Tiny Roll

[Don Cooper]

I have a T-tail Tiny with GWS R4P receiver, GWS Pico servos and GWS motor ( I have tried DXB with 10-8, DXA with 9-7 and S1 with 8-6 and 9-7 props). The rudder is fixed, not connected to the ailerons. It has always lost substantial altitude in rolls. The rolls are axial enough, it is just that the axis is 15 - 20 degrees or so down from the horizontal. Down elevator during the inverted parts helps some but not much. I have seen some threads on E Zone discussing the same problem, but the only possible cause mentioned was the lack of side area. So I built a foam body, making it into a mid-wing, open cockpit plane with a good bit of side area. That didn't help - it still loses a lot of altitude during rolls. Can anybody suggest any possible causes?

There appears to be plenty of power, especially with the S1 and 9-7 - good climb rate, loops, etc.

[AirWarriorBelgy]

i'm not familiar with this plane but how is the main wing configured --- undercambered - flat-- usually wing design is the reason for this.. undercambered wings change the physics of flight when inverted and cause a drop ...
remember ...pressure on the underside of a wing has to be greater than pressure on top to obtain and maintain lift!!

[Dave Robelen]

I can think of a couple of possibilities. One, the roll rate may be so rapid that your elevator inputs are not particularly effective. Next, you might have less elevator throw than is needed for the corrections. Finally, It might well be noseheavy. Do you have to hold a noticable amount of up elevator to glide level or avoid diving in the glide? You will need a CG that lets you go from full power level flight to power off without the nose dropping hardly at all. It is obviously normal for the model to sink, but it should not dive.
It has been a long time issue with pattern models that they track through a loop better with a forward CG, but roll easier and smoother with the CG further aft. I would shove the CG back a bit and try again, moving back until it feels "squirrely". Finally, you might want to ease off on the roll rate while you get this sorted out. Another test is the amount you have to move the pitch stick to hold inverted. If it takes a bunch of down to fly level inverted, it probably is noseheavy.
Regards, Dave

[Don Cooper]

AirwarriorBelgy - the wing airfoil is symmetrical.

Dave - thanks, I will try your suggestions. I have the C.G. at the back limit of the range shown on the plan, but the nose does drop substantially when going from powered flight to glide. So I will move the C.G. back a little more. Also I have been using minimum throws for both the elevator and ailerons to accommodate my aged reflexes, but I think I can handle a little more elevator throw.

I have the ailerons aligned with the centerline of the wing airfoil in the neutral position. Would offsetting neutral a little bit in one direction or the other help?

[Dave Robelen]

Hi,
Offsetting the ailerons might be used to help the looping depending on which way you move them, but more than likely would make the roll issue worse. Given that the nose drops fairly rapidly, and that you have limited elevator throw, moving the CG further aft and bumping up the elevator will probably be the most productive things to do. The task is to make up for the loss of lift each time the model passes though knife edge by timing elevator inputs accordingly. This can be more of a task on our lower powered small models because there is less momentum to carry the model through the roll.
Regards, Dave

[Don Cooper]

Dave,

Moving the C.G. back and increasing the elevator throws didn't make much difference in the altitude lost during rolls. Based on results from the FMS simulator, the problem appears to be a lack of power. I played with the .par file of one of the slow flyers on the simulation until I got it to fly, to eye-ball accuracy, about like my Tiny, in particular, it lost substantial altitude in rolls. After trying several things with no luck, I increased the power by 25% and the rolls became almost horizontal. My Tiny appears to have at least adequate power for other flight modes, but I guess those big ailerons make excellent airbrakes and generate more drag then the motor can overcome when they are deflected for a roll. Does that make sense?

[Dave Robelen]

Hi Don,
That make a lot of sense. It takes more airspeed to maintain altitude in rolls than is commonly required in many other manuevers. With the same thrust, you would probably see that it would be difficult to enlarge a loop and keep the original altitude. Sometimes the prop pitch can be the rascal here too. Too shallow a pitch cannot generate the needed airspeed.
Regards, Dave

[genebond]

Sounds about average for this size/power model to me. Typically, I pitch it up from level about 30-45 degrees, then slam the ailerons to do a roll. After a few, you can almost make it look like you're not even cheating... Of course, adding more power is another way to cheat :)

[Dave Robelen]

Hi Gene,
It may be typical for a Tiny, but my Flapjack which is a similar size, can do multiple rolls witout altitude loss. We are talking a stock Litestik drive with 8 cells and a 9-7 prop. If you are running the DC 1717 that is a whole'nother matter.
Regards, Dave

[Don Cooper]

Dave,

How long do your motors last with 8 cells? My first DXA (9-7 prop) with the Tiny didn't last very long with 7 cells. I have since added a heat sink, but have not yet gone beyond 7 cells.

[Dave Robelen]

Hi Don,
I have yet to have one play out after 40-50 flights. I spend short bursts at full throttle, and the cruise current is rather low. In comparing the two airframes, A friend and I found that the Tiny seemed to have almost twice the drag of a Flap Jack. The Tiny is derived from the very high powered "fun-fly" models with fuel engines, while the Flap Jack was laid out with drag reduction in mind for limited power. The effect of this drag reduction was to raise the maximum speed and lower the current required for flying and manuevering.
Regards, Dave

[Don Cooper]

I had come to the conclusion that the GWS IPS motors had marginal power for the Tiny as is, so I took a piece of foam I had laying around and hacked out a new wing. Not being particularly interested in inverted flight at this stage in my learning curve, I used half the Tiny airfoil with Reynolds Crystal Wrap on the bottom to form a flat bottom airfoil with half the thickness of the Tiny wing. For no specific reason I extended the span to 30 inches, keeping the chord the same as the Tiny wing. I flew it the first time this morning, and while I don't have it completely trimmed yet, I like the results so far. It is faster than with the standard wing, loops much tighter and will maintain altitude at half power or less. I hope to finish trimming it and try some rolls tomorrow.

[Dave Robelen]

Hi Don,
You did good! Using an airfoil that has a lot less drag leaves you some power to play with. If your situation is at all like mine, you will probably find that the motor runs cooler on this new setup as well. The span extension is a help in reducing the wing loading and letting you trim the bird at lower angles, which also reduced the power requirement. You may find that with the longer wing that the roll will be a bit lazy.
Regards, Dave

[genebond]

I think Don has hit on it. The drag on the Tiny is much higher than a lot of thinner wings, and therefore drops the speed considerably when flown at less than optimal angles and power levels. Most of the guys seem to graduate to a higher power drive system once they are comfortable on the Tiny with the IPS. The M100 and EPS100 seem popular. I like a 180 (Toytronix) motor grafted to the IPS, myself. With the higher speed, there are many more possibilites for aerobatics... and crashes! Don't get me wrong, with a super-light Tiny, such as the coreless driven one, it is a fun plane in a small area, such as indoors. But outside, more power seems to be the ticket.

[2NG]

Hello gang,

I've always wanted to have one of these Tiny's I found a site, and they call it Long Tiny, is this the same as Todd Long's Tiny?

http://www.*************/forums/showthread.php?threadid=54308&goto=newpost

It's a margin, cheaper than Todd's Tiny... So is this the same? For now, I'm just waiting for a confirmation from the experienced flyer's of the Tiny:)


Thanks.
G.

Edited..... Here you go.. sorry about that
http://www.homefly.com/ :(

[Don Cooper]

The airplane appears to be Todd Long's Tiny. I don't know whether the contents of the kit are the same as the one from Todd's Models. As seen from my previous posts in this thread, I powered the Tiny with several different GWS IPS motors (using 7-cell 250 mah nicads) and found the power to be marginal.