Dornier Do-29 STOL testbed

[Scotto]

I stumbled on this plane and it just struck me as an interesting configuration. I've got plenty of projects started that I still want to do, but I just can't resist this thing. I'm going to try to keep it pretty simple because I imagine it getting cut up, crashed and repaired, or otherwise redone in different ways.

Starting out with 40" wingspan and 2 2205s. Skipping the slats this time, but hope to figure out some nice ones. The goal is not VTOL. I think its more to have about the same "TOL" distance as a similarly sized more conventional stol plane, but with a higher payload capacity. However I probly will try to make it a kind of tricopter or asymmetric quad eventually

 

[Bo123]

Ooh nice. Interesting concept

 

[Hondo76251]

Dornier is right up there with dehavilland as some of my favorite airplanes...

This one is pretty wild, would love to see that thing in action!

 

[Scotto]

The night before last I got most of the pieces cut out, and last night I got most of it glued together. That went pretty quick! I should try to keep it simple more often!

Ill put my cut plan on here just because I know I like to look at other peoples plans, but its kinda rough and there was a handful of problems I found. Probly more I didnt find lol. I dont really like how I did the big flaps, but its removable so Ill figure out a more complicated and smoother version later.

 

[Bo123]

How did you cut so well?

 

[Scotto]

Thanks! I glue the plans to the fb instead of taping them, and then I cut on the lines with a sharp knife. I err to the outside on curves and stuff so I can touch up with the sanding block. For the spars and the borders for folds I use this balsa stripper tool. Love that little baby! Buy one if you dont have one. Or get 2 just for fun!

 

[the rc project]

I have stumbled upon the do-29 before, I did some experimenting with my timber x to see if I could lower takeoff and landing distance. It was able to fly directly off the flap motors(main motor shut completely off) however landing was a challenge, I ended up nosing it in. The motors created a large down pitch when throttle would increase in the slightest. I did build a small fuse for a do-29 but never finished it. This is an awesome build!

 

[Hondo76251]

I have stumbled upon the do-29 before, I did some experimenting with my timber x to see if I could lower takeoff and landing distance. It was able to fly directly off the flap motors(main motor shut completely off) however landing was a challenge, I ended up nosing it in. The motors created a large down pitch when throttle would increase in the slightest. I did build a small fuse for a do-29 but never finished it. This is an awesome build!

Thats pretty clever!

It does look like the DO 29 would have some unique flight characteristics to say the least! Lol

 

[Scotto]

I have stumbled upon the do-29 before, I did some experimenting with my timber x to see if I could lower takeoff and landing distance. It was able to fly directly off the flap motors(main motor shut completely off) however landing was a challenge, I ended up nosing it in. The motors created a large down pitch when throttle would increase in the slightest. I did build a small fuse for a do-29 but never finished it. This is an awesome build!

Cool! Thanks. I saw your thread with that after searching to see if it had been done here. You didnt elaborate much as I recall and moved on to the other project so I kinda assumed it didnt go well.

I thought it looked like it would do that pitching down thing. Because of the thrust being aft of the CG and the gyro effect. Looking at the few pictures of it flying on the internet, when its landing it looks VERY flared. Like the test pilots were bracing for it or something. I was going to try it mostly scale first. But I was thinking on the next one Id try making the H stab bigger and with an airfoil. Not upside down like some stol planes, but rightside up to move the center of lift with flaps up far enough back that when the flaps are down 90 degrees its almost balanced on the thrust line. And if thats too much I can just cut the tail span down a little. This is all assuming I dont make it go splat first flight . I imagine you have to lower the flaps very slowly.

 

[L Edge]

I have stumbled upon the do-29 before, I did some experimenting with my timber x to see if I could lower takeoff and landing distance. It was able to fly directly off the flap motors(main motor shut completely off) however landing was a challenge, I ended up nosing it in. The motors created a large down pitch when throttle would increase in the slightest. I did build a small fuse for a do-29 but never finished it. This is an awesome build!

Did you program any up elevator to counteract the flap motors as they move down?

 

[Ryan O.]

If you ever do add slats, the ones off the FT Storch might work on a plane this size.

 

[the rc project]

Did you program any up elevator to counteract the flap motors as they move down?

Yes, I did. But moving so slow and the “main” propellor not providing airflow to the tail made the plane lose authority, annnnd splat

Cool! Thanks. I saw your thread with that after searching to see if it had been done here. You didnt elaborate much as I recall and moved on to the other project so I kinda assumed it didnt go well.

I thought it looked like it would do that pitching down thing. Because of the thrust being aft of the CG and the gyro effect. Looking at the few pictures of it flying on the internet, when its landing it looks VERY flared. Like the test pilots were bracing for it or something. I was going to try it mostly scale first. But I was thinking on the next one Id try making the H stab bigger and with an airfoil. Not upside down like some stol planes, but rightside up to move the center of lift with flaps up far enough back that when the flaps are down 90 degrees its almost balanced on the thrust line. And if thats too much I can just cut the tail span down a little. This is all assuming I dont make it go splat first flight . I imagine you have to lower the flaps very slowly.

Sounds like we could talk for hours about this! I did try to offset the motors to have the motors push into the cg. And yes lower the flaps very slow 😂. You are correct with me moving to other projects but I think I’m coming full circle 😁

 

[L Edge]

You really picked a tough project.

With the flap (slight to moderate) you now have thrust components. Lift and forward speed now call for accurate throttle management. Takeoff usually you can get and isn't bad compared to landing, where less power causes it to drop but you need to match a forward air speed that keeps it in the air as you descend.. Your choices are thrust or flap(change angles changes lift and forward speed). Now I didn't even discuss pitch problems (whole new set of problems.

I explored the CL-84 concept and let me show you what I mentioned above. Thrust is in front of wing rather in back on flap. Same concept. How can you get it to CG? This is at one fixed angle. Need a fc to work it all out.

Second attempt at getting it to fly. Solved my pitch problem. Used wind to help me so I could change height and land properly..

It STOLed (real good in the last flight of the video)

 

[Ratcheeroo]

Thanks! I glue the plans to the fb instead of taping them, and then I cut on the lines with a sharp knife. I err to the outside on curves and stuff so I can touch up with the sanding block. For the spars and the borders for folds I use this balsa stripper tool. Love that little baby! Buy one if you dont have one. Or get 2 just for fun!

And I bet your blade is always sharp!. This is one area where I think some people overlook when cutting foamboard, it and the paper dull blades very quickly. I am continually snapping a new blade when cutting plans. I would say I probably go through two full blades during an average build. Great job!

 

[Scotto]

If you ever do add slats, the ones off the FT Storch might work on a plane this size.

Hey ya, simple and removable. The balsa stripper will be perfect for that too. Thanks.

 

[Scotto]

Yes, I did. But moving so slow and the “main” propellor not providing airflow to the tail made the plane lose authority, annnnd splat

Sounds like we could talk for hours about this! I did try to offset the motors to have the motors push into the cg. And yes lower the flaps very slow 😂. You are correct with me moving to other projects but I think I’m coming full circle 😁

What would you start with, like 5% in the mix?

Oh, the offset of the motors didnt even occur to me. It would be a trade off with how much air its pulling over the top. Ya we probly could find lots to talk about. You guys have given me enough to think on for tonight I might need some Tylenol.

 

[the rc project]

What would you start with, like 5% in the mix?

(Talking about the elevator mix right?)of course depends on your servo set up but I tried 0% for the first stage of flap(because from stock it’s -8% on the timber) and 10% for full flap(witch wasn’t actually full flap extension, that timber x has humongous flaps, even without a motors on the flaps she pitches down under power)

 

[Scotto]

You really picked a tough project.

With the flap (slight to moderate) you now have thrust components. Lift and forward speed now call for accurate throttle management. Takeoff usually you can get and isn't bad compared to landing, where less power causes it to drop but you need to match a forward air speed that keeps it in the air as you descend.. Your choices are thrust or flap(change angles changes lift and forward speed). Now I didn't even discuss pitch problems (whole new set of problems.

I explored the CL-84 concept and let me show you what I mentioned above. Thrust is in front of wing rather in back on flap. Same concept. How can you get it to CG? This is at one fixed angle. Need a fc to work it all out.

Second attempt at getting it to fly. Solved my pitch problem. Used wind to help me so I could change height and land properly..

It STOLed (real good in the last flight of the video)

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.

 

[Scotto]

And I bet your blade is always sharp!. This is one area where I think some people overlook when cutting foamboard, it and the paper dull blades very quickly. I am continually snapping a new blade when cutting plans. I would say I probably go through two full blades during an average build. Great job!

Actually I have a bad habit of pushing too hard so I break off and dull the tip on the mat real bad. Im running low on supply so Ive been trying to be gentler. Thanks

(Talking about the elevator mix right?)of course depends on your servo set up but I tried 0% for the first stage of flap(because from stock it’s -8% on the timber) and 10% for full flap(witch wasn’t actually full flap extension, that timber x has humongous flaps, even without a motors on the flaps she pitches down under power)

Ok so youve got it on a switch. The only flaps Ive set up were on a slider, and thats what I was planning on doing again. Im still very green on the opentx so Ill have to study up on that. Those numbers help though. I just had one number and had settled on 6.

 

[Scotto]

Here is the hatch in progress. When I can I like to spray glue the paper back on on the inside of curves for the strength. This one was easy. I traced the curve onto some scrap and temporarily glued it on the outside to hold it while I glued the paper on. I just got a new soldering iron "rework" station that has a hot air gun or electric torch, not sure what to call it, but it is awesome for undoing hot glue. I put a straw inside the holes for a guide for the little skewer "keeper". Might need to put it on a rope.

The body is wider than I expected I guess, but at least my hand fits in it that way. I cheated on the wheels and used my Circle slicer. Tail servos are ugly but they work. Had to order bullet connectors for the motors and the splitter and some other stuff. The motor parts and flap servos are the only thing now other than slats and maybe lights.