I am finally getting around to covering my son’s Midwest Super Stearman. I have covered a Sig Hog Bipe and a mini Ultimate Bipe before with absolutely no issues. I used the really good RC universe tutorials as a guide.

I am setting the iron at 220-230 degrees. I started with the control surfaces (aileron). I provided a pic so you can see how it is built up.





I am using the exact techniques that are in the videos tutorials. I am tacking first around all the edges and then sealing the edges. I am trying to remove as many wrinkles as possible by pulling around the edges before tacking with iron. Once that is done, I start to hit it with the heat gun. This is where the problem happens. I get around 4 to 5 inches away from the aileron and start to move in a side to side movement, making sure to stay away from the edges. The wrinkles start to magically go away and I am thinking this is a beautiful thing. As soon as I stop blasting with the heat gun and let it rest for a few seconds the wrinkles start to come back. They don’t all come back, but it definitely is not drum tight. So I hit it with some more heat, only focusing on the areas that are loose and wrinkled. It will go away again. I will let it rest and guess what, the wrinkles come back.

What the heck is going on? Please help!!!

Joe

Joe, you need to allow for the hot air that's being trapped in the structure while you're heating it up. Try to drill one small hole through the aileron between two of the "ribs" and then one hole through each "rib" side. This will allow all of the built up pressure from the heat to escape while your shrinking and sealing the covering. Looks like he did a heck of a job building that beast!

catracer may have it. I always make sure that I have no trapped air or sealed compartments anywhere on my aircraft. I will drill 1/16" holes between all compartments that may trap air. I have seen aircraft at the field in the hot summer sun actually "baloon" the covering material due to heated trapped air pockets.

Bill

Here's a diagram that I drew up real quick to show you what I mean...

Joe,

First of all, thank you, I'm the one who did those RCU articles and videos.

A good way to describe the problem you're having is to imagine that you have a quilt on your bed with a big wrinkle in the middle - You slap your hand down on it and two wrinkles appear on each side of it. You slap those down and the original wrinkle appears.

The only way to get it out is to grab the edge of the quilt and pull it flat.

Same thing applies here.

Instead of heating the wrinkle, try heating the areas on both sides of it. So instead of shrinking the wrinkle, those areas will shrink and pull the wrinkle out.

That piece you're doing is small, but tricky. Here's how I would do it:

First and foremost, drill a tiny hole in each rib and in the LE to give trapped air a way to get out.

Now cut a piece slightly wider, but about 2 inches longer than the aileron. Lay the covering over the aileron so you have most of the excess on the curved end.

Iron it down along the straight portion, but leave it loose over the last bay.

Weight it down tightly (Or have someone hold it down) and heat the end with a heat gun while pulling the covering with a gloved hand. This is exactly the same as how I did the wingtip in video #4.

Bullseye, I have used UltraCote on several builds and it is far easier to get a good job with Ultracote than with Mono...... I use a covering iron. I think you will have better results with the iron than with the gun. Your temp control is much more consistent. Make sure you calibrate your iron. I take a kitchen digital thermometer and find the dial location that corresponds to about 230 and 330 degrees. Apply the covering at the lower setting as you mentioned. Go back over the complete structure at the low setting. Then tighten to remove wrinkles at the higher setting. And as mentioned above, you must relieve gas build up in hollow structures. Also, if I have gas bubbles form at the higher temp setting when tightening the Ultracote over a solid surface area, I use a very small pin and poke several holes in the area that forms the bubbles. After the job is completed you will not see these tiny pin holes.

Thank you so much for all the great info! I never thought about the trapped air. I am gonna try all the techniques tonight.

Wish me luck,

Joe

I second what Airbusdrvr said. I think Ultracote is far easier to use than Monokote. BUT, I never use a heat gun on it, only the iron. You also have stay away from the seams when you're skrinking it.

I just wanted to give an update. Using the techniques posted on this thread solved all my problems! I am so happy to see these great results. Big thanks to all you guys!!!!!

I am also a huge fan of Ultracote. I only use Monokote when I am using the windex method. I tried using Monokote with a heat gun and iron a few years ago and made a promise to never do that again. Not forgiving at all.



Joe