“Btw, David Ty. presented a real Colombie-egg here, recently, by suggesting that the open U should face aft. On smaller boats, with fairly light masts, one can then just walk the mast up, right into the recess of the tabernacle.”

I had to look up Colombie- egg but now I really know what it means. Duh! That allows the pivot to be at the base, so much simpler. It allows the the base and pivot to be just a shallow box or socket.

With the beefy 2 sided tabernacle that Phil Bolger drew up, which worked fine for my square mast, I had to have a hefty U clamp at the base as well as a sizable bolt through the mast which was re-enforced with long 1/16 SS plates by the pivot.  The plus was its simplicity.  A drawback was the additional windage it presented.

Scott Dufour wrote:

I looked in my usual reference, David Gerr's "Elements of Boat Strength", as well as a few other places, and I can't find guidance for tabernacle scantlings.  I trust David's numbers, though.  Out of curiosity David, how do you calculate those? 

Pure empiricism, in this case. But for a case where I hadn't got previous experience, I'd consider the diameter and wall thickness at partners level that a wooden mast to PJR scantlings would need to be, for the height and sail area under consideration, and then attempt to design something of equal strength.

Jami Jokinen wrote:

Scott Dufour wrote:

My tabernacles are usually like a U shaped tube (viewed from above), made from three pieces of good solid wood, with the inside corners filleted and glassed, the outside corners rounded off and glassed.  The deck is cut with a shaped hole just large enough to let the tabernacle in.  

What kind and how thick should this wooden tabernacle be with a 6m mast?

Ideally, you would use a tough hardwood, but much will depend on what you can find locally. A very slow-grown native pine would be suitable. The thickness should be about 22mm.

(I elect to write this in this topic as it is specially for your boat, Jami)

Jami and Annie

choice of sailcloth

From a sunrot perspective I would not be so afraid of using up my stock of Odyssey III (220g/m²). Remember, up here on 59-60° north, I bet UV-radiation is less of a problem than in NZ and Australia.

However, if I were to make a new junksail, smaller than 20m², I would look around for a lighter cloth, say 120-170g/m2. I found on Frøken Sørensen (20m²) that the Odyssey cloth was just a bit on the heavy (stiff) side, so the cambered panels were a bit reluctant to inflate in very light winds.

On the 10sqm sail for my dinghy, Broremann, I used some light nylon (120g/sqm?), and that worked wonderfully well on that little boat (go to Youtube and search for Broremann)

Arne

I came across a mast hinge detail on the 'Tammy Norrie' blog I don't know if this may be of help. There is a lot more detail there.

https://tammynorie.wordpress.com/tag/mast-hinge/