OfFrOaDfReAk22

Ok guys i was watching th emilitary channel and they were showing planes that were experimental and one of them was a plane the looked like it had the wing backwars it was like a v but facing forward. heres a link http://www.aerialpostcards.com/scree.../EC87-0182.jpg basically what i wanna kno is it possible to make a plane like this that would be able to be a extremespeed propplane. if so this would be one hell of a plane. also is ther maybe something like this already out there. if so do u have a link. thnks

BMatthews

It's quite possible as long as you follow a few guidlines. First, you don't try to fly it with the scale balance point. The X29 was one of the first aggresively computer augmented stability test planes. The real one was descrived as trying to fly an arrow backwards. Without the computer the pilot was way over his head and would just pull the eject switch.

X29's have been done in model form already. I'm not sure where or who though. Google?

As for it as an extreme speed prop plane I think you're going to find that it's a problem unless you take some serious freedoms with the scale outline. The engine has to go in the nose or the tail. Either one is a long way from where the CG should be located. That point would need to be confirmed but from the picture it looks like it should be roughly where the little V is on the inner portion of the leading edge. That puts it smack dab in the middle of the airplane and a LONG way from where the engine would be. And on a prop speed model that spells trouble since the engine is so heavy in relation to the model. A severly shortended nose with the radio gear mounted back in the tail may do the trick.

OfFrOaDfReAk22

so its possible then

BMatthews

Definetly, it's been done before by others so there's no reason you can't. But you need to address how you'll compensate to get the CG in the right place without having big weights at the extreme ends of a rather long fuselage.

In the meantime to play with where you'll need to put the CG why not make a little all sheet balsa test glider with about a 16 inch wing span and play with it. You'll learn a lot towards the final prop jet and have a cute bit of inspiration to hang over your bench while you build the big one.

perttime

There is a foamy electric plan here:
http://www.parkjets.com/free-plans.html

You might be able to adapt it (?)

I recall that the forward swept wing might be a challenge in terms of getting it stiff enough under flying loads.

strawtarget

Heh. This is an awesome plane... one of my all-time favorites. It has often graced my computer's desktop background, and I have a little plastic model of it in my office. I considered modeling it in the distant past, but gave up because of a few factors, some of which have already been mentioned in this thread.

1. Like BMatthews says, you can't use a scale balance point. The balance point has to be moved, and the people who have modeled this plane seem to indicate that it flies better if you augment the size of the canards to better match the changed CG. Because of my tweaky "it's gotta be freakin' perfect" nature, I can't have that kind of deviation from scale.

1.5. Getting the CG right is possible with a ducted fan install, but difficult with an engine/prop at the front or rear (like BMatthews already pointed out).

2. Like perttime says, forward swept wings need to be built with EXTREME rigidity if you plan on flying the thing fast. If you look into the design history of the X-29, you'll see that the engineers say the major breakthrough that made that plane possible was the construction materials and techniques employed to get an extremely thin airfoil wing to be rigid enough for the planned flight envelope.


If you just want to build a plane "like" an X-29 with a canard and a forward swept wing but not necessarily a "scale X-29", then I think you have a very viable idea and a fun design challenge. With the freedom to change the planform around to suit the CG, it'll be fine. Designing a thin, fast wing that's rigid enough would be a fun challenge. I say "go for it".

cyclops2

Since your flight speed is nowhere close to scale, and the scale air molecules are much farther apart, you are absolutly allowed to change wing airfoil and thickness. [sm=thumbup.gif]

sscherin

My Feedback: (1)

I'll 2nd the part about getting the wings as stiff as possible..

The big problem is that if the wing tips flex up or down at speed they generate more lift at the tips thus flexing the wing more.
This goes on (quite quickly) untill the wings break form the stress.


Back in the 80's I was playing around designing a canard forward swept wing slope glider.

Like BMatthews said I started with a small free flight test glider and learned alot from it.

My first rubber band launch with the test glider ripped the wings clean off

fledermaus

There is a lot of information on forward-swept wings on the net - check out a few of these:

[link=http://www.aerodyn.org/Wings/fsw.html]http://www.aerodyn.org/Wings/fsw.html[/link]

[link=http://www.centennialofflight.gov/essay/Evolution_of_Technology/foward_sweep/Tech9.htm]http://www.centennialofflight.gov/essay/Evolution_of_Technology/foward_sweep/Tech9.htm[/link]

[link=http://www.airforce-technology.com/projects/s37/]http://www.airforce-technology.com/projects/s37/[/link]

Note that one of the first forward-swept wing aircraft was the 1906 Santos-Dumont No. 14bis (the one that some people say flew before the Wright brothers - but let's not start that debate here!). It was a canard biplane/box kite with very slightly forward-swept wings. You can see some period pix of this plane at [link=http://www.aerospaceweb.org/question/history/q0189.shtml]http://www.aerospaceweb.org/question/history/q0189.shtml[/link].

There were also several gliders built by an American named Cornelius during the 20's . The most notable early example was a Junkers project during WWII, designated Ju287. You can read about this and see some interesting pictures of wind-tunnel models of this project at [link=http://www.geocities.com/hjunkers/ju_ju287_a1.htm]http://www.geocities.com/hjunkers/ju_ju287_a1.htm[/link]. In fact, the Soviets captured the prototypes and actually developed them in the post-WWII years - this knowedge might be the basis for the Sukhoi S-37 of the 1990s.

Thus, many experiments have been done, and some production work, right from the first days of flight up to the present. Slow-flyers and fast flyers. Why not RC flyers? Go for it!

Ed_Moorman

My Feedback: (1)

A lot of the possibilities depend on whether you want a scale prop-jet or just a swept forward canard. A swept forward wing canard is easy. Here are some photos of a canard I have been flying. It was co-designed by my buddy Carl "Flaps" Laffert and myself. His previous canard was a pusher with a swept back wing so we decided to go with a tractor design this time. The wing is a 4*40 wing kit. The proportions we came up with. It turned out to be slightly nose heavy so it required some lead in the rear. A swept forward wing would move the required CG forward so we would have been better off.

The problem with forward swept wings is under g conditions they twist the tips to a higher angle causing tip stall. Planes like the X-29 have a composite wing that resists twisting. Here's what I mean by twisting. Look at the picture you uploaded. Draw an imaginary line from the leading edge at the root to the trailing edge at the tip. Under g conditions, the wing will bend like normal, but it will twist along this line with the tip rotating upward. This puts the tip at a higher angle resulting in a tip stall.

You need to insure that your wing is pretty stiff. On the 3 forward swept wing (FSW) planes I have designed in the past, I used foam cores and fully sheeted so they couldn't twist. They were excellent fliers. If you use normal construction, add some diagonals, top and bottom to help resist twist. FSW planes are great in crosswinds and mine would lock in on final, some of the best landing planes I have owned.

OfFrOaDfReAk22

thanks guys. im really going to read up on this and if it takes me a long time to do this then so be it. i only 16 so if i can make a prop driven x-29 i can just say it was one of the most bad ***** accomplishments of my life. the reason i chose this was iat first i wanted a propjet and looked at a tigershark and the cermark f-16 but there all arfs and if i got them i wanted to glass and paint them in military scheme and that would result in taking off the momokte and etc. so i figure witht his plan i can do what i want staticly and then the facotr of the pride and being able to say i made that plane. so look maybe later on and ill do a build thread. im going to see what kinda help i can get in the aerodynamis section so ill cya guys around

speedbrake

Hey,
I built a plane from MAN plans (I think it was MAN or possibly RCM) that resembled the X-29. It used a .45 engine in a pusher configuration. It wasn't scale but did have the basic configuration, forward swept wings, connards, single vertical fin. It flew great! It was very stable and fast. As I remember it also landed resonably slow....in fact it didn't have many flaws. The wings had a foam core and the fuselage, cannard, fin were all balsa. I recommend looking for this plan and building this particular model. I think you will be pleased with the looks and smooth flying. You could go more scale after playing with this model.

Cheers,
Speedbrake

speedbrake

OK...to keep this tread going I will design, build, and fly a .25 or .32 size model of the X-29. I built a one third size glider of the proposed model. It has a 1/4 inch profile fuselage and 3/32 inch balsa sheet lifting surfaces. The proportions are correct (wing, canard, and fin areas have been increased) but it looks ackward because of the profile fuselage. The fuselage is 15 inches long and the wing span is 11 inches. The red line on the fuselage is the CG. The glider really does glide well....and that is very encouraging! The model will use four channels; ailerons, canards, throttle, and nose wheel steering. I'll try to keep the fuel tank on the CG to keep it simple. A fixed gear will be used.....if the design proves to be robust then perhaps some retracts can be installed in a future model. I'll keep this thread posted of my progress. Speedbrake
[img][/img][img][/img]

speedbrake

OK...to keep this tread going I will design, build, and fly a .25 or .32 size model of the X-29. I built a one third size glider of the proposed model. It has a 1/4 inch profile fuselage and 3/32 inch balsa sheet lifting surfaces. The proportions are correct (wing, canard, and fin areas have been increased) but it looks ackward because of the profile fuselage. The fuselage is 15 inches long and the wing span is 11 inches. The red line on the fuselage is the CG. The glider really does glide well....and that is very encouraging! The model will use four channels; ailerons, canards, throttle, and nose wheel steering. I'll try to keep the fuel tank on the CG to keep it simple. A fixed gear will be used.....if the design proves to be robust then perhaps some retracts can be installed in a future model. I'll keep this thread posted of my progress. Speedbrake

OfFrOaDfReAk22

awesome glad someone stepped up to the plate.

BMatthews

Speedbrake. I deleted the first post where you didn't get the pics in and cleaned up the second without changing the part you wrote.

Nice test glider! I wish more folks that want to build oddballs would play with the concepts this way. As I'm sure you found out it's amazing what you can learn from a simple test model of this sort. A LITTLE discretion needs to be allowed for the basic lack of stability due to no dihedral but if the model shows strong signs of divergent rather than only neutral stability that should be an eye opener. Similarly if you know how to read the pitch stability by the way the model recovers from a purposely induced stall it can tell you a heap of info about the CG position.

And the best part is that after you are done playing with it you can donate it to a youngster and infect a new person with modelairplanitis or at least have a nice mobile hanging over your bench....

speedbrake

I am about done with the plans. However, the placement of the engine is still in doubt. Placing the engine on the nose would (to me) destroy the looks of the model. A pusher configuration is what I want but might prove to be difficult to accomplish because of the weight vs. CG location. If I can get the fuel tank on the CG and have a reliable fuel flow to the engine then that's the direction I'll go. I'm looking for a suitable fuel pump now. That being said, I'm pressing ahead with the drawings and will change them as needed.

The glider provided interesting results. It glides straight ahead with no tendency to fall off on a wing tip. Throws which caused a stall showed the glider will roll off on a wing tip and didn't recover. I was interested in where the CG was. Somebody in an earlier message suggested the CG would be at the leading edge of the wing, and that's is where it ended up. That provides me a starting point for the model's CG location. I'll still use a CG program to confirm the CG location. More to come. I'll start cutting balsa tomorrow. Speedbrake

speedbrake

I'm having trouble adding photos. Please....somebody explain to me how it is done. It says to: "for image uploads click reply or quote icons in any post above". That doesn't help!!! On some messages there is a box for adding attachments, but it isn't showing all the time...such as this reply box.

Thanks, Speedbrake

BMatthews

The [ image ] [ /image ] (without spaces so it shows here) is for linking to pics on other websites.

For posting pics from your own computer you need to use the File Click here to upload! controls directly under the text box where you are typing your reply. But this option is only available from the POST REPLY buttom option. It is not there for the QUICK REPLY box.

From there you need to ensure that the files are sized to fit within the max file sizes. Most digital camera pics are far too large as they come raw from the camera. Use a photoeditor to reduce them in size and quality until they are somewhere around 60 to 80 K in size.

speedbrake

I have the plans about done. The ribs require (for me anyway) a CAD program. As soon as the ribs are drawn, I'll be able to start cutting balsa. I'll start on the wing first because it will be needed for the fuselage construction. The fuselage is 45 inches long and the wing span 33 inches. It was necessary to enlarge the lifting surfaces. No decision yet if it will be a pusher or puller. I'm leaning toward a pusher.....the nose of the X-29 is to elegant to mess up with an engine! In a pusher configuration, the engine will be hiden from view by the wing. More to come. Speedbrake

Ed_Moorman

My Feedback: (1)

We got to thinking about the SWF canard idea and decided to go ahead and do it. My buddy, Flaps Laffert does the construction. Here he is with what we have so far. The wing is from a crashed World Models SkyRaider Mach II. The last rib was removed as the tip were crunched pretty badly. Forward sweep is 6 inches which should help the CG of our canard-it was nose heavy and required lead to balance. It will probably be ready to test next weekend, given good weather.

speedbrake

I finished the plans and have started cutting balsa. The wing is on the board and ready for the top sheeting. The wing is looking real small....at least to me. It is slightly larger than a F-18 wing I built from MAN plans for a .32 size pusher. If fact the planes are almost identical dimension wise. However, the F-18 has a huge strake that adds a lot of area. Where as the X-29 only has the canard which doesn't have the same amount of area.

The wing will be sheeted with 1/16 sheet top and bottom. The structure was put together over the bottom sheeting. The landing gear block has been installed. The structure seems to be very rigid...I hope stiff enough. I hope to have it off the board tomorrow and begin the fuselage. Speedbrake

OfFrOaDfReAk22

when you are finished is ther anyway i can get these plans from you if the plane proves a sucess?

speedbrake

Yes, I would be glad to share the plans. It would be great to see a fleet of these unique looking planes flying around. I think it most likely some redesgin will be necessary...but that's all part of designing your own model. I get more satisfaction building my own planes than buying and flying ARFs.

The vertical fin and canard are done, as is the wing. The fuselage is on the building board now. The fuselage consists of four 3/32 balsa side pieces cut from 48X4 sheets. The main fuselage is 40 inches long (nose block and exhaust cone will add another five inches). The intakes are about half that length. The main fuselage should be joined today and the intakes attached tomorrow or so. 1/2 inch tri-stock will allow the corners to be sanded to a nice round shape. The turtle deck behind the cockpit will be assembled separately and attached after the main fuselage is done. Perhaps the most difficult part for me will be duplicating the canopy. More to come, Speedbrake.

OfFrOaDfReAk22

cool thanks by the way awesome build. i cant wait to see and hear about its maden voyage. so far is it pretty hard or fairly easy. also have you decided on a pusher or puller and what engine will you use?