Tabarnacle

[Stef]

Can I just unscrew the 4 bolts? Will the back (nuts or plate) stay secure underneath so I can reseal?

[Pete]

Yes. I've done it on a regular basis. Remove, add new goo, and reinstall. Really don't want to have to do the mast step repair.

[Mark Rode]

Just did mine yesterday. No issues. Unbolt, clean threads, clean base, reseal, tighten bolts.

[AJ Oliver]

Yup, that is one item you probably want to attend to every year. Don't want water getting in there - which it did on my boat (#445).
If compression is going on (which means you've had water intrusion), you'll see cracks appearing in the gelcoat around the tabernacle plate.

[Stef]

Thanks guys.
I removed the tabernacle, it is ever so slightly depressed, less than 1/16". Seems to be normal given it's 1982? No cracks in gelcoat around the mast. Is there more wood core under the tabernacle?

[Pete]

Mine also has a slight amount of "crush". Seen others that look similar. Tested mine with a moisture meter and the previous owner even drilled a few smal test holes. Everything came up dry so I don't worry about it other than to remove and reseal the bolts annually. Not sure if there's wood in there or not but just about anything used at that time, I would think, will suffer some amount of compression.

[AJ Oliver]

to Pete & Stef -
Under the tabernackle there is (or was on #445 until I did a reconstruct), first, gelcoat, second, filler type stuff (similar to what's in the dagger board), third, a layer of plywood (this is I think usually the problem area. it gets wet), fourth, more filler, fifth, a 1/8th inch aluminum plate, sixth, the wood support at the front of the dagger board trunk. (I sort of forget - could have layers 2 and 4 reversed.)
The stainless tabernacle bolts go down through the aluminum plate - which, combined with a little water, leads to corrosion. I had a good quart of aluminum oxide (I think it's called) powder down there.
I may have been too hasty in doing a complete rebuild (see the posts elsewhere on what we did). If you tension your shrouds for sailing, and they don't lose tension in a few weeks, you probably do not have a problem.
If the tabernackle bolts do not tighten very well, it could just mean that the threads on the aluminum plate are stripped. That in and of itself I do not think is a problem - there is enough downward pressure on the mast that it's unlikely that the tabernackle will start to shift position.
Actually lots of 7.9's have water issues below the downhaul block just in front of the tabernackle. Mine did. If you fix one, might as well do the other.
Be careful on the reconstruct if you do it. The plywood is tapered - thinner toward the back of the boat. measure carefully and often. But overall, it's not too hard to do - especially if you are storing indoors for the winter, and have some time to work on it (ie, are retired like me).
Hope this helps. Feel free to contact me with questions. Sorry if the merlot I just drank caused some typos . .

[Doug Frye]

Aluminum Plate on newer boats BUT rusty steel plate on my 1982 vintage boat.

After digging through goo to rusty steel plate (really rusty....not just some surface rust) Big rusty flakes peeling off...did I say flakes? Thin chunks was more like it.
Took out remains of steel plate, ordered similar thickness strong aircraft aluminum plate from McMaster-Carr...drilled and tapped holes to bolt tabarnacle to and replaced the sandwich
under fiberglass skin that I saved. Roto-Zip through top skin and gently pry up.

[Doug Frye]

Under Robyn (hull #177) tabernacle looked like these before photo's:


Replaced with section cut from (.250) 1/4" x 12" x 12" Aluminum Plate (below) from McMaster-Carr.

Corrosion-Resistant High-Strength Aluminum (Alloy 7075)

Exceptionally strong but still lightweight, this aircraft alloy has better corrosion resistance than Alloy 2024 due to the addition of zinc. Originally developed for aircraft frames, it is also used for keys, gears, and other high-stress parts. Heat treatable. Nonmagnetic.

Has held up fine for 5 years of hard racing so far.


Doug

[Doug Frye]

One last photo from the S2 7.9 Forensic Pathology Archives.

[AJ Oliver]

Dear Stef & Pete -
The slight crush that you've noticed under the tabernackle may be caused by point loading of the half moon mast base on the tabernackle. On #445 we moticed that the tab was deformed (pushed down) under the mast base - with about a 1/16th inch dent. We solved it last winter (I think/hope) by welding an extra 1/8th inch stainless plate on top of the tab where the base rests. Seems to be working.
Seems to me that if the tabernackle is deformed, you likely have point loading going on - which you don't want.
If you want a picture, let me know and I'll send you one . .
Fair Winds, AJ (Skip) Oliver
Sandusky Sailing Club