Double diagonal floor repair. .advice really needed

[ErikBenson]

My 1953 ex Royal Navy Fast Motor Dinghy had a bashed in bit of floor


Situation at the moment.

I have cut out the damage in the floor -ie a rectangle (about 2' by3') from keel across to chine of both top and lower planks. My intention was to replace the inners with marine ply ( already cut and ready to fit.)
I then removed all the outer strips which cross the hole and have made new ones,-( the mating edges are not absolutely perfect against each other, but I had thought to bond and fill with 5200).
All is ready to fit back up. . .however I now have some serious questions as to how to procede.
I have not attached anything permanently.

I had thought to treat all the wood in the repair patch with epoxy to seal it before fitting. This would also allow me to leave out the cloth membrane and replace it with 3M5200, thus giving a complete seal.

Problem- what do I do to the rest of the hull?. . . .ie- I cannot get the epoxy resin in between the double diagonals. . .and if I treat only one side of them the wood will warp and possibly pull out rivets when the other side gets wet on the inside.

Also . . .the boat has been out of water for many years and the outer double diagonals at the front have quite wide gaps between them , partly clogged by old paint.

Because I will be trailering the boat and not leaving it in water to swell the wood , I need to have some form of permanent seal.
I read that it is folly to just fill these gaps with Sika or 5200 as the wood when it gets wet would have nowhere to go and pull out the rivets again .

Then I read that glassing the bottom , out to the chines is acceptable and has worked for ages on some boats. Even the BMPT have done this to their example.

If I take this course, maybe I should not use the ply patch but refit in untreated wood and use a cloth membrane. This would keep the boat as original , but not solve the dried out rest of the bottom of course.


What to do next ?

Finish the repair as original , and turn the boat upside down , rake out the old paint and strip all paint off and then glass the bottom.
To protect the wood. .do I then treat it from the inside with some sort of anti-rot product/paint ?


Note:
I have Don Danenburg's worthy forum telling me to replace the whole bottom of the boat, or stay near the beach ! . . . and then I have Jim Trefethen's book saying glassing is perfectly acceptable.
Life is short, and I just want to 'mess about with my boat", not rebuild the Ark.
Apart from the aesthetics matter, would it be possible to reverse this move some day if someone wanted to restore the boat to totally original?

AAAAAAAAAAAAAAAAaaargggggghhhhhhhh.

Any suggestions , however rude or impractical will be considered.. . .spring is in the air.

 

[Paglesham]

Glassing is fine provided you do it with epoxy and use an epoxy compatible cloth/mat. Epoxy won't stick to standard mat and polyester resin won't stick to wood! If you can get hold of anything in Wooden Boat mag by Dick Clarke of Lake Tahoe that'll tell how he does this treatment to all the Chris-Crafts he restores. He also mills a slight groove above the water line into which he tucks the glass.
Good luck.
Martin

 

[misty56]

I wouldn't be rude!

First I'm not really sure what you mean by "floor." To me that's what I walk on in a house and on a boat, it's a double-horn shaped piece of timber or whatever that sits over the keel and ties the frames on either side together. Somehow that is not what I'm seeing when I read your post.

It looks like you actually mean the damage is to the hull itself, which is a lot worse, especially with double diagonal. The proper way to repair this is to cut back to good wood in the outer skin to about six inches and in the inner skin to three (more on a big boat or a big hole) more than the damage, cutting each plank square. Then fit matching material to what's there. Fit new oiled cloth between the layers (get charity-shop thick linen sheets or buy calico from Whalleys.)

John Scarlett describes his method for this repair using a temporary mould fitted inside the hull and working from inside out on page 74-75 of Wooden Boats-- PM me with an email and I'll send you a copy of the pages.

I was shown another way, as follows: Fix the outer skin repair in place first (because the smaller size of the hole you have cut in the inner will allow you to brace the outer repair in place) and once that is done, fit the inner repair in the same way. This certainly works on smaller repairs. Note: with this method the cloth goes on first....


If you use ply on solid-timber DD, you have to remember that ply does not swell and shrink the same way as the original timber does; so your rigid epoxy-fixed repair will soon start to crack, letting in water and causing rot, and then you'll have to do it again.

IMO epoxy has a place, for for laminating coachroofs and such-like, but I personally would not use it in a hull repair. I've spent a long time doing up old boats and houses and IMVHO modern plastic products when used to repair trad materials will
1 Look great for a while
2 then they'll fail
3 they won't fail consistently so
4 to do subsequent maintenence/repair you have to get all the first lot off but
5 some of the first lot will be stuck like the last fiver in a miser's paw and
6 you will end up doing more damage than there was in the first place just to get it all right again.

Epoxy for hull repair is a repair of last resort, to keep it afloat till you do a proper job. But that's just my opinion.