Page 5 of 14

Re: Elastic Launched Glider B

Posted: January 13th, 2015, 4:31 pm
by bjt4888
torqueburner,

Congrats on building the Stan Buddenbohm Litt'l Sweep glider. The high schools that I have coached for the last couple of years also used this glider as their initial experience and got excellent results with it. I have built a few of these myself for testing purposes and all have trimmed out in a few flights and all flew great. I agree that this glider gives very good performance and does not take much time to build. The students I coached did not have any issue with launch handle strikes, but one test glider that i constructed with minimal decalage did occasionally have this problem. There are a couple of reasons that the students may be getting strikes against the launch handle.

It is possible that there is a small gap in the front hook to fuselage joint that the rubberband is getting wedged in. I had the students be sure that this joint was tight and had them put a small drop of glue in the vee formed by the front hook and fuselage joint where the launch rubber seats.

Were the students careful to orient the fuselage per Stan's marking for the top? If not, the glider may have inadequate decalage which would cause it's initial flight path during launch to bee too straight causing it to get caught in the rubber loop and/or hit the launch handle. The amount of decalage that Stan designed for the glider is approximately 0.5 degrees (all in negative stab incidence) which should cause the glider to start sweeping away from the launch handle immediately upon release, preventing strikes.

If you could describe the students exact launch procedure (angle of inclination, angle of bank, and amount of stretch) and the character of the flight during launch and transition, I may be able to be more help.

I posted a number of narratives last year on the Hip Pocket Aeronautics forum that describe launching and trimming SO gliders that might be helpful too.

Brian T.

Re: Elastic Launched Glider B

Posted: January 15th, 2015, 8:57 am
by SOCoach
By transition time / zone I am referring to the point at which the plane shifts from a vertical launch to a horizontal glide. Sometimes it goes up and has very little fall and goes right into the glide. Other times it falls nearly half its initial height and then begins its glide. We can't seem to find the variable that controls / affects this.

Re: Elastic Launched Glider B

Posted: January 15th, 2015, 9:01 am
by bernard
SOCoach wrote:By transition time / zone I am referring to the point at which the plane shifts from a vertical launch to a horizontal glide. Sometimes it goes up and has very little fall and goes right into the glide. Other times it falls nearly half its initial height and then begins its glide. We can't seem to find the variable that controls / affects this.
Here's a video that mentions what you are describe. Hopefully it is helpful. If not, let me know and I'll see what other suggestions I have.

Re: Elastic Launched Glider B

Posted: January 15th, 2015, 11:02 am
by torqueburner
bjt4888 wrote:torqueburner,

. . .Were the students careful to orient the fuselage per Stan's marking for the top? . . . If you could describe the students exact launch procedure (angle of inclination, angle of bank, and amount of stretch) and the character of the flight during launch and transition, I may be able to be more help.

Brian T.
Thanks Brian. I'll check whether they got the fuse the right way. They were clearly marked "top" as I recall, so I hope they did! The glider flies so nicely when they don't hit the launcher, so I'm guessing that isn't it, but you never know. . .

I also emailed Stan, and he said that he never had that problem when gripping the glider at the very end of the fuse behind the stab, but sometimes when gripping below the wing, which is what our guys have been doing (they watched the video of Bill Gowens very nice launch of his Big Poker). So we will try switching to the end grip first, will let you know if that doesn't fix the problem.

Dave D.

Re: Elastic Launched Glider B

Posted: January 15th, 2015, 5:44 pm
by wlsguy
SOCoach wrote:By transition time / zone I am referring to the point at which the plane shifts from a vertical launch to a horizontal glide. Sometimes it goes up and has very little fall and goes right into the glide. Other times it falls nearly half its initial height and then begins its glide. We can't seem to find the variable that controls / affects this.
It is likely your students are not controlling the 3 key launch variables. These are the pullback distance (to control the power), the tilt up and down (to adjust how steep the launch angle is), and the tilt left to right (to adjust when the glider goes into the glide).
Obviously this is simplified but the 3 launch variables are the same.

Try getting video of your good and bad launches and see if you can see the difference.

Re: Elastic Launched Glider B

Posted: January 23rd, 2015, 8:23 am
by Modeldad
I asked this question on SOINC rules clarification, but have not received a response. The rules state that ballast MAY be any malleable non-metallic substance. We are using a glob of epoxy on the nose of our glider for ballast. The reason being it doesn't dry out like clay and does not deform on impact. Is this legal? My interpretation is that glue is allowed for construction, and I just used a bunch of glue to hold the hook on the nose, and now I don't need additional ballast!

Thanks.

Re: Elastic Launched Glider B

Posted: January 25th, 2015, 3:03 pm
by wlsguy
My unofficial opinion. Since it is glue it, it should be legal.
My next question is, is it safe?
Obviously you don't want a hard, metal like, lump at the end of something being launched around the room. I think this was the intent of the requirements.

Re: Elastic Launched Glider B

Posted: January 25th, 2015, 4:33 pm
by Skink
I just wanted to share that I got hit in the head with one of these things yesterday at a competition outside the demarcated event area. It was the most chance occurrence ever because I was a moving target...it was amusing for the people who saw it!

Re: Elastic Launched Glider B

Posted: January 27th, 2015, 8:03 am
by Modeldad
Since there is no requirement for the clay ballast to be on the front of the glider (e.g., covering the nose), I'm not sure if safety was the reason for it. The lip balm cap specification prevents sharp noses. My opinion for not allowing metallic ballast is to avoid teams using lead (hazardous substance). Any one have any experience with this in the past?

Re: Elastic Launched Glider B

Posted: January 27th, 2015, 12:44 pm
by dragonmaster57
Does anybody have any good links for Elastic Launched Glider?