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Re: Elastic Launched Glider C

Posted: January 29th, 2014, 1:18 pm
by AtRi
While I do stand corrected in that adding/subtracting ballast should be the primary change when balancing the glider, I disagree that the glider should always be at 0-0 incidence. I always add a little bit of negative incidence to my gliders and I have had great success. I find it to be more of a balancing act between adding/removing ballast and adding/removing incidence, rather than strictly one or the other.
Interesting! It's really cool how filght characteristics are so different for each glider and design. Negative incidence usually causes my glider to do a hard crash at the transition. I actually build a bit of positive incidence before trimming to avoid breaking my glider on the first flight
Adding ballast definitely has an enormous impact on the glider
I actually meant that I add positive incidence, like you. My mistake.

Re: Elastic Launched Glider C

Posted: February 3rd, 2014, 8:26 pm
by wiseowl63
In regards to the "bubble" glider design. Has anybody ever heard of this glider and does anyone know where to find the schematics for it. Also what classifies a glider as canard.

Re: Elastic Launched Glider C

Posted: February 3rd, 2014, 9:34 pm
by erikb
In regards to the "bubble" glider design. Has anybody ever heard of this glider and does anyone know where to find the schematics for it. Also what classifies a glider as canard.
From the soinc.org FAQ:
"01/01/2014 - 20:38 What are the exact specifications needed for a glider to be considered a Canard Configuration?
There are two horizontal aerodynamic surfaces in elastic launch gliders. The larger surface is the primary source of lift and is considered the "wing." The smaller is a stabilization source and is considered the "horizontal stabilizer." Canard configurations place the horizontal stabilizer in front of the wing (reverse that of traditional layouts.) No aerodynamic surfaces may be behind the main wing."

As for the bubble glider I have no idea.

Re: Elastic Launched Glider C

Posted: February 4th, 2014, 5:45 pm
by baker
In regards to the "bubble" glider design. Has anybody ever heard of this glider and does anyone know where to find the schematics for it. Also what classifies a glider as canard.
I'm sorry, it was me that started the "bubble" thing. I think the team I asked what design it was, gave me a bum steer. But after some research I think they may have had a Chuck Marko's Scholastic Glider design or a derivative of it. The wing looks like what I saw and the fuselage was long, longer than FreedomFlight's.
http://www.youtube.com/watch?v=6Dl4U2DHKQQ

Re: Elastic Launched Glider C

Posted: February 5th, 2014, 8:23 pm
by fanjiatian
Would carbon tape work just as we'll as tow for the fuselage?
In what direction is the carbon supposed to be aligned for the fuselage?

http://www.amazon.com/EPISIZE-CARBON-FI ... B002IZJ8FI

Re: Elastic Launched Glider C

Posted: February 5th, 2014, 8:37 pm
by goswal
How is everyone doing with canard gliders, now that regional competitions are mostly over? My team is having success with the glide itself, but we're experiencing some instability immediately after the transition. It seems that our canard gliders have a much smaller "sweet spot," and require a near-perfect launch angle and bank for a proper transition. When we do get this transition, the glider will often begin a controlled but rapid descent, as if its angle of incidence were too negative. This happens even when the angle of incidence is slightly positive. We think this may be due in part to the ratio of the SAs of the wings and canard, but we're not sure.

Also, has anyone experienced significant launch differences based on different positions of the launch hook?

Re: Elastic Launched Glider C

Posted: February 6th, 2014, 10:05 am
by chalker
...... now that regional competitions are mostly over?
FYI... I'd estimate that the vast majority of regional competitions have NOT been held yet. Most regionals are in Feb / March.

Re: Elastic Launched Glider C

Posted: February 6th, 2014, 10:42 pm
by erikb
It seems that our canard gliders have a much smaller "sweet spot," and require a near-perfect launch angle and bank for a proper transition....Also, has anyone experienced significant launch differences based on different positions of the launch hook?
Canards are inherently longitudinally unstable. The Neutral point and the center of gravity are not the same as the "standard" configuration. So changes in the canard are far more sensitive then changes in a tail on the standard configuration. Thus, less forgiving.

That being said, moving the wing along the fuselage to bring the Neutral point closer to the center of gravity will reduce the instability but not eliminate it. However, a less forgiving launch and transition can be achieved.

Re: Elastic Launched Glider C

Posted: February 7th, 2014, 5:52 am
by AtRi
Has anyone had an luck in getting similar performance out of a canard glider compared to a standard glider? I have gotten canard gliders to transition and fly decently, but they don't begin to compare to my other gilders even with the bonus.

Re: Elastic Launched Glider C

Posted: February 7th, 2014, 10:19 am
by bjt4888
Reply to Goswal,
See the Canard Design Calculator link I posted in a message on page 3 of this forum. If the center of gravity of your glider is properly located relative to the neutral point (do you have enough clay on the nose and not too much), your issue is probably inadequate positive foreplane incidence. I have found that almost 3 degrees is needed for my canard design, which has a smallish undercambered foreplane. This is quite a bit more than the typical decalage angle of 0.5 degrees I have found typical of a non-flapper style low-ceiling conventional glider.
As I noted in my previous Canard post on this forum, my best flights with this glider are about 19.5 seconds for a launch height of about 24 ft. I believe that once an issue with foreplane mount flexing is solved, the design may be capable of better flights. I would encourage students to continue testing and researching the Canard design, there is potential, but I cannot share more as this is to be a student design exercise.

BJT4888