Filling up wrongly cut bow thruster holes

[C. Dog]

If you use epoxy; you cannot finish it with gelcoat.

But if this is in the antifouling; it doesn’t matter.

An expert would tint a marine two pack paint and spray over epoxy if it had to be used. Also we need to distinguish between gelcoat and flowcoat as gelcoat is for molded surfaces. Flowcoat goes on rough and requires sanding and polishing for a gelcoat like finish.

 

[wet feet]

If I had to do the job,and I sincerely hope I never have to do anything of the type,I would begin in much the same way as comfisherman by attaching a flexible piece of ply that had been covered with melamine laminate to the outside of the hull surface as a first step.Then I would create a light layup-say 3 plies of 600gsm mat over gelcoat.Then cut a hole for the tube,in the knowledge that I had some hope of getting it level and symmetrical.After carefully fitting the tube,get inside and bond it thoroughly and with great care.I would use the isopthalic resin as advised because I understand it's characteristics.If you feel compelled to use epoxy,and peer pressure pushes a lot of amateurs in that direction,do keep in mind that it works best with cloths or multiaxial types of material.These won't stretch or distort too much and will need careful tailoring to come into contact with all the surfaces and access is far from good down there.Polyester or vinylester with csm will result in a laminate that can be stretched or distorted with comparative ease.

If you look up the Sleipner guidance I mentioned in an earlier post,you will see that they recommend a radius where the tube meets the hull and some self adhesive sheet wax may be a good way to begin this shaping once the tube is tacked in place.Done right you will minimise drag and noise from the installation.

 

[fallguy]

I’m confused. So, the tube is held in place how? Or not at all?

If not, would you be able to pour structural foam into the void? Or could you piece in some foams and then pour the rest?

In my earlier post, I assumed you had found a way to hold the tube and cut it and then you were patching over the new tube.

Foam it all in and fair the foam to the tube cut which is made to the fair location on the hull. The foam acts as a backer for the patch and provides strength to support the tube as the bondline for the tube is not large.

Another approach would be to build the tube out to the prior thickness with same foam if access is limited. The entire thing is inserted, then faired.

Also, if the bondline is too narrow; epoxy would be my choice as well, but I’d never trust say an 1/8” wall of fiberglass tube intersecting a few layers of csm.

 

[Blueknarr]

I agree with most of the advice given. Since the tube is FG the tabbing used to secure it can also function as the over large hole repair.

I would also use a formica sheet to establish the external shape with just 2 or 3 layers of fg. Place the tube. Then combine the tube tabbing and hole repair.

I prefer iso over epoxy.
Epoxy is also acceptable.

After you grind the taper you can see the weave patterns of the original construction.
It is considered best practices to use the same resin, gage and weave in the repair as was used in the original.

A repair thicker than the original is usually better than one that is thinner.

I don't envy the awkward access.

I suspect that smaller pieces of cloth will be easier to lay in than larger ones.

Only you can determine if the benefit of using a familiar resin out ways the benefit of easier laying cloth.

Good luck

 

[ondarvr]

This is a very common layup in the chemical tank or filament wound tank industry, I did that for over 20 years. Hold it place with wedges, then glass it. It really is that simple.

 

[wet feet]

The parallels go well,since every tube I have seen was filament wound.Given the proximity of the surface,even after a reduction in tube size,I wonder if adding an "eyebrow" ,something like an equilateral triangle section that extends a few inches from the tube in fore and aft terms and tapers to nothing would act as a further deterrent to air finding it's way in.I'm sure many of us will have seen stern thrusters with a downward angled cowl at the ends of the tube for this kind of situation.