Is it really difficult to cover the Chrysalis wing using Monokote without getting wrinkles?

Is it just me, or is it really difficult to cover the Chrysalis wing without getting wrinkles? Any help would be appreciated. (I'm using Monokote)

From : Don Stackhouse

Well, Marty, it's not so much the Chrysalis, it's the Monokote. Monokote is an older covering, one of the very first iron-on films. At that time in history, its ability to go around 3-D curves was amazing to those of us who were used to Silkspan and butyrate dope. However, today things have changed, and a number of other coverings such as Ultracote or Oracover do a much better job of going around weird shapes. They also tend to be tougher and more split resistant. Unfortunately, they do this partly because the base materials aren't as stiff, so you either give up some flutter resistance or some weight in comparison to Monokote. The Monokote is an excellent choice because of its physical properties, but it is prone to wrinkles, especially around the wingtips. These can be minimized with expert technique during application, but it's tough to avoid getting one or two in the corners.

Cover the entire wing before you start shrinking the film tight. Cover the bottom first, trim the edges and iron them down, then cover the top. The bottom goes fairly smoothly with just four pieces to cover the four panels, but on top you will probably need to cover the upper side of the tips (between rib "O" and the tip plate edge) with a separate piece (otherwise it likes to wrinkle around the leading edge of rib "O"). Start each section by laying the covering in position, then sticking a small patch in place over the spar at one end with the tip of the iron. Now pull gently but firmly on the other end over the spar, and stick that end in place. Now tack a spot over the middle of the spar, then at the 1/4 and 3/4 points, then the 1/8, 3/8, 5/8 and 7/8 points, then tack the entire length of the spar. Now gently pull the covering tight in the middle of the leading edge and tack it down. Pull snug and tack down the corners at both ends of the leading edge, then the 1/4 and 3/4 points, etc.. Use the same technique for the trailing edge. Make sure the covering is stuck firmly to the entire surface of the trailing edge stock. Iron the covering down over the center section sheeting, and along edges of the "K" and "O" ribs and the tip plate.

Now start shrinking the covering gradually, starting with the corners and edges, then working to the areas in the middle. Do the bottom first, just enough to get the major slack out, then do the same on top. If you get some stubborn wrinkles around the leading edge on top, you may be able to re-heat the area where it's stuck to the edge and gently pull the wrinkles out. Trim the top covering and iron the edges down, then finish shrinking the bottom snug. Hold each section of the wing flat on your building board as you finish shrinking the top. Be careful not to overdo shrinking the area behind the spar, it's easy to buckle the tail ends of the ribs if you aren't careful. You can help avoid this by using the tip of the iron to stick the covering to the edges of the ribs before shrinking it up tight.

If you did a good job of holding your wing flat during the final shrinking, the washout (twist) in the tips should already be correct. Set the washout in the inboard panels as shown in step 52, once again taking care to not buckle the ribs behind the spar from overshrinking. It may take several iterations of shrinking the bottom, pinning it down and shrinking the top, re-shrinking the bottom, etc., before it settles into the correct shape. Also, get in the habit of re-checking the washout every few days or whenever the model doesn't seem to be behaving the same in flight. On new wings the washout likes to drift a bit until all the components and covering get used to each other. One of the drawbacks of a wing with adjustable washout is that it sometimes wants to adjust itself! After it's had some time to stabilize, it should settle down. It's like a new set of guitar strings; out of tune every few minutes at first, but after a week or two they hold a setting fairly well without a lot of readjustments.

In extreme cases you can always cut out the wrinkled area and iron on a patch. Be careful doing this or you can simply move the wrinkle to the next bay! ("Here, meet my Chrysalis, I call it 'Patches'")

Good luck, I hope this helps.

Don Stackhouse @ DJ Aerotech