mouthpiec

Hi,
I had an accident with my trainer, and after i fixed the wings, i had to cover them again, but when i covered them, since i am not a pro, the plastic developed some wrinkles.
Will this affect the flight perfomance

thanks and regards
sandro

ArCeeFlyer

My Feedback: (1)

Not unless they are really big and floppy wrinkles. If the covering is still generally tight and the wrinkles are small, it shouldn't hurt anything. Obviously, aerodynamic wise, the smoother the covering, the better. Have you tried hitting it with the heat gun again? If there is any shrink left in those areas, it may come out with some concentrated heat. Just be careful not to melt it. If it's Monokote or Ultracote, it will take a lot. I think up around 500 degrees.

da Rock

Yes

The freeflight guys discovered any number of things that have importance to airplanes the size of our models. They discovered that they could change the performance measurably by changing things we'd never believe would matter.

They used turbulator strips for example. They made some of the strips by gluing thread along the span. Most times they had to make the strips thicker than that, but that gives you some perspective. I've seen a glider design that was good become great simply by covering the stabilator with different covering.

When they were putting turbulator strips on their wings they were trying to disrupt the airflow. The strips could do that. They were effective but had to be very accurately placed. They were tiny and had an effect. Obviously, they were flatter than your average Monokote wrinkle. (and larger than the average Ultracote one.... )

Some years back I flew with a guy who was always saying "that's good enough". One airplane in his stable (stable is really the correct term) was constantly stalling on him. I personally think it was trying to commit suicide, but he professed that it was just a crummy design. It wasn't. The wing looked pretty bad. One day, a couple of us were in his shop and whipped out his heat gun and worked on that wing, top and bottom. I'd suggest that if nothing else, that wing picked up twice it's previous rigidity. And guess what..... It still stalled..... sometimes...... but nowhere near as often.

Some of us will notice wrinkles on our models. Some won't. With our models' power loadings it's real easy for some of us to simply power through wrinkles, bad assembly, whatever.... and never notice the finer details.

Do you need to fix those wrinkles? Not if their appearance doesn't bother you. But they do have some effect.

ArCeeFlyer

My Feedback: (1)

I've done the turbulator threads before also. It was a heavy plane with fairly thin airfoils and the turbulators really helped reduce the stall speed on hot days. I agree fully with Darock. It's always best to strive for perfection. Although, being your plane is a trainer, you probably won't notice any effects from minor imperfections. Trainers are very forgiving, but it would be good practice eliminating small things like that so when you move on to more advanced planes it won't come up and bite you later.

da Rock

And the more important detail about wrinkled covering is that it's not giving the wing the support it would get from uniformly tight covering.

It's a fact that's often overlooked that the covering contributes to the strength of the wing. But it doesn't do it if it's not tight.

ArCeeFlyer

My Feedback: (1)

Another good point. That's why I like to iron the covering to the ribs, even though it's not as pretty, it adds strength from triangulation in 3 axis. Tight covering can also hold some added washout in the wings. If I would have to guess at a percentage of strength contribution from covering, my guess would be at least 30%.

Tall Paul

I'd be surprised if the typical trainer's "performance" could be affected in a noticeable manner by a few wrinkles in the covering.
These planes are usually not dependent on the covering for structural rigidity anyway.
If it bothers you, now that you how not to do it, you can redo it, or with a heat gun, try to see how many of the wrinkles you can get rid of.

mouthpiec

hi,
thanks for the help
today i tried it, performace remained the same!

thanks again

da Rock

"noticeable" is the key word...........

It's good that the effects aren't usually noticeable to most flyers, otherwise all the beginners would probably have moved on to RC cars or knitting or such.

And the guy I talked about who had such junky airplanes didn't notice that the particular one we smoothed out for him didn't flop in on landings as much or snap out of turns ever again. (It wasn't snapping in the air much, but did.... and then didn't.) But those of us who'd fixed that particular airplane noticed. And especially on his landings. He never did stop trying to bring them in at a walk. And all of his other ones were constatntly needing the gear bent back and such.

BTW, everyone agrees that the effects wouldn't be overwhelming. The changes in performance aren't large. And our models are favored by having a huge power loading that'll fly just about anything and can hide lots of minor defects. Heck, one of our club regular's airplane was flying with more than a half-inch of aileron deflection for trim. We heatgunned the big warp out of that wing, rigged the aileron trim that was fighting that warp back out of the ailerons, and he took off with his "new and improved" highwing, trainer type. When he landed, he told us we'd wasted our time, that the sucker flew just like it had before. Was that power loading or just him? And most of us actually had watched his flight to see if the airplane wallowed and wiggled like always and it hadn't. And he overshot his landing attempts until he finally pulled his idle trim back some. And then said it flew just like before. OK.... Hey, landing with a slower idle won't be noticed by many. Like we said, it won't be overwhelming. But it is there, which is what was said about it.

As for most trainers not benefitting from stronger wings????????? Seriously? They're already "strong enough"?