have a 
> lower centre of gravity, so G (m1 m2 / d^2) will be larger, making it 
> heavier even without taking into account the buoyancy.
> 

Dennis,

Just bear in mind that this post has the context of objects on a shelf 
in a room - not JPL.

So the shelf is going to have to be super strong to hold up a bath as 
well? Well and truly classified in "unlikely ideas".

And in what way does the water affect the gravitional force acting on 
the body? Sure, it might make it awkward to measure directly, but the 
body still has the same force of gravity acting on it - merely has 
buoyancy countering it.

John,

There is this weird idea in science that things must be measurable. I 
suspect that in any real world way, the difference would be so small as 
to be utterly unmeasurable. Certainly in the open air on an ordinary 
shelf. However well fixed with resin or bolts. But theoretically there 
might indeed be a difference if the items are re-formed into different 
shapes.

-- 
Rod

Hypothyroidism is a seriously debilitating condition with an insidious 
onset.
Although common it frequently goes undiagnosed.
<www.thyromind.info> <www.thyroiduk.org> <www.altsupportthyroid.org>

"John Rumm"  wrote in message 
news:K8mdnbD64sHuVuLVnZ2dnUVZ8hmdnZ2d@posted.plusnet...
> dennis@home wrote:
>>
>>
>> "Rod"  wrote in message 
>> news:6e9nr4F62mhgU1@mid.individual.net...
>>> dennis@home wrote:
>>>>
>>>>
>>>> "Andy Hall" <andyh@hall.nospam> wrote in message 
>>>> news:487f9832@qaanaaq...
>>>>
>>>>
>>>>> Which is heavier?   A kilo of feathers or a kilo of lead?
>>>>>
>>>>>
>>>>
>>>> Either depending on how they are stored.
>>>
>>> Unless you are playing at quirky things like one being stored on the ISS 
>>> and the other on the desk, the change in moisture content of feathers, 
>>> or similar unlikely ideas, I do not understand what storage method has 
>>> to do with it.
>>
>> Well for one a kilo of feathers would be more buoyant than lead in most 
>> cases so it would weigh less.
>> For instance a kilo of hydrogen would weigh negative under normal 
>> conditions.
>
> the lead will also occupy a smaller volume and hence will likely have a 
> lower centre of gravity, so G (m1 m2 / d^2) will be larger, making it 
> heavier even without taking into account the buoyancy.

Not if the pile of feathers were the same height as the lead.

They would still be more buoyant though.

"Dave"  wrote in message 
news:kOudnWaci9VqSeLVnZ2dnUVZ8vydnZ2d@bt.com...
> John Rumm wrote:
>
>> Andy Hall wrote:
>>
>>> Which is heavier?   A kilo of feathers or a kilo of lead?
>>
>>
>> Probably the lead - slightly.
>
> But a kilo of each was specified. If they were both measured on the same 
> set of scales, how could they weigh differently?  :-)

Well he is obviously referring to mass or he wouldn't need to weigh them. 
;-)

>
> Dave

dennis@home wrote:
> 
> 
> "John Rumm"  wrote in message 
> news:K8mdnbD64sHuVuLVnZ2dnUVZ8hmdnZ2d@posted.plusnet...
>> dennis@home wrote:
>>>
>>>
>>> "Rod"  wrote in message 
>>> news:6e9nr4F62mhgU1@mid.individual.net...
>>>> dennis@home wrote:
>>>>>
>>>>>
>>>>> "Andy Hall" <andyh@hall.nospam> wrote in message 
>>>>> news:487f9832@qaanaaq...
>>>>>
>>>>>
>>>>>> Which is heavier?   A kilo of feathers or a kilo of lead?
>>>>>>
>>>>>>
>>>>>
>>>>> Either depending on how they are stored.
>>>>
>>>> Unless you are playing at quirky things like one being stored on the 
>>>> ISS and the other on the desk, the change in moisture content of 
>>>> feathers, or similar unlikely ideas, I do not understand what 
>>>> storage method has to do with it.
>>>
>>> Well for one a kilo of feathers would be more buoyant than lead in 
>>> most cases so it would weigh less.
>>> For instance a kilo of hydrogen would weigh negative under normal 
>>> conditions.
>>
>> the lead will also occupy a smaller volume and hence will likely have 
>> a lower centre of gravity, so G (m1 m2 / d^2) will be larger, making 
>> it heavier even without taking into account the buoyancy.
> 
> Not if the pile of feathers were the same height as the lead.
> 
> They would still be more buoyant though.

The word "likely" was used by John to indicate that this was not certain.

The buoyancy depends on shape. It would be possible in the fanastical 
way you are treating this thread to imagine a model ship made of lead 
that easily floated. And a super-dense package of feathers that at the 
least only just floated.

-- 
Rod

Hypothyroidism is a seriously debilitating condition with an insidious 
onset.
Although common it frequently goes undiagnosed.
<www.thyromind.info> <www.thyroiduk.org> <www.altsupportthyroid.org>

"Rod"  wrote in message 
news:6eb0ipF66kceU1@mid.individual.net...
> dennis@home wrote:
>>
>>
>> "John Rumm"  wrote in message 
>> news:K8mdnbD64sHuVuLVnZ2dnUVZ8hmdnZ2d@posted.plusnet...
>>> dennis@home wrote:
>>>>
>>>>
>>>> "Rod"  wrote in message 
>>>> news:6e9nr4F62mhgU1@mid.individual.net...
>>>>> dennis@home wrote:
>>>>>>
>>>>>>
>>>>>> "Andy Hall" <andyh@hall.nospam> wrote in message 
>>>>>> news:487f9832@qaanaaq...
>>>>>>
>>>>>>
>>>>>>> Which is heavier?   A kilo of feathers or a kilo of lead?
>>>>>>>
>>>>>>>
>>>>>>
>>>>>> Either depending on how they are stored.
>>>>>
>>>>> Unless you are playing at quirky things like one being stored on the 
>>>>> ISS and the other on the desk, the change in moisture content of 
>>>>> feathers, or similar unlikely ideas, I do not understand what storage 
>>>>> method has to do with it.
>>>>
>>>> Well for one a kilo of feathers would be more buoyant than lead in most 
>>>> cases so it would weigh less.
>>>> For instance a kilo of hydrogen would weigh negative under normal 
>>>> conditions.
>>>
>>> the lead will also occupy a smaller volume and hence will likely have a 
>>> lower centre of gravity, so G (m1 m2 / d^2) will be larger, making it 
>>> heavier even without taking into account the buoyancy.
>>
>> Not if the pile of feathers were the same height as the lead.
>>
>> They would still be more buoyant though.
>
> The word "likely" was used by John to indicate that this was not certain.
>
> The buoyancy depends on shape. It would be possible in the fanastical way 
> you are treating this thread to imagine a model ship made of lead that 
> easily floated. And a super-dense package of feathers that at the least 
> only just floated.
>

No. Ships float because they are made of metal (or wood, or concrete) *and* 
air. You cannot make a solid lead boat of any shape that floats due to 
buoyancy (a lead monolayer might float due to surface tension). Buoyancy at 
a water/air interface depends on shape. If the lead boat sunk it would still 
have a buoyancy (while sinking - granted less than its weight) independent 
of its shape.

If we assume feathers are made of keratin, you are correct on the second 
point (as it happens), as the density of keratin is not far off that for 
water and, at their crush limit, they may either float or not. A feather 
will float but that has little to do with bouyancy but a lot to do with 
surface tension. A fully wetted feather, under water would be around zero 
buoyancy and might sink or float.


-- 
Bob Mannix
(anti-spam is as easy as 1-2-3 - not)> -- 
> Rod
>
> Hypothyroidism is a seriously debilitating condition with an insidious 
> onset.
> Although common it frequently goes undiagnosed.
> <www.thyromind.info> <www.thyroiduk.org> <www.altsupportthyroid.org>

Bob Mannix wrote:
> "Frank Erskine"  wrote in message 
> news:fvmv741vvtsnsi1u7lnbvt3c9lgn5vni79@4ax.com...
>> On Fri, 18 Jul 2008 00:25:40 +0100, Dave 
>> wrote:
>>
>>> John Rumm wrote:
>>>
>>>> Andy Hall wrote:
>>>>
>>>>> Which is heavier?   A kilo of feathers or a kilo of lead?
>>>>
>>>> Probably the lead - slightly.
>>> But a kilo of each was specified. If they were both measured on the same
>>> set of scales, how could they weigh differently?  :-)
>>>
>> It all depends on what you mean by a 'kilo'.
> 
> Indeed, a kilometre of lead would weigh *considerably* more than a kilometre 
> of feathers (all other dimensions being equal). A kilogram mass of both 
> would weigh the same in a vacuum however and a kilogram weight of both 
> would, of necessity, weigh the same anywhere they were weighed..
> 
> If we take the mass of each to be 1kg and want to know how much they weigh 
> in air (roughly):
> 
> Lets say feathers are made of keratin, which has a density of something like 
> 1300kg/m**3 and round it down to 1000kg/m**3, as the keratin fibres may not 
> be completely solid. Lead has a density of 11,000kg/m**3. To make the maths 
> easy, let's call that 10,000kg/m**3.
> 
> 1 kilogram of lead will occupy a volume of 100cm**3
> 1 kilogram of feathers (after they are crushed to exclude the free air that 
> does not form part of them) will occupy 1000cm**3
> 
> The buoyancy due to the air on the lead will be 0.12g and that on the 
> feathers 1.2g (at STP in air)
> 
> Therefore a kilogram mass of feathers will be lighter by about 1g than the 
> same mass of lead, at STP in air (give or take).
> 
> I reckon.
> 
> 
Ar, but you could make a hollow cube out of the lead and evacuate it. 
Then work out its buoyancy... :-)

(Of course you're likely to want to store these things on your shelf 
along with the books and the china. And 1.2g isn't going to make much 
difference between resin, cement, bolts or holding the shelf up by 
mental effort.)

-- 
Rod

Hypothyroidism is a seriously debilitating condition with an insidious 
onset.
Although common it frequently goes undiagnosed.
<www.thyromind.info> <www.thyroiduk.org> <www.altsupportthyroid.org>

"Rod"  wrote in message 
news:6eb19tF69g8uU1@mid.individual.net...
> Bob Mannix wrote:
>> "Frank Erskine"  wrote in message 
>> news:fvmv741vvtsnsi1u7lnbvt3c9lgn5vni79@4ax.com...
>>> On Fri, 18 Jul 2008 00:25:40 +0100, Dave 
>>> wrote:
>>>
>>>> John Rumm wrote:
>>>>
>>>>> Andy Hall wrote:
>>>>>
>>>>>> Which is heavier?   A kilo of feathers or a kilo of lead?
>>>>>
>>>>> Probably the lead - slightly.
>>>> But a kilo of each was specified. If they were both measured on the 
>>>> same
>>>> set of scales, how could they weigh differently?  :-)
>>>>
>>> It all depends on what you mean by a 'kilo'.
>>
>> Indeed, a kilometre of lead would weigh *considerably* more than a 
>> kilometre of feathers (all other dimensions being equal). A kilogram mass 
>> of both would weigh the same in a vacuum however and a kilogram weight of 
>> both would, of necessity, weigh the same anywhere they were weighed..
>>
>> If we take the mass of each to be 1kg and want to know how much they 
>> weigh in air (roughly):
>>
>> Lets say feathers are made of keratin, which has a density of something 
>> like 1300kg/m**3 and round it down to 1000kg/m**3, as the keratin fibres 
>> may not be completely solid. Lead has a density of 11,000kg/m**3. To make 
>> the maths easy, let's call that 10,000kg/m**3.
>>
>> 1 kilogram of lead will occupy a volume of 100cm**3
>> 1 kilogram of feathers (after they are crushed to exclude the free air 
>> that does not form part of them) will occupy 1000cm**3
>>
>> The buoyancy due to the air on the lead will be 0.12g and that on the 
>> feathers 1.2g (at STP in air)
>>
>> Therefore a kilogram mass of feathers will be lighter by about 1g than 
>> the same mass of lead, at STP in air (give or take).
>>
>> I reckon.
>>
>>
> Ar, but you could make a hollow cube out of the lead and evacuate it. Then 
> work out its buoyancy... :-)
>
> (Of course you're likely to want to store these things on your shelf along 
> with the books and the china. And 1.2g isn't going to make much difference 
> between resin, cement, bolts or holding the shelf up by mental effort.)
>

A hollow lead cube (whether evacuated of not) is still not solid! It would 
be slightly lighter than if air filled.

(Resin? Bolts? We're way past that :o) Stick some bloody screws in, they are 
in shear and won't give way - the shelf will bend. Personally I would use 
spur shelving spaced 1/3, 2/3, 1/3 myself but what do I know - who cares, 
putting shelves up was how we all learned about DIY to start with, wasn't 
it?!)



-- 
Bob Mannix
(anti-spam is as easy as 1-2-3 - not)

Bob Mannix wrote:
<>
> 
> No. Ships float because they are made of metal (or wood, or concrete) *and* 
> air. You cannot make a solid lead boat of any shape that floats due to 
> buoyancy (a lead monolayer might float due to surface tension). Buoyancy at 
> a water/air interface depends on shape. If the lead boat sunk it would still 
> have a buoyancy (while sinking - granted less than its weight) independent 
> of its shape.
> 
Sorry if it wasn't clear - I meant a hollow model ship. I thought the 
whole Titanic would be a bit ambitiuous for a single kg of lead so just 
settled for an average model ship. (I can't help but think that if it is 
a model is must approximate to the hollowness of the real thing it is 
based on. But that's me.)

BTW - is there a standard way of defining hollowness of an object?

-- 
Rod

Hypothyroidism is a seriously debilitating condition with an insidious 
onset.
Although common it frequently goes undiagnosed.
<www.thyromind.info> <www.thyroiduk.org> <www.altsupportthyroid.org>

Bob Mannix wrote:
> "Rod"  wrote in message 
> news:6eb0ipF66kceU1@mid.individual.net...
>> dennis@home wrote:
>>>
>>> "John Rumm"  wrote in message 
>>> news:K8mdnbD64sHuVuLVnZ2dnUVZ8hmdnZ2d@posted.plusnet...
>>>> dennis@home wrote:
>>>>>
>>>>> "Rod"  wrote in message 
>>>>> news:6e9nr4F62mhgU1@mid.individual.net...
>>>>>> dennis@home wrote:
>>>>>>>
>>>>>>> "Andy Hall" <andyh@hall.nospam> wrote in message 
>>>>>>> news:487f9832@qaanaaq...
>>>>>>>
>>>>>>>
>>>>>>>> Which is heavier?   A kilo of feathers or a kilo of lead?
>>>>>>>>
>>>>>>>>
>>>>>>> Either depending on how they are stored.
>>>>>> Unless you are playing at quirky things like one being stored on the 
>>>>>> ISS and the other on the desk, the change in moisture content of 
>>>>>> feathers, or similar unlikely ideas, I do not understand what storage 
>>>>>> method has to do with it.
>>>>> Well for one a kilo of feathers would be more buoyant than lead in most 
>>>>> cases so it would weigh less.
>>>>> For instance a kilo of hydrogen would weigh negative under normal 
>>>>> conditions.
>>>> the lead will also occupy a smaller volume and hence will likely have a 
>>>> lower centre of gravity, so G (m1 m2 / d^2) will be larger, making it 
>>>> heavier even without taking into account the buoyancy.
>>> Not if the pile of feathers were the same height as the lead.
>>>
>>> They would still be more buoyant though.
>> The word "likely" was used by John to indicate that this was not certain.
>>
>> The buoyancy depends on shape. It would be possible in the fanastical way 
>> you are treating this thread to imagine a model ship made of lead that 
>> easily floated. And a super-dense package of feathers that at the least 
>> only just floated.
>>
> 
> No. Ships float because they are made of metal (or wood, or concrete) *and* 
> air. You cannot make a solid lead boat of any shape that floats due to 
> buoyancy (a lead monolayer might float due to surface tension). Buoyancy at 
> a water/air interface depends on shape. If the lead boat sunk it would still 
> have a buoyancy (while sinking - granted less than its weight) independent 
> of its shape.
> 
> If we assume feathers are made of keratin, you are correct on the second 
> point (as it happens), as the density of keratin is not far off that for 
> water and, at their crush limit, they may either float or not. A feather 
> will float but that has little to do with bouyancy but a lot to do with 
> surface tension. A fully wetted feather, under water would be around zero 
> buoyancy and might sink or float.
> 
> 
well, you would hve to fill the quill first. ISTR they used to be used 
to make fishing floats..

"Frank Erskine"  wrote in message 
news:fvmv741vvtsnsi1u7lnbvt3c9lgn5vni79@4ax.com...
> On Fri, 18 Jul 2008 00:25:40 +0100, Dave 
> wrote:
>
>>John Rumm wrote:
>>
>>> Andy Hall wrote:
>>>
>>>> Which is heavier?   A kilo of feathers or a kilo of lead?
>>>
>>>
>>> Probably the lead - slightly.
>>
>>But a kilo of each was specified. If they were both measured on the same
>>set of scales, how could they weigh differently?  :-)
>>
> It all depends on what you mean by a 'kilo'.

Indeed, a kilometre of lead would weigh *considerably* more than a kilometre 
of feathers (all other dimensions being equal). A kilogram mass of both 
would weigh the same in a vacuum however and a kilogram weight of both 
would, of necessity, weigh the same anywhere they were weighed..

If we take the mass of each to be 1kg and want to know how much they weigh 
in air (roughly):

Lets say feathers are made of keratin, which has a density of something like 
1300kg/m**3 and round it down to 1000kg/m**3, as the keratin fibres may not 
be completely solid. Lead has a density of 11,000kg/m**3. To make the maths 
easy, let's call that 10,000kg/m**3.

1 kilogram of lead will occupy a volume of 100cm**3
1 kilogram of feathers (after they are crushed to exclude the free air that 
does not form part of them) will occupy 1000cm**3

The buoyancy due to the air on the lead will be 0.12g and that on the 
feathers 1.2g (at STP in air)

Therefore a kilogram mass of feathers will be lighter by about 1g than the 
same mass of lead, at STP in air (give or take).

I reckon.


-- 
Bob Mannix
(anti-spam is as easy as 1-2-3 - not) >
> -- 
> Frank Erskine

Bob Mannix wrote:
> "Rod"  wrote in message 
> news:6eb19tF69g8uU1@mid.individual.net...
>> Bob Mannix wrote:
>>> "Frank Erskine"  wrote in message 
>>> news:fvmv741vvtsnsi1u7lnbvt3c9lgn5vni79@4ax.com...
>>>> On Fri, 18 Jul 2008 00:25:40 +0100, Dave 
>>>> wrote:
>>>>
>>>>> John Rumm wrote:
>>>>>
>>>>>> Andy Hall wrote:
>>>>>>
>>>>>>> Which is heavier?   A kilo of feathers or a kilo of lead?
>>>>>> Probably the lead - slightly.
>>>>> But a kilo of each was specified. If they were both measured on the 
>>>>> same
>>>>> set of scales, how could they weigh differently?  :-)
>>>>>
>>>> It all depends on what you mean by a 'kilo'.
>>> Indeed, a kilometre of lead would weigh *considerably* more than a 
>>> kilometre of feathers (all other dimensions being equal). A kilogram mass 
>>> of both would weigh the same in a vacuum however and a kilogram weight of 
>>> both would, of necessity, weigh the same anywhere they were weighed..
>>>
>>> If we take the mass of each to be 1kg and want to know how much they 
>>> weigh in air (roughly):
>>>
>>> Lets say feathers are made of keratin, which has a density of something 
>>> like 1300kg/m**3 and round it down to 1000kg/m**3, as the keratin fibres 
>>> may not be completely solid. Lead has a density of 11,000kg/m**3. To make 
>>> the maths easy, let's call that 10,000kg/m**3.
>>>
>>> 1 kilogram of lead will occupy a volume of 100cm**3
>>> 1 kilogram of feathers (after they are crushed to exclude the free air 
>>> that does not form part of them) will occupy 1000cm**3
>>>
>>> The buoyancy due to the air on the lead will be 0.12g and that on the 
>>> feathers 1.2g (at STP in air)
>>>
>>> Therefore a kilogram mass of feathers will be lighter by about 1g than 
>>> the same mass of lead, at STP in air (give or take).
>>>
>>> I reckon.
>>>
>>>
>> Ar, but you could make a hollow cube out of the lead and evacuate it. Then 
>> work out its buoyancy... :-)
>>
>> (Of course you're likely to want to store these things on your shelf along 
>> with the books and the china. And 1.2g isn't going to make much difference 
>> between resin, cement, bolts or holding the shelf up by mental effort.)
>>
> 
> A hollow lead cube (whether evacuated of not) is still not solid! It would 
> be slightly lighter than if air filled.
> 
> (Resin? Bolts? We're way past that :o) Stick some bloody screws in, they are 
> in shear and won't give way - the shelf will bend. Personally I would use 
> spur shelving spaced 1/3, 2/3, 1/3 myself but what do I know - who cares, 
> putting shelves up was how we all learned about DIY to start with, wasn't 
> it?!)
> 
> 

But why should the lead cube be solid? Not part of Andy's question. I 
was just trying to get the buoyancies the same/similar for the feathers 
and the lead to remove it from consideration.

The evacuation was simply to avoid anyone suggesting that the weight or 
the mass of the air inside had any relevance at all.

Perhaps the easiest ways of getting differences are things like weighing 
  one at the top of a mountain the other at ground level. Or over 
gravitational anomlies. Saves a lot of lead bashing and feather squishing.

-- 
Rod

Hypothyroidism is a seriously debilitating condition with an insidious 
onset.
Although common it frequently goes undiagnosed.
<www.thyromind.info> <www.thyroiduk.org> <www.altsupportthyroid.org>

The Natural Philosopher wrote:
> Bob Mannix wrote:
>> "Rod"  wrote in message 
>> news:6eb0ipF66kceU1@mid.individual.net...
>>> dennis@home wrote:
>>>>
>>>> "John Rumm"  wrote in message 
>>>> news:K8mdnbD64sHuVuLVnZ2dnUVZ8hmdnZ2d@posted.plusnet...
>>>>> dennis@home wrote:
>>>>>>
>>>>>> "Rod"  wrote in message 
>>>>>> news:6e9nr4F62mhgU1@mid.individual.net...
>>>>>>> dennis@home wrote:
>>>>>>>>
>>>>>>>> "Andy Hall" <andyh@hall.nospam> wrote in message 
>>>>>>>> news:487f9832@qaanaaq...
>>>>>>>>
>>>>>>>>
>>>>>>>>> Which is heavier?   A kilo of feathers or a kilo of lead?
>>>>>>>>>
>>>>>>>>>
>>>>>>>> Either depending on how they are stored.
>>>>>>> Unless you are playing at quirky things like one being stored on 
>>>>>>> the ISS and the other on the desk, the change in moisture content 
>>>>>>> of feathers, or similar unlikely ideas, I do not understand what 
>>>>>>> storage method has to do with it.
>>>>>> Well for one a kilo of feathers would be more buoyant than lead in 
>>>>>> most cases so it would weigh less.
>>>>>> For instance a kilo of hydrogen would weigh negative under normal 
>>>>>> conditions.
>>>>> the lead will also occupy a smaller volume and hence will likely 
>>>>> have a lower centre of gravity, so G (m1 m2 / d^2) will be larger, 
>>>>> making it heavier even without taking into account the buoyancy.
>>>> Not if the pile of feathers were the same height as the lead.
>>>>
>>>> They would still be more buoyant though.
>>> The word "likely" was used by John to indicate that this was not 
>>> certain.
>>>
>>> The buoyancy depends on shape. It would be possible in the fanastical 
>>> way you are treating this thread to imagine a model ship made of lead 
>>> that easily floated. And a super-dense package of feathers that at 
>>> the least only just floated.
>>>
>>
>> No. Ships float because they are made of metal (or wood, or concrete) 
>> *and* air. You cannot make a solid lead boat of any shape that floats 
>> due to buoyancy (a lead monolayer might float due to surface tension). 
>> Buoyancy at a water/air interface depends on shape. If the lead boat 
>> sunk it would still have a buoyancy (while sinking - granted less than 
>> its weight) independent of its shape.
>>
>> If we assume feathers are made of keratin, you are correct on the 
>> second point (as it happens), as the density of keratin is not far off 
>> that for water and, at their crush limit, they may either float or 
>> not. A feather will float but that has little to do with bouyancy but 
>> a lot to do with surface tension. A fully wetted feather, under water 
>> would be around zero buoyancy and might sink or float.
>>
>>
> well, you would hve to fill the quill first. ISTR they used to be used 
> to make fishing floats..

But they have already been crushed into a super-dense package. :-)

-- 
Rod

Hypothyroidism is a seriously debilitating condition with an insidious 
onset.
Although common it frequently goes undiagnosed.
<www.thyromind.info> <www.thyroiduk.org> <www.altsupportthyroid.org>

Rod wrote:
> John Rumm wrote:
>> dennis@home wrote:
>>>
>>>
>>> "Rod"  wrote in message 
>>> news:6e9nr4F62mhgU1@mid.individual.net...
>>>> dennis@home wrote:
>>>>>
>>>>>
>>>>> "Andy Hall" <andyh@hall.nospam> wrote in message 
>>>>> news:487f9832@qaanaaq...
>>>>>
>>>>>
>>>>>> Which is heavier?   A kilo of feathers or a kilo of lead?
>>>>>>
>>>>>>
>>>>>
>>>>> Either depending on how they are stored.
>>>>
>>>> Unless you are playing at quirky things like one being stored on the 
>>>> ISS and the other on the desk, the change in moisture content of 
>>>> feathers, or similar unlikely ideas, I do not understand what 
>>>> storage method has to do with it.
>>>
>>> Well for one a kilo of feathers would be more buoyant than lead in 
>>> most cases so it would weigh less.
>>> For instance a kilo of hydrogen would weigh negative under normal 
>>> conditions.
>>
>> the lead will also occupy a smaller volume and hence will likely have 
>> a lower centre of gravity, so G (m1 m2 / d^2) will be larger, making 
>> it heavier even without taking into account the buoyancy.
>>
> 
> Dennis,
> 
> Just bear in mind that this post has the context of objects on a shelf 
> in a room - not JPL.
> 
> So the shelf is going to have to be super strong to hold up a bath as 
> well? Well and truly classified in "unlikely ideas".
> 
> And in what way does the water affect the gravitional force acting on 
> the body? Sure, it might make it awkward to measure directly, but the 
> body still has the same force of gravity acting on it - merely has 
> buoyancy countering it.
> 
> John,
> 
> There is this weird idea in science that things must be measurable. I 
> suspect that in any real world way, the difference would be so small as 
> to be utterly unmeasurable. Certainly in the open air on an ordinary 
> shelf. However well fixed with resin or bolts. But theoretically there 
> might indeed be a difference if the items are re-formed into different 
> shapes.

Rod,

Don't get so excited, this was a frivolous response to Andy's comment 
"Which is heavier?   A kilo of feathers or a kilo of lead?" and 
absolutely nothing to do with shelves, just a meandering off topic for 
some light hearted amusement.

-- 
Cheers,

John.

/=================================================================\
|          Internode Ltd -  http://www.internode.co.uk            |
|-----------------------------------------------------------------|
|        John Rumm - john(at)internode(dot)co(dot)uk              |
\=================================================================/

John Rumm wrote:
> Rod wrote:
>> John Rumm wrote:
>>> dennis@home wrote:
>>>>
>>>>
>>>> "Rod"  wrote in message 
>>>> news:6e9nr4F62mhgU1@mid.individual.net...
>>>>> dennis@home wrote:
>>>>>>
>>>>>>
>>>>>> "Andy Hall" <andyh@hall.nospam> wrote in message 
>>>>>> news:487f9832@qaanaaq...
>>>>>>
>>>>>>
>>>>>>> Which is heavier?   A kilo of feathers or a kilo of lead?
>>>>>>>
>>>>>>>
>>>>>>
>>>>>> Either depending on how they are stored.
>>>>>
>>>>> Unless you are playing at quirky things like one being stored on 
>>>>> the ISS and the other on the desk, the change in moisture content 
>>>>> of feathers, or similar unlikely ideas, I do not understand what 
>>>>> storage method has to do with it.
>>>>
>>>> Well for one a kilo of feathers would be more buoyant than lead in 
>>>> most cases so it would weigh less.
>>>> For instance a kilo of hydrogen would weigh negative under normal 
>>>> conditions.
>>>
>>> the lead will also occupy a smaller volume and hence will likely have 
>>> a lower centre of gravity, so G (m1 m2 / d^2) will be larger, making 
>>> it heavier even without taking into account the buoyancy.
>>>
>>
>> Dennis,
>>
>> Just bear in mind that this post has the context of objects on a shelf 
>> in a room - not JPL.
>>
>> So the shelf is going to have to be super strong to hold up a bath as 
>> well? Well and truly classified in "unlikely ideas".
>>
>> And in what way does the water affect the gravitional force acting on 
>> the body? Sure, it might make it awkward to measure directly, but the 
>> body still has the same force of gravity acting on it - merely has 
>> buoyancy countering it.
>>
>> John,
>>
>> There is this weird idea in science that things must be measurable. I 
>> suspect that in any real world way, the difference would be so small 
>> as to be utterly unmeasurable. Certainly in the open air on an 
>> ordinary shelf. However well fixed with resin or bolts. But 
>> theoretically there might indeed be a difference if the items are 
>> re-formed into different shapes.
> 
> Rod,
> 
> Don't get so excited, this was a frivolous response to Andy's comment 
> "Which is heavier?   A kilo of feathers or a kilo of lead?" and 
> absolutely nothing to do with shelves, just a meandering off topic for 
> some light hearted amusement.
> 
John,

I should have put a smiley on your part. :-)

Dennis is doing what he often does.

-- 
Rod

Hypothyroidism is a seriously debilitating condition with an insidious 
onset.
Although common it frequently goes undiagnosed.
<www.thyromind.info> <www.thyroiduk.org> <www.altsupportthyroid.org>

meow2222@care2.com wrote:

> Fixings might be an issue, and the perfectionist's answer is surely
> resin fixings. But it should be ok with plugs & screws (use plenty
> of).
> 
> What will undoubtedly be an issue is shelf sag. It would take an
> exceptionally strong material not to sag with just end supports with a
> 42cm high 2' deep stack of books. You'll need to support these on all
> 4 sides, not just 3. 2x2 should do.

If you use something of decent thickness like 1" thick window board, and 
stick 2x1" battens on the wall right round the back and both sides you 
should be ok. If you want to use something thinner then you would need a 
lipping on the front.



-- 
Cheers,

John.

/=================================================================\
|          Internode Ltd -  http://www.internode.co.uk            |
|-----------------------------------------------------------------|
|        John Rumm - john(at)internode(dot)co(dot)uk              |
\=================================================================/

"Rod"  wrote in message 
news:6eaud4F65ij1U1@mid.individual.net...
> John Rumm wrote:
>> dennis@home wrote:
>>>
>>>
>>> "Rod"  wrote in message 
>>> news:6e9nr4F62mhgU1@mid.individual.net...
>>>> dennis@home wrote:
>>>>>
>>>>>
>>>>> "Andy Hall" <andyh@hall.nospam> wrote in message 
>>>>> news:487f9832@qaanaaq...
>>>>>
>>>>>
>>>>>> Which is heavier?   A kilo of feathers or a kilo of lead?
>>>>>>
>>>>>>
>>>>>
>>>>> Either depending on how they are stored.
>>>>
>>>> Unless you are playing at quirky things like one being stored on the 
>>>> ISS and the other on the desk, the change in moisture content of 
>>>> feathers, or similar unlikely ideas, I do not understand what storage 
>>>> method has to do with it.
>>>
>>> Well for one a kilo of feathers would be more buoyant than lead in most 
>>> cases so it would weigh less.
>>> For instance a kilo of hydrogen would weigh negative under normal 
>>> conditions.
>>
>> the lead will also occupy a smaller volume and hence will likely have a 
>> lower centre of gravity, so G (m1 m2 / d^2) will be larger, making it 
>> heavier even without taking into account the buoyancy.
>>
>
> Dennis,
>
> Just bear in mind that this post has the context of objects on a shelf in 
> a room - not JPL.
>
> So the shelf is going to have to be super strong to hold up a bath as 
> well? Well and truly classified in "unlikely ideas".

Where does the bath come in?

>
> And in what way does the water affect the gravitional force acting on the 
> body?

Where does the water come in?

> Sure, it might make it awkward to measure directly, but the body still has 
> the same force of gravity acting on it - merely has buoyancy countering 
> it.

Does it weigh the same though?

>
> John,
>
> There is this weird idea in science that things must be measurable. I 
> suspect that in any real world way, the difference would be so small as to 
> be utterly unmeasurable. Certainly in the open air on an ordinary shelf. 
> However well fixed with resin or bolts. But theoretically there might 
> indeed be a difference if the items are re-formed into different shapes.

You are getting things out of context.

>
> -- 
> Rod
>
> Hypothyroidism is a seriously debilitating condition with an insidious 
> onset.
> Although common it frequently goes undiagnosed.
> <www.thyromind.info> <www.thyroiduk.org> <www.altsupportthyroid.org>

"Rod"  wrote in message 
news:6eb0ipF66kceU1@mid.individual.net...
> dennis@home wrote:
>>
>>
>> "John Rumm"  wrote in message 
>> news:K8mdnbD64sHuVuLVnZ2dnUVZ8hmdnZ2d@posted.plusnet...
>>> dennis@home wrote:
>>>>
>>>>
>>>> "Rod"  wrote in message 
>>>> news:6e9nr4F62mhgU1@mid.individual.net...
>>>>> dennis@home wrote:
>>>>>>
>>>>>>
>>>>>> "Andy Hall" <andyh@hall.nospam> wrote in message 
>>>>>> news:487f9832@qaanaaq...
>>>>>>
>>>>>>
>>>>>>> Which is heavier?   A kilo of feathers or a kilo of lead?
>>>>>>>
>>>>>>>
>>>>>>
>>>>>> Either depending on how they are stored.
>>>>>
>>>>> Unless you are playing at quirky things like one being stored on the 
>>>>> ISS and the other on the desk, the change in moisture content of 
>>>>> feathers, or similar unlikely ideas, I do not understand what storage 
>>>>> method has to do with it.
>>>>
>>>> Well for one a kilo of feathers would be more buoyant than lead in most 
>>>> cases so it would weigh less.
>>>> For instance a kilo of hydrogen would weigh negative under normal 
>>>> conditions.
>>>
>>> the lead will also occupy a smaller volume and hence will likely have a 
>>> lower centre of gravity, so G (m1 m2 / d^2) will be larger, making it 
>>> heavier even without taking into account the buoyancy.
>>
>> Not if the pile of feathers were the same height as the lead.
>>
>> They would still be more buoyant though.
>
> The word "likely" was used by John to indicate that this was not certain.
>
> The buoyancy depends on shape. It would be possible in the fanastical way 
> you are treating this thread to imagine a model ship made of lead that 
> easily floated. And a super-dense package of feathers that at the least 
> only just floated.

I can't imagine any lead shape that will float in the air in a normal room, 
maybe you could describe it?

> Fixings might be an issue, and the perfectionist's answer is surely
> resin fixings. But it should be ok with plugs & screws (use plenty
> of).
> 
There is a difference between perfection and over specification.

dennis@home wrote:
> 
> 
> "Rod"  wrote in message 
> news:6eb0ipF66kceU1@mid.individual.net...
>> dennis@home wrote:
>>>
>>>
>>> "John Rumm"  wrote in message 
>>> news:K8mdnbD64sHuVuLVnZ2dnUVZ8hmdnZ2d@posted.plusnet...
>>>> dennis@home wrote:
>>>>>
>>>>>
>>>>> "Rod"  wrote in message 
>>>>> news:6e9nr4F62mhgU1@mid.individual.net...
>>>>>> dennis@home wrote:
>>>>>>>
>>>>>>>
>>>>>>> "Andy Hall" <andyh@hall.nospam> wrote in message 
>>>>>>> news:487f9832@qaanaaq...
>>>>>>>
>>>>>>>
>>>>>>>> Which is heavier?   A kilo of feathers or a kilo of lead?
>>>>>>>>
>>>>>>>>
>>>>>>>
>>>>>>> Either depending on how they are stored.
>>>>>>
>>>>>> Unless you are playing at quirky things like one being stored on 
>>>>>> the ISS and the other on the desk, the change in moisture content 
>>>>>> of feathers, or similar unlikely ideas, I do not understand what 
>>>>>> storage method has to do with it.
>>>>>
>>>>> Well for one a kilo of feathers would be more buoyant than lead in 
>>>>> most cases so it would weigh less.
>>>>> For instance a kilo of hydrogen would weigh negative under normal 
>>>>> conditions.
>>>>
>>>> the lead will also occupy a smaller volume and hence will likely 
>>>> have a lower centre of gravity, so G (m1 m2 / d^2) will be larger, 
>>>> making it heavier even without taking into account the buoyancy.
>>>
>>> Not if the pile of feathers were the same height as the lead.
>>>
>>> They would still be more buoyant though.
>>
>> The word "likely" was used by John to indicate that this was not certain.
>>
>> The buoyancy depends on shape. It would be possible in the fanastical 
>> way you are treating this thread to imagine a model ship made of lead 
>> that easily floated. And a super-dense package of feathers that at the 
>> least only just floated.
> 
> I can't imagine any lead shape that will float in the air in a normal 
> room, maybe you could describe it?
> 
> 
> 
In water.

-- 
Rod

Hypothyroidism is a seriously debilitating condition with an insidious 
onset.
Although common it frequently goes undiagnosed.
<www.thyromind.info> <www.thyroiduk.org> <www.altsupportthyroid.org>

dennis@home wrote:
> 
> 
> "Rod"  wrote in message 
> news:6eb0ipF66kceU1@mid.individual.net...
>> dennis@home wrote:
>>>
>>>
>>> "John Rumm"  wrote in message 
>>> news:K8mdnbD64sHuVuLVnZ2dnUVZ8hmdnZ2d@posted.plusnet...
>>>> dennis@home wrote:
>>>>>
>>>>>
>>>>> "Rod"  wrote in message 
>>>>> news:6e9nr4F62mhgU1@mid.individual.net...
>>>>>> dennis@home wrote:
>>>>>>>
>>>>>>>
>>>>>>> "Andy Hall" <andyh@hall.nospam> wrote in message 
>>>>>>> news:487f9832@qaanaaq...
>>>>>>>
>>>>>>>
>>>>>>>> Which is heavier?   A kilo of feathers or a kilo of lead?
>>>>>>>>
>>>>>>>>
>>>>>>>
>>>>>>> Either depending on how they are stored.
>>>>>>
>>>>>> Unless you are playing at quirky things like one being stored on 
>>>>>> the ISS and the other on the desk, the change in moisture content 
>>>>>> of feathers, or similar unlikely ideas, I do not understand what 
>>>>>> storage method has to do with it.
>>>>>
>>>>> Well for one a kilo of feathers would be more buoyant than lead in 
>>>>> most cases so it would weigh less.
>>>>> For instance a kilo of hydrogen would weigh negative under normal 
>>>>> conditions.
>>>>
>>>> the lead will also occupy a smaller volume and hence will likely 
>>>> have a lower centre of gravity, so G (m1 m2 / d^2) will be larger, 
>>>> making it heavier even without taking into account the buoyancy.
>>>
>>> Not if the pile of feathers were the same height as the lead.
>>>
>>> They would still be more buoyant though.
>>
>> The word "likely" was used by John to indicate that this was not certain.
>>
>> The buoyancy depends on shape. It would be possible in the fanastical 
>> way you are treating this thread to imagine a model ship made of lead 
>> that easily floated. And a super-dense package of feathers that at the 
>> least only just floated.
> 
> I can't imagine any lead shape that will float in the air in a normal 
> room, maybe you could describe it?
> 
> 
> 

The point of my original remark was that people *stack* plates in 
kitchen wall units without giving a thought to the fixings

"Rod"  wrote in message 
news:6eb7e7F69suqU2@mid.individual.net...


> Dennis is doing what he often does.

Its *you* that is trying to be serious.. the rest of us are having a bit of 
fun.
If you must be serious, please try and be sensible.

"Rod"  wrote in message 
news:6ebe15F69q54U1@mid.individual.net...
> dennis@home wrote:
>>
>>
>> "Rod"  wrote in message 
>> news:6eb0ipF66kceU1@mid.individual.net...
>>> dennis@home wrote:
>>>>
>>>>
>>>> "John Rumm"  wrote in message 
>>>> news:K8mdnbD64sHuVuLVnZ2dnUVZ8hmdnZ2d@posted.plusnet...
>>>>> dennis@home wrote:
>>>>>>
>>>>>>
>>>>>> "Rod"  wrote in message 
>>>>>> news:6e9nr4F62mhgU1@mid.individual.net...
>>>>>>> dennis@home wrote:
>>>>>>>>
>>>>>>>>
>>>>>>>> "Andy Hall" <andyh@hall.nospam> wrote in message 
>>>>>>>> news:487f9832@qaanaaq...
>>>>>>>>
>>>>>>>>
>>>>>>>>> Which is heavier?   A kilo of feathers or a kilo of lead?
>>>>>>>>>
>>>>>>>>>
>>>>>>>>
>>>>>>>> Either depending on how they are stored.
>>>>>>>
>>>>>>> Unless you are playing at quirky things like one being stored on the 
>>>>>>> ISS and the other on the desk, the change in moisture content of 
>>>>>>> feathers, or similar unlikely ideas, I do not understand what 
>>>>>>> storage method has to do with it.
>>>>>>
>>>>>> Well for one a kilo of feathers would be more buoyant than lead in 
>>>>>> most cases so it would weigh less.
>>>>>> For instance a kilo of hydrogen would weigh negative under normal 
>>>>>> conditions.
>>>>>
>>>>> the lead will also occupy a smaller volume and hence will likely have 
>>>>> a lower centre of gravity, so G (m1 m2 / d^2) will be larger, making 
>>>>> it heavier even without taking into account the buoyancy.
>>>>
>>>> Not if the pile of feathers were the same height as the lead.
>>>>
>>>> They would still be more buoyant though.
>>>
>>> The word "likely" was used by John to indicate that this was not 
>>> certain.
>>>
>>> The buoyancy depends on shape. It would be possible in the fanastical 
>>> way you are treating this thread to imagine a model ship made of lead 
>>> that easily floated. And a super-dense package of feathers that at the 
>>> least only just floated.
>>
>> I can't imagine any lead shape that will float in the air in a normal 
>> room, maybe you could describe it?
>>
>>
>>
> In water.

How are you going to get water to stay on the shelf?

dennis@home wrote:
> 
> 
> "Rod"  wrote in message 
> news:6ebe15F69q54U1@mid.individual.net...
>> dennis@home wrote:
>>>
>>>
>>> "Rod"  wrote in message 
>>> news:6eb0ipF66kceU1@mid.individual.net...
>>>> dennis@home wrote:
>>>>>
>>>>>
>>>>> "John Rumm"  wrote in message 
>>>>> news:K8mdnbD64sHuVuLVnZ2dnUVZ8hmdnZ2d@posted.plusnet...
>>>>>> dennis@home wrote:
>>>>>>>
>>>>>>>
>>>>>>> "Rod"  wrote in message 
>>>>>>> news:6e9nr4F62mhgU1@mid.individual.net...
>>>>>>>> dennis@home wrote:
>>>>>>>>>
>>>>>>>>>
>>>>>>>>> "Andy Hall" <andyh@hall.nospam> wrote in message 
>>>>>>>>> news:487f9832@qaanaaq...
>>>>>>>>>
>>>>>>>>>
>>>>>>>>>> Which is heavier?   A kilo of feathers or a kilo of lead?
>>>>>>>>>>
>>>>>>>>>>
>