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Old 19-08-2010, 21:59   #1
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Threaded SS Backing Plates Epoxied in Place ?

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,


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Old 19-08-2010, 23:33   #2
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Excellent idea, go for it . . .
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Old 20-08-2010, 02:10   #3
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Nut welding...

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.
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Old 20-08-2010, 02:59   #4
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Originally Posted by SvenG View Post
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.

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Old 20-08-2010, 05:13   #5
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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.
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Old 20-08-2010, 06:07   #6
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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!
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Old 20-08-2010, 06:11   #7
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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.
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Old 20-08-2010, 08:43   #8
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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.



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Old 20-08-2010, 10:14   #9
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threaded plates

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.
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Old 20-08-2010, 10:31   #10
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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,



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Old 20-08-2010, 14:37   #11
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Excellent answer.
Did you look that up in some table or do you just know it ?
How could it possibly matter?
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Old 20-08-2010, 14:47   #12
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Gord,

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How could it possibly matter?
It has to do with "give a man a fish" vs. "teach a man to fish". I'll leave the rest of the assignment up to you



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Old 20-08-2010, 14:51   #13
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Gord,



It has to do with "give a man a fish" vs. "teach a man to fish". I'll leave the rest of the assignment up to you
Wait...I know this one! "Give a man a fish, he'll eat for a day... Teach a man to fish, and he'll sit on a boat and drink beer all day..." I'm sure Gord knows this already!

Einstein claimed never to memorize anything which could be looked up in less than two minutes.
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Old 20-08-2010, 15:35   #14
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... Einstein claimed never to memorize anything which could be looked up in less than two minutes.
As Christian suggests; It has nothing to do with "give a man a fish" vs. "teach a man to fish".
In the modern information age; it may relate more closely to “give a man the wherewithal to purchase acquire a fish”.
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Old 20-08-2010, 15:39   #15
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As Christian suggests; It has nothing to do with "give a man a fish" vs. "teach a man to fish".
In the modern information age; it may relate more closely to “give a man the wherewithal to purchase acquire a fish”.
And if Einstein lived today he wouldn't even memorize his own name.



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