tailess design
 

Of all the tailless designs I have seen with out an elevator the fuselage has been relatively short. Does anyone know why this is or is this just for looks? Could you take an airplane and just eliminate the elevator and stabilizer and add elevons? Any suggestions would be welcome,thanks for your time,Mike

RE: tailess design
 

Here are my thoughts.

yes you could , you would just need to rebalance.

I would think that the reason for a flying wing design would be weight savings and simplicity. Iwould say this is probably the reason they usually have a short fuselage.

RE: tailess design
 

Thanks very much for the reply,my next bird will definetly not have an elevator,the only other ? i have is wich way is up and down on the ailivators, is it the same as the elevator?

RE: tailess design
 

All the control throw directions are the same.
welcome
Kenny

RE: tailess design
 

If you use an airfoil - for example, symmetric - designed for a conventional plane and remove the tail you will need to add some aileron reflex and you will need to move the C.G forward. My understanding is that 10% - 15% is good place to start for the CG. Both are required if you expect the plane to fly. Everything I know about this I learned here, so buyer beware :D

The reflexed airfoil has lower lift and higher drag. So you can expect to fly faster and require more power.

I'm converting a old stick. The wing will get new bigger ailerons (reflexed!), the engine will move back a bit, and a new rudder will be constructed just behind the wing.

RE: tailess design
 

A few flying wings have been made with full length fuselages so that the rudder would have a full effect. In fact someone even made a pattern model that looked like that.

There was also a guy with an Ugly Stik where the stabilizer would eject on demand and the model flew fine after.

To do that sort of stuff you need a proper airfoil. Either a special positive type with a lot of reflex in the camber line or a symetrical airfoil with the elevons set for some up trim to provide the reflex.

The elevons are a mix of aileron and elevator. They go up for up elevator and down for down elevator. Ailerons work the same as before but with the mixing you need to be sure the hinges have room to accept the angles the extra throw of up elevator and up aileron in combination. Generally you need the usual amount of aileron travel and often a very reduced amount of elevator travel.

RE: tailess design
 

Fin, rudder area needs to be enlarged quite a bit because of the short tail moment arm.

RE: tailess design
 

This works...
http://home.earthlink.net/~pjburke1/Tailless.htm
And this...
Cutting (knocking) the horizontal off, reflexing the ailerons, making them elevons, and a c.g. at 15%-20%..
had a short happy and vigorous life! :)

RE: tailess design
 

Thanks for all the replies but what does reflex mean?

RE: tailess design
 

Raise both ailerons a bit.

Look the three airfoils here: http://www.mh-aerotools.de/airfoils/nf_4.htm

... you see how the trailing edge comes up a bit.

RE: tailess design
 

Okay thankyou veary much,that explained it all, I will get some pics posted as soon as the plan starts to take shape,thank you again for your time. Mike

RE: tailess design
 

As there's no tail surface to balance the effect of the airfoil pitching moment, normal airfoils when used on tailless planes need to provide that balance.
This is done by offsetting the control surface trailing edge up a few degrees.. -relfex-
Or the airfoil can be purpose-designed to include the reflex in the shape..
Basically per the sketch.
As a symmetrical airfoil has no pitching moment it can get with less reflex, as long as the c.g. is ahead of the wing's mean aerodynamic chord, providing the nose down opposition to the reflex.

RE: tailess design
 

You probably haven't seen the Bill Evans Scimitar series of flying wings. He had one for pattern he called the Tracer. It had a fairly long fuselage, but used elevon control. The Tracer was in the 8-86 issue of RC Modeler magazine and they have plans available. Check their web site for plans and a picture.

The wing doesn't really care how long the fuselage is. There used to be a GeeBee flying wing and also a P-51. They looked funny at first until you realized they didn't have stabs and were flying wings.

RE: tailess design
 

Morris Hobbies builds a Spinsation, a wild flyer if toomuch power is used.

RE: tailess design
 

Well after all these years I am finally getting around to this project. It all started at the LHS when I was given the tail feathers and wing to a super kaos 40. I am sure that this is the older original kit. So this is my plan, strip the airlones off and make them bigger, the wing already has two servos in it that came with the wing. Scratch build the front fuse portion to fit my engine. Which will be a older os .61fs four stroke. Add a rear fuse to mount the rudder which will be located directly behind the wing. I thought i would just epoxy and glass the fuse directly to the wing. I was able to measure the original fuse length, do you think I should keep the front portion of the fuse the same as the original or change it and make it longer?

RE: tailess design
 

You'll need to balance the model at a position forward of the 25% point. Probably in the 18 to 22% area. So a slightly longer nose isn't a bad thing.... but then again this is a 61 and that's quite a lump.

Can you mock it all up and then hang the engine on with rubber bands and get a feel for the CG? Just slap on some wood guessing at roughly the amount you think you'll use. We're talking ballpark at this point.... a BIG ballpark.

RE: tailess design
 

Well I did mock it up last night. I framed up the fuse and added 1 inch to the nose for good measure and it needed more room for the gear and tank. At 6 1/2 inches stock the front is small so 7 1/2 will give me the room I need. The motor mount I am using is fairly long so that will give me some room for error.

RE: tailess design
 

One of the Simitar plans was offered in a magazine back in the late '70s. A school teacher friend and I blew the plan up using an opaque projector. Foam wings were cut and the Simitars were flying in a week. They started out half A but before it was over, his was converted to a .19 pusher with a home carved prop with landing year. Mine is still hanging on the wall. If memory is correct, the half a version having no throttle, if gotten into a flat spin... would spin all the way to the ground usually without harm.

That design did not have a reflex foil but it was asymmetrical.

In those days, mix was done via a sliding servo tray.

RE: tailess design
 

Actually if you were to draw in the mid line of the airfoil you'd find that it does have reflex and a lot of it. That is combined with the maximum camber location being much further foward than normal. Both the foward camber location and the reflex in the camber line are all you need to fly a plank style wing. The reflex doesn't need to actually be obvious in the outside shape of the airfoil. When you know what you're looking for though you can see it easily.

RE: tailess design
 

Reflex act like decalage. The more nose heavy, the more reflex, decalage. Same as a conventional configuration. Built a couple of 25 size combat foamies quite a while ago with a conventional symetrical wing. TLAR airfoil, about 1/8 in. reflex sort of followed the lower contour of the wing. Twin rudders to get enough rudder area without having an overly large single rudder. CG aroung 15 %. Very quick and agile. About 1/8 in. washout helped it not snap out of a tight turn. Fun to experiment:D Although they don't always work.

RE: tailess design
 

This is a Krafty 25...
http://users.adelphia.net/~pjburke1011/Tailless.htm

RE: tailess design
 

Plane like that would be cool at a funfly. Do a slow flyby in front of the crowd, pull a pin and the whole tail falls off and the plane keeps on going. Hmmm. Have to think about that one. Which plane of mine will be the sacrificial lamb. They're all looking at me with a sour face except the Pizza Box and it's just grinning like this.:D

RE: tailess design
 

Looked something like this? Built one with a Black widow .049 on it and a homemade mixer tray, looks like a bird in fligh becuase it's very maneuverable and small. I still have mine in the shed, but it looks real bad! I need to build another one. Also Built a .40 size Gremlin both are good flying planes.

RE: tailess design
 

Don Incoll in Australia did this with a Stick.. the horizontal was actually a fully flyable sloper.
He'd take the combination off, "lose" the horizontal, and continue to fly while the horizontal glided to a landing.

RE: tailess design
 

The ingenuity of aeromodellers makes me proud.:) becoming a lost art.