1975 Steury 15' Tri-hull Restoration

[Woodonglass]

Oooohhh Rahhh!!! Now Get some 2' tall saw horses to get her up to a good working height and go to work on sanding, filling, fairing, primer'ng and Painting. Let us know if you need anything!!!

 

[boatlex]

Here's a question... can fairing compound (epoxy based) be applied over primer? I suppose it might be safe if the primer is epoxy as well? I know usually you fair prior to priming, but for some areas on this boat it would be easier to see what needs to be faired after a coat of primer. The gel coat has faded quite a bit so as you sand into it, it changes color. The different colors are playing tricks on my eyes. The portion I'm talking about is actually pretty tricky, it's the compound concave shape right under the bow. Trying to sand that part evenly sure is hard, I've had to scrape with the edge of my block in an arc like I'm scraping furniture :/

 

[boatlex]

And one more question... I mixed up some filler and worked on some of the deeper scrapes and chunks taken out of the chines. I don't like the way my filler turned out. It's harder to sand than I expected, and keeps a rough texture. Rougher than the gel coat, despite both being sanded with the same paper. I used (roughly) 2 parts phenolic balloons, 1 part silica, and enough low viscosity slow cure epoxy to get it a bit thicker than peanut butter. I made it extra thick hoping it would help with sanding. Maybe I made it too thick, or didn't stir long enough, or maybe it just hasn't cured all the way yet? We did get some surprise rain, but I didn't think it would affect the epoxy since it had already been curing for 4-6 hrs and was dry to the touch.

Are my mix ratios way off? I can live with this as a rough filler but I was hoping it would be more chalky, almost like drywall mud. It would be a nightmare to work with this as a skim coat for fairing.

 

[boatlex]

I'll answer my previous questions... the difficult sanding of the filler was because it hadn't cured all the way. I guess the super thin coating, combined with high humidity, made the cure time way longer than the raka specs indicated. Using the fast hardener it was too gummy to sand after 24 hrs, but after 48 it was better. Also I used way more silica than most recipes recommended.

As for epoxy filler over epoxy primer, I couldn't find much information on that, but I did find one post somewhere random that said it worked well. It *sounds* like it should work. So here's my tentative plan, let me know if it makes sense:

1. sand 80-100 grit, fill/fair/shape as best I can
2. a few heavy coats of epoxy primer, then scuff with 120 for adhesion
3. any additional fairing/shaping required with epoxy filler
4. majic high build sandable primer with hardener
5. sand the sandable primer with 200 up through 400 grit until it looks perfect
6. majic tractor paint with hardener

That's assuming I decide to go with the tractor paint... I'm about to paint a few other things with it first, I'll see how they turn out.

 

[Woodonglass]

1.) I use primer to "see" any final flaws and then re-sand those areas removing as much of the primer as possible before adding more filler.
2.) I only use silica for deep gouges where I think I need more of a "structural fill". I also like my filler to be more like mayonaise so it flows into the fill area better. I feel it provides much better adhesion since it will get into the pores more readily than a thick mix. I also find a thinner mix is easier to sand. Careful with moisture and epoxy. They do NOT play well together.

 

[boatlex]

Hmm, interesting. Everything I've read (incl west system application guide) says the more microballoons you add, the easier it will be to sand. But it does seem maybe I've been adding too much. It does make it softer, but more "gummy". Dry sands ok, but doesn't wet sand very well. I think I will pick up some store-bought epoxy fairing compound to compare.

Meanwhile, I've been working on repairing the keel. It was in pretty rough shape. Here's what I've done so far:
- ground until I reached good glass (in the worst part that was all the way through the chop mat until I reached woven roving)
- filled until it was level with epoxy thickened with milled glass fibers and colloidal silica
- 3 horizontal layers of 1700 over the worst bit - these are very small, maybe 1" wide maximum, it just spans the cross-section of the keel
- built up a peak with the milled fiber/silica mix

It's looking pretty good, and I'm reaching the final shaping stages. I'm wondering about having a peak that tall (about 1/2") of thickened epoxy though. Will that be strong enough? Or do I need to grind 1/16" or so off and lay a strip of 1700 over the whole thing? That would be a whole lot more work to fair in and make it look good, but it's probably the "right" way. Or should I just roll with what I have?

 

[Woodonglass]

You're correct about the MB's making it easier to sand. I said I don't use the silica in my filler unless I want it to be more structural. Adding Silica to the mix makes it harder to sand. If you're using Thickened Epoxy with Glass fibers that stuff will cure and be very durable. Your keel will be fine like that. I'd shape it and call it good. That's just this Old Dumb Okies Opinion, so take it for what it's worth.:madgrin:

 

[boatlex]

The silica was for anti-sagging... several of the repairs I was doing were along edges, where vertical met horizontal. The silica kept it in place so it didn't start to run down the edge. And then I'd use what I had left to fill scratches and dips. I think that's where I went wrong, I should probably mix some without the silica for the surface filling. Those are the places that have been hard to sand without making recessed donuts around them!

The stuff I used on the keel was not chopped strands, it was finely milled into powder - looks almost like cornstarch. It's supposed to be super strong. I had bought it for making fillets for the transom and stringers. The site says it's for "high tensile strength putties and gap filling". The lack of longer fibers had me a bit worried, but I think I'm just over analyzing it (I tend to do that...) Anyways, it's shaping nicely so I think I will continue using it. Thanks!

 

[Woodonglass]

The balloons will thicken the epoxy enuf to keep it from sagging too! The Milled Fibers will add structural strength to the mix as stated but the fiberglass strands give it even more kinda like adding rebar to concrete instead of just gravel or sand.

 

[boatlex]

Yeah, I wish I'd thought of adding chopped strands before. Oh well!