(sigh)-wet rot in the gunwhales-advice please....

[yourmomm]

hi-
after many hours painful preparation i was just getting ready to feel satisfied and ready for the painting when i started prepping the gunwhales as the final job....

they are made of (what looks like) mahogany ply and have been externally sheathed in epoxy and glass fibre by the look of it-the epoxy has delaminated with the paint layer intact (hadnt noticed til i got up close with a sander)-a little dig with a knife and-sure enough-the mahogany underneath is rotten to the core. i am in the process of digging all this rot out but wonder how best to repair it?

putting in new ply im sure will be fairly simple, but to sheath it in epoxy seems ineffective in stopping the rot....do forumites have any suggestions to weatherproof this vulnerable area...? many thanks

 

[graham]

need a bit more info to offer any usefull advice. What type of boat is it? What is the hull material that the rotten bits are attatched to?

You correctly identified one thing.Coating wood in epoxy or grp will only work if it is completely sealed.One crack or hole in the coating will trap moisture in and accellerate the decaying process.

If the gunwhales are in fact external rubbing strips I would recommend stripping them off completely and replacing with hardwood ones .these should be oiled painted or varnished but not epoxied or glassed as they take all the knocks and inevitably moisture will get in behind.

After the depressing bit ripping off the old ones it will be a satisfying job fitting the new ones.

 

[yourmomm]

thanks graham-the boat is a one-off curtis and pape iroko-on-oak cutter headed ketch (9.8m on survey but a whopping 12.6m thanks to bowsprit and bumpkin). the rubbing strakes are made of mahogany (without epoxy sheathing-just varnished) and are completely intact-no rot at all(weirdly enough)-wherever the water ingressed-it was not through these!!! the top edge of the gunwhale terminates in one such intact rubbing strake, and there is another strake on the outer side of the boat approximately 7 inches below this at deck level. this produces a raised gunwhale all around the boat. it is the external section of this raised gunwhale with the rot-between the lower and upper strakes-the strakes themselves are fine, so do not need removing. i am hoping simply to chisel a section under and behind the lower strake, and simply cut the new mahogany ply so it fits in this section and then flush with the upper strake. many thanks for any further advice.

 

[graham]

Its a bigger boat than I imagined.I would get some advice from someone local who can actually look at the problem.

If she were mine I woul;d remove all the wet plywood and replace not with plywood but with Iroko .Iroko is much more durable and rot resistant than almost any other wood.

If you cant bend it in one piece you could consider laminating it in position out of several thin strips using epoxy glue or other suitable marine glue. Iroko is sometimes oily so may neeed degreasing prior to glueing.Also the sawdust from it is not healthy to breathe so get a decent mask.

Good Luck with the repairs.

 

[pcatterall]

So removing the upper and lower rubbuing strakes, fitting a new epoxied gunwhale section and replacing the rubbing strakes is not an option?
Trying to fit in a section between the strakes sounds potentially difficult, dont the rubbing strakes fasten through the gunwhale?
Perhaps you could post a sketch of a typical section?
good luck (youve got the whole winter to sort it!!)

 

[Sixpence]

Had a similar problem on my 21ft Debutante where someone had added the epoxy after the build and it hadn't sealed properly onto the wood , my solution may not be perfect and some may say the opposite but the best way I think is to remove absolutely all wet , or damp wood , then when you've cut well into good stuff start on the repair , but do not epoxy , if anything goes wrong and you don't get an absolutely perfect seal , the water will find it , and the first thing you'll know about it is when you're replacing the rotten wood again
Wooden boats lasted well enough before the invention of plastic , they just need looking after a bit more

 

[Poignard]

[ QUOTE ]
Coating wood in epoxy or grp will only work if it is completely sealed.One crack or hole in the coating will trap moisture in and accellerate the decaying process.


[/ QUOTE ]

Absolutely agree. If you can't be sure of a perfect coating, onto dry wood, you're better off without it

 

[yourmomm]

many thanks for the helpful replies-but my problem is this-i do not intend to epoxy the new ply i am putting-in but i i'll be jiggered if im going round the whole boat removing the sound (albeit epoxied) timber on MOST of the gunwhale....so....if im scarphing new (non-epoxied) ply around old (epoxied) ply-what precautions do i need to take...? many thanks again.

 

[tillergirl]

It sounds like you have an identical job to one I did about 10 years ago on Tiller Girl. If I read this right your gunwale extends below deck level. If that is the case and that is made out of plywood, I would immediately suspect a previously botched repair where someone hasn't been able to afford the right timber. It is hard to imagine the builder using ply for this application. I am afraid I cannot see the point of sheathing ply in this application; it just causes trouble. Water is bound to get into the laminates underneath the capping and then is trapped in there. I would also regard the deck/gunwale seam with some suspicion. If this is leaking then there is danger of damage to the deck, beam shelf and beams/half beams, perhaps even the top of the frames. I'm afraid I've been there.

I think this is no place for ply. You clearly have a yacht with pedigree, consider very seriously removing all the ply and replacing it with iroko. Don't worry about the bending, that will be no problem at all. Again, I've been there; indeed even scarfed in 24ft of beam shelf at 3.5" x 1.25" with no problem including the bending. What you do need is clamps, clamps, clamps - no even more clamps!

In removing the ply you get the opportunity to check behind it for any damage.

There is no value coating it with epoxy. A good sound paint job is all it needs and will last longer, flexing with the wood and allowing it to breath like was intended.