Dornier Do-29 STOL testbed

[Hondo76251]

I was just using the 3 view on the first DO 28 i did and my first fuselage ended up way too wide also, they're fatter than they look lol

 

[Scotto]

I was just using the 3 view on the first DO 28 i did and my first fuselage ended up way too wide also, they're fatter than they look lol

Ya its square but it looks wider. Rounded corners would help, but the helicopter front is just not gonna be pretty no matter what.

A thread for the Do28 would be nice.

 

[Hondo76251]

Yeah, i dont usually build a good nose on a test platform, at least not until I have it fairly dialed in.

I probably will do a thread on the 28 when i have something post worthy 😂

 

[L Edge]

Thanks! Ive read through alot of your projects, but I must have missed that one. Very interesting!
I wonder if I should set up triple rates on the throttle and maybe not on elevator? Ive got a new radiomaster that Im still learning how to program.
Im going to try to convince my thumbs that this is not a VTOL. Ill have to start with some speed and gradually get slower as I get more comfortable with it.

You hit the problem right on when you stated that the elevator/rudder has no flow/very little when the flaps/motor/prop are deflected down. Somehow you need to address that issue. Exploring VTOL and it's problems, when your flaps are partially down and if you apply differential, you change, maybe help yaw, it will induce roll because of the uneven thrust.

 

[the rc project]

You hit the problem right on when you stated that the elevator/rudder has no flow/very little when the flaps/motor/prop are deflected down. Somehow you need to address that issue. Exploring VTOL and it's problems, when your flaps are partially down and if you apply differential, you change, maybe help yaw, it will induce roll because of the uneven thrust.

This is exactly how my project turned into a CL84😂, and down the road of coding and such... then right back to good ole Stol planes

 

[Scotto]

Ready to fly! I hope. Those little nickels and dimes add up. With a 3s 1800 shes at 28.5 oz which I figured to be a WCL of 6.36. According to the chart thats not too bad, but it sure feels heavy for only having one wing. Im kinda spoiled to my biplanes.
I split the splitters for the flap and ail servos and one esc, and I just hooked the red wires together. So the becs from the escs are sharing the load. The 2205s turned out to be more weight than the 9g servos want to move, so I lessened the throw to about 50 degrees from the 90 I was planning. Theyre still not too happy sounding. We'll see what happens.

 

[Scotto]

Well it flies. Rudder is too small and I think the thrust angle in relation to the flaps might be way off. But thanks to the beans the damage is minimal. I had the motors limited to 75% didnt miss it lol.

 

[L Edge]

Well it flies. Rudder is too small and I think the thrust angle in relation to the flaps might be way off. But thanks to the beans the damage is minimal. I had the motors limited to 75% didnt miss it lol.

How did you get it launched?

 

[Scotto]

How did you get it launched?

The first flight I threw it out over the beans just in case flaps up. After the botched landing I tried taking off with flaps down about 30 degrees and thats what you see in the gif flipping over with well below half throttle. I think the thrust angle is very far the wrong way. It did take off from the ground with flaps up after but its not as funny.

I want to figure out differential thrust in opentx. But since I cant do anything simple Im wondering how to make it fade from mixing in rudder to aileron as the left slider for flaps goes down.

 

[Hondo76251]

We have quite a few planes that can transition from fixed wing to quad without too much trouble. This one seems like it would be closer to a twin rotor vtol, like an ospry...

 

[Scotto]

Finally programmed the differential thrust with pots to adjust the weight 0 to 25. It took hours to figure out but it looks so simple now. I was excited to try it but I had the wiring wrong and had to just fly without it. I changed the thrust angle to 110 degrees off the bottom of the flap from 90 and WOW that made it perfect. Very little elevator change to keep flying straight but it slows waaaay down. Im kicking myself for not taking video but I guess its fine. I made a nice landing with half flaps after about 8 minutes goofing off with loops and stuff. Against my better judgement took off again and I think the power getting low caused my right side flap servo, that is chattering and questiinable, to get soft and she went down. I ordered some 17g servos. Anyway, shes all fixed up and ready to go again.

"It's just a flesh wound"

 

[the rc project]

Finally programmed the differential thrust with pots to adjust the weight 0 to 25. It took hours to figure out but it looks so simple now. I was excited to try it but I had the wiring wrong and had to just fly without it. I changed the thrust angle to 110 degrees off the bottom of the flap from 90 and WOW that made it perfect. Very little elevator change to keep flying straight but it slows waaaay down. Im kicking myself for not taking video but I guess its fine. I made a nice landing with half flaps after about 8 minutes goofing off with loops and stuff. Against my better judgement took off again and I think the power getting low caused my right side flap servo, that is chattering and questiinable, to get soft and she went down. I ordered some 17g servos. Anyway, shes all fixed up and ready to go again. View attachment 205658 View attachment 205659
"It's just a flesh wound"

Freaking awesome! I guess I gotta build one now🤷‍♂️

 

[Scotto]

Freaking awesome! I guess I gotta build one now🤷‍♂️

Thanks! Ya its relatively simple and pretty good little flyer so far. Its very overpowered right now. I was playing with up scaling in inkscape to be better with these motors on a future one, but I like this size because it all fits on 2 sheets of dtfb. I think 1806s might be sufficiant and be fine with normal 9g servos on the flaps. As long as the max deflection is like 50-60.

So I was going to update the plans anyway. If you were building one would you want 40, 46, 50, or bigger wingspan? At 46 inches the fuse just fits on the dtfb.

 

[Scotto]

Ive been flying it pretty hard the last few nights. Landing hard too. The humidity and dew aint doing the foamboard any favors either. But the more beat up it gets, the braver I am to move the battery aft, and the better it flies. I probly wouldnt have been crashing so bad if I didnt have to fly so fast to keep the nose up.
I programmed a mix for elevator with flaps and made the weight adjustable with a pot. After extensive tests the weight is best at 0. I got very lucky with the thrust angle. Ive mixed in diff thrust for ailerons so that the weight is 0 with flaps up and R slider for weight of down flaps. I love this feature. Its very responsive at low speed and stable at high speed in roll axis. Ive got the weight of that alot higher than I expected and the flaps have only been going down 45 degrees.
The yaw I dont like so much. It feels like I have to turn really wide compared to what Im used to just so it doesnt get suirrelly and fall.
The 17g servos came in the mail and the current 9g flap servos are dead. One is stuck in the center and screams if you tell it to move. When one side is up and the other side is down there is really no saving it.

 

[Scotto]

Well I guess stick a fork in this one. I never got it dialed in just right. It was always nose heavy, thrust angle off, servo problems, or all the above and then some. I kept tip stalling it into the ground probly just from trying to fly too slow. I will try again but I want to build a few other things first.
So these motors are supposedly 745 grams thrust each making my power to weight ratio about 1.8:1. I cant decide how big to make the next one. I bought a couple ft "A" motors, but I dont know how much thrust they claim. These numbers obviously mean nothing if I dont know what Im doing.
My questions to you guys are; What should my target power:weight be? Also Wing cubic loading? If I go V tail I read somewhere on this forum 110° and 125% current H stab. Does that sound right? Im considering "thrusters" out of a tiny whoop in the V tail for low speed control (not Vtol). Still 110°? Any other wisdom/ advice from you guys is as always very much appreciated.

 

[L Edge]

For STOL ideas, found this plane which gives a lot of info on design (3 degree on wing ) and how to fly (60% of power on approach).
Interesting, props in front traps air under wing giving it plenty of positive pressure, your prop in rear doesn't trap enough air under flap I think.

I have a YC-14 transport wing with EDF's above using blown air deflected down when flaps(exploring length and deflection angle) are extending. Wow , what a difference. Going to try things like shown on video for t/o and landings. Lost a lot of aileron power for turning. Using yaw diff plus elevator to fly.

I did a bunch on blowing and suction on the wing itself to try to get laminar flow extended. I even increased hole dia size(as I went out) on a balsa covered wing using a fan(reversed polarity) in the center wing. Result was too much battery weight was needed to get an appreciated flow for any results.

 

[Scotto]

For STOL ideas, found this plane which gives a lot of info on design (3 degree on wing ) and how to fly (60% of power on approach).
Interesting, props in front traps air under wing giving it plenty of positive pressure, your prop in rear doesn't trap enough air under flap I think.

I have a YC-14 transport wing with EDF's above using blown air deflected down when flaps(exploring length and deflection angle) are extending. Wow , what a difference. Going to try things like shown on video for t/o and landings. Lost a lot of aileron power for turning. Using yaw diff plus elevator to fly.

I did a bunch on blowing and suction on the wing itself to try to get laminar flow extended. I even increased hole dia size(as I went out) on a balsa covered wing using a fan(reversed polarity) in the center wing. Result was too much battery weight was needed to get an appreciated flow for any results.

Thanks. Thats another cool plane I had never seen. I think that would probly take care of my tip stall problems. Id need to find some small really low kv or gear reduced motors...
Its kind of a shame they didnt get any contracts for that plane. Maybe it was ahead of its time.https://en.m.wikipedia.org/wiki/Bréguet_941
Did I hear that right, did he say they were flaring it with the flaps and not elevator? Im glad Ive got a slider for flaps. What kind of radio do you use @L Edge ?

 

[L Edge]

I have a DX9 which actually has enough bells and whistles for me to play with. If your into experimental airplanes, learn how to program the mixes so you can turn off/on things without flipping switches or rotating things.
Heck, even the throttle can be used as a 3 position switch(you set the ranges) which lets you trigger some function depending on your throttle position. Use it for flap deflection. Up,flaps 1/2 way, flaps full down.

If you want to really have stick time doing STOL takeoffs and landings, you should look into leading edge flaps(real cool on delta shape) or flaperons. I even automated my L E flaps to go from an angle of 32 degrees to level by itself. It also reduces your turning ability in the air..