Replies to This Discussion

Permalink Reply by James F. on November 10, 2010 at 3:30pm

1) I would base the airfoil off of an existing airfoil. From the looks of your airfoil you will have a lot of lift at slow speeds, but also a ton of drag and large moment. There are many tools you can use to come up with the wing design (x-foil is a personal favorite) or you can do the sizing by hand since all of the equations are very simple and easy to find online.

2) You'll want to make the hinge line of your flaps straight.

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Permalink Reply by Ryan on November 10, 2010 at 3:43pm

For the sake of simple construction since you dont' have a lot of experience I would recommend the Clark-Y Airfoil

You can get some idea here

Also move your aileron further out to the tip of the wing and just give it a straight taper is good enough.

R

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ModeratorPermalink Reply by Sgt Ric on November 10, 2010 at 3:58pm

Ryan is right, the location of the ailerons is too far inboard (more suited to flaps) and the aileron taper is inefficient.

As your control surface moves, the outboard portion separates from the main wing and looses any authority at all and only induces more drag.

Most UAVs designs try for better loiter capability than heavy-lift-VTOL design (as represented by your very aggressive airfoil)

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Permalink Reply by Ramon L on November 10, 2010 at 6:49pm

I recommend the WORTMANN FX 60-126

Attachments:

• 1.png, 29 KB

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Permalink Reply by William Gross on November 10, 2010 at 7:01pm

Thanks a ton for the input. The Clark-Y design looks like something that I should use. Is the Clark-Y design more suited for slow flying and simple maneuverability? Also, should I use elevators instead of ailerons? Im looking to do mostly loitering as it will hopefully be in the air for awhile and be easily flown so it will integrate with the autopilot easier.

What effect does the lower camber have? More lift but slower speed? The design I used was an existing airfoil and I just didnt know which airfoil characteristics affect which flying traits, so maybe a less aggressive shape will go a long way for my purpose

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Permalink Reply by Ryan on November 10, 2010 at 9:38pm

Are you looking to just build a flying wing?

That changes everything!

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Permalink Reply by William Gross on November 10, 2010 at 10:08pm

No, Im looking to build the fuselage as well. A rendering of my design is below

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Permalink Reply by Ryan on November 10, 2010 at 10:11pm

Yes, but just a flying wing without horizontal stablizer right?

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Permalink Reply by William Gross on November 10, 2010 at 10:20pm

The model that is rendered is not totally finished, I still need to add the horizontal stabilizer and make the nose a bit more aerodynamic. You cant tell by the rendering but there is also a rudder on the vertical stabilizer

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Permalink Reply by Stephen Wuest on November 16, 2010 at 7:43pm

Question: what is the size of your plan? Your really aggressive undercamber could work for very light planes, but is very aggressive for anything but a super light plane, or a massive lift machine!

Comment: The Clark-Y is plain vanilla, but the current standard aviation airfoil has a bit of up curve on the bottom front. The NACAXX12 series are somewhat modified flat bottom airfoils, that have a little better characteristics than the classic Clark-Y. Wikipedia has a couple drawings.

Unless you're going to completely build the wings yourself, you could order precise foam cores from flyingfoam.com in about 15 different airfoil patterns, from 24" out to 72", and sheet them yourself.
flyingfoam has a number of common airfoils used by RC flyers. They also have a Clark-Y. The RG15 is a bit slicker, with a little under camber. The Selig Donovan airfoils are also used a lot.

After picking a safe and generic airfoil, make sure that you get enough square inches of wing, and tail surfaces. And try to compute total plane ounces/square ft of wing. This wing loading is important, and a safe wing loading depends on the size of your plane (which is why I asked the size of your plan). 5-6oz/square ft is common for very light sailplanes, but a 6 ft wingspan glow plane may have 24oz/square ft. Pick the wingspan so that you will get a safe wing loading number.

Also, think about the surface area of the vertical and horizontal tail. Small planes need a bigger tail surface than full-size planes, as a ratio to the main wing. In your rendering, the horizontal tail is quite small, and would require a high airspeed to provide "grip".

Go for it!

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Permalink Reply by Stephen Wuest on November 16, 2010 at 7:53pm

Elevators are for up-down control. Ailerons are for roll control. If you have elevators and ailerons, you can "yank and bank" turn -- roll a bit left, add a bit of up elevator, and the plane will turn left. With ailerons and elevators, you can do without a rudder. But you can't do without an elevator.

You can also turn with just elevators and a rudder, but it becomes more difficult to level out the wings for landing without ailerons.

The Clark-Y is a simple and straightforward wing. (Good.) But the speed at which your plane will fly depends on the wing loading. Make the wing loading light, and it will fly slowly. Make it heavy, and you will have to fly fast to keep it in the air. So fast or slow is not mainly a function of the Clark-Y airfoil.

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Permalink Reply by William Gross on November 10, 2010 at 7:39pm

Also, Here is the fuselage Im working on. Still have alot of refining to do with the shape and also need to add the elevators. It will be lasercut out of some light material for the frame and then covered with a composite such as fiberglass or carbon fiber.

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