spinning out of control

[TJFBryant]

I am recently doing a scratch build of a very simple very novice micro glider. They call it a tailess glider because Basically its a Wing with a main fuselage. Like a delta wing. Now it has a moderate sized vertical stabilizer and thats about it. I am attempting to take this glider which flies very well when free flying and convert it into a micro rc plane. I have made the vertical stabilizer and evelons (passes as a horizontal stabilizer) to be fully functional. I am using a RFFS-100 system. When I fly the glider (6 " glider) with the Kp-00 motor and U-80 prop. it seems to roll uncontrolably. Could this be because the vertical stabilizer is not large enough for the amount of thrust being used? Or could it be the lack of a real horizontal stabilizer?
Like I said, it flyes fine when no motor is attached. It seems the motor is creating a whirl wind of trust that over comes the flying dynamics of this plane. Any thoughts?

I need major help on this, I am stuck between a rock and a hard place....plus I am new to the field aerodynamics and flight physics. I have general knowledge, but thats it. Thank you.

[Mike Taylor]

Got a picture of your set up? That would help in figuring out your problem. A couple of thoughts, though...

6" WS is pretty small, even for a delta. You might need to scale it up a little. If it a true delta, then you only have ~14 to 18 square inches of area, or about 1/8 square foot. Most of the smaller and faster RFFS planes I fly need twice that area (32 to 50 square inches).

Is the motor in the front or back? If it is in the back (pusher configuration), then there isn't a lot of air flowing across the controls until it gets up to speed. The KP-00 isn't exactly a torque-monster, but it does have enough to twist up a really small plane. Try launching it a low throttle, and then bring in more as the plane accelerates.

ALong another line of thought - how do you have the controls set up, and with what type of actuators? Are you using two BSD or Mini-MagActs, or are you using the surface mounted coils? How heavy are the surfaces, and how are they hinged?

If you are using the remote mounted coils, are they inline with each other to provide centering force? If not. try lining them up (with the output arms at 90* angles to each other). The actuators do not generate any real force at neutral, and the surfaces are on their own until you power to them be bending the sticks on the TX.

I either line the actuators up in line, or often use small 1/8" x 1/16" magnets to generate this centering force if the actuators are not lined up. This prevents a lot of problems like flutter around neutral.

[TJFBryant]

Thank you Mike for Replying. Your help is very much appreciated.
I think I can give you more specifics, sorry no picture though.

My tailess glider or delta wing has a wing span of approx 8 " and a body length of 6.5 ". The vertical stabilizer is roughly a total of 1.75 " top to bottom, BUT its only 1 " above the main wing and .75 below the main wing. The plane's motor is mounted in the front.
I am using the surface mounted magact coils directly to the control surfaces. They are aligned correctly, and the control surface are in line. I attached the control surfaces using slivers of rubber as hinges. It works rather well I think.

I believe a few things need to happen to make this plane fly straight with a motor attached. Remember it flies fine with no motor attached. Anyway. First I think I should make the main wing surface area larger. When I throw the plane at low throttle, the weight of the motor is so great it just lawn darts. If I throttle up to 50% in rolls slowly, yet uncontrolably. And just so you know, When I full throttle and hold it completely vertical it shoots straight up like a rocket spinning as it ascends. Personally, its one heck of a crazy flier. The fastest most uncontrolable plane I have ever seen.
Secondly I think I should enlarge the vertical stabilizer across the parallel of the entire Main wing from the front of the glider to the back. The vertical stabilizer now seems small and insignificant to the stability of the plane. :)

[Mike Taylor]

If it 'lawn darts' at no throttle with the motor on it, there it sounds like you have CG or surface reflex problems. It should glide faster than without the motor, but it should still glide. Check the CG as a glider, and make sure the CG is somewhere near or slightly ahead of that point. On a really small light model, you may need to get creative on where you mount the bits and pieces.

It may also be that the surfaces had some reflex as a glider to hold the nose up, but the actuators are holding the reflex out. This is a good place for centering magnets. Like I said, there is no force at neutral, and the weight of the surfaces is holding then down instead of up. Here is a picture of what I mean.

The gold piece under the chicken's neck is a 1/8" x 1/16" rare earth magnet. It centers the control surface, and it also keeps the actuator from letting the surface flap wildly. Adding these to the plane in the photo took it from being almost uncontrolable to being a fun flier... I got these from Forcefield.com and they are item #48. See: http://www.wondermagnets.com/cgi-bin/edatcat/WMSstore.pl?user_action=detail&catalogno=0048
This plane also had the rubber band hinges, but with the magnets in place, two 1/8" strips of tape were okay to use, and they are also a lot more durable and easier to replace.

One last thought: those surface mounted actuators don't produce a lot of force (the remote mounted ones are much stronger), so use the lightest materials you have for the surfaces. 1/32" balsa, or even some egg-carton foam might be light enough to help...

[TJFBryant]

thank you very much for your input. I am going to definietly buy those magnets ... I was always wondering why my control surfaces were fluttering like it was spastic.

I fixed the CG and now it doesn't quite nose dive any more. so thats a good thing. I think I will have to get a little creative when it comes to canceling out the constant uncontrolable rolling.

This glider I turned into rc wing comes from plans in a 1938 Airplane Modeler news magazine. The plans are more like diagrams of what it looks like then actual plans with measurments and instruction of any kind. So I improvised. Now all I need to do is modify it appropriately, and if my prayers are answered...it will do what it was meant to do....fly. I find that building it from scratch was extremely easy (3 hours to build without detail), and perhaps, if it flies and flies well, I will share pics of it flying with you fine folks. Thanks again Mike for the quick replies

I apologize also if my questions were less then intelligent, like I said...I am a novice- Intermediate flier...I know about only general aviational physics and building. :-)