Hello folks

Thought you might like a look at my own design 'Whirling Dervish'

The idea was to build something easy to fly and stupidly simple to build. I have tried it in various arrangements with different types of hubs.

The V-Tail did work ok but gave lateral stability problems in strong winds. This was replaced with the conventional fin and tailplane which works fine in all conditions.

I tried a 3 blade conventional straight hinged hub and a delta hub with 15 degrees of delta. Both seemed just as good but the delta hub gave a faster spin up which made ground launches a lot easier in low wind conditions. I did try a two blade hub but initial spin up was more difficult and the lift was definitely not as good as the three blader. I will try the two blade hub again after a few alterations as it is easier to build than the three.

Power is from a TT GP.10 with an 8x4 prop. Flies around nice on half power and a 2 oz tank lasts for ages.

I hope to make a plan for it after I have tried out a few more alterations . Right now it uses DC roll and has an elevator for pitch, it also has a rudder. I might try it fully DC just to see how it goes. Also I am going to try and build some of Hal De Bolts quick and dirty blades for it as that would make rotor construction easier for the beginner.

I know it is simple and unexiting to look at but the idea is to try and get a those starch wing enthusiasts to have a go at gyro flying.

Anyway, hope you like the pictures

Sean

Hi Sean, it looks great! I like your simple, straight forward design. What is the rotor dia. and the final weight? What did you make your fuselage from? (Looks to be a profile?)

Sounds like we both went down similar paths. My 'gyro had D.C. fore/aft control of the rotor plus elevator control (on separate channels) as well but I didn't like the response I got from changing the rotor angle. I ended up just adjusting the rotor tiltback to the best compromise setting and removed the servo & linkage and installed a ground adjustable link to save some weight. The conventional elevator, D.C. rotor tilt plus rudder really works a treat!

Hi Dickeybird

Thanks for your generous comments.

Rotor diameter is 32" and the all up weight is 22 oz. This gives a disc loading of just under 4.
Profile fuselage uses 5mm balsa sandwiched between thin plywood. Engine and fuselage mounts are 5mm sq hardwood set into balsa prior to glueing on the hardwood sides. The rear fuselage is open construction with 5mm sq spruce top and bottom with balsa strip infill. Pylon is similar.

I have flown all DC on some of my other designs but by fixing the rake it makes setting up easy for the beginner. Also the hang angle is easy to find as you just hold the mast and check the rear of the mast hangs vertical.

Elevator pitch does work very well as you say, to be honest I could do with making the elevator a little larger as at low power settings the pitch response is slightly limited though not a serious problem.

Attached is a better image showing the fuselage construction and an image of the delta hub. You will notice the hub is a virtual carbon copy of Jim Baxters design. Its simple and it works really well so why change it ?

Sean

Ahhh, simple & light construction! I usually seem to do OK in the lightweight aspect, but the simple part....nope! Too many sticks and little tiny parts.

I was worried about low speed elevator response during the design phase of my 'gyro so I used a thick, airfoiled stab to give more lift when needed than a slab surface. I used an Eppler E168 airfoil (12.44% symmetrical) and it works GREAT! Here's a pic:

'Nother pic:

Heavens !

Thats a really lightweight construction. Is it the .049 powered model I saw a thread on previously ?

I would have thought that at low airspeeds it wouldnt make any difference whether it was slab or elegant airfoil. Obviously I am wrong to assume this. Maybe the correct shaped section like your design increases the efficiency by maintaining a smooth flow for high angles of attack.

I will try a larger elevator first as it might be the simplest way, failing that I will produce a sectioned stab like yours.

Sean

Thanks Sean! Yup, it's called the "Gyrator", Cox TD .049 powered. Go to Andrew Donatelli's website for the RCU 1/2A Design Contest and click on "Gyrator, by Milton Dickey" Scroll across and click on "Gyrator3.mpg" for a short video clip showing a takeoff, stall turn and a landing. The landing shows the solid control available right down to a crawl. http://www.donatelli.net/contest/

Dunno for sure that you're wrong about flat stabs....airfoiled stabs just work better in all flight conditions, in my opinion. There are many wise pundits out there in www land that will vehemently argue that it's a waste of time and that flat plate tail surfaces are the only way to go! I really like 'em and don't mind investing the extra time needed to design and build them. Plus, they just look cool with transparent covering.

DICKEYBIRD

Just watched the movie, SUPERB !!. Sounds like a really annoyed wasp. I see what you mean about the more than adequate pitch control.

It might perhaps have something to do with you having a higher mast than mine, this give more of a lever for the drag of the rotor. Also my gyro has 6 degrees of downthrust...yours ?

Perhaps I should have thrown a .049 in my model just to see if it would fly !! I know mine flew well on its original AP.09 Hornet before I replaced it with the .10.

Also what aft rake did you settle on ? Mine has 8 degrees aft with 8 degres hang angle.

Great stuff

Sean

Thanks Sean! You're right about the annoyed wasp sound....that's the only thing I haven't been able to do anything with on the Cox engines. I've been able to work out most all of their other kinks through various modifications and they now start easily, idle well, have good throttle response and a strong top end. The real life sound is somewhat better than the tinny, canned sound from the video camera, though.

The Cox thing is just a personal challenge to me going back to my youth when my 2nd engine was a Babe Bee. I've come full circle, from u/c .049's to .40's & 60's r/c, pylon racing, 1/3 scale, etc. etc. and now all the way back around to Cox 1/2A power! It's a technical challenge to build aircraft and engines that perform just as well as their bigger brothers....but I love it!

The Gyrator has 5 deg. downthrust, 1 deg. pos. in the H/stab, about 8 deg. mast tilt (not sure, been tweaking it some lately) and the hang angle is about 10 - 12 deg....again not sure since I have been carving a little more weight off and haven't rechecked it lately.

Randy Wrisley's "Gyro Schtick" (RCM const. article) has the same rotor dia. as your 'Dervish and has flown with .061, .074 and .09 power but weighs only 16 oz. Yours would more than likely do great on a Norvel .074 since they are such a power animal but probably wouldn't fly at 22 oz. on one of my old antique Coxes.

Here's a link to the Gyrator const. thread over in the 1/2A forum...it has some more pictures and details if you're interested: http://www.rcuniverse.com/showthread...hlight=gyrator

ps: Your v-tail idea is way cool! You think it would work better with more area??

Thanks for the info Dickeybird, sounds like we both ended up with much the same setup with the exception of the powerplant.

I only ever used .049 on my old gliders as power pods or in small control line planes when I wuz a kid. A friend of mine does have a .049 helicopter with the .049 throttled by a variable sleeve around the exhaust port. Tail gyro is by a lead weight hanging under the tail rotor which uses pendulum effect to alter the tail rotor pitch as it twitches !!.

The V-tail did look good but came with some nasty suprises. Small rudder inputs caused sudden roll in the same direction as the input. Also side gusts would almost flick the model on its back. It was very interesting to fly but I do not think I will pursue V-tails on gyros in the future. Possibly with a lot of testing it could be made to be the sole control of the gyro eliminating any DC requirement but I don't have the patience to try it out now that the conventional sysyem works so well.

Only problem with our small gyros is orientation, I have to fly them really close or get eye strain !! I think I might add white tips to the blades to see if this helps

I will go take a look at your Gyrator link now.

Sean

I see that `Whirling Dervish` has its servos in the open, my own aircraft seem to get covered in exhaust gunk, mainly castor oil, how is this avovided? Maybe don`t use castor oil?
Colin Duthie

Colin

The servos do get some gunk on them but its not anything like as much as you think. Its not in the photos but I attach a small exhaust extension tube which pretty much places the exhaust far enough out from the fus to not be a problem.
Its not pefect but it works !

Sean

HI
I love the design!!!
Did you ever get a plan together for this model?
If so i love to get a copy and build my own.
Many thanks
Rob

Hi Rob

Sorry no plan available. The model flew very well but was not the beginners craft I was really after......very manouveurable but not that stable compared to some. That is why I am building a co-axial design for just rudder elevator.

Sean

Is anybody marketing a Gyro kit based on this line of thinking? .10 to .25 size.
Thanks