Paint lifting off fillets....

Any suggestions for paint lifting/bubbling/shrinking from the fillet surfaces? This is the second time with the same plane.

Last time, I cracked the bubbles then sand the fillets with 400, then wiped with rubbing alchohol and re painted. I thought I was set, but after looking the other day; it happened again. The planes just been sitting in the rack for last season.

jon

If you're using butyrate dope, it's easy to get bubbles because it shrinks and adhesion is poor. This time after you sand it down to the fillet surface and clean it, try spraying the fillet area with auto primer first. You can also use nitrate dope. Keep the color coat dope thin over the area.

Alcohol may not be the best for cleaning your fillet joint, try wet sanding it with prepsol.

The best trick is to simply not use dope for the color coat. Automotive lacquer, epoxy, or almost any paint other than butyrate dope will adhere better and shrink less.

Good luck!

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"I had some eyeglasses. I was walking down the street when suddenly the prescription ran out." - Steven Wright

Where can I buy prepsol?

Thanks for the suggestions...

My comments are twofold:

Make sure you have no oil on the fillets. That means fingerprints as well as anything else. We modelers have a habit of checking the fillets for smotheness with our fingers. But that just lays down a layer of oil right where we don't need it. Don't. Then use prepsol or some other prep solvent before painting.

Next, make sure your dope is plasticized. Brodak dope is pretty good as-is, but if you are having problems, add a little flex-all to the dope to make sure. With that, the butyrate dope should work absolutely fine. I am not a fan of using nitrate for a base, and butyrate dope does make a good finish.

What are your fillets made from and what dope are you using? That may help with the fix.

Prepsol is the name of an automotive pre-painting solvent that will remove grease, oil and masking tape residue without effecting most finishes. You can get it or a generic version at a paint and body supply store.

So far I have been lucky and have never had a problem, I use Aeropoxy fillets, sand them with 320 the next day, apply a coat of Brodak white primer, sand smooth with 320 and Brodak dope for the filler and finish.

Windy once told me that the best way to avoid this is to not spray the fillets directly....to rely on "overspray" from adjacent panels. He said that if the paint went on almost dry that it stood less chance of lifting.

See Ya

Where can I buy prepsol?

I've always found this odd, Len, that we have to avoid oily fingers in the fillet, and yet put plasticizer (oil) in the paint. I have had the problem too, till I started wearing rubber gloves at the fillet stage, cleaning with prepsol and don't use high shrink dope (especially Sig Supercoat) and don't use soft material (like spakle) for fillets, and better still, no dope paints at all. Besides all that, if it's a foam wing and no open structure, why use a paint that shrinks? I had one plane done with Sig, I sliced and re-did the fillets 3 times, finally what worked was some epoxy I tinted to match the dope! Man was I sick of that plane by then...

Eric V.

I bought some at an automotive part shop that also carried paints. Not sure if the chain stores carry it or not.

> Where can I buy prepsol?

Look for Dupont Prep-Sol Solvent #3919S.

I buy it at an auto paint store in my area (Ohio).

Use rubber gloves, open window, fans etc.

> Where can I buy prepsol?
Scott,

Try Baxter's Auto. I think DX330 is better though. Baxter's will have that too.

Here is what I do, I slice the bubble with a sharp exacto blade and peel it back just slightly and put a little thin CA in the crack. I then push down the bubble until the glue sets. This will get a little glue on the paint itself, don't worry, just sand lightly until the glue is off the paint. Now just touch up the paint. After the clear is put on you should never know that you had to slice a bubble. Basically I just glue the bubble down.

On a few planes I used Super coat just over the open bays and Lite coat everwhere else. But still, the colored dope is Super coat.

How do you match the automotive colors to what you already have?

I was going to try that company that just sells pigment and them mix my own using Lite Coat as the base. That just seemed like too much work.

My fillets are epoxolite. Everything is fine until I spray that last few coats of clear...

I dunno....

First off, SIG's colors are all non tautening. However, sometimes we need a little more. The easiest is to add a little plasticizer to your dope unless you need to mix a certain color that is simply not available. The Warbirds are the biggest headaches in trying to find appropriate colors, and sometimes one needs to mix his own to get the proper blend there. But if you are happy with what is available, just add plasticizer (Dave Brown's Flex-all comes to mind, but automotive plasticizers used for lacquer will also work).

Ok, while we're at it, I have some "Acryli-Clean", DX 330, by PPG. It is equivalent to Prep-sol? I've had good luck with it, but still not really sure.

Tools

I like DX330 better than Prepsol. Sikkens M600 is touted by some to be the "Cadilac" of degreasers for wet sanding dope but I haven't found any of that in my local area.

IMHO Dave

LAST EDITED ON Feb-03-04 AT 00:21 AM (CDT)
 
In further answer to your earlier question, I found Prep-Sol around here (Cleveland area) only at stores that advertise Dupont products in the yellow pages. Others wanted to sell me competing brands.

I have painted with Brodak butyrate dopes - clear and colored - over both epoxolite and 30-minute epoxy with microballoons (West 407) with equal success. I sand the fillets with fine sandpaper wrapped around a dowel to remove the surface coating that results from the filleting setup and smooth/contour the fillets. Then I paint just the fillet with brushed 50/50 thinned clear dope. Afterward, while blending the fillet finish into the model surfaces, I minimize overlap of coats across the seams. When spraying color, I have not then had any lifting or bubbling problems.

I hope this photo works:

Jon,
Ok here is a tip that may help many of you and why they seem to have trouble with Epoxolite fillets.

Never, ever sand fillets with anything finer than 320 sandpaper. Actually, I use 220 3M Tri-Mite to sand the fillets after they harden for 48 hours. The 220 sandpaper leaves the surface of the Epoxolite slightly rougher and allows the paint to get a better grip on the fillet. The surface of the fillet is easily filled with two or three coats of Sig nytrate dope. The box label Magnum (blue) still has perfect fillets as well as many of the other models hanging from the rafters.