View Full Version : Plywood Transom

Alan Peck
07-19-2001, 02:43 PM
The building plans call for two layers of 3/4 inch marine plywood, glued together to make the transom for my 15' runabout.

I know that epoxy is great stuff, but...
would it be good insurance to add screws on 8" centers just to be sure?

Is this overkill and could it possibly even have a detrimental effect?

I would appreciate any opinions.


Ian McColgin
07-19-2001, 03:03 PM
I'd not use screws as they are just a sourse of water intrusion. I'd glue up the blanks on a flat surface with maybe a little sand bag pressure to ensure even contact. Then cut and fit.


Mike in SC
07-19-2001, 03:05 PM
Alan- I can't see where a handful of screws will hurt, although 8" centers would mean more than a handful, I'd imagin. Just don't use so many, or screw so tightly that you squeeze the epoxy out. Look at it this way, if you were to have problems with the transome without the screws, you're probably gonna end up with problems eventually even with the screws. Then again, I've always liked the look of properly bunged screw holes in a varnished transome.

Wayne Jeffers
07-19-2001, 03:17 PM
I agree with Ian on this one; screws would serve mainly as a route for water to intrude.

Once the glue sets, the screws would be out of a job. Plywood is just glued up wood to begin with, right? I see no need for a belt-and-suspenders approach in this instance.


07-19-2001, 03:27 PM
What size outboard?

Done properly, screws will not hurt. That's the biggest stress point on the boat, with the outboard and all. Especially when out of the water.

If it was me, definitely screws and epoxy.


07-19-2001, 03:47 PM
Screws? Let's think about this a bit. How much stronger is the glue line between the plys of the ply wood than the epoxy glue line between the two layers of ply wood? Not much? None, I submit.

Who was the great philosopher who said, "I'd not use screws as they are just a sourse of water intrusion. I'd glue up the blanks on a flat surface with maybe a little sand bag pressure to ensure even contact. Then cut and fit." Such wisdom one should heed.

Anyway, when one puts in screws 1/3 should be in the top layer and 2/3 in the base. You wont be able to sinch downt the screws much. Maybe you should use carriage bolts. Not!

Lay one sheet down on a flat padded (old carpet) surface, coat both sheet with goop, goop bottom layer up with properly adulterated goop, lay on the other layer and pile on sand bags, first on in the center and build out slowly to let any entrapped air and excess goop escape. Buy a bunch if you have to. Winter's coming so you'll need the weight in your pickup anyway.

Worked for me.


Stephen Hutchins
07-19-2001, 04:42 PM
I vote no screws.

Alan D. Hyde
07-19-2001, 05:00 PM
How about no screws, but resorcinol and a gluing press?


G. Schollmeier
07-19-2001, 05:13 PM
If done right the 2 layers will become 1 layer of plywood. Would you add screws to other single layer plywood parts. You will gain nothing, but maybe trouble later.

Phil Young
07-19-2001, 06:08 PM
Personally I like screws in this application. The threads will tend to bite in the first sheet and the second, and actually hold them apart, allowing pockets of air here and there. Their heat expansion coeficcient will be different from the surrounding wood, so bunged, epoxied or whatever, cracks will develop, allowing some water to capillary deep into the wood, that's great, stops the wood drying out. Gets rid of all the air in the pockets eventually too. If you work it just right you can mix your metals a bit and do some great experiments with electron flow, and rates of decay of different metals and the woods they contact. Definitely the screws.

G. Schollmeier
07-19-2001, 06:36 PM

07-20-2001, 10:18 AM
Hi Alan,
I don't know if you ordered the back issues or not or if this helps you much but I just wanted to tell you that the guy that built the Downeaster (the larger version of our boat by the same architect) used screws in his transom at 6" centers. Although everyones comments above have convinced me to go without when it is time.

07-20-2001, 10:37 AM
No screws, epoxy proerly applied under controlled conditions.

Alan Peck
07-20-2001, 12:59 PM
Thanks for all the responses. It appears that the concensus is to use epoxy only, no screws, so that's the direction I will take.

Bill Berrisford
07-24-2001, 11:10 AM
Some of our boats have been on the water for over 25 years with laminated transoms clamped with screws from the inside without a problem.

bob goeckel
07-24-2001, 02:00 PM
how about a galvanized or fiber#%#** transom added to that wooden beauty!