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Old 02-27-2017, 10:38 PM
rv4dude17 rv4dude17 is offline
Join Date: Nov 2012
Location: texas
Posts: 163
Default harmon rocket II question

Why is the redline 275mph and the gross weight 2000lbs since the hrII is based on an rv4?
Spence Dance - East Texas
rv-4 (built and sold)
rv-8 (purchased flying and sold)
rv-4 (complete) O360 EFII
DAR sign off May 5th 2016, thanks Mel
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Old 02-28-2017, 05:44 AM
fixnflyguy fixnflyguy is offline
Join Date: Jan 2006
Location: Winston-Salem, N.C.
Posts: 951
Default Van is a smart conservative engineer..

As an experimental designer/builder, any number can be applied based on testing,design history, ect. I believe Van to be a smart, conservative engineer/designer/pilot. By utilizing testing, engineering, and also human factor margin of error(building and flying), a conservative assignment of V speed recomendation yields a lower risk factor in the long run. This is just my view, but I believe its pretty accurate.
Bill E.
8A7 / Advance NC
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Old 02-28-2017, 05:58 AM
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Weasel Weasel is offline
Join Date: Dec 2012
Location: Brooksville, MS
Posts: 724

Originally Posted by rv4dude17 View Post
Why is the redline 275mph and the gross weight 2000lbs since the hrII is based on an rv4?
Think of it as an entirely different airplane that happens to use some RV-4 parts
RV-4 715hr Sold
RV-10 "School Bus" - +1500hr counting
Fisher Classic Cassler Power VW sold
RV-10 N7631T 820hr Sold
RV-8 700+hrs
Carbon Cub 200 hr Sold
One-Off Super Cub 100 hr
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Old 02-28-2017, 07:38 AM
Tom Martin Tom Martin is offline
Join Date: Jan 2005
Location: Ontario, Canada
Posts: 1,428

The aft fuselage, from the passenger backrest aft, is pretty much stock RV4. Forward of that everything changes to heavier skins, larger angles, heavier gear mounts, titanium gear legs etc. The wings are shorter but use the same number of ribs. It is a much heavier aircraft then the RV4. John Harmon, the original designer tested the aircraft to these speeds. Over the years the aircraft evolved into the F1 rocket, the design upgraded by Mark Fredrick, with parts manufactured in the Czech Republic. A much nicer kit to put together but the $exchange got out of hand. A few EVO rockets were made, 20 or 30?, of which I have one.
Recently Vince Frazier has started to offer some parts that will make the F1 a possibility again.
Great airplanes, I will never understand why there are not thousands of them flying?
Tom Martin RV1 pilot 4.6hours!
CPL & IFR rated
EVO F1 Rocket 1000 hours,
2010 SARL Rocket 100 race, average speed of 238.6 knots/274.6mph
RV4, RV7, RV10, two HRIIs and five F1 Rockets
RV14 Tail dragger

Fairlea Field
St.Thomas, Ontario Canada, CYQS
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Old 02-28-2017, 07:48 AM
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logansc logansc is offline
Join Date: Feb 2005
Posts: 566

Me either! But for the record, I believe it is accurate to say that Mark Fredericks has hauled the Vne on the F1 Rocket back to 250 KTAS for safety's sake as regards flutter.

This is the only reason mine isn't flying at the moment:

Lee Logan
Ridgeland, SC (3J1)
F1 Rocket #160 flying

Last edited by logansc : 02-28-2017 at 07:50 AM.
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Old 02-28-2017, 07:51 AM
Michael Henning Michael Henning is offline
Join Date: Jun 2011
Location: Nashua, NH
Posts: 511

I'm not suggesting this, but has anyone ever taken a stock RV-4 up to rocket speeds? The fastest that I have taken mine was 195 knots (playing around, and when I noticed the speed, pulled power and pulled up to get rid of the speed).
RV-4 #2750
WW150C Prop
1018 lbs
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Old 02-28-2017, 08:01 AM
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Toobuilder Toobuilder is offline
Join Date: Jul 2009
Location: Mojave
Posts: 4,150

Originally Posted by rv4dude17 View Post
Why is the redline 275mph and the gross weight 2000lbs since the hrII is based on an rv4?
Much the same reason the RV-4 has a higher weight and redline than the Stits Playboy... Because the designer of the new and improved version has made the required modifications to the structure and accomplished the testing to verify.
WARNING! Incorrect design and/or fabrication of aircraft and/or components may result in injury or death. Information presented in this post is based on my own experience - Reader has sole responsibility for determining accuracy or suitability for use.

Michael Robinson
Harmon Rocket II -SDS EFI instalation in work
RV-8 - Flying
1940 Taylorcraft BL-65 -flying
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Old 02-28-2017, 10:11 AM
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F1Boss F1Boss is offline
Join Date: Aug 2006
Location: Taylor Texas
Posts: 708
Default Weight a minute...

Originally Posted by rv4dude17 View Post
Why is the redline 275mph and the gross weight 2000lbs since the hrII is based on an rv4?
If my memory is correct, the max gross on the HR2 was/is 1850lbs? The F1 is 2000lbs, but that was allowed after the Czech engineer had a look at the structure..

Keep in mind: the HR2 and F1 Vne is a TAS number: 240KTAS of 275MPH TAS. Pushing over from 12500' and leaving the power up can get you in trouble VERY quickly. I have heard confessions of folks doing this, and the speeds they reached...well... put them in the Advanced Test Pilot category.

Carry on!
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Old 02-28-2017, 10:42 AM
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smokyray smokyray is offline
Join Date: Jan 2005
Location: TX32
Posts: 1,768
Default Bigger, thicker, stronger?

Originally Posted by rv4dude17 View Post
Why is the redline 275mph and the gross weight 2000lbs since the hrII is based on an rv4?
I built an RV4 in the 80's and flew it 1000 hours. I later bought a flying HR2. I'm not an AE but my friend "KK" is. (designer of the RV10) He enlightened me on several key Rocket-ism's a few years ago.
History: My HR2 was an early one, Bakersfield Bunch built with John Harmon assisting the build when he could. After extensive experience with my RV4, the HR2 was the Four, personified.

The HR2 structure, though RV4 based is structurally superior in 2 key areas.
1. Forward fuselage (fwd of f40) structure is .040.
2. Wings are 19" shorter, effectively increasing wing loading which accounts partially for the increase in VNE. My HR2 has a single piece top wing skin.
The VNE was based on flutter calculations and tested by a qualified test pilot with John Harmon's prototype HR2.

My take on all of it is simple: The canopy rail has Experimental written on the side, treat it accordingly...

PS: Having spoken personally with John Harmon over dinner a few years ago, he consulted an engineer during design of the HR2 and had a test pilot confirm data on subsequent test flights verifying the HR2's structural integrity.

Last edited by smokyray : 02-28-2017 at 10:59 AM.
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Old 02-28-2017, 11:38 AM
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vfrazier vfrazier is offline
Join Date: Jan 2007
Location: Mount Vernon, IN
Posts: 1,120

All good info from Tom, Mark, and others.

For more info on what is available NOW, please visit

We update that site regularly. Very recently, we received some of the new bulkhead parts from the vendor. Made in the U.S. and a bit more expensive, they are perfectly formed with no lumps or bumps to rework. We can't wait to get the rest of them!

More info on the website. Please view it before bombarding the list with questions.
Vince Frazier
F1 Rocket and F4 Raider components
RV and Rocket Accessories, Tailwheels, Tools, & More
1-888-8FLYBOY (1-888-835-9269)

F4 Raider - under construction
F1-H Rocket "Crazy Horse" - sold
RV-4 "Chief Pontiac" - sold
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