This aircraft has been designed by Jean Claude DEBREYER and is now manufactured and marketed in kit form by the company Air Est Services in Marley, France. 

3-view drawing of prototype JCD-02 by Philippe Vigneron.

Specifications for the JCD-03: 

Span                    7.2 m 
Length                 3.1 m 
Area                  12.0 sq. m.

Main Chord         2.0 m 
Thickness           17.0% 
Empty Weight     80/85 kg 
Max Weight           175 kg 
Engine                 One Solo 210cc (15hp) 
Pusher Propeller  .75m diameter 
Cruise Speed       75 km/h

Hello everybody,

It is not my style to tell rumors, but this one is nurflugel-related and might be interesting to some of you.  Somebody mailed me that Michel Mangenot, the man behind the production of the Pelican-kits, is planning to retire.  I haven't got a confirmation yet, but I know that Michel Mangenot is not one of the youngest.  So it might be true.
     The history of this French flying wing (unswept) is very short.  Only two were built.  One was the prototype, which was constructed out of wood.  Later a mold was made and this mold made two kits.  One was finished and built by Jean Claude Debreyer, the designer of the Pelican.  The other is probably still stored in the firm of Michel Mangenot.  It was still there when I went to visit the firm (in 1999 or 2000).
     Jean Claude flew his Pelican for 10 years.  He calls himself a Sunday-flier.  Has 200 hours in 20 years.  JC told me that the Pelican is easy to fly, even for beginners.
     I am very tempted to buy the second kit, but my money is spent on another project.  But I worry about the molds.  If Michel Mangenot retires, what will happen with the molds???  Will they be sold, will they be stored in an attic, will they be ... destroyed.  I don't know.  But people who need a place sometimes or change their lives do strange things.
     My question: Is somebody interested in buying the molds and starting a small production himself (if it is true that they will be sold)?  Or it there somebody who can store the molds for future plans if Michel Mangenot needs to make space for other things.
     If Michel Mangenot truly is going on retirement and he finds nobody to buy the molds, I am thinking (very vague idea) about getting the molds and store them at my parents place (my place is too small).  Maybe I can get an agreement with Michel Mangenot to get the molds for free and place them for rent to possible kit-makers and to give this rent to Michel Mangenot.  Again, my ideas are still a bit vague! But I want to do a lot to save this flying wing from disappearing from the earth.  I like it too much.
     Are there any persons who have other ideas that can tempt Michel Mangenot to keep this flying wing alive if he fails to sell the molds.  All ideas are welcome.  How did other great kits stay alive?
     Keep that brain spawning wings,

Koen (a bit emotional after receiving the retirement-message)

I have had several emails from Michel, I keep pestering him for plans.  I would encourage everyone to write him and inquire about plans.  Without the molds the fiberglass work would be difficult to duplicate, but perhaps a redesign in wood and fabric is possible too.  Would buy the other kit, I think it is reasonably priced, but the shipping to the US would be the killer, same with his molds, not practical except for someone with big bucks.
     Koen... have you talked with JC now enough to have all the skinny on his Pelican.  Were you able to get any construction photos?  I would like to build it, if enough information could be obtained.

So any comments on the Pelican design philosophy?  If I understand the various translations correctly the main points are these:

1. A thin high aspect ratio wing will be heavier than thick low aspect ratio wing. (I assume that the fact that either have to carry a load about equal to the dry weight of the craft has some impact on this.)

2. If the goal is to gain altitude under minimum power, than a wing with aspect ratio 4 was preferable over a high aspect glider type wing because lower weight of the shorter thicker wing is preferable over higher L/D of the higher aspect ration thin wing.

In general are these statements true? Can they be quantified?

I would like to thank all who did an effort to translate the French text.  I hope that some of you can use the translation text in their site.  I will in mine.
     I just sent a letter (snail-mail, JC doesn't have e-mail) to Debreyer with a proposal that maybe can save this design from being stored in somebody’s attic. It is a VERY UNCONVENTIONAL proposal (hey... it is a Koen-kind of thing). It could end into nothing, but with a bit of luck it might get some more Pelicans into the air at a low cost. I keep you informed. Cross your fingers ... it might help.

     The JCD02 was the Pelican prototype, made of wood, equipped with a Peugeot 125 cc motorcycle engine and a 69 cm diameter propeller. Weight 60 kg empty. It flew well but its strength was probably inadequate. The JCD03 was practically the same design, but much more solidly constructed of epoxy/glass laminate. Heavier (80 kg) and provided with a single spar set further forward on the chord, the 17% ABRIAL section was not accurately followed and caused me to lose the advantage of the 12 horsepower of the SOLO 212 engine. The aft position of the engine made it impossible to increase the engine's weight, hence its power. The ground clearance of the propeller did not allow a large propeller to be easily employed, which made for long takeoff runs with the 74 cm propeller. The purpose of these two flying wings was to verify that for flight with minimum power, an aspect ratio 4 wing was needed, and not the narrow wing of a glider. To gain altitude it is better to save some weight than to increase aspect ratio. And as it happens, a narrower wing is a heavier wing. That is also the reason that I preferred a 17% thick wing instead of 12%. Struts would have had the same effect. The single wheel landing gear also allows a consider- able weight saving (the forces are transmitted directly to the pilot's buttocks, without extra material).  Alas, the balance wheels were set too far aft, which made ground handling difficult in a crosswind. This airplane was very easy for anybody to fly who had 20 hours on a conventional airplane.
     Though a limited span makes possible a light machine that can climb on low power, it does not allow soaring (glide ratio 10-12, 2 m/s sink). But cross-country flight is very pleasant with excellent vision forward and downward, worthy of a helicopter.

Koen added:  With this letter JC Debreyer answered my questions about the different types of Pelican and why he choose to use a 17% high airfoil and not a lesser draggy 12% high NACA 23112.  I still have the idea that the Pelican is a extraordinary design. It brings a closed cockpit, a stable platform, a extraordinary view and a eye-catcher to the beginning pilot.  Man, how I will hate it if this little jewel's molds will get lost in one's attic.
     I will stay in contact with JC Debreyer and follow the only flying Pelican to its final destination (exposition at the local flying club in Romorantin, hanging at the roof of the club). I will try to get some pictures through JC Debreyer.  I sure hope you like the new info.

Does anyone know where the CG should be on the Pelican?
     How was the Pelican controlled in flight, relative to the two rudders?  Should they operate independently, articulating only out and back to neutral, or joined together as a pair, and move in unison equally in each direction like the rudder on a conventional plane? 
     Are the rudders effective on the ground at low speeds, because lets face it, the fan is not blowing any air over them, as they are positioned at about the mid point on each wing half, and in line with the prop. 
     At what speed would they become effective on take off?  In flight, are you flying with the ailerons only in a turn, or it necessary to control yaw with rudder inputs in a turn?  The pictures I have seen do not clearly show whether there is a separate elevator type control surface, or is pitch controlled with a mixer of some kind ,using the ailerons as elevons? 
     The Pelican does have a very fat short wing with a wide chord.  It looks easier to construct than a long wing with a narrow chord, and thinner airfoil. Which is more efficient? Many low Hp designs I have seen look more like gliders with long narrow wings, and everyone is always saying because of the wing tip vortices, that is the way to go, but the Pelican seems to disprove that?  When the goal is to fly on low hp. not gliding? What is to be preferred? 

     There have been some questions about the balance between horsepower and wing span for an aircraft like the Pelican.  There is a technique for calculating such a balance for an aircraft design.  One example of it is described in Airplane Design Part 1.- Preliminary Sizing Of Airplanes, by Dr Jan Roskam.
     Essentially, specifying the payload, range and performance requirements and applying equations for aircraft weight and performance lead to an answer. Specifying the payload and range leads to an estimate of the gross weight. Specifying stalling speed and landing performance leads to an estimate of wing loading.  Specifying takeoff distance and cruise speed lead to estimates of power loading and climb and ceiling lead to estimates of aspect ratio. 
     The results are plotted on a graph with power loading on one axis and wing loading on the other.  Lots of tradeoffs are done.  The preferred aircraft usually has the least power loading and the highest wing loading of those that are feasible and just meet all the requirements.
     I applied this technique to a two seat aircraft recently.  It was a flying wing, although the method does not distinguish that fact.  I specified a 400 lb payload and four hours fuel and arrived at a TOW of 1600 lb.  Specifying takeoff from a 2000 ft strip on a warm day and a cruise speed of 150 mph each give different combinations of power loading and wing loading that are feasible.  Climb and ceiling also result in the same sort of curves but with aspect ratio a factor.  A warm day climb of 1000 fpm and a 17,000 ft ceiling led to an aspect ratio of 6.  Landing in 1200 ft with a CLmax of 1.6 gave the required wing loading. 
     Plotting all this information on a plot of power loading vs wing loading, suggested that an aircraft with a power loading of 16 (100 HP) and a wing loading of 12 (wing area 133 sqft) with aspect ratio of 6 and Clmax of 1.6 would likely be a good staring point for a design to meet these requirements in the most economical manner.
     This is a preliminary method.  Subsequent detailed design may cause changes in the preliminary values. 

Here it is, step by step: (ed. – This is Ronen’s reply to Mike Lee’s questions, indicated by the .)

I thought the proper CG location was a function of the computing where the CL was and how it changes at different angles of attack.

Cl has no point of operation - it is a coefficient, not a force.  CG does not change with AoA.  For most parts, until stall, Nor does the lift move around that much.

I guess I want to know where it should be on the Pelican, is it similar to conventional aircraft, you want a CG around 25-30% chord?

Mostly lift is at around 25% of chord.  But - which chord?  The Average Aerodynamic chord.

Flying wings are a new concept to me, and when you start getting into pusher configurations, I guess the optimum location is often very different from a conventional tractor setup.

HUH?  How so?

Sometimes the CG should be almost at the leading edge I think. I never did understand why that was so.

Frankly, neither do I.  I don't think I understand your statement above...

It would seem there should be proper CG relative to any specific airfoil, but I guess there are other factors to consider, because I have seen one design where the CG was supposed to be at about the leading edge.

CG location depends very little on the type of airfoil.  Trim may depend on it, but not CG.

Graham's method helps you figure roughly were the CG will fall when you have a relatively scale layout of your wing and tail, and helps you figure the distance between them, that sort of thing if I understand correctly.

It has nothing to do with figuring any distances, apart of showing you where the average aeronautical center is located.  Know that, and you can set CG easily.  So, why a flying wing would be different?

Maybe all this stuff is a little too basic for you guys here.  I have been reading the posts here for some time and I admit it seems you guys are into some real advanced theory here. If you don't have time for this basic stuff from a rank beginner I will understand. 

No problem.  And there is no more complicated theory for flying wings than for any other types of airplanes.  Not until you try to pry the last 1% of performance improvement!

     Thank you for your well thought out response, I'm sorry, but if anyone can answer the questions I posted about the Pelican, I would still like to read them. I just don't seem to have the ability to plug this stuff into some graph and come up with an answer that I would have any confidence in. Particularly when there seems to be two or three different bell curves, which must intersect, with figures in #, Mph, Hp, weight in Kilograms, etc., up and down four sides of a graph. I can stare at that stuff for hours and not come up with any thing that makes sense to me. I guess that is why I didn't become an engineer. 
     When I was taking ground school for my private ticket, my instructor had to walk me through some of those, I guess my brain is just not wired for it. 

     Hi Andy,  I have just spotted J.C. Debreyer’s Pelican on the TWITT site. The design philosophy and layout would appear to be similar to my Sgian Dubh (SD), although the SD is bigger and heavier. There doesn’t seem to be an "e" address? and I wouldn’t mind a wee chat with him. 
     He refers to an "ABRIAL" section, what do you know of this section and has it reflex ? `cause I have never heard of such a thing.  The other snag is that, if I could contact J.C.D., I don’t speak a word of French. 
     The weather here all summer has been very poor, so nothing much has been done by way of testing, quite apart from the authorities reluctance to countenance such an action.  Methinks I should get myself a partner in the good old U.S of A. 
     With all this crummy weather, I have had plenty of time on my hands, so I have finalized a third design of less outrageous layout, a more conventional high wing, taildragger, single seater using the same construction as the Iolaire and the Sgian Dubh. Most of the detail drawings are complete along with all the calculations that I think are required. Assembly starts this week.
     Keep up the good work!

1) I am happy to see you found your way to the nurflugel mailing list. This group is filled with professionals AND with model builders, bookworms and enthusiasts. You will find a lot of data there or guidance towards usable info. I will from now on contact you through the list. If I make a technical mistake, I am sure that others will correct me.

2) DOOOOOON'T GIVE UP ON THE PELICAN (or the unswepted flying wings). I don't know if you are a patient type, but the last few months I found data about the Pelican, which was unknown for many years. I do think that I have a good contact with JC Debreyer. I do think that I might get the info you wish. I am close to getting pictures. I do hope for you that there are also construction pictures.

3) I saw your questions on the list. Pity, you didn't ask these questions the first time I was writing a letter to JC. I could have asked them. Well, I will put them in my next letter. I will search my own pictures too to see if I have a picture of the technical part of the Pelicans kit. I didn't place all the pictures on the Nest of Dragons-site.

4) It is a pity that the JCD02 was constructive less good than the JCD03. I still believe that a JCD03 - similar design can be made with wood, but I am not the person to ask how and I am not sure that you will be possible to keep the weight as low (when making the same strength as the JCD03). Things like this get me scratching my hair too. Not a engineer too. 

5) About the design: a lot of other low power engined designs do indeed look like gliders with long and narrow wings. They started their design from the idea to get a low as possible sinkrate. If the sinkrate is low, the engine needs not much power to keep the airplane at the same height. This point of thinking is very common. JC Debreyer began his idea at another point. He wanted to reduce the weight at the best. Long wings are heavy wings, that is right. Choosing a high airfoil makes it possible to make a lightweight spar. According to Jack Lambie's book I think to recall that a spar with double height is 4 times stronger ... or was it stiffer. Damn memory... Can anybody correct? Well, once you have a ultra low wing loading you might not have the best possible low sinkrate (the drag of the Pelicans wing is high due to its high airfoil), but it gives you a chance to use a light engine too. I still don't understand the link between low wing loading and low power. I know about low wing loading and low speed, but I never saw this other relation explained. Anyway, JC did design his JCD03 that way and it did work.

6) Further development of the Pelican: I do think that JC Debreyer has a very good design. It is compact, not much parts, little construction costs, little flying costs.  But it could use a larger engine and a larger prop (most common comment).  How can one do that? Well, I don't suggest to use a front placed prop, but I suggest to use a ducted fan. Place the engine central, make a duct from the point after the spar to the end of the fuselage. Use this duct as a constructional part so it gives rigidity to the fuselage. The prop might still be small, but the efficiency of the prop is higher. The engine placed after the spar may be heavier, due to the shorter distance to the CG. A rudder might be placed in the ducts end to ensure efficiency at low speeds.  But you loose in the basic design of the Pelican, because you add weight. And this might get you into a totally new design which ask you look again at the size of the wings and the wanted perform-ance (speed, low costs in flying or shorter take off).  I myself would be super happy if I simply could build a Pelican like it is.  But I just wonder how it would perform when a central engine would be placed (like Mr. Mangenot suggested first at my visit to the firm).
     Man, again a looong mail. Sorry, folks.
PS. There was somebody who wanted to see pictures of the Pelican. My Pelican pages in the Nest of Dragons site (see link halfway the homepage of www.nurflugel.com) has some pictures of the unfinished kit and a Pelican
scale model.

     Regarding the larger engine, the engine I have in mind weighs about  70#, and this is quite a bit more than the 10Hp JC uses. However, we have to redesign the thing anyway, so just move the Pilot forward. I weigh 3x more, or less (actual less, than the difference in weight of the engines) so I move forward a little to keep the CG in the right spot, (if we know where that is supposed to be). I was real surprised no one could really look at the design and say, well it should be about at the spar, by the look of things. And yes I know what is Mean Average Cord, but not all designs seem to follow the 25-30% of MAC, and the reasons are unclear to me. I have seen a design with a constant cord wing and pusher configuration, with the pilot out in front of the Leading edge and the CG was indicated in the picture to be about under his Butt, several inches in front of the leading edge.  Totally new concept to me, I have been building RC for 35yrs, and I never flew anything like that, but I have never built and flown a Pusher either.
     Thank you Koen, for your response, it came at just the right time, I was ready, after trying to pin this stuff down for about 2yrs. now, to just give up and build a traditional tractor design, and be content with sitting in all that prop blast, and be less than happy.
     I did blow up the drawings I have of the Pelican this weekend, with the thought in mind of building a 1/3 size RC model to work out where the CG should be through flight tests, that is if it doesn't self destruct before I figure out about where that is.

Hello Andy,

     Sure am happy that the Pelican gotten so much attention lately. It has been a very unknown airplane the last years. I am glad to be opening doors for the Pelican. It is a too much interesting type (referring to the idea of "a plane for the man of the street" and to "budget flying") to go by unnoticed.
     It is very strange that I got in contact with JC Debreyer through a mailing list about flying fleas! I think I have a good contact with JC now. Sure hope to get some pixs soon.
     About your contact ... let me guess... Euh ... Hmmm... Mike Lee, isn't it.  (ed. – It was really Henry Matthews hm0062000@yahoo.com, and http://www.luft46.com/hpmpub/hpmpub.html)
     Mike contacted me too. He hopes to construct a similar design. But he is near loosing hope because he gets so little info. Pity, but I don't have the info he asks. I know that the JCD03 flew relatively a lot (JC has 200 hours, a real Sunday flyer). But I have no clue about the JCD02. I will ask in my next letter to JC.
     The pilots of all JCD's will be JCD himself I think. I never heard or read about other pilots. But I will ask too.
     I am happy to see Mike found his way to the mailing list. Sure hopes that he will not loose hope and will continue with his will to construct a unswepted flying wing.

Koen wrote:
> 5) About the design: a lot of other low power engined design . . .

In the past, this has been true, but not any more.  A 15 meter sailplane wing can be built of composites and the wing weighs only 75 lbs.  ±7 G's, all controls, pushrods, mixers, flaperons, ailerons, & spoilers.  Add a T-tailed fuselage if you must ;-)  and it weighs 135 lbs. empty.  You then have a 80 ft./ min. sink rate, 23 mph stall, Vne ~100 mph, 35:1 glider.  With 35:1 at 39 mph, that means 9 lbs. of drag.  Think we might find a motor & propeller that could produce 9 lbs. of thrust with low fuel burn? ;-) Composites can be wonderful or the devil.

> Well, once you have a ultra low wing loading . . . 

We can now-a-days get high lift and low drag from highly cambered airfoils. The US4 airfoil is a little over 17% thick.  The wing has 7 different modified US4 airfoil changes along the 15 M. span, each optimized for low drag at its design Cl for an elliptical lift distribution.  No wing twist at 0° flap and 6° of twist at 12° of root flap setting.  At 12° of flap, the airfoil at Re 1,000,000 computed Cl is 2.1 with a Cd of .018, a Cm of -.4, at a AOA of 6°.  The power of X-Foil and ASWing are amazing.

> I know about low wing loading and low speed . . .

Wing loading varies between 2.18 - 2.8 lb/ sq. ft.
Stall speed varies between 23 - 25 mph.

We'll see how it flies in late Nov. or early Dec. With higher amounts of drag, we would need more h.p. to over come it.
Thanks,
Dave Swanson
Glendale, CA
Light Hawk is beauty and grace, with charms to which grown men surely succumb.

There are many more considerations then minimum thrust for choosing an
airplane engine - prop combo...

> In the past, this has been true, but not any more. . . .

Up to here, correct.  However, There is still power required to accelerate the thing to TO speed, where the drag can easily be 3, 4 even 9 times larger than at maximum glide angle speed, or minimum, sink rate speed.
     BTW, required power for straight and level flight is about 1/3 HP (net), but - what about climb?
If you want best climb of, say, 400 FPM (totally insufficient, IMHO), you'll need about 2 HP (net) at the best speed.  However, if you want that climb rate at TO speed, you'll need between 8 and 16 HP - depends upon the actual TO speed.  If you want bBOTH to climb AND accelerate after TO (not TOO much to ask. right?), you'll need about twice to three times as much power. These figures are net HP, meaning considerations for altitude, and prop efficiency, need to be made.  Consider that an average prop is less than 66% efficient at low speeds, and...  Reqiored poert for actual TO is already @ the 25 to 40 HP mark....

> Well, once you have a ultra low wing loading . . . 

Low wing loading can actually reduce induce drag much more than the increase in the drag efficiency coeeficient that results from the decrease in AR. The problem is that increased wing area causes an increase in parasite drag, which increased AR does not.  Actual TO, landing and sink performance are MORE influenced by the wing area than by the AR.
     Total drag is big at low speeds (because of induced drag), diminishes to a minimum, and then increases at high speeds due mostly to parasite drag. Induced drag diminishes as wing area increases, and parasite drag increases with wing area.  The minimum point is where induced drag is equal to the parasite, so with increased wing area, the point where parasite and induced
drag are equal will have lower drag, and will occur at lower speeds.

> We can now-a-days get high lift and low drag from highly cambered airfoils.

Yes, we can, but why should we?

> The US4 airfoil is a little over 17% thick.  The wing has 7 different . . . .

This is a very elaborate strategy.  Too elaborate. Goes totally against the KISS - SAAL principle.

Ronen.

Hello Mike,

     When you add a lot of weight to a design, you must keep in mind that you are also adding a lot of needed speed to get airborne. So you get  a higher landing speed (and that is not very good for a beginners airplane) and you increase the take off run (I always love to be airborne before the fence   ;)   ).
     When adding a lot of weight one might better reconsider to recalculate the needed wingarea to keep all factors low (take off speed and take off run).
     A little help from this group might get you on the right track. You might try to just mention your weight and the weight and power of the intended engine and maybe a very helpful soul can help you to calculate the wing area while keeping the performance of the Pelican (very slow riser).

Keep that brain spawning wings,

Koen

PS: Scanning might take a time.
PS2: Later I will try to make a mail that can explain how to construct a few lines on a top view of the wings of the Pelican and to get the most rear position of the CG. The most forward position 
depends on the stability you seek (I read).

Hello everybody,

     Just to mention that I found several pictures that I didn't use in my Pelican page. I will scan them and place them at the files section of the Nurflugel mailing list.
     It are just picture of the fuselage and some views of control surfaces in the making. they give a good view on how the fuselage and the control surfaces are made.
     Hope this might help while waiting for a answer by snail mail from JC Debreyer.

Keep that brain spawning wings,

Koen

> PS2: Later I will try to make a mail that can explain . . . 

Much simpler - print it on a cardboard or Manila paper, cut it, and hang it from 3 points to find the center of the area, which - in uniform materials - is the center of gravity.  this will give excellent approximation of where the Neutral Point is.
     Forward limit depends, most of all, upon control authority, which flying wings are notorious for the lack thereof.  So, not much CG range, and so, better make the chord as large a possible (or reasonable).  The Pelican is quite alright in that sense.

> No one could really look at the design and say . . .

Just mentioned a method - mot as simple as looking, but not much more complex...

> Average Cord, but not all designs seem to follow the 25-30% of MAC . . .

A Canard, perhaps? Not much sense, otherwise... Do you have the drawings on a computer?

Ronen.

Mike Lee wrote:

> Regarding the larger engine . . . . . 

IMHO This issue of balancing the weight of the engine by moving the pilot forward is the strongest argument for pusher props.  Poor visibility is usually a problem for flying wings and, as far as I'm concerned, the best way to fix it is to get the pilot's eyes out in front of the wing.

> I was real surprised no one could really look at the design . . . . 

Simply guessing at the CG from looking at the planform is damn dangerous no matter how experienced you are!  Since you have 35 years of RC experience I assume you know the graphical construction method to find MAC.  That method works pretty well for wings without sweep and would be an adequate first approximation here.   Once you have estimated the AC graphically you can ASSUME a point 2 to 5 percent forward as the correct CG. 

> And yes I know what is Mean Average Cord . . . . 

The CG must have been marked wrong.  The aero-dynamic center of an airfoil will ALWAYS be near 25% chord (at subsonic speeds), on an unswept all-wing the neutral point can't be very far from the AC because the control surfaces don't have enough leverage to compen-sate for an out of trim condition. On a conventional design the horizontal stabilizer causes the NP to be farther aft than the wing alone, and that's why they can be balanced with the CG aft of 25%MAC. A canard has the opposite effect, moving the NP forward. 

Hello Mike,

 > Average Cord . . . .

Was it any chance the Haig Minibat or a Marske Monarch or Pioneer? They have forward sweep. If you only see a drawing with the cockpit, you will get a CG at the leading edge that is right. But you need to keep in mind the forward shape of the wing.
     I will try to phrase how you can draw the most rear CG (on top of AC (aerodynamic center)). You can use this one on a tapered wing (or not) with sweep (or not). But it has to be out of one section. The wing of the Pelican has two sections. But you can use the technique twice and calculate the relation.  How to start:

1) Find top view of wings.
2) Draw in front and at rear of the root chord (= point where wing and fuselage come together) the chord length of the wingtip.
3) Draw in front and at rear of tip chord the chord length of the root chord.
4) Connect these four points with a X.
5) Draw a line at 25% chord. With other words: place a point at 25% of the root chord length (closest by the leading edge)and do the same at the wingtip (closest by the leading edge). Now connect the points.
6) Where the X cross, you draw a line parallel with the centerline of the fuselage. Where this line and the 25% chord line meet is the position of the AC. Euh ... I do mean... take the longitudinal distance between this point and a reference line  and transport that distance towards the center line of the fuselage. With other words: slide this point sideways towards the fuselage.
     Voila. That is how I work.

Now for the Pelican.

     Use the technique on both sections. You get two points. Now you need to calculate a bit. Calculate the area of both sections. Now use some logic. If both sections would be as large, the true AC will be in half of the distance between these two points. If the inner section is larger the AC will lie closer to the point of the outer section (because the point of the inner section has more "weight" (just a expression to let better understand)).
     Now start calculating how large one section is towards the total wing area.  Example: outer section is twice as large as inner section.  So outer section is 1/3 of total wing area. Now draw a point between the two points that is at 1/3 of the distance and close towards the point of the outer section.  Voila de nouveau. That is it.
     Guys, if I am wrong here, please, correct me. I am using this technique for two years in my sketchbook.
     About the most forward distance of the CG of the AC, you can find a good explanation in one of the site that is in Doug’s links page. Sorry forgot which one it is. Guys, it has that section with a lot of airfoils for models and a goooood explanation about CG placing. I recall too something about pylon racers and aerodynamics of rib and fabric constructed wings and something about winglets. Anyway, a good site for nurflugel-fans and not
hard to understand.

Koen wrote:

> Guys, if I am wrong here, please, correct me. I am using this technique for two years in my sketchbook.

A verbal description of this procedure is always difficult.  I've seen it tried many times and it's never satisfying.  Also Koen, it sounds like you may be using more lines than you need.  These two pages from the Experimental Aircraft Association show the how to locate the AC with construction lines.

http://www.eaa62.org/technotes/cg.htm
http://www.eaa62.org/technotes/tail.htm

 > About the most forward distance of the CG of the AC . . 

If you're thinking of Martin Hepperle's page  the link on Doug's page is out of date because Mr. Hepperle recently moved to a new ISP.  I have the currant link on my page: http://www.gj.net/~nmasters/index.html
     You might also be thinking of Michael Selig's low speed airfoil page at the University of Illinois at Urbana-Champaign.  http://amber.aae.uiuc.edu/~m-selig/uiuc_lsat.html

Hi,

Just for fun, to use up a spare hour and to please my four-year-old I made today a Pelican model out of Depron (extruded polystyrene, normally used as thermal insulation behind wallpaper). It has 10" of wingspan, weighs 4g and flies straight, level and astonishingly fast in my living room. See two pictures:

http://jbergmeyer.bei.t-online.de/Pelican002.jpg
http://jbergmeyer.bei.t-online.de/Pelican003.jpg

     I have included a standard AA cell for size comparison. The picture quality could be better, but my digital camera is a very simple one.
     Oh, and by the way, I used the threeview of the Pelican prototype from the Twitt page. It came out of the printer with 10" span, so that was what I used. The wing has a little shaped-in reflex (I chamfered the leading edge from above and the trailing edge from below) and I had to bend the center part of the trailing edge upwards a bit. The C of G is at about 20% of root chord (not that there is very much gravity at all :-) to give enough stability.

Regards, Jochen

That looks really nice.  I bought some Coraplast, and some downspout, yesterday when I was in the big city,  and was thinking of doing a rough 1/4 scale proof of concept r.c. model. I've used the stuff 
before, can put together the major sturcture on some designs in a weekend.  Radio install then takes a little longer, If I can get caught up with my honeydos, will start cutting tommorrow.