How to reduce the diameter of a thru hull to install new skin fitting?

[robo555]

I had a Blakes 1 1/2" bronze seacock where the inside flange was fibreglassed into the hull. It was corroded (pink), so I removed it by drilling it out with a slightly bigger hole, leaving the flange still glassed in.

Now I have a 54mm diameter hole in the boat, and the replacement TruDesign skin fitting uses a 48mm diameter hole, i.e. when I insert the new TruDesign skin fitting, it wiggles about 3mm on all sides. What's the best way to install the new skin fitting? So far, I've got the following suggestions from people in the boat yard:

1. Grind out the hole to a dish size shape, re-glass it then drill the new hole. Understandably it's the most proper method but it's not an option for me. It's too much work (and risk for a newbie) to do this job, and I end up drilling out most of the work anyway.

2. Fill the hole with epoxy + thickener, then re-drill the 48mm hole. In effect I'm left with a ring of 2-3mm thickened epoxy to reduce the size of the hole. People has told me the epoxy won't stick to the existing fibreglass, but I'm also reading books saying epoxy is fine for repairing fibreglass.

3. Insert the new seacock with a lot of Sikaflex. Let the Sikaflex ooze out when installing the TruDesign skin fitting, don't tighten it too much, then tighten it proper a few days later. This was advice from a boat builder, 3mm of Sikaflex to hold the skin fitting is fine 'cos the skin fitting has the flange to hold it in place as well. But I dunno...3mm on all sides seems like a lot of wiggle space.

What do you think I should do to install the replacement TruDesign skin fitting? I'm leaning towards option 2, but don't know whether the 3mm ring I end up with will stick to the existing fibreglass, and what sort of epoxy / thickener I should use.

Thanks

[Orion Jim]

Your first option is the only option, unless you intend to keep your boat on the hard forever or you never want to sleep soundly again should you decide to actually launch the boat. YouTube is littered with tutorials, take your pick.

[Thomas1985]

Option 1 isn’t as bad as you think. I was shocked how easy fiberglass work actually is once I got going doing some

[deltaten]

As long as surface is clean, dry, applied to spec, epoxy will stick to anything but most plastics. Couple days on the hard should see you right for 'glass replacement and install.
Then again....3mm is only 1/8" +/-, so not a lot of fill needed..
.if you don't mind worrying over it.

[barnab]

If you read the installation instructions you'll find that TruDesign actually suggest to glue the through-hull into fibreglass boats with thickened epoxy. I wouldn't get sleepless nights over the 3mm.

Install the load bearing collar with the through-hull and you will be fine (this is not related to the 3mm, but will keep the through-hull in place even if something tries to knock it off)

[Bowdrie]

Originally Posted by barnab

If you read the installation instructions you'll find that TruDesign actually suggest to glue the through-hull into fibreglass boats with thickened epoxy.

As per that suggestion from TruDesign, should one decide to do that it behooves them to make a "dry run" first, and make some index marks.
Murphy's Law states that when the seacock is screwed onto a non-indexed thru hull the operating lever will never be in the orientation desired.

[s/v Jedi]

Option one of course. I find it disturbing that you think it’s too much work for you to do…

It’s not just easy, it’s also a fun, confidence building job.

Next time, use the correct size holesaw to drill the fitting out. You simply cut through the fitting instead of the glass.

[bil56]

I had this problem with a fishfinder.
the flange of the thru-hull is wider than the hole,
drill a few holes in the thickness of the hull, only a few mm deep to improve adhesion,
wrap the hull in PE film or a few turns of tape, wax or lightly oil,
put in place and secure from the outside ,
seal the remaining interior space around the through-hull with an epoxy/thickener mixture.
remove the through-hull by tapping gently with a wedge, you're done!

if you are worried, grinder around the hole inside/outside, and 1 glass cloth on each side
if you are in a hurry, polyester/glass putty instead of epoxy mixture (less good)

cheers !

[more]

https://www.amazon.com/Groco-Bronze-.../dp/B004KCVUF8
best easy way is buy this and be happy

but also must know new EU boat ussualy dont have sika on thru hull. only rubber washer on see side.

option 2 also work. epoxy with some filament and hard fix trudesign. you can buy made some rubber gasket

this

https://www.corseal.co.uk/products/n...ant=9735691269

[bil56]

correct diameter O-ring and you are safe, the seal will not be crushed ...

[Bowdrie]

Ah yes, it seems that even an old-line company like Blakes has gone to the dark side.
From their website; "Cast DZR Brass/Bronze components".
The body from DZR?
I'm sorry, for what they charge that's a pos.

[Fore and Aft]

Robo555 I would be happy epoxy gluing in the skin fitting. I do that with mine and I have removed other skin fittings that have been glued in and they are a real pia to get out.
But you don't mention, and I can't find any specifications on the size of the Tru Design flange? I imagine it is at least 12mm so you would still have 9mm of hull until the glue drys. If you do glue it in, then you're going to need to do some prep first. You will need someone on the outside with a marker pen to hold the skin fitting while you are on the inside measuring the gap and making sure it is even all the way around the skin fitting. Once perfect the outside person needs to draw around the skin fitting. Then for peace of mind I would wind the skin fitting nut down and draw on the outside of that as well. Then just follow the instructions for installing a skin fitting. I always like to wind the seacock on before doing the final tightening of the skin fitting nut. That way I can still rotate the skin fitting to get the seacock handle in the right position.
Cheers

[catsketcher]

I reckon the boatyard is stupid, 3mm gap is nothing for epoxy glue and all the fairing needed for the dishing out is a huge amount of work for no improvement in strength. The radius of the flange will be fine to handle any potential issues. If they recommend using polyester resin for the new glass then you have real issues with secondary bonding which scares me, whereas I have 2mm epoxy filled gaps around every through hull.

Whoever told you epoxy doesn't stick to polyester is totally wrong, good epoxy like WEST 105 loves sticking to anything apart from some plastic containers. I have built 4 boats out of epoxy and stick epoxy to polyester laminates, PVC, and even aluminium, and it loves woods like douglas fir and cedar. Epoxy is how people who can't cut things well build boats.

In fact epoxy NEEDS a sloppy fit. When I place bulkheads into a hull I don't place the bulkhead onto the hull, I suspend it by about 5 mm and then push epoxy filler under it and cove it. Good WEST type epoxy with silica powder in it to make a smooth peanut butter consistency can handle gaps up to 20mm. Epoxy joins are usually under low pressure so you don't squeeze the glue out. So most well built composite boats have a 3-5mm gap under all their bulkheads that the epoxy takes no worries.

Now I am different to most - I epoxy my skin fittings in too. I use plastic skin fittings that are epoxy compatible - been fine for 24 years so far and no issues with water ever. Tru design say you can epoxy them in too - I would go that way.

So if I was you I would make a peanut butter consistency epoxy glue, taoe a board to the inner hull side and smear the epoxy around the hole and then ream it out when hard with a tapered plug and sandpaper.

I am assuming the boat is solid glass - if it is cored then you REALLY need the epoxy.

BUt really, I would check your inside flange too - the backup plate. You should have a nice thick piece of something tough inside the boat, about 100mm square, bonded to the hull. Now if you don't, grind out about 200mm square inside, then glue on some G10 or some polyester laminate from the deck of a wreck boat about 100mm with rounded edges and then glass over that. You need a nice inside plate to help the hull cope with the point loads from someone stepping on the though hull

Cheers

Phil (Epoxy is your friend)

[gonesail]

i see no problem with filling the 3mm gap with thickened epoxy which is incredibly strong. you may need to drill the hole out after that. up to you.

[Robertkwfl]

For cored hulls, creating an annulus of thickened epoxy is absolutely best practice for thru-hull fittings. There’s no reason not to do it for uncored holes as well.

Duct tape works well for closing off one side when you add the epoxy.

It’s always good to wet out the surface with unthickened epoxy first. A 1/2” chip brush is good for that.

A syringe works well for filling the hole with thickened epoxy. Fill the hole completely then drill out the correct size hole once the epoxy has hardened.

I would prefer West System 404 as the thickener. It’s made for hardware bonding and, unlike silica, won’t absorb water.

The Gougeon Brothers on Boatbuilding book is a free download (Google it) and is an authoritative reference for the drill-fill-drill method and many other epoxy techniques.