XPS Board Building Advantages vs EPS Foam

[blackeye]

I think XPS delams BECAUSE it's waterproof. <snip> Water vapor in an XPS board has nowhere to go. 

This would have to be water that is sealed in after a repair, or perhaps condensation from ambient moisture in original construction? Beasho's theory is that water intrusion will just find its way out the way it came in.

My very old very amateur very beat up paddle blade with XPS is sound. I used the coarse surface sanding method.

I'm wondering whether the resin/foam interface fails or is the failure foam/foam beneath the resin that causes the delamination experienced with XPS? I am aware of 80's boats that delaminated because the two skin layers ground down the core between them.

Also, there was discussion years ago about XPS and the mold release on its surface.

[lazymodo]

My experience with XPS has been that over time it expands and swells.
I used it for box inserts within 1lb and 2 lb eps and in all cases it swelled and raised abouve thoe original shape (EPS remained stable). My guess is that the blowing agent that normally escapes EPS when it heats is trapped within the closed cells and still expnds with heat but cant escape the closed cell structure.
Just my expeirence.

[juandesooka]

I am back in the shaping game after a long hiatus, for an XPS experiment.  I found a 4" thick slab, but it was 25lb density. So a little heavier than desired, but will be strong.  I am not super fussed about board weight, so that's ok.

My question for the hive mind is structure for the mast tracks.  In EPS boards, we started by cutting a hole right through, then pouring higher density foam (up to 20lb) to the deck, so that wouldn't compress under the tracks, makes a I-beam connecting bottom and deck of board.  Then various experiments with making pillars to connect them, to reduce the amount of hd foam needed, using hollow carbon tubes or other materials.

But with a 25lb density blank, seems to me this structure isn't needed...the blank has more compressive strength than the additions we were adding before.  Are you guys just doing a direct install of the tracks, no further structure below?   

[surfcowboy]

I'm back thinking too. You can't literally mean 25lb density though. That would make a board over 50 lbs. You mean 2.5?

For reference, the lowest density I've used is 6lb for boxes. I'd still grab some divinycel for "Dwight Boxes" if I were you.

Watching this for sure. I wanna make a high-5' to 6' wing board shaped like a mini DW'er next.

[juandesooka]

it's this stuff https://www.dupont.ca/content/dam/dupont/amer/us/en/performance-building-solutions/public/documents/en/styrofoam-brand-sm-xps-foam-insulation-pis-43-d100086-enca.pdf

Specs say "Compressive Strength(1), ASTM D1621, psi (kPa), min = 30(207)".  If I am reading that right...30 pounds per square inch density.  But I may be misunderstanding the measure. The blank doesn't seem excessively heavy. But sure needs a lot more elbow grease to cut it with a surform!

I am making an homage to the Omen Flux 60, as a quiver killer combo wing prone board.  Thinking it'll be called "Ol'Man Sux" though.

[Hdip]

Add in some of the new KT design too and call it the Special K.

[clay]

it's this stuff https://www.dupont.ca/content/dam/dupont/amer/us/en/performance-building-solutions/public/documents/en/styrofoam-brand-sm-xps-foam-insulation-pis-43-d100086-enca.pdf

Specs say "Compressive Strength(1), ASTM D1621, psi (kPa), min = 30(207)".  If I am reading that right...30 pounds per square inch density.  But I may be misunderstanding the measure. The blank doesn't seem excessively heavy. But sure needs a lot more elbow grease to cut it with a surform!

I am making an homage to the Omen Flux 60, as a quiver killer combo wing prone board.  Thinking it'll be called "Ol'Man Sux" though.

Compressive strength means one could put a 30 pound weight and it won't crush.  Look up the pink panther stuff at home depot I think they have the psi on there and you can get an idea of density.  There might be some correlative formula, maybe Denton knows it...