Getting a mast on a boat WITHOUT a real crane

[Chotu]

Originally Posted by Kelkara

since you're just moving the boat and mast to a new location ... does the mast really need to go on deck? it's an offshore catamaran, can't you just sling the mast under the bridge-deck between the two hulls?

Pull the boat up to a boat ramp bow in. slide the mast underneath still on it's trailer, then hoist it up off the trailer under the bridge deck. motor off to new location on a calm day. reverse the process at the other end and wash the mast down with fresh water.

This thread is FANTASTIC.

2 big winners in a day here.

When the problem is tricky, change the parameters. I could just float the mast out on one end and use the trailer on the land end. I can drive the trailer to the next stop empty and reverse the process. Brilliant.

This is definitely the plan now depending on how things go at the marina (if they will still permit me to work on the boat or I have to leave).

The other plan if I can stay is to do the hinged mast above so I’ll need to get it on deck. Even if I do move, I’ll do the hinged mast.

I’m actually quite disappointed in myself for not thinking of this idea to carry it under the boat. I have to admit I was stuck in old monohull ways of thinking. Loose mast? Put it on the deck. Old patterns.

No matter where I go it’s calm water motoring throughout Florida thanks to the ICW and I have an absolutely monstrous bridge deck clearance. So it probably won’t even get wet. Ha ha.

[Buzzman]

Yes, if the mast is just being stored, lashing it underneath the bridgedeck is not a bad idea, but beware the curves in the bridge deck VS the length of the mast. You might find you'll need to add some sort of pole with a U-shape at the bottom end at the forebeam area to locate and retain the mast before lashing the mast up so as to avoid putting it into tension and putting a bend in it. Spreaders also might hang very close to water so boat could only be moved in very calm conditions. No chop or it would crash against the underside.

But if you have the clearance and the height above water, it might work getting it on, but getting it off in the future might require a new trolley of some kind, as surely you won't be keeping the one it's on now?

My on deck solution I was actually thinking of leaving the mast where it would be simple to raise at a later date, but if you won't be raising it for some time, it's going to be there in the way at head height.....so lashing underneath might actually make more sense.

Also, I second what others said about the forces acting on the 6' stub with hinge on top. It really does need to be well supported and possibly needs some sort of tabernacle arrangement as well, and this would need to be closely and tightly engineered so that as the mast folds into its vertical position it would fold into a sort of 'socket' in the top of the 6' stub, and the base of the mast would need to come into load-bearing contact with the base of the socket on top of the stub, in order to transfer the compression loads without straiing the sheer load on the pivot bolt. Tricky but doable.

Having the stub/tabernacle would also make the actual fixing as well as the raising of the mast easier, as invariably the base on top of the beam on the hull is not the highest point on the centreline of the boat, so the aft end of the mast would still need to be raised high enough to get the hinge point at the bottom to mate with the deck-step. Adding the stub avoids this and makes that part of the job easier also.

[Chotu]

Good points Buzzman.

[Sand crab]

You might not need the exact mast profile with the stub scenario. There could be a beefier section on the bottom if that helps.

[Chotu]

Originally Posted by Sand crab

You might not need the exact mast profile with the stub scenario. There could be a beefier section on the bottom if that helps.

Exactly what I’m saying.

The bottom 6ft only needs to be close in size (but beefier) to to do the job. Makes it a breeze to find a section at a junkyard. The interface between the two has to be specially handled, so all the compression load is on the stub section.

[wsmurdoch]

How do you stabilize the mast port-starboard as it is being raised if the hinge is above the chainplates (post 92)?

[Chotu]

Originally Posted by wsmurdoch

How do you stabilize the mast port-starboard as it is being raised if the hinge is above the chainplates (post 92)?

That’s a legitimate question.

We were saying above that it would need a couple of guides. One on each side, in line with the hinge.

This is definitely the most tricky part of the idea.

Seems to me that it might need stabilizers aft instead of near the hinge. Then another pair by the hinge. Something like that. Definitely this detail is missing b

[Buzzman]

Most of the trailer-sailer solutions involve blocks or brackets that raise the pivot point of the lower stay inline with the base of the mast pivot, but in the case of a tabernacle, these blocks and the pivot points for the stays would need to be some distance off the deck, so could not be permanent. Making attachment, deployment and storage tricky...

Another option to consider is that the tabernacle itself could be part of the stabilising system. So if you simply added some ally tube to the base of the mast, then made the tabernacle out of slightly larger channel, both the pivot at the top and the pin at the bottom could be in the new added on section of mast, which itself was then inside the larger channel section that is actually fixed to the deck on a broad base plate.

Theoretically you might be able to devise a 'temprorary stay' out of dyneema or similar that was mounted to the deck or gunnels and that came up to a point in line with the mast pivot. Sort of like an old style traveller loop, but with an additional stay or two to prevent it flopping sideways. Essentially triangulating the attachment point for the stays a few feet off the deck.

I'm imagining the weight of the mast itself would keep the lines in tension.

It might be you'd need a four-part anchor each side. Say four lengths of line with a snap shackle at each end. At the deck end they'd snap into existing fittings or specially placed U-shaped deck anchors. At the upper end all four would attach to a ring, and the stay on the mast would then attach to that, in line with the pivot in the mast. So while the mast and stays could then move up or down, the four-part anchorage stays would cancel each other out, and stay put under tension. They could be straps with adjustable tensioners.....

You probably couldn't do this on a mono, but the huge beam and available deck area of a cat makes it simpler as the four stays would need to be in cardinal directions. Forrard, aft, outboard, inboard, all meeting at a point in space exactly where the stay needs to pivot.

If you can't picture what I'm describing, picture an old person's walking stick, one of those for proper geriatrics, with the four separate feet that helps prevent them falling over. If each of the 'feet' is one of the four 'deck lines' and the shaft of the walking stick is the stay....

Might that work..??

[malbert73]

Originally Posted by Chotu

That’s a legitimate question.



We were saying above that it would need a couple of guides. One on each side, in line with the hinge.



This is definitely the most tricky part of the idea.



Seems to me that it might need stabilizers aft instead of near the hinge. Then another pair by the hinge. Something like that. Definitely this detail is missing b

Why not build a permanent vinyl ester or Carbon tapered box structure with struts if needed and a hinge on top for your mast. No need to extend mast or find a section. Can probably mount winches on it etc… mind the aesthetics but may work best?

[Chotu]

Originally Posted by malbert73

Why not build a permanent vinyl ester or Carbon tapered box structure with struts if needed and a hinge on top for your mast. No need to extend mast or find a section. Can probably mount winches on it etc… mind the aesthetics but may work best?

Yes. That’s kind of what I was saying. Having the stub or base or whatever you want to call it take care of some of the lateral motion. Even almost all of the lateral motion. Isn’t there a way to do that? I see those things at Automated parking lots go up and down. They are about 10 feet long and have a very very small portion inside the part that lists and lowers them. They don’t have problems flopping around. Isn’t there a way to do that with the mast base?

There wouldn’t be any winches on that thing because everything is running aft. I mean, maybe a halyard that I never use or something. Worst case. But everything else runs to a sale control table.

[Sand crab]

If an internal pole was inserted into the mast base and then was somehow fastened to your deck then part or most of the problem would be solved. Maybe a SS pole welded to a base which then would be fastened by bolts and or adhesive would work. The gizmo might be fg with carbon fiber. Or maybe a combination of a fg structure coming up part way with the insert and stub for the top section.