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Question on DPLF Primer/Sealer

Reflex

Well Known Member
I'm using DPLF 90 (black) under K36 (gray) high builder primer on my -14. Last night, after shooting the elevator fairings, I noticed that I had a couple of spots where I sanded through the epoxy skim coat (West Systems) into the filler (microballons and epoxy).

If I'd sanded through the skim coat into fiberglass, I'd know what to do. Since I sanded into the microballons filler, I'm not sure what the result will be. There are no pinholes, the DPLF primer just appears to have a different finish (splotches) in a couple of areas where I sanded though the skim coat.

My question is, will the K36 high builder primer cover this error or do I need to sand off the DPLF primer and start over? My understanding is that DPLF is very difficult to sand.

I used Dan H's suggestion on using a roller to create an orange peel finish on the skim coat to act as a sanding guide....what a great idea! Apparently I just got a little too aggressive over a few inches on the filler. After a thorough examination before spraying the primer, I could not tell that I'd gone through the skim coat.

Fred
 
There are no pinholes, the DPLF primer just appears to have a different finish (splotches) in a couple of areas where I sanded though the skim coat.

My question is, will the K36 high builder primer cover this error or do I need to sand off the DPLF primer and start over? My understanding is that DPLF is very difficult to sand.

The K36 should cover.

DPLF wet sands just fine, so you can kill orange peel, roughness, or dirt in a primer coat when necessary. If you feel like the splotch surface texture needs improvement prior to K36, grab a spray bottle with clean water and some 400 wet-or-dry. Wet sand lightly, rinse, wipe dry with a blue paper towel or painters rag. Don't break through, but if you do, no big deal...shoot more primer.

Beer selection is critical. For wet sanding DPLF, I recommend Newcastle.

Wet%20Sanding.JPG
 
fiber glass fun day!

I’m also starting the process on my cowl. OH BOY!

I’m starting with a k-36 like product (Shop Line clone). As the cowl is a combination of parts (std cowl with round inlets), I also have a few seams to hide. I was semi-successful with the seams - not too much work on the seams in terms of hiding lumps — just a bit of filler to make ‘em almost invisible.

My process is to sand the raw glass to make sure the release chemicals are gone, (clean before sanding), then dry wipe the surface. Then, I spray on the K-36. Do not blow off the surface with air, and do not wipe with a solvent rag.

Yep - spray the primer/filler right over the pin holes filled with raw fiberglass. If I miss any, I can use a gloved finger to push the K-36 into any open holes.

This is not a new trick - learned it when building my RV4 in the early 90s. That fella told of using dry wall mud dust on his parts, but I thought that the fiberglass dust might work better. No problems in almost 30 years!

Come to think. Of it, that process might have been described in Sport Aviation?

In any case, do not follow what I do, else you might end up with a finished airplane a bit faster...
 
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Let's see, the "Horton Hat". One side beer tube to mouth, the other side water with a tube down the arm to the sanding hand with a metered drip. Oh, then I guess we need to automate the balanced reload of each side of the hat...
 
Kirker Perfect Prime is a knockoff of K36, 1/4 the price of the PPG product. I've used it on cars and airplanes. Its flexible and works great on plastic bumpers and fiberglass parts. Super easy to wet sand. On the fiberglass parts I use ordinary drywall compound for pinhole filling. Summit racing sells Kirker rebranded paints and primers as their own line.

Whoever came up with pinhole filling with epoxy/micro is a masochist.

https://www.autobodytoolmart.com/kirker-perfect-prime-2k-primer-gray-up732-p-12618.aspx
 
Whoever came up with pinhole filling with epoxy/micro is a masochist.

Or gravely in error. Micro is not a pinhole filler. It's for shape and contour. And yes, there are alternatives.

Just remember the Chinese menu. Fast, cheap, good, pick any two.
 
Or gravely in error. Micro is not a pinhole filler. It's for shape and contour. And yes, there are alternatives.

Just remember the Chinese menu. Fast, cheap, good, pick any two.

I'll tell ya...whoever came up with using spackle was a genius. Disproves this theorem, as it satisfies all three requirements.
 
Spackling compound is just gypsum and a water based glue. I suspect for pin holes, it doesn't matter if a primer adheres well or not given how little surface area a pin hole presents.
It would be interesting to see if primer will stick to the spackling if there was a larger surface area. I might have to try just to satisfy my curiosity.
 
Many thanks for the input. I shot the K36 last night directly over the DP90LF with no sanding. I couldn't be more pleased with the results. No sign of where I sanded through the filler.

Fred
 
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