Boat Body Work

[Franko]

Hello Everyone!

I was wondering if anyone knows what is the best product for doing body work on a gel coated fiberglass hull. I just purchased a new 55" Scarab hull and the gel coat finish is very poor..there are scratches and (looks like to me) bad fiberglassing and mold work.

I wanted to know what to use on hull to get it looking good, so I can later paint it, also what type of paint and primer do you recommend for the gel coat?

Any help will be greatly appreciated.

Also, boat has no stringers installed or wood plate on transom, where can I purchase them and how do I glass them in place(I have never done this type of work before ).

Thanks for the help/suggestions,

Frank

 

[Altimat]

Sounds like a very typical fiberglass product. Here's what I do. Wash (scrub) the hull with comet and warm water very well. Spray a light mist coat ("guide coat") of dark primer over the entire hull. THis shows flaws and makes sanding easier and quicker. Sand with 150 wet or dry until all scratches are sanded out. Deeper flaws may remain. To repair these, feather them out and fill with a fine textured polyester body finishing filler. Finish to 150 grit. Clean hull with wax and grease remover then prime with a good urethane primer-surfacer. Use a respirator and excellent ventilation. 2 coats should suffice. Guide-coat the primer. Wet-sand with 400 wet, then finish with a light sanding with 600 wet. Paint with automotive urethane also.

If you need a transom doubler, trace the transom on your plywood, cut it out 1/8" undersize all around, then radius the transom side of all the edges. Trim and fit to hull. Sand inside of transom smooth with 36, then 80 grit. Brush the inside of the transom and the inside of the doubler with a heavy layer of epoxy. Install and clamp. Clean up edges and make fillets with the excess epoxy.

Cut your stringers to accomodate your engine mount and its location. Install mount to stringers. Add one or more additional 5" spacers between the stringers to maintain accurate spacing. Center, trim and install parallel in hull with a bead of epoxy on the mating edges. Leave nice fillets behind. Allow that to set. Cut two 1.5" strips of glass cloth or mat to reinforce the joint. Coat the seam 3/4" to either side of the joint with epoxy and lay on the strips. Brush with additional epoxy to just saturate the cloth. Additional resin is dead weight. Reinforce the stringer-to-transom and doubler-to-hull seams the same way if desired. The key is to have a nice 1/4" min. fillet in the inside radiuses first so that the glass will curve around the corner without pulling away and trapping air. When the reinforcements are applied coat the remaining raw wood with epoxy to seal.

Hope this helps!

 

[Franko]

Altimat,

I wanted to thank you for your answers to my questions and sharing your knowledge with me.

As you can tell I am new to boat building and setup/prep and all the help/advice I can get is appreciated.

I dont own a compressor, so can I purchase the dark primer that you recommended in spray cans?...Also, the urethane primer surfacer that you speak of, does that also come in spray cans?

Where can I get birch or marine grade plywood for my stringers and transom?

Should they be coated with something before I epoxy/glass them in?

You dont happen to live in Florida, do you?...LOL

Thank you very much for the help and advice.

I will try to follow your instructions and see how the boat comes out.

Best Regards,

Frank

 

[Altimat]

You can use model primers and paints commercially available with satisfactory fuel-proof results. I suggest finding a small body shop that might apply an acrylic urethane primer coat so you can spray the colors. Then bring it in again for an acrylic urethane clearcoat application after the color coats.

I use model aircraft birch plywood available from local hobby shops. I coat the wood after it is installed, and usually immediately after the final layups of reinforcing glass and with the same batch of resin.

No, I live in WI.

 

[PondSkimmer]

WOW Altimat sound like you have worked in a shop or two. I did body work for quite some time and you are absolutly right.

Novoa, if i were you the best bet is to look for a body shop to prime the boat with the 2K primers that he spoke about then take it back form them sand with 400 then 600 grit wet sand paper. Clean it off, do the tape work (if there is any) and give it back to them for the final paint. when you get it back you can sand out any minor imperfections with 1200 then 2000 grit wet sandpaper and polish with compound and a buffing wheel.

If you work with the shop and do all the labor (sanding and filling) you can save alot of $ they charge $65 per hour here in NY so you could immagine how quick it adds up!

Good luck!

 

[GTR]

Hi Guy's

While great advice on how to get things done the only point I would make is determine if the hull is polyester or epoxy first and use that f/glass to bond everything. If it is gel coated odds are it is polyester. Epoxy will delaminate from polyester over time every time. The tips given are good ways of doing everythin regardless of the type of glass.

Some of the auto parts stores are able to supply the correct paint in premix form in cans. It is best to used a catalysed enamel (polyurethane) clearcoat over the top. Join a club and see if someone in it can do the clear for you or get friendly with a body shop and ask if they can clear your boat when thery're doing a car/truck. Slip them a bottle of something and I'll bet you can get a great job done. It is worth going to a paint shop and having a talk with them and you never know they might do it for you with leftover paint as long as you do the labour. They can tell you how to go about it as well - nothing like access to first hand info.

Hope it all goes well

GT 8)

 

[Altimat]

Epoxy will delaminate from polyester over time every time.

I'll disagree. The only adhesion problems you will have with epoxy sticking to polyester resin is with old fiberglass which has absorbed oils.
"Epoxy Resin can be used over Polyester Resin. In fact, epoxy adheres better to cured polyester than polyester resin does and is a superior material for repairing fiberglass boats."

Quote from:http://www.clarkcraft.com/epoxyresin.php3

But polyester will never adhere to epoxy.

 

[Hydroguy8234]

I read once that polyester resins have a wax film that comes to the surface to aid in curring. Because of this I always sand old epoxy and clean with alcohol before I try to glue new stuff to it.

Dumas uses polyester resins in all of their hulls. If you go with the same stuff to glue in your rails make sure to have good ventalation. The stuff has very bad fumes.

The good thing is that polyester resins are cheaper than epoxy resins. I bought a half gallon at Menards for around $8.00.

 

[GTR]

Hi Altimat,

Maybe they have the best epaoxy resin around - I'm not in a postiion to judge. If epoxy is that much better than polyester why don't we use cyanoacrylate instead which is even stronger. The point I was making is it is always best to use chemically similar materials eg polyester with polyester, epoxy with epoxy. Having played with f/glas in boats (model mostly) I have found that the epoxies do evetually delaminate. It could be associated with the waxes in polyesters but I have always washed with acetone and made sure of a good keying surface. I agree in woiod construction it works way better than polyester.

just my experience. $0.02 worth

GT

 

[Atious]

I have a 56" tunnel hull out in my shed I poly'ed over epoxy 4 years ago. It sucks. The poly resin only adhered in spots and looks like sheets would peel off, only I'm not that lucky. I was so disappointed with the results I still have yet to fix it. Having done work with poly numerous times, being a motorcycle mechanic and body man, I know how to use and prep for use with poly. Maybe my experience is unique..... I'll not try poly over epoxy again though.

 

[Atious]

I have a 56" tunnel hull out in my shed I poly'ed over epoxy 4 years ago. It sucks. The poly resin only adhered in spots and looks like sheets would peel off, only I'm not that lucky. I was so disappointed with the results I still have yet to fix it. Having done work with poly numerous times, being a motorcycle mechanic and body man, I know how to use and prep for use with poly. Maybe my experience is unique..... I'll not try poly over epoxy again though.

 

[Franko]

Altimat, GTR,

Thanks again for the help and advice.

I'll also try what GTR suggested about getting the paints in aerosol cans from a paint shop, maybe they will have the primer in cans also.

To all that helped, thank you.

Best Regards,

Frank

 

[GTR]

Hi Guy's,

My point was not that poly is better than epoxy because it isn't. I was just suggesting that it is always best to stick with the same material the hull is made from. Each resin has it's place but I don't like them mixed for different elements of construction/repair.

Just my own prejudice I guess.

Wish you luck with your project.

GT ;D

 

[snowdog-2112]

Very interesting reading but here's a question from a painting newbie.

Will clear acrylic play nicely with a color enamel paint and does the acrylic offer good fuel protection?

Thanks,

Snowdog

 

[Altimat]

Very interesting reading but here's a question from a painting newbie.

Will clear acrylic play nicely with a color enamel paint and does the acrylic offer good fuel protection?

Thanks,

Snowdog

Acrylic urethane offers the best fuel protection, and I've never had any problems spraying it over any enamel or basecolors. You will need to allow the enamel to cure and sand it for adhesion before clearing it though.