Elastic Launched Glider B

[builderguy135]

Do you guys have any tips to build a symmetrical wing? Sometimes I'm having trouble with making both wings have the same amount of lift. A little might be a good thing, but sometimes I end up with planes dive bombing duing transition. Thanks!

What wing design are you using?

[NewSciolyer]

This might sound kinda weird, but I'm not using any kits. I have some old free flights kits from the 20th century that had missing pieces so I couldn't build it like it was meant to be built (Keil Kraft, that kinda of stuff). I ended just using the wooden pieces since laser cut didn't exist back then and there were only markers marking where you need to cut, so it was still one whole piece of wood. I think maybe part of the reason why is that the wood is so old and warped? Maybe it's just me not paying attention.

[bjt4888]

Newscioly,

A number of design and launch elements affect transition and wing symmetry is not high on the list. As long as the wings are reasonably close to the same shape, airfoil and weight, they will perform fine.

Design elements that help transition are: correct incidence (determined by flight character and not “zero-zero”; adjustable incidence built into the design is very helpful), no incorrect warps in flying surfaces, built to minimum weight (or close to minimum), correct fin height relative to wing dihedral (allows the correct amount of yaw instability for the desirable “Dutch roll” transition), correct tail moment arm length, correct center of gravity location, very stiff and light wood for the stabilizer and fin, stiff and light fuselage (judiciously placed carbon helps). Also, stabilizer area doesn’t need to be more than 15% of wing area. Our best flapper design uses 13.5%. All of these elements are present in gliders from the top designers (Gowen, Buddenbohm, Krempertz, etc.).

Launch elements that must be correct for a good transition are bank angle and inclination angle. These angles may be different for each copy of any particular glider.

I would recommend you build a proven design, using appropriate density and stiffness wood and carbon if needed, and spend as much time as possible practicing in the gym.

Read my past posts regarding trimming.

Brian T

[builderguy135]

This might sound kinda weird, but I'm not using any kits. I have some old free flights kits from the 20th century that had missing pieces so I couldn't build it like it was meant to be built (Keil Kraft, that kinda of stuff). I ended just using the wooden pieces since laser cut didn't exist back then and there were only markers marking where you need to cut, so it was still one whole piece of wood. I think maybe part of the reason why is that the wood is so old and warped? Maybe it's just me not paying attention.

I would suggest sanding evenly on each side then. Hold the wing up to a light to estimate the thickness, or just use a caliper. Make sure the high point line is similar for each side (use pen to physically draw it).

If you're having trouble keeping the wing shape symmetrical, draw one side of the wing on a sheet of paper and trace it onto the wood.

The wood might be warped if you sand on both sides. Don't do that, it warps the wood.

But yeah, listen to what Mr. Turnbull said. It's probably not the wing problem. If it's nose diving, then adjust the bank angle to see what works best.

[NewSciolyer]

Thanks for replying! I think it does have something to do with the wings because I tried switching it with two different fuselage and the plane still curves too much to the right. Unless I'm just a really bad builder and made the exact same mistake on both of them, or I think one side of the wing is catching a bit more air Since I'm on a budget and just to experiment, I cut the shape of the flaps off of foamboard and then sliced the foamboard in half so one side is paper and one side of foam. After that, I crushed the foam to make it more thinner to attach to the wood. The cut I made to split the foam wasn't very straight and one half of wing had more foam than the other.

Thanks!

[builderguy135]

Thanks for replying! I think it does have something to do with the wings because I tried switching it with two different fuselage and the plane still curves too much to the right. Unless I'm just a really bad builder and made the exact same mistake on both of them, or I think one side of the wing is catching a bit more air Since I'm on a budget and just to experiment, I cut the shape of the flaps off of foamboard and then sliced the foamboard in half so one side is paper and one side of foam. After that, I crushed the foam to make it more thinner to attach to the wood. The cut I made to split the foam wasn't very straight and one half of wing had more foam than the other.

Thanks!

The curve to the right is definitely from the stabilizers. If it's spiraling towards the ground, add more area to the vertical stabilizer. If it's turning in too tight of a circle, adjust a combination of the vertical and horizontal stabilizer tilt.

(Correct me if I'm wrong please!)

[bernard]

A diagram for Elastic Launched Glider has been posted to the national website.

[bjt4888]

Newsciolyer,

From the description of the use of foam on your glider, it sounds like you are trying a custom design. If this is true, my advice to you is to build a simple and proven design. A proven design, built of appropriate density wood, and built light will be much more likely to give good results quickly.

My favorite simple design is Stan Buddenbohms Littl Sweep SO. He doesn't kit this any more, but you could buy a plan from him for a very reasonable price ($1 last I knew). Also Kurt Krempertz website AMAGlider has a video build of this design. Appropriate density wood fir this design should produce these part weights: wing 1.5g, Stab .28g, Fin .08g, Pylon .1g, Nosehook .1g, and Fuselage .9g. Nose ballast will add another .35g for a total of 3.3g. A little overweight, but capable of 20 seconds launched to 22 ft. Part weights and wood quality are critical.

Or, spend a little $ for the J&H Aero or Freedom Flight kit.

BrianT

[bxt72]

I'm pretty new to this, but I think the J&Hs have been absolutely phenomenal. Definitely worth the money.

[bjt4888]

Bxt,

The Freedom Flight kit is also excellent. Won a very competitive Michigan States last year.

Brian T