Double-Diagonal Caulking

[Forbsie]

Can anyone advise whether I can caulk with cotton or oakum on my double-diagonal teak hull? I am sure that I heard that it wasn't advisable as the seams would close up on their own.

The boat has been out of the water for 2-1/2 years and some of the seams have opened to around 3-4mm.

Many thanks.

 

[NormanS]

Double-diagonal is a difficult beast. Don't caulk with anything that will not squish out when the planking "takes up". Best if you can wet the boat, either by launching, or possibly by using something like wet sacking.

 

[Keen_Ed]

Thought that traditionally, double diagonal hulls were kept watertight by oiled cotton (or modern equivalent) between the layers of planking?

Prob best to ask on the WB forum.

 

[Even Chance]

I'd personally use some acrylic sealant (non structural), that never really dries fully. It can squish out if it needs to as the planks take up.
I dont know any trade names off the top of my head.
Nice and easy/quick tip that was told to me by a boatbuilder of 45 years experience. Get the stuff you can paint over. Sikaflex make one.....

 

[Forbsie]

Thanks Guys!

I'll be using my special recipe squidge made with putty, grease, red lead powder and a splash more linseed oil which works really well but was wandering whether to lightly put in some cotton or oakum to effectively replace the calico(?) between the planks.

 

[clyst]

there are a couple of methods of building double diagonal craft . it would help if you described the type of boat .
Cheers

 

[cygnusv]

This may help

Can anyone advise whether I can caulk with cotton or oakum on my double-diagonal teak hull? I am sure that I heard that it wasn't advisable as the seams would close up on their own.

The boat has been out of the water for 2-1/2 years and some of the seams have opened to around 3-4mm.

Many thanks.

My first advice would be to speak to John at traditional boat supplies in Suffolk. Lots of knowledge and very helpful. If he doesn't know, he'll know a person that does.

My second advice is far more hesitant. The 2 layers of wood in the DD design should be separated by Linseed oil soaked calico. If this is in good nick the only thing I can suggest is submerging the boat for as long as it takes.

We have a clinker boat here that arrived October last year to be sunk on a shallow mooring for exactly the same reason. It is now floating, but not off the danger list yet!

I know that DD was used in WW2, a lot. Flexible, but of course new wood, fresh calico and Linseed, not too much to take up, light and strong etc etc

I know that it was usual to 'sink' a clinker hull to take up.

I'm happy that our hull is Carvel construction, much less stress!

 

[Forbsie]

there are a couple of methods of building double diagonal craft . it would help if you described the type of boat .
Cheers

Good point!

It is a 1905 ex-admiralty pinnace built with teak on oak. Diagonal inner skin, fore and aft outer.