Physics and buoyancy question

[Basel A]

Originally Posted by Ether

Most pool noodles are made from closed-cell foam, are they not?

I didn't mean within the cells themselves, but rather the long-ways cylindrical hole through the noodle. It doesn't increase the weight, but it does decrease the volume. Sorry, should have clarified.

Edit: Or rather keep the total volume but include the weight of the water inside. The former works better, I think, but I originally referring to the latter.

[JamesCH95]

Originally Posted by Ether

I believe he meant that the boat weighs 8 pounds in air. It would weigh noticeably less when submerged in water.

Good point.

[Rangel]

You might also want to use syntactic foam instead of pool noodles. Pool noodles absorb a lot of water drastically changing its buoyancy.

[PAR_WIG1350]

Originally Posted by Rangel(kf7fdb)

You might also want to use syntactic foam instead of pool noodles. Pool noodles absorb a lot of water drastically changing its buoyancy.

Only on the surface would absorb water and only if the cells are punctured. A new, undamaged, smooth surfaced pool noodle should not absorb much water at all, if any.

[Tem1514 Mentor]

Sorry guys, I became rather side tracked on a number of other items.

After a number of floatation tests with pool noodles and the blue insulation foam I found that the pool noodle will allow water to permeate into its’ cell structure after time (hours that is), where as the blue foam does not.

Using just simple floatation test using lead to represent the weight of the boat I was able to determine how much foam would be required to float 8 lbs. Then after some creative forming and cutting of the foam, was able to fit just enough foam in the un-used spaces of hull so in the event of flooding the model will stay afloat.

So many thanks to everyone for the input as it was greatly appreciated.