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Author Topic: Adjustable Elements for a Competition CL Aerobatic Airplane  (Read 2833 times)

Offline Trostle

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Adjustable Elements for a Competition CL Aerobatic Airplane
« on: March 02, 2021, 11:55:48 PM »
This is a take off from the recent post/questions about ball links.

If one is planning to build a model for serious competition stunt, the following elements should be part of the design:

 1.  Adjustable leadouts
 2.  Adjustable tip weight
 3.  Adjustable left/right flap trim
 4.  Adjustable elevator/flap ratio
 5.  Adjustable elevator trim relative to flaps
 6.  Adjustable tank height (fuel pick up position relative to spray bar) or build multiple tanks to suit what the engine is demanding
 7.  Rabe rudder with programmable rudder movement relative to elevator movement and have the ability to change the offset at neutral elevator

Extended list:

 8.  Multiple venrturis with different bores and lengths
 9.  Multiple muffler configurations that can be fit to the engine of choice
10. Premixed fuel containers with the same oil content but different nitro content so nitro content can be changed at the field while maintaining the same oil content.  Allows finding the best fuel given the temperature and pressure density

It should almost go without saying that a handle is needed with adjustable line spacing and the ability to change the center of that spacing.

If one thinks he can fly well enough and is serious about competing successfully for a Nats top 5 (or 10) position or making the US Team to the World Championships, then using Igor Burger's logarithmic control control system should be seriously considered.

Keith
« Last Edit: March 07, 2021, 02:59:29 PM by Trostle »

Offline Dave Hull

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Re: Adjustable Elements for a Competition CL Aerobatic Airplane
« Reply #1 on: March 03, 2021, 01:54:23 AM »
I would add, to Keith's list, for completeness:

--Adjustable CG (longitudinal axis)
--Adjustable gear height and stance. One might also include tracking. You might want to make changes based on surface (pavement vs. grass), for example
--If you didn't include the Rabe rudder, you might include instead a fixed offset, ground adjustable rudder.
--For those that mess with it, you might want to change engine offset, or if your building alignment isn't good, a vertical thrustline tweak

Some of these you get right once, and practically never change again, and others are endlessly fiddled with. I can recall one flyer that used lead shot for wingtip weight. Between every flight he would add or take out at least one pellet. I think if conditions changed, he changed the weight. If the ice cream truck drove by he changed the weight,,,,


Of course, we always adjust power level and propeller pitch as well. Which is a whole 'nuther discussion.

To some extent, if the kit is very well engineered, and it is built nearly perfectly, and if the flyer is not too picky, most of these adjustments are less critical. On old designs things were somewhat adjustable but often involved a knife and glue. Most flyers wouldn't settle for that nowadays....

Offline Larry Renger

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Re: Adjustable Elements for a Competition CL Aerobatic Airplane
« Reply #2 on: March 03, 2021, 07:52:38 AM »
Dang, that sound like work, not fun!  VD~
Think S.M.A.L.L. y'all and, it's all good, CL, FF and RC!

DesignMan
 BTW, Dracula Sucks!  A closed mouth gathers no feet!

Offline Ken Culbertson

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Re: Adjustable Elements for a Competition CL Aerobatic Airplane
« Reply #3 on: March 03, 2021, 10:30:16 AM »
Dang, that sound like work, not fun!  VD~
Half of Keith's list is on the mockup of the controls I am going to put into my next ship.  I have never used ball bearings for controls before, I don't think I will build without them again.  This took 2 days to build and I was a machinist in my youth so for those of you who can't use a mill I suggest finding an Igor thing instead of making one.  On the "it goes into the plane" version I am starting now the drive arms on the second bellcrank are angled slightly to give me 90 degrees alignment with the elevator horn, I am using smaller bearings in the Igor thing and using slider blocks for adjustment.  I am also lowering the flap adjustment screw down a bit.  With this arrangement 100% of the control adjustments can be made through one access panel.  I plan to use this rig in a profile so that I can refine the adjustability.

For those of you that are already using Igor's ideas the concept of having more flap on the rounds and more elevator in the corners is old news but to me this is like being 12 again and finding your dad's copy of Playboy hidden in the garage.

Ken 
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Offline Brett Buck

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Re: Adjustable Elements for a Competition CL Aerobatic Airplane
« Reply #4 on: March 03, 2021, 10:34:53 AM »
Dang, that sound like work, not fun!  VD~

   It's more fun when you win.

      Brett

Offline Howard Rush

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Re: Adjustable Elements for a Competition CL Aerobatic Airplane
« Reply #5 on: March 03, 2021, 10:37:52 AM »
Why is your Igor bellcrank metal?  There’s no moment between the arms and the axle.
The Jive Combat Team
Making combat and stunt great again

Offline Ken Culbertson

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Re: Adjustable Elements for a Competition CL Aerobatic Airplane
« Reply #6 on: March 03, 2021, 11:09:21 AM »
Why is your Igor bellcrank metal?  There’s no moment between the arms and the axle.
Not sure what you are asking on the moment.  The parts are elongated a bit to allow for adjusting the ratio but the settings here are what I got from Igor it performs flawlessly on the board.  Both settings on the arm (longer & shorter) resulted in a degradation so I guess he got it right and there is no need to make the drive arm adjustable after all.

What are you making yours from?

Maybe I should have stated that this one is for a profile and the attachment for the bellcrank is pretty well hidden behind the horn.

Ken

Here is a link of a bench test.



« Last Edit: March 03, 2021, 11:55:47 AM by Ken Culbertson »
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Offline Howard Rush

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Re: Adjustable Elements for a Competition CL Aerobatic Airplane
« Reply #7 on: March 05, 2021, 12:42:39 AM »
This is a take off from the recent post/questions about ball links.

If one is planning to build a model for serious competition stunt, the following elements should be part of the design:

1.  Adjustable leadouts
2.  Adjustable tip weight
3.  Adjustable left/right flap trim
4.  Adjustable elevator/flap ratio
5.  Adjustable elevator trim relative to flaps
6.  Adjustable tank height (fuel pick up position relative to spray bar) or build multiple tanks to suit what the engine is demanding
7.  Rabe rudder with programmable rudder movement relative to elevator movement and have the ability to change the offset at neutral elevator

It should almost go without saying that a handle is needed with adjustable line spacing and the ability to change the center of that spacing.

If one thinks he can fly well enough and is serious about competing successfully for a Nats top 5 (or 10) position or making the US Team to the World Championships, then using Igor Burger's logarithmic control control system should be seriously considered.

Keith

I suspect that you are correct, although there’s a way around number 6.
The Jive Combat Team
Making combat and stunt great again

Offline Howard Rush

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Re: Adjustable Elements for a Competition CL Aerobatic Airplane
« Reply #8 on: March 05, 2021, 01:35:40 AM »
Why is your Igor bellcrank metal?  There’s no moment between the arms and the axle.

I left out a few steps.  If one designed a flap control horn from scratch, he’d trade friction, weight, effort, and money and probably come up with something like the Veco control horn.  The axle would need to be little to minimize friction at reasonable weight and expense, yet strong enough to take the load.  That probably leads to a 1/8” steel rod axle.  The joint between the flap control horn axle and the input arm has to take the flap hinge moment (torque).  Using ball joints or other fancy bearings, one could get away with a plywood or plastic arm, but the torque requirement at the joint suggests a brazed joint, at least, hence a metal input arm.  The Igor bellcrank has no torque on its axle, so glue is strong enough to fasten it to the bellcrank arms, hence they be made from 1/16” plywood or thin carbon composite.  I use carbon, because that’s what I have around.
The Jive Combat Team
Making combat and stunt great again

Online Lauri Malila

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Re: Adjustable Elements for a Competition CL Aerobatic Airplane
« Reply #9 on: March 06, 2021, 12:01:51 PM »
Hey, don’t forget venturi’s. L

Offline Trostle

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Re: Adjustable Elements for a Competition CL Aerobatic Airplane
« Reply #10 on: March 06, 2021, 03:20:14 PM »
Hey, don’t forget venturi’s. L

Hi Lauri,

Good point.  In the same mode, there are possibly different mufflers than can be adapted to the engine being used that can be used as a trimming function.
I will add these to my list.

Thanks

Keith

Offline Don Jenkins

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Re: Adjustable Elements for a Competition CL Aerobatic Airplane
« Reply #11 on: March 24, 2021, 03:31:59 AM »
I thought most of the top guys in the country, if not the world, are using electric power.  This eliminates the need for many aspects mentioned above associated with IC power.  I have recently switched over to electric, and although I am not a threat to win any contest, once you have the system set up after a few 2 minute flights, waving your arm at the judges, pushing a button and flying for 6 minutes without any worries of a good engine run really adds to the enjoyment of the hobby.  Just my two cents. 

Don

Offline Ken Culbertson

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Re: Adjustable Elements for a Competition CL Aerobatic Airplane
« Reply #12 on: March 24, 2021, 07:06:52 AM »
I thought most of the top guys in the country, if not the world, are using electric power.  This eliminates the need for many aspects mentioned above associated with IC power.  I have recently switched over to electric, and although I am not a threat to win any contest, once you have the system set up after a few 2 minute flights, waving your arm at the judges, pushing a button and flying for 6 minutes without any worries of a good engine run really adds to the enjoyment of the hobby.  Just my two cents. 

Don
y1 y1
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Offline Trostle

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Re: Adjustable Elements for a Competition CL Aerobatic Airplane
« Reply #13 on: March 24, 2021, 09:17:26 AM »
I thought most of the top guys in the country, if not the world, are using electric power.  This eliminates the need for many aspects mentioned above associated with IC power. 

Don

Six of the ten items listed are desirable trim capabilities if the power is IC or electric.  Just saying.

Keith

Offline PJ Rowland

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Re: Adjustable Elements for a Competition CL Aerobatic Airplane
« Reply #14 on: July 07, 2021, 12:52:56 AM »
Six of the ten items listed are desirable trim capabilities if the power is IC or electric.  Just saying..

LOL spot on..


Yeah but come on Keith.. realistically how important is "trim" ? when comments like "I thought most of the top guys in the country, if not the world, are using electric power.  This eliminates the need for many aspects mentioned" exist.


I want to find one of these electric systems that all of a sudden make planes fly off the bench perfectly.

Learning to trim is a skill I was taught as a 5 year old learning to throw a glider. Trim it for a better flight.

The same applies except today Im pressing a button to throw my plane into the air.

Having a trim solution ISNT an elitist thing to build into a design. You can improve a great deal by having a plane that will go where you want it.



If you always put limit on everything you do, physical or anything else. It will spread into your work and into your life. There are no limits. There are only plateaus, and you must not stay there, you must go beyond them.” - Bruce Lee.

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 I Yearn for a world where chickens can cross the road without having their motives questioned.


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