Methods for Sealing Flaps?

What is the accepted or favorite way of sealing flaps? I've never done this but thought that monokote fed down between the flap and TE then "Z" installed (over/under) might work. but I would have to glue down one side or the other.

Is there a better way? or better material?

Thanks

I didn't think sealing hingelines was useful until I tried it. On your monocoat idea, just make the Z a little long, cut it down the middle, turn one half over, let it overlap the other half a little and heat seal them. Then the monocoat on both halves of the Z is facing the right way and you can stick it down with heat. RC guys do hinges this way. Most CL people use clear package tape. Dave Brown sells a hinge sealing tape as such. Put the tape on the bottom with the flap deflected to full up. Push the tape down into the hinge. The idea is not to get any binding from the tape.

Jim is "right on" in suggesting package sealing tape. Ted Fancher steered us to some called "Crystal Clear" (I believe) that can be purchased at WalMart or your local office supply. It is thin stuff and didn't stick well when trying to use it on packages, but for our purposes it was good. Basically you want to use the thinnest stuff you can get, and you want it to stick well enough to stay on the plane, but not so well that you can't peel it off again when it is time to replace it (if you get fuel or dirt in the hinge line.)

If you split it in half length-wise, it will be about the right width. Then apply it to the bottom hingeline of both the flaps and elevators, and put it between the hinges, only, not over the hinges. Deflect the flaps or elevators as far up as they will go and then apply the tape so it goes halfway into the gap. You want to add as little extra stiffness as possible, while allowing full deflection of the surfaces. For the most part it becomes "invisible" and won't hurt when it comes to appearance point judging.

>Jim is "right on" in suggesting
>package sealing tape. Ted
>Fancher steered us to some
>called "Crystal Clear" (I believe)
>that can be purchased at
>WalMart or your local office
>supply. It is thin
>stuff and didn't stick well
>when trying to use it
>on packages, but for our
>purposes it was good.
>Basically you want to use
>the thinnest stuff you can
>get, and you want it
>to stick well enough to
>stay on the plane, but
>not so well that you
>can't peel it off again
>when it is time to
>replace it (if you get
>fuel or dirt in the
>hinge line.)

Ted's on a trip right now, but he uses some sort of off-brand stuff that may not be available nationwide. A similar product is Scotch "Crystal Clear" extra strong tape. It sticks hard, but it never separates and leaves the adhesive behind. I use it a lot for rocket stuff.

I use Fascal, just because I have a bunch, It is a little thinner than the scotch stuff, but will leave the adhesive behind.

The technique is well described above, but I have a little sketch with instructions that I can email you if you want a more graphical explanation!

It makes a monumental difference in the way the controls respond. But the most important thing is that it eliminates a bunch of trim funnies that result from slightly different gaps, or gaps that vary over the range of travel.

Some of the guys at our club are using surgical adhesive tape—the stuff that only rips some of the hair off your arm if the medics use it to patch you up for some reason. It is very soft and despite the aparent low level of stick—on arms at least—it seems to stick to models very well. Also, it does not leave a residue but I must add that for several reasons, UV light, general appearance etc, the hinge lines are only sealed on the underside.

Also, it
>does not leave a residue
>but I must add that
>for several reasons, UV light,
>general appearance etc, the hinge
>lines are only sealed on
>the underside.
>

I think that most everyone only seals it on one side, usually the bottom (for obvious reasons).

After sealing the flap hinges of various models, I have noticed a tendency for the model to "pull" one way or the other when returning to neutral after a square turn. This is especially noticeable in the positive turns. A solution that seems to work is to also tape the elevator. This seems to balance the effect of unequal stiffness on the flaps.

>After sealing the flap hinges of
>various models, I have noticed
>a tendency for the model
>to "pull" one way or
>the other when returning to
>neutral after a square turn.
> This is especially noticeable
>in the positive turns.
>A solution that seems to
>work is to also tape
>the elevator. This seems
>to balance the effect of
>unequal stiffness on the flaps.

Oh! I'm glad you mentioned this - I recommend sealing both the elevator and flap hinge lines in pretty much all cases. Never occurred to me to do just the flaps.

However, if it does noticably stiffen the controls, there's something wrong. Most likely is that the sealing material is not crossing the gap right in line with the hinges, and is instead rolling or has accordion folds as you move it. A less likely possibility is that the material itself is too stiff, but if you use the crystal clear tape or Fas-Cal, that isn't an issue.