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Old 31-05-2019, 13:45   #16
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Re: Gelcoat over aluminum over fiberglass in head - how?

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Originally Posted by rls8r View Post
tapping the FRP .
It is pretty easy to make sloppy threads when doing this by hand. And then it will be no-where near as secure as excellent straight/tight threads.

One issue is wobble when drilling the hole by hand. Using a small portable drill press frame, or a drilling guide (like a tallish block of wood with a hole pre-drilled in it) is useful - stops the drill from wobbling.

And then similarily wobble when tapping.

use the correct recommended drill size for the tap, if you can't get then the next smaller size you have available.

Sorry, you probably already know all this - but a reminder can't hurt.
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Old 31-05-2019, 18:45   #17
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Re: Gelcoat over aluminum over fiberglass in head - how?

I agree forget the aluminum. You will constantly be fighting blisters and flaking paint. G-10 is the answer 1/4” is fine. Get 3 ss bolts for blind areas. Cut off the little tabs that stick up for wood applications. Epoxy then in place. You can actually allow the bolts to protrude a little beyond the bottom of the nuts into a recess so you are getting grip with something other than the tip of the bolts. I would put the Prefinished G-10 down with 4 ss sheet meta screws and some 3M 4200..done deal.
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Old 31-05-2019, 21:14   #18
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Re: Gelcoat over aluminum over fiberglass in head - how?

Bond the bolts in oversized holes with thickened epoxy. West System manuals explain the method.
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Old 01-06-2019, 00:25   #19
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Re: Gelcoat over aluminum over fiberglass in head - how?

If you have room under the floor to through bolt, that is your best option.

As many have said, forget aluminum.

A picture showing the installation site would be nice.

If you have room between the mounting surface and the hull, an oversize hole can be drilled, and then any of a variety of either homemade or store-bought toggles can be inserted lengthwise (or folded) and then prevented from rotating whilst being tightened either mechanically or with glue.

If you are mounting the toilet so that the vertical back surface is flush or close to a bulkhead or hull side, a bracket could be fabricated that extends from the lid hinge bolts (on the underside of course) to an L-bracket epoxied or bolted to the bulkhead or hullside, thus giving you rigidity in an additional plane.
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Old 01-06-2019, 06:08   #20
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Re: Gelcoat over aluminum over fiberglass in head - how?

Jim - I have tried to upload an image of the head as it was a while ago. I've made some improvements since then. Nevertheless, you can see the raised FRP platform on which the toilet will sit. The darkened square is where the old W-C Skipper toilet sat. I cannot access below the raised platform without major surgery to the head - so I'd prefer another approach.

It still seems to me that the way to go is to drill and tap directly into the FRP since it's >1.5x the thickness of a #14 bolt. I hear Breaking Waves' caution about sloppy drilling and tapping. Perhaps the way to go is to take Copacabana's notion of the installation being like a thru-hull backing plate and installing studs into the FRP using the epoxy procedure that Rod Collins describes at https://marinehowto.com/seacock-backing-plates/ for installing bolts into backing plates. Hopefully, that will address any 'sloppyness' issues. I can get silicon bronze fasteners at Fawcetts.

Once again - thanks all. This thread has not only given me better ideas about installing the toilet - but ideas about how to approach a number of repair jobs that I'm facing.

20181024_090524.jpg
Sorry - the preview shows this a being rotated 90° CCW and I don't know how to un-rotate it.
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Old 01-06-2019, 06:34   #21
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Re: Gelcoat over aluminum over fiberglass in head - how?

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It still seems to me that the way to go is to drill and tap directly into the FRP since it's >1.5x the thickness of a #14 bolt. I hear Breaking Waves' caution about sloppy drilling and tapping.
I did not mean to scare you off on the tapping, just to offer a caution to be extra slow and careful and precise. Jedi is right, with 1/2" base, it is the most straightforward approach here.

The one advantage of the threaded inserts is that while the (internal) threads are exact, they are more tollerent to slightly sloppy work as the hole you put them in can be a little sloppy because you can set the inserts in loctite or epoxy (while the bolts are still freely removable).

Just be precise/careful and any of these procedures will work fine for this job.
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Old 01-06-2019, 07:33   #22
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Re: Gelcoat over aluminum over fiberglass in head - how?

Are you sure the base is solid fiberglass and not glass over plywood? In the case of the latter, tapping threads won't be very effective. I'd be surprised if it was solid glass.
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Old 01-06-2019, 15:31   #23
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Re: Gelcoat over aluminum over fiberglass in head - how?

Quote:
Originally Posted by rls8r View Post
Jim - I have tried to upload an image of the head as it was a while ago. I've made some improvements since then. Nevertheless, you can see the raised FRP platform on which the toilet will sit. The darkened square is where the old W-C Skipper toilet sat. I cannot access below the raised platform without major surgery to the head - so I'd prefer another approach.

It still seems to me that the way to go is to drill and tap directly into the FRP since it's >1.5x the thickness of a #14 bolt. I hear Breaking Waves' caution about sloppy drilling and tapping. Perhaps the way to go is to take Copacabana's notion of the installation being like a thru-hull backing plate and installing studs into the FRP using the epoxy procedure that Rod Collins describes at https://marinehowto.com/seacock-backing-plates/ for installing bolts into backing plates. Hopefully, that will address any 'sloppyness' issues. I can get silicon bronze fasteners at Fawcetts.

Once again - thanks all. This thread has not only given me better ideas about installing the toilet - but ideas about how to approach a number of repair jobs that I'm facing.

20181024_090524.jpg
Sorry - the preview shows this a being rotated 90° CCW and I don't know how to un-rotate it.

You can't rotate pictures after they've been loaded. I rotate them using 'paint'; I assume there are other methods as well.

Even though the thickness of the glass fits in the 'thread/thickness ratio rule', typical production boat layups may or may not be substantial enough to ensure you have a good thread holding ability.

If the floor is really only glass, with no wood for a screw to hold into, then a stainless toggle like this can be installed from the top; you have to drill a slightly oversize hole, but this will be covered by the L-bracket and the toilet.




If you can find a supplier, these are available in stainless and use the same size hole as the fastener.



If you actually have at least 1/2" plywood under the glass (for me 3/4" would be a minimum), and it is in good shape you can use a stainless hanger bolt like this.



but of course a regular stainless lag screw would serve as well--as long as you didn't have to remove it to many times.

If you go this route, a hanger bolt, with the proper diameter pilot hole screwed in with epoxy has a lot going for it and might be the best compromise...
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Old 01-06-2019, 15:34   #24
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Re: Gelcoat over aluminum over fiberglass in head - how?

It's 1/2" of fiberglass. I can see down the 1/2" diameter bolt holes used to hold the previous toilet down. As I understand things, my boat is one of the early fiberglass boats - so I think that they went overboard with the thickness of fiberglass since they really weren't sure of the strength.
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Old 01-06-2019, 16:05   #25
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Re: Gelcoat over aluminum over fiberglass in head - how?

Thinking out loud...
Perhaps a bit of Corian (instead of aluminum or G10) to serve as a base for the new Elegance would allow a pleasant looking spacer that could be cut a little larger to cover things up??
I don't know about the mechanicals of Corian though I'm thinking that Corian is easy enough to keep hygienic while otherwise not offering a corrosion concern.
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Old 01-06-2019, 18:04   #26
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Re: Gelcoat over aluminum over fiberglass in head - how?

Now have I got it right way up!!
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Old 01-06-2019, 21:05   #27
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Re: Gelcoat over aluminum over fiberglass in head - how?

Coopec, if you have actually drilled through the fixture and determined tht it is indeed solid glass 1/2 inch thick, then disregard this worry!

But that installation sure looks like it is ply with glass over it. the sharp corner where the vertical and horizontal surfaces meet isn't how most folks would shape an all-glass moulding. I reckon it is worth your while to check and be really sure.

Another thought: looks like there is enough vertical clearance that you could cut an access port in the vertical panel and get your hand in... and then through bolting becomes possible. Our previous boat was designed thus...

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Old 01-06-2019, 21:53   #28
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Re: Gelcoat over aluminum over fiberglass in head - how?

Perhaps the OP is unaware as are many, that the bolts are just lab bolts, holding the head down.


I'd just clean up what he has, cover or fill the holes, line up the new head, and drill for the lag bolts.


Am I missing something? Or is it the wood under the open hole, hard to see. If so, glass over, could even forget gelcoat and install.


If it's just dirt...
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Old 01-06-2019, 22:24   #29
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Re: Gelcoat over aluminum over fiberglass in head - how?

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Now have I got it right way up!!
What's up?
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