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    Notice on 2021-2022 Fund Raising

Seeking Input - Hull Repair

Prairie Schooner

Jeff & Donna, new owners 7/21
We will be getting new instruments in our ’86 E35-3. I think a third transducer was installed at some point which leaves us with three holes. The electronics company requested that we fill them all and they’d make a fresh one.

I couldn’t get a wrench on the existing thru-hulls or make a tool to try to unscrew them so I decided to just drill them out. Smart? Maybe not, but it’s water under the bridge. In the process of grinding out the scarf I ended up getting into the TAFG. More water under the bridge. Anyway, I went out about 10’’ from the hole edges. At 3/4” thickness that’s about a 1 to 13 scarf.

I’m using epoxy because of the better adhesion. We’re due for a warm day here in New England this Thursday. It will get alternating layers of biaxial cloth and woven cloth, placed at different angles, with the largest patch touching the hull first, getting progressively smaller. I’ll put 2-4 layers inside as well.

The holes will be smoothed out. I just didn’t have a drum sander with me today.

Anyway, does it look like there’s anything grossly wrong here before I start laying up?
 

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bigd14

Sustaining Member
Blogs Author
Looks like a good plan. Suggestion: install the biaxial cloth on the inside first and let it harden as much as possible. This will provide a nice backer so you don't push all the layers into the boat as you are squeegeeing the air bubbles out.

I have done about a dozen of these and after the first few I modified my procedure to go with the smallest piece of material first (which is still slightly larger than the actual hole) and gradually get bigger matching the expanding radius of the hole. I realize this is against the advice of Gougeon Brothers et al, but it seems like its easier to get a bond between all the layers this way and prevent voids and air bubbes. Once the individual holes are filled I then cap the entire thing off with 2-3 progressively larger layers of biaxial cloth to really bond it well out to the rest of the hull. The end result is rock solid.

Also, when wetted out the biaxial will be thinner than you think, likely necessitating many many layers. Plan ahead with lots of cutout pieces ahead of time! Nothing like cutting biaxial under duress with epoxy hands...

Good luck with the project.

Doug
 

texlan

Member I
Blogs Author
Looks like a good plan. Suggestion: install the biaxial cloth on the inside first and let it harden as much as possible. This will provide a nice backer so you don't push all the layers into the boat as you are squeegeeing the air bubbles out.

I have done about a dozen of these and after the first few I modified my procedure to go with the smallest piece of material first (which is still slightly larger than the actual hole) and gradually get bigger matching the expanding radius of the hole. I realize this is against the advice of Gougeon Brothers et al, but it seems like its easier to get a bond between all the layers this way and prevent voids and air bubbes. Once the individual holes are filled I then cap the entire thing off with 2-3 progressively larger layers of biaxial cloth to really bond it well out to the rest of the hull. The end result is rock solid.

Also, when wetted out the biaxial will be thinner than you think, likely necessitating many many layers. Plan ahead with lots of cutout pieces ahead of time! Nothing like cutting biaxial under duress with epoxy hands...

Good luck with the project.

Doug
Having filled a few holes.. I lay up a few layers of biax on plastic or in a paint tray liner big enough to cover all the holes with ~1" overlap, then pick them all up, wet, and drop them on top of the holes like bigd14 suggests. Let them tack enough to provide some backing, and then go to town from the bottom.

His layup schedule (smaller to larger) works the best in my experience. Also, I find that letting the layers tack in between sets of 3 or 4 helps to keep the whole wet soggy mess from falling down under its own weight.

p.s. for bottom-side layers of biax i'd again wet them out on a paint tray or taped down plastic and then apply the whole set of 3-4 at the same time ..makes the job go faster and less frustrating.

I'd skip the woven -- while it's thicker than biax, biax is stronger, more fair, and the layers are less likely to peel apart wet and upside down due to more contact area.

bring some fairing compound anyways...
 
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Prairie Schooner

Jeff & Donna, new owners 7/21
. . . I modified my procedure to go with the smallest piece of material first . . . I realize this is against the advice of Gougeon Brothers et al, but it seems like its easier to get a bond between all the layers this way and prevent voids and air bubbes.

Also, when wetted out the biaxial will be thinner than you think, Nothing like cutting biaxial under duress with epoxy hands...
Thanks Doug. Good input.
- Hmmm. I guess the theory of the biggest sheet first is connecting the strength. But as I think of it, as long as I don't sand into the big layers, the connection should be there.
- Do you have a guesstimate on how many layers for .75"?
Jeff
 
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markvone

Sustaining Member
Previous thread with tips and number of layers:


Mark
 

Prairie Schooner

Jeff & Donna, new owners 7/21
Having filled a few holes.. I lay up a few layers of biax on plastic or in a paint tray liner big enough to cover all the holes with ~1" overlap, then pick them all up, wet, and drop them on top of the holes like bigd14 suggests. Let them tack enough to provide some backing, and then go to town from the bottom.

His layup schedule (smaller to larger) works the best in my experience. Also, I find that letting the layers tack in between sets of 3 or 4 helps to keep the whole wet soggy mess from falling down under its own weight.

p.s. for bottom-side layers of biax i'd again wet them out on a paint tray or taped down plastic and then apply the whole set of 3-4 at the same time ..makes the job go faster and less frustrating.

I'd skip the woven -- while it's thicker than biax, biax is stronger, more fair, and the layers are less likely to peel apart wet and upside down due to more contact area.

bring some fairing compound anyways...
Thanks texlan. Good idea on the inside layers first. I'll do that.
I like the 3-4 layers at a time bit.
I'm not sure if I'll have enough biax so I'll have to use some woven, but good to know the relative thicknesses.
I was Thinking about doing the fairing another day, but maybe I'll try to get to it tomorrow too.
Jeff
 

Prairie Schooner

Jeff & Donna, new owners 7/21
Previous thread with tips and number of layers:


Mark
Yikes, using Loren's 10 oz. thickness I'm going to need 57 layers!
Thanks Mark.
 

Loren Beach

O34 - Portland, OR
Senior Moderator
Blogs Author
I have seen (reputable) boat yards do this with a combo of fiber-filled epoxy filler and XX layers of cloth. They swore by their method.
If totally on my own, I would use many layers of bi-ax.
Last time I had the yard fill a hole in the bottom, I added some layers later inside -- sort of a "belt n suspenders" mentality.
 

Prairie Schooner

Jeff & Donna, new owners 7/21
I have seen (reputable) boat yards do this with a combo of fiber-filled epoxy filler and XX layers of cloth. They swore by their method.
If totally on my own, I would use many layers of bi-ax.
Last time I had the yard fill a hole in the bottom, I added some layers later inside -- sort of a "belt n suspenders" mentality.
That thought crossed my mind Loren but I didn't know if it was insanity or inspiration. I'll see how things are going with the first dozen or so layers, but for this I think the 'better safe than sorry' camp is the way to go.
 

bigd14

Sustaining Member
Blogs Author
In some of the thicker holes I have added 1/4 or 1/2 inch thick disc of G10 as filler to avoid the very situation you describe. I figure with 3/4 inch of existing layup thickness all around a small thru hull hole this will be plenty strong. But with three holes close together I am not entirely sure. I would probably do it but you might think pretty hard about it based on how strong you think that entire area is. In my case I didn’t feather the holes all the way back to nothing, more like 1/4 inch down to the level of the G10 filler. And I made sure that the inside layers were really well bonded for a good distance around as per Loren’s “belt n suspenders” approach.
 
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Prairie Schooner

Jeff & Donna, new owners 7/21
In some of the thicker holes I have added 1/4 or 1/2 inch thick disc of G10 as filler to avoid the very situation you describe. . . . .
I ended up doing something like that Doug. I installed three layers of 10 oz. cloth on the inside. Then from the bottom I put one layer of cloth over all three holes, after which I put 5 discs of biax in each of the holes. The structure inside is the TAFG so I didn't have direct access to the inside of the hull. The smile in the 4th photo of my initial post is because of this. I crammed trimmings from the biax in there with resin. A photo of these plugs is attached here. Then I put up the largest overall patch in biax, followed by another somewhat smaller. It got dark before I could finish the job (or take pictures).
We had unseasonably warm weather today here in Rhode Island. I'm hoping for another to finish the job.
 

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