What's new
Van's Air Force

Don't miss anything! Register now for full access to the definitive RV support community.

Glassfiber putty vs west systems resin/microballones

Epoxy

What base is that putty product? Polyester? West system is epoxy based, it doesn?t shrink like polyester does, it?s really light when mixed with micro balloons..What benefits are you looking for with the Valspar product? West systems epoxy is super versatile..you?ll love having it anyway when you have to modify fairings..
 
I am new to this. yes.
the Valspar stuff seems smoother and easier to spread.
I did already use the WS w/micro, and it doesnt' get very smooth. there are air bubbles after I spread, no matter how much mix.

Do you believe the valspar will shrink and crack over time?
after all , its being used on cars?
 
Micro

I don't get air bubbles, but I don't use Cab-O-Sil. No idea.
However, there is a trick you could try. If I want the micro smooth, wet your fingers or a credit card with a spray bottle of water and smooth it. It sets just fine. That said, I sand most of it off anyway and apply two coats of Kirker EnduroPrime as a high build primer. Anything like pinholes gets filled.
 
Manually mixing epoxy and microballoons to get the right consistency for a float coat is tricky. If you your mix is heavy on the epoxy side, then it's heavy. If it's heavy on the microballons, you get a lot of micro voids, sorta defeating the purpose of using it in the first place.

You can make a test and weight the difference, I am betting the weight difference is very small. The panel is already cured so you can apply any system, epoxy or polyester on top and it doesn't matter. Most of the fiberglass products provided from Vans use polyester resin gel coat anyway. .
 
My favorite is Poly Fiber SuperFil. It mixes perfect, does not shrink
and sands very easy. It will last a long time if stored in a cool dry
place.
 
Manually mixing epoxy and microballoons to get the right consistency for a float coat is tricky. If you your mix is heavy on the epoxy side, then it's heavy. If it's heavy on the microballons, you get a lot of micro voids, sorta defeating the purpose of using it in the first place.

You can make a test and weight the difference, I am betting the weight difference is very small. The panel is already cured so you can apply any system, epoxy or polyester on top and it doesn't matter. Most of the fiberglass products provided from Vans use polyester resin gel coat anyway. .

This reminded me of a trick I used 25, 30 years ago in my RC plane days. We'd make flowable filler with epoxy resin cut with acetone and filled with micro balloons. Now, this was with model planes, but it sure seemed to work well. Does anyone have any actual technical knowledge with acetone and epoxy resin, and the impact to its physical properties?

Guess I should have searched then posted... Found this.

https://www.epoxyworks.com/index.php/thinning-west-system-epoxy/
 
Last edited:
I don't know the physical properties, but West Systems advised me that G-Flex could be thinned up to 5% by weight with acetone. I did that for something and it definitely made a significant drop in viscosity. No data, just a qualitative observation.

For other epoxies, it would probably be worth to contact the manufacturer for guidance.

Dave
 
I am building an RV10, and would like to smooth the cabin top before top coat.
most of the builders are using west systems resin plus micro or cab-o-sil.
I wonder if anyone has tried automotive putty products....

Dry micro (microballoons and epoxy) is used to change contour. Microballoons add fill bulk with very little weight.

Cabolsil makes resin thixotropic...it doesn't run. Cabo is not a filler material.

I've seen four or five different fillers applied to the same RV-10 cabin top. For sure, it is very difficult to sand a flat surface contour across fillers of different densities. Much better to contour using just one.

Primer-surfacers and high build primers are used later, with block sanding, to optically flatten prior to paint.

What exactly are you trying to do?
 
I used evercoat rage extreme on my 10. I have done a lot of auto painting and much prefer poly putties to epoxy. I did use 3M High strength repair filler for anything that needed rigidity or strength before the filler. I agree that epoxy based fillers have their place in some applications, but for smoothing an F/G top, poly fillers are much faster and easier to work with.

Don't use basic fillers for beefing up low areas near the door. build up with something stong, with filler on top to finish it off / clean it up.

Larry
 
Dry micro (microballoons and epoxy) is used to change contour. Microballoons add fill bulk with very little weight.

Cabolsil makes resin thixotropic...it doesn't run. Cabo is not a filler material.

I've seen four or five different fillers applied to the same RV-10 cabin top. For sure, it is very difficult to sand a flat surface contour across fillers of different densities. Much better to contour using just one.

Primer-surfacers and high build primers are used later, with block sanding, to optically flatten prior to paint.

What exactly are you trying to do?
Thank you guys for the insights!

Dan, I installed the RV10 cabin top overhrad console, and now I wish to fill all the gaps, holes, smooth the surface ,round the cabin top pillars before primers and final paint.

I guess I will start with WS and balloons.
Final finish with putty? Or still with ballons?

Tnx
Oren
 
Hi Oren.

I did my cabin top interior with Epoxy/Micro mixture, faired it and then skim coated with straight epoxy. I then applied high build primer and painted It worked out very well.
 
Thank you guys for the insights!

Dan, I installed the RV10 cabin top overhrad console, and now I wish to fill all the gaps, holes, smooth the surface ,round the cabin top pillars before primers and final paint.

I guess I will start with WS and balloons.
Final finish with putty? Or still with ballons?

Tnx
Oren

Gaps, holes, and shaping around pillars are all jobs for micro.

This is honeycomb and glass, faired with micro, sealed with an epoxy skim, followed by wet-on-wet epoxy primer and PPG K36 high build. Nothing else needed. I restrict polyester to small defects discovered after the first coat of epoxy primer, if any.

There are no magic product shortcuts. Shape and surface are products of care and work.

Canopy%20Interior%20Painted.JPG
 
My favorite is Poly Fiber SuperFil. It mixes perfect, does not shrink
and sands very easy. It will last a long time if stored in a cool dry
place.

+1 for Poly Fiber SuperFil! It sprays real nice if you dilute as per instructions. If you spray VS brush or roll, it will take very little sanding to get a nice smooth service.
 
+1 for Poly Fiber SuperFil! It sprays real nice if you dilute as per instructions. If you spray VS brush or roll, it will take very little sanding to get a nice smooth service.

Perhaps you meant Poly Fiber Smooth Prime?

Super Fil is a two-part epoxy filler, basically expensive pre-mixed epoxy and microballoons
 
OVERZEALOUS SANDER

With little to no experience with fiberglass and fearing the worst, I finally dove in & tackled the canopy fairing (RV12). Outcome seems to not be too bad!
Except I sanded right thru a thin spot. What do you guys think I should do to repair ? Floxed resin? add a layer of glass?

sequence of events :
after cure
https://photos.google.com/share/AF1...?key=b09kWkNmNFRoSDJaNmxZTVUxVk12T2RSa2Jqd2dB
after some (too much?) sanding and trimming, canopy removed
https://lh3.googleusercontent.com/p...vdn1p8GLy-MCDZ3r40YMX=w640-h480-no?authuser=0
outboard view (red tape placed behind hole)
https://lh3.googleusercontent.com/p...RwVY43KWULACSVx8XW_Fq=w640-h480-no?authuser=0
inboard view
https://lh3.googleusercontent.com/p...ALgHOpvPChwtJTrpIjCdx=w480-h640-no?authuser=0
 
Hole

Dan is the expert, but I would add several layers stacked in a reverse pyramid so the layers form a scarf joint. Probably at least one inside as well.
 
Dan,

I have SEM high build primer that I was planning to use for this same application.
(https://www.semproducts.com/product/high-build-primer-surfacer/42013)

Calling that stuff "high build" is a bad joke at consumer expense. Per the datasheet, it is less than 10% solids by weight. Compare with PPG K36 for example, at more than 50%. You would spray a whole case of cans to get equal build.

Can't prove it, but I'd also bet adhesion is better with the two-part catalyst activated professional product.

Does the darker primer have to be epoxy based? Or would any dark primer suffice?

I use dark epoxy primer under a lighter high build for two reasons. First, while block sanding for surface flatness, I can see when the high spots get thin. Second, if sprayed "wet-on-wet", the epoxy primer ensures superior long term adhesion.

"Wet on wet" means spraying a cross coat of epoxy primer, allowing the solvent to flash off, then spraying two cross coats of high build, roughly 4 mils. Although the solvent has mostly evaporated, the epoxy is not cured, and the two materials bond. For K36, PPG says the primer must be overcoated with 7 days. Per a good long conversation with a PPG rep some years ago, I wait about 30 minutes. The rep's description was "about as long as it takes to clean the gun and mix the high-build".

A 4 mil wet coat will shrink to about 2 mils when dry. You can block it to a half mil or a little less over the high spots, then spray two more cross coats and repeat. Note two rounds nets about 5 mils of build in the low spots when the highs are at minimum, which tells a lot about how close you want to get with your original surface contouring using micro.
 
Thanks.
Which primer do you typically use?

I use PPG, mostly because I have an excellent PPG distributor in my area. I recommend you use whatever major brand is sold by a local pro paint shop where you can get good advice when needed....PPG, Sherwin Williams, BASF, AkzoNobel, etc.
 
I used...

I used epoxy/micro/cabo for the first two coats; put it on with a flexible squeegee.

Light sanding in between coats.

Then I used straight epoxy, applied with a 6" squeegee. Light sand between three coats.

Very smooth, no noticeable pin holes...I will have to wait and see when they prep it for paint...

I am planning to fly off Phase 1 before paint...
 
Prep

I'm backwards. I apply neat epoxy. Cure 30. Spread a layer of micro. Cure overnight.
Sand 40 grit till surface is uniform then 80 to smooth. It's white now.
Apply a coat of Kirker EndroPrime. Gray epoxy primer. Cure 60. Apply second coat. Cure overnight. Wet sand 180 till uniform then finer grits to paint ready. White shows through the gray as it gets thin. Dry. Spray two coats Kirker EnduroPrime 60 minutes apart. Cure overnight. Wet sand 800. Dry. Spray final color. Cut & Buff.
 
I feel like I have some experience at filling and sanding because I spent literally two years doing that on my entire airplane, not just the canopy. I used West Systems and microballoons for the most part and it has held up pretty well over the years; I've never had any slough off. I've read this entire thread and I'd say that DanH has the best advice. The only thing I would add is you only get one chance with the West Systems so put it on thick and file/sand it back down. If you find a low spot later and try to fill it with more West Systems, it will leave a margin of pure epoxy that you can never sand out. West Systems and microballoons kind of has the consistency of cake frosting when you spread it on. Pro Tip: You can let the West Systems cure to the "green" stage and knock back any high spots with a SurForm file. That saves a lot of sanding. Unless you have a vacuum pump to de-aereate the mix, you're going to get some entrained bubbles. Maybe DanH has a better way but I just filled those with Evercoat glazing compound. Yes, the PPG primer is great, and you can alternate colors for each coat.
 
Thanks, guys.

I applied a skim coat of neat epoxy over the contoured epoxy/micro surface today. I'll wait for that to cure, overall happy with it so far. There are 2-3 minor imperfections that I'll need to look at.
 
Glazing

Thanks, guys.

I applied a skim coat of neat epoxy over the contoured epoxy/micro surface today. I'll wait for that to cure, overall happy with it so far. There are 2-3 minor imperfections that I'll need to look at.

If they are really minor like pinholes or deep scratches, try automotive glazing compound. Available at any auto parts. Looks like a tube of toothpaste. Use a credit card to squeegee a pea size amount on the spot. Sets in about 30. Wet sands like primer.
 
Fiberglass rookie

Could someone please explain” neat epoxy” please. I’m at this stage as well and about as fiberglass illiterate as they come. Thanks in advance.
 
Neat epoxy

Could someone please explain” neat epoxy” please. I’m at this stage as well and about as fiberglass illiterate as they come. Thanks in advance.

That's epoxy mixed with no fillers. Just epoxy. I brush on a coat before applying micro to help it bond. Sime builders apply it to fill minor imperfections.
My process is documented on my blog. Some have self archived.
Best place to start is Dan's thread on Fiberglass. He is the expert.
 
Last edited:
For those applying epoxy skim coats, I thought I would add something I learned recently.

Most epoxies leave a slightly sticky waxy residue on the surface when they cure. This is called Amine Blush, and it is a result of amine precipitating out of the epoxy as it cures. Amine blush will obviously interfere with adhesion of later coats of anything and must be removed.

Over the years, I have mostly relied on sanding the amine blush off. It is gummy and loads sandpaper pretty fast. On a recent project (wood) I tried vigorously scrubbing the surface with acetone, and it did not do much to remove the amine blush. So I went back to sanding. Then, I put a coat of urethane spar varnish over the epoxy (for UV protection) and a strange thing happened. The varnish wouldn't cure.

I have learned that acetone can actually make the amine penetrate back into the epoxy. Then, even though the epoxy was fully cured and scuff sanded, the residual amine embedded into the epoxy interfered with the cure of the varnish.

So - how best to remove amine blush? Well, it turns out that soapy water works GREAT. I use a fine Scotchbrite pad and water with some Dawn dishsoap and it comes off really easily. I still scuff sand the surface before re-coating, but it doesn't load the sandpaper because the amine is gone.

So - any time you are re-coating over epoxy, especially neat skim coats, just scrub with soapy water before scuff sanding.
 
That's epoxy mixed with no fillers. Just epoxy. I brush on a coat before applying micro to help it bond. Sime builders apply it to fill minor imperfections.
My process is documented on my blog. Some have self archived.
Best place to start is Dan's thread on Fiberglass. He is the expert.

Agreed!! I have checked out both of your write ups, I?m just a little mentally challenged on the terminology. Thanks for the response!!!
 
Most epoxies leave a slightly sticky waxy residue on the surface when they cure. This is called Amine Blush, and it is a result of amine precipitating out of the epoxy as it cures.

Steve, is your shop climate controlled? Generally amine blush isn't significant if temperature is stable and humidity is low.
 
Steve, is your shop climate controlled? Generally amine blush isn't significant if temperature is stable and humidity is low.

The particular project in question was in my garage and probably got cooler than typical overnight. But I think we always get a little bit of amine blush with the Jeffco 1307. Normally it gets removed with the peel ply. But that isn't helpful for surface finishing.

Ironically our composites shop probably stays more stable in temp during the winter, because we will run the shop heat overnight. In the summer, we go from warm days to cool nights. On the other hand, the epoxy is pretty well cured before evening comes.
 
Pure (or "neat") epoxy is heavy. The only place I used it was to seal my wing tanks. Applying the PRC tank sealer on a primed piece of pre-preg fiberglass was unsatisfactory because it was full of pinholes. So I tried pure epoxy on a test piece. When I brushed on the first coat, it was full of pinholes as well. So I let it set up for a couple hours until it was tacky and brushed on a second coat. That one was absolutely smooth. When it was cured, I applied the PRC tank primer and sealer. I haven't had any leaks in six years.
 
Ironically our composites shop probably stays more stable in temp during the winter, because we will run the shop heat overnight. In the summer, we go from warm days to cool nights. On the other hand, the epoxy is pretty well cured before evening comes.

Probably local advantage. Dixie, The Land That AC Built. My shop is heavily insulated with 4 ton heat pump. When working composites it never strays more than a few degrees from 75F and 20% RA.
 
Last edited:
I?m a little late joining this post, but have a couple observations. If I was creating a filler that is mechanically bonding two surfaces, I think I would use something structural, like flox or West System Micro Fibers (fiberglass), because it has some structural properties - and if it?s thick, lay in a layer or two of wetted cloth to prevent future cracks. Micro is used to finish the bond joint before prime/paint, not for bonding structural surfaces. It has no structural properties. As far as the amine blush goes, yes this needs to be removed before doing any other step, and it can be removed with soap, warm water and a scotch brite pad in just a few minutes. No need to load up your sheet of sand paper with this waxy substance, just wash it off. If you are laying cloth, the amine blush comes off with the peel ply that you should use over cloth layups. You probably know all this already, but haven?t seen it in this post, so.... just sayin?...
 
Jeffco is very blushy. Have you looked at MGS resins?
The particular project in question was in my garage and probably got cooler than typical overnight. But I think we always get a little bit of amine blush with the Jeffco 1307. Normally it gets removed with the peel ply. But that isn't helpful for surface finishing.

Ironically our composites shop probably stays more stable in temp during the winter, because we will run the shop heat overnight. In the summer, we go from warm days to cool nights. On the other hand, the epoxy is pretty well cured before evening comes.
 
Jeffco is very blushy. Have you looked at MGS resins?

Agree on the Jeffco (Rhino). Brushed/rolled two coats on a foam/mud turtledeck form a few days ago, and noticed a lot of blush, even in a low humidity shop. But it's cheap!

Hotwired%20Foam.jpg


Turtledeck.jpg
 
Agree on the Jeffco (Rhino). Brushed/rolled two coats on a foam/mud turtledeck form a few days ago, and noticed a lot of blush, even in a low humidity shop. But it's cheap!

Dan,
Curious what your suggestion for a similar structural resin would be as an alternative to the Jeffco?
Brad
 
Curious what your suggestion for a similar structural resin would be as an alternative to the Jeffco?
Brad

You mean primary structure, like spars and ribs? Picking epoxy for that is above my pay grade. For primary stuff I'd use whatever was specified.
 
I use PPG, mostly because I have an excellent PPG distributor in my area. I recommend you use whatever major brand is sold by a local pro paint shop where you can get good advice when needed....PPG, Sherwin Williams, BASF, AkzoNobel, etc.

The local PPG distributor here has been great. I spent half an hour with him yesterday having him match a SEM color for my top coat. Picked it up this afternoon (a DBC/DBI).

I had to spend a bunch of time getting my garage ready to spray, so it's taken a little bit to get to this point.
I'm at the point of the first high-build step and I'm pretty happy overall so far. I blocked it and getting ready for round 2.

One thing he recommended was sealing the K36 and he suggested their Omni Sealer product prior to paint. I assume there shouldn't be an issue with doing that? His claim was the K36 would soak up the topcoat and it could require a lot more coats..
 
One thing he recommended was sealing the K36 and he suggested their Omni Sealer product prior to paint. I assume there shouldn't be an issue with doing that? His claim was the K36 would soak up the topcoat and it could require a lot more coats..

When in doubt, refer to the product data sheet. Don't know about the Omni sealer, or about soaking up topcoat, but there is a note stating K36 must be sealed before spraying DBC black. Point being, there may be things going on which we don't understand.

Datasheets here:
https://us.ppgrefinish.com/PPG-Refinish/Products/Automotive-Refinish/Deltron#

My K36'd parts were sprayed with DPLF, along with the rest of the airframe, the day prior to color. The epoxy primer is a bit like an adhesion promoter, and I wanted the same primer color under the topcoat everywhere.

P7040001.JPG


P7040002.JPG
 
Last edited:
Back
Top