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  #11  
Old 05-27-2018, 03:55 PM
MConner MConner is offline
 
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Location: Snead Island, Florida
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Quote:
Originally Posted by plehrke View Post
And make sure you remove when carrying load with aft CG.
The sailplane has a flashing caution light that has to be cancelled that warns us that ballast is installed.
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  #12  
Old 05-27-2018, 04:43 PM
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Toobuilder Toobuilder is offline
 
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Location: Mojave
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Some time ago I proposed a slug of lead in an aluminum tube spanning the fuse sides under the stab to address the RV-8 solo CG issues. Have not implemented it yet, but the cautions for spin recovery are valid until proven otherwise. Even a little weight that far aft will alter the MMOI of the vehicle.
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  #13  
Old 05-27-2018, 06:46 PM
Kyle Boatright Kyle Boatright is offline
 
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Location: Atlanta, GA
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Quote:
Originally Posted by MConner View Post
Kyle, caution noted. I am not planning to load the plane outside the normal CG limit but right now it is at or ahead of the forward limit with no baggage/ballast.
The issue is the moment of inertia. Think of a two pound stick that's a couple of feet long, but most of the weight is located towards the center. Give that stick a spin and it'll spin rapidly, but slow down relatively quickly too. Take that same stick and put the weight out towards the ends and it'll be harder to get spinning, but once it begins spinning, it'll want to keep spinning - think about a majorette's baton.

Putting a weight on the stinger will make your airplane more like a baton - with more weight out towards the ends. Slower to generate a yaw rate, but once you have a yaw rate (say in a spin), it'll be more difficult to slow/stop that yaw rate.
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  #14  
Old 05-27-2018, 09:12 PM
rv7charlie rv7charlie is offline
 
Join Date: May 2006
Location: Pocahontas MS
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But if it takes 50 lbs in the baggage area, it might only take 2 lbs on the tailspring. Moment of inertia should be the same, right?
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  #15  
Old 05-27-2018, 09:38 PM
BobTurner BobTurner is offline
 
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Location: Livermore, CA
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Quote:
Originally Posted by rv7charlie View Post
But if it takes 50 lbs in the baggage area, it might only take 2 lbs on the tailspring. Moment of inertia should be the same, right?
No, thatís not the way it works.
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  #16  
Old 05-27-2018, 10:12 PM
MConner MConner is offline
 
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Location: Snead Island, Florida
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Quote:
Originally Posted by rv7charlie View Post
But if it takes 50 lbs in the baggage area, it might only take 2 lbs on the tailspring. Moment of inertia should be the same, right?
I agree, the CG is what it is. I do not do acro and and the chance of me getting a fully developed spin is almost zero.

Mark
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  #17  
Old 05-27-2018, 10:19 PM
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mfleming mfleming is offline
 
Join Date: Sep 2016
Location: Joseph, Oregon
Posts: 261
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Quote:
Originally Posted by Kyle Boatright View Post
The issue is the moment of inertia. Think of a two pound stick that's a couple of feet long, but most of the weight is located towards the center. Give that stick a spin and it'll spin rapidly, but slow down relatively quickly too. Take that same stick and put the weight out towards the ends and it'll be harder to get spinning, but once it begins spinning, it'll want to keep spinning - think about a majorette's baton.

Putting a weight on the stinger will make your airplane more like a baton - with more weight out towards the ends. Slower to generate a yaw rate, but once you have a yaw rate (say in a spin), it'll be more difficult to slow/stop that yaw rate.
Quote:
Originally Posted by rv7charlie View Post
But if it takes 50 lbs in the baggage area, it might only take 2 lbs on the tailspring. Moment of inertia should be the same, right?
Quote:
Originally Posted by BobTurner View Post
No, thatís not the way it works.
I'm getting my popcorn. This might get interesting fast
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RV-7 Slider #74572
Started 11/2016
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  #18  
Old 05-27-2018, 10:33 PM
Kyle Boatright Kyle Boatright is offline
 
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Location: Atlanta, GA
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Quote:
Originally Posted by MConner View Post
I agree, the CG is what it is. I do not do acro and and the chance of me getting a fully developed spin is almost zero.

Mark
For your -10, the spin issue is probably a minor consideration. For folks who are trying to move the CG aft for aerobatics, the moment of inertia is a real consideration because aerobatics increase the odds of entering an accidental spin.
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  #19  
Old 05-28-2018, 05:13 AM
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Larry DeCamp Larry DeCamp is offline
 
Join Date: Apr 2010
Location: Clinton, Indiana
Posts: 635
Default Kyle, your point duly noted !

Without getting Dan H in the arena, is anyone qualified do an MoI comparison between acceptable CG with pax and baggage VS a stinger weight. Is the popcorn done yet ?
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  #20  
Old 05-28-2018, 05:38 AM
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ronschreck ronschreck is offline
 
Join Date: Mar 2006
Location: Gold Hill Airpark (NC25), NC
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Default My solution

Over two years ago I installed a ballast container in the tail of my RV-8 to improve aerobatic performance when flying solo. The concept received many critical comments when I posted it on VAF but I have found that the addition of 20 pounds to the tail of the aircraft has greatly eased the stick forces required in aerobatic maneuvering, especially in inverted flight, and I have no problems with spin recovery or other control issues. The thread can be viewed HERE.

http://www.vansairforce.com/communit...d.php?t=133740
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