Danny 3.2m launch.

[soarrich]

With my Danny 3.2m which I've only had out once I noticed something odd to me. If I launch it more out than up it seems to continue the out part and doesn't rotate by itself, if I give it up it rotates and climbs like I would expect it to. If I throw it up as opposed to out, it climbs normally. The hook seems OK, maybe even a little far back because if I start pulsing the winch the plane wants to fall off. I have the balance back to where I just get a hint of up in a dive test.

Is this non self rotating a problem or just the nature of the beast. :confused:
Richard Border

[D_Ryan]

Rich;

At first read, it sounds almost like the elevator linkage or the control surface is deflecting under flight load, and not holding the desired setting.

When you launch straight out, the airflow past the elevator is rendering it more negative relative to the wing, effectively altering the decalage. Don't know if this is the result of the linkage flexing, the elevator mount deforming, or perhaps the servo not having the holding torque required.

When you launch at an upward angle, the acceleration and airspeed is likely a bit lower and the elevator setting/decalage is not altered.

Just a thought, since it would seem the force generated by the delta between the tow line attachment point relative to the center of lift of the wing would overecome and effect of the elevator anyway, but perhaps not...

I too will be interested in any responses by those more knowlegeable

r/
Dave

[ThermalBuster]

Rich

What you are seeing is probably the result of a very good setup (IMHO). You have no elevator preset to pull the nose up when you throw it straight so it goes level quite a ways before the aft tow hook location causes it to rotate.

When you launch with the nose up the aft tow hook location immediately kites the plane against the forward motion or wind. This is very good and makes the plane pull real well all the way up the line. Your zoom will build a lot of speed and ping off for a max climb at whatever attitude you set the fuselage.

I would'nt change a thing. (But be careful with the zoom. You can flutter things with a high speed ping when you are set up like that!)

ThermalBuster

[rscarawa]

Could it be that the plane is very tail heavy? I am just guessing.

It seems that the rotation would be caused by air pushing the stab down due to positive incedence. If you have a tail heavy plane, you have been adjusting the elevator to have more and more down trim in order to keep the tail from dropping or since there is less nose weight to counter act. If your stab was at or less than 0 degrees compared to the wing cord, then I would think the speed from the histart or winch would prevent rotation and cuase the plane to fly a straight path.

Try adding some nose weight if the cg range allows it, retrim for level flight, then relaunch.

If you plane keeps falling off the hook, move it forward too.

Just a hunch more than anything.

[Mark Miller]

My take on it is a bit different. Not rotating is a function of tow hook placement. I would suggest to move it back. Falling off when pulsing the winch seems to be related to airspeed and angle of attack. You may be being to gentle with the airspeed and the airfoil is actually stalled or close to it. The plane can still go up in this condition because you are working on the bottom of the airfoilbeing pressed against the air instead of the top of the airfoil lifting. It is kind of like a kite flying. I would say move the tow hook back and faster on launch. Also make sure to throw hard to get you through the stall that happens just off launch. The plans should rotate hard after you throw it but you still need airspeed to keep it flying efficiently and not mushing through the air.

Mark Miller

[R. Carver]

What Mark said. Move it back and increase the tempo of your pulse on the pedal. If the hook were too far back, the plane would have a tendancy to zig-zag up the launch and you'd be making rudder corrections like crazy.

[OVSS Boss]

I agree with Mark too. The comment was made about CG, yes, an aft CG would cause a flat launch if the hook is too far forward. I try to set my hook behind the CG and if necessary I will actually have some down trim in. But the hook is where you get rotation.

Mac

[soarrich]

I think I'll move the towhook back, and add a little nose weight for next time, I'm really enjoying this plane.

I flew it today for about an hour, it's seems to have the CG a little to far aft, i.e. it's tail is a little low while circling, seems to take a little 'top' rudder, and has a little pitch down while returning from down wind in a steady glide. This sailplane is a great flyer, the slight handling problems are very very subtle, I hope a little lead in the nose will fix them, if it doesn't fix them this would still be the best flying sailplane I've ever had, and I've been flying sailplanes since '79.

The other day when I flew it it was dead calm and overcast, perfect test flying weather, my Ram2 showed that in dead air this plane sinks at 1~1.2 foot per second. With the turnaround at 200 paces, 550~600' I was getting 450' launches and ~7 minutes.

Richard Border

[jrerickson]

Richard,

I wouldn't add any nose weight yet. Just try moving the towhook back about 1/8". On my Topaz (similar to the Danny) the towhook is behind the cg, opposite of a standard set up. Who cares, it works well. I get good rotation and I never pop off.

Another thing, I wouldn't be afraid to step on the pedal. I'd bet that the Danny can take a full pedal winch. I haven't seen a Topaz fail yet, including huge zooms off a full pedal winch, into the wind. I've seen some AVA tips come off, but that's another story :-)

John

[tomcat5109]

John, I don't want to hihack this thread so could you responed in a pm with some questions I have about the Topaz? I'd like to know your setup that has been most productive for you concerning cg placement, ballast, etc.

Thanks,

Tommy