Old skiff transom replacement challenge

[Tigosaurus]

Hello everybody! I'm sure glad I've found this forum. I've been working on a skiff that is in need of repair. I've replaced the benches so far, but the transom is more of a challenge. The boat was probably built in the 1970s and I'm not sure if the transom board has been replaced since it was manufactured. The rotten board was only 8 inches in height. Unfortunately, I didn't take a picture of it before I removed the rotten one..
Also, you can see the overlaps of the aluminum between the hull and transom, which is curved inward below the gunwale, creating a need to widen the hull while I insert the new transom. I have removed some rivets. The questions I have:
Do I need to remove the entire transom aluminum by taking off all the rivets, or just enough to remove enough rivets to pull the hull out enough to insert the transom?
Or will lining the gap with 5200 at the point I stopped taking out the old rivets, then simply replacing with new aluminum rivets do a leak proof job?
Should I replace with the 8" deep board, or go with a 12"?

 

[jbcurt00]

What are the scorch marks on the hull around the rivet holes?

Rather then opening the seams on both sides, why not remove the knee brace?

Thats what I had to do to work on my Duracrafts transom.

If you bend the hull out to try and slip a new transom into the now opened pocket, IMO, you risk damaging the hull.

 

[jbcurt00]

Watermann
classiccat
dozerII

 

[Watermann]

Welcome aboard Tigo :wave:

I sure wish you would've popped in before going through all the trouble of removing those rivets and breaking the seal in the seam. If you make the transom as wide as the sides of the hull there would be no way to force the sides wide enough to accept the new wood without stress buckling the aluminum on the sides of the hull where it is still attached with rivets.

The way I would've done the replacement would've been to remove the knee brace to clean under it and the 2 side brackets. That way the new wood could be angled into place and the brace/brackets then replaced. Messing with the seams is risky business at best.

 

[Tigosaurus]

jbcurt00
The scorch marks are from a tig arc. I welded up some holes on the bottom of another old boat that was in a useless state. The transom board slipped straight down into the knee brace back part of the transom on that boat, and I had experimented to see how the arc would work take the corner caps off. The rivets immediately mushroomed, making it easy to break of the rivets so I could punch out the back. The scorch marks brush right off and the holes are clean. For the record, however, not recommended.

I didn't want to remove the knee brace because of it being attached to the hull. But after discovering the difficulty of the alternative, it makes me realize it is the only choice. Thank you. The question is whether the 5200 "slathered" in between the the two "sleeves" and re-riveted will create a waterproof bond.

Another issue is the transom board. Doesn't seem like it would be a problem to increase ht from 8" to 12", can anyone see any problem once the fit is good? Also, would 3-4 coats of spar urethane be good enough? The new transom board is under the old one.

 

[Tigosaurus]

Watermann, discovered the forum by accident after I had started "experimenting". And removing the side brackets and knee brace will be the new plan. I can weld cracks, but after reading in the forum and otherwise, I plan to leave the welding to cracks and some holes only. I do appreciate your suggestions!

 

[Frey0357]

Tig: As far as the transom board replacement goes, the 12" versus 8" height really is not a huge difference, if the 12" is not impeding on anything and you already have it cut to this size then leave it (IMHO). As far as sealing goes, if not using epoxy, I recommend the WOG recipe that has been posted many times here on this site. I used it with excellent results!

1 part Spar Urethane+1 part Boiled Linseed Oil+2 parts Mineral Spirits. Let Dry for 2 days. Follow with 2-3 coats with straight Spar Urethane (pay close attention to the endges). Sealed!


Frey

 

[Watermann]

Yes I would increase the size of the transom wood too and I think it's a good idea. :thumb:

I use Helmsman spar for sealing the wood in my boats but I would also recommend a few coats of paint as well since that wood is exposed it couldn't hurt. 5200 will seal that seam back up and it's also a stubborn adhesive once set up.

 

[Tigosaurus]

Appreciate the information! I'm looking forward to applying it.