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RV4=Efficiency

smokyray

Well Known Member
Thought this was worth a re-print...

Smokey
HR2


Anders RV-4 CAFE TRIAVIATHON
The typical candidates are aircraft with well over 300 horsepower.
We politely told the RV-4 builder that we would consider hosting his record attempt if he would submit an explanation of how his aircraft could realistically qualify as a contender. This was, after all, a very difficult record to break. The original Triaviathon record, set by John Harmon in the Harmon Rocket on May 8, 1993 had stood for over 4 years. Jeff Ackland's record attempt in March 1997 in the 500 hp Legend, had missed the record by about 8%. Jeff had vowed to return with more horsepower in the Legend.

The RV-4 builder was persistent. He submitted an im- pressive list of his RV-4 performance modifications. That list, shown in the sidebar, unquestionably qualified him as a true student of CAFE racing ideas. But could an aircraft with only 200 hp seriously challenge the record? We decided to let him have a shot at it.

When he arrived at the CAFE Foundation hangar, it became apparent that this RV-4 builder meant business. He practiced dentistry in Visalia, California as his day job. By night, however, he was a passionate airplane builder. His name was Dave Anders. He seemed deceptively calm and mild mannered for a man who was about to make a world record attempt. The care and precision evident in all of his many RV-4 modifications spoke volumes about the depth of his commitment to this project. Several of these modifications merit comment:

The polished aluminum finish on this aircraft, which revealed every rivet head, showed superb metalwork. The elegantly simple and clean design of the controls, hardware and interior must also have been a factor in this aircraft winning so many workmanship awards. However, besides per- fecting the aircraft's appearance, Dave also focused intensely on drag reduction and increasing the engine's power output. This passion for excellence in both cosmetics and per- formance suggested he might surprise us with his score.

Preparing N230A for the record attempt would mean achieving an optimized power to weight ratio. This meant removing as many non-essential parts of the aircraft as was legal within the FARs. At the August 1997 Oshkosh Convention, when Dave made the decision to go after the record, he began dieting. By the time he arrived at CAFE, he had lost 23.5 pounds of body weight in 7 weeks! He figured that every pound he lost would increase his rate of climb by 3 fpm.

The cooling system modifications include 34 square inches of total inlet area through two machined, axi-symmetric inlets with internal diffusers to a downdraft plenum. The cooling outlet is 24.7 square inches and is augmented with exhaust flow. The fuel injector servo throat was opened and its diffuser re-profiled, eliminating 3 of the 4 ram sensing tubes in the throat. Holes, radii and polished chamfers were used everywhere possible to save weight.
TRIAVIATHON HISTORY
The Triaviathon scoring formula is:
28110625 x [Vmax x ROC]2
Score = [4100625 + Vso4] x 109
where Vso is stall speed, ROC is rate of climb and Vmax is the top speed at 6000' pressure altitude.
The formula is complex because it was designed to proportionately reward stall speeds between 35 and 70 mph. Stalls above 70 mph receive a progressively increasing scoring penalty. Stalls below 35 mph do little to improve the score.

The measured rate of climb is converted to equal that for the altitude window of 2500'-3500' in standard day atmosphere.

The barograph, mounted on the wingtip, uses its own calibrated pitot-static source while the cabin barograph is connected to "T" fittings in the aircraft's pitot static system. The cal- ibrated airspeeds (CAS) recorded on the wingtip barograph provide a correction table for the cabin barograph recordings.

If the test flight shows that the stock static system is accurate, the rate of climb performance of the second flight, made without the wingtip barograph, can be used for scoring. If the static system is not accurate, the ROC from the first flight is used in the scoring.
PREPARATIONS

Dave arrived at the CAFE hangar on Friday, September 26, 1997, with his wife, Diane, and an entourage of well-wishers. The first task was to drain all of the fuel from his aircraft and measure its empty weight. N230A weighed just 975 lbs. empty including the IO-360 A1A Lycoming engine and Hartzell constant speed propeller. Installation of the barographs and camcorder was made by the CAFE team in preparation for a record attempt at dawn. Everyone hoped for clear skies and smooth air.

Meanwhile, Dave applied thin blue translucent Mylar tape to all gaps and surface slits on the aircraft to reduce leakage drag. He installed a very small "racing" tailwheel. Tiny, precisely-built afterbody fairings for the fuel tank quick-drains and aileron hinges (using scaled airfoil coordinates!) were installed in preparation for the record run.

Dave arrived the next morning wearing very light clothing ("Hammer pants") and very lightweight shoes like those used by wrestlers. He skipped breakfast and made one last trip to the bathroom before climbing into N230A.

The first flight was made with about 12 gallons of fuel. Stall speed was recorded on the wingtip barograph. Dave exhibited great piloting skill as he delicately approached stall using the maximum allowable manifold pressure (14" Hg.). The Vmax speeds registered on the wingtip and cabin barograph were recorded and compared.

The second flight was made with about 8 gallons of fuel, allowing just enough for VFR minimums. The rate of climb and Vmax part of Dave's record derived from the second flight. During those Vmax runs, the propeller turned at just over 2900 RPM, the limiting speed for a constant speed prop.
TRIAVIATHON RECORDS

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.
Score: 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.
Score: 2381.24.

This bettered John Harmon's previous record by over 1,000 points and 'raised the bar' so high that future Triaviathon contestants may have to use aircraft that are 'purpose-built' for the event. As one considers what kind of aircraft that would be, many very challenging design questions arise. Would it have more span? a thinner wing? retractable gear? full span Fowler flaps?

Dave's plans for future modifications are a carbon fiber cowl, elevator and rudder, along with a fastback canopy to reduce flow separation at the canopy trailing edges. There is a clear possibility that his record may be broken in the near future by a woman aviator -- his wife, Diane!!
CONCLUSIONS

A highly modified RV-4 has shattered the CAFE Triaviathon record. David W. Anders, pilot/manufacturer and Richard VanGrunsven, designer, will have their names inscribed upon the perpetual CAFE Triaviathon Trophy and will be officially recognized at the 1998 Oshkosh Convention for this new world record.

It is noteworthy that the RV-4 aircraft is not purpose-built for Tri- aviathon competition; it remains a 2-place, aerobatic, efficient cross-country travelling machine. The big lesson from this new record is that keeping an aircraft's weight to a minimum has a magical effect upon its performance. Efficient structural engineering deserves the same attention as drag reduction and engine hot-rodding.

It was a pleasure and a privilege to host Dave Anders and his RV-4 for its record attempt in the CAFE Triaviathon. He should be congratulated for his extraordinary achievement in producing this remarkable aircraft and its new world record.

http://www.youtube.com/watch?v=wrJ0HlzGeyg&feature=related
 
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smokyray

What an inspiring story, I have an older slow build RV4 that I am working on
tail feathers............Tom
 
upgrade

So... how do we get an RV-3 in the trials.... anybody?.... Any suspicion that a -3 would beat the -4? Smokey.... you in?
Best
Brian
 
By the time yoiu juice the engine and install a c/s prop a 3 will be to heavy to meet the 44 mph stall that the 4 did. A couple of us ran the numbers back when Dave did this. :mad:
tm
 
Long time ago..

My RV4 was brand new in 97', it's first year of flight. At that time when I read the article I was amazed considering all the hard work I had done just to get mine flying. 12 years later it still amazes me...

Smokey
HR2
 
Enjoyed the OP; quite a story. I also enjoyed the youtube link. First time I've seen a RV-4 with the fastback conversion. That is one good lookin' plane!

wj
 
Smokey,
Thanks for posting that. I have some numbers that are not as technical, but some may find interesting. I am in my 40 hours of phase one flight testing. My RV4 is pretty basic. I built it with a 180 hp O360 (I rebuilt). It has a Sterba 70 x 80 wood prop. It is day/night VFR with steam gauges. It came in at 951 pounds painted but with no seats. My home field is at 6,200 feet (New Mexico). My flight testing is at fairly high density altitudes. Last weekend I was doing climb/decent test. I flew for 1.2 hours at various power settings. When I topped off at the pumps ? 7.5 gallons. I flew again yesterday. I stayed at the airport and shot landings. I flew .8 hours, again at various power settings. This time I used 4.0 gallons.
I know this doesn?t prove much as far as good solid numbers go. But it was a pleasant surprise for me. I?m loving this airplane.

Cameron Smith
RV4 #68
 
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