something other than wood that holds screws well

[pcg]

I want to imbed (in fiberglass) some stringers that run the length of the floor of my 22' Cruiser, to serve as a level mounting suface to screw down cabinets. Wood holds screws well, but I want somethign that won't rot. I've read here that the plastic lumber at Home Depot holds screws well, but is not very dimensionally stable with changes in temperature, compared to other materials. I'm concerned about that because the interior temp (storage and in use) can obvioulsly wary from near zero to over 100F.

Any other suggestions for a material that won't rot, is relatively dimensionally stable with temp swings, and holds screws well? Thank you!

[Foggy]

https://www.newjerseywindow.com/blog/why-a-fiberglass-door-is-better-for-security-than-wood/#:~:text=Wiggling%20or%20pulling%20at%20a,screw%2Dholding%20power%20of%20wood.

[ssobol]

[Tom Hruby]

Have you considered pressure treated wood? It is not pretty, but since you will be covering it with fiberglass, that should not be an issue. Another option might be to use square aluminum tubing ( https://www.onlinemetals.com/en/buy/aluminum-pipe ) and attach the cabinets with self tapping screws. In any case I would use epoxy rather than polyester resin with the glass because that will give you a better bond. As mentioned above, the plastics (pvc, hdpe, etc) have a very large coefficient of thermal expansion. That means that screws will tend to work in their holes, or the plastic will buckle and lift up your cabinets. Also none of the plastics will have a good bond with glass, epoxy, or polyester resin.

[Reelin2]

Personally, I think you are overthinking it. Done right, CDX or Marine ply, coated in epoxy will outlast you. If you are stuck on composite you could do coosa, but you will need to build up a glass layer to screw to or you could thru bolt some brackets. The only rot I’ve experienced on interior wood was due to negligence. A failed bilge system, leaking water tank or fill, leaking windows, seal, etc. that is left in disrepair for an extended period.

[ssobol]

You could try Trex decking (or equivalent). This is probably better and is weatherproof. The disadvantage is that it is relatively heavy and expensive compared to wood. I used it for a raised platform over the sump (even with the cockpit floor) in between the tanks on my 22. This is an area that frequently gets wet.

[thataway]

Why not just use fiberglass and epoxy resin to tab the wood into the existing glass? This also get rid of the problematic zinc plated steel "L" brackets. If for some crazy reason you need to remove the cabinet work later, just cut the tab.

Another option is to either use Weld Mount studs on the inner surface of the hull or "T" nuts embedded into fiberglass. You can also put an epoxy pot with an embedded wax or silicone coated threaded object the same thread as bolt or screw you plan to use. If you must encapsulate anything it would be Coosa board as noted by Reeling2.

The last item I would use is probably wood or wood substitute encapsulated in fiberglass. When all of those L brackets are screwed into the floor, they are not holding because of the balsa core, they are holding because of the fiberglass.

[Marco Flamingo]

I used Azek to make some simple cabinetry. It's PVC, screws and glues, floats, and is relatively inexpensive. In my photo album under Modifications-Cabinetry.

[Foggy]

Why make 'must do (gotta be the best)' modifications thinking 'long term' when
you will most likely either sell the boat (very common) in the shorter term or
your 'must do' modification(s) will out live you (x 2 - 3, almost assured)? Do you
have a grandchild that will benefit from your efforts?

Aye.
Grandpa used to say, "Keep it in perspective."