Threaded SS Backing Plates Epoxied in Place ?

[SvenG]

Some of our stanchions need re-bedding ... wow, isn't that unusual !?

Since it is a pain to get to the underside I'm considering cutting SS backing plates and thread them for screws. I'd install them and then put some epoxy or roving over them so that they would stay in place even if the screws are removed topside.

While it would be a bit costly, it sure would be nice to be able to re-bed in the future without having to remove headliner or interior trim. The plates could also be oversized to better distribute stanchion loads.

Thoughts ?

Thanks,


-Sven

[PAR]

Excellent idea, go for it . . .

[Boracay]

Depending on the level of technology available would it be possible to weld ss nuts on the underside of the plates?

If I were doing it I'd be tempted to use a quality polyurethane mastic under the plates and maybe a butyl (or something removable) mastic under the stanchion plates. Just to allow a bit of movement from time to time.

[mbianka]

Originally Posted by SvenG

Some of our stanchions need re-bedding ... wow, isn't that unusual !?

Since it is a pain to get to the underside I'm considering cutting SS backing plates and thread them for screws. I'd install them and then put some epoxy or roving over them so that they would stay in place even if the screws are removed topside.

-Sven

Sven:

Be careful and ask yourself why the boat manufacturers did not do this to start with? I just recently installed some deck hardware for a solar dodger project. I predrilled backing plates to fit the outline of the deck hardware stanchions. When I tried to put the screws through them they sometimes did not line up because of the curvature of the deck. You may find the some problem with your threaded backing plate.

Capt. Mike
THE BIANKA LOG BLOG

[PAR]

My only concern about threaded backing plates, as suggested here would be the fasteners galling up in the backing plates, which you can address during installation with anti seize. Naturally, you'll want to make some templates of the plates, but manufactures don't do it because it costs more. Make the plates thick to accept enough threads to be effective.

[Christian Van H]

Originally Posted by PAR

My only concern about threaded backing plates, as suggested here would be the fasteners galling up in the backing plates, which you can address during installation with anti seize.

Tef-Gel please, and please think about using butyl as the sealant... You wont work on them again in this lifetime!

[Blue Stocking]

Countersink the glass deck before putting the bases down. Build a litte cone of sealer around the bolt or screw. This will compress into the countersink and cure to a compessed 0-ring. Any caulk that squeezes up thru the screw hole helps to seal the base from above.
My Cheoy "leakey" is back to being a "Lee"
I also sometimes wrap a machine screw thread with Teflon tape. Helps the sealing and appears to prevent galling.

[SvenG]

Yes on the butyl and yes on the "Mainsail" countersink for sealing. I do use tefgel whenever we screw anything into metal. (Butyl lasts for a week under fingernails !)

Would coarse or fine screw threads be best if I want to reduce the plate thickness ? I'm guessing that 3/8" SS would be just about right strength-wise but don't know if that would allow for enough threads ?

Thanks for all the inputs.



-Sven

[double diamond]

If the material of the fastener and the threaded plates have similar tensile strength, 5 threads engagement gives the full strength of the fastener. Fine pitch threads are stronger, because the minor dia. is larger, and that is the area that fails first. Example: 3/8-16 thread, 5/16" plate gives 5 threads.
Andy

[SvenG]

Originally Posted by double diamond

If the material of the fastener and the threaded plates have similar tensile strength, 5 threads engagement gives the full strength of the fastener. Fine pitch threads are stronger, because the minor dia. is larger, and that is the area that fails first. Example: 3/8-16 thread, 5/16" plate gives 5 threads.
Andy

Excellent answer.

Did you look that up in some table or do you just know it ?

Thanks,



-Sven

[GordMay]

Originally Posted by SvenG

Excellent answer.
Did you look that up in some table or do you just know it ?

How could it possibly matter?

[Maine Sail]

Originally Posted by SvenG

Yes on the butyl and yes on the "Mainsail" countersink for sealing. I do use tefgel whenever we screw anything into metal. (Butyl lasts for a week under fingernails !)

Sven,

As much as I like to take credit for the "countersink" method I learned it from a guy I knew at Hinckley back in the 80's. Morris Yachts also uses this method..

Here's an M-36 being countersunk for Dorades..

[brankin]

When I installed my stanchions, I cut 2"x3/4"x1/4" stainless bar and welded the 14/20 nut on the plate and then over-sized the entry side hole and re-tapped the nut. During installation, it was a real mess. I would coat the nut plate with 5200 and then have my helper install the bolt. Most of the nut plates had to be put in place by feel. In the end, it was well worth the effort. I have removed and replaced several bolts and the nut plates stayed in place so that I could reinstall the bolt by myself from the exterior