 Hi Guys, Sealing up the hinge line on ailerons and elevators to prevent flutter is always something I've had trouble with; never seems (excuse the pun) to stay put! What is the most popular method?
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 I've used clear solarfilm to good effect. It's useful for patching too.
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Sealing the hinge to prevent flutter? I've not heard of that before. I thought flutter was likely to be caused by slack or flexibility in the control circuit or the wing structure. Yes, reducing the leakage between the upper and lower wing surfaces improves aerodynamic efficiency. Am I missing something?
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Hi Simon, I'll admit I was a bit sceptical about it too a few years ago. It usually affects larger models (2M+ wingspan) because the control surfaces are larger. The first time I noticed it was when i was at the fyting field with a friend a good while back and he pointed out that there was a pronounced buzzing sound that was apparent when I throttled back (on the bottom of a loop) coming from the airframe. It turned out it was the elevators vibrating in the airflow. We all try to make our flying controls as slop-free as we can but there is no way to eliminate the "backlash" that can be found in some of the "bargain" servos that are on the market. I must admit that I do use these on occasion as 6 JR servos at 80+ quid a pop is a bit much to smuggle past the long-haired one in the house. To prove a point I put a deflection gauge on the elevators of my current flying machine and was alarmed to find 1.5 degrees either way in what I thought was a near perfect set up!
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Doug, As Mike says clear Solarfilm or similar is the the way to go, trying to use tape to seal the surface is messy unless you can fold the surface completely back to apply it. Flutter is not just caused by poor linkages, there are many reasons even the shape of the aileron tip or if the control surface has round leading edges, the list goes on, it would require a seperate thread and I am not going there. Sealing the surface cleans up the air flow makes the control surface more efficent and just looks neat. I used to only do it on my larger models as the forces on the controls are greater, but now i do on every model as they all fly much nicer after it's done.
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 As they will be purely for sealing purposes,and not actaully hinging the surface, then as suggested....solarfilm should be fine, or you could even try blenderm tape that some of use on the smaller foamy type models - sticks very well ( try the chemist for it )
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 For smaller moderate-speed models, I use simple solarfilm hinges.but for the bigger, faster ones, I first cut short strips of (scrap) film, overlap the end, tack them together, then iron them onto the wing/control surface in an X pattern, (top on wing, underside of control, and v/v), about a foot apart, then film over the top. This gives a more positive location to the surface, seals the gap, and yet is still floppy at the hinge-line.
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 i have considered sealing surface gaps on my 5ft span Extra but am not sure how to proceed. so my 3 questions are: Do you tape both sides of the hinge ? On large movement surfaces, the tape abviously wont stretch so do you need to allow slack in the tape allow movement ? and Which surfaces need sealing, do you need to do ailerons and rudder ?  (Timbo, does blenderm work on this size model ?). regards Rich
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Well as I say...it should be OK as it is only acting as a seal. Whatever you use you need to apply it so the hinges dont bind up. I usually bend the control surface right back and up as it were, then iron on the film right into the hinge line - easier to show than describe  ...I will see if I can find an illustration. This is the best I could find showing the seal / hinge method as Eric described above /forum/smilies/surprised_smiley.gif[/img]fficial%26sa%3DN]here
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| Edited: 16/05/08 23:24 |
 I have just bought my first ever ARTF, a Fliton Extra 260 mini. All the control surfaces have square cut edges and to provide room for movement of the cyano hinges the instructions tell you to leave a 2mm gap!  This is about as alien to me as a square aerofoil! I plan to cut an angle on the control surfaces and top hinge using Solarfilm underneath to cover the newly exposed balsa and clear hinge tape on top over the multi-coloured surface.
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| Edited: 17/05/08 12:25 |
Hi Richard, Ailerons and Elevators definitely, won't hurt to do the Rudder as well. Some modellers say that only the underside of the hing line needs to be sealed but if you're going to the trouble of doing one side then why not both? As Timbo said, if you deflect the control surfaces fully and then apply the tape/film there is no need to "build-in" any slack. Just wish I could get mine to stay put! Will try the chemists tape next.
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Doug, If you look at a full-size glider, the pilot plasters tape over EVERY potential gap, in the search for a few percent less drag, and more efficiency. I imagine the Red Bull comp loonie - er - pilots do as well, for every last mph of speed. Timbo - that's it! Really old-fashioned, as used by the galloping ghost and single-channel brigade, only they used doped on fabric, or even stitched on. KISS always works best! As you said, and as I put in a different thread on the same subject, disconnect the servo link, then deflect the control surface as far as it will go before shrinking the film, ie aileron or ele, folded 180 degrees forward on top of the wing, to do the underside, then as far as it will deflect downwards to do the top surface. I saw a clever idea in another mag, on how to get a true straight line on the hinge taper, too, one of those - why didn't I think of that - jobs. Take your standard tapered te stock. glue a bit of square stock to the fat end, then glue a bit of standard triangle stock to that with the angle arranged as required for the top or bottom hinge-line, plane/sand it down, and you have a straight, stiff aileron or flap.
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Hi Eric, Going by what I've seen on TV, the Red Bull 540's have their Ailerons top-hinged with full length "piano" style hinges. I haven't seen a model 540 up close but do they have theirs top-hinged too? Takes the guesswork out of Aileron Differential as well! The Great Planes Super Sport 40 some years ago used that method you described for their Ailerons hinge taper too. Simple idea that works!
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