Thanks to a gentleman in Bangalore, Mr. Lingaraj, I have got hold of an incomplete MK Models ( Kato) kit of Hanno Prettner's legendary Curare, in a 20 size

It's a very old kit, and a fair number of parts are missing - fortunately mostly balsa/ply which can be replicated

About Prettner -  http://www.rcindia.org/rc-general-topics/hanno-prettner-living-legend-of-rc/msg297475/#new

Plans from Outer Zone

Will be using an ASP 25 Glow Engine

The plans only have the right wing, so, after 44 years I did some GT (Glass Tracing). Last done to copy Engineering Drawing Assignments in 1974-5





Now I've traced and pencilled a left wing on the reverse side of the plans ( a mirror image, so to speak)

@sanjayrai55,
Sir,
Guess the dark wood is from the kit and the whiter pieces are new, right?

Is the original material balsa?
Regards

Quote from: K K Iyer on February 01, 2019, 06:38:29 PM
@sanjayrai55,
Sir,
Guess the dark wood is from the kit and the whiter pieces are new, right?

Is the original material balsa?
Regards

Correct on both counts sir

I have had very limited exposure to quality kits. In the late 80's, I had 2 OK Model (Pilot) kits, and a few years ago a Great Planes kit. This is my first MK Kato kit

I must say the balsa quality is exceptional! I have encountered 4 different grades of balsa, selected for the application. Even the ply, while being light, is extraordinarily hard. Brilliant kit maker, Kato

Wing ready for covering

Since I didn't have 15 mm thick balsa, made the wingtips from 3 different sheets glued together 

The horizontal stab has an anhedral!   

Started the fuselage

just another awesome build  by Sanjay sir!!
By the way how would anhedral stab affect how the plane flies??

I myself am not too sure  Looks cool, and Hanno Prettner said to use it

The most logical explanation I found was in RC Universe:

RE: anhedral on horizontal stab
An engineer once told me that the anhedral on the F-4 tail was to help with low-speed yaw stability. The tail of the F-4, like most airplanes, generates negative lift, so anhedral on the horizontal tail would actually work like dihedral for a wing (it's stabilizing). This seems to imply there is a tradeoff with yaw stability while inverted, which of course wouldn't be a problem for the F-4.

As for RC aerobatic airplanes, especially so-called 3D, I doubt it has any benefit. The anhedral adds effective side area to the tail, which is the same as adding more fin area. It does add it down low, however, which might help knife-edge tracking if it is done properly, but that's only theory, and I believe that was the thinking behind the Curare tail. I remember some discussion about it in the '70s (or was it the '80s?). It seemed to work, but then so do many other designs without anhedral. You would probably have to be an aerodynamicist or an avid experimenter to design it so there is any discernible benefit.

If you think it looks cool, a little bit probably will not hurt. Or if you think you need to redistribute the vertical stabilization area lower, it might help.

As for adding maximim side lift capbility, there would be no benefit at all, since adding tail area is stabilizing. Good knife-edge lift has a lot to do with the proper balance between area ahead of the CG and area behind the CG. All else equal, adding effective fin area, without changing anything else, will make it harder for the rudder to yaw the airplane and generate side-lift. Also, the length of each horizontal stabilizer/elevator would have to be multiplied by the secant of the anhedral angle to keep the same pitch effectiveness, which would of course increase weight slightly.

However for my (very limited) flying skills, I don't think I'll be testing, or valuating it's use

Quote from: sanjayrai55 on February 07, 2019, 04:35:42 PM
The horizontal stab has an anhedral!  

Sir that anhedral stab is the signature of the Curare.
With a flat stab it'd no longer be a Curare!

I'm glad you had one of the other unique elements - the thick fin leading edge.
Hope you have the chin block too...
Regards

great going sanjay sir.

Thanks Iyer sir; yes, the chin block and thick fin LE will soon make their appearance

Thanks Manoj. You are always encouraging

Right now I'm in an intense struggle: the design called for an oval fuel tank of 150 cc capacity, with the larger axis horizontal. Can get no such tank, nearest is a rectangular 180 cc. To fit that, there is fouling with the wooden engine bearers. So I've decided to use a Glass Filled Nylon mount. Which brings it's own complications in installing - tight space. I also want to use a steerable nose wheel against the fixed one supplied

Sir,
A few suggestions
1. If you think 90cc will suffice, check out MD rum ka bachcha. I've been considering one for a 10 size model. It's quite oval.
2. If you omit EM1 and EM2, there should be enough space for a round or square section tank. Without printing the plan, I'm not able to estimate the available space. Pl let me know. Then I'll see if I have something suitable.
3. If possible, skip the steerable nosewheel. On such a small streamlined model it's not worth the effort
4. If going radial, please finalise the holes in the firewall and mount the flanged nuts before starting the fuselage. The nose is complete on mine, and the flanged nuts epoxied to the back of the firewall. No way to make matching holes in the radial mount. I'm not able to bring myself to cut the cowl free! See pic.
5. If you don't have 4 flanged nuts and matching bolts, let me know. I think I got some in 2006!

Quote from: sanjayrai55 on February 07, 2019, 04:36:43 PM
Started the fuselage

Iyer sir, the picture doesn't tell the whole story, but the FW is already glued in place, with blind nuts fitted. The Engine mount is also fitted, and the Sullivan flex 180 cc tank fits fine. 90 cc is too small for a 25 Engine. Just that everything is very cramped.

The cowl blocks will need multiple holes for tightening the Engine and mount bolts, and the exhaust bolts. Also, I'll be keeping the Engine upright, not at 90 degrees.

Regarding the nose gear, I'm still deciding.

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