Flatplate wings, which planform is best suited?

[rcjetpilot]

Hi All,

I’m thinking about building a few 480 sized planes and would like to use a flatplate wing. Normally I would just use a true airfoil, but with such a small wing (<32 span), the simplicity of a flatplate design is tempting.

So, my question is this: Which type of wing planform lends itself to the natural aerodynamics of a flatplate?

1. Highly tapered.
2. Swept back.
3. Delta.

Thanks in advance,

Bob.

[BMatthews]

The planform is more determined by how you want to fly and what you want the model to look like. However consider that a flat plate is used on 3D models as much for just a spot to mount the control surfaces as it is a way to provide lift. If speed is your goal (swept and delta options suggest this) then a flat plate will be fine for straight line stuff but in the turns you'll find that the flat plate airfoils stall sooner and produce more drag so a sharp turn will bog down the model more.

[rcjetpilot]

Hi Bruce,

Thanks for taking the time to drop in and post some comments, it's greatly appreciated.

Let me add some additional detail (I should have mentioned this in the beginning), I'd like to build a few Mini480 edf planes. I could use a few for those for last minute dashes to the field to get some quality stick time:)

So the type of plane will be in the "jet style" family and speed is king. At the moment I'm considering two designs, one is highly tapered; the other is a cranked delta. No foam stuff, just good old balsa.

Seems to me the flat plate has an interesting characteristic in that the root thickness is sufficiently less then the tip thickness. In effect creating an artificial washout? So if this is kind of on track thinking, I’m curious to which planform lends itself better to the natural characteristics of a flat plate.

Bob.

[BMatthews]

.....Seems to me the flat plate has an interesting characteristic in that the root thickness is sufficiently less then the tip thickness. In effect creating an artificial washout? So if this is kind of on track thinking, I’m curious to which planform lends itself better to the natural characteristics of a flat plate.

Bob.

That only applies to a proper airfoil. The flat plate becomes blunt enough that I suspect you won't get that sort of advantage.

I would imagine that you'll want to do some snappy high speed turns. With the sheet wings you'll have to turn wider to retain speed. For me that would be a killer. Far better than to use a sort of decent airfoil to help avoid the stall.

[Scaledown]

Highly tapered wings usually have a tendency to tipstall. With the low stall angle of a flat plate, that could lead to some nasty handling.
My vote is for swept back with moderate taper.

[rcjetpilot]

Hi Scaledown,

Thanks for the post. I seem to remember reading somewhere that flatplate wings in general, have a bit more pitch to thrust line coupling then a standard airfoil but at lower speeds the issue is minor.

I just don't know if the preceived simplicity of a flatplate can be coupled with a favorable planform. Me thinks I'll just build and fly:)

Bob.

[Foxy]

Don't rule out using a finishing sander and 10 minutes to give the wing some profile. Works for me.

All the best.
Adam

[acvar]

If performance is important, at the speeds we fly you should never sweep your wings. It lowers effeciency. It does very little to reduce drag at subsonic speeds, and it drastically reduces lift. The same goes for delta wings. The only use for a swept wing on our planes is a forwad swept wing for its better stall characteristics, but that can be achieved with varying the chamber, with just a little more effort, and will not have the loss of effeciency.

[Scaledown]

Interesting information, acvar.
I suppose that's why pylon racers don't have swept wings. So you really need to decide whether you want jet style (looks fast) or straight (goes fast).

[kdwzagi]

in the turns you'll find that the flat plate airfoils stall sooner and produce more drag so a sharp turn will bog down the model more.

i have found that my flat plate (6mm depron) 38" spitfire does bog down in tight turns so i agree with that but i have not managed a tip stall yet so i'm not too sure on that one


kev

[John Threatt]

Find the thread in Foamies about Jerbears Simple Wing. Its a flat plate wing design with a 1" dihedral and a J250 motor. The only feeling I have about the Aeronautical principals involved is admiration. It flies well even in a 12MPH breeze. I built two for my basic needs and 6 more bodies in an afternoon for future wear and tear. Simple is its middle name but its great KISS design will have you smilin at the flying field, Cost minus flight pack is less than $4. Intermediate pilot skills only since Inverted flight and areonautics are possible.

[vintage1]

Surely the issue with a flat plate is you can hardly make things worse whatever planform you pick :D

When I ws a kid I used to make chuck gkliders out of balsa sheet. Loads of fun, and some were better than others.
Fighter jets wioth swept wings used to dutch roll.

But averything else worked OK - deltas, fake warbirds etc. I even built a profile triplane out of sheet. With an 020 on it. The flew too! Glided like a brick, but flew.

I tried a Jetex Starfighter. That was not successful,. Today I would bungee launch it and it would probably fly.

The answer is knock up a chuckie, and see how it works.