Ok, I decided to fiberglass the small cracks and openings on my boat.I thought about filling with fiberglass paste,sanding,washing it down real good then spraying with gel coat using a preval sprayer or even just slapping it on with a small brush. My question is how do you form the paste and or gel coat on a rounded or curved surface? I was going to try to form the paste then sand,put the gel coat on ,cover with plastic and use a roller over the covered gel coat to help conform to the rounded surface. Will this work? Any other ideas?
Fiberglass problem??
- Thread starter paulh1
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I would just put the gel on then cover with some plastic and stretch the plastic tight to conform to the surrounding area. Then use painters tape to hold the plastic in the stretched position while it cures. You might have to do two coats. A light sanding and you will be good to go.
I agree with Jibes but I use aluminum foil. I shape it to the adjacent curve or corner and then move it over the damaged area to act as a mold. The last job I did I didn't have foil so I used the painters tape as a dam and over filled the area. I sanded down the excess when it hardened with the Multimate tool.
[edit - yes i first made structural or deep repairs with epoxy + fiberglass cloth or filler when required, then covered the last few millimeters with gelcoat as below. It's pretty easy to add fillers to make the epoxy a paste that can be sculpted before it sets]
This year I did alot of cosmetic fixes on our boat, with just the right tint of gelcoat supplied by our boat's manufacturer (fabulous support, even though long out of production).
The type of gelcoat they supplied is called topcoat, which means it contains a 'waxy' element that provides surface protection while the gelcoat hardens. So, no other skin or covering over the wet topcoat is required. A bit easier for fixes than having to mess with films etc.
For my gelcoat fixes, I first filled deep gouges with catalyzed gelcoat thickened enough with cabosil so that it doesn't run. Then, to finish or to fix smaller problems, I just used catalyzed topcoat painted on with a small brush or tool, then smoothed with plastic bondo spreaders.
Before and between applications, I cleaned the areas with acetone, sanded, then another wipe with acetone just before the gelcoat.
In this manner it was pretty easy to build up the gelcoat to any required profile. Don't try to get it all in one application. It's easy to build up to the desired level in a few applications, then sand to the final level. Finish off with 1000 or finer body-shop sandpaper, then polish. If the tint was perfect the repairs become invisible.
This year I did alot of cosmetic fixes on our boat, with just the right tint of gelcoat supplied by our boat's manufacturer (fabulous support, even though long out of production).
The type of gelcoat they supplied is called topcoat, which means it contains a 'waxy' element that provides surface protection while the gelcoat hardens. So, no other skin or covering over the wet topcoat is required. A bit easier for fixes than having to mess with films etc.
For my gelcoat fixes, I first filled deep gouges with catalyzed gelcoat thickened enough with cabosil so that it doesn't run. Then, to finish or to fix smaller problems, I just used catalyzed topcoat painted on with a small brush or tool, then smoothed with plastic bondo spreaders.
Before and between applications, I cleaned the areas with acetone, sanded, then another wipe with acetone just before the gelcoat.
In this manner it was pretty easy to build up the gelcoat to any required profile. Don't try to get it all in one application. It's easy to build up to the desired level in a few applications, then sand to the final level. Finish off with 1000 or finer body-shop sandpaper, then polish. If the tint was perfect the repairs become invisible.
As long as you can get sufficient depth of gelcoat and are fairly smooth in its application you can just treat it like car bondo. Slap it on till you get a nice uniform coat, then do the 60-80-100-110-220-600-rubbing compound sanding routine. 60 grit may be too aggressive for the thin layers we are talking about but will take the high spots out quickly.
All too often folks want to immediately go to 220 grit and they spend a LOT of time trying to sand out 60 grit scratches.
I did my rudder this way and it came out quite nicely.
Don't forget the alcohol hardener for the gelcoat
All too often folks want to immediately go to 220 grit and they spend a LOT of time trying to sand out 60 grit scratches.
I did my rudder this way and it came out quite nicely.
Don't forget the alcohol hardener for the gelcoat
the 'hardner' that Bill is referring to is Poly Vinyl Alcohol or "PVA", also know as 'parting fluid'. You spray it on the final gelcoat surface; and, the PVA affects a rapid cure of the gelcoat surface. Without the 'parting fluid' the gel wont completely cure within a reasonable time and any attempt at sanding without use of parting fluid will result in very rapidly 'clogged' sand paper and 'smeared' gelcoat surface.
example of PVA: http://www.jamestowndistributors.co...duct.do?pid=4213&familyName=Polyvinyl+Alcohol
Use a Preval self contained spray gun for the spraying: example - http://www.jamestowndistributors.co...t.do?pid=2155&familyName=Preval+Spray+Gun+Kit
example of PVA: http://www.jamestowndistributors.co...duct.do?pid=4213&familyName=Polyvinyl+Alcohol
Use a Preval self contained spray gun for the spraying: example - http://www.jamestowndistributors.co...t.do?pid=2155&familyName=Preval+Spray+Gun+Kit
To get the shape at the curves, I use a flexible spreader or squeegie. This takes some practice to get it the right shape. Sometimes I take a wooden stir stick (like an ice cream or Popsicle stick) and shape it with a sander to match the profile. If using a waxed resin or gelcoat, no PVA required. If you do need to seal the surface, hair spray will also work and is easier to apply than PVA. For finishing with spray, especially if using a gun or Preval, thin the gelcoat with 50% Duratec. No air cure agents are then required and the finish is glossier, harder and exhibits less "orange peel".
Just a few comments. First of all, I'd use polyester resin instead of epoxy because epoxy has some incapatibility issues with gelcoat and polyester doesn't and also it is much cheaper and for the repair you are doing, it is quite satisfactory indeed. I would grind out the cracks/crazing and then repair them with resin and cloth/mat and then sand it smooth to the shape required, then use a polyester putty to fare it out and smooth it up and then, spray gelcoat with the Preval sprayer you mentioned that is catalyzed and then spray PVA atop to get rid of the oxygen (but you can buy gelcoat with wax and so you don't need PVA or celephane, etc.). Then you wet sand the cured gelcoat (320/400/600) and when satisfied, buff out with FG rubbing compound and you are done. To put putting into cracks is like using concrete without rebar. And you cannot just spray gelcoat over the cracks to cover them up, because they will eventually show through your new gelcoat. That's what I do and I have been doing it for over 30 years.
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