How to protect transom plywood?

This topic has 13 replies, 9 voices, and was last updated 7 years, 6 months ago by amuller.

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October 12, 2016 at 11:44 pm #5482
amuller
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This might be a little off-topic, but I’m replacing the plywood on the transom of my little tin boat. Am wondering about the best way to protect it. Soak with resin? Just paint? Linseed oil?
October 13, 2016 at 1:27 am #45724
david-bartlett
Participant
What I do is first sand it good, then apply a couple coats of epoxy resin, then sand lightly and polyurethane or varnish over the epoxy. Drill all your fastener holes before applying epoxy and varnish.
October 13, 2016 at 1:45 am #45728
mr-asa
Participant
Not sure why you’d apply varnish over epoxy?
October 13, 2016 at 2:41 am #45733
david-bartlett
Participant
quote Mr. Asa:

Not sure why you’d apply varnish over epoxy?

Most epoxy is not UV stable and will break down much faster if unprotected by the varnish.
October 13, 2016 at 3:29 am #45735
mr-asa
Participant
So do you apply a new coat of varnish every year? The UV protection in it breaks down over time and exposure to UV.
October 13, 2016 at 10:35 am #45749
chris-p
Participant
Good advice from David above. Some guys keep up on their transoms, im a little lazy and let it go for a while!
October 13, 2016 at 11:01 am #45753
sydinnj
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US Member - 2 Years
If the boat is stored inside it lasts a long time, outside then it needs to be done more often. My Fay Bow outboard from 1931 looks like the day I put it on around 25 years ago. It is stored inside and I used Pettits ultra V Gold. It is a polyurethane. My Hacker Craft which spends much more time in the sun lasted 13 years before I redid the finish.
October 13, 2016 at 12:06 pm #45757
george-emmanuel
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US Member - 1 Year (includes $3 online payment fee)
My 2 cents: When installing any wood in a boat use a marine grade. There are all types of "marine" plywood. Marine fir is probably the most common but it isn’t what it used to be! So I treat all plywood with Smith’s Clear Penetrating Epoxy nicknamed CPES. It soaks into the wood deep. Thoroughly saturate the outside edges of the plywood, let it cure and then use your finish. I prefer Sapele but at about $100/sheet it scares people.

If you encapsulate your transom you are asking for trouble. Water can enter from the slightest crack/hole and can’t get out. At that point rot begins and goes wild. My personal preference is to treat with CPES then varnish. I don’t use polyurethanes when cosmetic appearance is important because they are more difficult to deal with later on.
October 13, 2016 at 1:21 pm #45763
wiscoboater
Participant
Most of the CPES available can be cut 50% with Acetone to thin it to a water like state. Using that as your first coat, followed by an uncut second coat will dramatically increase the level of penetration into the wood. Doing it in that way will outlive us all. See a demonstration of this method at the Jamestown distributors web site. They sell top of the line boat restoration supplies.
October 13, 2016 at 1:33 pm #45764
amuller
Participant
Thanks for all the input. Lots of opinions on this, and no perfect answers. I favor penetrating materials over an impermeable surface coating, because the barrier will likely be imperfect and saturation will result. There is not a huge amount at stake with the plywood pads on a tin boat, but an encapsulated plywood transom on a chopper-gun fiberglass hull is a whole different story…..
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