Mat'l to mount my AL tanks on?

[MikeT]

Geez, way to much time wasted this morning looking for what marinesurvey/Pascoe recomend. "Haysite or other fiber reinforced plastic".
Cut strips and 5200 to tank bottom. FRP's the stuff they make pc boards out of. $300 for a 1/4" 3'x4' piece! Uhm, anyone got any cheaper ideas for me?

Thanks,
Mike

[marshmat]

Good on you for reading Pascoe's article first, the guy knows the right (and the 200 wrong) ways of doing things.
When he refers to FRP, that's engineer-speak for fibreglass. Printed circuit board base, although it is indeed fibreglass, is not the stuff you want; you're looking for a cheap, bulk sheet material. You can get suitable material under any number of brand names. The key: it must be waterproof, rot-proof and non-metallic. No wood, no pressure treated wood, no "wood-derived engineered panels", and no crappy foams. Some stiff plastics might work, or you can always make fibreglass plate yourself using cheap polyester resin and cheap bulk mat. (Before the engineering staff hound me on that: yes, polyester and CSM is weak and brittle compared to cloth and epoxy- but we're talking about gas tank shims here, it's not like they'll see the kind of loading a hull does.)

[MikeT]

Thanks Marshmat,

Yeah, if Pascoes site had mentioned "FRP" and not that Haylite (fiber reinforced panel) I might have known what he was talking about. When I had guys asking me if I wanted G10 or FR4, that's when I was thinking pc board mat'l.
Anyways, the marina refered me to a plastics guy whose talked to a few guys in his business that know the tank shimming procedure. FRP from McMaster Car would run about $150, this guy's given me 4 cheaper options where I can get a 2x4 sheet of 1/4" mat'l for about $50.
1. Poly
2. Cloth based phenolic
3. Linen based phenolic
4. Canvas based phenolic (cheaper than the cloth or linen based)

Any opinions? Or should I dull up some tools and spend the money on FRP from McMaster?

Thanks,
Mike

[marshmat]

Not sure about the exact composition of any of those, Mike... but if (1) is solid polyethylene sheet, as I suspect, that should do fine. They make entire gas tanks out of the stuff, after all. "Cloth" or "canvas" can refer to a lot of different varieties of material, some of which might perform admirably, some of which might be vulnerable to deterioration when exposed to the bilge area of a boat.