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  #1  
Old 04-06-2021, 07:36 AM
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craig.roser craig.roser is offline
 
Join Date: Feb 2019
Location: BRADENTON
Posts: 21
Default WEIGHT AND BALANCE AEROBATIC MANEUVERS

Does this check against your RV-8:

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Craig Roser

2015 Gunter Malich RV8
2005 Cessna C182T G1000
West Central Florida

Last edited by craig.roser : 04-06-2021 at 08:40 AM.
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  #2  
Old 04-06-2021, 08:55 AM
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Carl Froehlich Carl Froehlich is offline
 
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Location: Dogwood Airpark (VA42)
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It seems that your CG is a little too far forward, not out of spec but perhaps not what you want.

For solo flight, my RV-8 CG is 81 - 83, perhaps as far forward as 79 for a much smaller pilot than me. At most aft CG (gross with passenger, full aft baggage, no forward baggage) the CG is at 86 when down to minimum fuel.

Carl
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  #3  
Old 04-06-2021, 10:59 AM
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craig.roser craig.roser is offline
 
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What would cause too far forward? I didn't build the plane. I'm the third owner. The plane flies great.
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2015 Gunter Malich RV8
2005 Cessna C182T G1000
West Central Florida
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  #4  
Old 04-06-2021, 12:02 PM
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rv8ch rv8ch is offline
 
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Quote:
Originally Posted by craig.roser View Post
What would cause too far forward? I didn't build the plane. I'm the third owner. The plane flies great.
Your W&B shows 35 lbs in the forward baggage compartment - I'd move that to the back if flying solo.
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  #5  
Old 04-06-2021, 12:51 PM
spatsch spatsch is offline
 
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Location: Plano, TX
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Quote:
Originally Posted by craig.roser View Post
What would cause too far forward? I didn't build the plane. I'm the third owner. The plane flies great.
Heavy prop (e.g. constant speed, metal), battery in front, heavy battery (not LiPo), light paint job (not as much weight on tail), bigger engine, Smoke system in front baggage compartment rather than back baggage compartment, .... .

My CG was AT the front of the envelope. Wasn't really a big deal for anything in acro with exception of spin entry and snap rolls which both are a bit easier with the CG further back (but not impossible even at the front of the envelope). Stick pressures obviously get lighter on pull as you move the CG back so that's another reason to not be AT the front ... .

I put a CATO prop on, got a LiPO battery and put a smoke system in the back luggage compartment. Now I can adjust my CG by putting more or less smoke oil in.

So if you just getting started in acro I wouldn't worry and just have fun. If you don't get a clear break on spin entry and you really want to there are many ways to move the CG back.

Whatever you do though make sure it is properly secured... . 20lb at 9G is 180lb... .

Oliver
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  #6  
Old 04-06-2021, 04:43 PM
Daveflier Daveflier is offline
 
Join Date: Jun 2019
Location: Lake Worth Florida
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Default My solution

Following what Ron Schreck posted a number of years ago and consulting with other RV-8 aerobatic types, I elected to add 20 pounds of ballast under the vertical stab. I added 5 lb increments and reached 20 lbs. and have spent the last year averaging four aerobatic flights a week with never an issue.
My RV-8 is nose heavy,Hartzell constant speed,IO-375 with a full Raven inverted system. I installed a smoke system 5 gal tank on the lower aft baggage shelf, but rarely carry more than a gallon of smoke oil. I generally fly with 22 gallons, 11 aside, having a Flop tube in the right tank. Without the ballast, the aircraft was extremely nose heavy at 70kias on final. The day I added the ballast, I had a new aircraft. I use a free app called CG finder, and depending on fuel load I can put a 170lb pax in the aft seat and still be within the c.g. Range, but I never fly aerobatics with a passenger. I did replace the heavy Odyssey battery on the firewall with an Earth X Lithium. The aircraft flies all Sportsman maneuvers just fine. The only limitation being the pilot as to the quality of maneuvers.
My takeoff weight in this configuration is 1544 lbs. My takeoff cg is 82.17 and zero fuel cg is 82.37. My measured arm for ballast placement is 232.38.
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  #7  
Old 04-06-2021, 04:44 PM
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chrispratt chrispratt is offline
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Craig: Perhaps this can help. It's some examples of my RV-8 weight and balance to remind me of limits on my aircraft.
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  #8  
Old 04-07-2021, 07:18 AM
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ronschreck ronschreck is offline
 
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Hey Craig, you've got a great weight and balance program and Oliver and Dave have some really good comments. Nothing wrong with your CG as it is if you are just interested in sport aerobatics. Being heavy in the nose will mean that stick forces will be heavy in looping maneuvers and spin entry will be inconsistent or impossible. Snaps are out of the question. If you are interested in competition aerobatics you are living in the center of one of the most active aerobatic states in the US! Moving the CG aft will lighten the stick and make spin entries crisp and enable you to do snap rolls as well. (Note: stay well below maneuvering speed for snaps. The sweet spot is 100-110 knots.) I regularly flew with the CG about an inch forward of the aerobatic aft limit. This was accomplished by putting 19 pounds of #9 lead shot in a box between the front and aft horizontal stab spars. I drained the shot out before flying with a passenger. I hope to see you in competition some day.

PS: Dave, why not park the Decathlon and compete in your RV for a change? We need your support.
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