Is it really necessary to seal the hinge gap on the H9 US60? They appear to be very close already.

you really should.... adds control effectiveness, reduces your chances for flutter and gives you some wiggle room if you lose a CA hinge or two.


John

JSN is right...I seal all hinge gaps on all my planes to reduce chance for flutter!!! My friend actually hinges some 40 size planes on both sides of the surface with clear ultracote!

Hope this helps

Dan

Yeah that plane flies fast. So it really would benefit. I sealed my ailerons on my US 40. It's really easy once you try the first one. Hanger 9 manual gives good instructions.

Joe

I don't wanna offense anyone, but I've never had flutter in any of my planes and I've never sealed any of the hinge gaps. I don't find it necessary, but that's coming from my own personal experiences. Perhaps I'll seal the hinges in some airplane in the future, but I just haven't thus far.
Clint

I have had flutter in the past and caused catastrophic airframe failure. I seal all my hinge gaps with clear monokote now. No more flutter. Something else worth mentioning is that I always overpower my planes and that increases the need to seal the hinge gaps. In the past I used to nearly double the recommended engine size. Speed became a problem and likewise flutter.

I can say that it can only help to do it. With a bit of covering and your sealing iron a 40-60 size plane can be done in about 15 minutes.

Sealing the hinge gaps on this plane may not make a difference on flutter but it will add a lot to the control authority. Seal all the hinge gaps. Lots of fun to be had with this plane with quad flaps.

Ed M.

It's not a bad idea to seal hinge gaps on speed planes. Like it has been mentioned here it will aid in control but as for preventing flutter it is a misconception (unless there is a really big gap and then you probably have other problems in construction as well). Air flowing through the gap in a turn will decrease the effectivness of the control surface. The harmonic that causes flutter isn't from the gap but more likely started from slop in the control linkage that allows the surface to start oscilating.

I do not believe that sealing a hinge, on it's own, has is great (or direct) cure for flutter, although some secondary effects do apply.

What it does, is this. First, sealing the gap does reduce "loss". This does increase the effectiveness of the surface. This means that the surface needs slightly less movement to achieve the same desired control effect. In consiquence, slightly greater leverage can be given (meaning low hole in the servo horn and high hole in the surface horn) can be used. This does help increase the speed required to flutter, due to the "advantage" of the servo.

Secondly, sealing the surface can add a bit of stiffness, due to the material "crammed" into the gap, this makes movement less drastic, and helps reduce the "odds" that flutter will occour.

Airspeed causes flutter. If a pilot (or designer) claims that a plane WILL NOT FLUTTER, then that person has not experimented with enough airspeed. There is no such thing as an airplane that WILL NOT FLUTTER. There is no such thing as a "mod" that eliminates the chance of flutter, only one that changes the speed at which an airplane WILL FLUTTER. Yes, some "mods" actually lower flutter speed, meaning an increase in chance of flutter.

The only proven method of directly ruducing the chance of flutter is to reduce airspeed. The only proven method to increase the speed required for flutter is to add a mass balance. Otherwise, we only can better the stiffness of the control system. High Torque servos and short (stiff) push rods do help.

I seal all surfaces on all aerobatic planes. No discussion, and no reason to not do so. I do not, however, consider it to be a replacement for discretion for throttle stick placement.

Once again, all aircraft will flutter!

I use a one foot long thin stainless steel thing ruler to do my sealing. Just place the ruler all the way down to the CA hinge and iron the 1/4 inch of ultracoat to the outside flats of the hinges. Absolute piece of cake. I only do ailerons but the other surfaces can be done too. It's so easy that, if you are a serious flyer, why not do such a simple 15 minute task? With the big control throws of the 3D planes these days, the only way to get them to 60% is to leave a bigger gap in the hinge. If you leave too little of a gap, the control surface will bottom out on the wing long before it reaches 45%. The only other solution is to sand down (bevel) your control surfaces near the hinge. Forget that.

Joe

Joe,
Any serious 3D plane has beveled edges to begin with.

I don't care for the binding that occurs when the sealing material (tape, clear monocote, etc.) gets pinched in the hing area. I have been using shorter pieces of sealing material and placing them BETWEEN the hinges. The shorter strips are easier to handle and the movement of the surface is much more free. Air can't pass through the hinge anyway.

Ernie

i run a thin bead of silicone in the gap. next day i slice down the center with an exacto-knife.

no air gap and no binding

Instead of sanding a bevel, try to CA in a piece of tri stock for tail parts. If you are working with a taper, as on an aileron, use a razor planIt's really not that hard, and it does work well.

I agree, double bevels are the way to go, and sealing is too. I can't leave a gap, and do not settle for less than 3D throws on an aerobat.

I usually use a piece of covering material that matches, or some clear.

I like the suggestions that Ernie and outssider posted. I've never heard of the silicon thing.

I can't figure out how silicone could not bind, even after slitting it with the exact knive...?

Ernie

For most aircraft I will agree that as long as you hinge closely that you will not find too many problems if you are flying the plane for what it was designed.
I think most failures occur when there is sloppy linkage, a large gap and the plane is "over driven".
If you want to add power in a dive, seal the gap, if you want to fly at mach 1, seal the gap.
The important thing is to remember that these really are just little airplanes and they experience the same aerodynamic effects of the big ones.
Learn how to fly it like an "airplane" and also take every precaution you can to avoid losing it.

if you ever attempt this, do it on a small test piece first. the bead must me very thin and absolutely no excess can be allowed or the hinged surface wont go to full extreme throw !! if it's done right it will work....if done wrong you will have a real mess on your hands