Flying without a vertical stabilizer

[telnar1236]

The newest version is about half-built. Not building from plans with these tailless planes is a real challenge since the geometry has to be fairly precise to work well. On the wings you can see both the elevons (to be used purely for pitch control) and the spoilers (which should control roll). Still trying to figure out exactly where I'll want to install my spoiler servos.

 

[L Edge]

The newest version is about half-built. Not building from plans with these tailless planes is a real challenge since the geometry has to be fairly precise to work well. On the wings you can see both the elevons (to be used purely for pitch control) and the spoilers (which should control roll). Still trying to figure out exactly where I'll want to install my spoiler servos.
View attachment 245258

How did you determine the size of the spoiler?
Talked to a Carf rep, suggested max angle of 25 degrees deflection and a extreme of 30 degrees for drag brakes.
My second attempt for drag brakes is going to have a set of splits.

Using landing gear to save plane like I did with DARKSTAR. Object is to advance throttle enough so it lifts off(nose up/down) and keeps flying about 3-6 inches when CG is right on. Then try a gentle left/right turns about 1 ft and see what happens.
Better than full bore, pickup and watch it crash. Worst case, my way, should give you asphalt rash.

 

[telnar1236]

How did you determine the size of the spoiler?
Talked to a Carf rep, suggested max angle of 25 degrees deflection and a extreme of 30 degrees for drag brakes.
My second attempt for drag brakes is going to have a set of splits.

Using landing gear to save plane like I did with DARKSTAR. Object is to advance throttle enough so it lifts off(nose up/down) and keeps flying about 3-6 inches when CG is right on. Then try a gentle left/right turns about 1 ft and see what happens.
Better than full bore, pickup and watch it crash. Worst case, my way, should give you asphalt rash.

Wish I had a more scientific answer, but these spoilers are a case of it looks about right

 

[L Edge]

I design a lot by the "Gut feeling", interested in your setup of spoiler servo and it's location.

 

[Piotrsko]

@L Edge If you're like me, gut feeling involved a couple hundred crashes until gut became calibrated.

Spoilers for nose down? Maybe? Hmmmmm. Gut says:"I like it" brain responds: "what do you know?"

 

[Air-headed Aviator]

This whole thread has been fun to read through, and the whole experiment really showcases how much of a geometry problem aerodynamics are.

Vertical stabs are such simple solutions to flight; they provide an opposing force left or right to resist diverting flight. Typically they get larger with respect to the wing area since wings themselves cause yawing forces when in flight and depending on their orientation.

replacing the fin as you've already shown is tricky, cause you have to figure out where else to get your sideways stabilizing forces, and minimize other areas that can cause stability. Swept wings are one of the most effective ways to get sideslip stability, because by nature of being at an angle to forward flight they essentially point some of their lift force sideways. Any slip of some degrees point more lift of whatever wing out sideways and the opposite wing more forward, causing a yawing force to point that noise back straight.

That phenomena is likely why you see more instability with dihedral on your swept wing designs than anhedral. That dihedral is pointing lift back inwards, reducing your stabilizing yawing forces. Anhedral and also the extreme washout points more lift sideways.

On the sizes you're testing those geometries will struggle to balance out, but they could run more effective with larger wingspans. I think one other already suggested such on this thread but that's basically how Prandlt flying wings work. Otherwise you will have to replace your vertical fin with drag rudders, differential thrust, and a whole matter of other tricks.

 

[L Edge]

@L Edge If you're like me, gut feeling involved a couple hundred crashes until gut became calibrated.

Spoilers for nose down? Maybe? Hmmmmm. Gut says:"I like it" brain responds: "what do you know?"

How's your gut feeling for this one?
For my second approach with the same plane(udder rudder first test), my second approach is to use a modified drag rudder where I am splitting the two, outer and inner deflection next to each other, so it involves 4 servos(individual) to form the 2 drag brakes. Why, simple to make and I have flat plate body. Don't have a 3D printer. Will try outer half deflected upwards and reverse servos and try outer half down.
Initially,l offset deflections 10 degrees takeoff and landing and switch mode to activate rudder turns.

Plane will have elevons, then deflection of inner say down, outer going up next to each other, both sides, any where from zero to 30 degrees.
Gut says 2 " wide drag rudders on first shot. Thinking it might work. Or should it be outer down?

What does your gut say?

 

[Piotrsko]

Gut says inward is nose up effect, outward is down or zero even if they are plumb to the wing. I can see up being useful, down, not so much but could be a trim effect. Yeah it's primarily for hopefulley making drag aft of the CG,

Need picture, having a dyslexia moment.

 

[telnar1236]

It's been a while since I've been able to build much between life, work and then two back to back hurricanes, but now that life has settled down a bit and the weather is not throwing storms at me, I've had some time to finish my most recent prototype. After sitting on a shelf for a couple months the foam was peeling a bit but otherwise it's in good shape. So it was the work of a couple hours to install the servos and add the skin to top of the plane. It's a bit windy this weekend, but weather permitting I plan to try and fly it tomorrow.
There are two big differences between this and previous design. The larger is that it uses spoilers to control roll instead of elevons to counter adverse yaw. While this means roll will only be controllable when it is pulling positive pitch angles, this is always the case except for in aerobatic flying, so it should be fine. The other is that the wing tips no longer have washout. This improves yaw stability (in this design) and washout was primarily necessary to try to counter the adverse yaw from the elevons.

Initial glide tests have been promising and trimming the plane by manually moving the servos seems to work very effectively. None of the previous issues with roll reversal appear to be present.

Below are some gifs of the control surfaces.

Pitch:

Roll (I bumped the elevator a bit but only the spoilers are meant to move):

 

[LitterBug]

I have a Strix Nano Goblin kit that needs to be built. Part of me wants to leave the vertical stabilizers off the initial build so I can take it out, fly it, and join this thread. It will be set up with Walksnail FPV gear so I'll have onboard footage.

LB

 

[Mr Man]

I have a Strix Nano Goblin kit that needs to be built. Part of me wants to leave the vertical stabilizers off the initial build so I can take it out, fly it, and join this thread. It will be set up with Walksnail FPV gear so I'll have onboard footage.

LB

Can if you want, but I’m not doin‘ that with my ft goblin that has a 5x7 prop on it.

 

[LitterBug]

Can if you want, but I’m not doin‘ that with my ft goblin that has a 5x7 prop on it.

Nano Goblin is Sub 250g and I fly a non-stock 2x4.1x4.1 prop....

I'd do it with the full size goblin, but the vertical stabilizer is molded to the fuselage. LOL I'm actually considering making a single vertical stabilizer for the nano goblin. Curious if it would make it a bit more stable on the yaw axis with a single FIRM fin.

 

[Mr Man]

Nano Goblin is Sub 250g and I fly a non-stock 2x4.1x4.1 prop....

Yours could work.🧐

 

[Mr Man]

Mine’s gonna be way heavier.

 

[LitterBug]

I also have two complete ReadyMadeRC Maxi-Swift 54" new/ old-stock monster flying wing kits. I could build one without the wingtip winglets......

 

[Mr Man]

🧐

 

[Piotrsko]

Sometimes somebody rips off the winglets on the combat zagi. Still flies just waddles with turn input until it gets the Idea it needs to turn.

 

[L Edge]

It's been a while since I've been able to build much between life, work and then two back to back hurricanes, but now that life has settled down a bit and the weather is not throwing storms at me, I've had some time to finish my most recent prototype. After sitting on a shelf for a couple months the foam was peeling a bit but otherwise it's in good shape. So it was the work of a couple hours to install the servos and add the skin to top of the plane. It's a bit windy this weekend, but weather permitting I plan to try and fly it tomorrow.
There are two big differences between this and previous design. The larger is that it uses spoilers to control roll instead of elevons to counter adverse yaw. While this means roll will only be controllable when it is pulling positive pitch angles, this is always the case except for in aerobatic flying, so it should be fine. The other is that the wing tips no longer have washout. This improves yaw stability (in this design) and washout was primarily necessary to try to counter the adverse yaw from the elevons.
View attachment 246326
Initial glide tests have been promising and trimming the plane by manually moving the servos seems to work very effectively. None of the previous issues with roll reversal appear to be present.

Below are some gifs of the control surfaces.

Pitch:
View attachment 246327

Roll (I bumped the elevator a bit but only the spoilers are meant to move):
View attachment 246328

Hope you try it with the EDF. Please do the video. Who knows, it may work.

I have a Strix Nano Goblin kit that needs to be built. Part of me wants to leave the vertical stabilizers off the initial build so I can take it out, fly it, and join this thread. It will be set up with Walksnail FPV gear so I'll have onboard footage.

LB

Tough to fly a wing without a vert stab. But I did find a NACA design in the 1950's that does allow(with 3 degrees of reflex) a wing to fly that is really stabilized and handles gusty winds. Rudders account for over 25% drag so this improves flight times tremendously.

 

[Piotrsko]

Whole diy point to stability is a bit of drag aft the center of pressure. Reflex on a swept back taper wing is one way, up elevon is another. Don't recall how the Prandtal does it, but it doesn't have them either.
Rudders are for boats.

 

[telnar1236]

Hope you try it with the EDF. Please do the video. Who knows, it may work.

Tough to fly a wing without a vert stab. But I did find a NACA design in the 1950's that does allow(with 3 degrees of reflex) a wing to fly that is really stabilized and handles gusty winds. Rudders account for over 25% drag so this improves flight times tremendously.

View attachment 246357

I definitely plan on getting video when I have the chance to try and fly it. The version in the pictures has a 50mm 3s EDF that gives it a thrust to weight ratio better than one, so it should have enough power, at least. Twenty mile an hour winds made yesterday less than ideal, but hopefully this coming weekend. I'm always impressed by how well some flying wings fly without vertical surfaces.

Whole diy point to stability is a bit of drag aft the center of pressure. Reflex on a swept back taper wing is one way, up elevon is another. Don't recall how the Prandtal does it, but it doesn't have them either.
Rudders are for boats.

I'll need to look into this some. All my CFD models showed something similar - at least for trimmed flight. While having washout seemed to hurt, except in terms of countering adverse yaw, reflex seemed to make everything work a bit better than simply modeling a symmetrical airfoil with a control surface deflecting up. Food for thought I guess