Bad Driver

Guys,
I was wondering if anybody out there has any experience with designing & flying scale(ish) WW1 bipes?

Are there any preferred airfoil sections? I am happy to sacrifice quite a lot of scale accuracy for a better flying model but the wing still needs to look 'authentic' if possible.

I have a plan for a 1/6 scale Ansaldo A.1 and would like to enlarge it and use it as a guide for a 1/5 ( 60.5" ) sport-scale model (I'll probably extend the nose a little too to help balancing - see pic below. Electric powered btw).

Any advice would be much appreciated!

Thanks,
B.D.

khodges

My Feedback: (1)

I don't have the design background for actually determining the airfoil shape on a plane, I trust the kit designer for that. The true airfoil for most any WWI plane would be an undercambered shape, meaning the underside of the airfoil is also curved upward (convex) and the chord is fairly thin. This makes for an inherently weak wing due to a small main spar, which requires functional flying wires to support wing loads during flight. Most of the popular kits have an out-of-scale airfoil that includes minimal undercamber, or even a flat-bottom airfoil with a relatively thick chord section. This design allows for a stronger "I" beam type main spar that can even be "D Boxed" (leading edge sheeted from top around to bottom of spar) for even more strength. The flat bottom airfoil also makes flying characteristics better (greater lift at low speeds). I know the higher end builders like Mick Reeves and Proctor tend to use more scale airfoil design, where Balsa USA is at the other end, and Glenn Torrance is sort of between. All are very nice looking planes when built, and unless you are well versed in the technology of the day, won't notice the difference when you look at one of any of their planes. Of course the Fokkers of the day used the thicker section airfoils (cantilevered wings) so the thick wing is prototypical for them.

That will be a great looking plane, I haven't seen one before. Try to keep the tail construction light as possible so you don't have to stretch the nose. Electric will be nice, especially for scale detailing as it will be easy to hide the motor.

B.L.E.

It's my understanding that a lot of WWI pilots lost their lives not from being shot down but because of the unforgiving nature of WWI aircraft during takeoffs and landings. I'm sure that if they are faithfully scaled down, the model will be just as unforgiving as the full scale planes were. I would suppose that the lightest wing loading achievable would be your friend here.

The nice thing about E-power on WWI models is that the heavy batterys can replace the lead needed to give the gas versions of these planes enough nose weight to balance.

CliffordH

My Feedback: (9)

Look at a gottegen 398 or I think that is the spelling. It is a rather thick airfoil and looks close to the airfoil on the repo fokker DR1s. I have used it on a plane or two and had good luck with it but then I like large planes with just enough power so you have to fly on the wing and not the engine.

Cliff

BMatthews

A buddy of mine just recently built a scale SPAD 13 and used the scale airfoil. It has a 36 inch span but is very light at 12 oz. The scale airfoil in this case worked just fine. He reports that it has no bad stalling charactaristics at all. It's very much like any other model he's flown.

The airfoil on the plane in the pic looks decent from what I can see but if it uses a super sharp leading edge shape you may want to temper that by rounding it a little. That and as with any scale model of this style keeping the wing loading as light as practical will also help a lot. If you have your doubts about being able to do that then you may want to look at some airfoil options. Luckily there's some nice ones from Dr Mark Drela that are technically glider airfoils but they are thin and are designed to work at low reynolds numbers and operate in a non fussy manner at higher lift coefficients. Just what you need for a scale biplane. Look at the AG03 and AG16 for thin but friendly flying options that would look pretty much scale on such a model.

treedog

Here is some good info on airfoil design. Hope it hels some
http://www.desktopaero.com/appliedae...e/welcome.html

Bad Driver

Gentlemen,
Thank you all for your advice & help!

On an off chance I tried a google search for the designer of the original Ansaldo plans I bought as I think he is a well-known South African scale builder/flyer... amazingly enough I did find an addy and received a reply from him confiming that it was his model! An amazing thing this internet...

So, I have asked him which airfoil he used as this is obviously my best bet from a proven design.

All the best,
B.D.

rmh

FWIW-spend your time on construction techniques and not on looking for a magic airfoil
The fine points of the currves used on th original simply don't matter
select a shape that looks acceptable THEN- find out how to build that shape as light as possible whilst maintaining the strength required
Jeezus - that's the thing the original designers fought!
How to get performance from overly heavy/ poor power output powerplants
th rest of the plane was just a collection of compromises to make it fly.
As a model -- the new electric powerplants really offer you the best possible power source
no vibration to fight (build lighter ) no sudden power losses common to scale builders who are typically not IC engine conversant.
Pick the look you want then look at the materials now on hand to get best weight strength-
There is no correct airfoil which will save the day if you miss the weight / strength envelope.
th designers way back then found the same problems to be true.