plywood species?

[matt167]

I'm building a small outboard powered cabin cruiser. Flat bottom, curved bow, very simple ( roughly a Lewis boat works chugger design) in a 60" beam x 16' variation. I'm trying to source 3/8" doug fir plywood that is ACX or better without having to order it in from a website or get something imported like Merenti or Okume, This boat will be fiberglass skinned, faired and either painted or gelcoated. Will be a trailer boat, so the exotic stuff would be a waste and the one supplier I found does not sell to the public.

One place has 3/8" sanded ACX SYP and it's $26/ sheet
They list/ have to order a 3/8" douglas Fir underlayment for $36. But if it's an MDO type underlayment it won't work

Will SYP work in boat building? I know it's slightly heavier

 

[Woodonglass]

Since you'll be glassing it yes. I'd recommend using two layers of 1908 Biaxial Fabric on both the outer and inner plywood for the bottom and sides of the hull. this will ensure good strength for any underwater obstructions you may encounter.

 

[matt167]

do you mean 1708? i can't seem to find anything on 1908?

I was thinking the same as you. 2 layers of 1708 inside and out.. Since I'm varying from the original plans and putting in a stringer system ( larger than design, bigger motor, forward controls ). should I bed/ tab the stringers into glass, or fasten them directly to the plywood and glass over everything that way?

 

[Woodonglass]

OOPS! I meant 1808 It's stronger and bulkier. Install stringers as described in link below. Bed them in PB and then Tab them in with 2 layers of the 1808.

 

[matt167]

Ok, so basically build the plywood out like a fiberglass boat? I read all your how too's years ago while attempting to restore the Custom Craft and had much of that done to it. Which is the whole reason this boat is getting done like this, as the Custom Craft was destroyed by a building collapse, I'm salvaging what I can of that boat to build a new one

 

[matt167]

well, turns out that the lumber yard didn't really know what the wood was. Talking to some plywood people, it's an interior/ exposure 1 grade plywood. Not a true exterior. The company also lists it as "A/C UL SYP" although they said it's exterior..

Another lumber yard can get AAX/ marine grade doug fir at $100 per sheet but that is same cost as the Meranti plywoods after shipping. I could use meranti for the bottom and a basic ACX or BCX for the sides