Backing plate material for stanchions

benajah · #1 (**permalink**) 05-29-2011

Hi all, I did a search but didn't come up with anything. I need to fix a loose stanchion and not sure of the best material to use as a backing plate. The existing backing plate is really small, about four and a half square inches and i want to put something bigger. I have some 16ga sheet steel, some plywood also, but wanted to see if there are better materials to use.

BELLATRIX1965 · #2 (**permalink**) 05-29-2011

I'm afraid sheet metal will not do much for you under stanchions! I buy 1/8" thick stainless steel from the "scrap" bin at a local machine shop (cheap!) and make my own custom backing plates. Just be sure to use bi-metal saw blades and cobalt drill bits, or you will get frustrated trying to cut it!

pdqaltair · #3 (**permalink**) 05-29-2011

While SS is certainly good stuff, your going to find 1/8" aluminum MUCH easier to work with and sufficient for your needs. Corrosion is only an issue if you have way too much leakage. Sheet metal shops and sign stores should have scraps. FRP is also a good material; 1/4" is a good general purpose thickness.

If you aren't into scrounging scraps, McMaster Carr has everything.

olson34 · #4 (**permalink**) 05-29-2011

Use a 3/8" in plate of G10/FR4 plate.
McMaster-Carr

Something about 6 X 9 inches, or whatever will fit well. Moosh it into place with thickened epoxy. Redrill the holes oversize in the deck, fill with thickened epoxy, redrill for the bolts.

Bed the base in your choice of marine goo, and you're good to go... for another 20 years... plus.

mitiempo · #5 (**permalink**) 05-29-2011

I agree with olson34. And when you re-drill after potting the deck holes you can tap the holes for the bolts easily as well. If the holes are tapped between the deck and 3/8" G10 you almost don't need the nuts but I would certainly use them as well.

benajah · #6 (**permalink**) 05-30-2011

Thanks for the suggestions. My friend, who has not a lot of experience on boats went sailing with me on Saturday. He is a big dude, 230 or do, and I didn't think to brief him on how to get on and off a boat and he just grabbed a stanchion to climb on and wrenched the he'll out of it, pulling the bolts loose, the outboard ones are pulled out a good 1/8 inch.
Which raises another concern. My boat is a Cal 2-27 and I haven't messed with the stanchions yet, will try to work on it tomorrow, but it seems to me that if they pulled out that far....were they installed with a backing plate? I can't see the fitting now because there is a cosmetic shell over it that is the size I mentioned before.
I'm worried about what I am going to find when I get everything exposed. Oh the joys of boat maintenance.
At least if this happens to be a weakness I can go through and rebid and redo all of them before I run into problems in the future. Good to know beforehand.

studentt · #7 (**permalink**) 05-30-2011

I would advise NOT using plywood as a backing plate material for your stanchions. If a leak does develop, you may be depending on mush to hold your stanchions in place.

SlowButSteady · #8 (**permalink**) 05-30-2011

Quote:

Originally Posted by studentt

I would advise NOT using plywood as a backing plate material for your stanchions. If a leak does develop, you may be depending on mush to hold your stanchions in place.

Plywood backers should have 2 or 3 coats of thinned epoxy (applied to the bolt holes as well) to prevent this from happening.

My '75 Cal 2-27 originally (so far as I can tell) had no backers on any of the deck hardware. Unless you have tons of karma racked up, and the nuts on the bolts were just loose, for a stanchion bolt to pull out like that your boat almost certainly has some rotten core. The good news is that 2-27 decks were all plywood cored (again, so far as I can tell), so the rot may not have spread very far.

mitiempo · #9 (**permalink**) 05-30-2011

Plywood core spreads wet and eventually rot farther than balsa will. The balsa is end grain where the plywood has a laminar structure and the moisture will spread through it quickly.

SlowButSteady · #10 (**permalink**) 05-31-2011

Quote:

Originally Posted by mitiempo

Plywood core spreads wet and eventually rot farther than balsa will. The balsa is end grain where the plywood has a laminar structure and the moisture will spread through it quickly.

That makes sense, but I've seen a couple of cases where moisture/rot didn't spread very far in plywood (however, those may have just been anomalies).