Venting Control Surface Covering?
 

Ihave several planes that have "holes" in the control surfaces, one is a SIGSomethin' Extra with laser cut holes and the other is a Hog Bipe with self inflicted "circle cut saw"holes. Both are afflicted with noticeable sagging covering over the holes. Both are kits built by me. Both have their hinge gaps sealed on both sides. Both are covered with Ultracote. I have used a heat gun and hot iron trying to eliminate the unsightly sag (the plane!not me). With each tool the covering billows up as there is nowhere of the expanding air to escape. Oh, during the original build of each, 1/16" holes were drilled in the LE of control surfaces into these cavities - worked for the inital covering but not for shrinking after the hinge gaps were sealed.

My question: How do you address providing venting for these areas?

TIAfor sharing your experiences.

RE: Venting Control Surface Covering?
 

Drill a hole like the one in the LE (Which is now apparently plugged up) in either the side, or the TE.

RE: Venting Control Surface Covering?
 

if you can't do as Mike said then a small pin hole or two in the covering will allow the gas to escape just like when you have a bubble in the covering.

RE: Venting Control Surface Covering?
 

Both good tips. The SSE has plenty of wood on the TE of the control surfaces. 1/16" bit in a pin vise ready to drill. The HB elevators and rudder are tapered to 1/16" so looks like the pin hole will do the deed.

Thx.

Oh yea - GB- Ihave NEVERhad a bubble in MYcovering so Ihave no clue what you're talkin' about! http://www.rcuniverse.com/forum/js/f...wink_smile.gif

RE: Venting Control Surface Covering?
 

Do not put a pin hole in free span covering.  If you do, the hole will expand  when you heat it to remove the sag.

RE: Venting Control Surface Covering?
 

Got a fan?

Got an iron?

I got a box fan in the shop. I turn it on and do the shrinking in front of it. The shoe on the iron can be applied so it only touches a small area of the covering. Shrink a small area at a time.

When you cover a hole in an open area, you need the patch to stick far enough away from the hole that you can apply heat that doesn't soften the outsides of the patch while you shrink the patch that's over the open hole.

Apply any patch with the low temperature recommended by the covering mfg. Let it cool completely. The idea is to get good supporting area around the hole. When it's completely cool, turn up the iron and touch only patch area in the hole area.

When the air inside the "drum" heats up and expands, the fan blowing on the other side will cool will carry off most of the heat.

I have had to punch a hole in one bay that was a real problem. I did it in a corner where the covering was supported by a rib going one way and the LE going another. I didn't get heat close to it and when everything was worked out and cool, a very small patch went over it on low heat without any trouble at all.

It's a technique you learn over time.

RE: Venting Control Surface Covering?
 

This is Ultra, not Mono. The little pin hole will often close up under heat as it cools.

RE: Venting Control Surface Covering?
 

Hi!
All holes should be made through the wood into the inner part of the wing/stab or whatever ...not made directly in the open film structure!!!!

RE: Venting Control Surface Covering?
 

VACUME PUMP. I'm not going to give a blow by blow "how to" description. Most modelers don't
have a vacume pump anyway! When covering the control surfaces I drill 3/32" holes in the
center of each hinge slot. Typically hinges ar 3" to 4" apart which works well. If the design
uses aileron torque rods, the control rod hole is also used to suck out heated air. Cover the
control surfaces as you usually would. Start the shrinking process in the middle, and work toward the tips. Insert the tubing from the vacume pump into the a hinge slot. Start with a heat gun, and
as blisters form, turn on the vacume pump. Finish it off with an iron. The trick is to learn when to
apply vacume, when to use the heat gun, and when to use the iron. You also need to listen to the
sound of your vacume pump to know when it is laboring (choked off) and when it is helping you.
I've got airplanes that I did several years ago, and have never been reshrunk. Monokote is the
only film I've done it with, but I see no reason it shouldn't work with other products.
I never really liked plastic film anyway. I still paint half of what I build. Greg

RE: Venting Control Surface Covering?
 

jaka - Sounds like we're on the same page as I use a 1/16" drill bit in a pin vise during construction to connect the various areas not directly exposed to the outside atmosphere.

Greg - I know that my building skills really suck but I don't think that's what ya had in mind. Definitely food for thought on the next project.

The whole story is: During the initial build I vent every compartment exposed to covering to atmosphere. The wings - not an issue. The ailerons - vents to the LE as are the rudder and elevators. The fin and stab are vented to the TE. Kool. The base covering and trim are applied. Still, everything is vented. Then I seal both sides of each hinge. Boom! Didn't think about it because all of the vents have been sealed. The aileron guts are no longer vented. The elevators and rudder are no longer vented. The stab and fin are no longer vented. After a bunch of trips to the field on hot days things need tightening up. Either an iron or heat gun is used. But, there are a bunch of areas that are no longer vented to the atmosphere. Thus my question.

RE: Venting Control Surface Covering?
 

I've started embedding tiny styrene vent tubes on new construction. The LHS probably has a wide selection of styrene plastic tubing other hobbys use.

RE: Venting Control Surface Covering?
 

I just use a straight pin to make a "pinhole" in the wood of the leading, or trailing edge of each bay.

RE: Venting Control Surface Covering?
 

First of all, you want to seal the working moving surface, Ail, rudder, elv, is that correct? Seal only one side, usually the bottom of the surface.
Remove the botched up sealing material, and start over.
When cleaned with Trim Cote that you can buy from any hobby store, Have your pieces all laied out, then remove the backing and place the covering on the cleaned area.
Then use your finger, remove any problem area's and then use a small screwdriver to poke it in where it needs to go. After it sets , about 1 min. use a heated Trim iron and go over the coating. It works. You don't want any Pin holes anywhere. That invites a rip in the covering and more problem later.

RE: Venting Control Surface Covering?
 

Hey Flaphappy - the 2-sided sealing of the hinges was done because I am anal retentive about my covering jobs. Just like to keep that good ole glow goo from infiltrating the back side of one-sided hinge seals making it difficult or impossible to keep clean. If both sides are sealed - no clean up issues.

RE: Venting Control Surface Covering?
 

I use the vacume pump when I cover solid sheet surfaces. On built up surfaces I drill small holes to connect all possible "chambers". These are then vented to the hinge slots. Greg

RE: Venting Control Surface Covering?
 

hi
put a pin hole in every open bay of a shrink filmcan do this on the bottom-but will not be seen anywayallows hot expanding air to escape
is especially good to stop the covering from sagging in the sun at the field-does not effect the way the plane flies will not cause the covering to rip
it works good
REGARDS TONY