Transom repair

Rebuilding a 1969 Grady White Atlantic, reportedly the last year they made wood boats. The transom is two layers of solid boards, outer layer is three horizontal, inner is several vertical working across the transom. In both layers the boards have shrunk and so I have gaps as much as a few 8ths on an inch between, but everything is solid. Wondering how I should fill the gaps.....

 

Welcome to the forum.

You don't fill the gaps. These planks were "edge set" and they did use a Dolfinite style of seam sealant. A modern build like this may still use Dolfinite, but polysulfide or polyurethane would be a better choice.

The reason the gaps have opened up is twofold, the first is some shrinkage, as you've noted, but mostly it's because the fastener holes have "egged" out and fastener corrosion, has weakened their grip, in these now over size holes.

The fix it disassembly, removing all the fasteners, restoring the holes and installing new fasteners. If this had been caught is a regular maintenance routine, you could have simply refastened, but it's likely the transom is way past this type of repair.

The fasteners all over the boat will probably be suffering from the same things and the repairs are similar; restore the worn out fastener holes, repair/replace cracked and broken frames/planks and refasten over polysulfide in the laps or seams.

That particular boat is well known to have tension cracks in the turn of the bilge sections of the aft frames. Sistered repairs are common to see on these and this is acceptable, if a cluttered look. I prefer to scarf in frame repairs, for a seamless look under paint. I know you think she's sound, but I work on this type of boat of this vintage all the time and I can assure you, there's a whole bunch of stuff you haven't seen yet. Refasten the transom and drop it in the water, with some sand bags to simulate the outboard weight, fuel tanks, etc. and a full load of well fed skipper and guests. Don't fill the boat with water (regardless of what some old timer might suggest), unless you want to fix a whole lot more than you need to now.

 

Transom

Thanks PAR....wasn't even sure where to start. When I back out fasteners is a 3M 5200 or 4200 the recommended filler?

 

3M 5200 and 4200 are adhesive/sealants, not fillers.

What is your experience level with old, lapstrake boats? This build method has some unique things about it, unlike other builds, so some familiarity is needed.

The first thing that needs to be done is a solid assessment of the structure and the hulls actual shape, which might be distorted by a weaken structure. With this in hand a plan of attack can be utilized to address the various issues.

 

Wood working experience, fiberglass experience both ok. lapstrake first.

Overall hull and shape appears to be good. 99% of the frames are fine, it is the stern most 5 or 6 that were rotted at the keel line in the bilge, probably back 12" on each side from the centerline. The transom itself is solid, it's just the separation that is clearly apparent there.

 

Can you post pictures of the aft bilge (inside)?

 

inner bilge area.

 

Paul,
White oak to sister damaged ribs?

 

White oak works well, but live oak works much better. I'd also be inclined to scarf in the repairs, rather than sister. A sistered repair is acceptable, but sloppy looking and adds weight. A few frames it's doesn't matter much, but I've worked on lots of this type of boat and the bilge turn will have "tension cracks" in the frames, typically where the planking fasteners penetrate them. This is why I wanted to see the bilge, uncovered, so the frames can be looked over. This is a very common problem among power lapstrakes and not that bad of a fix, if you catch it early enough.

Below shows the scarf repair and under paint, you'll never know it's there. This is also a typical location for a tension crack (which can be hard to see, if you don't know what to look for).