Mast/tabernacle repair

[Vanalien]

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:


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:


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?

[GreenLake]

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

[RaleighRancher]

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:
Oblique view of aft edge of tabernacle:
Forward edge of tabernacle (no bend):

[GreenLake]

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.

[RaleighRancher]

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.

[RaleighRancher]

Following up on my issue with the tabernacle:
Prior to my tabernacle getting bent as noted above, the clevis pins had been hard to insert. Last weekend I raised the mast and absolutely could not get the second pin through. On closer examination, I realized that both of my tabernacle plates are slightly off of 90 degrees from the mast. The result is that the tabernacle plates don't align well when raising the mast. It looks like this is from a combination of two issues when I repaired the mast two years ago:
1. the cuts deviate from 90 degrees by maybe half a millimeter.
2. the holes i drilled for the screws walked just a tiny bit on entering the mast step casting.

It seems to fix these two issues I need to cut about 3/4 inch off the top end of the mast stub and the bottom end of the long upper mast portion. And make sure I can get the cut dead straight and drill the holes with no walking. Then I'll need to add about 1-1/2 inch shim to the cuddy floor where the mast rests. Sheesh.

Perils, pitfalls, advice?

[tomodda]

Sorry to hear (read) that you're having so many problems with the tabernacle. It's truly the "Achilles Heel" of our wonderful boats, if that one part isn't working right, you're dead in the water. So you've asked for ideas and suggestions, here's off the top of my head:

-How are you cutting the aluminum mast? I'll assume a cutting disk on an angle grinder. Build yourself a jig (2x4 wood is fine) to keep everything aligned. Put the two pieces of mast side-by-side, making sure they are absolutely parallel, then cut, ideally with some mechanism to make sure you keep the blade at 90 degrees. Something like this:

https://youtu.be/_e7HDp9AMP8?t=747

and here's how to make it:

https://youtu.be/_e7HDp9AMP8?t=680

By the way, that is (IMHO) an excellent woodworking channel. Japanese guy full of brilliant ideas.

-Get a "Center Punch" to start your screw holes, they've very cheap and save you from drifting drill bits. If you are uncertain of our ability to drill at 90 degrees, there are all sorts of tricks to help you out. Personally, use and old CD as a drill guide (you can check you angle via the reflection), but do some googling to see what method works best for you.

-Make sure your screw hole is the size of the INNER diameter of your screws (bottom of the threads), not the total diameter. You can easily tap the hole with a Harbor Freight tap and die kit. But if you use stainless steel screws (and you should!) then it will self-tap, i.e. cut it's own grooves into the aluminum mast. Go slowly, carefully, and use some tapping oil (lubricant).

-Do you really have to cut an entire 0.75 inch on both sides? If you're only off by a few mm? Or is this because of your bad screw holes? I'd almost be tempted to redrill and then tap a larger hole into your tabernacle plug, but you'll need a drill press for that....

-Are you in Raleigh, NC? (From your onscreen handle)? If so, I'm in Durham, near downtown and lucky you, I have a spare, broken mast. You're welcome to come by, cut off a length of my mast and use it as the bottom part of your rig (base of the mast, from keelson to tabernacle). Likewise, I have a spare two-pin tabernacle floating around in my "junk drawer," you're welcome to it. I also have a fairly OK drill press, and we can see if the mast plugs from my old mast will help you. Also have a compound miter saw, so if you can source a metal cut-off blade for a chop saw (Dewalt makes one), that solves your 90-degree cutting problem. Anyway, if you're nearby and willing to run over to Durham - bring your entire mast or boat if you want - I'm happy to help out. Private message me.

[RaleighRancher]

These are all really helpful suggestions. I did purchase a metal cutting blade for my miter saw. Hadn't thought about butting the two pieces together to ensure a congruent cut. Seems obvious now.

You infer correctly I'm in Raleigh. You are very generous to offer your time and spare parts! I'll pm you! Thanks.

[GreenLake]

Definitely think twice before shortening your mast.

[tomodda]

Exactly. Stay length is the problem, you have got to get the correct tension. And that's the reason I think Mr Raleigh is better off taking a piece off my broken mast, rigging that as the bottom part of his tabernacle setup, and then cutting the bare minimum off his upper mast. We're working on doing a meetup and let's see if we can't put together an intelligent solution to his mast problem.