Epoxy and stainless steel.

NYSail

NYSail

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Jan 6, 2006
3,137
Beneteau 423 Mt. Sinai, NY
So have a project to do with epoxying a threaded coupling to fiberglass. A male npt / 5/8 nipple will be screwed in for a 5/8 hose to be attached. Is the adhesion between the stainless and epoxy strong alone when done correctly? I do intend to put a couple wraps of cloth at the base as well.

thanks
Greg
 
Ralph Johnstone

Ralph Johnstone

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Jan 4, 2006
7,219
Hunter 310 West Vancouver, B.C.
Not too clear what this is for and what is required as far as strength, impact resistance, water tight seal, above water, below water. What the hell is this going to be ? Maybe just a little bit illegal perhaps ? Verrrrrry interesting. :shhh: Don't keep us in suspense.

Piling up FG around the 1/2" coupling will not be very strong. Perhaps bolting a small SS 1/2" FIP threaded flange to the FG would increase the strength for the nipple. Without more details, I'm down for the count.
 
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NYSail

NYSail

.
Jan 6, 2006
3,137
Beneteau 423 Mt. Sinai, NY
Ha yes very vague indeed. Beneteau has a water feed to the shaft tube which is made of fiberglass. The water is necessary for the volvo dripless shaft seal. They had a bronze fitting tapped into it with only a couple threads at best, then had a wad of epoxy surrounding it. Was water tight and it’s in a place that is relatively safe from impact, however fitting complete corroded. Yes it is below the water line. I have a small peice of 1/4 inch thick fiberglass that I will drill a hole into and set the stainless steal fitting in,, then plan to expoxy that onto the tube. The picture is of the cleaned up hole that the fitting will sit on top of.

greg

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D

dlochner

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Jan 11, 2014
12,803
Sabre 362 113 Fair Haven, NY
A stronger solution would be glass in the threaded part of the fitting. There will be more surface area. Check the West System website for info on casting threads.
 
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Bob S

Bob S

.
Sep 27, 2007
1,800
Beneteau 393 New Bedford, MA
Greg,
I was thinking of doing the same upgrade but thought of taping a piece of G10 and epoxying it in place. The G10 should be plenty strong to thread a NPT fitting into it.
 
NYSail

NYSail

.
Jan 6, 2006
3,137
Beneteau 423 Mt. Sinai, NY
So I did a test with just the threaded joint epoxied only at the base……. Let it cure for 15 hours and it is very attached. I screwed the nipple in and torqued it and the thing didn’t budge. So I think with the extra that I am doing which includes a couple wraps of cloth should be more than adequate.
Thanks for the tips!

Greg
 
DougM

DougM

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Jul 24, 2005
2,242
Beneteau 323 Manistee, MI
NYSail said:
So have a project to do with epoxying a threaded coupling to fiberglass. A male npt / 5/8 nipple will be screwed in for a 5/8 hose to be attached. Is the adhesion between the stainless and epoxy strong alone when done correctly? I do intend to put a couple wraps of cloth at the base as well.

thanks
Greg
Click to expand
That’s an Achilles heel in the Beneteaus…
the epoxy buildup will work because there isn’t much water pressure there. The danger is that it is relatively weak and the fitting can easily snap off if it is accidentally bumped.
Bear in mind that, unfortunately, the original fitting is brass, and subject to saltwater corrosion. It should be bronze. Others have had little luck in locating a bronze replacement.
A supplier like McMaster Carr may be a source. I know Annapolis Yacht Sales sold replacement fittings, but they were still brass as far as I know.
 
NYSail

NYSail

.
Jan 6, 2006
3,137
Beneteau 423 Mt. Sinai, NY
DougM said:
That’s an Achilles heel in the Beneteaus…
the epoxy buildup will work because there isn’t much water pressure there. The danger is that it is relatively weak and the fitting can easily snap off if it is accidentally bumped.
Bear in mind that, unfortunately, the original fitting is brass, and subject to saltwater corrosion. It should be bronze. Others have had little luck in locating a bronze replacement.
A supplier like McMaster Carr may be a source. I know Annapolis Yacht Sales sold replacement fittings, but they were still brass as far as I know.
Click to expand
yes indeed…… mine was completely corroded. When I went to remove the remaining peice it crumbled. I am going to use stainless steel as a replacement (see above photo). When done it will be quite robust.

Greg
 
thinwater

thinwater

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Mar 26, 2011
3,687
Corsair F-24 MK I Deale, MD
How do you suppose threaded fittings are added to commercial fiberglass tanks (none of these suggestions are it)?

Buy a threaded FRP coupling and glass that in. Also, you don't use cloth (not flexible enough), you use mat. Since most mat is not epoxy-soluable, deconstructed 1708 or similar is common.
 
S

senang

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Oct 21, 2009
316
hunter 38 Monaco
By the look of it this a standard Volvo lipseal. Volvo does NOT mention this arrangement with the water hose. I have installed this volvo lipseal in our boat a couple of years ago without this hose. Volvo DOES insist that you “burp” the seal, that is compress the bottom upwards to create a leak between shaft and seal. You have to do this after a haul out to let the air out of the shaft box, so the outer lipseal gets lubricated and cooled with water. For the inner lipseal you have to introduce a small amount of waterresistant grease once a year. It is pretty maintenance free.
I suppose Beneteau (Edit: sorry I mentioned Volvo here) made this arrangement to mitigate for owners not applying the Volvo instructions.
 
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MikeHoncho

MikeHoncho

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Dec 28, 2015
1,897
Laser, Hunter H30 Cherubini Tacoma
I think I would consider placing a helicoil in the fiberglass and thread the threaded/barbed figure to it.
 
NYSail

NYSail

.
Jan 6, 2006
3,137
Beneteau 423 Mt. Sinai, NY
senang said:
By the look of it this a standard Volvo lipseal. Volvo does NOT mention this arrangement with the water hose. I have installed this volvo lipseal in our boat a couple of years ago without this hose. Volvo DOES insist that you “burp” the seal, that is compress the bottom upwards to create a leak between shaft and seal. You have to do this after a haul out to let the air out of the shaft box, so the outer lipseal gets lubricated and cooled with water. For the inner lipseal you have to introduce a small amount of waterresistant grease once a year. It is pretty maintenance free.
I suppose Beneteau (Edit: sorry I mentioned Volvo here) made this arrangement to mitigate for owners not applying the Volvo instructions.
Click to expand
I burp and lightly grease every year. Maybe volvo doesn’t mention it because every set up is different. Beneteau has a fairly long shaft tube with a cutlass on the end that does not allow significant water to back flow up into the shaft tube to cool things down. No cutlass strut.

The set up so far the way it is designed works flawlessly.

greg
 
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