Gelcoat Repair - Confused

[PGHMAN]

Ok, working on my winter project that I picked up a few weeks back and need to do a repair on the hull. As seen in the pic the gelcoat is missing in front and under the right sponson. Damage is approx. 5"x2" and depth at the lowest point is under a 1/4". The fiberglass is solid.
The more research the more confused. I know the prep that needs to occur but I am confused on whether I should fill the gouge prior to gelcoat due to the depth. Some say Marine Tex can be gelcoated and others suggest a poly filler or just gelcoat?
Any experience to offer would be appreciated. Thanks.

 

[Strizzo]

fill with fiberglass/resin then sand down below the level of the original gelcoat, apply new gelcoat.

i do not envy you my friend.

 

[Krispy]

Have a look at my thread on gelcoat repair.


The basic gist is that you need something to fill the damage to bring it up the the level of the surrounding areas. Since it is gelcoat that has been removed and not glass, you could get away with just gelcoat.

Basic steps:

1. Pick away at the loose gelcoat at the perimeter of the damage, ensure the fiberglass is not retaining any moisture.
2. Clean area with acetone
3. Mix gelcoat:
a. Gelcoat
b. hardener
c. surface wax
d. pigment to match the yellow
4. Apply gelcoat, I prefer to "overfill" the area, leaving a high spot.
5. Let it cure/harden
6. Sand flat and polish the whole hull to blend.

The pitfalls of this method are with step 3, it is very difficult to get the color to match to the OEM aged yellow. This is why I decided to do my entire hull black instead of yellow. I had many more spots to treat than you did. And most of them had been sanded smooth with the bottom of the hull from beaching. In the areas that I had that were just chipped away gelcoat, I actually used a fiberglass filler (bondo brand, but made for marine applications, no talc filler like automotive bondo) And then covered the whole area with gelcoat. Looking back on the situation I could have counted on the gelcoat acting as more of a filler than I was giving it credit for.

Marine TEX is one of the easiest and least expensive ways to fix the problem, if you can live with a "repaired" white spot in that area I would go that way.

Feel free to ask any questions and we will do our best to help!

 

[PGHMAN]

fill with fiberglass/resin then sand down below the level of the original gelcoat, apply new gelcoat.

i do not envy you my friend.

Any recommendation on a fiberglass resin? Not a poly resin? I am not familiar with gelcoat characteristics but it appears that is more like a paint viscosity and would be difficult to mold around the edge and the depth I need to acquire to be flush. That's why I think a filler then gelcoat.
Color match is not critical being most of area will be covered by the sponson and below the water line.

 

[jammin777]

hi rob, gel coat is much thicker than paint to it can be built up a bit higher. then sand using 280 grit to get it smooth and flush, the work your way to 1500 grit the machine buff, polish and wax. sanding gel coat is much like sanding bondo heres where i got my gel coat from the suppliers of seadoo.
http://www.gelcoat.ca/index.php?p=catalog&parent=2&pg=1

my gel coat repair thread http://www.seadooforum.com/showthread.php?67577-99-seadoo-gsx-rfi-semi-restro/page2

 

[Krispy]

Any recommendation on a fiberglass resin? Not a poly resin? I am not familiar with gelcoat characteristics but it appears that is more like a paint viscosity and would be difficult to mold around the edge and the depth I need to acquire to be flush. That's why I think a filler then gelcoat.
Color match is not critical being most of area will be covered by the sponson and below the water line.

Gelcoat is much thicker than paint, and should be applied as such.

If you fill the area to be flush with the surroundings and then apply gelcoat you will have a raised area as the gelcoat has thickness on top of the now flat surface. If you are covering the whole bottom of the hull like I did it isn't as big of a deal.


As for filler this is what I used

Yes it is marketed under the name "bondo" no it is not traditional bondo. I have exchanged several emails with 3M (Bondo's parent company) about the compatibility with gelcoat and moisture and they are completely compatible.

People have the image of "bondo" being this horrible pink filler that is used in half azz body shops, this product couldn't be further from that.

The only thing this has in common with the old pink body filler is the name.

 

[PGHMAN]

Hi Kevin - can I build it up to a 1/4 inch? Seems excessive that's why I am thinking a filler first. When's the camping trip? I am taking off tomorrow since weekend forecast calls for rain again - 3 weeks since I've been out....killing me!

hi rob, gel coat is much thicker than paint to it can be built up a bit higher. then sand using 280 grit to get it smooth and flush, the work your way to 1500 grit the machine buff, polish and wax. sanding gel coat is much like sanding bondo heres where i got my gel coat from the suppliers of seadoo.
http://www.gelcoat.ca/index.php?p=catalog&parent=2&pg=1

my gel coat repair thread http://www.seadooforum.com/showthread.php?67577-99-seadoo-gsx-rfi-semi-restro/page2

 

[jammin777]

1/4" seems excessive for sure, couldn't tell from the picture but i agree, filler first.
i leave tomorrow and will be back next Thursday. going to take a spare tps sensor and test tools with me just in case! i hope you get to ride again soon.

 

[PGHMAN]

Gelcoat is much thicker than paint, and should be applied as such.

If you fill the area to be flush with the surroundings and then apply gelcoat you will have a raised area as the gelcoat has thickness on top of the now flat surface. If you are covering the whole bottom of the hull like I did it isn't as big of a deal.


As for filler this is what I used

Yes it is marketed under the name "bondo" no it is not traditional bondo. I have exchanged several emails with 3M (Bondo's parent company) about the compatibility with gelcoat and moisture and they are completely compatible.

People have the image of "bondo" being this horrible pink filler that is used in half azz body shops, this product couldn't be further from that.

The only thing this has in common with the old pink body filler is the name.

Krispy, thanks for the info. Does the bondo that you recommend material sand smooth to apply the gelcoat. I see that you and Jammer sprayed. I have a gun and compressor and can spray but can it be applied via foam brush or best sprayed? Pardon my ignorance on gelcoating.

 

[PGHMAN]

I bet your itching to find out how the ski rides!!! I wish you the best! Wondering, you spoke of a person named Dennis from the Candoo forum. Are you referring to Dennis - one of the owners?

 

[PGHMAN]

1/4" seems excessive for sure, couldn't tell from the picture but i agree, filler first.
i leave tomorrow and will be back next Thursday. going to take a spare tps sensor and test tools with me just in case! i hope you get to ride again soon.

I bet your itching to find out how the ski rides!!! I wish you the best! Wondering, you spoke of a person named Dennis from the Candoo forum. Are you referring to Dennis - one of the owners?

 

[soccerdad]

Any recommendation on a fiberglass resin? Not a poly resin?

Some notes on gelcote, "fiberglass resin" Poly, etc. For these skis, all of it uses polyester resin. Note that Epoxy resin is a completely different material. The gelcote is just a thick version of polyester resin. It has some other fillers to up the viscosity and allow you to sand it smooth. "Fiberglass" resin is just polyester (poly) resin. Polyester resin is usually used to make laminates with fiberglass. The fiberglass is the specific structural material that gives the ski the strength. It is the white itchy stuff. Fiberglass comes in assorted woven fabrics and non-woven mat materials. The fabrics are typically stronger than the mat materials. The mat materials are usually used a bulking filler between layers of fabric. Many skis and boats use what is called a chopper gun to spray glass strands and resin at the same time into a mold. This makes quick boat building. Often then glass cloth is added in areas that need extra strength. Chopper guns are not a home use thing though. BTW, Bondo is also just polyester resin with a ton of fillers in it.

Finally polyester resin comes in two basic forms. One is for laminating (making structural things) and the other is for surface coating (like the top of a repair inside your hull, or on the deck of a surfboard). Laminating resin never fully hardens on the surface in the presence of air. So surfacing resin has wax added to allow it to fully harden. If you are doing multiple layers, you do not want the wax in there since it will act as a release agent when you go to put the next layer on and make your laminate weak.

So bottom line in normal language: Use the non wax polyester resin for doing structural repairs. Use the surfacing wax resin if it will be your top layer (or put some wax paper on it to allow the surface to harden). Use gelcote for an exterior surface of the hull that you want to sand down to match the existing hull.

From what you describe, I would fill the void area up some with laminating resin and glass cloth or mat. Then top coat with gelcote. As long as the area is still strong and just needs filler, then use bondo to fill it some and top with gelcote.

Let me know if you have any questions. I know this can be confusing. I spent several years as a composites process engineer and have made a host of "fiberglass" and carbon fiber parts and molds.

 

[Sportster-2001-951C-Stock]

Good post Soccerdad, this is absolutely the case!

 

[jammin777]

I bet your itching to find out how the ski rides!!! I wish you the best! Wondering, you spoke of a person named Dennis from the Candoo forum. Are you referring to Dennis - one of the owners?

yep dennis from the candoo forum great guy and support! kinda nervous as i want it to run good, well it runs good just need it to fire up good lol!

 

[soccerdad]

Two additional things to help the knowledge base.

First, the skis are built backwards from the repair process. The gelcote is sprayed into a mold, then the glass is built up giving the smooth hull and rough inside of the ski.

The polyester resin really is based on styrene. So styrene can be added sometimes during processing. Also, that is why you never want to use polyester resin with Styrofoam. The resin will just dissolve the Styrofoam. You can use urethane foam as a reinforcement (like in a surfboard) to give you great strength with very low weight.

Carbon fiber and Kevlar parts just use carbon or Kevlar fabrics instead of the glass fabrics to make a laminate. And yes, fiberglass is really glass, just like in your windows, that is spun into small fibers. Typically carbon fiber or other advanced materials are used with epoxy resin since it is much more stable dimensionally, and has higher impact strengths.

 

[jammin777]

a foam brush should be fine being that its a small repair area. make sure that when you fill it with what ever material that you leave low so that you can build it up with gel coat and contour sand after gel coat is applied otherwise you will end up sanding the gel coat off. you probably already knew that.

 

[Krispy]

a foam brush should be fine being that its a small repair area. make sure that when you fill it with what ever material that you leave low so that you can build it up with gel coat and contour sand after gel coat is applied otherwise you will end up sanding the gel coat off. you probably already knew that.

This, it works either way. Spray is a better finish, but foam is easier.

MarineTex is cheap and functional but has poor appearance on anything but white.

 

[PGHMAN]

yep dennis from the candoo forum great guy and support! kinda nervous as i want it to run good, well it runs good just need it to fire up good lol!

Dennis is a local guy near me and I had the opportunity to meet him in early June when I was having my bogging issue. I met him at our local lake during his camping weekend and he inspected my ski and he hooked up his Candoo and analyzed my TPS which was he indincated was spot on.
A real stand-up guy....anyone that would take time from a family camping trip to help a stranger for over an hour is tops in my book! I did compensate him for his time and have reached out to him several time since.
Again, good luck this weekend! Let us know how it performs.

 

[PGHMAN]

This, it works either way. Spray is a better finish, but foam is easier.

MarineTex is cheap and functional but has poor appearance on anything but white.

My research shows that gelcoat should not be applied to MarineTex correct? I should go with a poly base filler like the Bondo glass, right?

 

[PGHMAN]

Some notes on gelcote, "fiberglass resin" Poly, etc. For these skis, all of it uses polyester resin. Note that Epoxy resin is a completely different material. The gelcote is just a thick version of polyester resin. It has some other fillers to up the viscosity and allow you to sand it smooth. "Fiberglass" resin is just polyester (poly) resin. Polyester resin is usually used to make laminates with fiberglass. The fiberglass is the specific structural material that gives the ski the strength. It is the white itchy stuff. Fiberglass comes in assorted woven fabrics and non-woven mat materials. The fabrics are typically stronger than the mat materials. The mat materials are usually used a bulking filler between layers of fabric. Many skis and boats use what is called a chopper gun to spray glass strands and resin at the same time into a mold. This makes quick boat building. Often then glass cloth is added in areas that need extra strength. Chopper guns are not a home use thing though. BTW, Bondo is also just polyester resin with a ton of fillers in it.

Finally polyester resin comes in two basic forms. One is for laminating (making structural things) and the other is for surface coating (like the top of a repair inside your hull, or on the deck of a surfboard). Laminating resin never fully hardens on the surface in the presence of air. So surfacing resin has wax added to allow it to fully harden. If you are doing multiple layers, you do not want the wax in there since it will act as a release agent when you go to put the next layer on and make your laminate weak.

So bottom line in normal language: Use the non wax polyester resin for doing structural repairs. Use the surfacing wax resin if it will be your top layer (or put some wax paper on it to allow the surface to harden). Use gelcote for an exterior surface of the hull that you want to sand down to match the existing hull.

From what you describe, I would fill the void area up some with laminating resin and glass cloth or mat. Then top coat with gelcote. As long as the area is still strong and just needs filler, then use bondo to fill it some and top with gelcote.

Let me know if you have any questions. I know this can be confusing. I spent several years as a composites process engineer and have made a host of "fiberglass" and carbon fiber parts and molds.

SoccerDad, great info! The deepest area of my damage is approximately 3"x1" and is about 1/4" deep. Thus the need to apply the filler then topcoat. I am still confused on what material to use for the filler...it needs to be poly based and not epoxy based, right?

 

[Krispy]

My research shows that gelcoat should not be applied to MarineTex correct? I should go with a poly base filler like the Bondo glass, right?

That is correct, MarineTex is not to be used as a pre gelcoat filler. It is a solution that requires no gelcoat. I have heard it is a bit difficult to sand, but gelcoat Has it's own difficulties.


Sent from my iPhone using Tapatalk

 

[soccerdad]

Yep, I would use the bondo product to fill it. The MarineTex is epoxy. The polyester gelcote will not stick to it as well as it does to the polyester based bondo. Then the gelcote over it. As Krispy said, make sure the fill is lower than your desired final surface level by about 1/16" or a little more. Then apply the gelcote to as close to the final surface as possible, while leaving it a little high. The material should not run, but if you have problems with it running, you can use wax paper to stabilize it as it cures. You then can just peal it off. Let it fully cure, then sand. It is tough stuff. Use a sanding block and make sure you do not sand through the existing gelcote near the repair. Take your time and it should work great! Good luck! And take some pictures as you do it. BTW, if you find you need to build up the gelcote some more, just make sure the surface has been sanded slightly to get rid of any wax on the surface if you are using a waxed gelcote.

 

[Krispy]

[MENTION=66002]PGHMAN[/MENTION]

How is the project coming along? Any updates?

 

[PGHMAN]

[MENTION=66002]PGHMAN[/MENTION]

How is the project coming along? Any updates?

Hi Krispy - no update on the hull repair. Had a crappy weekend weather wise in Raleigh and decided to rebuild the carbs opposed to working on the hull. Plus I need to make a trip to West Marine for filler and gelcoat.
Still confused on the filler. West Marine sells 3M Marine filler which I believe should do the trick...again the area to be filled is only about 3"x1"x1/4" then top it with gelcoat.
I was planning to purchase the EverCoat gelcoat repair kit and mix the color. I am not overly concerned with a precise match since most of the area will be covered by the sponson plus below the water line plus trying to keep within budget.
Ever use the EverCoat gelcoat kit?

 

[Sportster-2001-951C-Stock]

Yep, I would use the bondo product to fill it. The MarineTex is epoxy. The polyester gelcote will not stick to it as well as it does to the polyester based bondo. Then the gelcote over it.

This is correct, gel coat will not reliably adhere to epoxy but epoxy will adhere tenaciously to gel coat and polyester resins. Polyester resins cannot be applied over epoxy. There are other choices for applying a finish to epoxy and gel coat isn't one of them.

I've used white epoxy appliance paint for white hulls many times and pleased with the results.