Advice on "EZ Trim" Glider

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tooth

tooth

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Is there such a thing, lol. After 6 flights I finally got my Hawk to level out and soar for 43 seconds, completing that requirement for the NARTREK certification program. It was rewarding and frustrating at the same time. I readily admit despite reading and watching a few videos on the trim process, I’m terrible at it.

My wife is also doing the cert program with me, and she’s ready to start her glider. But she’s looking for a glider kit that is easier to trim than the Hawk. She’s an excellent craftsperson and her builds often look better than mine, so the construction component isn’t an issue.

Any of you have experience with a glider kit that seemed to be a relatively easy trim? We both thank you in advance for any recommendations.
 
tooth said:
View attachment 592395
Is there such a thing, lol. After 6 flights I finally got my Hawk to level out and soar for 43 seconds, completing that requirement for the NARTREK certification program. It was rewarding and frustrating at the same time. I readily admit despite reading and watching a few videos on the trim process, I’m terrible at it.

My wife is also doing the cert program with me, and she’s ready to start her glider. But she’s looking for a glider kit that is easier to trim than the Hawk. She’s an excellent craftsperson and her builds often look better than mine, so the construction component isn’t an issue.

Any of you have experience with a glider kit that seemed to be a relatively easy trim? We both thank you in advance for any recommendations.
Click to expand...
B/g's can be tricky because you need both glide and boost trim. A pop pod glider design will have a large c.g. shift between boost and glide, making trimming much easier.
 
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tooth said:
Is there such a thing, lol. After 6 flights I finally got my Hawk to level out and soar for 43 seconds, completing that requirement for the NARTREK certification program. It was rewarding and frustrating at the same time. I readily admit despite reading and watching a few videos on the trim process, I’m terrible at it.

My wife is also doing the cert program with me, and she’s ready to start her glider. But she’s looking for a glider kit that is easier to trim than the Hawk. She’s an excellent craftsperson and her builds often look better than mine, so the construction component isn’t an issue.

Any of you have experience with a glider kit that seemed to be a relatively easy trim? We both thank you in advance for any recommendations.
Click to expand...

GLIDER DESIGN & TRIMMING "LIBRARY" . . .​

https://www.rocketryforum.com/threads/glider-design-trimming-library.155758
 
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Almost any pop pod glider will be easier to trim than the ancient designs from the early days of figuring out boost gliders.
 
TheAviator said:
Check here for lots of tips:

https://www.nar.org/contest-flying/competition-guide/duration-events/boostglide-duration/
In particular, Ed LaCroix's writeup on his Maxima glider is great reading for how to trim.

https://www.nar.org/wp-content/uploads/2014/05/Maxima-A-BG-Lacroix.pdf
Click to expand...

That is an exhaustively detailed construction plan, and yet it omits the the design glide c.g. location.

The symmetrical design is not bad for a beginner's kit, but most advanced designs have some asymmetry designed in for better circular glide performance.

I object to the pitch trimming by warping the bare trailing edge of the stab. It will constantly need adjustment, even between trimming and flight. You should use a more permanent way to set the trim. Perhaps the easiest is to dope that area. brush on some thinner and then hold in the warp until the adjustment "sets", and allow it time to fully dry and relax.

In a nutshell, the proper way to build and pitch trim a glider is to: First, add trim weight to put the c.g. where it belongs (For an RG, you might be able to move the motor pod.). There is usually a specified range, so do not overdo the added trim weight. Second, adjust the stab trim, more or less permanently, to get the desired glide. Third, do fine trim adjustment on the field with very small amounts of trim weight. EZ-peasy.

There are also ways to trim for a good hand launch, circle turn, etc., but you will have to hit the library for that info.
 
Alan15578 said:
That is an exhaustively detailed construction plan, and yet it omits the the design glide c.g. location.

The symmetrical design is not bad for a beginner's kit, but most advanced designs have some asymmetry designed in for better circular glide performance.

I object to the pitch trimming by warping the bare trailing edge of the stab. It will constantly need adjustment, even between trimming and flight. You should use a more permanent way to set the trim. Perhaps the easiest is to dope that area. brush on some thinner and then hold in the warp until the adjustment "sets", and allow it time to fully dry and relax.

In a nutshell, the proper way to build and pitch trim a glider is to: First, add trim weight to put the c.g. where it belongs (For an RG, you might be able to move the motor pod.). There is usually a specified range, so do not overdo the added trim weight. Second, adjust the stab trim, more or less permanently, to get the desired glide. Third, do fine trim adjustment on the field with very small amounts of trim weight. EZ-peasy.

There are also ways to trim for a good hand launch, circle turn, etc., but you will have to hit the library for that info.
Click to expand...
I agree with you about objecting by warping the trailing edge up. I once saw or heard of using a bendable piece of small diameter piano wire as a stab-flap stop using an elastic thread to pull the stab-flap up.

Or just put -1 degree negative incidence in the stab.
 
ljwilley said:
The easiest gliders I've ever heard of are the Estes gryphon and the Sky Rocketry Condor Boost Glider- Apogee sells it here:
Condor Boost Glider
Click to expand...

That is really not a bad price for a Flat Cat type BG. I have a Flat Cat that I lost the pod on in my garage after many flights. I have one I have half put together again; and one someplace in the Lair boxes of still in the box.

$14 is not a bad price at all.

1689713761869.png
 
Alan15578 said:
The symmetrical design is not bad for a beginner's kit, but most advanced designs have some asymmetry designed in for better circular glide performance.
Click to expand...
Alan,

That's interesting . . . What is the source for that info and do you have more data on it ? ( Asymmetry producing better circular glide performance )

Dave F.
 
Ez2cDave said:
Alan,

That's interesting . . . What is the source for that info and do you have more data on it ? ( Asymmetry producing better circular glide performance )

Dave F.
Click to expand...
I am the author of that quoted statement. If you want supporting data, do your own research. It is late and I need to sleep.
 
Ez2cDave said:
Alan,

That's interesting . . . What is the source for that info and do you have more data on it ? ( Asymmetry producing better circular glide performance )

Dave F.
Click to expand...
Wtf does that even mean? Are we talking about asymmetrical airfoils? Under-cambered? Circular Airflow by Frank Zaic? Maybe the Colanda effect?
 
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shockie said:
Wtf does that even mean? Are we talking about asymmetrical airfoils? Under-cambered? Circular Airflow by Frank Zaic? Maybe the Colanda effect?
Click to expand...
For my part, it means that The Maxima instructions are incredibly detailed for such a simple symmetric model.

Feel free to discuss any of the topics you raised above.

I chose the asymmetric word to be general and to encompass many common design elements. Perhaps the most common relevant "asymmetry" is stab tilt, but there are many others. The idea is to build in many of the "tweaks" from the start rather than imposing them later in a more difficult trimming process. Furthermore, you want to achieve a coordinated turning flight that will minimize sideslip and trim drag, increasing performance marginally. You can still be competitive with a symmetrical design since "picking air" overwhelms all of these design elements.
 
Alan15578 said:
For my part, it means that The Maxima instructions are incredibly detailed for such a simple symmetric model.

Feel free to discuss any of the topics you raised above.

I chose the asymmetric word to be general and to encompass many common design elements. Perhaps the most common relevant "asymmetry" is stab tilt, but there are many others. The idea is to build in many of the "tweaks" from the start rather than imposing them later in a more difficult trimming process. Furthermore, you want to achieve a coordinated turning flight that will minimize sideslip and trim drag, increasing performance marginally. You can still be competitive with a symmetrical design since "picking air" overwhelms all of these design elements.
Click to expand...
Oh.ok. I don't believe in stab tilt or rudder tilt, rudder tabs,etc.
 
Alan15578 said:
I am the author of that quoted statement. If you want supporting data, do your own research. It is late and I need to sleep.
Click to expand...
I simply asked you about the source of your statement about "asymmetry producing better circular glide performance" ( which, apparently, it is you ).

I, then asked you for more data regarding that phenomenon, which I had never heard of before. "Asymmetry" has many different possible meanings, as it pertains to glider construction, making your statement extremely vague.

Basically, how & why is circular glide performance made better by "Asymmetry" ? Asymmetry of what, exactly ?

Dave F.
 
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shockie said:
Oh.ok. I don't believe in stab tilt or rudder tilt, rudder tabs,etc.
Click to expand...
Ah, one beauty of this sport is that once you build a model and set it in motion, god or mother nature integrates the equations, and what you believe, or what fallacies you hold, make no difference in the resulting performance. You don't even have to know that there are equations that can model the resulting motion.

Stab tilt may not be common. I have not been competing and observing for the last 30 years or so. However, it may be the most obvious asymmetry. It is not something from your bag of tricks that you can keep hidden. Worse, it looks like shoddy construction, rather than sophisticated design. To my old "mind sim" it seems like it might be a good idea for steady state circling flight, but I'm not so sure about broader dynamics, like stall recovery. I think I only tried it once and it seemed OK, but not like now every glider must be built this way. I suppose one could build 10 gliders with stab tilt, and 10 gliders with no stab tilt, but the equivalent rudder deflection, fly them all 10 times, and see if there is any statistically significant performance difference. It is OK to disbelieve. At his point to me, it is just a stylistic choice.

I have spent time observing the flight of soaring birds that spend a lot of time circling above their hunting fields. In recent years, I have seen some some nature documentary films where they have attached small digital cameras to flying birds like Eagles and Falcons. Birds have no rudder or vertical stabilizer, but they do have an articulated horizontal stabilizer. They use stab tilt dynamically to turn and maneuver. I am not aware of any aircraft steering this way. but there may be something to stab tilt worth considering.
 
Alan15578 said:
I suppose one could build 10 gliders with stab tilt, and 10 gliders with no stab tilt, but the equivalent rudder deflection, fly them all 10 times, and see if there is any statistically significant performance difference.
Click to expand...
Rudder deflection will induce a spiraling Roll, during Boost.
 
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Ez2cDave said:
Personal experience . . . Especially on my D BG at NARAM-50.

I used rudder offset to induce a turn. Duting Boost, the glider exhibited wider & wider spirals ( corkscrews), until Burnout.
Click to expand...
That was a bad joke that required no response. I trust that you comprehended the intent of my joke.

Rolling on boost is often a good thing as it tends to straighten out the classic S-curve boost. I don't know how your flight fared, but it does seem to illustrate the need for both boost and glide trimming.

I'd like to see an impossibly rare video of a healthy soaring bird packing moist clay into it left wing to enable it to circle more efficiently. This is a better "bad" joke.

The traditional way to trim HLGs is to add weight to the left wing and warp down the trailing edge of the left wing. This enables a good arm launch, climb out, and transition to circling flight. I personally feel that hand launching and trimming is the most fun part of flying BGs. However, BGs are not HLGs and need not be trimmed this way. As I way of paying it forward, I might advocate a theoretically better way to build or trim, but it is not like I'm trying sell you a car or solar panel. What ever works for you is good enough.
 
Alan15578 said:
Rolling on boost is often a good thing as it tends to straighten out the classic S-curve boost. I don't know how your flight fared, but it does seem to illustrate the need for both boost and glide trimming.
Click to expand...
Alan,

In my case, it did not produce an Axial Roll . . . Rather, it caused an "sprial", similar to a Barrel Roll, which widened with every revolution, presumably as airspeed increased.

Dave F.
 

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