jackhammer

I went ahead and made a windscreen with 1700 glass and US Composites slow cure 635. I'm happy with the rough work and am trying to make it smooth. I've been using the same 635 and adding cabosil to make it more like a paste. It's working good, but I'm thinking there's got to be a cheaper, faster, and better way.

Is there any fairing compound I can use on this epoxy that cures fast like the polyester putty's?

Also, when can I prime it? If I have some 80 grit scratches do I need to take them out first or can I use a higher build primer directly to the bare epoxy?

glassdave

iTrader: (1)

I use AdTechs 861 Ultrafair for the major straightening then a thin coat of 865 FinalFair to take care of any porosity. Its a great system and sands easy. Ultrafair cures pretty good in 24 hours but FinalFair seems to take a few more days, both sand very well. 861 Ultrafair actually looks just like light chocolate cake frosting and spreads just as easy . . . . . . does not taste as good though Once you have the surface straight and sanded up to about 120 or so you can use automotive primers.

http://www.adtechplastics.com/c-13-m...compounds.aspx

jackhammer

Wow, 861 Ultrafair up to 1" thick? I'll have to get a quart, thanks Dave!

glassdave

iTrader: (1)

I've actually use it at that level to, its great stuff and doesn't shrink or move around. Did some extensive work on a bilge that necessitated some heavy fill and it worked great. It will have some light surface porosity so you will need some of the 865 for a final coat. It says its sprayable but not with conventional equipment. You could brush the stuff on and get decent results.

jackhammer

Oh man, my eyes started watering when they told me the price... $167/gal

I called our man at US Composites who recommended the Fasco 110. He said one part is like peanut butter and the other like vaseline, doesn't shrink, adhesive strength like marine tex. And people are using it for a fairing compound. Too much sales pitch?

Have you tried this stuff?

http://www.uscomposites.com/adhesives.html

glassdave

iTrader: (1)

Havnt had the chance to use that yet but i would suspect it would work fine although it might be a pain to sand. You are doing a pretty good amount of surface area, whats your time worth

Unfortunately one of the drawbacks to using epoxy is limited and often pricey products. I have found whenever i tried to save a few bucks it cost me huge in time and effort to finish.

jackhammer

Time is a good point. But for me it's not the money, it's the frustration. I work and work and work and it just never seems to get right. I can get things smooth, it's straight/flat that kicks my ass.

I went ahead an ordered a gallon of the Fasco 110. I need to do some rough work in other areas so it's ok. If I sent you a sample would you compare it to the 861 for me?

glassdave

iTrader: (1)

sure that would be cool, I'd actually to see a comparison my self. Easier sanding products tend to fair better and one of the tricks to getting things straight is to use courser grits to do all the roughing. The majority of sanding during the fairing process is gonna be with something in the 36 or 40 grit range. A common misconception is that finer grits make things straighter when its actually the opposite. Finer grits just finalize the surface for primers and the progression through grits is very important. For something like your project i would do all my sanding and shaping in forty grit and maybe 80 for shapes/features/edges then after i feel its true i would go over everything with a quick hit of 80 grit then lay a coat of 865 on. Finalize the shape with 80 touch that up with 120 and 180 then prime. Final shaping is always done by hand and you kind of have to sneak up on it.

I'll PM ya my address.

Can you post some pics of the progress so far?

jackhammer

Here are front view before and after. For the support I modified the rail and used the sheet pvc as a template. I liked the way it looked so I just glassed over the sheet and rail. I tested both for adherence and they held pretty good so I was ok with it. I first filled in the gap between the rail and pvc and used some 6oz cloth to pull them together. When I wrapped the 17oz stuff around it I had trouble keeping it stuck up under, in those places I used more 6oz and made a real mess.

jackhammer

Here is a side view showing the new lines. I cut the sides down about 3" to match the lower profile. I also didn't like the hatches sticking up so high so I took them out too.