Annie, your blog has given me hours of interesting reading, but I had forgotten about it lately. Now I find you have described the making of your tabernacle - wonderful - I have wanted for some time to come and visit you to have a look at it, but reluctant to interrupt your valuable boat-building time. Now I don't have to, its all in the blog! (By the way, your link did not work for me, but your blog site address is easy to remember.)
Much praise too, to Pete - nice job.
I want to add an unsolicited comment - not that I have had experience with this kind of tabernacle - but as an ex-hiab truck driver, in another part if my life, I have made plenty of money on the side pulling masts out for people and decided many years ago my "ideal boat" mast would have to be self-lowering. My last boat (a stayed gaff rig) had a tabernacle of sorts, and the forces involved in raising and lowering a heavy mast were no problem at all - a 2:1 purchase on the anchor capstan winch - and a ten-minute job to rig a halyard down to it, via a strut. An easy one-person job. But the tabernacle itself was just a little deck fitting with no sides, with the pin/hinge at the foot of the mast - an over-size version of what trailer yachts have - and wouldn't do for an unstayed mast.
My comment is this - I think we have a bit of a fixation about the pivot point - I see no need for pins or any other kind of hinge fitting with this kind of "proper" tabernacle. It is one thing if you are raising/lowering the mast every time you go sailing - or if you are going under bridges frequently etc., but if it is just going to be the odd occasion when you need to lower the mast, why have a fitting at all? I rather prefer to have the front part of the tabernacle bolted in place to make a strong four-sided box when sailing - its only a moment or two to remove a couple of stainless bolts and open it up. The mast can then fall back (under control of course) and just pivot back over the top of the tabernacle. It might be nice to have that part shaped or padded a little - and much better if the sides of the tabernacle extend up a little higher each side than the pivot point at the back.
(I am pondering the possibility of having a trailer-boat roller mounted there for the mast to pivot or roll back over, as next move would be to slide (or roll) the mast forward prior to making it fast in its horizontal position. The tabernacle then serves as a fore-gallows - if there is such a word. This is a slight complication as the mast then has to be restrained from rolling forward while being lowered - not necessarily a disadvantage, but that's another story and lets leave that part for later)
Of course, it is not quite as simple as that - everything needs to be held in place while the mast is coming down, and you can't afford to let the mast fall one side or the other. I never found that to be a problem with my previous arrangement which worked while on the water - the boat just needs to be level and not allowed any roll during the process - then gravity will act the way you want it, your lowering mast has enough stability (just) and although I fussed about this and took precautions to begin with, I quickly found that in sheltered water up the creek here, the forces would stay vertical and no lateral support was ever necessary. And the pin/hinge arrangement at the foot of that mast could never have provided the slightest amount of lateral support - it all relied on the mast naturally falling through a vertical plane which it wants to do. No rocking the boat though - instability is never too far away!
Anyway, to get back to the pin/hinge question - yes, a pin or hinge will give a little lateral support while lowering (though possibly not enough if the mast started to go over the side.) The sides of the tabernacle will give some lateral support during part of the lowering process - enough in my experience. If you are worried about lateral support and decide to take precautions then I think you would probably want to temporarily rig some kind of lateral support higher up on the mast anyway, not rely on the pin or hinge.
I see a pin or hinge as mainly just to keep the mast close to the pivot point and stop it from falling out of the tabernacle or sliding forward during the lowering process. I can not see why a simple lashing would not do the same job. Why not just have a cleat mounted on the tabernacle, up near the top, so before opening up the front of the tabernacle you just lash the mast in place at the pivot point with enough flexibility in the lashing to allow the mast to roll back over the top of the tabernacle - but tight enough, or in conjunction with a preventer to stop the mast slipping forward as it is lowered, if slipping forward is thought to be a problem.
(It would be best if the sides of the tabernacle extended a little bit higher each side than the pivot point at the back. But unless you have a little bit of surplus length to play with there, it looks like that might be a little bit too late in your case.)
Most of my ideas don't quite work until the time comes to put them into practice, and then something usually needs to be changed. This might be a case in point, but I think it could be made to work and on mine I am going to try to avoid the use of any fitting bolted/welded/screwed to the mast at the pivot point, just a lashing. Maybe I will end up with a red face, but I offer this in the reasonable expectation that others will now chip in with better ideas. (I bet Arne can come up with something better!)
Thanks for the effort you make in maintaining your blog, I can assure you it is worth it.
PS if a pin is considered necessary, then I am sure you are right to have it at the back of the mast rather than "a damn great bolt through the middle" (as you so delicately put it in your blog.) So, why not just lash it to the mast when needed, rather than fix it permanently. Or find some other way of clamping on a removable hinge of some kind.
I suppose, in the most general terms, my point is really that a hinge/pin fitting is only of use during the actual lowering process - the rest of the time it does nothing, so why have it permanently fitted? And we all know you don't want to be drilling or welding anywhere near that point. Sorry, I can never express an idea in one sentence when fifty will do to begin with!