Mast Hinge Question

[DavidF]

I know, perennial topic...

My new DS2 (1977) has a mast hinge. It is definitely not the most solid fitting, so I am trying to figure out if it should be replaced over the winter.

When raising the mast, the hinge provides a pivot point, but does not provide much stability. I don't know if this is an original fitting, but it doesn't look as solid as the one from D & R. Can anyone with a D & R hinge describe how stable it is. (I realize that the stays are what make the mast stable once stepped.)

Here are a few pics:
http://dl.dropbox.com/u/975964/photo%285%29.JPG
http://dl.dropbox.com/u/975964/photo%286%29.JPG

Thanks,

David.

[GreenLake]

David,

It's not clear from your fitting why there should be a problem with solidity. From your photos it looks like a comparable design (two U channels, one overlapping the other).

You correctly note that what holds the mast up is the action of the stays, with mostly compressive loads on the mast hinge.

In raising the mast, I think you shouldn't expect this to work like a door hinge. A bit of flexibility is good, because whenever there's a bit of give, that limits the forces that the fitting has to withstand.

The mast represents such a long lever arm, that any fitting without give would quickly be overwhelmed (or would have to be designed much sturdier). What that means for raising the mast is that you need to steady it yourself while raising it.

[ChrisB]

David,

I don't see anything about the tabernacle on your boat that looks any more or less robust than the ones sold by D & R or direct from Dwyer. In fact, yours was manufactured by Dwyer as their name is stamped on the piece attached to the mast. I agree with what Greenlake posted; the tabernacle is simply a pivot point. It's up to the person raising the mast from the horizontal to make sure the mast is raised straight (tip of the mast should be in the centerline of the boat fore to aft). Once rigged, the tabernacle only serves to hold the base of the mast in place while under compressive load.

[K.C. Walker]

I'll 2nd what Greenlake said. Yours is a Dwyer and more than likely what D&R sells. It is the same setup that I have and yes it's a little sloppy on the way up and that's fine. It looks as if your base plate is bent from being overstressed, as was mine. It still looks structurally sound so you can remove it from the mast and straighten it. I straightened mine by hammering it flat on an anvil. When you go to straightening it you will realize that it's actually pretty strong.

A Hobie Cat mast just sits in a divot that's maybe 1/2 inch deep and freely rotates. The only thing that holds it in place are the shrouds.

[hectoretc]

Agreeing yet again with everything stated above. I purchased and installed a tabernacle this summer from D&R after my first successful, but very stressful experience of levitating the mast verically like balancing a pool cue in the palm of your hand trying to lower it into the cuddy blowhole by myself. No wind that day, and simply could not imagine trying it in any kind of sidewind. There can't be too much worse of a sinking feeling than watching the mast tip beyond your ability to control it, and hoping there isn't anything in that 25 foot radius of your boat that is going to be expensive to replace, let alone the mast itself. After that experience, the slop in the tabernacle hinge is a a welcome difference from the whole mast wanting to tip this way and that. Not specifically stated above, but perhaps already known/assumed is that you should insure to have the sidestays attached before you raise the mast, thereby helping to center it, the higher you raise it, and as I was instructed, it's also a very good idea to use the main or jib halyard to assist in the raising/stabilizing process to hold the mast forward until the forward tabernacle pin and headstay can be attached.

For me, the only uncomfortable part of the tabernacle process remaining is that becuase of the natural slop (or flex) built into it, when the mast is raised and vertical, you need to actually pull back on it to get the forward pin inserted into the tabernacle. It feels kind of counter stablizing to be pulling the mast back (moving toward the unstable position) to get the pin in. You have to be looking down to get the pin in with one hand while trying to pull back on the the mast with the other, but not wanting to let it go too far. Maybe I should be locking down the headstay first before inserting the pin?

I am thinking I read a post elsewhere in this forum where someone had installed some shims in the tabernacle hinge making the foward tabernacle pin "line up" when the mast is stood up. I need to re-find that to see if there was more specifics given.

[TIM WEBB]

There's been some debate about whether or not the use of the forward pin is even necessary. I haven't used it on The Red Witch for quite some time, with no adverse effects.

[K.C. Walker]

+1 for what Tim said about the front pin. I've spent a fair amount of hard sailing with that setup and no problems.

I've actually experimented with tilting the mast base and like the results without the front pin. I have made the mast stub movable like a racing setup on a full-length mast. When I have the mast stub full forward the base plate matches up with the mast plate. When I shim the mast stub back the base plate and the mast plate have a gap in the front of about 1/16 of an inch. When I put on the vang hard I get considerably more bend in the mast than when it's even.

[talbot]

If you trailer the boat on the road regularly (rather than keeping it rigged in the water or dinghy park), I would skip the forward pin. When I trailered my boat every weekend I would eventually forget to remove the foward pin when lowering the mast. The rivets shear off as if they aren't there, and you have to reinstall the tabertacle hinge on the mast and/or the tabernacle. The forward pin has no effect on holding the mast up, 'tho it might marginally increase the rigidity of the joint. (More of a concern for racers, who usually use 1-piece tapererd masts.)

If you moor the boat, go ahead and install the pin. You won't have to worry about it for six months, and if you forget in September and rip the tabernacle hinge out of the spar . . . . well, you've got all winter to fix it.

[DavidF]

Thanks for all of the great feedback. It is good to have a better idea of what to expect from the hinge setup.

I think that mine is a bit more wobbly than it could be due to the bent plates and the looseness of the screws holding the plates to the mast sections.

I will try hammering the plates flat again and re-attaching them more securely. (at least some time before next spring...)

David.