Elastic Launched Gliders B

[Maxout]

Jdh3


2) When you launch it horizontally with low power and no bank, it climbs linearly for 2 feet and then tries to transition right into a glider, but the right wing tips downwards, bringing the whole plane down.

This is a wing warp problem. Grab the right wing about 1" out from the fuselage and twist the part ahead of the flap so that the leading edge is raised relative to the trailing edge. Don't touch the flaps at all. If the wood cracks, that's fine, just harden it with ca glue. This should fix the problem, although you may find a need for more right rudder trim.

[Jdh3]

Jdh3


2) When you launch it horizontally with low power and no bank, it climbs linearly for 2 feet and then tries to transition right into a glider, but the right wing tips downwards, bringing the whole plane down.

This is a wing warp problem. Grab the right wing about 1" out from the fuselage and twist the part ahead of the flap so that the leading edge is raised relative to the trailing edge. Don't touch the flaps at all. If the wood cracks, that's fine, just harden it with ca glue. This should fix the problem, although you may find a need for more right rudder trim.

I agree.
You can often see the problem when you look at wings from the front. The problem wing (right in this case) will not be catching as much air and therefore not getting enough lift. The opposite wing will continue to get lift until it rolls over the airplane into the ground.

[AirplaneMan]

I tried increasing the incidence a lot and I had to also add more clay to compensate for that. But this same situation seems to occur. The glider goes up and then immediately flies towards the ground. What I mean by that is that the glider goes up, then after reaching its maximum height, it slightly turns to the left and flies downwards at a 45 degree angle. It doesn't dive at a 90 degree angle; it's almost as if it's a glide, but the glider loses altitude very quickly and hits the ground.

Airplaneman-
Gliders are tougher to trim then Wright Stuff. See my list below-

If the glider ROLLS Left, points its nose down, then the left (Port) wing needs more positive incidence. That is, the leading edge needs to be higher than the right (Starboard) wing.

1) Technique #1, Turn model upside down and bend the port wing's leading edge up a couple of degrees. It the wing cracks, drop some CA in the crack.

2) Technique #2, crack the port wing's wing root at the leading edge and lift it a degree and glue in place.

3) If the glider enters transition, note if the orbit is left or right. I suspect a left hand orbit. If the glider is stalling, add clay to reduce the stall.

4) If the glider has a slight diving flight, remove some clay.

Report on these changes and I can offer more suggestions.

Regards,
50 Missions

Thanks for the tips!
But the wing has carbon fiber glued on so wouldn't cracking the wing mess that up?
Plus I'm a little hesitant to break the wing that I spent so long making... Isn't there anything else that I could do?
Anyway, I increased the incidence by a pretty good amount (~1 degree) and I also increased the weight on the nose, and the same situation seems to persist, but it isn't as bad. Before, the glider would be flying downward (as stated in the posts above) but now, this only happens for the beginning of the flight. For example, I launched the glider to about 20-25 feet and in the first 8-10 feet the glider was still flying downward. Then, it leveled out and began gliding like normal. How can I stop the glider from doing this? I'm losing all that altitude because of that fast downward glide in the beginning and that is giving me lower times (~10-15 second flights)

[fifty_missions]

I'm thinking there may be a mass issue. If your glider weighs over 4 grams, it is consuming too much energy to fly. A good analogy is take a 5 mile hike with loose change and a bottle of water. Take the same hike a week later... loose change, a bottle of water and a 100 pound knapsack. Which of the two hikes did consume more energy to get the job done? Heavy aircraft struggle to fly when overloaded. The cannot maneuver for the same reason. Transitioning is directly related to the wing loading. Small wing area and heavy construction and you just built an arrow. What you want is a design that can maneuver from the vertical to horizontal. That ability will be correspondent to the weight and wing area.

1) Josh is correct, the one wing that drops needs to have its leading edge up even higher. Cracking the leading edge and setting with CA is a very common fix. 30% of my own gliders (30+) have had this fix.

2) Same fix may help the transition to happen higher near the ceiling.

3) It is a bit sketchy when you say a launch at 20'-25'? Is that VERTICAL (90 degrees), 45 degrees, or almost horizontal?

4) Did you try to either reduce the nose mass or bend the trailing edge of the stabilizer up? Either would help bring the nose up to transition as the glider slows down at the apex of the launch trajectory.

5) If the glider has a severe roll to the right on launch, bank with the left wing tip lower than the right on the launch (banked left).

6) As I tell my students, build at least 5 gliders and one might be a winner. You may need to go back a build another. Get symmetric and use less glue.

One of these days we need to publish common terms with images for describing flight patterns. I believe many descriptions are being garbled by semantics.

Report back,
50 Missions

[AirplaneMan]

My glider was originally 3.7 grams, but after the repairs I made throughout the testing process, the glider probably weighs around 4.0 grams now.

1) Ok I'll try that but how do I crack the wing? I'm using a flapper FF design so there's carbon fiber on the wing. Cracking the leading edge won't also break the carbon fiber, will it?

3) That's a launch to about 20-25 feet vertically (20-25 feet straight above the floor)

Also, does rudder deflection have an impact on the transition? And if it does, what is the effect of increased/decreased rudder deflection? I'm wondering because I have a very wide turn circle right now, and when I slightly bend the rudder to get a smaller circle, the plane seems to become less stable in the flight.

[fifty_missions]

1) Ok I'll try that but how do I crack the wing? I'm using a flapper FF design so there's carbon fiber on the wing. Cracking the leading edge won't also break the carbon fiber, will it?

It more like break the wing. It is best spot is right at the root where the two wings join. We are talking about 5mm deep and maybe 2mm up. Forefinger tops and thumb bottom side at that location. Break the wood slightly to raise the leading edge up about 2 mm. Don't try to measure that. Just eyeball it and real the wood audibly give to the force. Use medium viscosity CA glue or DUCO to hold that change.The idea is for the leading edge, preferably the length, to be just degrees higher on that wing that is not creating enough lift. The opposite wing gets no changes (at this point). This should not interfere with your carbon fibre.

There are no awards for a Glamourous Glider! What wins is pure functionality.
Report Back,
50 Missions

[AirplaneMan]

Ok I'll do that. Just wondering, would decreasing the flap deflection on the right wing achieve the same result?
Also, what is a good amount of flap deflection for a flapper glider? Right now I have about 3/16 inches of deflection. Is that too much?

[fifty_missions]

Ok I'll do that. Just wondering, would decreasing the flap deflection on the right wing achieve the same result?

No on the deflection. That is a lot of area to change and makes the glider super asymmetric. Both flaps should be equal. That said, there is some suspicion that one flap is flexing more at launch and/or is significantly lighter than the other wing. this would induce a roll.

Let me define roll.... hold the glider at the nose and the tail. That becomes one axis. Rotate the glider on this axis with the wings spinning around the the fuselage like a top. THAT is the ROLL Axis. NOSE UP or NOSE Down is the PITCH Axis (either as stalling or diving). YAW is from the axis as if a pin went through the top center of the wing and through the fuselage. Rotate the glider on that axis and it is YAW. If the glider orbits in a full circle, it was affected by the YAW AXIS. Most glider turns are a combination of all three axis in coordination. Most SO gliders orbit with a active combo of roll and yaw with a few flying with a noticeable bank with one wing flying lower than the opposite, tip to tip. Such a glider has a Roll tendency.

Once we get your transition, then we move onto a stable orbit procedure.

More Reports,
50 Missions

[builderguy135]

How would flap deflection be affected if my chord changed from 3" to 3 .75" ?

[fifty_missions]

How would flap deflection be affected if my chord changed from 3" to 3 .75" ?

. Keep the trailing edge limit about the same as where it is now. More area means more lift. Added deflection means substantially more drag. This might be okay for a 20' ceiling where a BUNT launch is best but for the most part, a glider needs to get up to 30' to transition.

Other concerns... Flutter- too much flap area may induce flutter which is high drag and damaging to the flap area.

.... Too low on the trailing edge of the flap could mean dragging across the floor on landings. Depending on the surface this could fracture the edge or just collect gunk that is hard to remove.

..... mass changes. The larger area may mean one wing gets heavier and causes a corkscrew on launch. Sometimes that is okay to bleed off speed before transition but many times causes hard to correct tendencies.

But, like my Dad always said, you don't know until you try.

Good Luck,
50 Missions