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darryl
07-20-2012, 09:55 PM
Pretty obviously OT :) I have an idea to use a layer of ping pong balls arranged in one layer and all touching, then fill the gaps with insulating foam, then skinning it over with fiberglass on both sides. It would form a panel which would be strong, yet light, and have some insulative value. I'm wondering which part would insulate best, the spray-can foam or the balls. Being hollow and air-filled, there might be an air current set up inside in response to temperature differentials from one side to the other. If that happens, the ball would be a poor insulator. If perchance that wouldn't happen, then it would be a good insulator, and the foam would go three times as far. Ping pong balls are about 1-1/2 inches in diameter, and as smooth on the inside as they are on the outside.

It has occurred to me that you could lay a lot of them on glass and glue them to each other- that would give a flat base for the rest of the panel to be formed onto. Or- you could arrange them to make a shaped panel, or a corner.

For practical purposes this may all be quite insane- or it may have some value in some way. It's just an idea that came to me while looking through a dollar store and seeing boxes of ping pong balls cheap.

RussZHC
07-20-2012, 10:07 PM
The first thing I wonder is if a given temperature change or quickness of change would collapse the ping pong balls?

Not that it would matter if all of the gaps were filled with insulating foam or that you could do anything about it anyway but what about if that happened to a number of them in terms of structural integrity?
I'm envisioning large insulating panels that if a line of balls caved in could kink the panel...

lowcountrycamo
07-20-2012, 10:11 PM
Air is a great insulator, especially insulated air. ;) I don't know which would have the greater R value but it's my experience that "insulation" and air pockets work best together as you are doing. And I think it's a good idea as long as the balls are real cheap.

sasquatch
07-20-2012, 10:47 PM
Darryl , do you have an application in mind for this??

Evan
07-20-2012, 11:00 PM
Sounds like a lot of extra time and trouble when you could just use sheet styrofoam. Small air bubbles are better than big air bubbles because of convection cells in large bubbles. Ping pong balls are just big enough for convection cells using dry air. Dry air can form convection cells down to a sphere of about 3/4" diameter. Below that convection stops operating and only conduction and radiation play a part.

Jim Hubbell
07-20-2012, 11:25 PM
Float a bunch on your heated swim pool to help contain the warmth. Might make an interesting swim if left in place. Might foul up the skimmer tho. Oh well.

bob ward
07-21-2012, 12:25 AM
If all you want to end up with is a lightweight insulating panel with a fibreglass skin on each side, while your pingpong balls and sprayfoam idea will work, it will be a lot easier to obtain a slab of foam, either EPS or rigid PUR and fibreglass that, be careful with you choice of resins though. Polyester resins (cheapish) will dissolve EPS foams but are AOK with PUR. Epoxy resins (dearer) will be OK with either type of foam.

Evan
07-21-2012, 01:07 AM
A layer of aluminum foil anywhere in an insulating layer adds R3 to the insulator.

darryl
07-21-2012, 01:25 AM
First off, I don't think the balls will even feel a change in air pressure, up or down, since the round shape would support either without difficulty. If you physically crushed an area- well there would be support from the foam, plus the fiberglass skin.

The balls are cheap, otherwise the cost per sq ft of panel would be too high. As it is it would be about $2/sq ft for the balls. Contrast that with a foam that won't dissolve with polyester resin, and the balls come out a lot less expensive, even when you add in the cost of spray foam. Polyester resin compatible foam is not cheap by a long shot, whether bought by the board or in a can. EPS or styrofoam is a lot cheaper, but then you contrast that with the extra cost of epoxy resin- then you consider the fact that epoxy isn't designed to 'soften up' fiberglass matte, so you want to stay with polyester resin-

It was just an idea. Evan, I think you're right on the mark with the comment about the maximum size of cell that would be useful- the balls are too large to prevent convection.

I don't have a particular application in mind, though it's not hard to see that a light and rigid panel would have advantages, including having some insulative value. A body for a one-man electric runabout, perhaps- maybe the bottom part of a canoe could be built this way-

beanbag
07-21-2012, 01:58 AM
ummm, excuse me? But regulation ping pong balls are now 40mm diameter. I just felt like correcting somebody on the internet.

darryl
07-21-2012, 02:34 AM
ummm, excuse me? But regulation ping pong balls are now 40mm diameter. I just felt like correcting somebody on the internet.

Dang! No wonder these balls are cheap- out of spec! :)

J Tiers
07-21-2012, 10:13 AM
My suspicion is that better R-value insulation could be obtained in a somewhat thinner panel without the ping-pong balls. Overall cost is likely to be lower as well, since there is no need to "herd" the balls and carefully spread out the expanding foam between them.

If you want a better material, still using a "wasted resource", you could do about the same thing with discarded "packing peanuts". It would be a good form of recycling.


ummm, excuse me? But regulation ping pong balls are now 40mm diameter. I just felt like correcting somebody on the internet.

1.5" is 38.1 mm 40 mm is 1.57"...... still "about" 1.5"

Perhaps a difference without a distinction?

beanbag
07-21-2012, 05:52 PM
1.5" is 38.1 mm 40 mm is 1.57"...... still "about" 1.5"

Perhaps a difference without a distinction?

Well, back when regulation balls were 38mm, I wouldn't have bothered correcting somebody over the .1 mm, but now their error is a whole 2mm!

If you've trained all your life on the 38mm ball, and somebody suddenly gave you a 40mm ball, it would feel like swatting a beach ball around.

SteveF
07-21-2012, 06:27 PM
The balls are cheap, otherwise the cost per sq ft of panel would be too high. As it is it would be about $2/sq ft for the balls.

I don't have a particular application in mind, though it's not hard to see that a light and rigid panel would have advantages, including having some insulative value. A body for a one-man electric runabout, perhaps- maybe the bottom part of a canoe could be built this way-

I'm confused. Laid out perfectly you are looking at about 60 x 30 or 1800 ping pong balls. At a regulation weight of 2.7 grams each that's about 10.7 lbs. Not counting the weight of the foam or fiberglass matrix. The cost of the ping pong balls alone is $2 / sq ft. Not counting the spray foam, fiberglass, resin or ungodly amount of labor involved.

A sheet of 2" XPS foam is under $1 / sq ft and weighs about 8 lbs. It's a little heavier if you want the higher density sheets that will support up to 100 PSI (continuous rating is less).

There must be a reason why no one makes insulation boards out of ping pong balls but I can't think of what the reason might be. :confused:

Steve

darryl
07-21-2012, 08:20 PM
I was just in a building supply store this AM. 2 inch xps is $37 for a 2ftx8ft piece. That's about on par with the balls, so why would I go the labor intensive route instead of using already formed sheet- there is no good reason I can think of at the moment.

In fact I can't think of any other use for ping pong balls except as- ping pong balls.

Evan
07-21-2012, 08:56 PM
There is an very important alternate use for ping pong balls. It is a parts of the toilet flush test to determine flushing power, especially with low flush toilets.

JoeLee
07-21-2012, 10:12 PM
I think you would be far better off if you used honey comb sheeting in place of the ping pong balls. The small air pockets would have a better insulating value and much stronger than the balls. Thinner also. Strong enough to walk on.

JL.................

Bill736
07-21-2012, 10:43 PM
The use of ping pong balls as part of an insulation board might have merit if you need insulation that will not become water logged , or perhaps as part of something that will float. In any case, I recently bought a package of ping pong balls at the grocery store . They simply looked like something that I might use in the future for some project. When I got home, I added them to the three packages I had already bought, but forgot about. I will say, however, that fairly often I do " impulse buy" various small items and materials , and most of the time I find I have a use for them within , say, 2 years ( if I can still locate them). It's sort of a sixth sense that a lot of us on this forum probably have.

Mike Burch
07-22-2012, 06:46 AM
Careful, Evan, you'll start a new diet fad...

wtrueman
07-23-2012, 02:34 AM
Where this idea might be good is in using several layers, bonded with the spray foam insulation, as salt water marine float because the teredos (sp?), or Bankies (also sp?) could not penetrate them. Cost, however, would depend on the life cycle of a regular ping pong and of course, the initial cost of many pings. Wayne on the west coast.

vincemulhollon
07-23-2012, 09:02 AM
The balls are cheap, otherwise the cost per sq ft of panel would be too high. As it is it would be about $2/sq ft for the balls.

Mostly posting this to try out the new forum, haven't played ping pong in a couple presidents, I think since Bush the First. I did get an egg-bot printer and accidentally wasted the money on tournament grade ping pong balls for testing before I used the machine to make my glass christmas gift ornaments. Anyway there's tournament grade balls at around one dollar per ball, and there's "practice" balls that are like $9 for a bucket of 144. However there is some difference in durability and strength. Even as a guy just fooling around I could tell the difference between "real" ppballs and "practice" ppballs. So spec out BOTH your material strength and price using the same material, or you could be in for an unpleasant surprise. Kind of like spec'ing out a project using aerospace certified angle stock but using bed-frame-ium whatever that stuff is. What is bed-frame-ium metal anyway? It doesn't weld, machine, or bend very well, although it does take paint and rust pretty well.

(FYI an egg bot printer is a kit that is vaguely like a vertical mill set up for gear cutting with a rotab... However its made entirely out of fiberglass and wood and while precise enough to decorate round things is not nearly strong enough to actually cut anything (although it can engrave...). The "mill spindle" so to speak is a arm on a flapper hinge with a bic ultra-fine point pen instead of a cutting spindle. Hooked up to an infinitely patient and detail oriented computer it can make VERY nicely custom decorated christmas gift ornaments. "Someone" should write an article for digital machinist about doing this task with a 4-axis CNC mill)

rowbare
07-23-2012, 11:23 AM
Hold a match to a ping pong ball then see if you want your insulating panel to have that kind of behaviour.

bob