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Old Mar 23, 2010, 12:44 AM
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Gasser Scale "WNF 342 Doblhoff"

Hi guys,
I'm going to attempt my own scratch build of a scale pusher(mainly because I'll never own a Tempest). Here's a list of some of the design goals:
-30-50cc Gas engine
-True scale head(which will probably be my first compromise)
-Built-up blades
-modular in design so it can be broken down for transport
-It must be Ugly
-Complete in time for the Muncie fly in

I am only planning things out for now, but I want it to be very large. The power plant will be a 30-50cc Gas engine. The rest of the aircraft will be scaled to that end. The drawings and details will be made available as I develop them. I don't intend to make a single penny, I'm doing it for the love of the hobby, and wouldn't want to be bothered with the hassle involved anyway(Besides some would just steal my plans and sell them on E-bay).

I've narrowed the candidates for the build down to two. One is a German design of which I have very little information(Not even sure of it's name). The other is a Pitcairn YO-61.
If anyone has any details or info on either of these aircraft, I would greatly appreciate your input. I'm trying to aquire some good line drawings to plan from. I'm also interested in all input and opinions. I would very much like to find scale drawings of the actual heads used in these aircraft to build from. I'm sure machining the bits will cost me a fortune since I'll have to hire the work out.

I realize that neither of the two aircraft would win any favor from anyone that has been blessed with the gift of sight, but I am oddly drawn to both of the poor ugly ducklings.

Regards,
-Mike
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Old Mar 23, 2010, 08:06 AM
AND FOR MY NEXT TRICK....!
jodini's Avatar
Omaha Millard, Nebraska, United States
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Man Mike....how many projects do you have going here!?!?! Work must be slow!

I love this project....very different!
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Old Mar 23, 2010, 09:17 AM
It was a GLITCH! Honestly!
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Mike,
I have sent you a PM about the Tempest but have heard nothing back

Anyway I like the look of the new project..very different..Joes right you have too much time on your hands

Good Luck mate



Regards Rich
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Old Mar 23, 2010, 10:20 AM
Suck it and see
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Cromer, North Norfolk Coast, UK
Joined Aug 2008
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Hi Mike,
This project sounds great!
I think the German one is ugliest, and therefore the best candidate. The only lead I can find to it's identity is here http://barnstormingblog.blogspot.com...fa330-wnf.html

The WNF 342 V3 - V4 Doblhoff. Put this ID into Google and read more!

Good luck.
John
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Old Mar 23, 2010, 12:22 PM
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Quote:
Originally Posted by SafeLandings View Post
Mike,
I have sent you a PM about the Tempest but have heard nothing back

Anyway I like the look of the new project..very different..Joes right you have too much time on your hands

Good Luck mate



Regards Rich
Thanks Rich,
Unfortunatly I've not recieved any of your PM's, it's probably a problem on the site. I'll be taking your advice and trying my own thing. I only hope I can do something cool with the project.

John, thanks for the information leads.

Joe,
I figure as fast as you build you already have on ready for testing after seeing the thread.

Dave(Imsofaman),
You did some work with built-up blades in the past; any reccomendations?

Regards,
-Mike
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Old Mar 23, 2010, 07:22 PM
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Hey Guys,
I agree that the German WNF 342 Doblhoff is the ugliest and most sinister of the two, and have elected to go that route based on John's encouragement.

The aircraft was really more of a convertiplane than an Autogyro, or Helicopter. It had tip jets on the blades for takeoff/landing and had a helicopter style swashplate. The pusher prop was disengaged for hover. There was no need for an anti-torque system since the tip jets produced no torque on the rotor mast.

I'm currently bidding on the power plant. A 50cc Gas engine to which the rest of the ship will be scaled. I'm still looking for accurate line drawings to scale from. I've worked some numbers based on the 20" prop the Gas engine will turn, and rough scale from pictures and best guess, the main rotor would be approx. 96" dia. (Insert 3 manly male grunt noises here)

I've found very limited info about the machine. I like the tube structure build, and should lend itself to easy duplication. This project is quickly moving to the top of my build list.

I found a few more pics.

-I will most likely use a 3-blade scale heli for the head since it will be easier than machining one. The cyclic inputs with a swashplate will require much less torque than a tilting rotor system in most of my other autogyro's
-I don't have plans at this time to install tip jets, or have a blade collective pitch feature

I'm pretty stoked about this....I'm looking for input and opinions guys.

Regards,
-Mike
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Old Mar 23, 2010, 07:32 PM
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Quote:
Originally Posted by jodini View Post
Man Mike....how many projects do you have going here!?!?! Work must be slow!

I love this project....very different!
Work isn't slow Joe, but I sit in the full scale stuff for 8hrs at a time, and I'm building in my head during the dull bits.
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Old Mar 23, 2010, 10:35 PM
AND FOR MY NEXT TRICK....!
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Omaha Millard, Nebraska, United States
Joined Sep 2004
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You have a cool job Mike and I rather it be dull than people trying to shoot you down!

I love the new project. Looks very interesting so I hope you give it a go!
Joe
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Old Mar 24, 2010, 02:46 AM
Suck it and see
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Quote:
Originally Posted by Boneswamped View Post
...I sit in the full scale stuff for 8hrs at a time...
Mike,
At the scale you intend, you will have another one to sit in!

Look forward to hearing of developments, please post progress.

John
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Old Mar 24, 2010, 09:01 AM
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Yo 61 please!!!!
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Old Mar 24, 2010, 03:36 PM
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Quote:
Originally Posted by imsofaman View Post
Yo 61 please!!!!

Ditto!

Ken
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Old Mar 24, 2010, 05:59 PM
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Hey Guys,
I hear you on the YO-61, it's a cool aircraft. That being said; the Doblhoff has several characteristics that make it more appealing to me as a project:

-The angular shapes with the tube structure will be easier to duplicate. I intend to make the airframe from tubing with brazed or soldered joints.
-There is no complicated compound curved windscreen to replicate(particularly the nose section of the YO-61), it's just simple flat panel sections.
-The hinged front end of the cockpit area(which I intend to incorporate) lends itself to easy access to radio gear and fueling.
-The head I'm planning to use could utilize collective pitch at a later date with nothing more than a programming change. Who knows if it flies well, a tip jet attempt might be in order.
-As a career full scale helicopter guy, I have a fondness for the developmental roll the Doblhoff played in the helicopter's lineage.
-It's uglier and more sinister looking

If those reasons have failed to change your mind, then I would love to see your YO-61 build thread as soon as you get started. I'll still, however, be moving forward with the German aircraft.

I've been searching for line drawings with no luck. The history of the Doblhoff is fairly illusive, and has often been mis-labeled a helicopter contributing to the lack of accurate information. I'm trying to become a subject matter expert on the aircraft, but at present don't know much more than is posted here.

Regards,
-Mike
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Old Mar 24, 2010, 06:24 PM
Suck it and see
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Hi Mike,
I'm with you on the Doblhoff idea for the reasons you gave, plus the fact that it's obscure. When built it will be fairly safe to say that it's the only one of its kind anywhere. With a 3 blade setup as scale, it will be more likely to be a good flier too.
Better shut up or I will be persuading myself to build one

Good luck.
John

PS Mike, your last 3 pics on post #6 are not clickable to upsize.
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Old Mar 25, 2010, 08:32 PM
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Quote:
Originally Posted by Boneswamped View Post
s.

-I will most likely use a 3-blade scale heli for the head since it will be easier than machining one. The cyclic inputs with a swashplate will require much less torque than a tilting rotor system in most of my other autogyro's
-I don't have plans at this time to install tip jets, or have a blade collective pitch feature

I'm pretty stoked about this....I'm looking for input and opinions guys.

Regards,
-Mike
I think the swash/heli head is the right way to go. If you CG correct the blades at the 1/3 chord and make the bolt hole the same the control loads will be very light. A tilty-cyclic head with three blades at this size will need some serious servos, not to mention getting the damping right on the head. More than likely at this size the three bladed head will be very controllable, and you can always add tip weight to get it under control. As an easy (but maybe costly) bailout you can always add one of the flybarless control systems that are readily available now and make it fly any way you want.
I wouldn't remove the collective function myself. WIth the tilty heads you can tilt the whole rotor back and speed up the spin up. With a cyclic head you don't have that tilt to work with so being able to reduce the pitch will greatly help the spinup. You could probably couple the collective with throttle so the pitch comes up to the right value just as you reach takeoff throttle setting. Just an idea to play with.
I'll be watching your progress.....
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Old Mar 25, 2010, 11:54 PM
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Thanks for the input Mickey,
-I agree with you on the collective function, good point. It shouldn't be too difficult to setup the way you mentioned with some simple radio mixing.
-Do you think the three blade swash set-up would be controllable without a flybarless control system?
-If the head were mounted with enough aft tilt for spin up(as in a roll only setup), utilizing swash function for cyclic functions; do you feel it would still need collective?
-I'm leaning towards a rigid rotor setup with lead/lag(Accomplished with the single blade mounting bolt) and flapping occuring in the root of the blade mounting(most likely with a small segment of glass fiber between the blade and the grip), of course feathering would occur at the blade grip.

There are a lot of unknown variables to me in this project, and that's another reason it interests me. I have zero experience with swash controlled Autogyro's. The limited pics and info I can find about the WN-342 seam to show the head mounted level. I think it could get away with this because the rotors were spun beyond autorotational RPM with the tip jets. There must have been a lot of inertia in the system with the heavy jets at the tips. Your experience with this type of setup is invaluable to this project, so I'll appologize in advance for the many ignorant questions to follow.

Regards,
-Mike
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