redford

My Feedback: (6)

I'm not new to covering with Monokote, but I'm still having trouble with concave curves - specifically right now, the leading edge of the vertical tail fin near the fuse. I've searched for a thread on this, because I know that many Monokoting techniques have been discussed, but I can't find anything dealing with concave curves.

I chose to attached the tail feathers before covering, to avoid the separations between the parts when covering the individual pieces first. I've covered the fuse, with a u-shaped cut-out for the fin. That worked well. I also put the fillet pieces of Monokote down first. Now, it's time to cover the fin itself, and I just can't get a nice smooth finish on the leading edge. Any tips to help me?

Thanks!

KidVermin

My Feedback: (3)

After sealing one side of the vertical stab, leaving a 1/4" to 3/8" overhang all around. At the concave area, scissor cut slits toward the fin spacing about 1/2" apart. Stop the slit cut to about the centerline of the stab. Seal the slit tabs down and repeat for the other side making sure to offset cuts from the sealed side to prevent exposed balsa once sealed.

I've found the 21st Century iron with the convex base works best in these curved areas.

J_R

Keep two facts in mind when covering concave and convex areas with films. The shrink and they stretch. Sometimes, it is a matter that there is too much material, such as when covering a wing and doing the tips. In this case, you want to shrink the film before you apply it, then stretch it tight, both using heat.

If I understand the problem with the fin, this may help. Cut slots in the film. Not the part that will be covering the fin, but almost up to it. Then pull on the triangle shaped pieces as you heat them. Be careful not to pull too hard, as the slots will rip. A small trim iron works better than the bigger sealing iron for this. Work slowly, maybe an 1/8 of an inch at a time.

redford

My Feedback: (6)

J_R-

I know you're exactly right - I need to "shrink the film before I apply it" in this area on the fin. The tip (from both you and rreiss) to slit the film is a good one, and how do I shrink it before applying it?

MinnFlyer

My Feedback: (4)

You do NOT want to shrink it before applying it.

Iron the film down to the flat surface, then heat the area of the slits and pull them to stretch them, you will need a helper or you might break the fin off the plane. (It takes some good pulling)

Remember, film STRETCHES as well as it shrinks.

rajul

My Feedback: (58)

Redford, here are links to a few references that include techniques for concave/convex surfaces, and a host of other essential techniques as well.

http://www2.towerhobbies.com/cgi-bin...?&I=LXL794&P=0

http://www2.towerhobbies.com/cgi-bin...?&I=LXZ866&P=0

http://www2.towerhobbies.com/cgi-bin...?&I=LXHZ84&P=0

FWIW and good luck

J_R

MinnFlyer is absolutely right. Initially, I was not sure if you were talking about covering fillets between the stab and fin, or covering the fin. Film will stretch to the point where it gets almost transparent, then it rips.

There used to be a guy that went to modeling shows and covered planes with only a heat gun. It was quite a show. I have not seen that done for some time now.

The second link that rajul supplied is to Faye Stilly's books. They are a tad pricey for a magazine priced book, BUT, they are the best, IMHO. They have saved me more rolls of film then I care to think about.

redford

My Feedback: (6)

Thanks for all the good suggestions. I'd already read all the references provided, and some others, but I'm still learning things about Monokote every time I use it. I've almost finished covering my current project (BTE Venture) now, and here are the things I learned this time (I've never seen these, stated this way, in the books - or, they were stated between the lines and some emphasis here might not hurt...)

1. Pre-cutting and laying the film down in the first place is very important. You can't take out the worst wrinkles, or get the film to tighten properly, if the film is off-kilter at all. Think before you start!

2. The purpose of the trim iron is to apply heat to very small places where you don't want the heat to get to adjacent areas. (Tack on lo and shrink on high!)

3. Don't ignore the advice that the sealing irons (large or trim) are for applying heat - not for stretching the film. Use a light hand!

4. The stretching around (convex) curves needs to be vigorous, and seal only a small fraction of an inch at a time. Take your time!

I know experienced builders know all this, but maybe some other beginners will benefit from these tips.