Through hull woes

[Clyde Coastin']

Hello all,

Firstly, apologies for the newbie question. I was looking for advice as I am in the middle of fitting my first through hull for a new raw water inlet. I drilled the hull square from the outside and the new skin fitting sits nice and flush on the outer hull. My question is that the plug that came out the hull is amout 1.4mm thicker at one side than the other, owing to the curvature of the inner hull.

I am fitting a TruDesign composite through hull and valve and the plastic washer will now not sit perfectly square against the nut on the inside of the hull. Is this an issue, or will the sikaflex between the platic washer and the hull seal up anyway?

I'm not sure what my options would be to correct this as glassing for 1.4mm seems crazy, I'm tempted to taper the spare washer that came with the kit and use it to make up the gap. I am using a load collar also (which actually sits pretty square...) I assume this will take a lot of the mechanical load from the washer nut area also.

Any and all suggestions welcome!

 

[superheat6k]

A nice thick gasket of sikaflex plus an internal pad piece ~ 3 x the diameter of the fitting will take up the difference.

I would set it loosely so you see a full squidge of the sika right under the pad piece and outer flat of the ski fitting, then just nip and leave for a week to allow the sika to cure, then pull up quite stiffly.

It won't ever leak.

 

[ash2020]

I was always taught to put a plywood washer on the inside, quite a bit larger than the hole. The logic being that if there is a slight leak, the ply will tend to swell and seal it. If you look at skin fittings in different boats you'll find that many have a plywood washer. Birch ply is the best, 12 or 15mm. I wouldn't use tree wood with a grain as it could split into 2 parts along the grain. Also, yes, Sikaflex.

 

[Fr J Hackett]

Use a plywood pad which you can then taper slightly to account for the very small angle a rasp file will be sufficient then a good smear of Sikaflex to bed it down and then the plastic washer will sit square on the plywood pad. In the absence of sealing the sides of the hole and cut raw fibreglass make sure you use Sikaflex or butyl tape to bed the unit on the outside to avoid water ingress into the fibreglass, you can use the butyl tape on the threads as well.

 

[Rhylsailer99]

I have to do 2 cockpit drains 1.5" through hulls did all my others with thickened epoxy under the plywood plates ,would sikaflex have been a better option

 

[Fr J Hackett]

I have to do 2 cockpit drains 1.5" through hulls did all my others with thickened epoxy under the plywood plates ,would sikaflex have been a better option

No