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Old 09-17-2019, 06:32 PM
Bernie Bernie is offline
Join Date: Apr 2018
Location: Mountain Green. UT
Posts: 5
Default RV-4 modifications?? for a 6'7" tall pilot

I am a 6'7" tall pilot with much of my height in my legs vs my torso. I spent years test fitting various RV type aircraft and that journey led to my current RV-14 building project #140587 (VS, rudder, and HS done, working elevator, QB wings and fuselage to be delivered late Sept or Oct).

I have the opportunity to buy an unpainted but flying RV-4 but would need to modify to accommodate my size. The seller has allowed me to temporarily move the roll bar & seat back, and remove the rear stick. These temporary moves allowed me to mockup the seating location comfortable for me and eyeball the modifications needed. If I were to buy this aircraft I would;
- move the roll bar back 4.5 - 5 inches
- add new reinforcement to the canopy rail to support new roll bar location
- build a new seating platform just in front of the rear control stick housing
- shorten existing lap belt connection points and fabricate new connection points both aft and wider than existing
- redesign new manual flap lever to match new seating platform
- position new canopy crossbar to fit immediately behind the new roll bar location
- once the new canopy crossbar was in place the existing crossbar would be cut to accommodate the new roll bar location

I am looking for feedback from those familiar with the RV-4 on my plan. My obvious motivation is to take the pressure off my RV-14 build and have an aircraft to fly acro and formation while I continue my RV-14 build.

Thank you in advance for any thoughts or considerations that I have not yet completely thought through.
N914BF reserved for the RV-14
N904BF reserved for the RV-4 should I decide to buy
PPL 1971, USAF officer/pilot 1976-2006
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Old 09-18-2019, 07:00 AM
Scott Hersha Scott Hersha is offline
Join Date: Jan 2005
Location: Cincinnati, OH
Posts: 1,796

I?m actually doing just what you describe on my RV4 right now. I should have it done by tomorrow. I moved my roll bar back 2.75?. I moved the seat bottom hinge aft 1.75?. This will give me a slightly more reclined seat angle, which will aid in head clearance. 4-5? seems like a lot. I did all the things you mentioned - seat belt attach mod, cross-brace moved, etc. I also have manual flaps so the flap lever notches in the seat frame have to be changed. The two side skin bulkheads need to carry the load of the roll bar, and so the .063 metal piece that ties the 1/8? angle under the roll bar to those bulkheads will have to be made to support the new location. Be very careful drilling out the rivets in the original .063 plate. You?ll have to match drill the new plate for riveting back into those same holes, and you don?t want to elongate them. I think you?ll have a challenge getting the roll bar to fit back on the rail unless you plan to modify/re-weld it. The fuselage tapers and moving the roll bar 4-5? aft will move the bolt holes too far outboard to catch the thick angle support piece. I was able to modify the bolt holes in the roll bar slightly to make mine fit, but another couple inches aft would have required a more serious re-do of the roll bar. Good luck - make sure you can still reach the throttle.
RV6/2001 built/sold 2005
RV8 Fastback/2008 built/sold 2015
RV4/bought 2016/sold/2017
RV8/2018 built/Sold(sadly)
RV4/bought 2019 Flying
Cincinnati, OH/KHAO
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Old 09-19-2019, 11:35 PM
riobison riobison is offline
Join Date: Jul 2011
Location: Oliver BC & Red Deer Alberta Canada
Posts: 380

I'm 6ft and its a tight fit for me. Had new cushions made from Oregon Aero and that helped.

I also wear a set of thin sole Simpson Racing Shoes or thin sole slippers. That gave me another 1/2 inch as well my feet are not getting caught or wedged in the pedals.

Clarity Aloft in ear head set saves on the canopy with the extra clearance.
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Old 09-20-2019, 06:12 AM
DanH's Avatar
DanH DanH is offline
Join Date: Oct 2005
Location: 08A
Posts: 9,901

Seen this movie before.

Although fun and interesting, I'd recommend you drop the idea and concentrate on wrapping up the RV-14. It's not just the mods. Taking on a second project to mod, maintain, and fly creates a whole list of cascading issues....including not finishing the firstborn.

Apparently you have some extra cash. Use it to hire help and finish even faster.
Dan Horton
Barrett IO-390
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Old 09-20-2019, 07:02 AM
MWH265's Avatar
MWH265 MWH265 is offline
Join Date: Feb 2016
Location: Virginia
Posts: 111
Default Resale

Don't forget, if you buy the 4 and make all these mods, when the 14 is done you need to find someone tall enough to sell the 4 to. Really narrows the market for you. Unless you plan to keep it.
RV6A Owner/Operator
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Old 09-20-2019, 02:56 PM
Bernie Bernie is offline
Join Date: Apr 2018
Location: Mountain Green. UT
Posts: 5

Scott and others,
- thank you for the thoughts and observations
- please keep any additional thoughts coming
- I would love to hear how your planned modifications turn out
- I will be visiting family in Dayton and Cinci for Thanksgiving and may want to arrange a visit to see your modifications
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Old 09-20-2019, 04:48 PM
Larry DeCamp's Avatar
Larry DeCamp Larry DeCamp is offline
Join Date: Apr 2010
Location: Clinton, Indiana
Posts: 1,069
Default More reference

Kelly Wilson (Indianapolis ) built a solo RV4. It was extensively revised to optimize aerobatic handling etc. You may wish to consult Kelly because it was DONE.

That said, to Dan?s point, the market will be small for an RV3 made for tall pilots.

Jim Winings bought Kellys plane and returned it to a 2 place RV4.
Larry DeCamp
RV-3B flying w/7:1 0320 / carb / Pmags / Catto 3b / digital steam
RV-4 fastback w/ Superior roller 360/AFP/G3X/CPI/Catto3b
Clinton, IN
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Old 09-21-2019, 07:37 AM
rbibb's Avatar
rbibb rbibb is offline
Join Date: Jun 2006
Location: Freericksburg, VA
Posts: 624

I’m 6’5” and made some very minor mods to my RV4 and find it tight but not uncomfortable.

I’d question the need to move the seat back 4-5”.

I realize that 2 inches in height difference is huge and that it depends on where those two inches are - torso versus inseam, etc.

In my case I moved the seat back base just about an inch or whatever I could when moving the roll bar back and not having to modify the canopy frame.

I did adjust the length and therefore angle of the support fuselage formers that form the support under the roll bar assembly attachment points.

Any more than that was going to lead to a cascading set of mods that would have proved impractical.

My biggest issue is headroom. My headset just barely clears the canopy and any decent bump I do make contact with it. It has a few light scratches to prove it.

A mod I didn’t make but wish I had would be to change the brake pedal geometry. I have to be conscious not to apply brakes as my feet have to maintain a rather acute angle with my legs to not apply brakes. Only an issue on landing and something I’m so used to doing I never think of it. In the air enroute it doesn’t matter.

I have a rather thin cushion and a rather sore rearend after long x countries. Not a big deal as I stop about every three hours anyway. Have flown 1200 miles distances with one or two stops and never been so uncomfortable it was an issue.

I’d caution about doing too much modification. If you move the seat back too far you have to move the control stick assembly rear mounting point, then the stock weldment won’t work, etc.

The RV4 is tight. Move one thing and a dozen others are affected, etc.

Pretty soon you’ve made a scratch built center section of the airplane....

But it’s your plane and you can build it however you want but as others have said, the market for single seat RVs is pretty small. But the RV4 is a fantastic plane to fly. My stick time in other RVs is very limited but I flew an RV7 once and was shocked how different it felt. Still orders of magnitude better than a 172, etc but compared to the 4 it felt like I was flying a minivan while 4 seems like what I imagine a Ford GT would.

You might be able to engineer raising the canopy a bit. Would require a lot of work and would add drag, etc. but with some custom made fiberglass skirts you could add 3/4 of an inch or so and if you channel your inner Dan Horton end up with something that looked good and didn’t require as many mods to basic structure. But I’ve never heard of anyone doing that so you’d be on your own.

But if you do end up flying your 4 be prepared to be hooked.
Richard Bibb
RV-4 N144KT
Fredericksburg, VA
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