Transom Wood

[crosbyman]

Lumber yards should have it it came with a somewhat paper like beige colored layer on top (probably to help the paint to garb better) as I recall it was 60 inches wide by 8 feet. this goes back a while since I have had my new bass boats/75 ETEC 12 years now so we are talking 15-18 years ago when I did the transom on my previous rig with my totally amazing Classic 50 (loved that engine…trolled great, ran great..and drank twice the gas my ETEC drinks today 🙂 )

update: did some googling ….this must have been the stuff (it was marine plywood …for balconies)

The only kind of plywood you should use as decking material is marine plywood. There are several differences between marine plywood and normal plywood which make it the best choice for an alternative decking material. Marine plywood is seven to eight layers thick, and the epoxy used to bind the layers is waterproof. On top of that, the plywood itself is treated with waterproof sealer

Joining AOMCI has priviledges 🙂

[Pete]

Plywood glue specs are WBP(water and boil proof for marine and high quality exterior grades) and MR (moisture resistant usually for interior grades). High quality exterior (HQE) plywood like AB exterior grade uses the same glue as marine plywood. I have built boats with marine and HQE plywood with equal success and HQE costs less. There are ply thickness standards used, Ex: I have seen 5 ply 3/4" and 7 ply 3/4". When I was a PM engineer at a Marine Research facility in West Palm Beach, Fl in the 70’s we built numerous sea water use large and small tanks, flumes, large pump forbay sumps, transport tanks for long haul on land and air, etc. I specified AB Fir exterior plywood for these and to use 2 part epoxy and 3 coats of polyester resin. There never was a failure and they held up excellent for exterior and interior use with sea water. Fiberglass cloth was used in some areas where extra joint strength was needed. We used the plywood because it was quick to build and to modify as conditions arose and relatively inexpensive. Metals (SS, Monel, marine Aluminum) were also used in special cases along with the plywood. Then and now before using any plywood a WBP test was done on a small piece. The AB never failed the test.

Fir plywood will have some grain checking and needs good sealing to temper that, the polyester resin did a good job doing this in our outside applications. Overlay with fiberglass completely solves the checking.

For my race boats I use Okume plywood (3mm, 6mm, etc.) and AB exterior for transom boards laminated with Okume for a bright finish, clear coat with epoxy + fumed silica in epoxy for a structural thickener for bonding.

Lots of info here on glue and plywood:

http://www.christinedemerchant.com/mari … glues.html

http://www.christinedemerchant.com/mari … rades.html

[mini-motors]

On my Elgin Aluminum boat, I used a chunk of Douglas Fir 2X8(or 10?) on the outside. The 2" side was about 1/8" bigger than the roll of aluminum on the top. On the inside, I used a piece of 3/8" Okume. I work in a boat shop that has decent sized scraps of the BS1088 stuff. Both pieces were finished in polyurethane before installation.

[Author]

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