Rotted wood in transom

[mcqmga]

Hey Guys, While placing tiller on gudgeons on my Ds1 , I noticed wobbly and weakness. Upon further review all the gudgeon bolts were loose. Seems wood backing inside transom had rotted. I cleaned out wood and would like advice on best method of repair. Any advice appreciated.

[mcqmga]

https://photos.app.goo.gl/xHdqJT9yTpxnZvPp9

[GreenLake]

I would probably replace with marine grade plywood, but make sure that all sides are sealed with epoxy (same as the holes - the latter, you could overdrill then fill with thickened epoxy and drill that to the correct size). The idea is to prevent any water from getting at the wood, whether through cracks or via seepage in the holes.

If any wood is exposed at the back, just paint the epoxy to prevent UV damage.

That repair will then last longer than you'll own the boat.

[mcqmga]

Thanks GL!

[Brigdenj]

I just completed a repair on my DSI. Transom was rotten and water logged. It weighed 10 lbs removed! I cut the inside layer of glass around the wood core, easily removed the rotten wood which was delaminated and then ground the area clean before installing 1/2” airex foam and a layer of 1708 using epoxy. Came out great.

[GreenLake]

Welcome to the forum. And thanks for sharing your approach.

[Buster]

Greenlake,

I've got the same issue with my DS1. The screws on the upper gudgeon cannot be tightened. Could I over drill the holes, fill with epoxy, then re-drill and re-mount the gudgeon? That is, without a plywood backing plate?

The lower gudgeon is still nice and tight.

Upon closer inspection, the gudgeon is held by bolts with a nut inside the transom. (not wood screws) Depending on the condition of the wood stiffener, I could replace the bolts with longer bolts, a large backing washer, and re-tighten. Any advice appreciated.

[GreenLake]

My DS1 has a narrow as strip of encapsulated wood to hold the gudgeons. I don't think it has any other purpose than distributing the load from the rudder. Locally, the wood provides crushing resistance, so the bolts can be tightened. More globally, it spreads the load from the rudder over a wider area. Think backing plate.

Situations where rudder loads are extreme might be upon grounding but also if your stern is struck sideways as in a collision with a boat that fails to properly pass behind you. Or simply doesn't see you. In busy waters these things can happen even if you aren't racing.

What you don't want is for that to crack your transom so you take on water.

Overdrilling and filling with epoxy addresses the issue of crushing loads from the bolts.

If you simply keep the rotted wood encased you aren't doing anything for distributing the load for those extreme events.And the whole structure may be soft enough to allow the transom to flex in normal usage, weakening it.

You could just add a layer of glass or two over it. That would strengthen the support, causing it to be like a hollow beam. That might make it stiff enough to work as intended in distributing the loads. However, if you encase soggy wood it risks swelling in a frost, cracking open your "hollow beam".

This should give you enough information to decide what you want to do.

If your boat also has that buried 6x1, you might decide to slice open the glass holding it in place (an oscillating saw would work well for that) and to remove the wood. Replace by new wood or structural foam, but overdrill the holes quite a bit if the latter, or only enough to seal the inside of the hole with liquid epoxy if the former.

Replace the glass you cut off to get at the rotten wood. If foam, make sure to build up a strong enough laminate as all the strength is in the skin.