Fibreglass repair?

[OVERKILL]

Not automotive related.

We recently picked up (as in yesterday) a ski boat for the cottage. It's a 1995 Supra Com TS6M with the 310HP Ford GT40 EFI 5.8L 351W in it. Being a 1995, it has the composite stringers, not wooden ones found in the late 80's early 90's ones. Hull looks in excellent condition from the outside and from what one could see of the bilge.

Now, I cleaned out the bilge yesterday with some dawn to get all the gunk out of it and discovered about a 2' long crack underneath the engine, about 1" out from the left stringer that had been concealed by the filth. It is not a through crack, and appears to be on a bit of an angle. No idea what would have caused it, as there's no signs of trauma on the bottom of the boat anywhere

My question is, those of you familiar with repairing marine fibreglass, is this just a situation where one would ensure it is clean and try and shove some resin in it, or would you try and force some mesh down in there first? It's not very wide. The hull is supposed to be a kevlar/fibreglass composite so this kinda surprises me but I'm guessing it could be a flex crack from hitting some large waves?

 

[BrocLuno]

Gotta determine the nature of the crack. Take it out for a run with the engine compartment open. Watch the hull react as you cross waves at various angles. It's prolly the mass of the engine and hull flex. But it may be corkscrew flexure of the hull ...

You can't shove anything in there w/o knowing how it originated and how it's acting. So do the investigation and then we'll figure out what to do?

Once you know the nature of the flex, you can address the issue properly. Prolly means Vee'ing out the crack, filling with a matrix resin solution and overlaying a beefier fillet. Maybe with some reinforcement from the stringer outward to spread teh load. Not a big deal, but it can be work.

Almost guaranteed that it has oil mist in the crack, so nothing will bond without thorough cleaning and exposure of new faces. The bummer is that as you grind out the new faces and lay back the crack, IF there is any oil present, the grinder will just broadcast it onto the new exposed surfaces and you still won't get a bond.

Once the issue is figured and the solution designed, it may be a good application for vacuum bagging ...

 

[JTK]

Funny you should mention this. I've been watching my brother fix up his $500, ~1995 model year project. He's probably got $700 and countless hours into it between the floor and some small powertrain stuff, but he loves these type of projects. He knew he was getting into a few soft spots in the floor, but you never know what's going on until you get into it:

 

[Donald]

Resin and fiberglass cloth/mat is like cement and rebar/steel etc.

The strength comes from the combo. Resin by itself has little strength.

If you have never worked with fiberglass before I suggest you mix a cup and apply some fiberglass cloth to a box.

As mentioned above, you need to get it very clean. Disposable brushes.

 

[BrocLuno]

So all polyester resin hulls have release agent present. It's almost as bad as oil for lousing up a joint. It can be washed off with 409 and water. But, like oil, you really have to do a stellar job of cleaning. Any contaminates in your work and you might as well not even try ... It's a waxy substance and it's even easier to spread around than oil ...

 

[OVERKILL]

Originally Posted By: BrocLuno
So all polyester resin hulls have release agent present. It's almost as bad as oil for lousing up a joint. It can be washed off with 409 and water. But, like oil, you really have to do a stellar job of cleaning. Any contaminates in your work and you might as well not even try ... It's a waxy substance and it's even easier to spread around than oil ...


I was going to hit it with brake kleen but it sounds like that won't be sufficient to get the oils out of it. I have an acquaintance who I was unaware actually used to work in fibreglass hull repair, so I may get him to come over and take a peek at it. The boat is currently at home, about 2hrs from the cottage, so I can't really toss it in the lake to observe how the crack responds unfortunately, as per your earlier suggestion

 

[Danno]

Any closer lakes, like Lake Ontario?

 

[maxdustington]

Originally Posted By: JTK
Funny you should mention this. I've been watching my brother fix up his $500, ~1995 model year project. He's probably got $700 and countless hours into it between the floor and some small powertrain stuff, but he loves these type of projects. He knew he was getting into a few soft spots in the floor, but you never know what's going on until you get into it:

My dad has that boat but it's a 1986 Lynx or something!. Merc 140 which is a GM Iron Duke! Same gauges, same throttle. Painted differently, but the blower exhausts are the exact same. That is what tipped me off.

Thanks for the pics, the hull on his boat is getting soft, too.

EDIT: Got excited, his is not a bow rider.

 

[OVERKILL]

Originally Posted By: Danno
Any closer lakes, like Lake Ontario?


Closest are the Kawartha ones actually, but I wouldn't put anything I own in there due to the Zebra mussels.

 

[maxdustington]

Originally Posted By: OVERKILL
Originally Posted By: Danno
Any closer lakes, like Lake Ontario?


Closest are the Kawartha ones actually, but I wouldn't put anything I own in there due to the Zebra mussels.


I have a cottage near Picton. They actually screwed up Lake Ontario, the reptiles dissapeared around the time they showed up was it late 90s? Lake Ontario was pretty polluted during the 2000s too, it is hard to say what really screwed it up so badly, the pollution or the mussels. Man, I remember when the zebra mussels seemed to coat everything that was left underwater. They can really turn your feet to ribbons, it is difficult for me to trust any natural water without something on my feet.

I've never heard of them damaging boats but there is no reason that they would not that I can see. They are not quite as numerous as they once were, but I think are they still there.

 

[OVERKILL]

Originally Posted By: maxdustington
Originally Posted By: OVERKILL
Originally Posted By: Danno
Any closer lakes, like Lake Ontario?


Closest are the Kawartha ones actually, but I wouldn't put anything I own in there due to the Zebra mussels.


I have a cottage near Picton. They actually screwed up Lake Ontario, the reptiles dissapeared around the time they showed up was it late 90s? Lake Ontario was pretty polluted during the 2000s too, it is hard to say what really screwed it up so badly, the pollution or the mussels. Man, I remember when the zebra mussels seemed to coat everything that was left underwater. They can really turn your feet to ribbons, it is difficult for me to trust any natural water without something on my feet.

I've never heard of them damaging boats but there is no reason that they would not that I can see. They are not quite as numerous as they once were, but I think are they still there.


Yeah, that's why I avoid bodies with them present.

We are up in Muskoka, where apparently the water is too acidic for them. We were supposed to get hit by them in the 90's but they never took, apparently they hit the water there and just died

 

[CarbonSteel]

Originally Posted By: OVERKILL
Originally Posted By: BrocLuno
So all polyester resin hulls have release agent present. It's almost as bad as oil for lousing up a joint. It can be washed off with 409 and water. But, like oil, you really have to do a stellar job of cleaning. Any contaminates in your work and you might as well not even try ... It's a waxy substance and it's even easier to spread around than oil ...


I was going to hit it with brake kleen but it sounds like that won't be sufficient to get the oils out of it. I have an acquaintance who I was unaware actually used to work in fibreglass hull repair, so I may get him to come over and take a peek at it. The boat is currently at home, about 2hrs from the cottage, so I can't really toss it in the lake to observe how the crack responds unfortunately, as per your earlier suggestion

In my youth, I spent more time in an industrial fiberglass fabrication shop than I care to remember. You can clean it with acetone and allow it to fully evaporate before starting the repair. It is important that you find the source of the crack so that it does not return. The key to good joint is preparation followed by diligent application of mat and resin while working as much air as possible from the mat as you work it.

 

[Trav]

First you have to determine if its just a crack in the gelcoat or is the substrate cracked? There are different methods of repairing it depending on if it was done with a chopper gun, matting or multi layered cloth.
Repair is pretty straightforward and simple once you know what you are dealing with.

Edit: I found this, it looks fairly comprehensive, may be it helps.

https://www.westsystem.com/wp-content/uploads/Fiberglass-Manual-2015.pdf

 

[maxdustington]

Would you post some pics of the boat and motor please? Pictures of the cracks are optional.

 

[CT8]

I rebuilt the deck and some other repaired on a crashed flat bottom drag boat using The book Trav posted the link to. The book is a necessity !!!

 

[Shannow]

JTK, make sure that your brother saturates that timber with coolant (and boric acid)...it will last forever

 

[NYEngineer]

One thing I do to lay really nice fiberglass is to use a paint roller instead of a brush. It really speeds things up and gives you more time to work. Less air too.
Another thing is to make a tool with 1/4" rod. Bend it so it looks like a paint roller and on the straight part where the roller would go, drill two small holes for cotter pins. Stack washers on the rod like a roller and use a fender washer and then an sae washer, then a fender washer and on and on. Use the cotter pins to keep the washers in place. You stagger the washers like a stack of alternating quarters and dimes. This is fantastic for rolling air out of fiberglass mat. To clean it, let it set up and break the resin off with a hammer.
This tool is commercially available but when I was a kid on Long Island, no one ever had any. It was easier to make them myself. Even used a handle I got from the Snapon man.

 

[Donald]

Clean and sand rough. 6" 15oz finerglass tape. Look at Defender marine, they have a lot of this stuff.

If you have no experience with fibergass cloth and resin, try a small piece on a box or piece of plywood.

 

[AVB]

I also found that paint rollers work well, thanks for the tip on making a roller. I never thought of that. I bought a busted up old Ghenoe that I have been rebuilding, this has been my first experience with fiberglass repair. I should have found the time to finish it over the winter. Summer heat really cuts the working time of the resin, also found that you have to be fast when using cheap plastic drinking cups to mix in. You have to empty them before the bottom melts out.

 

[NYEngineer]

Yeah. Plastic cups are not ideal. I always buy a stack of paper buckets for mixing.