For those who have flown both, how does the flat plate wing fly compared to a wing with say a 10% airfoil? This will be good info. for people who plan to build the 3DX, Trident or similar flat foam type planes in the near future. Thanks.

A flat plate airfoil tends to act the same in all angles. They almost always fly at about +5* and are very effective in the pitch axis. However, they do not float in on landings unless power is kept in, and they glide very poorly.

An airfoiled wing usually likes to fly level, and will rock back and forth in a harrier. They fly at about +1*, and will tend to rotate along the pitch axis more slowly than a flat wing. They glide very well, and usually fly nearly to a stop on landings.

Of course, there are many exceptions to these generalizations, but this stuff is pretty close.

Dan

if you go up to a 20% foil, she'll be a slow flyer, but she'll float beautifully...would make a nice aerobatic trainer

brad

rcmann, I have a 11oz 3DX and it glides very well as a matter of fact if you keep these things light you will hardly notice the slight angle of attack it needs to generate lift. If you have a CG that is aft, your glide ability will dimminish if you keep it in the normal range it will glide just fine.


POWER

The good news is, we all figured out that the flat plate wings work just fine. Not long ago, nobody thought they worked at all. I really don't think you can go wrong either way. Tim H's comments sum it up very well. Some people simply like to have a "built up" wing. I like the simplicity of a flat plate for the good crash worthiness and great ease to repair it.

Probably the best advice is to just try both and give both a good flying season to compare all attributes: flight character, ease of construction, ease of repair, crash durability, etc.

Derek

Hear, Hear, Derek. well put - i prefer built up for the performance, but you can't beat a plate for simplicity 6 of one/half dozen of the other.....

brad

There is an article in the February 1982 issue of Model Airplane News by Andy Lennon in which he plots the lift/drag ratios of various airfoils, including a flat plate, curved plate and semi-symmetrical.

It turns out that at low Reynold's numbers (<40,000), curved plates are best, followed by flat plates and finally semi-symmetrical.

At higher Reynold's numbers (>120,000), the lift/drag ratio of the semi-symmetrical has significantly improved, while the curved plate and flat plate remain roughly the same as they were at 40,000.

The formula for Reynold's number at sea level is

Speed(mph) X Chord(in) X 780

At low speeds curved plate and flat plate are best.

At higher speeds the semi-symmetrical is best.

The key factor in the curved and flat plates, however, is the fact that they are linear and their performance does not change with speed.

A semi-symmetrical airfoil can give a nasty surprise when coming in for landing because the lift that it provides decreases not only because of the decrease in speed, but because of the decrease in performance at low speeds.

This helps explain the terrific performance of all the IFO's, Sukalyns and 3dExtras.

Thanks for all the good input to my question. I plan to try out a flat airfoil first.

3 more things about airfoil vs flat...


Wingloading!

Wingloading!

Wingloading!

Keep it as light as structurally possible!
The best planes I have ever flown had low wingloadings.
Yes a flat plate wing is easy and they do well in our
situation. But you should try both and make your own decision.

I have made comparisons between both types flat and airfoiled.
Yea - it's a more difficult to do a built up. but I must say
the airfoiled wing is much sweeter to fly.

Remember the more that prop has to dig in to the air to hold that plane up flat or airfoiled the more you will have to fight
the plane in the stall regime.


Ronster

Ronster