GB Woodie Transom

[Marinex]

We are just redoing our wooden transom for the second time. Originally in varnish but then we had it stripped and it was cetol the second time. In both cases we have had issues with the seams between planks cracking open and water intrusion causing discoloration. Has anyone found a solution for this, we kind of wondered if we used CPES thin epoxy if that would help?


The pictures tell the story of the issue, thanks!

 

[MYTraveler]

After preparing surface well, a few coats of epoxy (the first being very dilute to allow deep penetration), followed by varnish, which is necessary to protect the epoxy from UV damage / deterioration. At least that's how my last boat, which had a lot of bright work (current boat has none) was maintained.

 

[RT Firefly]

Greetings,
Mr. M. Wood is constantly expanding and contracting due to heating (sun)/ cooling, wetting (spray/rain)/drying. IMO, whatever you put on carvel (edge to edge) planked seams will crack eventually. The best solution and you may not like the appearance is router out the seam, fill it with resilient caulking and varnish over. MY $.02 (CF).

 

[Cigatoo]

Is the water getting in from the top of transom / deck seam area and working its way down? I’ve seen that occur in the fiberglass boats. Just a thought.

 

[MYTraveler]

Finish cracking may be inevitable (although, if I recall correctly, my maintenance guys used a pliable, or at least not brittle, epoxy -- the same stuff used to coat the threads holding down the guides on fishing rods, which would otherwise crack when the rod is loaded up) , but if the goal is to prevent black staining, which is typically caused by mold, proper preparation followed by saturation of dilute epoxy should encapsulate the wood sufficiently to prevent water intrusion and mold grown on the wood itself.

 

[Marinex]

Thanks for all the help so far, we are going to fashion a cover for it this fall as well

 

[Comodave]

Thanks for all the help so far, we are going to fashion a cover for it this fall as well

That is a goodidea. Keep the sun and water off it. I like Stamoid for that since it is truly waterproof.

 

[Lepke]

I've did a lot of varnish work when I was younger. After the stain, if any, I used 2+ coats of a clear drying epoxy, West w/special clear hardener. Then a few coats of a varnish with good UV blockers.
As Groucho says, the wood shrinking and swelling will open the seams. If the seams are too tight you'll have to open them up to run a proper seam sealer. The easy way is with a thin saw blade. Then I epoxy including the wood in the seams so a slight leak won't swell the wood. After that a good seam sealer that has the ability to expand and contract.
Before the varnish, I also coat the seam sealer. With the wood sealed the wood changing size is minimal. If you have the wood off, seal the back side. It doesn't need varnish where the sun doesn't shine.
Say the secret word and win $100.

 

[fgarriso]

I am happy I don't have a wooden transom anymore.

 

[Keijo]

Has anyone tried taking down to bare wood, light weight F/G cloth with clear epoxy plus UV varnish over top?

 

[rgano]

Has anyone tried taking down to bare wood, light weight F/G cloth with clear epoxy plus UV varnish over top?

One my GB 42 woodie, I always applied CPES in two coats whenever the wood was bared. Then Epifanes. I don't recall ever having the seam splitting issue in my transom, but it normally was covered with a Sunbrella cover if not underway. In you case I'd get it all cleaned up to bare wood ensuring the problem seams are opened up and then saturate the area with CPES to ward off the moisture which gets in there. I did not feel the necessity to widen the seam to put an elastic caulk in there, but if the problem persists after the above recommended treatment with CPES and a sun cover, you might consider the idea.

 

[Keijo]

I have tried that method - with 3 coats of CPES and up to 10 coats of Bristol. Eventually the cracks appears and water intrusion follows. Perhaps Epifanes is more pliable than Bristol and will ‘give and take’ with heat expansion. My thinking is that F/G cloth might prevent any such movement.

 

[RT Firefly]

Greetings,
Mr. K. F/G will eventually crack as well. Tried that on a cedar strip canoe. The wood is stronger than the F/G/

Now there's a larger problem in that you will have to remove the F/G to repair.

 

[Keijo]

Thanks for that.

 

[Comodave]

I don’t think I would fiberglass it either. On the one hand it may work great but on the other hand if it fails you have a tremendous mess to deal with. I am so happy that our current boat has absolutely no exterior wood…

 

[jjorgenson3]

Woodie Transom

I’ve used this product for 12 years. It works great for me.

 

[Keijo]

Thanks, I'll look into that.

 

[DutchProf]

Fiberglass epixy

Have used fiberglass w West system epoxy on two boats built. One a cosine Wherry which is closest to what you query.
First: make sure the wood is clean (bare), and fill any large defects. Then let it dry! After finish sanding and careful vacuuming, lay out your fiberglass and ( tricky part) try to keep it as flat and tight on the wood as possible.
Second: Buy, or make a roller ( I’ve made several out of heavy metal wire with metal washers ( alternating large and medium) , and have it ready when you wet the glass. Then roll carefully to not trap air pockets ( which you will), and when you do, go back to that area ( means you lift the glass beyond the defect off and start over) rolling in single direction and care to get a feel for applying just the right amount of epoxy to ensure the mat is completely wetted will take some time, but you’ll get there.
3: Sand to at least 120, ( I prefer 220) then Varnish with your preferred UV varnish ( I like z-spar), and you will have a very long lasting result. After more than 30 years on that edge planked Wherry not a single problem arose.
The look of varnished wood, but not the upkeep. I revarnish every few years depending on use, but the system described has worked like a charm for me. Hope this may be of some help. Good luck!

 

[DutchProf]

Gap repair

Afterthought: if you sand the surface and collect the sawdust, you can make a sawdust/epoxy ‘putty’ for repair of any larger defects.
If color is critical, you can even add pigments to the putty to try for a better color match ( tricky, and a pain if you get it wrong as you have to remove it), but after making a few practice mixes you can often get quite close.

 

[DennisB1]

I would vanish the transom with epiphanies and then cover the transom with a sunbrella in a light color and remove the cover when using the boat.

Trouble with covering one side of the wood transom with a fiberglass would be expansion and warpage unless the inside also has the same covering process. I have made glue up table for boats covering both sides with equal number of varnish coats on each side. Goal is to have uniform expansion on both sides of the wood. The coatings also slow the absorption of moisture, so the wood is more stable.
If you measure the surface temperature with a IR gun you will notice that the wood gets quite warm. I did that measurement a few days ago (PNW Seattle Latitude) and got a surface temp of 130F in the late afternoon. So a light-colored cover would keep the surface cool and minimize your cracking.

 

[Circumnavigator]

Two posters have suggested "dilute" epoxy -- West Systems says to never dilute its product and I agree. I would use two or three coats of West System on very dry bare wood and then several coats of standard -- not urethane -- varnish with a sun block. Urethane varnish is great for inside where it resists denting, but sanding it is a bear.


Glass cloth over wood is rarely a good idea. A cloth cover is a great idea.


Jim

 

[mickand]

From the photo, it looks like plain butt joints, not the tongue/groove GB type.
I agree that the 'cure' is to rout out the joints - 1/8" wide/depth - 'finish' the planks, tape up and apply Teak Decking Systems black caulk. You've now effectively 'finished' the planks as 'individuals' and the caulk will take up the normal future expansion/contraction of the wood, without 'cracking' the varnish.

 

[Brent S]

I have had great success with routering a small groove in the seams, then glueing in a teak batten into the grooves. Followed by 12 coats of varnish .No movement of the seam after 20years.Had to wood out the transom twice in that time and reapply the varnish.
Good luck.

 

[jgwinks]

Most of the problem is due to what ever finish you put on is spanning the seams between the planks. When the wood moves due to expansion and contraction the finish cracks. In new construction using epoxy each plank would be coated all the way around before installing it and bonded to is neighbors. No spanning of the seams, no cracking. Short of replanking the best you can do is route out the seams and coat/fill with epoxy. Strip, dry, and coat the inside too if you can get to it well enough.