I see that we have written nothing since June to indicate progress… Well that’s partly holidays, partly a dose of shingles, and partly because I have been more focussed on building than writing (no bad thing I guess).
Planking at last
Well we girded our loins and bank balance and ordered the kilometer of Western Red Cedar required for planking of the boat. We ordered this from Barry Biddlecombe at cedarstrip.co.uk . Barry has been very helpful and supportive in the process, and his prices are excellent (no connections, just a happy customer).
I will take a picture of this pile of wood (a much smaller pile than you would imagine (a cuboid of about 0.5M square and 3m and 5m lengths))….
The planking process
Louise and I are getting faster at fitting these to the boat, but it takes about 45mins per plank. We started by scarfing planks together to form 27ft lengths, but found that manhandling these lengths was really difficult, so we are now fitting them in two halves, and staggering the joints.
Again using advice from SBA members (Mike Bell and Nigel Thompson) and Barry from Cedarstrip and a lot of reading Dave Gerr’s book on scantlings I decided to reduce the cross section of the strips (and increase the thickness of the cladding). We reduced them to 18mm by 33mm (against 22mm by 33mm as specified in Selway’s plans) – the intent was to make the planks easier to fit (as producing compound bends needed in a sample 22×33 strip seemed close to “impossible” for me).
We have tried a number of approaches to holding the planks in place, but the current scheme is a combination of wedges, clamps and screws with penny washers, which seems to work.. see left…(click for a bigger image)
Clearly there is a limit which we are approaching as we reach 10 planks on a side, which is the length of the clamps and their ability to be hooked over the deck clamp (and they work much better than the wedges) – so we are going to need to modify the approach soon…
We also deploy some clamps to help twist the planks – these are clamped to the plank so that the long end of the clamp lies inboard, and then use some string/rope to put the twist on the plank.
Fitting now goes quite quickly – first move all the blocks on the moulds to the right height for the new plan (unscrew and rescrew 72 wood screws), then apply glue/epoxy to existing plank (and new one in the case of epoxy), then fit loosely with wedges, pre-drill for the screws at mould stations, add intermediate clamps (using blocks at the top to avoid damaging the new plank), then tighten wedges, then add screws (making sure the the plank is tight to the mould) – this is actually a bit complex as you need to get the plank tight to it’s neighbour before the screw is fitted, but without the screw the plank will not be in it’s final orientation), then remove all the glue/epoxy that has (hopefully) squeezed out of the joint, and use some epoxy to make the fillets which help secure the plank to the stem and transom, then go round and round checking and tightening – lastly add stainless steel screws to the plank at stem and stern (these are the only ones that stay in place… Our record is fitting 3 half-planks in a day! It strikes me as quite odd that in fact you could produce a complete hull without the screws at stem and stern (they are just belt and braces) and build the whole hull without a single screw or nail)…
Here are some more pictures of the process… (we are now in a rush to try to fit all the planks before the weather turns too cold/wet for epoxy work)….
You might recall we had some concerns over the strength of the glue when it was “gap-filling” so we have decided to mix epoxy and glue approaches (not together you understand 🙂 ) in the construction. As we already decided to fit each plank in two parts (bow and stern) to make it easier to handle, and because the level of “twist” required in the planks is much less in the stern (due to the simpler lines of the hull there); and because the planks sit naturally better where there is less twist, we have decided to use glue (Titebond) on the stern planks and use epoxy (West System) on the bow planks (where there is a greater risk of inter-plank gaps that need filling).