Flat vertical stab/rudder question.

[Paul5992]

Were are all you smart mouth's now? I post pics and I still don't know any thing?

[yakpilot]

***? you're making a big deal out of a non-issue IMHO.

[sideshowbill13]

Heres mine!!! I just used a lot of glue on the rudder

[2walla]

Shoot that thing looks pretty good-- especially for the price..

[sideshowbill13]

Mines not finished yet i am just waiting to be able to fund the electronics and 52cc turnigy engine.

I plan on using it on imac once its ready!!!

Also been thinking about having the cowl airbrushed with flames to make it even more like the redbull 540 I like scale things.

[wingwall]

O.K., here goes. You should be fine, and it is good that the horizontal stab and elevator is an airfoil. It gives it some depth that contributes to stiffness. You need stiffness and little or no slop in your servo and linkage. Just don't do any full power dives. Thottle management is needed.

Many, if not most, airplanes, including ones with airfoils, can get flutter, it they go fast enough. It is vortex shedding that oscillates from one side of the elevator to the other at the rear that causes the flutter. If the sta/fin is not stiff enough (and strong enough) the oscilation of the vortex shedding can reach a resonant frequency that accelerates the deflection and force back and forth on the stab/fin. You either lose control or something breaks. It's the horizontal stab that usually needs to be stabilized and made stonger, particularly if it is flat and too thin. The fin is short and usually stiff enough with the fuselage to give it the strength and stiffness needed. As long as you keep the pull-pull wires reasonably tight it should be fine. (It appear from the pictures that you are using a pull-pull system.

I have seen ailerons of airfoiled wings flutter and come off, just because the linkage was not stiff enough. Flutter set in very noticebly on a Midwest Extra 300 ( 80" with a Moki 210) I had (still have) some years ago just on a very shallow dive at about half throttle. I tried to slow it down and get back to the field, but the aileron pulled out the hinges, yanked the single servo linkage apart, and the aileron fluttered to the ground. I was able to land with only one aileron. You usually cannot do that if you lose the elevators. With elevators in flutter you lose pitch control and crash. If you lose your rudder you can revert back to how most of us learned how to fly, that is with bank and yank flying.

The aileron was fine, so I glued it back in. The linkage and servo was another story. Gears got stripped in the servo. Since then I have gone to stronger servos and linkage. I don't know if the gears got stripped during the flutter or as the aileron came off putting a final pull on it.

The Midwest had truss wiring to stabilize the flat stab (older model), although that was not because it said so in the plans (kit built). I read about it as a good thing to do in threads such as this. Later models of the same kit had an airfoiled stab/elevator. The plane still had a flat fin. The rudder was not real strong on knife edge. That's where an airfoil would help also.

Have fun with it. And give us some feedback on how effective the rudder is.

W

[Mithrandir]

	Quote: Originally Posted by MODE 1
	........ Minor flex is a good thing as it displaces load.

I don't understand....

?????

[MODE 1]

	Quote: Originally Posted by Mithrandir
	I don't understand.... ?????

LOL Mith.

[wingwall]

Oh, and don't forget to seal the hinge gap.

[sideshowbill13]

how do you seal the hinge gaps

[wingwall]

Some ARF manufacturers provide extra covering in the same color as that that is at the hinge line. You usually have to cut it into strips wide enough to crease it down the middle and fit into the bevel of the hinge line. Iron it to both sides of the bevel. You only need to apply it to the top side or the bottom side. Top or bottom is at your preference. The top side may look better, since it hides the hinges. It depends on how neat and accurate your are at applying it. Sometimes this will not hold well either, and come loose with time. Often there is a place where it does not fit well with the gap and hinges, and the crease is not straight, then somewhere in its range of motion it gives an irritating popping or crackling noise. There needs to be a straight line in the crease.

Many people get a clear tape that sometimes is sold as a hinge tape. Probably the most flexible (no crackle) and easiest to apply is 3M Blenderm. This I understand is what is repackage and sold in hobby shops as hinge tape. Another possible tape to use is Scotch MultiTask. It, or the Blenderm may, or may not, be found in your local Ace Hardware or an Office Depot. The Blenderm can also be found in a medical supply store, as it is used to apply things to skin.

[Bam Bam]

i have only ever used good old regular clear tape that i flog from work! works great! any tape will do so long as it sticks.

[rede2fly]

go to your local banner and sign company get thier scraps of vinal works great and can get whatever color you want. most of the time they will just give it to ya

[sideshowbill13]

Ok I have some hinge tape I built a lot of foamies with it when I scratchbuild its flexable and I like using it.

thanks!!