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harmon rocket II question

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.
 
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?
 
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:

DSC_0141-L.jpg
 
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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).
 
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.
 
Weight a minute...

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...:eek: put them in the Advanced Test Pilot category.

Carry on!
Mark
 
Bigger, thicker, stronger?

Why is the redline 275mph and the gross weight 2000lbs since the hrII is based on an rv4?

Spence,
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...
V/R
Smokey

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.
 
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All good info from Tom, Mark, and others.

For more info on what is available NOW, please visit www.f1aircraft.com

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.
 
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

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.
 
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...
 
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.
 
Skin in the game...

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 :)

 
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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.
 
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.?
 
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.
 
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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Testing

Mark Frederick was operating in uncharted territory. By his own admission he was operating at a higher speed than ever before in that airplane.
The statement required at Reno regarding testing is only as good as the integrity of the operator.
The testing itself, if done to Reno protocol, is rather meaningless. Dive testing could be performed 100 times successfully and the next time something flutters. This has proven to be the case with early T18's and Stephens Acro derivatives among others. The ONLY way to know for sure is a full professional analisis, WAY beyond the budget of most Sport Class racers.
Trim tabs are a completely separate issue. If a trim tab or tab linkage fails at race speed, statistically it is fatal, whether an RV, Rocket or composite airplane.
So I stand by my statement that the Reno racers, SARL and others are operating in uncharted territory.
I have an airplane that I built with the intention of racing in SARL. However, in that category, the bar has been raised to a speed well in excess of the speed I am willing to operate my airplane at.
Another completely separate issue is turbulence penetration speed. A Pitts or Pitts derivative is capable of surviving severe turbulence at race speed. Not so with some of the Sport Racers because of the lower stall speed, and in some cases lower G limit.
 
For the record:

The Reno Sport Class test speed requirement is a dive to 105% of the expected fastest lap speed. My expected lap speed the year I had a trim tab let go was 265MPH. The plane was tested to 285mph. So, I exceeded the Sport Class requirements in several dive tests. I know the plane had been to 250+KTAS many times against a 240KTAS Vne.

As Bob remarked, the drop off speed agreed by the racers and briefed by the Pace Pilot and Observer in that section was 160KIAS if I recall correctly. It turned out that we were dropped at ~200KIAS. The NTSB noted that the failure occurred at 306mph TAS.

I'm sorry to be mixing KTS and MPH, but that is what the report reads.

I'll guess the temp at that time was about 80F - so you can see we were very close to 265MPH at the drop - in a dive - at full power. Not good, as it turned out. I ended up 20MPH past where I knew I was safe - QUICKLY. Again I am guessing, but I think the failure at 306MPH occurred about 15 SECONDS after the drop off at 265MPH.

Again, the failure of the tab was caused by an assembly mistake - not a structural overload. But: I installed the part, so it is my fault.

I would not call this particular event a flutter event in the same manner that airframe flutter is being discussed in this thread. I will suggest that you all keep an eye on your trim tabs tho!

Since having correctly built parts installed, that ship has been tested to far more than 306MPH - several times, with no issues. But the lap speeds remain in the 260MPH range. Oh well.

Also, the Sport Class drop-off speeds are monitored quite closely due to this event, and are probably +/- 2KIAS of what is agreed to, and briefed. That is a very good thing, as we have all seen what can happen if the drop speed is not what the pilots think it is.

Carry on!
Mark
 
Reno

Some more food for thought:
Miller Gem flew into a dust devil at Reno and emerged in many pieces.
The homebuilt Mustang clone with Lear wing, structural failure of vertical tail during race.
GP5, wing failure during qualifying. A number of people knew that one was just a question of when.
So far no takers on my question of maneuvering/turbulence penetration speed in races. The various RV's appear to be considerably more vulnerable in this regard than the Rockets.
I am not opposed to the Reno Sport Class Racers. I am concerned that some are not concerned with the issue of an encounter with severe turbulence at a speed far in excess of maneuvering speed.
 
i have always been concerned about flutter with my rv-4. the fastest i ever went with the stock rv-4 aft fuselage was about the speed at the triaviathon competition 250.7 MPH in 1997. after that i modified the fuselage with the fast back and an significantly different type of elevator and rudder construction.
the first surface to flutter in the rv-4 style tail aircraft is most likely the rudder/vertical stabilzer. there have been aircraft in the past that fortunately landed after experiencing sever empanage flutter. one aircraft i am referring to even had the aft portion on the turtledeck in front of the empanage crush inward as if you twisted a cola can in your hands. the bulhead between the longerons under the empanage was torn corner to corner into 4 pieces which gives you an idea of the movement of the tail. the empanage surfaces were trashed and the rudder was inoperable. the pilot did a good job getting it down in 1 piece and told me he was being careful while testing Vne.
my fast back is epoxy bonded and revited. my rudder and elevators have epoxy bonded and revited trailing edges that are about .060" thick with a square trailing edge. they are mass balanced including the rudder. they have .020" skins. they are stronger and stiffer than original construction. the rudder has ribs in every other stiffener location instead of just stiffeners. the trim tab uses close tolerance fits (actually reamed) so as to not allow any play. these are things you can find in any aero engineering book on flutter resistant construction.
i have been able to talk with richard vangrunsven and ken kreuger over the years and both of them understood what i was doing, didn't want me to get hurt, and just suggested ideas that might help. neither endorsed my efforts.
i have been told that the deeper aft fuselage as in my fast back was a good modification to increase torsional stiffness. i am told however, unless you have had flutter testing done on your aircraft you don't know where it may be. also that, since we all build our own they may not be exactly comparable.
this is the third set of control surfaces i have put on my aircraft over it life. the first 2 failed from cracking. i also completely broke the vertical stablizer spar into from side to side about 3" below the top hinge before it was counter weighted. i consider myself a pretty good builder and i know the spar didn't break because of poor construction. i also never self anything unusual during any flight.
the efforts of all racers are to be as careful as they can be, while being aware that the plane is being operated experimentally, perhaps beyond it's design.
reno has it's special safety requirements in an attempt to protect the pilots and fans. bob mentioned the safety changes regarding starting procedures for the metal planes that are of the rv style and modifications thereof. those planes now run on a smaller course so they are less likely to be able to get to questionable speeds which could be dangerous.
the fastest i have gone in a race situation is just over 264 MPH TAS but i don't want anyone to think that would be safe to duplicate. that was straight level and smooth.
 
i have always been concerned about flutter with my rv-4. the fastest i ever went with the stock rv-4 aft fuselage was about the speed at the triaviathon competition 250.7 MPH in 1997. after that i modified the fuselage with the fast back and an significantly different type of elevator and rudder construction.
the first surface to flutter in the rv-4 style tail aircraft is most likely the rudder/vertical stabilzer. there have been aircraft in the past that fortunately landed after experiencing sever empanage flutter. one aircraft i am referring to even had the aft portion on the turtledeck in front of the empanage crush inward as if you twisted a cola can in your hands. the bulhead between the longerons under the empanage was torn corner to corner into 4 pieces which gives you an idea of the movement of the tail. the empanage surfaces were trashed and the rudder was inoperable. the pilot did a good job getting it down in 1 piece and told me he was being careful while testing Vne.
my fast back is epoxy bonded and revited. my rudder and elevators have epoxy bonded and revited trailing edges that are about .060" thick with a square trailing edge. they are mass balanced including the rudder. they have .020" skins. they are stronger and stiffer than original construction. the rudder has ribs in every other stiffener location instead of just stiffeners. the trim tab uses close tolerance fits (actually reamed) so as to not allow any play. these are things you can find in any aero engineering book on flutter resistant construction.
i have been able to talk with richard vangrunsven and ken kreuger over the years and both of them understood what i was doing, didn't want me to get hurt, and just suggested ideas that might help. neither endorsed my efforts.
i have been told that the deeper aft fuselage as in my fast back was a good modification to increase torsional stiffness. i am told however, unless you have had flutter testing done on your aircraft you don't know where it may be. also that, since we all build our own they may not be exactly comparable.
this is the third set of control surfaces i have put on my aircraft over it life. the first 2 failed from cracking. i also completely broke the vertical stablizer spar into from side to side about 3" below the top hinge before it was counter weighted. i consider myself a pretty good builder and i know the spar didn't break because of poor construction. i also never self anything unusual during any flight.
the efforts of all racers are to be as careful as they can be, while being aware that the plane is being operated experimentally, perhaps beyond it's design.
reno has it's special safety requirements in an attempt to protect the pilots and fans. bob mentioned the safety changes regarding starting procedures for the metal planes that are of the rv style and modifications thereof. those planes now run on a smaller course so they are less likely to be able to get to questionable speeds which could be dangerous.
the fastest i have gone in a race situation is just over 264 MPH TAS but i don't want anyone to think that would be safe to duplicate. that was straight level and smooth.

Thanks for all the details Dave! I for one have had quite a few questions about your evolving project and you answered several here.:)
 
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