Lwang

I was looking at ways to make float arms. I see plenty of DIYs here that has marine foam sheets glued together into squarish blocks, plumbing pipes tie-wrapped to the arm or pipe insulation/neoprene foams. I wanted to try the marine foam scheme, but getting my hands on those marine sheet foams seems a bit inconvenient (need large sheet, etc). I was thinking of using the polyurethane spray foam that they use for insulation since they are easily available.

I thought the easiest way is to cut the ends of an 1 liter soda bottle, keeping only the cylindrical section, spray the foam into it, then just drill a hole in the middle and insert it into my arm (I can cut the bottle after spraying the foam and letting it dry so there are less steps).

If I want to make it more fancy, I would get some 2 or 3 inch paper tube (or use the same soda bottle as above), grease the inside, spray the foam into it and slide the solid foam out when dry.

I can use bigger bottle for more buoyancy or small bottle for less.

Anyone tried this before? Will these compress in depth? They seem to be super stiff in the store.