Tappered leading edges

I have question for the stunt world whats better tappered leading edges are straight leading edges. does the planes fly different are is it just the look?????

My understanding is that the swept LE offers improved yaw stability.

Overall tapering of the wing is a result of establishing proper lift distribution.

Experts will probably check in on this one however.

FWIW

It depends on what you want to use the airplane for. As far as I know, all of the current top level PA airplanes have a swept LE, so if your are at that top level of competition, that is what is winning. There are, however, some airplane with a streight LE that fly very well. The Oriental and Magician are two that come to mind.

John Quigley

Hello All

Model design is a very interesting passtime and so much room for creativity. I like to fly CL models and have also designed many RC aerobatic models that were successfull. Also Gliders for those interested I have one contest to go for LSF4

Tapering the LE does give yaw stability if done correctly.

It is the hi point of the wing section that is importantif the percentage thickness is also held constant ie max camber.

If the hi point is fixed and the le is cut short to produce taper then the only gain is looks. This was done in some much older plans.

There is some good software to produce wing sections today.

Some I am playing with (as none of them are complete in them selves) is POFILI (from Italia and costs about $15US) this one prints a set of ribs including sheeting.

Simply define the root chord and the tip chord and the number of ribs and presto a printout ready to go.

Compufoil is OK but only produces foam templates for a cutting machine that they produce. This on takes into account the loss by the hot wire. Very good idea.

I once built two similiar RC aerobatic models with tapered wings. One with a straight TE and the other with a straight HI point. The straight HI point was great in rolls in calm weather and the straight TE was great in windy weather.

SO the software that is now available for PC's, playing with wing sections can be very rewarding if the HI point is tapered.

Most of these software packages instantly display the shape and no longer does one need to draw every shape or visulise the shape frm the numbers.

It is easy to see the shapes on the NACA numbering system but todays system of cordinates by Eppler or Whortman need a stronger mixture than coffee.

SOme of the latest sections have a concave back, like the kitted Palmer Chief but not as prenounced, which may be useful for stunters using flaps.

Bob Palmer was an advocate for using NACA wing sections on his models. The NACA 00XX is similiar to the SAFTG that was popular in the late 40's and early 50's on some of the better layed out US designs.

Using some of the techniques that are used on todays RC gliders where there is almost gapless flap hinging, could be used on stunters to keep the wing section shape.

The flaps on these RC gliders move approx +5 to -80 deg.

There is a model gliding home page that has a saying "TWITH" The wing is the thing. While it si devoted to RC flying wings the message that the wing is important is a good lesson.

When I went from nice curves for wing sections to corrrectly designed wing sections I gained a signifficant improvment in model performance.

Seelig is an American aerodynamisists who has done much for RC gliding. With some financial assistance form the stunt following it would be interesting to determine if a gain could be obtained for stunt.

Much like what al raby did way back poking his head out of a car with wing sections and measuring lift.

May all this has been done and I have not caught up.

This is the best site for modelling that I visit.

John Q