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  #11  
Old 07-08-2018, 09:04 AM
Captdf Captdf is offline
 
Join Date: Feb 2014
Location: Cypress, TX
Posts: 12
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IO-320, Catto prop. 1500 max gross, 971 empty weight, 71.44 empty weight CG. With full fuel and me (180 lbs) my max back seat weight is 158 lbs using Vanís recommended CG.
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Cypress TX - KEYQ
RV-4, IO-320
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  #12  
Old 07-08-2018, 09:37 AM
Nate-ISU Nate-ISU is offline
 
Join Date: Mar 2013
Location: Indianapolis
Posts: 43
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0320 w/wood prop & 4" spacer; 1020 GW / 1500 Max / No more than 200lbs behind the roll bar for me. No acro at those weights. I've done light stuff (aileron rolls and lazy wing overs) with my mom that clocks in at maybe 105lbs. I've flown with my buddy ~230lbs in the rear; pitch wasn't scary sensitive but certainly noticeable. Plane flares itself after level off and never reached the regime of needing forward stick but I kept it to 3pts; a wheel landing definitely would have required it.
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  #13  
Old 07-08-2018, 01:10 PM
Vac Vac is offline
 
Join Date: Jul 2009
Location: Niceville, Florida
Posts: 345
Default Spreadsheet

Happy to share an RV-4 weight and balance spreadsheet that allows you to input wheel weight and arms. These data should be available for any airplanes you are considering purchasing and you can run your own numbers...accuracy of the data varies, however. That’s why a trust but verify technique may be warranted and you should consider reweighing any “new to you” RV. Drop a PM or email and I’ll be happy to send it to you.

Each airplane is going to be a bit different, but handling characteristics do change with CG. If it’s a light nose airplane (O-320/wood or composite fixed pitch prop), you can experiment with different size crush plates to change the empty CG. If it’s a heavy nose (O-360/constant speed prop), empty CG is likely further forward, but you can run into max gross weight sooner. Just depends!

One other consideration is footwells, if you’ve got ‘em it’s easier to accommodate folks with longer legs, regardless of their weight—otherwise their knees can interfere with the canopy bulkhead behind the pilot’s seat.

If a four doesn’t meet your requirements and you like the tandem configuration, an eight might. The handling characteristics of a light nose four are as close as you can get to a three and occasionally share the fun with someone else...lots of discussion about CG effect on handling characteristics in the training manual over on the safety page...good luck!

Cheers,

Vac
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RV-4 2112
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Last edited by Vac : 07-08-2018 at 01:17 PM.
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  #14  
Old 07-11-2018, 01:26 AM
Lufthans's Avatar
Lufthans Lufthans is offline
 
Join Date: Dec 2017
Location: Hilversum, The Netherlands
Posts: 37
Default Wheeler or three point?

Ours has an O-320 and Catto prop, so not all that heavy on the nose. We've only gotten her a few months ago, and I fly mostly solo. My girlfriend (125 lbs), her 15-year-old daughter (about the same weight) and my 15-year-old son (not a whole lot more) have been the only passengers up till yesterday. And sure, she got a bit more pitch sensitive, but nothing to worry about.

Going with the Vans numbers, I could have someone up to 200 lbs in the back, so combined with the above experience, I didn't think much of putting a 170 lbs friend in the back. But boy, does that feel differently! Especially when flaring for landing.

I'm not exactly sure what happened. I started to flare lightly to make a slick threepointer. Or so I was planning. The nose shoots up in the air and I end up way behind the power curve. So I correct by pushing the nose down. No response. If anything, the nose went up further and for a moment it felt like control responses were reversed. Smaller inputs then, plus a dab of throttle to get some air over the tail and prevent me from dropping in from 10 feet. That seemed to smooth everything out, and a second later I was down on the runway safely.

It happened very quickly, and I find it hard to determine what happened. The gusty wind might have something to do with everything, but I feel the backseater certainly was a factor. I think next time I have a passenger, I'll wheel it on, rather than threepoint.
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Hilversum, The Netherlands

PH-SUM RV-4; Imported and upgraded.
PH-BRR Bowers Fly Baby; Imported and upgraded
PH-MGA Jodel DR1050; Built, with Subaru EJ25
PH-EIL RV4; Imported and upgraded for friend. Sadly crashed
PH-ERD Robin DR300; Built with Subaru EZ30 for friend.
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  #15  
Old 07-11-2018, 11:57 AM
Whitman Whitman is offline
 
Join Date: Oct 2010
Location: 2R4
Posts: 201
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0-320E2D, Whirlwind GA prop 1988 RV-4.

195lb front seat pilot
228lb passenger
0lbs rear baggage

Using Foreflight W&B calculator (incredibly complicated to set up) yields 76.6 takeoff (full fuel), and 77.4 inches (zero fuel CG). Design limits as we know are 68.7 to 77.4 inches aft of datum.

My personal limit is 210 behind the roll bar. The Rv-4 goes from being a lamborghini to a Cadillac when you add a rear passenger.
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  #16  
Old 07-11-2018, 12:01 PM
rv7charlie rv7charlie is offline
 
Join Date: May 2006
Location: Pocahontas MS
Posts: 3,018
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I think a closer analogy than Caddy would be Porsche 911 with 1950's era rear tires.
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  #17  
Old 07-11-2018, 12:32 PM
springer springer is offline
 
Join Date: May 2012
Location: AZ/MN
Posts: 305
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Quote:
Originally Posted by Lufthans View Post
Going with the Vans numbers, I could have someone up to 200 lbs in the back, so combined with the above experience, I didn't think much of putting a 170 lbs friend in the back. But boy, does that feel differently! Especially when flaring for landing.

I'm not exactly sure what happened. I started to flare lightly to make a slick threepointer. Or so I was planning. The nose shoots up in the air and I end up way behind the power curve. So I correct by pushing the nose down. No response. If anything, the nose went up further and for a moment it felt like control responses were reversed. Smaller inputs then, plus a dab of throttle to get some air over the tail and prevent me from dropping in from 10 feet. That seemed to smooth everything out, and a second later I was down on the runway safely.

It happened very quickly, and I find it hard to determine what happened. The gusty wind might have something to do with everything, but I feel the backseater certainly was a factor. I think next time I have a passenger, I'll wheel it on, rather than threepoint.
Hans I found keeping a little power to touchdown helped with pitch control. More airflow over the elevator. With a backseater, the -4 is a different airplane.
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RV-4 '88-'09 Built & Sold
RV-8 Purchased
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  #18  
Old 08-02-2018, 04:43 PM
N999BT N999BT is offline
 
Join Date: May 2005
Posts: 197
Default A couple of tips

I have 1100 hours in my -4 now, it weighs 975 (or so) with an O-360 and Catto prop. I did a couple of things to be able to haul a heavy passenger / (bags). First, I moved the battery into the engine compartment, in the right cheek. This allows a forward baggage compartment between the rudder pedals, so you can add weight forward of the CG. I usually put a bag of tools and heavy stuff like my O2 tank, oil, tie downs, etc up there.

Secondly, if I know I am aft CG, I always run the trim forward (down) so that I have more stick force and feel when I get slow with flaps down.

I like to land with half tanks or more if rear loaded.

I hope this helps.
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  #19  
Old 08-02-2018, 05:23 PM
rjtjrt rjtjrt is offline
 
Join Date: Mar 2006
Location: Australia
Posts: 724
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Iím sort of hesitant to post on this thread, but just want to emphasise the importance of W&B in tandem seat RV.
This is an accident report from a few years ago that stuck in my mind.

https://www.atsb.gov.au/media/24397/...701033_001.pdf
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  #20  
Old 08-03-2018, 02:17 AM
Lufthans's Avatar
Lufthans Lufthans is offline
 
Join Date: Dec 2017
Location: Hilversum, The Netherlands
Posts: 37
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Ouch. Not exactly light reading. Thanks for sharing though!
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Hilversum, The Netherlands

PH-SUM RV-4; Imported and upgraded.
PH-BRR Bowers Fly Baby; Imported and upgraded
PH-MGA Jodel DR1050; Built, with Subaru EJ25
PH-EIL RV4; Imported and upgraded for friend. Sadly crashed
PH-ERD Robin DR300; Built with Subaru EZ30 for friend.
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