folkboat transom replacement/sealing

[woolleyhatter]

Greetings all
I'm replacing a transom on my FB (exchanging the mahogany for oak) and i'm at odds of what sealant/bedding mastic to use. That said should i just seal it with epoxy and bond it on, or indeed does it need to have a bedding mastic?
Any advice is as always appreciated.
Regards

[RFNK]

How are you making up the transom? How are you joining the transom planks? The only mahogany on our Folkboat is the transom and it's the only place where I've had rot. The rot was in the top corners where there'd obviously been a bit of impact damage that wasn't repaired well. I really don't think mahogany is a very suitable wood for planking or transoms. Unfortunately our Twister is planked with mahogany. It's just too soft and prone to rotting above the waterline, especially if it sustains any damage.

I'm assuming you'll use silicone bronze screws to fasten the plank ends to the transom below the waterline? The only issue that I'd be concerned about would be possible movement in the joints below the waterline due to swelling of the oak transom and the planks. Epoxy is the strongest solution but it's possible that swelling timber could fracture the inflexible epoxy, rendering the joints prone to leaking if they fail. Maybe Sikaflex or similar would be a better solution. Above the waterline, I'd use epoxy as the situation is more stable and you can take full advantage of the strength of the epoxy. Rick


Rick

[Lou Kovatch]

I just did my entire transom,,,a 40' 1939 cruiser,,,do not use the epoxy if your boat will flex..2 years ago, I did my foredeck with epoxy/ graphite,,and oh boy, what a mistake...I had to remove the entire fore deck and replace with new teak...1000.00 bucks gone..the epoxy will Not allow the wood to flex the way it should, and believe me,if it wants to move,its gonna move...the epoxy would not allow the wood to flex, and split the teak beyond the cut grooves.....Now, my transom is also of South African mahogany, with an inner layer of cedar...3/4 cedar, 1/2" mahogany....I screwed my cedar down at intervals, then the mahogany layer, I both screwed down and epoxied to the cedar to keep water from between the boards...This was advice I had gotten from a woodenboat bulider nearby...I used all silicone bronze bolts above and below the waterline...I was told not to mix metals,,,go with one and stick with it,,,My transom planks,I match cut them all and marked them prior to joining them...as far as mahogany and water,,,mahogany is very resilient as is white oak to water,,,make sure you treat your white oak with cuprinol.....My boat is all mahogany at the wheelhouse and white oak for framing, with cedar for hull material....the mahogany will last well, as long as it is taken care of every season....all my joints got their fair share of cotton in the joints, seam seal where needed and the mahogany got 13 coats of varnish.... lets see, swelling,,,I have had no swelling of my oak below the waterline,,,nor of my cedar,,,I was advised not to use 5200 where there was a wood to wood interaction,,because the 5200 would not allow the wood to go where it "needs" to go,,,it would stop a good seal.....if you need pics or help, give a holler,,,,I have complete pics of what I did to my transom on the rebuild....I had a small hole, that turned into a complete transom,strut blocks,rudder block rebuild.....a 3/8" hole and 10 months out of the water....yeeeha.... if you need help or some pic references, give a holler.....

[RFNK]

The transom shouldn't be flexing much - it's a very strong part of a Folkboat. The planking and transom will swell underwater, otherwise this clinker boat will sink. It's unnecessary to use silicon bronze fastening above the waterline as out of the water there's no risk of crevice corrosion in the 316 stainless. As far as the use of epoxy below the waterline goes, it would be good to get the advice from others about that - I'm just not sure whether epoxy would hold properly to the swelling planks etc. Above the waterline, I think it would be the best way to ensure that the planks are well fastened to the transom to prevent movement and keep the hull as tight as possible. Our hull is clinker but differs from most in that it was all glued along every seam with resorcinol, the planks are plywood and it's all as tight as a drum - after 50 years. It's also apparent that the quality of mahogany varies greatly. I'd never use the mahogany I can get in Australia again. Rick