Transom Troubles

[seandwyer]

Well, it would seem that as soon as you finish one project another surfacing, uglier than the last.

I had just installed my wood work and was preparing to take the bout out to the lake tomorrow for the first sail. The sail I had intended to make each of the last three weeks. I went over the boat inspecting all the hardware and tightening. When I got to the brackets that hold the rudder on I noticed some screws were loose. I reached under the deck to get a wrench on the nuts there and found the board that sits against the hull almost completely and irretrievably rotten. Serious rot.

So I have some questions about fixing this. Not all the screws are in rotten wood. In the picture, the top two outer and bottom two outer screws are in "good" wood, while the top and bottom center screws are not. Essentially, everything that is "wrinkled" looking (paint) is rotten. Oddly, the majority of the rotten wood is in the center of the board. Not the edges, not the top or bottom. But the wood that is rotten is so soft that mostly its just the paint holding things together.

So, number one--could I sail with things like this over the next week or so while I make a new board in the evening? I'm betting it has been that way for a long time--it definitely didn't ALL happen over the winter. As a matter of fact, I may have bought it that way and just never noticed over the last several years. I'm sort of going crazy here. I had planned to be on the water at the beginning of last month!

Number two--does anyone have a suggestion for a specific species I should make it out of? I have a big piece of ash I am thinking about using. Would that be OK?

Number three--how is that board held in there and what's the best way to get the old one out without hurting the hull? I'm assuming that it is held in at the top and bottom with fiberglass tape and epoxy. Is that the fastening method?

My plan is to cut a board to shape, then cover in glass cloth and epoxy, then once dry, glass cloth and epoxy in place, then drill my screw holes from outside the transom so as to have them exactly where they had been. Should I cover the entire board with cloth and how many coats do you guys think are necessary? How many layers should I use to fasten it in place? Are we talking about buying another quart and a half of epoxy?

Thanks for the help...

[GreenLake]

... went over the boat inspecting all the hardware and tightening. When I got to the brackets that hold the rudder on I noticed some screws were loose. I reached under the deck to get a wrench on the nuts there and found the board that sits against the hull almost completely and irretrievably rotten. Serious rot.

Not untypical for this boat.

So I have some questions about fixing this. Not all the screws are in rotten wood. In the picture, the top two outer and bottom two outer screws are in "good" wood, while the top and bottom center screws are not. Essentially, everything that is "wrinkled" looking (paint) is rotten. Oddly, the majority of the rotten wood is in the center of the board. Not the edges, not the top or bottom. But the wood that is rotten is so soft that mostly its just the paint holding things together.

That's what's been holding things together for you so far.

So, number one--could I sail with things like this over the next week or so while I make a new board in the evening? I'm betting it has been that way for a long time--it definitely didn't ALL happen over the winter. As a matter of fact, I may have bought it that way and just never noticed over the last several years. I'm sort of going crazy here. I had planned to be on the water at the beginning of last month!

You should probably not sail this "as is". But...
I could see where mounting a temporary backing plate (plywood, or even your eventual replacement board) might serve as a short term "fix". You would have to use longer bolts.

Number two--does anyone have a suggestion for a specific species I should make it out of? I have a big piece of ash I am thinking about using. Would that be OK?

This can be answered by a quick search, there are several places that list how well suited certain woods are for boat building.

Number three--how is that board held in there and what's the best way to get the old one out without hurting the hull? I'm assuming that it is held in at the top and bottom with fiberglass tape and epoxy. Is that the fastening method?

You would use an angle grinder or a chisel to cut the fiberglass along the edges. After ripping/digging out the wood, you'd sand everything flush, extending the sanded area 2" on each side.

My plan is to cut a board to shape, then cover in glass cloth and epoxy, then once dry, glass cloth and epoxy in place, then drill my screw holes from outside the transom so as to have them exactly where they had been. Should I cover the entire board with cloth and how many coats do you guys think are necessary? How many layers should I use to fasten it in place? Are we talking about buying another quart and a half of epoxy?

There's no need to wrap this in cloth.
Get a quart of laminating epoxy (the leftovers will last forever) or if they sell that, a pint (with the half-pint of hardener).
Coat your wood on all sides and press into place.
Prepare a plastic sheet a just a bit longer than your wood is tall plus 3-4" on each side.
On that, lay up 2-3 layers of glass cloth or mat or both, whatever you have (cloth first).
The fiberglass would be as long as the wood is tall and 2" wider on each side as the wood is wide.
Wet out each layer with the epoxy and squeegee off all the excess.
You should then be able to pick up the plastic and transfer the entire sheet in place (like a big, somewhat wet sticker).
Using the plastic, squeeze out all air, spreading from the middle sideways.
(You'll appreciate at this point how well you've removed the excess epoxy earlier)

Make sure that the epoxy is spread to cover the bottom seam to the hull and the top seam where it connects to the underside of the deck. I don't think you need actual "tabs" of fiberglass at those two locations, just make sure all openings and cracks are filled.

Even though it's not vacuum bagged, the large sheet will resist air getting into the repair and that will help keep everything in place. You might improve that by taping the edges and/or "clamping" the repair. Something like a bean bag chair would work well, or some large foam pad that you wedge in there with a stick pushing off the CB trunk (or from a board across the rear ends of the seat benches - you'll have to be a bit inventive.

After that has all cured, you take the plastic off and then you can drill from the transom side as you indicated, and you'll wet the holes with epoxy. Applying wax to the bolts means you can put them in before the epoxy in the hole has cured. Don't forget to paint to prevent UV damage (wash the epoxy with soapy water if not sure whether its a "blush free" formulation). At that location, use what paint you have, or even spray paint.

I haven't done this repair yet, but it's clear that it will be due on my boat not to far in the future, so I've been thinking about how I would attack it, and that is what I wrote down above.

[seandwyer]

Hey, Greenlake,

Wow--I like the idea of the big sloppy sticker!

So, as you envision this, I should wet the entire area of the board with epoxy and then press into place while it is still wet. Do you think maybe it would be best to allow the epoxy to harden just a little so that it doesn't run before pressing in place, or do you see this as something that happens as soon as the epoxy goes on?

Also, should I let the epoxy on the board harden before applying the "sticker" or maybe just get super tacky?

I also wonder what guys think about polyester resin. I just bought the cloth at the auto parts store and they, of course, sell a resin for fiberglass that costs a LOT less than epoxy. I chose to not buy it because I know epoxy works, but wasn't sure about that resin, which I think is polyester.

Assuming I wind up going with epoxy, is there any reason not to use different brands of epoxy together for a patch like this? I have some MAS left over that might be enough, but I sort of doubt it, especially if I have to wet through three layers of glass. I can easily buy West System locally, whereas System Three and MAS are mail order, unless I want to do some serious driving, which I don't. I have also been thinking about trying an epoxy I just became aware of called Raka http://www.raka.com/
They sell a few different kinds, but one of them has a UV protectant built in. They actually performed well in this epoxy trial where most of the well known brands were put to the test: http://www.oneoceankayaks.com/Epoxtest.htm but let's be real here--the reason I'm attracted is because they sell a quart and a half kit for 39.00 bucks and it reviews well. That's a pretty good deal.

[GreenLake]

I would coat only 5 (five) sides of the wood - leave the inside bare. You will only need a thin layer, so the epoxy won't be in a thick enough layer to sag and run. (Think paint). With the inside of the board dry, you can easily press it against the transom. Once the epoxy has kicked, or a little after that, you no longer need the support and can then apply the patch (sticker) which will complete the coating of the wood when you apply it over the inside face.

There's no benefit in using polyester. Epoxy bonds much better and also is a better water barrier. The fact that it costs a bit more should not matter enough for the small(ish) quantities concerned.

You cannot mix components from different vendors together. (And when you mix you need to be rather precise in measuring and thorough in stirring). You would mix small batches (so you don't have the epoxy go off on you with smoke). A solo cup at a time, or less.

You can work with batches from different manufacturers, they will bond to each other. If you want to use up some epoxy you already have, you could use it for either the wood or the fiberglass part of the repair.

This kind of repair, any of these brands will do.

About my favorite brand:

I can get SystemThree locally, and therefore I've been using it consistently and exclusively. Because my experience is "limited" to that brand, I mention it, just in case there are some situations where their stuff behaves a little differently. Once such difference is that SystemThree is blush free, that is, it does not need to be washed before painting. Some of the other brands are not blush free, and so require a soap water wash after curing.

For this job, the UV protectant matters little (the price may), because you are always going to paint the inside of your boat.

The test is very interesting, but it is unclear which of the System Three products they tested. From the date of the test I suspect it is the "general purpose" resin made by System Three - a few years after the test they came out with a new line of laminating epoxy called "SilverTip". It is very clear and to me seems a definite improvement over their GP product.

But, this is all over thinking because for this you can use any of them.

[UCanoe_2]

Sean, my transom has the same troubles as yours and will get some attention after I finish the centerboard. Ash has good mechanical properties for this application, but it is not the most rot-resistant wood for this spot that will stay wet. I have a piece of black locust that may go into my transom. Ordinary pressure treated pine would be an inexpensive but suitable choice. You may want to save the ash for projects like canoe thwarts or snowshoe frames, where its toughness, flexibility, and beauty can be used to good advantage.

Also, you may want to drill the holes for your fasteners oversize, fill the holes with epoxy, and then redrill to the correct size. That way any water that leaks through the screw holes will not penetrate the inside of your piece of wood.

[GreenLake]

Ash is good for tillers. As for pressure treated wood, it's an unusual and surprisingly logical choice. Normally, it would be something that you don't want to use near to or immersed in a body of water - not because of rot but because it leaches poison into the water. However, fully encapsulated like this, I can definitely see it. Even if moisture were to wick in through a crack, there's not going to be a lot of exchange going on - unlike immersion.

[seandwyer]

Hey, Guys,

Yes, board selection sort of stumped me because there are so many ways to go. Once I pulled all the rot out of the recess, I found that the board that had been in there must have been from the very start and the transom glass laid up on it. As such, I really feel like I need to replace it with something of the exact same thickness so as to fill that pocket back in. Even on the outside of the transom I can see lines in the jell coat that I had never noticed. They aren't cracks, but gentle curves where the glass was perfectly molded around the board.

So, in the end, I bought a small piece of marine grade plywood in half inch dimension and am working on cutting it to fit the odd shape of the bottom. Once I found how things were put together the 3/4" ash simply looked like to much work trying to plain it down to 1/2". Once I get the board cut, I'm going to seal it with epoxy, then glue and clamp it in place with epoxy and thickened fillets on the edges (if that is really a fillet).

I do really like the idea of black locust though. When I was a kid we made fence posts out of that stuff--even posts that held up a swinging bridge on my uncles farm. The stuff lasts forever and puts lots of holes in tires, boots, feet, etc. Those are some nasty thorns!!

I've taken some pictures and when this is finished I will try to post a "see as you go" guide to how it went.

Thanks!

[K.C. Walker]

Sean,

The marine plywood method is exactly the way I would have gone. It's much less likely to split. I think you can just wet out both sides of the joint, make some peanut butter thickness epoxy for bedding and press it into place. I would be careful to make sure that all edges were wetted out before pressing it into place, though. You could easily pull it in tighter by running some screws through the gudgeon holes in the transom and snugging them up (well waxed of course). Go ahead with your fillets and brush on some epoxy on the inside exposed surface and I think you'd be good to go. I see no reason to add glass. I think as long as your epoxy encapsulated you should be good for another 30 or 40 years, if not longer. And, yes a coat of paint for UV protection, though this is a somewhat protected location.

[seandwyer]

Well, the repair is mostly finished now. Because of time constraints, I used West System epoxy (available from the wooden boat guy down the street as opposed to driving forever or waiting on mail order). I must say, I am not as big a fan of West System as my other experience with MAS. The West product stinks for one thing, gassing off a formaldehyde sort of stink. That said, I was using a fast hardener, and in retrospect I think I would have rather had the medium. I wasted epoxy a few times as suddenly it cooked off, steam coming off and the plastic Solo cup melting in my hand--which sort of burned. But hey, I put it down. Eventually. The other issue with West is that now I have to wait a week or so until I can paint it, or at least that's what they suggest, so as to make sure any blush has fully come to the surface. So, because it is in a protected area I went ahead and bolted the gudgeons on so I can use the boat now.

Here's a blow by blow picture fiesta.

[seandwyer]

I used an angle grinder with a cutting wheel to remove the old glass, then a sanding disc on the same grinder to sand down to bare glass/resin around the edges. I used 1/2" marine grade plywood for the new board. I cut to fit, dry fitted and then clamped in place to drill my new holes. Once drilled, I removed the board and over drilled them a few sizes larger. Then I coated it in epoxy on five sides and let it dry. When dry, I mixed plenty of epoxy, thickened with colloidal silica (a West thickener) and coated a good layer of peanut butter thickness epoxy on the back of the board. I clamped it in place with my improvised "jack" clamp and then mixed more of the thickened epoxy for filets. I also bought a syringe (boy do they look at you funny when you ask for one in the drug store) and injected the holes from outside the hull with epoxy until the holes were completely filled and epoxy ran down inside. The next day, I washed everything with a scotch bright pad and warm water and soap, then dried things off with towels, then a hair dryer. When I was satisfied that things were totally dry I covered the board with 6oz glass and clear epoxy, extending the reach of the glass to its original 2" border beyond the board. After this dried I drilled out the holes and reinstalled the screws through the gudgeons, covering them with Pheonseal just in case.

[seandwyer]

If you look at the holes through this board they seem to be slightly off center, but essentially what I did was replicate what was there in the first place. The board had a definite pocket in the hull that I had to fill back in and the holes weren't perfect to begin with. I figure if it was good for 45 years, it'll be OK for another 45.

Sorry this post is chronologically backwards. I added things from beginning to end, but I guess I should have started with the end and worked my way back to the beginning. Hopefully this is still helpful.

[K.C. Walker]

+1 for it probably lasting another 45 years. I really like your jack clamp!

It's interesting to think about this era DaySailer and its possible longevity. These boats are so rebuildable. A "soft" transom on many boats is considered end-of-life. Yes, it was a pain to do, especially because you were thinking you were ready to go.

I used West System for years. It's really dependable. Back in the day, I used to have to order it from them direct. They were always really helpful and their publications are still worth reading. A friend who is a kayak builder gave me a couple of gallons of MAS when I was doing a big project a couple of years ago. I really like it and I don't miss the stink of West System at all.

Nice rundown on the repair!

[seandwyer]

Thanks KC. Yeah, that stuff stinks, especially when it starts really cooking. The steam that comes off it is obnoxious!

Again, sorry for the photos appearing backwards. Does anyone have a suggestion as to how to deal with this other than just writing and uploading the pictures in reverse order?

[UCanoe_2]

Nice job, Sean! Next time you need a syringe, go to a farm supply store and you won't get funny looks!

[K.C. Walker]

I know what you mean about West cooking off fast. It's a cold weather epoxy. MAS was formulated for using in Florida so all three of their hardeners are slower than West Systems fast.