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08-14-2015, 09:54 PM
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Join Date: Aug 2015
Location: Novi, MI
Posts: 107
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RV-7A - Weight & Balance concerns. Is it the right plane for us?
Hello,
This is my first post - I live in Novi, Michigan, close to Detroit. My wife and I own a 0-300 powered 1966 Cessna 172. As we like to travel, we want to upgrade to a faster plane.
Intitially, we thought about getting a 182 or maybe an older Bonanza until another member of our EAA chapter showed us his RV-9A and offered a ride. While we both always liked the looks of RVs, none of us ever even sat in one. OK, now we want one. 
Except of that we could not take our bikes with us, a RV-7A would fit our mission perfectly, I could even do some light aerobatics with it. We also thought that a half-finished kit would be a great option, as I always wanted to build, but as I am afraid that I would not have the endurance to work on the project for 3 or 4 years.
Well, the more I investigate RV-7As, the clearer is becomes that we would most likely face W&B issues. My wife and I weigh, including clothes, headsets, a survival kit, something to drink, phones, etc. 400 lbs.. Based on the weight numbers, here in this forum, most finished planes seem to be around the max. empty weight Vans mentions on their website of 1,130 lbs..
This would leave us with an useful load of 670 lbs.. Minus our weight and full tanks (42 * 6 = 252 lbs.) we would have only 18 lbs. left for baggage.
It also appears as whether the CG tends to be very far aft. It actually seems to be so far aft, that reducing weight on the prop, the avionics or the crew and to instead put more baggage in the baggage compartment, would easily cause the CG to get out of the envelope.
I am now wondering, whether my concerns regarding the far aft CG are valid, whether something can be done about it and how much weight we could save with a fixed pitch instead of a CS prop? What else makes the planes heavy, besides of avionics?
Oliver
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08-14-2015, 10:37 PM
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Join Date: Dec 2011
Location: Livermore, CA
Posts: 6,797
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Of course swapping a CS to fixed pitch will move the cg back - just what you do not want. Have you looked at the -14? More expensive of course, but reports say it's easier to build than a -7. And more room.
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08-14-2015, 11:14 PM
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Join Date: Aug 2015
Location: Scottsdale, Arizona
Posts: 20
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Great questions, Oliver. I'm new to the RV world and wondering the same thing. I'm 215 lbs and have the same concerns ... looking forward to reading the replies.
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08-15-2015, 12:05 AM
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Join Date: May 2014
Location: Ann Arbor, MI
Posts: 25
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Building a 7 close to you
I may not be able to give you great W&B answers, but I am building a 7 at Y47 in New Hudson. If you would like to see one in the build process, please let me know.
Marcus
__________________
Oceanside, CA
RV-7
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08-15-2015, 12:38 AM
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Join Date: Aug 2015
Location: Scottsdale, Arizona
Posts: 20
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Quote:
Originally Posted by mlang
I may not be able to give you great W&B answers, but I am building a 7 at Y47 in New Hudson. If you would like to see one in the build process, please let me know.
Marcus
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Ohhh - I was at New Hudson last month for two weeks (do you remember the red/white Cherokee parked outside about 80 yds east of the self-serve fuel pump?) I would have enjoyed seeing your build in process.
Have fun. Hope to catch you next time I'm in town.
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08-15-2015, 01:54 AM
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Join Date: Feb 2006
Location: Sydney, Australia
Posts: 251
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I'm not sure what numbers you are running. My 7A came to 1,135 lbs and 77.9 in with a Hartzell CS prop. I can get two 200 lb people in, fill the baggage compartment (100 lbs) and the tanks and stay within the CG range (86.36 vs 84.92 in).
I increased my MTOW to 1,900 lbs and flight tested at that weight during phase I. The flight manual states the extra 100 lbs can only be carried as fuel. The fuel must be burnt prior to landing or a heavy landing inspection carried out. I also stick to paved strips in that configuration.
I prefer flying mine with some weight on and the CG aft. It is slightly faster in cruise and you can hold the nosewheel off forever. IMO you would have no problems with a suitably equipped RV7 as long as you are comfortable in it. As the others have said there is a lot more room in the RV14.
__________________
Richard Talbot
RV-7A
Sydney, Australia
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08-15-2015, 04:37 AM
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Join Date: Jan 2009
Location: Hobe Sound, Florida
Posts: 292
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When we head to KOSH we are heavy with full fuel and bags. The issue really is the cg that moves aft in that config with only 5-10 gallons of fuel for landing. We just have to tell ourselves to lower our pitch control gains on landing.
__________________
Kevin Phelps
Paid thru Dec 2020
RV-7A flying N782WP
Stuart, Fl
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08-15-2015, 05:34 AM
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Join Date: Nov 2005
Location: Asheville, NC
Posts: 2,692
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Similar to Mr Talbert, My RV-7A with IO-360-M1B and Hartzell is 1100 lb empty (including cabin fire extenguisher) and has a forward biased CG such that if I follow the 100 lb baggage limit it is impossible to go out the rear GC limit.
At the risk of making general statements, it is my understanding that CGs for a 7A with CS prop will tend forward and CGs for a 7 with FP prop will tend rearward. Other combinations will be inbetween these two tendency limits.
__________________
Bill Pendergrass
ME/AE '82
RV-7A: Flying since April 15, 2012. 850 hrs
YIO-360-M1B, mags, CS, GRT EX and WS H1s & A/P, Navworx
Unpainted, polished....kinda'... Eyeballin' vinyl really hard.
Yeah. The boss got a Silhouette Cameo 4 Xmas 2019.
Last edited by rzbill : 08-15-2015 at 05:37 AM.
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08-15-2015, 07:04 AM
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Join Date: Jan 2011
Location: SoCal
Posts: 391
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What adds weight?
Oliver:
Welcome Aboard! (Surprised I beat Mike- inside joke...). To your question, Almost everything adds weight.
Safety, comfort, convenience, and performance features, with very few exceptions, add complexity, build time, cost, and weight. Software is the only modification I know of with no weight effects.
A friend's 7 has great avionics, seats, upholstery, & other features which make it quiet, comfortable, easy to fly, and safe; my 9a has fewer amenities, is lighter, and safe.
You can build an RV 7 (3, 4, 6...10, 14) light if you wish, and many have. If you decide to build, suggest you consider the designer's thoughts:
"Van’s has always striven for "Total Performance"; the ability to do as many things well as possible. But all airplanes are compromises, and no matter how versatile, each is biased toward a particular 'mission.' "
__________________
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VAF dues paid though exempt
RV-9A sold (I miss that bird!)
RV10 sold (miss that one too!)
RV-14A build underway
Last edited by esco : 08-15-2015 at 07:06 AM.
Reason: added welcome!
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08-15-2015, 07:17 AM
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Join Date: Mar 2005
Location: Dallas area
Posts: 10,768
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Be Careful.........
Quote:
Originally Posted by rwtalbot
I'm not sure what numbers you are running. My 7A came to 1,135 lbs and 77.9 in with a Hartzell CS prop. I can get two 200 lb people in, fill the baggage compartment (100 lbs) and the tanks and stay within the CG range (86.36 vs 84.92 in).
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with this scenario. Remember you won't be landing with full tanks. Try this loading with minimum fuel and make sure you are still within CG range.
__________________
Mel Asberry, DAR since the last century.
EAA Flight Advisor/Tech Counselor, Friend of the RV-1
Recipient of Tony Bingelis Award and Wright Brothers Master Pilot Award
USAF Vet, High School E-LSA Project Mentor.
RV-6 Flying since 1993 (sold)
<rvmel(at)icloud.com>
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