I have to have a pedestal made - why not a tabernacle?

[smj]

Instead of focusing on how to drop the mast to deck level using a tabernacle, possibly focus on how to drop the mast temporarily low enough to pass under a 65’ bridge. I’m sure the loads would be much lower doing this as opposed to fully dropping the mast?

[Knotical]

Originally Posted by NevilleCat

https://yachthub.com/list/boats-for-...proa-71/271980

That is a super cool boat - not a traditional cat but more like a Polynesian canoe with a side ama.

I like it.

[Rjstutch]

Originally Posted by Knotical

That is a super cool boat - not a traditional cat but more like a Polynesian canoe with a side ama.

I like it.

Yes they call it a proa, and I have to agree!

[Rjstutch]

Originally Posted by NevilleCat

https://yachthub.com/list/boats-for-...proa-71/271980

Looks like the new owner did a renovation!

[Chotu]

Originally Posted by thataway41

We successfully tabernacled a 60' mast. The pivot point was near the boom gooseneck, so the mast was laid into a crutch, then the mast was also in a crutch when fully down. We used a 12,000# capacity Holmes tow truck winch. We did have the upper shrouds with a pivot point at the same place as the mast pivot point. The mast was keel stepped, but we put the stub pivot point 7' off the deck. You could do similar, making the permanent part the pedestal you mentioned. The 7' section below the pivot point was cut out and the fulcrum for the winch. The mast laid aft, and the lower 7' were forward, and had the sheave for the cable from the winch at its bottom. You would have to do some engineering, and modification of the attachment of the lower 7' to the mast-but it would give you the extra height you want. We did have to be lined so we were going straight upwind or down wind, and in wind no more than 10 knots. It was a one person job, with a wired remote to the winch.

This is EXACTLY IT!!

Do you have any more information about this boat and its tabernacle system? Any pictures?

Did the boom stay on the 7ft section? Or was the boom in the section that lowered?

[Chotu]

Originally Posted by MicHughV

Let me get this straight.....this 60 something foot mast will be supported only by a line from the masthead to a gin pole and the pivot point. In other words the entire mast will be supported only on the two outer ends during rotation ?? Additionally, the support line from the masthead is not going straight up, but at a pretty pronounced angle towards the pivot point. This is going to result in quite some lateral load at the tabernacle, and if the mast does not stay inline with the centerline of your boat, substantial twisting load on top of everything else.

The mast will have it's spreaders, shrouds, etc, still attached to it. ie, it will be quite heavy, and still only supported by the outer ends during any planned rotation.

I see a lot of potential issues here from several angles and before you jump into anything, my suggestion would be to enlist the aid of a professional structural engineer or nautical architect to assess your goals and requirements.

I think it’s 300-400lbs if I remember correctly. Weighs as much as 4 dinghy outboards.

The spreaders and shrouds take care of your fears actually. They need a pivot point in line with the pivot point of the mast for that to work.

Regarding the angle of the masthead attachment point, are you familiar with a gin pole?

Aren’t you a structural engineer? Or mechanical engineer? Want to have at it?

I’m not opposed to help. That’s why this thread exists. To ask for help.

[Chotu]

Originally Posted by smj

Instead of focusing on how to drop the mast to deck level using a tabernacle, possibly focus on how to drop the mast temporarily low enough to pass under a 65’ bridge. I’m sure the loads would be much lower doing this as opposed to fully dropping the mast?

I guess because I want more out of this.

I don’t care about a 65ft bridge. I want to lay it on deck and do the whole icw like a trawler. To go under low fixed bridges to inland anchorages. Things like that.

It’s not about making 65ft bridges.

If I can’t figure this out, I’ll just pay a crane to do the same.

[Jdege]

Originally Posted by MicHughV

Let me get this straight.....this 60 something foot mast will be supported only by a line from the masthead to a gin pole and the pivot point. In other words the entire mast will be supported only on the two outer ends during rotation ??.

Given the forces that a mast had to be designed to handle under sail, I'd be astounded if the couple of hundred pounds that is it's own weight were within orders of magnitude of anything that would cause a problem.

[smj]

Originally Posted by Chotu

I guess because I want more out of this.



I don’t care about a 65ft bridge. I want to lay it on deck and do the whole icw like a trawler. To go under low fixed bridges to inland anchorages. Things like that.



It’s not about making 65ft bridges.



If I can’t figure this out, I’ll just pay a crane to do the same.

Then no doubt, I would plan on using the crane.

[Chotu]

Originally Posted by Jdege

Given the forces that a mast had to be designed to handle under sail, I'd be astounded if the couple of hundred pounds that is it's own weight were within orders of magnitude of anything that would cause a problem.

You are correct. I’ve already supported it from the ends and it is just fine.

I think MicHughV is talking about the lateral stability of it in wave action.

It needs a little more support than just the ends because the top end can start swinging around and damage the tabernacle. It needs something else to steady it. That’s that the shrouds do or a pair of baby stays do.

[MicHughV]

Chotu,

My advice and recommendation is simple.....hire a crane service. Sorry, I know you don't want to hear this.

[Buzzman]

Originally Posted by Chotu

Question: is there a mast raising/lowering system that can secure the mast from moderate lateral forces when it’s being lowered other than carrying special shrouds and supports to line up perfectly with the pivot point?

In short, no.

Whatever shrouds or solid stays you utilise they MUST pivot inline with the pivot point at the base of the mast. The higher up the mast this is, the higher the pivots need to be on the stay/shroud supports.


The received wisdom is to use a gin-pole off the forrard 'edge' of the mast, with a pulley on top. Run hauling line through this, attached to forestay, (and then via forestay deck fitting block) tailed to a winch aft.

Solid stays, pref removable, are better than flexible shrouds as they allow less sideways movement.

At best, you could (I was going to say epoxy, then I remembered your allergy) "fasten" some sort of cleat or bracket to the deck, to attach a fitting that would bring the pivot point high enough to be inline with the mast base pivot point.

If working the ICW you might leave these and the stays in place, making it dead simply to lower the mast *enough* at each low bridge, but you would not want them in the way if handling sails.


An acquaintance of mine on FB is re-engineering the mast-raising system for a Farrier trimaran so it is a four-piece, *parallelogram* lowering system, which was pioneered I think by Telstar on a similar tri in the eighties. There is a mathematical formula to use to calc the lengths of the arms and so on so that the mast can be folded easily and without gin poles etc. But it's complicated and requires precision engineering of all and stainless components. He's DIY-ing it and having some fun....
See video of a Telstar below... Of course, if you're just lowering enough to go under bridges, you only need to operate the system partially, eact time....and could probably do it solo....

https://www.youtube.com/watch?v=EeToe43DRHU

[Jdege]

Originally Posted by Chotu

I think MicHughV is talking about the lateral stability of it in wave action.

It needs a little more support than just the ends because the top end can start swinging around and damage the tabernacle. It needs something else to steady it. That’s that the shrouds do or a pair of baby stays do.

That makes sense. I've never raised or lowered my masts except on the hard or in a slip on a calm day. I'd not even think about it in open water.

For a mast that long you'd want supporting lines to the top of the mast that don't run through the spreaders, that could be actively managed to maintain tension as the mast raised or lowered.

Though with my short masts and solid tabernacles, I don't bother.

[Corvidae]

I did the tiny version of this on a dingy. Scaling up has a few differences. I got away with keeping steel rigging. At cruising cat size, Dyneema is going to be the only option. The stainless rigging on a cat would be a nightmare to handle. You're also going to have to deal with tensioning the rig after raising it, which can be a big chore on a cat, no matter the material.

Once big design flaw I made, that should be avoided. Make your hinge point higher than your head. And for your use case, make sure that total height from the water is 14' or less. That gives you full access to the great loop canal passages.

[Chotu]

Oh my god!

What kind of sorcery is this???

This is absolutely the most elegant method I have ever seen. This has real merit to apply to my situation, solving all the issues. The hard baby stays would solve all the problems.

Getting the baby stays at a balance point of the rig and holding the rig from a center point like that would work perfectly! Then I could just use a standard “dumb pedestal” as a mast base and that’s it. No need for all the complicated tabernacle stuff and all the support in the center prevents the wet noodle tearing out the deck hardware issue.

This is it. This is the way to go. There are no drawbacks other than a bit of weight for the a-frame solid baby stays.

Thank you VERY much for this post.

I had no idea this method existed.

It’s exactly what I’m looking for because it also solves the issue of moving the mast forward to position it correctly for traveling with the mast down.

With the right brackets to receive the mast and lash it in, it will be very stable for say, doing the icw for days through all those bridges.

Originally Posted by Buzzman

In short, no.

Whatever shrouds or solid stays you utilise they MUST pivot inline with the pivot point at the base of the mast. The higher up the mast this is, the higher the pivots need to be on the stay/shroud supports.


The received wisdom is to use a gin-pole off the forrard 'edge' of the mast, with a pulley on top. Run hauling line through this, attached to forestay, (and then via forestay deck fitting block) tailed to a winch aft.

Solid stays, pref removable, are better than flexible shrouds as they allow less sideways movement.

At best, you could (I was going to say epoxy, then I remembered your allergy) "fasten" some sort of cleat or bracket to the deck, to attach a fitting that would bring the pivot point high enough to be inline with the mast base pivot point.

If working the ICW you might leave these and the stays in place, making it dead simply to lower the mast *enough* at each low bridge, but you would not want them in the way if handling sails.


An acquaintance of mine on FB is re-engineering the mast-raising system for a Farrier trimaran so it is a four-piece, *parallelogram* lowering system, which was pioneered I think by Telstar on a similar tri in the eighties. There is a mathematical formula to use to calc the lengths of the arms and so on so that the mast can be folded easily and without gin poles etc. But it's complicated and requires precision engineering of all and stainless components. He's DIY-ing it and having some fun....
See video of a Telstar below... Of course, if you're just lowering enough to go under bridges, you only need to operate the system partially, eact time....and could probably do it solo....