Phil Brown wrote:

 The second links to a site where the sailor looks to have tried different rigs on the same mast and tabernacle.  His steel tabernacle looks like it drops town to the keel around three sides of a post below deck. I haven't seen something like that before but it looks good.

http://sv-ulladh-log.blogspot.com/p/ul-la-junk-rig-conversion.html

Phil

Thank you again, all :)

The Havsfidra conversion page (link above) had also an interesting mast I haven't seen before:

1 1/2" PVC schedule 40 pipe with 1" x 1 1/2" cedar insert set in epoxy.

There is an article in one of the JRA magazines about the construction of Speedwell's tablernacle by Pete Hill and Shirley Carter, with photos.  I don't have the time to research which issue it was but it was sometime in the last 5-6 years. 

David Tyler wrote:

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.

Makes sense.  I'd  think that the "LAP",  Length Above Partners,  for the calculation for the mast diameter would actually be,  Length Above Tabernacle Top,  not length above deck. That will save me about 1/2 in thickness for the tabernacle sides. 

Would someone please be a sport and draw a simple sketch of these last ideas?

I'm still having difficulties in understanding the construction and usage that came up a few posst earlier. Sorry :/

David,

Wow, I just edited out much of my post thinking  I was making your idea too complicated. Luckily I had it on word: It began even longer with an idea about a vertical ginpole attached to the tabernacle to bring the Mast close to vertical but then why not use the forward facing tabernacle that way:

Original:

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. Or perhaps a hinge or pivot bolt would allow a larger mast. A hole through the mast base along with a locking clamp at the base would have minimal stress risk compared to one further up on the mast and would be easier to plug for additional re-enforcement, I think. (On my old cabin stepped stayed mast the hole in the step was vertically elongated to allow the mast pivot on the through bolt and on its heel and then set down on the step.)

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 1/16 SS plate by the pivot. The plus was its simplicity. A drawback was the additional windage it presented.