Author Topic: Clear Dope Over Colored Dope? (Read 7427 times)

Chancey Chorney · « **on:** October 12, 2015, 07:29:38 PM »

Ok. This should be the last question I have over my simple build. I think I have spent more time asking questions here regarding this simple 1/2a profile than I have time in it. Anyways, on with the question. I have applied 2 unthinned coats of butyrate clear dope on the whole airframe. I waited till dry and sanded with 400 grit sandpaper till the finish was dulled completely. I am planning for a natural woodgrain finish on a majority of the model with definitely one and possibly two different colors of 'accent' and striping on it. Now I will say that the clear and colored dope are all Sig Butyrate Supercoat dope. Is it best to do a full clear coat again before doing my color coats and only on the areas wanted, OR, do my colored 'artwork' then clear over the whole thing or just clear where there is no color dope. As a final coat, and a first color coat, is it alright to thin it 50/50, or is full strength better? I apologize in advance for this probable simple question, but a search later, I did not find anything regarding this. Thank you in advance for any and all help regarding this matter. I will at least have this under control for my first full fuse built up project coming up, so there SHOULD be less questions on it.

Avaiojet · « **Reply #1 on:** October 12, 2015, 07:52:34 PM »

Chancey,

I have absolutely no experience applying colored dope, yet.

However, I have painted a few airplanes, a bunch in fact.

I always applied the clear coat last over the entire model colors and all.

Are you sure that clear is fuel proof?

Charles

Edited: Applied the clear coat by spraying not by brushing.

Chancey Chorney · « **Reply #2 on:** October 12, 2015, 08:16:15 PM »

I have only read everywhere, as well as the label on the jar and it states Fuel-Proof. I am using Sig Butyrate exclusively, and I am running them pesky .049's so I will let you know.

Randy Powell · « **Reply #3 on:** October 12, 2015, 09:16:18 PM »

Fuel resistant, rather.

Chancey Chorney · « **Reply #4 on:** October 12, 2015, 09:33:25 PM »

Yes, so I have heard. I believe that the bottle does say fuel proof, but that is probably to a non nitro fuel. I am slightly concerned about this, but I do always wipe down my planes after flight.

Tim Wescott · « **Reply #5 on:** October 12, 2015, 09:52:19 PM »

Every time that I've tried to brush clear over colored I've just ended up dragging color all over. If there's a way to do it successfully I'd love to hear about it.

I would decorate with colored tissue (Sig used to carry it and may still, Easy Built and just about any other place that caters to the free flight trade still does). Then paint over that with clear.

Dane Martin · « **Reply #6 on:** October 13, 2015, 07:54:56 AM »

Tim's got it right for sure, don't brush the clear over the color. And if i may offer another fun thing to do... If you have already purchased the colors and want to use them, you may want to take the airplane down to the local body shop. Ask them to clear the plane for you. Most shops have something always set up for clear. I've done that a few times and they have done my 1/2A planes for free and i tipped the guy.
Be ready to talk about modeling though, they will be interested! Lol

Dennis Saydak · « **Reply #7 on:** October 13, 2015, 09:36:12 AM »

Two initial coats of dope are barely enough of a substrate for color dope application. I'd apply at least one more coat of clear and possibly more depending on how much you've sanded off and the amount of thinner you use for the next coats. NEVER brush clear dope over colored dope as it will make a mess, guaranteed. You will need to spray clear dope over any color trim. Better yet, use a rattle can of Minwax clear gloss poly to overcoat the entire model. That will provide additional fuel resistance more so than dope.

Larrys4227 · « **Reply #8 on:** October 13, 2015, 10:30:09 AM »

Does the Minwax clear gloss poly yellow over time? Got a brushed dope plane thats almost ready for clear ... have been undecided on how I want to do it, but i know not to brush the clear on. Minwax may be the simpliest.

Balsa Butcher · « **Reply #9 on:** October 13, 2015, 12:21:10 PM »

Easiest way in this situation is to brush on a few more coats of clear, thinned 50% or so until it shines then apply trim using either monokote trim sheets or better yet, thin sign vinyl cut to shape. You probably can get scraps for this purpose from local sign shop for free or minimal $$. That's it. The sign vinyl will actually stick better than the monokote trim sheets but if either starts looking a little worn, just replace.

Sig dope is not completely fuel proof but no dope is and Sig is better than most. No big deal, it's been used in this application for years and as long as you don't spill raw fuel over it will hold up OK. As for applying clear over color, one pretty much needs a spray rig/compressor for that. A good investment if you are going to stay in the hobby/sport. Brushing over color will soften the color and make a mess.

For next time: If your model has a light structure, use Lite-Coat Clear. It doesn't shrink as much as Sig Super Coat. Colors are labeled "Super Coat" but will not shrink like Super-Coat clear. Shouldn't be an issue with a solid profile, even 1/2A size, but something to consider for the next model.

Paul Wood · « **Reply #10 on:** October 13, 2015, 01:17:32 PM »

Quote from: Larrys4227 on October 13, 2015, 10:30:09 AM

Does the Minwax clear gloss poly yellow over time? Got a brushed dope plane thats almost ready for clear ... have been undecided on how I want to do it, but i know not to brush the clear on. Minwax may be the simpliest.

Larry,

Minnwax polyurethane is fuel resistant and will yellow over time. But, unless your base color is white, you'll probably never notice the yellowing. It is heavy so you have to be careful with the application. Polycrylic is a different animal. It is water based, will not yellow, but is NOT fuel resistant.

Larrys4227 · « **Reply #11 on:** October 13, 2015, 02:12:18 PM »

Quote from: Paul Wood on October 13, 2015, 01:17:32 PM

Larry,

Minnwax polyurethane is fuel resistant and will yellow over time. But, unless your base color is white, you'll probably never notice the yellowing. It is heavy so you have to be careful with the application. Polycrylic is a different animal. It is water based, will not yellow, but is NOT fuel resistant.

I have also been tossing around the idea of thinned Brodak Crystal Clear in one of those Preval Sprayers you can get at the box stores

Chancey Chorney · « **Reply #12 on:** October 13, 2015, 03:31:43 PM »

Well,I don't know where to start.
@Dane Martin - I am familiar with the use of automotive clear, and as Dennis remembered, I am a bodyman by trade. I am still in the industry, just working on bigger things and we do not use clear very much. But I still have connections in a few shops. Thank you.

@Dennis Saydak- Thanks for the tip of putting one more coat. I did brush my first two on relatively thick, and unthinned. After my light sanding, I did not see anywhere broken through. But I will heed your advice and clear the entire model once more before the color coat is applied. I am thinking I have enough left to do this. I will take a look before proceeding. I have to make my way to the aircraft supplier to get my next batch of dope if there won't be enough. Thank you.

@Balsa Butcher - I have access to the cutoffs as a friend has a cutter still, I believe. I will call him up, as I had not actually thought of doing it that way. Thank you.

Dennis Saydak · « **Reply #13 on:** October 13, 2015, 04:04:57 PM »

Quote from: Larrys4227 on October 13, 2015, 10:30:09 AM

Does the Minwax clear gloss poly yellow over time? Got a brushed dope plane thats almost ready for clear ... have been undecided on how I want to do it, but i know not to brush the clear on. Minwax may be the simpliest.

Larry, the can says may amber over light colors. I don't know if this means the Minwax clear is slightly tinted or if it ambers over time. It really shouldn't matter a whole lot on a 1/2A sport model as it provides excellent fuel proofing. Here's a picture of Gretchn, my Halloween ride for this year. She was painted by my daughter with artist acrylic paint. I fuel proofed her (Gretchn, not my daughter

) with two light coats of Minwax, which went on very well.

Chancey Chorney · « **Reply #14 on:** October 13, 2015, 05:01:06 PM »

Quote from: Dennis Saydak on October 13, 2015, 04:04:57 PM

Larry, the can says may amber over light colors. I don't know if this means the Minwax clear is slightly tinted or if it ambers over time. It really shouldn't matter a whole lot on a 1/2A sport model as it provides excellent fuel proofing. Here's a picture of Gretchn, my Halloween ride for this year. She was painted by my daughter with artist acrylic paint. I fuel proofed her (Gretchn, not my daughter ) with two light coats of Minwax, which went on very well.

Wow. That looks so cool Dennis. You both did a great job on it. It is looking like I am going to have a pit stop on the way home from work one day this week. If I may ask, where do you buy yours?

Dennis Saydak · « **Reply #15 on:** October 13, 2015, 05:23:45 PM »

The can I have belongs to another club member who often builds at my place (P.G.). I'm certain you can buy it at any Home Depot type store. It has a new type of spray nozzle compared to what I'm used to. It sprays a very fine mist, that is easy to control.

Chancey Chorney · « **Reply #16 on:** October 13, 2015, 05:45:51 PM »

No worries Dennis, thank you. I was thinking the same, Home Depot, Canadian Tire.

Chancey Chorney · « **Reply #17 on:** October 13, 2015, 05:50:59 PM »

Hey there again Dennis. I found this at the Home Depot online. Would this happen to be the stuff?

Chancey Chorney · « **Reply #18 on:** October 13, 2015, 08:25:52 PM »

Ok. So I tried some Lacquer thinner I had, and it turned my clear dope milky! So, I will write this one off as not to use. Probably would still be good to clean with. I will talk to a friend possibly tomorrow to see if I can try a different lacquer thinner.

Dennis Saydak · « **Reply #19 on:** October 13, 2015, 10:06:56 PM »

Quote from: Chancey Chorney on October 13, 2015, 08:25:52 PM

Ok. So I tried some Lacquer thinner I had, and it turned my clear dope milky! So, I will write this one off as not to use. Probably would still be good to clean with. I will talk to a friend possibly tomorrow to see if I can try a different lacquer thinner.

Yes that's the exact Minwax can I have. It sprays very nicely and can take a long time to dry completely to the touch, like 24 hours. The milky appearance is called blushing and it happens more easily with cheap thinner. The main cause is high humidity. Retarder is a slower drying thinner that prevents/eliminates blushing. Use cheap lacquer for non critical jobs like cleaning spray guns.

Chancey Chorney · « **Reply #20 on:** October 14, 2015, 04:03:46 PM »

Test two later today. I picked up MEK today to try. If this doesn't work out, I will just buy Randolph thinner too.

Dennis Toth · « **Reply #21 on:** October 14, 2015, 06:41:06 PM »

Chancey,
If you are going to use dope you need to always add thinner even to the first coats. For a clear wood finish you should thin 50/50 and apply 4 brush coats on all the wood. Block sand with 320, wipe clean with a tack rag. The color should be sprayed. Go to Home Depot and get a Preval Spray unit (a self contained spray head and paint jar - about $5). Mix your color dope 50/50 (use either Sig or Brodak or Randolph thinner). Tape off the trim you want (use cheap store brand aluminum foil and Blue painter tape to cover the other areas), you can use a coat of white primer where the color will go. Lightly sand the primary then start spraying your color light coats, likely need two sprayed coats. Since you've worked with the body shops if you start to get blushing get some retarter (don't add more then 10%). Once you get the coverage you want let it dry a few days, put any decals on you want then spray a light 60/40 clear coat over the whole ship, let dry then do one more full clear coat. Let dry for a couple weeks then you can fly. The clear coat is needed to seal the color.

Best, DennisT

Chancey Chorney · « **Reply #22 on:** October 14, 2015, 08:25:16 PM »

Ok. Well test #2 is complete. Now along with it, I preformed a test #3, due to a flaw I had found while performing test #2. This flaw also relates back to test #1, so test #4 has just been completed. I will get to the flaw after writing my test numbers.
Test #1 - Sig Butyrate and lacquer thinner, mixed in plastic shot glass. Result - blushed/cloudy/foggy
Test #2 - Sig Butyrate and MEK, mixed in plastic shot glass. Result - blushed/cloudy/foggy
Test #3 - Sig Butyrate and MEK, mixed on bottom of tin can. Result - Clear, honestly shinier than pure unthinned butyrate
Test #4 - Sig Butyrate and lacquer thinner, mixed on bottom of tin can. Result - Still clear, but will let dry completely

So, while performing test #2 is when I had noticed that my mixture was equally as cloudy in the plastic shot glass as was test #1. So I was thinking, could this be an issue, mainly the one causing my cloudiness? I did not have anything else to mix in, so I cleaned the pop can underside and mixed in the bottom hollow. Then as soon as I started mixing, the darn ink numbers mixed in with the stuff. I wiped out the bottom of the can and redid the test. Success, for the moment. I had to run out for a bit, and when I returned, it was still shiny. I was happy. And it appeared shinier than just the pure unthinned dope. So, after seeing this, I went and redid test #1 again and it is looking promising as well. I will keep posting as it goes. I will also mention that I am mixing small batches (2 drops of each) in the hollow of the can, mixing using wooded stick, and applying with the same.

Dennis Saydak · « **Reply #23 on:** October 15, 2015, 10:29:32 AM »

Chauncey, your tests were likely totally unnecessary and you have provided the answer to your problem. Never mix dope or lacquer thinner in a plastic container. The plastic will dissolve contaminating your paint. That's why dope or thinner doesn't come in plastic containers.

Chancey Chorney · « **Reply #24 on:** October 15, 2015, 02:53:12 PM »

Yep, now I know. Well at least on the bright side, I did learn something without causing myself extra work. Only a bit of lost time. And now, a bit more knowledge.

On another note, is it safe to store a 50/50 mix of dope and thinner together in the Sig jar, or even a sealer jar? Or is it best practice to just mix what you will need in the short near future (ie. One week)?

Dennis Saydak · « **Reply #25 on:** October 15, 2015, 04:22:04 PM »

Yes you can store thinned dope for a loooong time.

Chancey Chorney · « **Reply #26 on:** October 15, 2015, 04:27:13 PM »

Awesome news. Now to go mix up some clear and apply. Add color on Saturday, then pick up my clear Saturday night then spray that on Sunday, possibly, if all has set up by then. Thank you Dennis.

Dennis Toth · « **Reply #27 on:** October 15, 2015, 04:36:49 PM »

Chancey,
You can store the thinned dope in a sealed container without any problems, all that will happen is thinner does very slowly (like over a year or so) to where you would need to add a little to get back to 50/50. I use qt glass tomato sauce jars that I cover the top with Saran wrap then put the top on very tight.

One thing you might try for your tests is to do a test on strips of aluminum foil (old Windy tip) with the mixture of different amounts of thinner and retarter. The blushing is a factor of humidity. If the relative humidity is less than 70%, just the thinner is OK, above that you need either slow thinner (if you get thinner from an auto body shop they will ask what ambient temperature you intend to paint at) or a bit of retarter.

Good luck with the project.

Best, DennisT

Chancey Chorney · « **Reply #28 on:** October 16, 2015, 05:53:46 PM »

15-10-2015 : Ok. Final coat of dope and color were added this evening. Now I just have to wait until Saturday evening to get my hands on a can of clear spray. I will then hopefully spray that Sunday morning. AUW till this evening is at 4 3/4 oz, that is all hardware, motor mount, engine and prop. I hope the Babe Bee will do alright. I just want a nice little relaxing flier.

16-10-2015 : Ok. Well back from outside yet again. I took the advice of Dennis Saydak and went out and bought a can of Minwax Polyurethane Clear today and just sprayed on a coat. I will have to let it sit and dry a bit before assembling the plane. I cannot wait to take a few pictures when it is completed. Anyways, just a little progress update.

p.s. Both of these messages were posted on my thread under the 1/2a building forum, just in case you seen it there first.

Chancey Chorney · « **Reply #29 on:** October 16, 2015, 06:20:06 PM »

Thanks all for the help in finally getting a nice finish on an airplane using new to me techniques.