Internal painting: Pre-prep

[Alan Wheeler]

Well if you can, get the WestSystems fillers. It seems to be the cheapest around here. Ask for 410 microfibers. It should be a Tan coloured powder. Easy to mix and work with and cheap. DON'T go for the dark brown Microballoons. That stuff is expensive and harder to work with. I find a hand full of the white silica powder 406 thrown into the mix allows a "mayonase" mix to not slump. However, a very thick "peanut butter" consistancy is what you will be needing, so you probably don't need the 406 at all. Mix the 410 As thick as you can make it as this makes sanding easier. You will most likely need a 20ltr bag of the stuff.
I also suggest you go for a summer grade hardener. Once again, if it is west system, then you want the 105 Resin and a 205Hardener. Careful as you have a pot life of about 10min and in any bulk quantity, it will heatup and go of in a minute. DO NOT use the summer hardener if you are filling any area over say 25mm deep. It will get too hot. The 206will be hard enough to sand in about 6hrs. The winter hardener will give you a much longer work time and allow you to fill much larger volumes, but will start its curing process in about 45min and will take about 12hrs before you can sand.
For shaping, obviuosly, the closer you can get to the finished article, the less sanding after cure. So cut some shapes from plastic of what you want as a finished fillet. USE GLOVES, it is a messy job no matter how careful you are.
Hope this helps.

Glad you clarified that Wheels. I figured you meant the epoxy fairing, not the Polyester. Bondo was used for years, but it does not do well in marine environments It was even used in the 60's as seam compound on wood boats. I have dealt with this. No fun. I agree that the 410 filler is easier to work with, but I prefer the 407, at least for external fairing on the hull. I have had the 410 clog sand paper. Just a personal preference. I like the West Systems because I am familiar with it, but I know there are allot of equal products out there.

[jimini]

Please do not use common auto body fillers, they will hold moisture and that is something you don't want in any boat. There are products out that are made with fiberglas for fiberglas tapering. Kitty Hair is one, Tiger Hair is one and also Gorilla Hair too... All made with chopped fiberglass and used with mixing resin much like auto bondo products... Rough/grind the old fiberglass up to give the newer Gorilla Hair something to bond to Mix amounts small enough that will give you time to work the glass into shape without lefting and putting air bubbles in it Never mix chopped fiberglass and resin by stirring with a stick; always mix with a bondo paddle and use folding motions as if one is applying it to a surface, working out air bubbles as you going. Keep the edge of the paddle at 45° and drag it towards you, seldom push it away . Than sand after drying (at least 30min >whatever)with 80 grit on a dual action sander. Next apply a medium coat of fiberglass resin to allow for "setting in" the rough spots; let dry and smooth the area with 180 grit sandpaper on a dual action sander - than prime with a "good quality' primer and spot putty the small inperfractions and resand than reprime sanded spots THAN topcoat... A local shipyard should have answers to what products would be best to use also... Basically grind; apply; sand; apply; sand; apply; prime; sand; reprime; topcoat...

Twenty Five years as a body/fenderman pays off sometimes...

jimini®