Closed Cell Buoyancy Foam Test

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Reid
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Re: Closed Cell Buoyancy Foam Test

Post by Reid »

Well the results are in and, I must say, I am left with more questions than answers.
Here are the results:
Non Cut piece: Starting weight 24 grams, ending weight 74 grams (208% increase in weight)
Cut piece: Starting weight 20 grams, ending weight 64 grams (220% increase in weight)

So I must admit, I did not expect these results. However, there may be some variables that could have negatively impacted the results of this test.
1) As Jaysen pointed out (and I didn't agree with), the string that was attached to the screw may have given the water a pathway into the middle of the piece of foam.
2) The foam was mixed in a plastic mixing cup and then pulled out of the cup once it was cured. The bottoms of both foam samples were not as smooth as the tops. This could have been due to being pulled from the cup.
Could this have given the water a pathway to enter the foam as well?

To confirm the water intrusion I cut each piece in half. I blotted the inside with a paper towel and then squeezed one half in a vice. Both paper towels were wet and both pieces that were placed in the vice produced puddles of water.

I think this test might have to be re-run to eliminate the variables. Maybe leave the foam in the mixing cup and simply weigh it down by placing something on top of the foam. This would eliminate the string in the middle.

As with any scientific experiment these results will be open to your comments, scrutiny, and constructive criticism.

Here are the photos of the results:
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IMG_6828.jpg
IMG_6829.jpg


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piperdown
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Re: Closed Cell Buoyancy Foam Test

Post by piperdown »

I wonder if a full 7 day cure might make a difference.... :doh:
I agree that there had to be some capillary effect using string. Wonder if something like weedwacker line (nylon, assuming it wouldn't melt) might not be a better choice.
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Reid
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Re: Closed Cell Buoyancy Foam Test

Post by Reid »

piperdown wrote: Wed Dec 22, 2021 1:38 pm I wonder if a full 7 day cure might make a difference.... :doh:
I agree that there had to be some capillary effect using string. Wonder if something like weedwacker line (nylon, assuming it wouldn't melt) might not be a better choice.
It actually was a nylon string.
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OneWayTraffic
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Re: Closed Cell Buoyancy Foam Test

Post by OneWayTraffic »

I'm assuming that the foam was mixed in ideal conditions? I'm a little surprised that water was absorbed, but not shocked. There are multiple documented cases of water getting into foam, in for example old whalers. Google 'chainsaw whaler' for an interesting thread. On the other hand some identical boats never get water in the foam despite years of neglect. There is also this guy Ike on Hull truth and Boat design that used to work for the coast guard. He's a mine of information.

https://www.boatdesign.net/threads/hull ... ion.13679/

Seems to me that the upshot is that one should take great care in measuring and mixing two part foam. Temperature needs to be right. Best is to get block foam made in a factory and cut to shape. I can attest that the block foam I bought is higher quality than what I mixed myself despite the two using the same ingredients from the same supplier. Also important is that if a compartment has foam in it, it either be fully sealed or be kept ventilated.

silentneko
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Re: Closed Cell Buoyancy Foam Test

Post by silentneko »

I think the cure time might be the biggest issue here. Properly cured closed cell foam should not absorb moisture like a sponge. Water should only be able to penetrate the exposed cells, not wick its way through the structure.
I've done similar tests with an other 2lbs foam and great stuff from Home Depot. Neither absorbed much after a few days.
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Dan_Smullen
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Re: Closed Cell Buoyancy Foam Test

Post by Dan_Smullen »

Reid, Science and the Community thank you.

If you run the experiment again you could devise a way to determine if the foam will shed the water it absorbs. Seems like it would due to gravity alone. :doh:

fallguy1000
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Re: Closed Cell Buoyancy Foam Test

Post by fallguy1000 »

Reid..

Any good test needs a control.

What would a control be?

Something that should show zero change. For example, a piece of foam encapsulated in epoxy.

Also, I have an issue with the size of the sample. Despite it being a massive pain in the rear, I'd want to test a larger piece.

Surface area. The surface area is a factor; not simply the weight. The absorption is measured against area, no? So, if your cups are say 3" cylinders; the area is 42.4 square inches and the absorption is say 46 grams in 42.4 sqin. For a 7' wide boat by 16' long, themat is 16,128 sq inches which results in 17500 grams which is ?36 pounds of uptake for an entire boat surface one side (assumes other side is not accessible by water).

Consider my remarks conversational.

Oops. Remarkably more math errors..
Last edited by fallguy1000 on Wed Dec 22, 2021 6:36 pm, edited 1 time in total.
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fallguy1000
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Re: Closed Cell Buoyancy Foam Test

Post by fallguy1000 »

Of course, this is why the ink tests are done, because they want to know if it keeps going beyond the surface much...
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OrangeQuest
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Re: Closed Cell Buoyancy Foam Test

Post by OrangeQuest »

Thank you, Reid, for taking the time and using the resources to conduct this test.
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Re: Closed Cell Buoyancy Foam Test

Post by fallguy1000 »

See my math edits... ugh... I am having a bad day..
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