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Old Dec 07, 2012, 05:52 PM
Horizon Hobby Employee
United States, IL, Mahomet
Joined Jun 2006
648 Posts
A voice of reason, it had to happen eventually.

The only thing I would add is that in general, moving the CG back will not increase the performance. The model won't glide further or stay up longer. For the vast majority of pilots there is nothing to be gained by approaching neutral stability.

Craig



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Originally Posted by peterlngh View Post
The simple fact ...

...Cheers!
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Old Dec 07, 2012, 07:10 PM
Registered User
Joined Apr 2012
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Thanks, Craig.

My first high performance sailplane, at that early date, was a Mark's Models Windfee. It didn't fly particularly well with an aft CG but it flew so well that i didn't get another sailplane until I built a Sagitta 600. I didn't believe that "newfangled aft CG stuff" so I added about 6 ounces of lead in the nose to get the CG where it "looked right" to my eyes. Then I started taking the lead out, a bit at a time, and was soon to the CG range called for. Wow! I still have the old Sagitta and I'm considering an electric conversion because it's a damned fine sailplane.

Then I got a Hobie Hawk, and she taught me to fly fast, but it didn't have the all around performance of the Sagitta. Now we have designs that allow for spectacular high speed performance and light lift capability, even for sport fliers like myself, and a lot of that is due to designs that are optimized for an aft CG and more neutral stability. I will still continue to start out a little nose heavy and then dial it in through trial and error.
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Old Dec 07, 2012, 07:18 PM
Aka: Ralph
Canada, ON, Hamilton
Joined Nov 2012
315 Posts
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Originally Posted by peterlngh View Post
Hi, dangerdan.

With the bulge on the right side it's not likely to grab the prop since the blade will be moving away from the bulge. That being said, fixing the bulge might be as simple as wrapping the canopy with tape or rubber bands and letting it sit for awhile. If that doesn't work you might be able to shape it with the careful application of heat. Another option would be to coat the inside with fiberglass cloth while holding the canopy in shape.

Cheers!
Thanks for that info..
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Old Dec 07, 2012, 07:22 PM
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You're welcome, dan.
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Old Dec 09, 2012, 12:09 AM
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United States, NM, Rio Rancho
Joined Sep 2010
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Can't wait for the next good flying day.

Well after my adventurous maiden flight. I am ready to get back in the air. I placed velcro on the battery and the battery area. I will not have a repeat lesson in dynamic cg. I did see moments that just amazed me. A little breeze and it is a very stable plane.

The weather is about to change here in New Mexico so we might not have good flying weather for a week or so. Time to clean up my shop and look for something new to build.

Mertz
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Old Dec 09, 2012, 06:50 AM
RCHN #150
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Lawrenceville, GA
Joined Nov 2007
5,997 Posts
I found that Scotch All Weather Fasteners work better than velcro. In fact, in some applications, you do not need a strap. And, the material is gender-neutral. My 2 cents.

http://www.scotchbrand.com/wps/porta...6604127&rt=rud

Rick
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Old Dec 09, 2012, 11:41 AM
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United States, NM, Rio Rancho
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Thanks Rick,
I'll give that a try.

Guy
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Old Dec 14, 2012, 10:07 PM
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Red Bluff CA
Joined Sep 2001
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Well justed picked up a DX18 for the Mystique. The sailplane programming looks straight forward. Now to get flap linages right.
Randall
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Old Dec 16, 2012, 03:55 AM
Airborne whenever I can.
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Canada, AB, Edson
Joined Dec 2006
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Quote:
Originally Posted by dangerdan View Post
Also be sure to visit the Novice Lounge of the Eastern Soaring League
http://www.flyesl.org/forums/forum.asp?FORUM_ID=14

I read the thread on Gordy's Sailplane Balancing System.

That was very informative and I actually understood that.
Great, Thanks for that link my friend. I found Skybench and ordered a 2mE Lil Bird, I was looking for a good E-version of the Bird Of Time for a long time. gonna be fun to get that one together. Sorry for the off topic! Thanks

PAT
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Old Dec 18, 2012, 12:13 AM
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Thornleigh - 20k N of Sydney,N.S.W.,AUSTRALIA
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Suggestion

Quote:
Originally Posted by peterlngh View Post
The simple fact is that different fliers demand different things from their planes. A person flying a Radian for their first flight ever demands an entirely different performance envelope than someone flying a Pulsar in a local ALES event. And neither of those will necessarily correspond to a regional, national, or world thermal duration event or an advanced LSF task.

A beginner needs a plane with positive stability so that they can learn the special kind of hand/eye coordination it takes to fly a model. They might also have to compensate for rookie mistakes in setting up their controls and incidences. These problems are easier to overcome if one has experienced fliers to help one out but a great many people, like those who live in rural areas, don't have that resource readily available.

In the most general of terms: a sailplane set up with the CG towards the front of the recommended range will be easier for an inexperienced pilot to fly. A forward CG will also result in a predictable combination of attributes for experienced pilots flying a new plane. Think of it as an error on the side of caution. It might come as a shock to learn that some manufacturers get the whole CG range wrong. It happens but setting up at the front of the recommended range will almost always prevent one from running into a problem like Mertz had when his battery shifted back. This approach, of beginning with a forward CG and gradually moving weight back until the desired performance has been achieved, is a time honored approach among almost every pilot I've ever met.

Many of the pilots getting this sailplane are making a significant step up in size, performance, and complexity. Those are three very important variables. One of the things that one can do to reduce the learning curve is to set up the initial CG to, hopefully, give rather benign handling for the learning period. Then, as one learns the habits of the plane, one will then adjust the CG to give optimum performance and that optimum performance will differ between pilots and whatever task they wish to perform.

Cheers!
All good info ... but here's suggestion ... for any sailplane.
On the assumption that the sailplane has been built/assembled straight and true, exactly as designed, check out, and then download and use SailplaneCalc.
If you can use a measuring stick, and can work out areas, and tail moment distances etc. this very easy to use program will give you a good starting point for your CofG (Longitudinal Balance Point) - if you use a Static Margin of around 10%, you can always move the CofG back futher from that reasonably safe position after a first flight, to give you a more lively performance, but the CofG should always be forward of the aircraft's Neutral Point.
Daffy.
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Old Dec 18, 2012, 01:00 PM
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Originally Posted by hhrnd40 View Post
On my Mystique I run the servo arm down (through the provided slot) and the linkage internally. I get the clearance by relieving a bit of the trailing edge spar to allow the linkage to clear and give me the required flap travel. Once I get the clearance I need I wick in thin CA to reinforce the balsa. I also made a slight bend in the linkage to help clearance as well. I do the same thing on 2K molded ships and trust me, there is no lose of structural integrity.

Also see my post #98 for other photos on my Mystique build.

Thanks,
JD
I'm seriously considering the purchase of a Mystique. I'm a little concerned about the flap linkages, however. Question: I'm wondering why I couldn't relocate the control horn from the top of the flap to the bottom, thus hooking it up in a more conventional, straight forward manner? I mean, why did E-Flite locate the control on top? I see no advantage.

Beyond that, it appears that the Mystique would be a good next-step glider for me. Currently, I'm flying a 41-year old Monterey (rudder, elevator only) and a foam Blaze. Neither one has flaps, which is something I really want on my next glider.

KillerChaos
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Old Dec 19, 2012, 03:15 PM
Joined Jan 2007
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Originally Posted by KillerChaos View Post
I'm seriously considering the purchase of a Mystique. I'm a little concerned about the flap linkages, however. Question: I'm wondering why I couldn't relocate the control horn from the top of the flap to the bottom, thus hooking it up in a more conventional, straight forward manner? I mean, why did E-Flite locate the control on top? I see no advantage.

Beyond that, it appears that the Mystique would be a good next-step glider for me. Currently, I'm flying a 41-year old Monterey (rudder, elevator only) and a foam Blaze. Neither one has flaps, which is something I really want on my next glider.

KillerChaos
The flap horn is on the top for better mechanical advantage, most TD type designs have top mounted flap horns when bottom hinged for this reason, the further you put the connection point from the hinge line, the more stable the linkage is, bottom mounted flap horns would drastically reduce mechanical advantage plus increase the chance of landing damage if the linkage gets caught up in the grass.. Flaps are also bottom hinged for efficient travel as 90% of their travel requirement is in the down direction.
I would refer to JD's post earlier in this thread for flap installation, this may help you through the installation process a little better..
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Old Dec 19, 2012, 03:54 PM
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United States, TN, Johnson City
Joined Jul 2011
188 Posts
Got my Mystique a couple of days ago and am going thru the wing servo linkage woes. I have re-read posts about how others have approached this, but most of the detail is missing I would appreciate some answers to these questions from some of you who have been successful in getting this done.
- Is cutting a relief in the trailing edge like mertz has done, the best way to go?
- Did you use the recommended servo control horn hole and length?
- Were you able to get the suggested suface throws?

I am working on the ailerons first, but the bend I used to get the minimum binding seems to eliminate any possibility of getting the correct surface throw. I get about half of what is needed, even though the servo horn is moving its full travel. This has me thinking i need to have the control rod pretty straight, which is leading me toward the trailing edge work.
Thanks for any advice!!
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Old Dec 19, 2012, 06:30 PM
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USA, CA, Chico
Joined Feb 2011
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So what's the consensus about this plane guys??? I've been sittin on the fence about getting it. Is it truely ALES capable?? I've been out of sailplanes for a few years, got into small foamy electrics a couple years ago, but I sorta long for an easy to put together but decent performing e Sailplane. What do guys think of this one in terms of all around performance and durability, and ease of construction??
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Old Dec 19, 2012, 07:31 PM
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Quote:
Originally Posted by TeamHorizon View Post
The flap horn is on the top for better mechanical advantage, most TD type designs have top mounted flap horns when bottom hinged for this reason, the further you put the connection point from the hinge line, the more stable the linkage is, bottom mounted flap horns would drastically reduce mechanical advantage plus increase the chance of landing damage if the linkage gets caught up in the grass.. Flaps are also bottom hinged for efficient travel as 90% of their travel requirement is in the down direction.
I would refer to JD's post earlier in this thread for flap installation, this may help you through the installation process a little better..
Thanks, that makes sense. I couldn't tell from photos just how the flap was hinged. Meanwhile, still thinking on the matter, I'm wondering if perhaps mounting the flaps servos from the top might provide the direct (straight) linkage some of us are looking for. I guess I won't know how much I'm chewing on until the glider arrives, but maybe...

Thanks again,

KillerChaos
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