3/4" Skin Fittings Holes Cut too Large...........Options???

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thesaintlyone

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So in the process of removing the seacocks I cut out some very difficult to remove skin fittings using a holesaw just slightly larger than skin fitting itself. Three in Total all 3/4 " Head Sink Outlet. Galley Sink Outlet and Engine Raw Water Inlet

When I put the new 3/4" Skin Fittings in they move a little as the hole is now slightly bigger!!!!

What are my options????
 
thesaintlyone said:
So in the process of removing the seacocks I cut out some very difficult to remove skin fittings using a holesaw just slightly larger than skin fitting itself. Three in Total all 3/4 " Head Sink Outlet. Galley Sink Outlet and Engine Raw Water Inlet

When I put the new 3/4" Skin Fittings in they move a little as the hole is now slightly bigger!!!!

What are my options????
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Repair holes ( major job if done properly) and cut new holes in original positions
or
do a less than "major repair" to blank off the old holes. Cut new holes in new locations.
or
Buy larger skin fittings.
or
Use loadsa sealant!
 
Wot Vics said. If the holes are only slightly too large Id go with a little extra sealant. I generally use CT1 as it will glue the fitting in place as well as sealing it. How much play is there?
 
The fitting is held in by the nut clamping it to the hull, not by the hole itself. Quite common to have a small gap between the fitting and the hole - I always do this in my plywood boat. Just fill it with sealer and tighten the nut.
 
TBH I have tried the last option on the Galley Sink outlet it feels solid but got visions of leaking. Buying a 1" skin fitting does sound plausible can I buy the connections to take a 1" DZR ball valve down to a 12mm which is the size of the Engine Raw water Pipe.

What would be the exact size Holesaw for 1" Bronze Skin Fitting

There isnt much play maybe a mm each side plenty of flange surrounding the outside of the hole!!!
 
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Assuming the mushroom head is at least say 5mm larger on the radius than the hole then seal with sikaflex 291, but I would add a marine ply inner pad piece at least 3 x the diameter and attach this to the inner face also with ska filling the gaps, or if you really want it fully done bond in place the pad piece with GRP pre-drilled to the diameter of the fitting plus 2mm for sealant and fitting clearance.

When tightening the Sika seal just nip up gently so it is squeezing all around the fitting, but do not pull it up too tight yet. Let it set for a week then pull up firmly onto the set Sika, which will by then form a proper gasket.
 
thesaintlyone said:
So in the process of removing the seacocks I cut out some very difficult to remove skin fittings using a holesaw just slightly larger than skin fitting itself. ?
Click to expand...

I'd go for bigger skin fittings to match the size of the hole cutter you used.

By the way, it's a strange method you've used. It doesn't take long to grind off the flange of a skin fitting with an angle grinder and it is quite easy to do it carefully enough to avoid touching the hull of the boat.
 
Drilling a new 1" hole sounds like a nightmare, or lots of extra work. If you do the extra work you may as well do it properly and start again.

I'd go the Sika/CT1 route with big washers or reinforcement. But there is little point in lots of reinforcement on the inside if the overlap on the outside is minimalist. You could make big washers for the outside (if they are difficult to source) from fibreglass sheet you make up yourself. Simply make up sheet from some decent glass 750gm double bias, 2 or 3 layers, and the drill out with appropriate hole saws. Chamfer the edges and if you make enough you can use some on the inside (and keep some for future disasters). Make up on heavy duty plastic, polythene, sheeting and you will get a decent enough outer surface (and coat with Interprotect).
 
Firstly, what a daft way of removing a through hull !

If there is only 1mm of pla all around the fitting there is nothing to worry about, stick it in with sealant, end of.
 
thesaintlyone said:
So in the process of removing the seacocks I cut out some very difficult to remove skin fittings using a holesaw just slightly larger than skin fitting itself. Three in Total all 3/4 " Head Sink Outlet. Galley Sink Outlet and Engine Raw Water Inlet

When I put the new 3/4" Skin Fittings in they move a little as the hole is now slightly bigger!!!!

What are my options????
Click to expand...

i'd smear some epoxy resin and glass around the inside edges of the hole to reduce the diameter a bit, tidy up the outer edge with a bit of gelcoat and use plenty of ct1 to seal the new skin fitting in. a washer on the inside to spread the load is no bad thing.
probably over kill but what the hell.

one question i have is in tightening up the skin fitting as i have heard conflicting advice. does the team recommend tightening the fitting fully in the first instance or tightening to a little over hand tight and murdering up after the gunge has set?
 
viago said:
one question i have is in tightening up the skin fitting as i have heard conflicting advice. does the team recommend tightening the fitting fully in the first instance or tightening to a little over hand tight and murdering up after the gunge has set?
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You hear both because there are sound arguments for both approaches and therefore strong advocates for either one or the other. Personally I don't think it matters in this case provided there is plenty of sealant and the nut is tight.
 
Neeves said:
Tighten fully in the first instance.

Advise from sealant manufacture in Oz.
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Same here in a different application.
Disturbing the joint by leaving it slack then tightening is a recipe for shearing the sealant off either the hull or the fitting.
Particularly on a round skin fitting.
 
lw395 said:
Same here in a different application.
Disturbing the joint by leaving it slack then tightening is a recipe for shearing the sealant off either the hull or the fitting.
Particularly on a round skin fitting.
Click to expand...

Exactly what I was advised.

The other advise, for a CT1 type product, was do NOT clean with turps, either before application or during cleanup. It cleans exceptionally well - but weeps into the sealant and weakens the bond - clean with water.
 
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