|Pros spreading LPU(?) Glue in a DIYish Step|
(Photos from ProWall Factory)
|Finished SIP... Note Gluing Press in Background, Right|
I been thinkin'.
Ply/foam/ply composite construction has a LOT of advantages in boats. Foam insulates and floats, two valuable characteristics in WaterWorld. Separating skins of ply creates a girder very much more rigid, and stronger than the same two pieces bonded directly together.
So let's get some acronyms aboard:
- SIP (Structural Insulated Panel) - A pre-fabbed ply/foam/ply composite. Unfortunately, the more commonly available SIPs are made with nautically worthless OSB (Oriented Strand Board).
- XPS (Extruded PolyStyrene) - Available in boards of several useful dimensions from local building supply yards. Commonly referred to as blue- or pink board. It has high R-Value (insulates well), high structural strength (as foam goes), is completely water-proof, and stable (doesn't disintegrate into beads).
- AC plywood - Has one 'good' side (knots and gaps filled, sanded) and one not-so-good (holes not filled, usually sanded.
- DIY (Do It Yourself) - Mostly a great way to go. But I'm not the kind of guy who likes to knit, believing that machines do it faster AND cheaper.
For square boaters, especially, SIPs are an excellent way to shorten build time and dramatically improve insulation and positive buoyancy.
Square Boats of the Bolger Brick, Puddle Duck Racer, TriloBoat, Shantyboat and so on types stand to benefit most from SIP panels. Triloboats, for example, use 85% to 100% flat-panel construction. Time savings would be huge if building a whole boat from SIP, rather than DIY composites. But even Curvy Dogs use flat panels for bulkheads, sloped decks and superstructure construction.
SIPs can be DIYed. One can build them in place (generally the way to go whenever curves are present). Or one can pre-fab them, flat on the bench, before assembling them into the hull. In either case even clamping is the tricky part, to ensure good glue up and leave no voids. Vacuum bagging is ideal and within reach of amateurs, but requires a good set-up and tools you won't be taking with you.
Manufactured SIPs use high quality processes to ensure perfect adhesion. The downside is that they're mass producing for the housing market, which has different needs. XPS is more exotic, in this market, and the low end of the standard is 3 inches. The 'ply' used is most often OSB (Oriented Strand Board), a nautically worthless material.
The trick will be to come up with a standard or two, whose many customers make manufacture worth a company's while.
For starters, I'd suggest a SIP standard of 1.5 inch XPS sandwiched between two layers of 1/4 inch AC ply of a good, marine wood (red cedar, fir or equivalent, yellow pine).
1.5 inch foam provides reasonable thickness and allows framing with standard 2x lumber. If more thickness is required it can be laminated up without too much trouble, as 1/4 inch ply accepts staples for even, DIY clamping. AC plywood is much cheaper than marine, while SIPs' girder strength makes up for any structural advantages derived from engineered marine ply.
So, Square Boaters... do we represent enough of a market to start reaping economies of scale?