Originally Posted by knlever

1. Anhedral decreases roll stability right? I never tried it . Does it increase lift by preventing outward floor of air?
2. Move prop rearward -what about stability and 'handing on its propeller? Not required, really but looks real stable in that position.

1. This is common misconception by both modelers AND model designers (HH "Delta Ray" for ex.)

A delta is also a Nurflügel and as such the wingtips are to the rear and act as a STABILIZING empennage, horizontal AND vertical if not flat (i.e., di/anhedral). So an anhedralled rear wingtip in such a case is the exact OPPPOSITE of an anhedralled "normal" wingtip. Note this very prominent feature in ALL gulls and albatrosses, known to have very high L/D for a bird. Having the tip of a delta or Nurlflugel elevated with dihedral greatly reduces spiral stability, why modern jet fighters usually have subfins and why the F-16 has an anhedralled stab ("stealthy" fighters keep stab inline with wing to reduce radar visibility).



Further, instead of having to add reflexed "up-elevator", by simply slightly canting the tip break-line inward toward the front ("a few degrees of "toe-in"), when bent down this automatically produces neg. AoA at the tip, EXACTLY what is best for a delta or Nurflügel (without further refining it to get the BSLD, not really important in such a crude small model with huge power/wt. ratio!)

2. Having the rotating mass BELOW the CG has the same effect as a spinning hard-boiled egg (heavy end up) or a self-righting top >


That works because when/if the mass on top of the rotor starts to get off vertical, gravity acts on it and as this UPPER mass rotates it precesses, but the force is 90° AHEAD of the "normal" precession of the rotor which is 90° ahead of the weight-produced force on the rotor .... so 90° + 90° = 180° which works against the "normal" rotor precession. However, this secondary upper precession ("wobbling", rotating upper axis) is less than the main rotor precession force and so merely diminshes that "normal" precession.

The result is a continually reduced precession seen as an inward-curling SPIRAL .... which is how such a self-righting top is observed to function (as the top slows the process reverses till the ever-more wobbling top falls over)

You can see in the startup of my UFO toy invention (I created the prototype which was then taken over with my permission: of course had I then known HOW popular it would become I would not have so easily acceded, but Spin Master came to me, NOT the assigned "inventor" to update the patent using my new text and win a large lawsuit against Overbreak, an infringer, since the supposed "inventor" did not know how/why it worked, thus giving me an "in" with Spin Master for other toys of mine):

the main mass is above the lower fast-spinning rotor (the very lightweight foam "UFO" upper section spins slowly and mostly provides counter torque drag )

My Vectron RC UFO #2 (3 min 45 sec)

Is that UFO radio controlled? We have an UFO toy that is similar always wondered how it stayed upright. The one I had was fitted with a plastic rod about 5 cm high on top. Flew OK without it though.

This is my latest prorotype. It either climbs or dives, and CG does not seem to make a difference. It is due to lack of stiffness which causes reverse elevon effects I think. Still, on some occasions it does a post stall quick turn within about a 50 cm space which is encouraging. More strengening and testing to follow. Span about 22 cm and weight is 24 g which is much more than the 16g rc model I posted earlier.

Originally Posted by knlever

Is that UFO radio controlled? We have an UFO toy that is similar always wondered how it stayed upright. The one I had was fitted with a plastic rod about 5 cm high on top. Flew OK without it though.

That is a follow-on to my original design which was first IR controlled, then RC in some versions illegally copied from Edu-Science who then licensed the N.A. rights to Canadian Spin Master. The version you describe is smaller than the original and the vertical "stick" is to allow the users to catch it whilst spinning without getting near the fast-turning rotor on the bottom! It uses an IR sensor to momentarily speed up the rotor when the toy gets too close to smtg under it. It is even more simplistically stupid (thus mass-popular) than the original insofar as it reverts to instinctive baby-action (waving one's hand) instead of learning more precise finger control for exact hovering.



Typically hyper-stupid (MUCH-copied money-making for sellers) fun for all the grown-up infants out there .... further proving how most humans (in general: gives notable often unacknowledged unrewarded exceptions) are NOT the cleverest animals on the planet > even Kiki quickly found out on his own how (by intelligent observation) to use his foot on the left stick to launch my Nano Quad

Yes the yellow one is the one I have.

I thuought I would do some calcuations for the design parameters. The first thing to establish the stall speed. Brisk wallking speed, 6.6 kmh or 1.8 metres per second is a baseline.

Assuming an all up weight of 14g, what would be the required wing area for this stall speed?

A triangular wing shape 20 cm wide by 20 cm long will have a square area of 200 sq cm or 2 square decimetres. At 14g this will give a wing loading of 2g/ sq. decimetre.

According to this calculator, the stall speed for this wing loading will be 12 km/h. This is twice the required stall speed. However, that won't matter if the minumum turn radius requirement can be met.

Can the turn radius of 2 metres be met with the required wing loading? I will use a bank angle of 45 degrees.
This calculator gives the turn radius for a given speed. An entry speed of 12 km/h or 7 mph gives a turn radius of 3.8 ft. or 1.1 m. Seems quite optimistic. An entry speed of twice that, 24 km/h will give a turn radius of 15ft or 4.5 metres. Not quite enough, but OK for an out door area. Finally, a speed of 14 km/h or 1.2 times stall speed will give a turn radius of 1.5 metres.

Not sure if these calculators were meant for low Reynolds numbers.

You might consider using the "modern technology" route I took with the RoomRaider, namely powered-lift, with the motor + LIPO providing lift (über-"blown flap")

According to this calculator, the stall speed for this wing loading will be 12 km/h. This is twice the required stall speed. However, that won't matter if the minumum turn radius requirement can be met.

But by that time you may as well just attach the model to a string and center pole and do it as a RTP model.

I'm sorry but where's the fun in having a radio control model if all we do is fly in one circle going up and down within a confining space? I just don't see it myself.

If I wanted to fly a model in such a space I'd simply opt for either an RC heli or quad copter and play at trying to pick up light weight objects and move them to new places. Or I'd build a free flight rubber powered mini stick duration model and see if I could break 3, 5 and so on miniutes of flight with it. The Mini Stick goes in circles too. But at least it'll fly more slowly and I can just sit and watch it and enjoy the beauty of flight.

I suppose if this is some sort of "test" you've given yourself then go for it. And such a model WOULD be usable in larger sites. But if the intent is to fly primarily within that small area then I just don't see it as fun other than to actually solve the puzzle. After that I'd likely hang it up.

As for the 14 gms I would suggest you find lighter components. Lots of models are flying as RC models or IR models that are lighter. And light weight is a key element in flying in tight places. With a bit of work you SHOULD be able to get it under 10 grams.

As for the bank angle why limit yourself to 45? Nothing says you can't turn at anything up to and including an 88° bank.

My Avitron ornis easily circle and do figure-8's at 11 KPH in a 3m dia, space, slower straight line. Of course they too use powered lift of a sort

PRECISE 2-ch, 8.35g, 55 mAh LIPO

Avitron flying in the living room - Avitron V2.0 dans le salon (suite) (0 min 24 sec)

2 Avitron V2.0 dans le salon - 2 Avitrons pursuit in my living room (1 min 11 sec)

From what I saw your Avitron has more on common with a helicopter than it does with a fixed wing model.

Very perceptive, Bruce! As I wrote, both the Avitron (vid is from the mfg, so shows their Avitrons, not "mine", of course) and the RoomRaider use what I consider to be "powered lift", as does a heli, eh? (absolutely no Canadian offense intended w/ "eh?", eh?)

Non taken, eh.

But by that time you may as well just attach the model to a string and center pole and do it as a RTP model.

Well that I already did with my incorrect purchase of the twin motor control J3 Cub as they call it. Apart from flying in circles, which is bad enough when in RTP mode, it also lacks elevator so no touch and goes and stalls, and no aileron or even a rudder to turn and fly across the circle for a few seconds. When the wing picks up there is no way to trim the thing or turn into the wind to compensate. There is some element of fun in it.

I'm sorry but where's the fun in having a radio control model if all we do is fly in one circle going up and down within a confining space? I just don't see it myself.

Do you mean in RTP mode or otherwise? I have posted several videos of models that do aeroatics in a confined space and its all a lot of fun. Even in a RTP model, I could imagine I could do loops and rolls - yes rolls where the string wraps around the fuselage and unwraps again. The RTP tether will only stop it from hitting the walls.

If I wanted to fly a model in such a space I'd simply opt for either an RC heli or quad copter and play at trying to pick up light weight objects and move them to new places. Or I'd build a free flight rubber powered mini stick duration model and see if I could break 3, 5 and so on miniutes of flight with it. The Mini Stick goes in circles too. But at least it'll fly more slowly and I can just sit and watch it and enjoy the beauty of flight.

I already have a quad copter or had one to be exact, and that was not good enough. It has to be a model of a jet plane, and the skill of designing and building a plane that can turn and burn in a small space is a challenge I want to meet. Technically possible, it all depends on my skills.

I suppose if this is some sort of "test" you've given yourself then go for it. And such a model WOULD be usable in larger sites. But if the intent is to fly primarily within that small area then I just don't see it as fun other than to actually solve the puzzle. After that I'd likely hang it up.

Well eventually I would fly in a larger area as well when available, it still will be a capable model no matter how little air it moves in a small space.

As for the 14 gms I would suggest you find lighter components. Lots of models are flying as RC models or IR models that are lighter. And light weight is a key element in flying in tight places. With a bit of work you SHOULD be able to get it under 10 grams.

For components I will post my selection, and recent flight tests of my #glider#

As for the bank angle why limit yourself to 45? Nothing says you can't turn at anything up to and including an 88° bank.

Too true, I missed that one, g loading does not matter as there is no pilot.

The crude object you see in the picture is my latest prototype. I curved the leading edge as a sort of conical camber, which instantly made the wing stronger. For vertical stabilizers I folded up the wing tips, which then made the wing area smaller. With a AAA battery up front, it weighed in at 24g total.

Flight tests revealed a pitch instability so after moving the CoG from 10cm from leading edge to cm from leading edge, stability was acceptable. With up elevator it was able to stall turn within a 2 metre space, and do some dramatic pull ups. I was surprised by how much lift was generated by such a small wing carrying a large weight. Experimentation is everything.

I need to build a stronger wing and forward fuselage, also, the final RC equipment and battery will not be placed at the extreme front of the model.

Things look promising.

Radio equipment suggested-

https://www.rcgroups.com/forums/show...n-indoor-micro

TX
https://www.banggood.com/WLtoys-F949...content=227736

Brick
https://www.banggood.com/WLtoys-F929...content=227736