When to patch vs fill a hole?

[wikakaru]

I have just purchased a "new" 1980 Cape Dory 22 that has a lot of holes in the deck and topsides that need to be repaired. For the small holes (e.g. 1/8 inch, like where mounting screws used to be) it is obvious that the solution is to fill with a thickened epoxy mixture; for the large holes (e.g. 3 inch, like where non-functional instrument cut-outs are) it is obvious that the solution is to bevel the fiberglass and build up a patch with incrementally larger layers of fiberglass. But what about medium-sized holes? There are a half-dozen holes from about 1/2 inch to one inch that need to be fixed. What is the best way to fix that size hole?

Thanks,

Jim

20190812_174228.jpg

[Kickin Bears]

I’d tackle that by making a single flat layer fiberglass piece (laid up on a flat piece of plastic), let it cure, trim up edges/clean, epoxy in behind holes, then evaluate. You could probably fair it from there. Cutting a small patch piece of cloth to layup as a second step, if theres room without creating a lump that would have to be ground down, is an option too. Then fair it from there.

Look fw to seeing other opinions.

I know a number of folks who would epoxy in the patch, fair it, sand (repeat if necessary), and then call it and move on to the next project.

[Markst95]

Use a countersink on the small holes. More surface area for the epoxy to adhere to and less chance of a stress crack.

[JD-MDR]

What about below the waterline? I replaced some thru hulls . The new ones had different bolt pattern. The hull is thick 1-1/2" in some places. I wasn't sure how to fill the old holes so I let the yard do it. They just cleaned the surfaces and filled with epoxy. Also the new flathead screws are not countersunk and faired over like the originals. They are countersunk just to the surface. You can still see the screw heads. I just let it go and launched yesterday. Got all my chainplates replaced with 1/2" g-10. On to other projects . First I need to get out sailing a few trips. Please respond. Thanks

[wikakaru]

I’d tackle that by making a single flat layer fiberglass piece (laid up on a flat piece of plastic), let it cure, trim up edges/clean, epoxy in behind holes, then evaluate. You could probably fair it from there. Cutting a small patch piece of cloth to layup as a second step, if theres room without creating a lump that would have to be ground down, is an option too. Then fair it from there.

I'm not 100% sure I follow you. Are you saying to build up a "plug" out of fiberglass first, or are you saying to basically cover over one side of the hole with fiberglass and then add fairing to fill the rest of the depth?

Thanks!

Jim

[wikakaru]

Use a countersink on the small holes. More surface area for the epoxy to adhere to and less chance of a stress crack.

Thanks! Although the "stress crack" ship has already sailed. This boat already has lots of them that will also need to be addressed.

[Kickin Bears]

I’d tackle that by making a single flat layer fiberglass piece (laid up on a flat piece of plastic), let it cure, trim up edges/clean, epoxy in behind holes, then evaluate. You could probably fair it from there. Cutting a small patch piece of cloth to layup as a second step, if theres room without creating a lump that would have to be ground down, is an option too. Then fair it from there.

I'm not 100% sure I follow you. Are you saying to build up a "plug" out of fiberglass first, or are you saying to basically cover over one side of the hole with fiberglass and then add fairing to fill the rest of the depth?

Thanks!

Jim

The latter, implying all the fine print such as bevel @ 12:1 etc etc

[wikakaru]

The latter, implying all the fine print such as bevel @ 12:1 etc etc

Bummer. That's a pain to do for a 1/2 inch diameter hole.

Thanks for the advice!

Jim

[tjr818]

The latter, implying all the fine print such as bevel @ 12:1 etc etc

Bummer. That's a pain to do for a 1/2 inch diameter hole.

Thanks for the advice!

Jim

I doubt that I would go to that extreme. The recommended 12:1 ratio is for a structural repair to the hull. If these 1/2" holes are for wiring in bulkheads or in the hull liner I would not go that far, put a slight bevel on the hole mix up some epoxy and filler and have at it. It might take tow applications, but I should be fine.

[JD-MDR]

[quote="JD-MDR"]What about below the waterline? I wasn't sure how to fill the old holes so I let the yard do it. They just cleaned the surfaces and filled with epoxy. Also the new flathead screws are not countersunk and faired over like the originals. They are countersunk just to the surface. You can still see the screw heads. I just let it go and launched yesterday.
Hoping to get some response still. Oh they are just 1/4 and 3/8" holes in 1-5/8" hull thickness

[Paul D.]

Tim is correct is the holes are not structural, meaning they are in non critical areas needing strength. Here's a good video on the 3"hole repair, for 1"inch hole I reckon a somewhat less involved similar method would do well.

https://youtu.be/MVLRjxe_iUw

[wikakaru]

I doubt that I would go to that extreme. The recommended 12:1 ratio is for a structural repair to the hull. If these 1/2" holes are for wiring in bulkheads or in the hull liner I would not go that far, put a slight bevel on the hole mix up some epoxy and filler and have at it. It might take tow applications, but I should be fine.

I'm not sure whether any of these mid-sized holes qualify as structural. There are 3 locations:

1. The aft end of the cockpit just under the traveler.

Cockpit aft.jpg

2. The top of the transom just below the taffrail. (And possibly the bolts holding the outboard motor mount if I decide to go engineless.)

Transom.jpg

3. The aft face of the cabin house.

Cabin house.jpg

[wikakaru]

Tim is correct is the holes are not structural, meaning they are in non critical areas needing strength. Here's a good video on the 3"hole repair, for 1"inch hole I reckon a somewhat less involved similar method would do well.

https://youtu.be/MVLRjxe_iUw

Thanks! I've watched several videos, but that one is much better produced than the ones I watched. The through-and-through part of the hole they started with in the video looked to be about 1 inch, with damage extending out to about 3 inches, so they increased the size of the entire hole about 3 inches and then beveled and patched it.

All of my holes have sharp edges because they are drill holes, so presumably I would start beveling right away, but those would be some itty bitty pieces of fiberglass in the patch layers. I would think the glass would fray and the tiny patches would just fall apart as I was handling them if I tried to make the repair using this method, unless I do as they did and rip out a big section of the hull and make my 1/2 to 1" holes all 3" holes before I start. I don't really want to do that.

As a side note, I wonder why they didn't do the beveling on the inside of the hull so the part of the repair showing from the outside was much smaller?

Thanks,

Jim

[Kickin Bears]

I’ve never heard that the 12:1 bevel is for hull only, and the bevel ratio is based on the fiberglass thickness, not the diameter of the hole ...

Just my .02 cents

[tjr818]

Another method for those small holes on the cabin bulkhead is to fabricate a teak cover plate, that would cover all of them at once. The bad part about cover plates is that they might require screw holes to fasten them. When we removed an instrument from that same bulkhead I has able to fabricate a bronze plate that was the same shape as the old instrument and used the same mounting holes. It matches the bronze trim plate of the other instrument. Originally the plan was to replace that instrument with a newer knot log, but the single tridata display made that unnecessary.

Cabin from Aft Thumbnail.jpg