I am sure you are right Arne, on all three points.
1. Marcus did also stress the need for drainage when we discussed it the other day – same as you. Any wood down there will be thoroughly saturated with epoxy. And Marcus suggested cutting in some small gutters - your suggestion of rubber pads might be a good one too.
2. Yes, the wood block does indeed take the full weight of the mast. If I was making the tabernacle in steel I would certainly weld a plate there, or at least use fastenings - but the challenge here is to avoid welding or drilling at that critical point. I thought 200 – 300mm might give enough gluing surface for the wooden block to get by without any welding (or fastenings.) David seems to agree and has suggested 200 would be plenty, and recommends gluing with Simpsons. I might just go 300 anyway. And keep an eye on it, as I will with all these first-time-trial things.
3. I guess it goes without saying that the mast heel plug should have a drain hole, a good point for reminder.
Arne, in a previous post you seemed to be suggesting plenty of clearance (ie over-size tabernacle) would add to the strength of the tabernacle – if I understood you correctly. It makes sense to me, could you clarify please if that is what you meant?
A half sheet of aluminium (600mm wide) will fold into a 160 x 160 channel, with “top hat” flanges of about 25mm – I am not sure at this stage what to allow for the folding, but the offcut (from 600mm) will be too small to be of any use for anything. To save an extra cut and make things quicker (and cheaper) for the engineer – why not use the entire half sheet and make a tabernacle channel of about 170 x 170. Since the mast will be packed out to fit the tabernacle anyway, why not go the extra 10mm, use all the material, quicker and cheaper – and even more cross-sectional area (strength in bending.) ?
Any problem there?
By the way, I think now it makes sense to forget all about filleting and coving the inside corners of the tabernacle etc to fit the mast – just use epoxy, glass tape, filler and some judicious use of encapsulated wood, and build the mast up square at the top of the tabernacle, and square heel plug at the bottom – and sand the resulting square block sections to fit exactly inside the square tabernacle channel. And make it around 170 x 170 to save a guillotine cut, and use up all the material.
(Maybe some of the clearance space could also taken up by bonding a liner inside the tabernacle, at least where the square blocks will bear - a bit of hard sheet plastic of some kind? A small teflon cutting board will go through a thicknesser quite nicely to make packers of the right thickness - for example...? (though I am not sure if even Simpsons will stick to teflon!))
What say you, David and Arne?
(PS Thanks too, David, for your most recent post. All points clear and understood.)