Making thru hull holes smaller...how?

[Rowglide]

I am currently replacing all my seacocks and have encountered a small issue.
The original holes for all thru hulls are loose. On average about 1/8”-3/16”of slop. The hull is 5/8”-3/4” thick.
I am installing G-10 backing plates, epoxied to hull. The holes cut in the G-10 are snug to the thru hull OD.
What should I do to improve the holes in the hull? I’d rather not grind out and fill them in , and then re-bore them.
Here is what I thinking of doing...
Sand bore of each hole with a coarse drum sander. Wet glass with epoxy then put on a thin layer 1/16-1/8” of epoxy thickened with 1/4” glass chop.
Drum sand to final dimension.

How does this sound?

[rbk]

1/8” - 3/16 slop isn’t the end of the world 1/16 - 3/32 around the diameter. 5200 the flange and up the through hull should take case of it. 4200 if you’re thinking about doing it ever again.

[SailsWithFists]

No need for the holes to be tight. The tolerances you indicated are fine. The thru-hull flange properly sealed to the hull will do the job along with the backing plate you specified.

[Rowglide]

I guess it just seems really sloppy. My inner perfectionist (He only shows up occasionally) is not very happy with it.

[rbk]

Well if he (the perfectionist) bought the thru hulls I’ll assume they’re a bronze thru hull with flanged seacock, or better yet a flanged adapter and inline ballvalve. If the second is the case you should literally never again have to remove the thru hull and flanged adapter and only have to replace the ball valve once again in our lifetime if that. In that case expose the glass around the hole and inside the. 5200 the crap out of it, the bond will be stronger than the hull and if they ever have to come out again it’ll be someone else’s problem. (Just did all mine as well) Hint-someone’s selling a groco step wrench for $25 on here. It’s easy enough to do it without but $25 is cheap and you could probably pimp it out for beer after you’re done with it

[S/V Alchemy]

Originally Posted by rbk

Well if he (the perfectionist) bought the thru hulls I’ll assume they’re a bronze thru hull with flanged seacock, or better yet a flanged adapter and inline ballvalve. If the second is the case you should literally never again have to remove the thru hull and flanged adapter and only have to replace the ball valve once again in our lifetime if that. In that case expose the glass around the hole and inside the. 5200 the crap out of it, the bond will be stronger than the hull and if they ever have to come out again it’ll be someone else’s problem. (Just did all mine as well) Hint-someone’s selling a groco step wrench for $25 on here. It’s easy enough to do it without but $25 is cheap and you could probably pimp it out for beer after you’re done with it

^^This in spades. The bit keeping the water out isn't so much the "hole slop", which sounds nastier than it is. Maine Sail's tutorials on this are all you should need to keep that perfectionist pleased.

[Cheechako]

It does seem a bit sloppy if you are talking that gap all around, but if on the diameter about right. I wouldnt worry or spend time. Use lots of 5200 and your done!

[Suijin]

Originally Posted by Rowglide

I guess it just seems really sloppy. My inner perfectionist (He only shows up occasionally) is not very happy with it.

Sometimes sloppy is preferable. If the hole-to-thru-hull fit were perfect there would be a good chance of not getting a good caulked seal in the hole itself.

This assumes, however, that you've installed your backing plate properly, i.e. that it is bedded so that the flange bottom is perfectly flat when screwed down on the thru-hull. That's what gives the assembly it's strength and rigidity.

[deblen]

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[boatman12]

Assuming the flanges of the thu hulls are larger in diameter than the holes, how about cutting some donuts out of a stable material and filling the "slop" with these. This will keep the thru hulls centered in the holes. Epoxy them in place.