DL-PC6: Another Delanne Tandem Wing

[synjin]

Okay, last year after the Bush Plane Challenge, folks on that thread thought about stretching the idea of a bush plane. So, I decided to mix my simple PC-6 design with a Delanne tandem wing. My Frankenstein’s monster is almost done. I modified the fuselage from my simple PC-6, and used its 59.5 inch wing in the front. The rear wing is a slight modification of the front wing but only 75% of the front’s wingspan. Of course I’m going to power it with the ubiquitous 2212, two of them, 1400KV.

This is probably the most complicated build I’ve done from scratch. It has ailerons and flaps on the front wing. It has elevons and flaps on the rear wing, and if I can program it the flaps on the rear wing will also act as elevators. It has differential thrust and about the only thing I don’t know at this point is where I’m going to have to put the battery to balance it. On my other Delanne twin the battery had to be placed almost at the CG which was mid fuselage. Until I get strapped down points for the front wings I won’t know where I’ll have to put the battery to balance it. I’m kind of hoping it’ll go away up in the nose. Otherwise I’ll have to cut an access panel to get the battery into the middle of the fuselage. It will have 4 inch wheels in the front and a 2 inch tail wheel on a caster.

A couple of vertical stabilizers and a few more details and it should be ready for a maiden flight. We’ll see whether she flies or dies.

This is the only positive thing to come out of my recovery time from COVID-19, which sucks by the way.

 

[L Edge]

You will definitely have a very twitchy pitch problem. Be sure to balance nose-tail axis to reduce chances of roll on takeoff. Been there, done it.

 

[synjin]

It looked good, and I wish I’d gotten a picture before I went out to maiden it. And it was indeed pitchy. Pitched right into the ground after an interesting and unintended wing over at an altitude of 6’. It’s flight reminded me of the first version of the DL-57, kind of porpoisey. The DL-57 Mk.I and II’s problem was that the rear wing had a negative angle of incidence. I’m not certain whether I will try to work out the problem with it, or if I should strip out the components and cut my losses. I hate giving up on an idea like this. However, when I finish recovering from COVID I still have a long honey-do list that must be completed, AND I want to build Unrau’s DH-82 Tigermoth…and a Hellcat.

P.S. On the upside I figured out how to program the rear flaps to work as elevators when not being used as flaps… Too bad I didn’t have time to try the flaps out.

P.P.S. And now I’ve spent enough time on this post, and looking back at the original build thread, that I’m trying to figure out what the problem is. The first DL twin had similar issues with flight until I put a small dihedral into both of the wings. The only problem with that is that I have wooden spars buried in both of the wings of the DL-PC6.

 

[L Edge]

Is your plane destroyed or repairable to try again?

 

[synjin]

Is your plane destroyed or repairable to try again?

Well, what a month! Shortly after I crashed the plane, I got to have my first experience with Covid. What fun that was… I’m sure.

I think I can rebuild it. As I noted above, I think both wings need to have a dihedral. But that means I need to carefully cut the spars without damaging any of the servo wires buried in the wings. I also need to rebuild the aft part of the fuselage. The place where the fuselage connects to the rear wing needs to be widened, and perhaps I should add another inch or inch and a half to the length of that fuselage section. I keep looking at the remains, but since recovering my wife has had an extensive honey-do list. I may not have built any planes in the last month, but I have constructed one heck of a deck.

Work starts up again next week, I’m a teacher, so I’m not sure when I can get back to this project. It would be nice to see this plane fly. I was pretty proud of the programming that went into the control surfaces.

 

[FoamyDM]

Anything happen since the last post @synjin ?

 

[synjin]

Well, this summer I took time to rebuild the back of the fuselage and gave it a go. She was very hard to fly, but I got her back to the ground mostly intact. I need to rebuild this model from scratch and add in dihedral for both the front and back wing. That's what solved the problems I had with the other twin-motor tandem.

Sadly, the wife has a long list of honey-dos for me to get done before I can get back to building. Hopefully by that point I will have figured out the whole ELRS TX/RX binding process...and maybe will have upgraded my FlySky NV-14 from OpenTX to EdgeTX (this bird runs most of 10 channels and the Jumper T-Lite doesn't have enough switches).

 

[LitterBug]

ELRS binding isn't bad if you use the web interface or do it as part of the firmware update.