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Prepping for clear coat

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  • Prepping for clear coat

    I have a new unflown EFlite Maule that I want to clear using Varithane exterior Spar Urethane. The plane is factory painted with stick on "decals" and some areas left white foam. I have studied the thread dealing with this product and am confused about the prep with 91% IPA. Do you rub down the plane including the painted areas and "decals" or mask them off and just do the white areas?
    I intend on cutting the Spar urethane 60/40 and spraying it through my Pasche model H air brush.
    Please let me know about the alcohol and the spraying!
    Thanks,
    Marc

  • #2
    Are you talking water based Varithane? I rub the unpainted and painted areas separately so as to not get color on the white. Rub the painted areas very lightly. I then use Grossman's technique. I use a very fine bristle brush to get a perfect finish. Doc

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    • #3
      Originally posted by doctormike View Post
      Are you talking water based Varithane? I rub the unpainted and painted areas separately so as to not get color on the white. Rub the painted areas very lightly. I then use Grossman's technique. I use a very fine bristle brush to get a perfect finish. Doc
      Hi Doc!
      Thanks for responding! I intend on using the water based Varithane Spar product exterior grade. Had I not read the other thread I would have used the Minwax and I am grateful I didn't. The comment about the Minwax being brittle and it's effect on the hinges made it a no go for me. As a matter of fact i am headed to lowes to exchange the Minwax for the Varithane as soon as I finish this post!

      What exactly is Grossman"s technique? Any other hints would be appreciated. Is using a terry cloth towel for the alcohol rub OK or would you suggest paper towels such as bounty? Have you tried cutting the Varithane with water? if so what percentage for brushing ? What are your thoughts about cutting with water and spraying through an air brush?
      Thanks for the help,
      Marc

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      • #4
        Been thinking about the painted areas on EFLITE models. Am I correct in assuming they were painted on over the foam with no regard to the release agent? If so then that would account for the fact that the paint comes off so easily. It would also mean that prepping with alcohol on the painted areas is wasted effort. If you just coat the painted areas with clear after no alcohol prep will the clear stick to the paint?
        Marc

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        • #5
          The Grossman technique: Brush on the Varathane. As you brush, move the surface around where you can get light reflection on it. This will show up places where the surface has resisted the Varathane. Any place that you see surface resistance, rub it with a paper towel. Sometimes rubbing it vigorously with the brush will get rid of it. Then re-brush it. Using the Grossman technique might eliminate the need for an alcohol rub down altogether. I've never had a problem with Varathane sticking to the painted surfaces. Brushing will give you a perfect finish. I do thin my Varathane a little bit. Not too much. Exactly how much, I haven't measured the proportions. Home Depot is the only place that I have found Varathane, other than on line. I, honestly, would not bother with airbrushing Varathane on. A fine brush will do the job. If you ever repaint a model, low gloss Varathane makes an excellent primer, even on Ultracote. GOOD LUCK! Doc

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          • #6
            Originally posted by doctormike View Post
            The Grossman technique: Brush on the Varathane. As you brush, move the surface around where you can get light reflection on it. This will show up places where the surface has resisted the Varathane. Any place that you see surface resistance, rub it with a paper towel. Sometimes rubbing it vigorously with the brush will get rid of it. Then re-brush it. Using the Grossman technique might eliminate the need for an alcohol rub down altogether. I've never had a problem with Varathane sticking to the painted surfaces. Brushing will give you a perfect finish. I do thin my Varathane a little bit. Not too much. Exactly how much, I haven't measured the proportions. Home Depot is the only place that I have found Varathane, other than on line. I, honestly, would not bother with airbrushing Varathane on. A fine brush will do the job. If you ever repaint a model, low gloss Varathane makes an excellent primer, even on Ultracote. GOOD LUCK! Doc
            Thanks Doc! I am wondering if rubbing the whole plane down with 4/0 steel wool, tack ragging the surface and then brushing on the Varithane might be another way to go. I am returning to R/C flying after many years. I was into the hobby when Monokote first came out. We used to rub with the steel wool before painting on it-That worked!

            I would prefer a dry prep as opposed to the alcohol! No issues with paint bleeding over to the unpainted areas and no worries about the contact paper decals. You are quite right about Home Depot as a Varithane source. None of the local HDs or Lowes had it so I ordered it on line to be delivered to the store.The way the on line order sheet reads you get 2 quarts that way as opposed to one quart when ordering from Amazon.
            I'll post my results after i decide on which method I'm going to use.
            Thanks again,
            Marc

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            • #7
              Hey Marc, I wouldn't say steel wool is necessary. I typically apply WBPU or Varathane-type coatings straight onto the model with a foam brush with a minimum of strokes. I've yet to have any adhesion issues.

              0/0 may be more advisable than 4/0 if you're set on using some sort of dry surface prep with steel wool. A little goes a long way, especially if you're only clearcoating the stock paint job. I'd recommend testing on some scrap foam first to see how the different grades affect the final finish.

              Post your results!
              ​​​

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              • #8
                You don't need to use steel wool. Just follow the tried and true technique. Doc

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                • #9
                  I just purchased a motion P-38 in green. I want to put invasion stripes on it. Any suggestions on what kind of tape and paint to use ?

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                  • #10
                    Do NOT use steel wool with any water based product, unless you want rusty looking freckles in your finish.
                    No need to waste time with a sprayer - this finish came from a foam brush (disposable) over 0.5 oz fiberglass cloth. I have used the Minwax on my new foam models and brush is the way to go- dries as if sprayed.
                    Attached Files

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                    • #11
                      Hi Guys!
                      Well not a great report! The 91% alcohol dissolves the paint Eflite used so no go with that. Not terrible because I tested it first in an inconspicuous place so no damage. Then i rubbed the bottom of the unpainted stab with the alcohol very carefully and very thoroughly. I then coated it with a very fine camel hair brush and used the light as Doc described as the Grossman method. It came out like a bad poker hand-Aces and spaces!! I tried the rubbing with a towel and rubbing with a brush to no avail. I became anxious about it drying like that so I took damp Bounty towels and rubbed the entire surface . Funny thing -All that did was to take it off. Good news is it looks fine,as if it had never been done.
                      The red painted rudder took the poly OK but really didn't look that good, The fuse has large areas of white unpainted foam bordering large areas of red painted foam. Since the rudder came out just ok I decided not to paint the fuse. Not worth the trouble.

                      Just to confirm I used water based Varithane spar urethane outdoor.
                      Thanks for the help,
                      Marc
                      PS-The finish did not take to the decals either!

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                      • #12
                        Well I painted the fuse anyway and it came out ok!
                        The release agent on the white unpainted area is really stubborn. I just can't get it off and have decided to leave it uncoated. Thanks for your help!
                        Marc

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                        • #13
                          Oh my, once again, take the Minwax coat it on the white, unpainted area, it will ball up, wipe it off with a rag, and let dry, repeat until it doesn't ball up again. The release agent is oil based, the Minwax is water based (assuming you're using water based) oil balls up in water, it's the easiest way I know of to get rid of the release agent.
                          Then, if I want to leave the surface white, out with the Sample pint from Ace which I just left white, or good old left over house latex white, either works great.

                          Grossman56
                          Team Gross!

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