Thoughts on carvel hull repair

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Ross1

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Looking at a carvel planked hull. 10-15 planks have rot below the waterline at the point of a frame (6-10 inches wide)! the planks are 15m long and replacing each one obviously expensive. Is it possible to scarf joint planks in at the point of the frame, each one staggered....or will this permantley effect the integrity of the hull!!!
 
It can be done. The key point is the shift of butts. No butt may lie in the same vertical room or frame unless separated by 3 clear streaks. Horizontally they should be more than 4 frames apart if in adjacent streaks. Avoid short planks as they are hard to bend to place. You should try to exceed these numbers as much as you can.
If she has sawn frames you may use plain butts on the frames, otherwise butt blocks between the timbers. H C Jurd in Yacht Construction recommends that scarfs can be feather edged inside but should be lipped outside. Lips may be dispensed with if the scarf is to be glued, but I would recommend extreme care with glue on a hull of this size as she is probably old enough to have all sorts of stuff soaked into the planking that is inimical to glue.
 
Because of the number that need replacing by the time one has staggered all the joints one will have alomost replaced a majority of the full length planks any way!
 
You may get away with shorter lengths if you scarph and epoxy. This doesn't quite turn the wood back into one piece, as the ads claim, but it's significantly stronger than butt joints. Whilst you're at it, think about routing out all the top side seams and splining. Once you've done this, it's no longer necessary to stick to original plank widths for cutting out rot. Cut it out - scarph it back in again.
 
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