Gelcoat repairs - small patches and lots o' spiders

[erikgreen]

I'm going to start a new thread soon (two boat threads running at once, a sure sign of MBS) for my new "project" which is a 1961-ish Buehler Turbocraft jet boat.

It's a super pretty, probably very fun, historically important boat (first production jet boat, same model owned by Jackie Kennedy, magazine articles written about it, etc).

So I'm pretty sure I'd be able to sell it for a bit if I restored it, plus the restore would be fun (simple drivetrain sooo much easier than I/O mechanicals). But the parts are worth a bit themselves... classic engine, etc. Plus I could spend next winter restoring a classic car instead, which I need (all I have to drive at the moment is my tow pickup, which isn't getting me a lot of dates

Before I make that decision, I need to ask the collective wisdom here about fixing the gelcoat. Due to the desire to restore the boat to original condition, I don't want to paint the hull, I want to match and restore the original gelcoat color.

The problem with this is that the boat is old, and while the gelcoat is in generally good shape (no delaminations, blisters, major sections missing) it has a lot of spider cracks all over the hull, possibly due to flexing after the stringers/structure rotted. It has a few small locations missing due to impacts of branches, etc in storage on the cap, too.

What I'm thinking I'd want to do is remove any major sections of spidered gelcoat, (where the cracks go down to the glass) and sand other spidered areas, plus clean up the hull in general to remove any loose gelcoat. I'd repair the underlying glass as needed. At some point in parallel with this I'd repair the interior structure of the boat, probably creating or needing to repair some more gelcoat holes in the process.

Then I would plan on buying some good quality gelcoat and hand color matching the hull's polished color (I'd have to polish a section) and using arbourite or plastic molds and to mold the replacement coat in place, then fair and polish that. Then I'd re-attach the hardware and hopefully have a nice, shiny boat.

Since I've never done significant work with gelcoat, I need some idea how well this would work - I know it's not easy to make the patched hull shiny and fair, or match the color of 50 year old faded gelcoat, but if I did this:

* Do I need to go down to the glass everywhere, or will gelcoat stick to sanded gelcoat enough?

* Will new gelcoat stick to the underlying glass well enough to last a while?

* Can anyone predict any gotchas of doing this?

* I'm operating on the assumption that a "restored" boat should be the original color without paint. Or would it be ok to give it a quality paint job instead?

* Or should I try to find a gelcoat patch compound made with epoxy instead?

Any thoughts appreciated,

Erik

 

[ondarvr]

Re: Gelcoat repairs - small patches and lots o' spiders

I answered in the quote.

I'm going to start a new thread soon (two boat threads running at once, a sure sign of MBS) for my new "project" which is a 1961-ish Buehler Turbocraft jet boat.

It's a super pretty, probably very fun, historically important boat (first production jet boat, same model owned by Jackie Kennedy, magazine articles written about it, etc).

So I'm pretty sure I'd be able to sell it for a bit if I restored it, plus the restore would be fun (simple drivetrain sooo much easier than I/O mechanicals). But the parts are worth a bit themselves... classic engine, etc. Plus I could spend next winter restoring a classic car instead, which I need (all I have to drive at the moment is my tow pickup, which isn't getting me a lot of dates

Before I make that decision, I need to ask the collective wisdom here about fixing the gelcoat. Due to the desire to restore the boat to original condition, I don't want to paint the hull, I want to match and restore the original gelcoat color.

The problem with this is that the boat is old, and while the gelcoat is in generally good shape (no delaminations, blisters, major sections missing) it has a lot of spider cracks all over the hull, possibly due to flexing after the stringers/structure rotted. It has a few small locations missing due to impacts of branches, etc in storage on the cap, too.

What I'm thinking I'd want to do is remove any major sections of spidered gelcoat, (where the cracks go down to the glass) and sand other spidered areas, plus clean up the hull in general to remove any loose gelcoat. I'd repair the underlying glass as needed. At some point in parallel with this I'd repair the interior structure of the boat, probably creating or needing to repair some more gelcoat holes in the process.

Then I would plan on buying some good quality gelcoat and hand color matching the hull's polished color (I'd have to polish a section) and using arbourite or plastic molds and to mold the replacement coat in place, then fair and polish that. Then I'd re-attach the hardware and hopefully have a nice, shiny boat.

Since I've never done significant work with gelcoat, I need some idea how well this would work - I know it's not easy to make the patched hull shiny and fair, or match the color of 50 year old faded gelcoat, but if I did this:

* Do I need to go down to the glass everywhere, or will gelcoat stick to sanded gelcoat enough?

1. Answer, you only need to get down to the glass in areas where the cracks get to the glass, gel coat sticks to gel coat very well.

* Will new gelcoat stick to the underlying glass well enough to last a while?

2. It may only last for another 50+ years, so what do you mean by a while?

* Can anyone predict any gotchas of doing this?

3. Just lots of work.

* I'm operating on the assumption that a "restored" boat should be the original color without paint. Or would it be ok to give it a quality paint job instead?

4. It should be gel coat.

* Or should I try to find a gelcoat patch compound made with epoxy instead?

5. Epoxy products doesn't hold up well in UV light and gel coat won't bond to it, so don't use it.

Any thoughts appreciated,

Erik

 

[erikgreen]

Re: Gelcoat repairs - small patches and lots o' spiders

Cool, thanks. This whole boat would be a lot of work, but it's a quality craft to begin with, and I'm thinking the restore would be well worth doing. This does not seem to be a "pig with lipstick".

I just need to decide if I want a car more, and if so do I want to store this boat in the meantime. I have to keep everything indoors because the local code enforcement are jerks, so that's half of my detached garage gone.

I'll post a thread with some pics soon to share, but if I decide to do the restore I won't start that for a while. I might clean it out, get some waterlogged wood out, and pickle the engine (Marvel mystery oil) though.


Erik

PS: Only 50 years? So when the boat is twice its current age I'll have to do this again? Man.....

 

[KurtG]

Re: Gelcoat repairs - small patches and lots o' spiders

Do you think you have true spider cracks or surface crazing? With your description of spider cracking, I'd wonder how brittle the gel may be in other areas from weathering/UV exposure. If there are indeed issues with the layup/flexing, then any weathered gel you don't address may also crack whether new repair or even painting. If it was just surface crazing, I'd be less concerned with a patch job.

I think you're going to want to take care of the stringers and deck first as to prevent any further stress cracks if that is indeed what they are.

Hand coloring was the toughest part of the gel repairs for me. Make sure you measure the tinting and color enough resin to complete the project. I now have enough pre-colored resin to complete additional repairs at a later date. The first two batches I tried to replicate based on the drops of colorant added to the mixing cup, but it didn't work well. I then colored all my resin and all subsequent batches have matched.

It's not not clear to me from your description why you need to mold the gelcoat in place. I guess I'd use gel paste in areas that appear to need molding.

 

[erikgreen]

Re: Gelcoat repairs - small patches and lots o' spiders

I guess I was thinking molding would be the easiest to get fair, and save at least some sanding.

In places I'll have to go down to the original glass layup, which means a 1/8" or so thickness of gelcoat, which I would think would run if I just sprayed it in place? Like I said, I've never worked with it before, what I know is that it's a good molding compound but not a great glue.

I guess I was thinking I'd make a mold for the hull section I'm coating out of flexible MDF or pressboard and plastic coating, smooth, then apply gelcoat and cover with the mold to let harden. I do something like this now with hull repairs, and I get a very smooth patch that requires little sanding to be invisible (under paint, of course).

I'm not 100 percent sure about the origin of the cracks. I can say they are mostly on the white part of the boat, the hull, and in many areas are parallel to either the gunwale or purely vertical, this leading me to believe they're not just crazing. The blue deck is mostly free of cracks, it just has a few chips. There are areas of the hull sides that are crack free too, amidships.

I'll post pics in another thread later tonight if I can, to let you see what I'm dealing with.

Erik

 

[ondarvr]

Re: Gelcoat repairs - small patches and lots o' spiders

Making a mold to achieve the shape and reduce sanding would be very difficult and require far more work than just fairing the surface will.