How to fix gap in side of fiberglass hull

[aaronhl]

You can see I have the coring out and the opening exposed to the fiberglass (with more grinding to do). What advice on how to fix from the inside or out would you have for me? I was planning on putting a board out the outside and building gelcoat and fiberglass from the inside before putting new core in. What do you think?

 

[fallguy]

1. Remove all the loose stuff or any fibers not in original matrix.

2. Grind a 12:1 taper into the existing core on the outside.

3. Cut the inside big enough to fit a wood backer faced with shipping tape on the inside of the outside.

4. Glass the outside with 1708 to just enough room for gelcoat.

5. Remove backer. Skin the inside with 3 big to small patches of 1708.

6. Grind the 12:1 taper on the inside.

7. install a stay in place backer(s); something you can pull into bonding putty with screws from face and let it cure

8. Remove screws and repair inside as needed.

 

[wet feet]

Fix from the inside,its half the work.Grind a taper from the inside to the outside because you are headed for the same process the original builder used.Make sure all damaged material is removed and then you need to pull the torn edges back into alignment.For a surface with simple curvature in one plane,I find 1/4" plywood with a melamine facing applied to be a really useful material and would add it where possible by means of self tapping screws.For the region below the swelling into the hull joint flange it might be simplest to use self adhesive sheet wax to create the most faithful representation of the original shape.

Double gel and build up the laminate in stages.Allow the first couple of plies of CSM to cure before introducing biax to the mix as it will minimise the risk of print through and then just replicate the original laminate.The more faithfully you can replicate the original shape-the easier the finishing will be.If the double thickness gelcoat doesn't allow for a perfect surface you may have to apply more from the outside.On no account should you expect to get a good finish working from the outside,it won't happen and will take many hours of work to get anywhere close.

 

[aaronhl]

Very good thanks for the helpful replies

It might be tricky keeping the parts steady as I screw the board on because it's about 1/8" off

Possibly delicate tapering from the inside as I approach the existing gelcoat

Those are my initial thoughts. I think the fiber glassing will be the easy part once everything is prepared properly.

 

[ondarvr]

A slight variant in the procedure.

Grind from the inside but don't be concerned about removing every bit of damaged glass, you want to retain as much of the original shape as possible. And don't be concerned about the outside other than to force it back into the original shape, or as close as you can get it.

Grind 90% of the way through from the inside and apply several layers of glass on it. Gel coating from the back side is OK, but 90% of whatever you put on there will either be buried under more glass, or sanded off to get the right shape.

Once the inside laminate is hard you can pull off the wood or whatever you used on the outside and grind off the rest of any damaged glass and get it to line up better. You actually do want a complete, but relatively thin laminte on the outside. Without a good laminate on the outside any future stressing of the repair may create cracks in the gel coat or fillers.

The outside repair is 90% cosmetic, the inside repair is 90% structural.

 

[wet feet]

I may be slightly at odds with ondarvr here because when i have to do something of this nature I will happily spend a day or two aligning the surfaces before creating my temporary mould for the missing section.I also take the time to create the most faithful female version of the missing area and give it the best finish that can be achieved in a reasonable time,which is why I line a satin or gloss Formica facing for the temporary mould.I do this because it eliminates almost all of the finishing process on the outside, there may be small amount of blending at the periphery of the hole that has been filled but it is an order of magnitude less that having to create a quality finish while working from the outside.I see little need for a big taper on the core since they would have butted sheets of core material when the boat was built,but I would make sure that the inner skin joint was 4-5 inches at least from the outer joint and I would avoid sharp corners in either location,and probably straight lines if that were feasible.

 

[ondarvr]

I didn't say don't try to align the surfaces, I said gel coating it on something of this nature doesn't help much.

The reason is that not having a laminate over the outside leaves it vulnerable for more cracking in the future. Fillers surrounding a repair like this aren't that crack resistant

As for not gel coating it in the beginning, you will end up respraying the entire surface no matter how you fix this damage. So that step doesn't help much at all.

 

[wet feet]

It may be different cultures,I've been around boatyards since the 70's and have seen gel sprayed on the outside of exactly one boat.We tend to repair from the outside in and expect the finishing to extend just a tiny bit from the point where old meets new.For a boat that is still in production it might be possible to arrange for a local section to graft in but preparing the best representation of the outside and duplicating the original manufacturing sequence is pretty normal.

 

[ondarvr]

I'm a little confused by your answer, but not really. You're in the UK, spraying gel coat there is somewhat uncommon, here it's done every day.

I did this type of work for decades, starting in the 1960s, then traveled globally doing it later.

By the time you've spent two days lining up the outside and gelcoating the surface, I've completed the inside repair and moved to getting the outside faired. The outside needs to be touched up (resprayed) either way, you can't get a perfect gel coat job on this size of repair from just the inside. As the job scales up in size it might be beneficial to pre gel coat it depending on the type of damage.

On this job I might be wrapping up the final touches at the end of day two, I'm not talking about the other damage to the gunnel or sole.


A laminate covering the outside of this repair is important, which means it needs to be sprayed or have gel coat applied in some fashion after all the glass has been laid down.

 

[aaronhl]

So ur saying ideally you want to repair with glass on the inside and also the outside, that way the new gel might not crack as much ?

 

[ondarvr]

Yes

 

[aaronhl]

OK Good I feel most of the repairs Ill start on the inside, starting with the gelcoat... hopefully with enough flushness to the original hull looking from the outside. From there I can grind into the hull from the outside in a way that can make the repair fair to the original maybe using only some matt - I don't plan to respray the whole boat, or even the side, so an attempt to color match or inability to see the repair from 20 feet away would be good enough for me

Thanks for everyone help I can see how ill do this only waiting for the weather temperature to get high enough

 

[aaronhl]

Fix from the inside,its half the work.Grind a taper from the inside to the outside because you are headed for the same process the original builder used.Make sure all damaged material is removed and then you need to pull the torn edges back into alignment.For a surface with simple curvature in one plane,I find 1/4" plywood with a melamine facing applied to be a really useful material and would add it where possible by means of self tapping screws.For the region below the swelling into the hull joint flange it might be simplest to use self adhesive sheet wax to create the most faithful representation of the original shape.

Double gel and build up the laminate in stages.Allow the first couple of plies of CSM to cure before introducing biax to the mix as it will minimise the risk of print through and then just replicate the original laminate.The more faithfully you can replicate the original shape-the easier the finishing will be.If the double thickness gelcoat doesn't allow for a perfect surface you may have to apply more from the outside.On no account should you expect to get a good finish working from the outside,it won't happen and will take many hours of work to get anywhere close.

Do you think the polyester will melt into these sheets? Or do you have a better item?

Amazon.com https://www.amazon.com/Self-Adhesive-Laminating-Machine-Sealing-Laminate/dp/B0C2HR12RJ/ref=sr_1_2_sspa?crid=3UILBRMIMALT0&dib=eyJ2IjoiMSJ9.j6bNivF4Sx_ZBit24uuvdgz_CFizJ9Ps0a7-zIuhgh4s4c3OWto-Paqrke3gPz4TOrkKOdztZiyxKR4zsu29B72YhvVbkiCXC2G9E89TuGnniWBshOH7c35PkHY0Kw1V2S-NAA76JmLsU2q4IlB73m3gn7M3oljyiJcVMeG97dFTBq7dWjzOmy5Joto_JCQn1RE3CQcecoxnJyJ5KDgNkkPorSfQ1OdU-yGJSyfab4cEqmBp5tLvfNOYCh9ccE8c-JkxKTuk9RYmbjK6JD-5Lhn7C0VFjQkYfzv7BeXxCdQ.3lpF7m019LBHSdMakkkYHqcbvvU4lpmX-IrDBQhG_-k&dib_tag=se&keywords=self%2Badhesive%2Bsheet%2Bwax&qid=1745415487&sprefix=self%2Badhesive%2Bsheet%2Bwax%2Caps%2C236&sr=8-2-spons&sp_csd=d2lkZ2V0TmFtZT1zcF9hdGY&th=1

 

[ondarvr]

How do you plan to use those?

 

[wet feet]

I see no conceivable use for those laminating sleeves on this job.I have attempted to attach a sketch of what you need to work toward.I recommend generous separation of the various joint lines and gradual tapers,where tapers are needed.The replacement core will need to be bedded on some kind of paste that will deal with unevenness and efforts made to eliminate voids in this region.