jsherblon
Well Known Member
Anyone have experience with Loehle Wonder-Fil for pinholes? http://www.loehle.com/
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Loehle Wonder-Fil?
- Thread starter jsherblon
- Start date
aadamson
Well Known Member
Nope, but
I think I'd want to know what it's made of.... Polyester shrinks with time and some fillers absorb water.
Really, if you are just looking to fill pinholes. Take raw mixed epoxy (no fillers), and use a squeegy to put it on, taking most of it off. This will allow the epoxy to "wick" into the holes and a good finishing epoxy will fill the holes instead of just "dome them over". That little bit of epoxy all over the part is really easy to sand, it just takes time for it to cure first. Also might have to do it more than once, but doing it the other way, usually takes more priming and sanding, putting most of the $$$ on the floor. Oh, and you'll be surprised at how far a little epoxy will go doing the above.
BTW, all epoxies are *not* the same when it comes to thin coats. Some won't cure. West and Jeffco shouldn't have that problem.
Good luck,
I think I'd want to know what it's made of.... Polyester shrinks with time and some fillers absorb water.
Really, if you are just looking to fill pinholes. Take raw mixed epoxy (no fillers), and use a squeegy to put it on, taking most of it off. This will allow the epoxy to "wick" into the holes and a good finishing epoxy will fill the holes instead of just "dome them over". That little bit of epoxy all over the part is really easy to sand, it just takes time for it to cure first. Also might have to do it more than once, but doing it the other way, usually takes more priming and sanding, putting most of the $$$ on the floor. Oh, and you'll be surprised at how far a little epoxy will go doing the above.
BTW, all epoxies are *not* the same when it comes to thin coats. Some won't cure. West and Jeffco shouldn't have that problem.
Good luck,
I've tried the squeegie epoxy thing twice and had pretty terrible results. I found that it was difficult to sand and didn't get into the holes very well, resulting in the holes opening back up after sanding. As for polyester based products, I've used them for years on cars and bikes and never had a problem with shrinking or absorbing water. Actually, how would a filler absorb water when it spends its life under sealer and paint? This is just my own limited experience, but it is first-hand.
aadamson
Well Known Member
info
Polyester fillers will shrink and crack with time. As for sucking up water, other fillers that do that, do it *before* you paint them. Put them in the hot sun for a few hours and you get little pock marks that's the water trying to escape, then over time, that paint will lift where the water was.
If you want to try another filler, then my suggestion is Rage Xtreme by evercoat. Or, lots of coats of K38 PPG primer
Polyester fillers will shrink and crack with time. As for sucking up water, other fillers that do that, do it *before* you paint them. Put them in the hot sun for a few hours and you get little pock marks that's the water trying to escape, then over time, that paint will lift where the water was.
If you want to try another filler, then my suggestion is Rage Xtreme by evercoat. Or, lots of coats of K38 PPG primer
I keep reading that we're not supposed to use polyester fillers cuz they will shrink and self-destruct, but the entire auto repair industry runs on the stuff, not to mention the auto manufacturers. Every car on the road has filler on it and they all seem fine. I'm confused. Every car on the road has some filler and I don't see evidence of a problem. What am I missing?
Incidently, I believe Rage is polyester based.
Incidently, I believe Rage is polyester based.
1) It does and WILL shrink. This occurs as it's curing and is a major problem if you're making castings or some large buildup. This is not typically a problem if you're applying it in a thin film. It's also not a major problem if you're applying it in the form of a filler. The problem is when the resin is held in a mold, or put in a big glob in a corner, etc, where it can't shrink uniformly due to being constrained. Wanna fill a crack? Polyester my very well crack. Smoothing small surface imperfections? Polyester's fine.
2) In a thin film, polyester may or may not cure properly. It doesn't cure properly in the presence of air. Thick and thin are relative. If you squeegy it on until it's razor thin, you may come back the next morning and find it's still sticky. You didn't mix it wrong...
3) It's adhesive properties stink...does it stick well enough for filler? Yes. Is it good for repairs? No. If it's sticking properties suck so much, how can they build big boats out of the stuff? They apply the different layups while the polyester has not fully linked (it's hard, but it's still "green", as they say). The new layers bond CHEMICALLY with the underlying layers.
4) It won't cure properly over uncured epoxy. Epoxy can take weeks to cure.
5) It's dirt cheap. If it wasn't for this, no one would use it. Hey, if you have a process down to make it work, and you can save a ton of cash, why not use it, right?
6) It's curing rate and to some extent it's properties can be changed by varying the amount of catalyst (MEK, by the way). This is an advantage. You're pretty much stuck with an epoxy's chemistry, like it or not.
Maybe I'm off base on some things, and I'm always eager to learn something new, but this is how I've come to understand it's properties over the years.
2) In a thin film, polyester may or may not cure properly. It doesn't cure properly in the presence of air. Thick and thin are relative. If you squeegy it on until it's razor thin, you may come back the next morning and find it's still sticky. You didn't mix it wrong...
3) It's adhesive properties stink...does it stick well enough for filler? Yes. Is it good for repairs? No. If it's sticking properties suck so much, how can they build big boats out of the stuff? They apply the different layups while the polyester has not fully linked (it's hard, but it's still "green", as they say). The new layers bond CHEMICALLY with the underlying layers.
4) It won't cure properly over uncured epoxy. Epoxy can take weeks to cure.
5) It's dirt cheap. If it wasn't for this, no one would use it. Hey, if you have a process down to make it work, and you can save a ton of cash, why not use it, right?
6) It's curing rate and to some extent it's properties can be changed by varying the amount of catalyst (MEK, by the way). This is an advantage. You're pretty much stuck with an epoxy's chemistry, like it or not.
Maybe I'm off base on some things, and I'm always eager to learn something new, but this is how I've come to understand it's properties over the years.
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All true, but my point was that for smoothing out pocks and pinholes in a cowl, body fillers seem like just the ticket. Way easier to sand than epoxy, cheaper, dries quicker. The issue of using on uncured epoxy seems moot since the cowl was built a long time ago, and shrinking is not a problem with modern high quality fillers if used correctly. By correctly, I mean as fillers, not to fill giant divots or to sculpt a set of tailfins to make the RV look like a '59 Caddie. As far as adhesion goes, good filler sticks just fine if the surface is reasonably rough and clean. I wasn't trying to say that polyester is some kind of wonder filler, but it's not nearly as crappy as folks are saying. If used correctly it will stay put and the paint won't peel off. We're all driving around with the stuff and our cars are fine. If the paint blisters in the sun or a big slab of bondo falls off your plane, it's cuz you screwed up and not the filler's fault
szicree said:
100% correct! Filling pinholes is a very good use because you don't end up with a thin film, and it gets very hard and brittle (excellent for sanding). Not really any better than other fillers, maybe, but certainly no worse in this respect and there's no reason to not use it here.
My point re: the epoxy is that I think a lot of people lay up their own parts, or maybe use little strips of glass here and there to build up an area that needs some touch up. It was more directed at this sort of thing. Totally no issue if you're on old epoxy doing filling type work.
I would love to see someone put big Cady fins on their RV.
Tony Spicer
Well Known Member
Yep. Used it on my RV-3. Worked just as advertised. Used half a quart so far, with nothing but the spinner left to do. Don't remember where I saw it, but Van gave it a favorable report as well.
Tony Spicer
Anyone remember the beautiful yellow plane that Cory Bird of Scaled Composites designed and built. In Nov. 2004 Sport Aviation. "Next came what Cory calls a resin wipe. After going over the surfaces with 36-grit abrasive paper, he spread on a coat of pure resin, then immediately squeegeed it off.....repeated.... leaving a thin film of resin that filled every scratch and all the pinholes." I don't know much but I know Cory does.
Ken Broussard
Ken Broussard
Tony Spicer
Well Known Member
Bill,
The cowl has been painted for about five weeks. Pinholes are tiny little things. Most aren't any bigger than say, a pinhole. In engineering units, I would say .016 to .032 inches. If a paint dot that small didn't stick, how the heck would you even know?
Here's a photo:
http://picasaweb.google.com/tonyboytoo/RV3BMiscellaneous/photo#5145873060770268402
Zip down to Stag Air Park and I'll let you do the spinner!
Tony
High Build Primer K38 from PPG
I used the lots of coats (maybe 3 coats with light block sanding between coats) of K38 from PPG. Worked really well. Never really had a pin hole problem on any parts. The weave on the cowl is showing a bit after the first few summer months of flying but I atribute that to the cowl shrinking from the engine heat post curring it. I heard that from Scott MDaniels in another thread here.
I used the lots of coats (maybe 3 coats with light block sanding between coats) of K38 from PPG. Worked really well. Never really had a pin hole problem on any parts. The weave on the cowl is showing a bit after the first few summer months of flying but I atribute that to the cowl shrinking from the engine heat post curring it. I heard that from Scott MDaniels in another thread here.
