Lets Build a Four Wing Plane(have working prototype, tesing is going great so far !)

[Vimana89]

Here it is. For those who haven't already seen this or heard of my interest in such a project, I've begun to try my own hand at custom multi-wing designs after enjoying the DR1 so much. I could have gone with a simple bipe or even a triplane, but wanted to make a four wing plane. Fair enough, FT made a ten wing plane fly and others have done similar stuff in the annals of RC history to now, but I don't just want it to fly, I want it to fly outstanding and be unique. I have a working prototype that I'm getting dialed in with CG and trim a bit still that already flies pretty good, but got off to a rough start. Here's the video, will include more pics later. I can answer any questions about it if necessary. The design is very simple and uses flat wings with no dihedral, camber, or air foil, and employs V tail elevons.

The plane is a tiny bit squirrely, but some of that is still trim and possibly CG related. There's quite a few small things I could tweak with the design, or change the control system or air foil completely. I'm still not the most experienced designer/builder/flyer and multi wing is new territory for me, so any help or ideas are much appreciated.

 

[PsyBorg]

Proportionally I think I would add some length in the fuse between the wings and the tail. Looks like its pretty pitchy and that may be cg but I think the added length could still make it a touch more stable in the back end. Looks to have a nice roll rate.

Was hard to tell if it can flat turn with rudder only. If you can get the V tail to do that well then that opens it up for some decent 3d. Get it doing knife edges and I think it would be well on its way to being a decent flyer.

In the next flight do things like take it up high and cut throttle to give people a look at the glide slope and how it acts and reacts for tip stalling. Maybe some slow low passes directly in front of the camera at eye level so we can see how flat it flies. Then maybe some flat level punches to see if it balloons or dives on added power. Then some flat level rolls to see if it will roll on a straight axis or if it barrels.

Then everyone should be able to give enough feed back and ideas to make it a great plane.

All in all its off to a real good start going by the video.

 

[Vimana89]

Proportionally I think I would add some length in the fuse between the wings and the tail. Looks like its pretty pitchy and that may be cg but I think the added length could still make it a touch more stable in the back end. Looks to have a nice roll rate.

Was hard to tell if it can flat turn with rudder only. If you can get the V tail to do that well then that opens it up for some decent 3d. Get it doing knife edges and I think it would be well on its way to being a decent flyer.

In the next flight do things like take it up high and cut throttle to give people a look at the glide slope and how it acts and reacts for tip stalling. Maybe some slow low passes directly in front of the camera at eye level so we can see how flat it flies. Then maybe some flat level punches to see if it balloons or dives on added power. Then some flat level rolls to see if it will roll on a straight axis or if it barrels.

Then everyone should be able to give enough feed back and ideas to make it a great plane.

All in all its off to a real good start going by the video.

Great suggestions! I'll start by seeing how level I can get the passes and check the glide and stall behavior. I can't knife edge anything yet, this plane might be able eventually, but not sure. If it rolls at all it's going to barrel, I don't think the V tail elevons lend well to axial rolls. Extending the length of fuselage between the wings and tail plane is a good idea and could help with pitch but may make getting CG forward enough even more difficult, so it's something I'll have to play around with.

 

[Grifflyer]

Great suggestions! I'll start by seeing how level I can get the passes and check the glide and stall behavior. I can't knife edge anything yet, this plane might be able eventually, but not sure. If it rolls at all it's going to barrel, I don't think the V tail elevons lend well to axial rolls. Extending the length of fuselage between the wings and tail plane is a good idea and could help with pitch but may make getting CG forward enough even more difficult, so it's something I'll have to play around with.

Couldn't you just extend the nose as well? Or are you going for a stubby nose look?

 

[Vimana89]

Couldn't you just extend the nose as well? Or are you going for a stubby nose look?

Not necessarily. I like how this one came out with the stubbier look, but it would look good with a longer nose as well, so I'm open to that possibility. I just came back from more testing, I'll see how the video came out. What I can say after testing, is the plane is flying a bit better. I messed with trim a bit and seated the battery so it couldn't move around at all and cause problems with handling.

So here's the flight characteristics; Dips a bit on launch unlike my DR1, yet climbs with throttle(not to the point of ballooning straight up though). In this regard it is similar to the DR1. I'm not sure its even possible to get such a plane as either of those to not have at least a tiny bit of a nose up tendency on throttle. I can keep it pretty level at lower speeds and altitudes, but its not as easy as the DR1 because it lacks the camber and dihedrals. I think what this does is imparts what others have termed "neutral stability" that many people experience with flying wings, so its not a plane to just take your finger off the stick for long periods of time and just let it go. On the up side this makes it very maneuverable and transitioning in and out of high alpha a snap.

No axial rolls, but a pretty tight barrel roll is possible. When I cut the throttle, the plane dips/drops without a real glide ratio, but it does not till stall at all, it just drops and the wings remain level.

 

[Vimana89]

The more I fly this and dial it in, the more I'm starting to really enjoy it. This is actually a really good plane and part of what made it a bit of a challenge and lead me to think it had more design flaws than it actually does is the fact that it has been more finicky of my slop than most of my other planes. This bird is a lot more sensitive to slop, trim, CG, thrust angle, ETC. and needs a little dialing in. I stepped out of my comfort zone a bit with this design but it was well worth it.

 

[Vimana89]

Here's footage from just this morning. This has generally a lot smoother flying than my first video, and tests loops again plus rolls and stall/glide.

 

[Vimana89]

Right now the plane has a 5x4x4 prop, I wonder what it would fly like with something like a 6x4x2? Might have to try it.

 

[PsyBorg]

Seeing a more detailed flight it is more impressive then you presented it to be. Well done. I still think I would add some more down thrust to get that nose down a bit. It should if I am thinking correctly help with high alpha flight as well since it would be pulling forward more and allow lower speed to drop the tail even further.

In any case if you are happy and like how it handles leave it be and rock on. Maybe just add notes about the down thrust and lengthening the tail a bit so others can decide what they would want to do if you put them out to the general public.

 

[Vimana89]

I'll fly and trim and experiment some more with this plane as long as it holds up and possibly try an updated second prototype before releasing any plans or build guides, I'm not in too much of a rush with this one. There's many very minor changes including construction methods of certain areas that would make it more sturdy and streamlined that I would like to make. I think adding a tiny bit of length in both directions(tail and nose) wouldn't hurt. I'd definitely put in any notes related to the plans or build that it has nose up tendencies a lot like the FT DR1 that need to be worked with as far as trim and thrust angle.

 

[Zetoyoc]

looks great. that does remind me i need to get my dr1 out again. it has been four days! I love that plane I may have to try four wings soon too.

 

[Vimana89]

looks great. that does remind me i need to get my dr1 out again. it has been four days! I love that plane I may have to try four wings soon too.

Glad to hear how much you enjoy the DR1. Been a while since I took mine out, it already flies great. Still working a couple kinks out of the four wing plane, but its coming along well.

 

[Vimana89]

Going to do some more testing of different props, trim, maybe a slight change in thrust angle. This plane is still a bit pitchy and squirrelly no matter what I seem to do, but no so much where its unpleasant to fly. On the contrary, I can't seem to put this one down...a lot of fun. I want to get some more foam and sharp blades and try a second prototype soon.

Changes that will be made to the second prototype:
1: slightly lengthened/extended fuselage between wings and tail plane
2: slightly lengthened/extended and also more streamlined nose section and battery compartment
3: full stagger on the wings without that mistake of having the middle two almost level
4: possible use of tabs/slots or other methods for stronger structural reinforcements connecting the wings

 

[Vimana89]

I'll have a vid soon of testing 6x4x2, the same prop I use on my Charlie. I think I tested on the DR1 and was ok but not impressed. This plane seems to like them over the smaller multi-blade props in most cases, except maybe the Lumenier 5x4x4 which were nice but probably less efficient. High alpha is still good but takes a tiny bit more finesse, but level flight and aerobatics actually seem to improve with the 6x4x2, as well as top speed, which isn't too important on this one but still fun.

 

[Vimana89]

6x4x2 is nice on this plane. The torque is only really noticeable on launch, other than that she's as stable/unstable as ever. I don't see a noticeable sacrifice to high alpha, but my aerobatics and level flight improve with 6x4x2, unlike my DR1 which seems to prefer the 5' multi-blade style props more. I'd say this is better than 5x3.7x4 and at least as good as 5x4x4 and a lot more efficient.