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  #11  
Old 02-28-2017, 12:14 PM
Mark Albery's Avatar
Mark Albery Mark Albery is offline
 
Join Date: Jul 2007
Location: Redwood City CA
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Quote:
Originally Posted by Michael Henning View Post
I'm not suggesting this, but has anyone ever taken a stock RV-4 up to rocket speeds?
Dave Anders has achieved some remarkable performance from his RV-4

Quote:
The original Triaviathon record was
set by John Harmon in the Lycoming
IO-540 powered Harmon Rocket II on
May 8, 1993. His achievements were:
Top Speed 244.79 mph.
Rate of Climb 3330.21 fpm.
Stall Speed 56.36 mph.
For a score of 1316.45.
Dave Anders’ RV-4, on September
27,1997, achieved the following:
Top Speed 250.71 mph.
Rate of Climb 3308.39 fpm.
Stall Speed 44.78 mph.
For a score of 2381.24.
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  #12  
Old 02-28-2017, 01:01 PM
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logansc logansc is offline
 
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Good call, Mark...I was hoping you'd chime in. My mistake on the Vne all, I was thinking 250 KTAS for some reason, not the correct number 240.


Lee...
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  #13  
Old 02-28-2017, 09:21 PM
jrs14855 jrs14855 is offline
 
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Location: Lake Havasu City AZ
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Default Rocket

Many years ago I had a discussion with John Harmon about the HR2. My recollection is that heavier tail skins were also used. He had some engineering help from an aero engineering class and maybe the professor at an area college.
The shorter span wings reduce the spar bending moment and the closer spaced ribs and heavier skin increase wing strength. I don't recall ever hearing of a structural failure on HR2.
I know of one HR2 that was a many years ago regular visitor to Havasu and did 300 m/h passes down the ramp.
The F1 Rocket had a full blown flutter in a race at Reno, one elevator was mostly gone, landed safely.
I think Dave has flown the 4 faster than the CAFE speed, maybe around 265?? What is Vne on the 4??
The racers, both SARL and Reno and others are in unexplored territory regarding Vne.
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  #14  
Old 03-01-2017, 06:25 AM
Michael Henning Michael Henning is offline
 
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VNE on -4 is 180 knots(210mph).
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  #15  
Old 03-01-2017, 08:38 AM
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smokyray smokyray is offline
 
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Quote:
Originally Posted by jrs14855 View Post
Many years ago I had a discussion with John Harmon about the HR2. My recollection is that heavier tail skins were also used. He had some engineering help from an aero engineering class and maybe the professor at an area college.
The shorter span wings reduce the spar bending moment and the closer spaced ribs and heavier skin increase wing strength. I don't recall ever hearing of a structural failure on HR2.
I know of one HR2 that was a many years ago regular visitor to Havasu and did 300 m/h passes down the ramp.
The F1 Rocket had a full blown flutter in a race at Reno, one elevator was mostly gone, landed safely.
I think Dave has flown the 4 faster than the CAFE speed, maybe around 265?? What is Vne on the 4??
The racers, both SARL and Reno and others are in unexplored territory regarding Vne.
Guys,
VNE is a number calculated by the designer at which exceedance can potentially cause structural failure of one or more portions of the airframe. Aviation is full of stories where aircraft exceeded VNE by a huge margin and survived. However, turbulence, control inputs and G loading all contribute to potential failure. Van set the VNE of RV's conservatively IMHO for that reason. Being an experimental amateur built airplane, builders are free to do whatever they want, knowing full well the implications therein.

Michael/Jim, My HR2 empennage and my RV4 are identical. To build the HR2 you first purchase an RV4 kit, then modify it per the HR2 plans and sub kits. John used .020 skin on the elevator and rudder of the HR2 prototype (I also did on my RV4) which later became standard on all RV4 kits but no other major modifications except for the longer, beefier fuselage and shorter wings and of course the IO-540 growling (and burning alot more GPH) out front. Mark Frederick would further improve on the HR2 with the F-1 design and much refined kits.

Dave Anders RV4 on the other hand is far from "stock" and has some key aerodynamic differences as were keenly pointed out in a recent Kitplanes article.
First, every hinge point has a fairing. The Elevators and Rudder trailing edges are riveted (copied by Van on the RV9 and 10) and he employed Carbon Fiber in several areas. Having seen Dave's masterpiece up close personally several times over the years it speaks of not one big difference but lots of little differences. The Lycon modified IO-360A1B6 (angle valve) and special Hartzell prop that run smoothly at 2900 RPM are just part of the equation. The overall airplane is beyond the Rocket in many specific ways and is truly a design personified showing what determination, forward thinking and experimentation can accomplish.

V/R
Smokey

PS: When I was flying the F16, VNE is 810 KIAS at Sea Level. Exceeding that number was rumored to melt the canopy and catastrophically fail the engine. The fastest I ever saw was 750 KIAS at 500' AGL (1.3 Mach) over the Gulf Of Mexico and that was plenty fast. Discretion is sometimes the better part of valor


Last edited by smokyray : 03-01-2017 at 10:08 AM.
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  #16  
Old 03-01-2017, 12:34 PM
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Weasel Weasel is offline
 
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Quote:
Originally Posted by smokyray View Post
.. and that was plenty fast.

[/i]
I imagine it was.
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  #17  
Old 03-01-2017, 12:41 PM
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longranger longranger is offline
 
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Quote:
Originally Posted by jrs14855 View Post
Many years ago I had a discussion with John Harmon about the HR2. My recollection is that heavier tail skins were also used....
My HRII plans set #211 called for 0.016 elevator and rudder skins, same as the RV-4, but also called for a 0.016 v-shaped doubler inside the trailing edge bends. The doubler was wide enough to catch the aft stiffener rivets. Many guys did upgrade to 0.020 skins.
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  #18  
Old 03-01-2017, 01:01 PM
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AX-O AX-O is offline
 
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Quote:
Originally Posted by jrs14855 View Post
The racers, both SARL and Reno and others are in unexplored territory regarding Vne.
Just because you don't hear about the testing done by some of us, it does not mean that we are in "unexplored territory". It simply means that you are not aware of other peoples efforts. We have to demonstrate (and sign documents certifying completion) certain parameters in race configuration by testing prior to being accepted to Reno.

If collectively we are all testing and racing at those airspeed, does that not become "explored territory" at test day conditions, g-loading, configurations, etc.?
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The information that I post is just that; information and my own personal experiences. You need to weight out the pros and cons and make up your own mind/decisions. The pictures posted may not show the final stage or configuration. Build at your own risk.
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  #19  
Old 03-01-2017, 03:55 PM
Christopher Murphy Christopher Murphy is offline
 
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Location: colorado
Posts: 700
Default Vne and racing

At every race I put on, including the two way speed dashes, it was briefed and cautioned that no aircraft should be flown above a max speed at which it was tested.

Cm.
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  #20  
Old 03-01-2017, 09:13 PM
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rvmills rvmills is offline
 
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Just to touch on a few of the discussion points, as others have done. The OP poses a good question, and the basic differences in build spec that Tom, Smokey, Mark and others have outlined are the major factors. My Super Six was built in the same way...basically a "Rocketized" Six, in much the same way that an HRII is a mutant 4 (Mutant Rocket Drivers...I kinda like that for a patch...whaddya think).

Bottom line is that there are significant differences that justify the higher Vne...and significant testing in the field to support it. As Smokey will tell ya, to take a 4 to Rocket speeds, without the design changes, would not be recommended...and he has a well known flutter story to tell as well.

Mark's flutter in Reno was in part a result of a start that was quite a bit faster than briefed. The high drop-off speed helped Mark get past his Vne, and he did a great job handling the situation. The flutter and failure of the trim tab cable and the trim tab itself was also attributed to a trim tab actuator horn that was not within Mark's specs. When we rebuilt the tail in my hangar, we incorporated some improvements in the design of the tab and the surrounding structure. I will be copying that on my S6 as well.

Our class procedures at Reno have been modified as a result of that event, and we now drop off metal aircraft at slower speeds, at a lower altitude (flatter trajectory), and later (closer to the start pylon), so that there is less time in the chute in a full power descent. That keeps the metal guys safe, and we actually use a flatter trajectory, albeit at a higher speed, in the Gold races, to allow the turbocharged animals to be further up on the power at the release...in this case to help prevent prop overspeeds.

We really do emphasize safety at Reno, and as Axel said, we must certify that we have tested to a speed that is 105% of what we can qualify at. We are not at all flying in uncharted territory...just want folks to know we don't take safety lightly at all there! All out speed when down on the course and level is not our most critical point, in terms of flutter...its in the chute...and we are taking good safety measures there. Bill Beaton qualified at 281 mph in his highly modified HRII, but was very careful about his speed in the chute. Its not dissimilar to what Mark said about lowering the nose at 12.5 and leaving the black knob far forward...Bill knew better.

Finally, Dave Anders' 4 is anything but stock, as others have said. Its a work of science and art...and we may get the chance to see it in Reno this year! I sure hope so!

Cheers, Bob
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Last edited by rvmills : 03-01-2017 at 09:16 PM.
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