2015.11.02 - To Glue or Not to Glue
The work has continued on slowly these last few days since the last few veneers have needed to be steamed in order to get them to bend in the tightest part of the bilge without cracking. Having introduced a curve in to the wood each piece has to be thoroughly dried before it is put in place taking more time.
Then there is a section on the hull where the damage has extended under the recently removed bilge stringer and that needed to be cut back as can be seen in the photos below.
The wood from Robbins Timber arrived as did 150kg of lead. The wood has been stored in the rafters of the workshop, the lead by the forge ready for when I recast it into smaller pigs for blast. Well, 130kg of it or so.
However, today’s burning question is whether to glue and screw the boat back together again or not. This is a difficult and contentious issue amongst the wooden boat community. Glueing and screwing certainly gives a very good result but it is difficult to take apart again when repairs are needed, and repairs will be needed at sometime or other.
The alternative is to use a sealant instead of the glue. This has the advantage of being less difficult to take apart and you can usually do it without damaging the wood, but it is a lot more expensive and does not give such a strong boat although it may be strong enough.
I’m leaning towards glueing but the effort that has been required to get Naiad to this stage does make me wonder it I am wrong about that. Something will need to be glued, of that there is no doubt but everything?
The lead is for ballast. Shoal Waters had about 280 lbs of lead in ten pigs arranged either side of the centreboard. As you can see from the photos of the project, there is quite a lot of space around the centreboard case to put the pigs provided that they are not too high. So then, time for some maths.
280 lbs is about 127 kg, so 127 kg is close enough to start with. The density of lead is 11340 kg per cubic metre or 11.34g per cubic centimetre. This means that 127 kg of lead will require 12700/11.34 cc of space or about 1120 cc, say 11litres. So if I want 10 pigs, 5 either side of the centreboard case then each pig will be 1.1 litres(ish).
Now, a litre would take up a cube 10 cm x 10 cm x 10 cm which would be very awkward, so I thought about how I was going to make these things and to do that I bought an industrial loaf tin that is 25 cm long by 12 cm wide by 13 cm high. So the question now becomes how high would 1.1 litres be in the bottom of that tin?
Of course the answer is straightforward it’s 110 cm cubed / 25 cm / 12 cm or about 3.7 cm, which is fine.
As a check I decided to work the other way round. If each pig is 10 kg then I’d need 12.7 pigs. Let’s drop the weight to 120 kg to give 12 x 10 kg pigs, 6 per side then each pig would be 25 cm x 12 cm x 3.3 cm which is good enough.
So 10 pigs at 11 kg each or 12 pigs at 10 kg each.
When I get to the casting stage, I’ll weigh out 11 kg or 10 kg of lead, melt it and put it into the tin and then when it’s cooled it should be around the correct size.
They will not be too long either. 6 pigs will take up 1.5m of length and there is going to be around 2m of available space. This has the added advantage of being able to move the pigs towards the bows or the stern to trim the boat once she is completed.
The new veneers continue on…
The extra old veneer cut away. The patches of white are excess thickened epoxy that I have been using to fill in the worst damage. I set myself a target number of veneers to put in place and then stop once I have reached that target. Any epoxy left over at this point does not get wasted.
The extra cut away from a different angle.