All,

Due to some accumulated damage, I am considering rewinging my LT-40. Some of the guys at the club recommended going with a flat wing (no dihedral).

Is there a good description of wings somewhere? I know there are symetrical and flat bottomed, but am not sure exactly what the difference is.

I'd like for the LT-40 to be more "sporty" and hold my interest longer, without become to unstable for a novice (approaching 10 solo flights).

Any help or suggestions would be appreciated.

GB

The dihedral is the angle between the two wings as seen from the front or rear.

reducing the dihedral will reduce roll stability, and will also reduce rudder-roll coupling. (rudder turns will be more flat)

With planes such as the LT-40, you can safely reduce the dihedral to where the wing is flat, just be aware that the plane may need opposite aileron to prevent the bank from getting steeper on its own after you center the ailerons. You really shouldn't see a huge difference.

You gain more aerobatic capabilty by changing to a semi-symetrical or symetrical airfoil... but that would mean carving the wing saddle area of the fuselage, and its too easy to do that wrong. Just flattening the wing... I doubt you'll have any problems.

fhhuber hit the nail on the head again, but I've got a few things to add.

To make the LT-40 more sporty while still having the flat bottom wing, I'd enlarge the control surfaces by 25% to 33%, and I'd remove 1 rib bay from each side of the wing. You could probably get away with 2 rib bays being removed, but that might be too much, too fast for a novice. I would also have a 40 or 46 FX engine on it, or something simmilar.

Thanks for all the advice,

I am not yet bored with the LT-40, and I was thinking that it would be nice to be able to switch wings and make it more sporty and switch back to let it be used as the club trainer (next year).

So, if I modify the flight controls, how would that affect the old wing?

Also, where would you find instructions on how to build flight control surfaces? I think I have the tools to do almost anything, but I assume they are more than just flat panels of balsa. Or are they? Or perhaps someone sells a kit with them?

THanks again,

GB

The ailerons on the LT-40 are most likely tapered solid balsa stock, appx 1/4 inch at the front and 1/16 at the rear.

You can buy this material in several widths, from 1 inch to over 2 inches, in 3-foot lengths. The front endg is then double-beveled to allow free movement in the hinge line with minimal gap between the control surface and the wing.

The tailplane control surfaces are commonly made from flat sheet balsa, sometimes with holes cut out to reduce weight. Sometimes they are built up of an outer frame of appx 1/4 X 3/8 stock and 1/4 X 1/8 "ribs". Tapered stock as with the ailerons can also be used.

It is also possible to make the control surfaces changeable... Use Pinned type plastic hinges, replace the pins for any given control surface with one long piece of music wire, bent at one end and the bend trapped by tape. (needs periodic inspection) Pull the wire, the control surface falls off, ready to be replaced with another that has had matching hinges installed. (of course.. unclip the clevices on the tailplanes... and the ailerons need brass tube "liners" epoxied in the holes for the torque-rods. (easier to do the tailplanes than the ailerons...)