Fiberglassing in hole in thick hull.

[zboss]

Hello,

I am moving two through hull's further up on our hull and when we take then out we will leave two holes. Our hull is about 1.75 inches thick layup at that location. They used both fiberglass chop and cloth.

Obviously, if I followed the directions from West Systems I would need to grind out a sloped area three feet across. That's insane!

I was thinking about epoxying in a plug the total thickness and then grinding down both sides so I only needed to grind an area about 6 to 8 inches in diameter.

Opinions?

[Don C L]

Having done this once years ago I can only offer what worked for me. But I think the question is how much does that hole compromise the strength of the hull at that point? The through-hull does to some extent create a weak point in the hull. If you strike something at the through-hull vs. somewhere else how much more likely are you to cause a breach in the hull? Ideally you repair the hull to the extent that the hole now is covered in a way that equals the strength of any other corresponding part of the hull, or better. Hence the directions from West System I am guessing. However that does seem to me to be overkill too. In my own case I roughed up an area on the inside about a foot and a half wide (I did not take off layers of glass.) I layered up cloth with each layer about a half inch wider than the previous until I had a patch of about 1/2 to 3/4 inch which was the about the thickness of the hull at that point (much thinner than yours, it was a Columbia 24!) On the outside I filled the hole with epoxy putty and put two layers over it and faired it in. It was as bit of a bulge on the inside, yes, and it did seem like overkill too. It probably was, but I didn't think about it again. I never struck the patch so I don't know how it would have fared, but it sure seemed strong to me, and through-hulls are usually in places that don't get struck. Recently I removed the head and didn't have time to fill the hole so I just capped the through-hulls. That was a lot easier but not exactly permanent. I hope we hear from some fiberglass experts from West and/or Cabo Rico!

[Scott Berg]

12 - 1 bevel would be about 20" and that sounds rightDo you have the layup schedule from the builder? Much better to match it for flex and strength.


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[minaret]

Originally Posted by zboss

Hello,

I am moving two through hull's further up on our hull and when we take then out we will leave two holes. Our hull is about 1.75 inches thick layup at that location. They used both fiberglass chop and cloth.

Obviously, if I followed the directions from West Systems I would need to grind out a sloped area three feet across. That's insane!

I was thinking about epoxying in a plug the total thickness and then grinding down both sides so I only needed to grind an area about 6 to 8 inches in diameter.

Opinions?

Done it that way many many times. Buy a piece of G10 and laminate it together to make your plug. Then grind and glass exterior, grinding at least 1/8" material off and laminating with 2-3 1708. Then slap a fat patch on the interior too. Fair exterior, barrier coat, and paint to match.

[Jim Cate]

Perhaps I'm naive, but these holes have been in the boat since launching. They were "plugged" by the skin fitting, but not much strengthened. Now he has removed the skin fitting and needs to keep the water out. The hull is no weaker than it has ever been.

I find it hard to justify making a big deal out of this. Grinding a small bevel area on both sides, glass over the inside with a couple of layers, fill the hole with epoxy mish-mash and do a good job of glassing over the outside, then bog and fair. Waterproof and at least as strong as it has been all its life.

But I am not a pro...

Jim
Edit: Seems that Minaret and I were typing at the same time. And he IS a pro... I'd take his advice over mine any day!!

[Don C L]

Originally Posted by Jim Cate

Perhaps I'm naive, but these holes have been in the boat since launching. They were "plugged" by the skin fitting, but not much strengthened. Now he has removed the skin fitting and needs to keep the water out. The hull is no weaker than it has ever been.

I find it hard to justify making a big deal out of this. Grinding a small bevel area on both sides, glass over the inside with a couple of layers, fill the hole with epoxy mish-mash and do a good job of glassing over the outside, then bog and fair. Waterproof and at least as strong as it has been all its life.

But I am not a pro...

Jim

That's what I was thinking too, and then someone said, "if you hit that with a hammer as hard as any other place on the boat, will it leak?" So then, doubting my initial impulses, my patch started growing and growing...

[zboss]

The old "holes" are on the stern quarter of the vessel where the stern slopes back onwards, so unless I'm backing into something or maybe broadsiding something, then I think the likelihood of them getting hit are slip. But your advise is well taken.

I think I'm also comfortable with both Mineret's and Jim's advice.

[Impetuous too]

Don't regret going pretty overkill on ours, particularly the under water holes. We dished out both sides -in just over an inch of hull we went to about a foot across. A short cut we went with for a low risk spot was to glass a couple of ever increasing circles on the outside and fill in some of the inside with mish mash and epoxy. We probably put between twenty and thirty layers on each patch but in the grand scheme of things it was easy to do amongst other jobs so didn't take too long. Once we were pretty even we filled with thickened epoxy then awl-fair to get our shape back and long boards with guide coat.

Getting the cracks in the gellcoat out... Now that's another matter! It was a lot of work but we've no worries. All the best!

[RDW]

Take any suggestions. I give here with a large grain of salt
I did see a need video once. they did all the work from the inside. They placed a Pap plastic barrier over the outside with some sort of support. From the inside. They sprayed on a layer of jelcoat. They took some sort of routing tool and beveled out the center. A small amount. Then they applied there approximately N fiberglass from the inside. Upon removing the outside support. All they need to do was above the Jelcoat.

Again my only experience is watching the video. It did look like an excellent repair.
Best of luck.
rdw

[zboss]

I saw that gelcoat trick as well. They basically put plastic on the outside and taped over it then sprayed the gelcoat on and followed it the layup.

[chouliha]

Originally Posted by Jim Cate

Perhaps I'm naive, but these holes have been in the boat since launching. They were "plugged" by the skin fitting, but not much strengthened. Now he has removed the skin fitting and needs to keep the water out. The hull is no weaker than it has ever been.



I find it hard to justify making a big deal out of this. Grinding a small bevel area on both sides, glass over the inside with a couple of layers, fill the hole with epoxy mish-mash and do a good job of glassing over the outside, then bog and fair. Waterproof and at least as strong as it has been all its life.



But I am not a pro...



Jim

Edit: Seems that Minaret and I were typing at the same time. And he IS a pro... I'd take his advice over mine any day!!

Jim. Greetings

That is just what we did when we needed to patch a transducer hole. Ground it out to about 5 inches slapped in some epoxy and 6 layers biaxial cloth and then bogged over the area that wasn't totally filled in. Again our old hull is pretty thick.

Cheers

Chuck


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[GILow]

I asked a pro from our yard to do this for us at our first slipping. Our hull is over 2 inches thick, nearer 2.5 for most of the holes that needed to be plugged.

He had a collection of premade fibreglass disks of the same size as the through hull holes. He packed these disks in to make up the bulk of the filling then did the bevel thing with the outer layers.

Have not sunk yet.

Edit. On rereading minarets post I wonder if what I thought were fibreglass disks were actually the g10 laminate minaret mentions. I will ask the yard guy when I see him next. Anyway, they were precut disks of some slightly off white material.

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[minaret]

Originally Posted by GILow

I asked a pro from our yard to do this for us at our first slipping. Our hull is over 2 inches thick, nearer 2.5 for most of the holes that needed to be plugged.

He had a collection of premade fibreglass disks of the same size as the through hull holes. He packed these disks in to make up the bulk of the filling then did the bevel thing with the outer layers.

Have not sunk yet.

Edit. On rereading minarets post I wonder if what I thought were fibreglass disks were actually the g10 laminate minaret mentions. I will ask the yard guy when I see him next. Anyway, they were precut disks of some slightly off white material.

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Nah, I do what your guy did. Just don't expect others to have fiberglass flat stock scraps of varying thickness lying around.

[Cheechako]

Originally Posted by Jim Cate

Perhaps I'm naive, but these holes have been in the boat since launching. They were "plugged" by the skin fitting, but not much strengthened. Now he has removed the skin fitting and needs to keep the water out. The hull is no weaker than it has ever been.

I find it hard to justify making a big deal out of this. Grinding a small bevel area on both sides, glass over the inside with a couple of layers, fill the hole with epoxy mish-mash and do a good job of glassing over the outside, then bog and fair. Waterproof and at least as strong as it has been all its life.

But I am not a pro...

Jim
Edit: Seems that Minaret and I were typing at the same time. And he IS a pro... I'd take his advice over mine any day!!

I'm with Jim on this one. I'd plug the hole and grind both sides to put maybe 1/4" + of glass layup on each side and call it a day. Use the plugs you core out of the hole for the new location for the plug!

[RDW]

Use the plugs you core out of the hole for the new location for the plug! __________________
Excellent thinking
rdw