Plugging 7/8" hole in 1 1/4" solid FG.

[Patrick of M]

Seems common wisdom is bevel the repair 12x hull thickness, then build up in epoxy and cloth. My hull is 1.25" solid FG. Even working both sides reducing to 6x each side that is a big patch either side,. Also the hole is keel adjacent so no room for a big patch, especially on the inside.
Other acceptable repairs?
The hole had a speed sensor in it .

[Chotu]

Originally Posted by Patrick of M

Seems common wisdom is bevel the repair 12x hull thickness, then build up in epoxy and cloth. My hull is 1.25" solid FG. Even working both sides reducing to 6x each side that is a big patch either side,. Also the hole is keel adjacent so no room for a big patch, especially on the inside.
Other acceptable repairs?
The hole had a speed sensor in it .

The boat wasn’t breaking apart with the speed sensor in it, so it won’t break apart with an epoxy plug in it.

Fill ‘er up with slow epoxy and mix in some chopped glass fibers if you want some more peace of mind.

[Patrick of M]

Good point....they don't fall apart with 2" thru hulls either, but I guess its a matter of degree

[RyanC27]

I made a similar repair by first epoxying in place a G10 disk that was thinner than than the hull thickness
https://www.mcmaster.com/product/90444A112

And then built up a fiberglass schedule on either side

[coopec43]

Originally Posted by Chotu

The boat wasn’t breaking apart with the speed sensor in it, so it won’t break apart with an epoxy plug in it.

Fill ‘er up with slow epoxy and mix in some chopped glass fibers if you want some more peace of mind.

Maybe you guys use a different type of Chopped Strand Matt (CSM) but in Australia our brands of CSM are incompatible with epoxy. Maybe times have changed?

"It is not advisable to use emulsion bound CSM with epoxy; the emulsion binder will not be dissolved, limiting resin saturation and laminate quality. Instead, a powder bound CSM is recommended, given that it does not need to be dissolved in the same way and is ultimately compatible with epoxy resin."
https://www.resinlibrary.com/contact-us/

[Chotu]

Originally Posted by coopec43

Maybe you guys use a different type of Chopped Strand Matt (CSM) but in Australia our brands of CSM are incompatible with epoxy. Maybe times have changed?

"It is not advisable to use emulsion bound CSM with epoxy; the emulsion binder will not be dissolved, limiting resin saturation and laminate quality. Instead, a powder bound CSM is recommended, given that it does not need to be dissolved in the same way and is ultimately compatible with epoxy resin."
https://www.resinlibrary.com/contact-us/

It’s an English to English translation problem. Ha ha

Chopped strand Mat is not chopped glass fibers.

This is what chopped glass fibers are:

https://www.fibreglast.com/product/1...lass_Fibers_30

Mat with epoxy is mostly just a waste. It provides little strength (and no direction of strength) for a LOT of weight gain and wasted material. It should really never be used with epoxy. Its entire purpose was to provide a bulking effect for use with polyester, yet… you will find people (even on this very forum) who use it in the form of 1708 with epoxy. Wasteful. Heavy. But they love their 1708.

Uni, biax and stitched cloths (sometimes woven cloth) are the preferred materials for epoxy based construction.

But we are talking about chopped glass fibers, not mat. He’s just filling a small hole. Mixing chopped glass fibers in makes his epoxy plug as good as the surrounding material, should he say….. ground the boat right on a pointy rock in the exact spot his transducer used to be.

Although with the hole being right next to the keel, he’d have to be tipped way over on his side, coming down the face of a breaking wave at some really crazy angle onto the rocks for this to actually happen. Lol

[coopec43]

[QUOTE=Chotu;3832251]It’s an English to English translation problem. Ha ha

Chopped strand Mat is not chopped glass fibers.

This is what chopped glass fibers are:

https://www.fibreglast.com/product/1...lass_Fibers_30

/QUOTE]


Yep! I have no problem with that.......


Chotu Any idea when you plan to launch? My biggest problem was getting insurance (They insisted on a "safety survey" before they would cover the yacht)

[Chotu]

[QUOTE=coopec43;3832266]

Originally Posted by Chotu

It’s an English to English translation problem. Ha ha

Chopped strand Mat is not chopped glass fibers.

This is what chopped glass fibers are:

https://www.fibreglast.com/product/1...lass_Fibers_30

/QUOTE]


Yep! I have no problem with that.......


Chotu Any idea when you plan to launch? My biggest problem was getting insurance (They insisted on a "safety survey" before they would cover the yacht)

I launched 5 or so years ago. Have about 4000 miles on the boat. Insurance will be very different for you than me because of our different countries. I was able to insure mine through one of the standard big insurance companies here. Haven’t tried comprehensive insurance because I’m not willing to go through all the bs. I have liability for marinas. Also, until a boat is 100% complete most won’t insure it anyway. They assume you’ll quit the project and burn it

[JBP]

Originally Posted by Patrick of M

Good point....they don't fall apart with 2" thru hulls either, but I guess its a matter of degree

The problem isn't hull strength. The problem with large plugs is that they can come loose over time. What with thermal expansion/contraction and maybe some hull flex thrown in, the joint between the plug and old hull can eventually crack and leak and possibly fail.

If you can't get 6:1 all around, I'd feel safe if you can do an oblong which is greater that 6:1 on the long axis even if less than 6:1 on the short side.

[Kettlewell]

I'd just use epoxy putty in a 7/8" hole. Run a round rasp through the hole to make sure it is roughed up, and then seal coat the inside of the hole with your favorite epoxy resin. Let dry a bit but not all the way, then fill in the rest of the hole with thickened epoxy paste. I've used Petit underwater epoxy before and it is great stuff, and incredibly sticky when applying. https://www.jamestowndistributors.co...ct-detail/6766

[rwidman]

You know how the repair is supposed to be done but you are asking on an Internet forum for permission to do it the wrong way?

If your plan is to just fill the hole with epoxy or fiberglass, there is a good chance that your "plug" will come loose and fall out at some point.

If you don't want to fix it the right way, put the speed sensor or something similar back in the hole, sealing it properly, and move on.

[rwidman]

Originally Posted by JBP

The problem isn't hull strength. The problem with large plugs is that they can come loose over time. What with thermal expansion/contraction and maybe some hull flex thrown in, the joint between the plug and old hull can eventually crack and leak and possibly fail.

This is the correct answer.

[Bowdrie]

Don't worry about all the doom-and-gloom stuff.
Plug the hole with epoxy that is thickened with something.
Epoxy on a G10 backing pad over the plug.
Good to go.
Make the G10 pad large/thick enough to allow the future mounting of a Groco flange adaptor.

[sailingharry]

Consider this. Entire small boats are made of 1/8 thick glass construction. This hole is not "structural." The purpose of this patch is to keep water out. Grind a 3" diameter 1/8" deep dish on either side (in and out). Fill the outside with a series of glass disks. At this point you are seaworthy. Then go inside, fill the hole, and top with another series of glass disks. You now have a patch that is clean, neat -- and hundreds of times stronger and more durable than the perfectly adequate speed sensor you removed.

The 12-1 adage is appropriate for structural repairs, such as the 4' long sugar scoop my father added to his boat.

A question for those that recommend a 30" diameter repair for a 1" diameter hole. The skins on my boat are maybe 1/8" thick. Why does a patch in my hull require a 2" overlap, but the same repair on his boat a 16" overlap?

[Chotu]

Originally Posted by sailingharry

A question for those that recommend a 30" diameter repair for a 1" diameter hole. The skins on my boat are maybe 1/8" thick. Why does a patch in my hull require a 2" overlap, but the same repair on his boat a 16" overlap?

He he he. Waiting for this response also. Can’t wait to see the answers

But the rest of this post that I deleted, pretty much nailed it. The purpose of making the concave grind out and re-glassing at a slow slope away from major chunks missing in a hull is to reduce stress risers as the hull flexes. It’s to tie in the various layers of glass and allow the original structure and the repair to bend at the same rate. (Thanking god I don’t have one of those hulls)

In 1.25” thick solid glass right next to the keel, that just isn’t happening. If this area is flexing a lot, it’s time to cut the boat up and put it in the landfill.

Harry also makes another good point. This is just to keep water out. Being extreme, to prove the point, he could just fill it up with 5200 and be done as well. Or hammer a wooden bung or cork in.

But the epoxy will work also.