Rotten transom on inflatable

[Ardenfour]

I've inherited a Seago inflatable on which the top 3 - 4 inches of the plywood transom have rotted. The remainder seems pretty solid, as does both ends where it attaches to the tubes. Any hints on repair procedure? Obviously chop out the rot, but then what?

 

[Iliade]

An idea: Get some ~2-3mm stainless steel sheet bent into a U shape to bridge the rot by a large margin both sides and top. Through bolt with at least 4 x 5mm bolts. Infill with plastic chopping boards. Fit a cast metal motor clamp plate or it may slip around.

If your woodworking skills are up to it perhaps cut out the rot leaving a broad chamfer, say 3" minimum. Let in a new piece of ply using a good two-part adhesive. (Cascophen resorcinol glue.)
I'd chamfer the sides at the front and the bottom at the back so as to give a degree of mechanical lock. Personally I'd still want to plate over the join, but then I'm paranoid.

Or do it properly and ditch the whole transom, re-glueing a new one in it's place. That's too scary for me though!

 

[lw395]

It's going to be difficult to do precision woodwork like scarfing in new wood, as you can't get the transom on a bench properly.
The big problem is the leverage the motor exerts on the top of the transom.
You can't just add heavy reinforcement to resist this, because you are limited by the clamps on the motor.

So I'd probably add a new piece of ply butted on top of the sound part of transom, then reinforce front and back, up to the limit of the motor clamps.
Then add some reinforcement outside the motor clamping area.
Alternative is to add the strength with metal or GRP.
It might depend what materials fell to hand.

 

[Boathook]

It's going to be difficult to do precision woodwork like scarfing in new wood, as you can't get the transom on a bench properly.
The big problem is the leverage the motor exerts on the top of the transom.
You can't just add heavy reinforcement to resist this, because you are limited by the clamps on the motor.

So I'd probably add a new piece of ply butted on top of the sound part of transom, then reinforce front and back, up to the limit of the motor clamps.
Then add some reinforcement outside the motor clamping area.
Alternative is to add the strength with metal or GRP.
It might depend what materials fell to hand.

That seems like a good way to me. Ideally the rot needs to be removed or 'stabilised' but I would add GRP to either side and round over the top. The top edge would require rounding to allow the 'cloth' to sit smoothly.

 

[Ardenfour]

Some excellent suggestions, many thanks

 

[CAPTAIN FANTASTIC]

I had the same problem. I dried the dinghy over winter and then fibreglass the transom both sides; it lasted for years.

 

[TQA]

Forget trying to scarf in a new piece unless you suffer from OCD.

Cut out the rot and apply GitRot to the exposed edge or epoxy will do as well. make sure you cut down enough in the center to allow the clamps to get to the doubler you are going to fit.

Now find a piece of ply and make a doubler for the top part of the transom it needs to overlap the existing cut down transom by at least 2 inches and be deep enough in the center to take the outboard pad. Glue and screw to the existing transom and apply the finish of your choice. Two or three coats of epoxy is what I would use but household exterior will work to.

For those of you with 2 hp eggbeaters 1/2 ply and wood screws will do. If you are an 18 hp driving power crazed numpty like me then at least 3/4 and one inch is better. I would also through bolt in the center and keep an eye on the joint line just in case.

If cosmetics matter then a 3 to 1 chamfer on the bottom edge of the doubler will improve the look of things.