Author Topic: Clear Dope Lifted Up from Fillets (Read 2981 times)

Dick Pacini · « **on:** March 31, 2014, 11:07:45 AM »

I had some nice Hobby-Lite fillets on the Coyote fuselage where the cheek cowls meet the body. Everything was sanded and cleaned. I put a coat of nitrate clear on yesterday and another coat this morning. It looked really good.

I just checked the work and found that the clear had lifted off the fillets. I had to scrape and sand the dope away and I need to add some more Hobby-Lite to blend it in.

I picked up a can of clear Minwax Polycrylic and need to know if it can be applied over a doped/sanded surface. Will it stick to the fillet or will it lift too?

Avaiojet · « **Reply #1 on:** March 31, 2014, 12:56:18 PM »

Dick,

I'd be interested in seeing what a Hobby-Lite fillet is?

Charles

Dick Pacini · « **Reply #2 on:** March 31, 2014, 02:09:44 PM »

Quote from: Avaiojet on March 31, 2014, 12:56:18 PM

Dick,

I'd be interested in seeing what a Hobby-Lite fillet is?

Charles

http://www.hobbico.com/accys/hcar3400.html

Tim Wescott · « **Reply #3 on:** March 31, 2014, 02:32:21 PM »

Quote from: Avaiojet on March 31, 2014, 12:56:18 PM

Dick,

I'd be interested in seeing what a Hobby-Lite fillet is?

Charles

http://lmgtfy.com/?q=Hobby-Lite+Filler

Dick Pacini · « **Reply #4 on:** March 31, 2014, 02:41:17 PM »

Quote from: Ty Marcucci on March 31, 2014, 01:14:16 PM

How many days did you let the fillets gas off? Usually once they have cured for a few days, the Nitrate does the job, just make sure NO covering goes over the fillets because as it and the dope shrink, the covering will pull away trying to get level.

I don't think there is anything to gas off. Hobbylite is water soluble and drys in minutes. However, they did sit overnight before the first coat of dope.

I used the dope straight from the can. Maybe if it was thinned a bit, I would have had better results.

RC Storick · « **Reply #5 on:** March 31, 2014, 03:19:09 PM »

My suggestion is sand it clean, dust on DC540 primer. When your painting fillets do not spray directly on them. Just let the over spray cover them. At no time get them wet. Good luck

Dick Pacini · « **Reply #6 on:** March 31, 2014, 03:31:06 PM »

No spraying on this model. Brushing the clear dope.

Dan McEntee · « **Reply #7 on:** March 31, 2014, 03:31:48 PM »

This stuff is the same thing as hardware store spackling compound. On concave surfaces like fillets, it will lift off as the dope shrinks. Been there and made the mistakes. On all fillets, I use finish cure epoxy mixed with micro balloons and have never had any kind of paint lift off of it. Any off the other kinds of fillet material mentioned over the years will work better also. I like to use the epoxy/micro balloon method as it adds strength to the joint you are filling and is easy to work with. I mix just a small amount of epoxy in one of those small graduated mixing cups, maybe 1/4 ounce or so, then start adding and mixing the micro balloons until I get something like cake icing. Then I apply it with a round applicator of somekind working it smooth as I go. Adding the micro balloons really slows down the cure time, but I think that is an advantage to give you time to work. By itself it cures in 20 minutes or so, but after mixing, it can be an hour or more, and the volume quadruples, almost filling the cup. Once you see the stuff starting to get tacky by playing with the leftovers, you can dip your finger in some alcohol and smooth the edges down top nothing and have them where you don't need to sand them at all. Do a search on the list here of my name and I'm sure I went into more detail on other occasions. Just don't have time for more right now.
Good luck and have fun,
Dan McEntee

PS To Add; I think this stuff is vinyl, like the vinyl spackling compound at the hardware store. I think it is just a complete incompatibility issue.

bob whitney · « **Reply #8 on:** March 31, 2014, 03:51:39 PM »

epoxy and micro balloons works for me just keep paint buildup to a minimum

Tim Wescott · « **Reply #9 on:** March 31, 2014, 03:52:36 PM »

Quote from: Dick Pacini on March 31, 2014, 03:31:06 PM

No spraying on this model. Brushing the clear dope.

Somewhere on this forum I read something from someone (there, isn't that nice and specific?) that if you're brushing, the way to dope fillets is to paint along each edge, leaving the middle un-painted. Then let everything sit for a while (I think it was a day or two), then paint the middle. The guy reported 100% success, but then I don't think he was painting over spackle.

Dick Pacini · « **Reply #10 on:** March 31, 2014, 05:21:34 PM »

Quote from: Dan McEntee on March 31, 2014, 03:31:48 PM

This stuff is the same thing as hardware store spackling compound.

PS To Add; I think this stuff is vinyl, like the vinyl spackling compound at the hardware store. I think it is just a complete incompatibility issue.

Dan, have you ever used it? It is nothing like spackling compound and it is made for use on balsa. It is almost like fine powered balsa.

Dan McEntee · « **Reply #11 on:** March 31, 2014, 06:36:23 PM »

Oh yeah, I've used it before. We sell it at the hobby shop I work part time at, and I think it's packaged under several other names. The can feels nice and light, almost like it's empty, correct? Check out the spackling compounds at the hardware store next time. I think the critical thing is the concaved surface. You might not have any problem on a flat surface. It may be that the dried surface of the stuff just doesn't allow for "tooth" and for the dope to stick. I can't remember if I tried primer or not, I just quit using it all together. After I read about the epoxy/micro balloon mixture and had such success with that, I've never tried anything else since. I would carve it all out as best you can and try something else. I know that's not what you want to hear, but sometimes the best lessons are the hardest learned.
Type at you later,
Dan McEntee

Tim Wescott · « **Reply #12 on:** March 31, 2014, 07:45:39 PM »

The stuff has almost no mechanical strength. I use it for filling divots in balsa before applying 'coat, but I would expect that having good adhesion to the stuff with dope would just mean that when the dope lifts it pulls the top layer right along with it.

Dick, the problem here is that dope shrinks. When you paint a fillet, the dope shrinks, and wants to pull away from the fillet. So you need fillet material that the dope will stick to, you need to not load on the dope (which makes the dope stronger in the "pulling away" direction without changing its adhesion), and you need fillet material that won't just crumble when the dope tries to pull it apart. Making the fillet radius large also helps (the sharper the bend, the more pull the dope has).

The fillet materials that I know of that work well are wood, leather, and epoxy with microballoons, either home-mixed or bought (Superfil is one brand name). I'm sure there are others. You want about a 1/4" radius or larger fillet -- a really teeny tight fillet invites bubbles as the dope dries.

Keep in mind, too, that seeing success after a day of drying doesn't guarantee success forever -- dope doesn't just shrink for a while, dope just shrinks. So you can have your fillets lift a year after you paint.

Dick Pacini · « **Reply #13 on:** March 31, 2014, 08:00:58 PM »

I think someone recently said to soak the fillets with CA if strength is required. My fillets are not sharp. They are about 5/16 radius.

I recall years ago that rubbing glue on fillets would reduce the lifting of the finish. This is nothing new. The best fillet is carved balsa, but a lot of work.

I picked up some Minwax Polycrylic clear today. Going to do the fillets over and try the Minwax.

john e. holliday · « **Reply #14 on:** April 01, 2014, 09:26:43 AM »

Good luck. That Super Fil is what I am using now and am thoroughly sold on it. I too have a tub of that lite spackling compound that I would never use for fillets as it has no strength to it. For flat surfaces it is okay, but there were some areas I had to add a second layer of compound to get the surfaces even. Thinned dope dope will soak into it some, but not enough for fillets. My opinion and experience. By the way Super Fil does add strength to the joints. Also get it smooth to start with as it is hard to sand. Used metal files when I first tried the stuff. You know live and learn.

Dick Pacini · « **Reply #15 on:** April 01, 2014, 10:30:18 AM »

Quote from: john e. holliday on April 01, 2014, 09:26:43 AM

Good luck. That Super Fil is what I am using now and am thoroughly sold on it. I too have a tub of that lite spackling compound that I would never use for fillets as it has no strength to it. For flat surfaces it is okay, but there were some areas I had to add a second layer of compound to get the surfaces even. Thinned dope dope will soak into it some, but not enough for fillets. My opinion and experience. By the way Super Fil does add strength to the joints. Also get it smooth to start with as it is hard to sand. Used metal files when I first tried the stuff. You know live and learn.

The fillets on the Coyote are not at the wing joint. They are at the balsa triplers where they feather into the fuselage sides. Strictly an appearance use. I have read that if strength is required, the fillet can be soaked with CA.

Tim Wescott · « **Reply #16 on:** April 01, 2014, 10:44:16 AM »

Quote from: Dick Pacini on April 01, 2014, 10:30:18 AM

The fillets on the Coyote are not at the wing joint. They are at the balsa triplers where they feather into the fuselage sides. Strictly an appearance use. I have read that if strength is required, the fillet can be soaked with CA.

Try your CA idea, and let us know how it works. I think you'll find that you'll have to sand just as much as you would a well-applied epoxy/microballon fillet, and that your dope won't stick nearly as well.

I have never seen one of the expert builders here recommend the combination you're advocating, and some of these guys go out and try different stuff just to see if it works. Chances are the reason it hasn't been suggested is because someone tried it and found that it wasn't at all satisfactory.

But, it's your plane.

Dick Pacini · « **Reply #17 on:** April 01, 2014, 11:32:41 AM »

Quote from: Tim Wescott on April 01, 2014, 10:44:16 AM

Try your CA idea, and let us know how it works. I think you'll find that you'll have to sand just as much as you would a well-applied epoxy/microballon fillet, and that your dope won't stick nearly as well.

I have never seen one of the expert builders here recommend the combination you're advocating, and some of these guys go out and try different stuff just to see if it works. Chances are the reason it hasn't been suggested is because someone tried it and found that it wasn't at all satisfactory.

But, it's your plane.

I am not here to re-invent the wheel. I am just trying to make the best of a poor situation and salvage the airplane by repairing a hiccup. I don't need the CA for strength in this application and it would have been applied after the fillets were sanded anyway.

I have spent way too much time on this model and want to move on to something else, but I need to "git 'er done." I will most likely stuff it in the pavement or in the trash can.

Dan McEntee · « **Reply #18 on:** April 01, 2014, 01:09:39 PM »

Hi Dick;
I have felt your pain! I went through all of this before the internet was ever invented! I thought that was a light, quick way to easy wing fillets. I don't remember if I ever tried to apply CA to the fillets in an effort to get dope to stick or not. Try it in a small, inconspicuous place and ope over it to see what happens. I think the epoxy/micro balloons works because even though it feels as smooth as a baby's but, it's porous and give the dope something to grip onto. More micro balloons than epoxy. try the CA trick and report back. It may help some one else with the same problem.
Good luck and have fun,
Dan McEntee

Dick Pacini · « **Reply #19 on:** April 01, 2014, 01:41:42 PM »

Quote from: Dan McEntee on April 01, 2014, 01:09:39 PM

Hi Dick;
I have felt your pain! I went through all of this before the internet was ever invented! I thought that was a light, quick way to easy wing fillets. I don't remember if I ever tried to apply CA to the fillets in an effort to get dope to stick or not. Try it in a small, inconspicuous place and ope over it to see what happens. I think the epoxy/micro balloons works because even though it feels as smooth as a baby's but, it's porous and give the dope something to grip onto. More micro balloons than epoxy. try the CA trick and report back. It may help some one else with the same problem.
Good luck and have fun,
Dan McEntee

We are a bit off track here. CA on the fillets was not suggested to make dope stick, it was to add strength to the fillet. Dang it, I just read that here within the last day or so. It makes sense. CA will toughen up balsa. It might have been in the old thread about the T-Rex when it was new on the market. Maybe from Brad Walker.

I am going to repair the fillets after having to gouge some out to remove the dope. Once repaired, I will try the Min-wax on the fillet. Just need it to look good enough to paint. If the Min-Wax sticks, I will post pics of the repair. That roll of Ultracote is looking better and better.

Dan McEntee · « **Reply #20 on:** April 01, 2014, 04:31:39 PM »

Quote from: Dick Pacini on April 01, 2014, 01:41:42 PM

We are a bit off track here. CA on the fillets was not suggested to make dope stick, it was to add strength to the fillet. Dang it, I just read that here within the last day or so. It makes sense. CA will toughen up balsa. It might have been in the old thread about the T-Rex when it was new on the market. Maybe from Brad Walker.

I am going to repair the fillets after having to gouge some out to remove the dope. Once repaired, I will try the Min-wax on the fillet. Just need it to look good enough to paint. If the Min-Wax sticks, I will post pics of the repair. That roll of Ultracote is looking better and better.

I'm curious if the CA will seal the filler and eliminate the possible material compatibility, and give it some better "texture" for dope to stick to. Depends on how it reacts to the filler. I remember trying all sorts of stuff but nothing worked. That has been twenty years or so ago, or more! Like I said, that was before the internet and I was just trying stuff looking for quick, easy and light...just like you probably were.
I hope it all works out to your satisfaction.
Type at you later,
Dan McEntee

Dick Pacini · « **Reply #21 on:** April 01, 2014, 06:01:06 PM »

I sanded the fuselage enough to remove or scuff the dope, then brushed on the Min-wax Polycrylic. It is ready for a second coat about now. Keeping my fingers crossed. I did not used CA on the fillets. I figured that would change the parameters comparing the dope to the Min-wax.

I really have spent too much time building this plane. Today, I got a letter from Social Security addressed to Mister Coyote...

Dick Pacini · « **Reply #22 on:** April 02, 2014, 08:07:26 PM »

Good news, I repaired the fillets and put 2 coats of Min-Wax Polycrylic clear on the whole plane, right over the scuffed clear dope. The Min-Wax stuck to the fillets and they look fine.

Dan McEntee · « **Reply #23 on:** April 04, 2014, 01:09:38 AM »

So, how goes it Mr. Pacini? Got an update on your progress with the current applications? Let us know how it's working.
Type at you later,
Dan McEntee

Dick Pacini · « **Reply #24 on:** April 04, 2014, 04:17:23 AM »

Going to sand today and hope to get the NAPA primer on over the weekend if the weather allows spraying outside. Working overnight tonight and tomorrow so sleep might take priority.