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        Is a jedelski flying wing possible?

#1 Moogee Sep 03, 2002 07:03 AM

Is a jedelski flying wing possible?
 
I only ask because I tried to make one for my EDF50 unit and on every attempt to fly it nosed in straight from launch.

Then I looked at it for a while and it hit me... DOH.

In my effort, the LE to 1/3rd chord must be acting as the wing, and the 1/3 to TE section like a huge down elevon....

With a jedelski you need something to hold the incidence of the wing... typically a stabiliser.

Can this be achieved by increasing the reflex (by adding up elevon as the neutral point) or is it just intrinsically not a good idea to try a jedelski flying wing?

I can imagine that increased sweep angle may help - are there any designs that do work?

Thanks

Morgan

PS it was a correx plane, of course, but since then it's been found that a mini mugi is hot on an EDF50

#2 Sture Smidt Sep 03, 2002 07:28 AM

Jedelsky
 
Hi,

I have toyed with this idea for a while. Try the following. Make elevons full span with a chord 20% of the full chord. Reflex the elevons to lie flat when the leading edge touches the table as a starting point. The aspect ratio (span/chord ratio) should be less than 6 and preferrably less than 5.

Elevator travel should be 10-12 degrees and aileron travel 10 degrees. Make sure that full aileron travel is possible both sides when the elevator is full up or down.

On a rectangular plan form with no sweep back the CG should be at 15% chord as a starting point.

Make a light hand launch glider at 1/2 scale, say, to explore CG, reflex and handling.

Good luck!

Sture

#3 Terry Lyttle Sep 03, 2002 11:15 PM

Sure!
 
I have actually LOST a couple of f/f Jedelsky wings, they fly fine. Once you get the dynamics right, just enlarge. The f/ftests should include high and low speed flight, highly banked launches, catapulting, etc. Have fun with it, and experiment! However, don't change ANY MORE THAN ONE trim at a time; as soon as you change elevon setting AND c/g, you learn nothing.

#4 schoey Sep 04, 2002 12:03 AM

Morgan

What size was the mugi on an EDF50? I've got a pile of correx, mugi building experience and an EDF50 sitting here.

I'm halfway through building another mugi at the moment, this one is going to have a MEGA 5T strapped to the back.

Grant

#5 omega blood Sep 04, 2002 02:11 AM

What's a jedelski flying wing ? Or a jedelski for that matter?

#6 Moogee Sep 04, 2002 04:13 AM

Sture - thanks for those suggestions!

Schoey - the Mugi was 60cm span - the builder was Steve Wrona of Eflight Models. Don't know much more about it but he says it was awesome!

Omega Blood - I don't know anything about the theory of Jedelski wings but I think it is a term applied to a wing that has two flat surfaces (typically sheet material) that meet at the highest point of the wing; as per this hugely exaggerated and very crude diagram.

/\
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#7 ChrisP Sep 04, 2002 05:35 AM

I think that the real definition of a Jedelski wing is where the first third of the aerofoil is shaped balsa in a sort of Clark Y section and the rear two thirds flat balsa sheet. All kept in shape by triangular ribs on the bottom. This results in a highly cambered, thin aerofoil.
I don't think that a flate plate wing with a break in it counts as Jedelski construction.
If I remember right from reading Aeromodeller a zillion years ago, well at least in the 60's, the idea came from Eric Jedelski.

#8 Moogee Sep 04, 2002 05:56 AM

Thanks, Chris.
I should have stated that I was making a semi-informed guess.

My previous correx 'Jedelskis' have not required the triangular ribs. I simply hold the angle with tape along the fold.

For lightweight models the wings don't flex much and I've even gone up to a spd400 at 700mm span with no ribs.

They do flex on 'impact' though and with one of my slowflyers I cartwheeled for a landing and it was quite amusing to see the correx wing compress and then 'springboard' the plane about 2 feet vertically.

#9 omega blood Sep 04, 2002 02:44 PM

What would be the advantages or flying characteristics of this type of air foil ?

#10 Terry Lyttle Sep 04, 2002 11:35 PM

Why Jedelsky
 
Seems that the configuration follows the MAC with simpler construction. Mean Aerodynamic Chord is the line in all airfoils that ultimately describes its shape and most of its characteristics. If you look at MAC as a hint about what to expect from a wing, you will see that Jedelsky will be fairly fast, fly inverted not worth squat, but physically will build in 1/4 the time of any other wing.

Also in the 60s, some Brighter Light experimented with "Skinny Lifters", sheet wings steamed to MAC to prove the lift characteristics of various airfoils; typical freeflighter, too much time on his hands...:D

#11 ChrisP Sep 05, 2002 06:16 AM

Jedelski is easy to build. You used to be able to buy the profiled front portions from your friendly hobby shop.

As a high cambered, thin aerofoil it's best used in 'one speed' models such as free flight gliders. If you drive them too fast you will get pitch changes due to significant centre of presure movements.

Jedelski came about in the 60's as an easy way of building wings for towline gliders.

#12 Sture Smidt Sep 05, 2002 06:27 AM

Fenix 400
 
I use the Jedelsky section on my Fenix 400. Its a S400 machine with very nice flying characteristics. The speed range is reasonable and the landing/stall habits are nice.

See www.komtek.no/fly/fly.htm and click on S-Models.

Sture

#13 Pierre Audette Sep 05, 2002 06:36 AM

1 Attachment(s)
It works for me. The biggest problem I had was with yaw stability. I ended up putting a fair amount of twist in the elevons and adding winglets. It flies fine now. It's mainly based on Az Chuck's So Slo 2 design.

#14 Sture Smidt Sep 05, 2002 06:49 AM

Fenix 400
 
1 Attachment(s)
The Fenix 400. Plans are available.

#15 Terry Lyttle Sep 05, 2002 10:36 PM

Jedelsky
 
I ain't so sure on this one-speed thing. I know that A1 gliders look for an ultimate l/d ratio, and that is how I flew most of my stuff. However, I was browsing through an old Model Builder, and there was a photo of a sloper that had a speed envelope that went from walking to 70mph; not much limit there!

Working on the info in that article, I chose Jedelsky for my F89 sloper, still under construction; I will find out for myself if there is a "best" speed for that type of wing or not. Gotta say that building that wing was not a big part of my evening, including aileron hinging (old fashioned zigzag).


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