Mast/tabernacle repair

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Mast/tabernacle repair

Postby Vanalien » Tue Aug 04, 2020 10:15 pm

Yesterday in a light breeze my starboard stay let loose and the mast toppled into the water. The damage seems slight:
1) the tabernacle plate the mast attaches to is bent:
2760

2) the rivets on the sides of the mast (holding the mast to the base) sheared off cleanly, but the rivet at the front of the mast base tore through the mast to the bottom of the mast:
2761

Will it be safe to straighten the tabernacle piece by squeezing it in a vise?

How can I repair the base of the mast? Will it work to wrap a piece of metal around the mast and rivet through that?
Or will I have to cut off the mast? If I shorten the mast, I assume I would need to move the tangs the the upper end of the stays attach to further up the mast... I would think that would be cheaper and easier than procuring shorter stays.

What is best? What is cheapest yet still safe?
Steve
"Nellie Ruth" - 1985 DS2 Anniversary Edition #12819
Little Canada, MN
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Re: Mast/tabernacle repair

Postby GreenLake » Wed Aug 05, 2020 8:21 pm

Bad luck, that! But looks like things are fixable.

You can just drill a new hole for a rivet, a bit offset from the one that tore out. (Or two, one on either side).

These rivets only keep the casting from falling off and while it's being raised. When the mast is used, it's under compression, and as long as the bottom end of the mast section still fits snugly around the casting, the rivets have nothing to do.

If you succeed in straightening the hinge, all is fine (like the rivets, most of its work is done while raising the mast). If you can't get it straight enough, get a replacement from DR Marine. But only then :)
~ green ~ lake ~ ~
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Re: Mast/tabernacle repair

Postby RaleighRancher » Wed Nov 01, 2023 11:10 am

My question seems close enough to the original topic here:
How easily do the tabernacle plates bend?

Boat is a 1982 DS2. I replaced the tabernacle about 1 year ago (due to trailering the boat, with raised mast, into a tree branch; you can read about the other repairs that required herehttps://forum.daysailer.org/forum/viewtopic.php?f=11&t=6716). The replacement tabernacle was brand new from D&R and quite a bit beefier than the old. Have had no incidents since then - all smooth sailing and launches.

Two weeks ago, I noticed the aft edge of the lower tabernacle plate is bent, as if that edge alone took a hard downward load. I can still insert the forward clevis pin, but it's very tight/very high friction on the pin.

Any ideas on what I might've done to cause this? Insufficient forestay tension? Something about the way I'm raising the mast?
Aft edge of the tabernacle: 3152
Oblique view of aft edge of tabernacle: 3153
Forward edge of tabernacle (no bend): 3154
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Re: Mast/tabernacle repair

Postby GreenLake » Wed Nov 01, 2023 4:43 pm

What struck me from your pictures is that the tabernacle appears quite a bit wider than the mast profile. Any overhang provides a lever arm which is exposed to the full force of the shrouds. Rig tension is a few hundred # combined, which is not insignificant. However, you'd expect top and bottom to have similar deformations.

Is your rig overly tight?

The leeward shroud should be slack at 10kt or above. Another test is that you should be able to (just) hear a note when plucking the shroud. If too slack it will sound more like a rattle.

I'm not overly familiar with tabernacles so there may be something I missed. But I would want to rule out an overly tight rig.
~ green ~ lake ~ ~
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Re: Mast/tabernacle repair

Postby RaleighRancher » Wed Nov 01, 2023 11:14 pm

Thanks, greenlake. You are a fount of knowledge on these boats!

I did notice that the replacement tabernacle was significantly wider than the one it replaced, but had not recognized the added leverage that created. Perhaps i will look into replacing the top and bottom plates (keeping the castings they are bolted to). I'll check with D&R about proper width too.

As for rig tension, I'm still learning. On my last two outings I was watching to make sure the leeward shroud went slack, but it's quite possible I ran them too tight a time or two over the summer. I can see where the added leverage and excessive tension could create the issue.
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