Grunder Industries ADF-01 Falken build log

[Mr. Gandalf]

Three things I would like to suggest you try.
1) set your control surfaces for 2 rates. One for low and the other high with a good exponential. Mine uses very little movement at all.
2) Mine was very tail heavy as you can see so I had to inch my battery forward and finally solved it by moving the canard forward.
3) Try 3/4 throttle initally to slow process of trying to get it under control.
After adjusting, plane goes real fast.

Thanks, I do have dual rates set up, but mine seems to be nose heavy and the battery is already as far back as it can go while still being ahead of the prop. I will try launching at lower throttle next time I try a hand launch, and BTW, do you think thrust angle could be part of my problem?

 

[Wildthing]

Thanks, I do have dual rates set up, but mine seems to be nose heavy and the battery is already as far back as it can go while still being ahead of the prop. I will try launching at lower throttle next time I try a hand launch, and BTW, do you think thrust angle could be part of my problem?

If you find it glides with no or very little power and then nose dives when you power up then I would change the angle of the motor. Some of your down force can also be from the large engines , the faster you go the more it pushes down. .

 

[Mr. Gandalf]

If you find it glides with no or very little power and then nose dives when you power up then I would change the angle of the motor. Some of your down force can also be from the large engines , the faster you go the more it pushes down. .

So I probably should try a slight up angle on the motor.

 

[L Edge]

Be interested in some pics showing side view, front and top views before I make any suggestions. My first thought would to try putting some elevator up trim and launch(close to ground) or start playing around with the canard. Either change the AOA or make it larger(more nose heavy)? without ripping things apart yet.

I would launch only a foot or two above ground and have thumb on throttle gimble(not the stick) so if it is noseheavy, it won't bo much damage if you shut it down immediately..

 

[Mr. Gandalf]

Be interested in some pics showing side view, front and top views before I make any suggestions. My first thought would to try putting some elevator up trim and launch(close to ground) or start playing around with the canard. Either change the AOA or make it larger(more nose heavy)? without ripping things apart yet.

I would launch only a foot or two above ground and have thumb on throttle gimble(not the stick) so if it is noseheavy, it won't bo much damage if you shut it down immediately..

Thanks for the advice, I will upload some pictures later.

 

[Namactual]

I would not even sweat the nose damage. You could cut most of the nose off and not effect flight too much. With such an exotic airframe, I would worry about getting it flight worthy before repairing too much or worrying about aesthetics.

 

[Wildthing]

A little up elevator is a good idea, treat it like a wing and give it a little reflex.

 

[Mr. Gandalf]

Sorry I took so long to post the pictures, but here they are.



So, I have attempted to fly it since my last post but it still won't fly . I gave the elevons plenty of up trim, held full up elevator, and moved the CG back but it would not lift off the ground.
Next I tried giving it a hand launch with no power and full up elevator, and it stayed level all the way to the ground; although I have noticed that this plane doesn't glide very well, it sinks way more than it goes forward but it also yaws heavily to the right . Anyway, after that I tried a hand launch with just a little bit of power and full up elevator but it dived straight for the ground. I am thinking that the engines are pushing the thrust from the motor down somehow since it only dived once I added power, so I may try blocking them so that air can't go through.

 

[Wildthing]

Move your battery back even farther and keep attempting to glide test it first with no power . Keep moving the battery back until you can glide it with little or no up trim or elevator input. Once you have achieved that then add some power but be gentle on the throttle.

 

[Wildthing]

Also for the yaw to the right and looking at the pictures you last posted, some could be camera angle though. Side shot it looks like the leading edge of the wing drops a bit so you would have a negative angle of attach forcing the plane down and from the front shot the left and right wing are at different angles. Not sure about FB but I have straightened wings using heat gun and or boiling water.

Also check your lateral balance.

 

[L Edge]

Anyway you can straighten the canards out so it is parallel to the wing? Think that is part of problem. Move the battery back about a inch per shot. Check CG each time before you chuck it.

Here is the way I want you to do it. Wait until you have a windy day where the winds are a minimum of 5-10mph. The higher the better. Leave elevator trim at zero.
With the wind blowing(now you have some lift going the wing) chuck the plane at a height of about a foot. See what happens.

If plane noses down, still move battery back 1", repeat process, until when you chuck, it flips it nose high( now CG is aft) so now you move it forward until it got the best glide. Wind still blowing, go up 2 ft and chuck it. Fine tune it. DO not use motor until you got it. That way, your experimental plane still survives. Do a video if possible. If you can't get it to glide, don't use motor.

I also another tool that we can try.

I bet no one else has something like this with nothing up front and it flies. It is very unstable if there is very little airspeed.

 

[Mr. Gandalf]

Move your battery back even farther and keep attempting to glide test it first with no power . Keep moving the battery back until you can glide it with little or no up trim or elevator input. Once you have achieved that then add some power but be gentle on the throttle.

Also for the yaw to the right and looking at the pictures you last posted, some could be camera angle though. Side shot it looks like the leading edge of the wing drops a bit so you would have a negative angle of attach forcing the plane down and from the front shot the left and right wing are at different angles. Not sure about FB but I have straightened wings using heat gun and or boiling water.

Also check your lateral balance.

Anyway you can straighten the canards out so it is parallel to the wing? Think that is part of problem. Move the battery back about a inch per shot. Check CG each time before you chuck it.

Here is the way I want you to do it. Wait until you have a windy day where the winds are a minimum of 5-10mph. The higher the better. Leave elevator trim at zero.
With the wind blowing(now you have some lift going the wing) chuck the plane at a height of about a foot. See what happens.

If plane noses down, still move battery back 1", repeat process, until when you chuck, it flips it nose high( now CG is aft) so now you move it forward until it got the best glide. Wind still blowing, go up 2 ft and chuck it. Fine tune it. DO not use motor until you got it. That way, your experimental plane still survives. Do a video if possible. If you can't get it to glide, don't use motor.

I also another tool that we can try.

I bet no one else has something like this with nothing up front and it flies. It is very unstable if there is very little airspeed.

Thanks for the suggestions!

 

[Mr. Gandalf]

I just did some glide testing on the falken, and I learned that one reason it wasn't gliding well before is because I wasn't throwing it hard enough. Another thing I learned is were the CG is, and that the elevons do provide good control authority. The problem that is probably the cause of this planes lack of flight seems to be the thrust angle.
The motor sits right above the CG, I held the plane in a balanced position by the wingtips and then gave it a bit of throttle, the result was it nosing right over. So, is the thrust angle my problem or was my thrustline test flawed?

 

[Fluburtur]

You could try changing it so when doing your test it is stable then see how it flies.

 

[Wildthing]

I think that test is flawed especially with a midmount or pusher. Try holding it vertically by the nose when powering it up and see what it wants to do.

But if you got the cg finally figured out and you can glide it with all the surfaces at neutral position I would add some up trim to the elevators and try under medium power to launch it.

 

[L Edge]

Hold your plane vertical and keep track of the throttle position to give it enough to hover. Then try to release it and see what happens. if it sorta stays up, good chance it will fly.
Then try chucking it in wind(not calm) about 1 ft off ground. Have your left hand on throttle gimbal so you can quickly cut throttle and prevent crash. Same as before. Nose down, battery back. Nose up move battery forward.
If level or small deviation, kill throttle and then your ready to go where you go to fly and then try at throttle setting you found to hover at. When launched, if got enough control, add or subtract power to fly.

 

[Mr. Gandalf]

I think that test is flawed especially with a midmount or pusher. Try holding it vertically by the nose when powering it up and see what it wants to do.

But if you got the cg finally figured out and you can glide it with all the surfaces at neutral position I would add some up trim to the elevators and try under medium power to launch it.

Hold your plane vertical and keep track of the throttle position to give it enough to hover. Then try to release it and see what happens. if it sorta stays up, good chance it will fly.
Then try chucking it in wind(not calm) about 1 ft off ground. Have your left hand on throttle gimbal so you can quickly cut throttle and prevent crash. Same as before. Nose down, battery back. Nose up move battery forward.
If level or small deviation, kill throttle and then your ready to go where you go to fly and then try at throttle setting you found to hover at. When launched, if got enough control, add or subtract power to fly.

Thanks guys! I will try it out .

 

[Mr. Gandalf]

I have got the CG worked out, and it glides well now. However, this model is pretty beat up at this point so I might have to build a new one before trying to fly it again.

 

[Wildthing]

I have got the CG worked out, and it glides well now. However, this model is pretty beat up at this point so I might have to build a new one before trying to fly it again.

Don't worry about the beat up part, now that it is gliding good and you have the cg worked out now give it some power and see if you have to change the angle of the motor. Might as well work out all the bugs on this one so when you do build the next one it will be a piece of cake.

 

[Mr. Gandalf]

Don't worry about the beat up part, now that it is gliding good and you have the cg worked out now give it some power and see if you have to change the angle of the motor. Might as well work out all the bugs on this one so when you do build the next one it will be a piece of cake.

I might try to fix it but the wing is bending near the slot so it is causing the plane to pitch down.