About Propellers Other Products Articles Bookshop Gallery Links Contact Supercool

Propeller Dynamics

Essential reading for model aircraft contest fliers. This is the only book on the market explaining propeller theory in non-mathematical terms. A rattling good read, I know, I wrote it.


Reno for Gearheads  
from  Graham White


This report will not be your usual Reno air race report, instead it will concentrate on the unique go-fast features and state of the art engineering that makes Unlimited class air racing the world's fastest motor sport. I wish I could also give race results. Alas, thanks to the despotic acts of the terrorists who did their evil deeds on September 11, 2001, no races occurred therefore, no race results.

For 2001 twenty-nine Unlimiteds had entered, These aircraft ranged from balls to the wall, out and out racers to stock warbirds. If it were not for the wonderful hospitality heaped upon me while at Reno I would never have been able to gather all the neat information incorporated into this report. Pete Law has been involved with Unlimited teams since the 1960s. He started his racing career by designing all the systems; cooling, carburation, ADI and hydraulic for Darryl Greenamayer's F8F Bearcat. This aircraft re-wrote the rules for the Unlimiteds. Not surprising considering that until his recent retirement, Pete was a high level executive working at the Lockheed Skunk Works. I recently got to know Pete and he kindly took 3 hours out of his busy schedule to introduce me to every Unlimited team. Additionally, Pete is a fountain of knowledge on just about every aircraft, mainly because he probably rebuilt and set up the carburetor, designed the spray bar system and ADI system. Others also displayed similar hospitality.

Unlimited racers compete around an 8.2688 mile course marked off with pylons. The pylons are 55 gallon oil drums placed high up on a pole. Although no restrictions exist for the type of aircraft flown, the vast majority of racers are ex-World War II fighters. This is simply because these aircraft represented the fastest piston driven aircraft ever manufactured. Of course, the top racers are highly modified - as we shall see. An argument that has raged almost from the days of the Wright brothers first flight is; which is better: air cooled radial or, liquid-cooled inline. Even to this day, that argument has not been settled. And perhaps this is the way it should be. The see-saw battle of liquid-cooled inline vs. air cooled radial will, apparently, never abate.

Below is a brief synopsis of each aircraft and the modifications incorporated.

Race #4 Dago Red - Highly Modified P-51D.

Dago Red is right at the top of Unlimited racing. It has held the FAI 15 km straight line record at 517.06 mph since 1983 and is presently the fastest qualifier ever at Reno, 490.825 mph. So what makes this aircraft such a phenomenal performer?
This aircraft has been on the race circuit for many years. It started out as a P-51D Mustang. Registered as N5410V it was wrecked and rebuilt in its current highly modified form, and now has been a leading race campaigner since 1982. Hard to say what percentage of the original aircraft remains but we can be sure of one thing; it ain't much.

Engine Modifications:

P-51Ds are normally powered by a Packard built Rolls-Royce Merlin V-1650-7. In stock configuration it is rated at 1,450 horsepower. Dago Red's engine puts out an estimated 3,500 to 3,800 horsepower. And remember, a stock Merlin is no slouch incorporating features such as overhead camshafts actuating four valves per cylinder, two stage intercooled and aftercooled supercharging.....etc. In order for a Merlin to survive at such remarkable powers, first order of business is to beef up the basic structure and strengthen it. As is typical with most V-12 engines, the Merlin features 7 main bearings to support the crankshaft. In the Merlin's case, the main bearing caps have additional support by featuring cross bolts that go right through the engine's crankcase and through the main bearing caps - one either side of the main bearing hold down studs. Rigidity of the crankcase and crankshaft is essential to make the engine survive under high power operation. Therefore, one of the first modifications is to increase the size of the cross bolts. With seven main bearings and two cross bolts per main, a total of 14 main bearing cross bolts are utilized. As an additional aid to stiffening the entire power section structure, the 14 cross bolts go through massive external steel plates that run the entire length of the power section. So far so good. But all this additional power introduces another problem not envisioned by Rolls-Royce. The massive four blade Hamilton Standard propeller is driven through a spur reduction gear that is housed in a nose case. Of course, all this additional power is translated into more propeller thrust. In order for the nose case to stay on the engine, a steel strap attached to the nose case, bolts to the crankcase inside the intake valley. Interestingly, this modification may have been inspired from a repair scheme of World War II. It was quite common for aircraft to make emergency gear-up landings. With a Merlin this would inevitably result in a damaged nose case and/or crankcase (see illustration). Another key item that needs improving over stock is the lubrication system. A stock Merlin has a conventional dry sump system and runs 60 to 80 psi hot oil pressure. Under racing conditions, this is not sufficient. First off the stock pump gears are replaced with longer ones to increase the pump's displacement. However, even this is not sufficient so an additional pump is installed in parallel with the original pump. Merlins have two accessory drive pads on the rear of each cylinder head, four in all. Normally, these pads are used for driving an air compressor, tach. generator...etc. One of these drive pads is used for the additional oil pump. An Allison V-1710 pump does the trick. Oil pressure, with the these modifications now runs over 100psi hot. With all this additional oil being pumped into the engine, scavenging becomes more critical. A stock Merlin has a windage tray to catch oil slung off the crankshaft. An additional windage tray is installed to improve scavenging. To further improve scavenging, the vacuum pump is now pressed into service as an additional scavenge pump. O.K., now we have taken care of the oil supply and scavenging chores, however, the oil has now picked up a tremendous amount of rejected heat. A stock P-51D uses an air-to-oil honey comb cooler mounted in the so-called dog-house. For Dago Red, this oil cooling system is totally inadequate. So Dago Red utilizes the P-51H oil cooling system. In other words, a water/glycol to oil cooler is mounted in front of the fire wall. Coolant is pumped through the oil cooler then to a radiator mounted in the dog house. This offers a far more effective heat rejection route. To further condition the oil, a sophisticated deaerator is installed to purge the entrapped air. However, it's not just the oil that needs to be cooled, the engine coolant, a 50/50 mix of water and ethylene glycol, is circulated through the engine. Running at elevated power settings, a stock cooling system would simply be overwhelmed. It seems that a power setting of 80 in.Hg. Abs manifold pressure is about all the stock cooling system can safely handle. To combat overheating, a highly modified radiator, manufactured by Dave Griswold, is used. It has more tubes, more fins and more rows. To further augment cooling, water is sprayed on the radiator core. Water is introduced via a spray bar system designed by Pete Law. As Bill Kirchenfaut, Dago Red's crew chief, so eloquently stated; at race speeds, it's like Niagara falls spraying on that radiator core. The fact that no after cooler is employed (see explanation later) allows a larger engine radiator to be used. The area normally occupied by the aftercooler radiator is used for engine cooling chores. If one looks carefully at TV images of top Reno Unlimited racers, a distinctive trail of steam can be seen issuing behind the aircraft. This steam is generated by spray bar water that flashes off as it makes contact with the high temperature radiator core. Dago Red will consume approximately 60 gallons of spray bar water in a race, which lasts about 15 minutes. With all these cooling system modifications, coolant temperature runs at 100 degree C and oil runs at 85 degrees C. From the foregoing, it can be ascertained that raising the power of the Merlin is a question of chasing down all the potential weak points. One component in a high horsepower engine that undergoes incredible stress is the connecting rod, possibly one of the most critical of all internal parts. Stock Merlin connecting rods are typical of their ilk, they are blade and fork, although Rolls-Royce took the more difficult manufacturing route of using the 'marine block' variation on this concept (see illustration). Although exquisitely made, Rolls-Royce connecting rods were only designed to tolerate the loads of a stock engine. When manifold pressures exceed 100 in.Hg. Abs, they become fragile. One of the Merlin's main competitor's during WWII was the General Motors built Allison V-1710. Conceptually very similar to the Merlin, i.e., liquid-cooled V-12 and similar displacement. Although much maligned, the Allison was another superb example of aircraft engine design. One feature in particular that distinguished the Allison was the stoutness of its connecting rods. As with the Merlin they were of blade and fork design but considerably stronger. This hands the hot rodders a golden opportunity. Although the center distances from the journal to the wrist pin are slightly different, this can be compensated for by forging special pistons with a higher compression ratio. The ultimate Allison series built were the 'G' series and specifically the G6 series. These G6 rods are the ones installed in Dago Red's Merlin. One normally thinks of Allisons being built in the tens of thousands, which is true, however, only 750 G6 engines were built. Their only application was the North American F-82 Twin Mustang. The available supply has been further depleted by 50+ years unlimited hydroplane racing and tractor pullers where they were the favored Allison. For this reason G6 Allison rods are a much sought after component.

Now that the engine has received structural rigidity, an oil system and cooling system that can handle the additional requirements with beefed up internal and external components, it's time to get serious about making more power. With a highly supercharged engine such as the Merlin, the easy and obvious route is to simply crank up the manifold pressure. And that's exactly what Dago Red does - among other things. It is almost a waste of time trying to improve upon the intake port design or finish. In stock configuration, Merlins' were ported and polished. In service, Merlins' were usually limited, depending on dash number, to 60 in.Hg. Abs This pressure was preset via the automatic boost control. In other words, a pilot could push the throttle to the firewall but the engine would not be overboosted, but it would not operate at full throttle at sea level either. So of course the first thing the racers do is get rid of the automatic boost control. One undesirable by-product of supercharging is increased charge temperature due to compression heating. Rolls-Royce took care of this by having an intercooler and aftercooler incorporated into the supercharger. This simply means two supercharger impellers run in series to boost manifold pressure (see illustration). A coolant jacket in the supercharger housing acts as the intercooler between the two stages, but it really does not accomplish much. Most of the heat from compression is rejected via the after cooler. This is a rectangular, boxy-looking heat exchanger that sits on top of the engine towards the rear. It is a radiator core with compressed fuel/air mixture on the outside of the radiator tubes and coolant flowing though the tubes (see illustration). Works great for reducing charge temperatures, however, it creates a restriction that reduces manifold pressure by about 1 in.Hg. Abs. For a stock Merlin, it's not significant, but for Dago Red's race engine, running at an astronomical manifold pressure, it's a problem to the tune of costing approximately 5 in.Hg.Abs. To get by this problem, a simple pipe replaces the aftercooler. This now introduces the problem of how to get the charge temperature down. This is accomplished by introducing massive amounts of ADI fluid. ADI stands for anti detonation injection. ADI serves two primary purposes; firstly it reduces the charge temperature, via evaporation, as it is sprayed into the intake system. A lower charge temperature increases the density of the charge and reduces the onset of detonation. Secondly, once ADI enters the combustion chamber, it reduces the flame front temperature, again delaying the onset of detonation. ADI fluid is introduced at the intake elbow, colloquially referred to as the Horse's Ass because that's what it looks like..!!! ADI fluid is made up of a 50/50 mix of distilled water and ethanol or methanol. Engines with the aftercooler removed are referred to as 'tube engines.' by the racers. As noted above, stock P-51Ds were typically powered by a Packard built V-1650-7. However, that was not the ultimate Merlin. After World War II, Rolls-Royce developed a civilian version of the Merlin for the more demanding environment of civilian airliner operation, (long range cruise at high power). Rolls-Royce toiled long and hard to get some semblance of reliability and longevity out of the engine. The outcome was the so-called 'transport engine' or more correctly, the Merlin 500 and 600 series. These engines had all heavily stressed parts beefed up, improved cooling jacket design, heavy duty valves....etc. Dago Red uses a Merlin 622 power section with a Packard built V-1650-9 supercharger. The dash nine has optimal supercharger ratios for increased boost. This brings up the next question; how much boost does Dago Red run in a race? The quick and easy answer is; it all depends. During qualifying, only sufficient power is used to move up to the next round. However, when it gets down to the final Gold Race, everything is allowed to hang out. Maximum boost is primarily determined by engine rpm and secondly by ambient temperature and air pressure. In this engine it can run in the 135 to 140 in. Hg. range when at 3400 rpm. Assisting boost is a carefully designed ram air scoop. For Dago Red it is made from fiber glass with an ideal convergent/divergent design. This design picks up approximately 3 to 5 inches of manifold pressure at race speeds. Theoretically, it is possible to run an even higher manifold pressure than 140 in.Hg. Abs But at 140 inches the point of diminishing returns has been reached. In other words so much power is consumed driving the supercharger, very little, if any, additional power is fed to the propeller. At 140 inches, the Merlin two stage supercharger is consuming in excess of 1,000 horsepower to drive. It has even been argued that anything in excess of 100 inches does not produce any additional power to the propeller, however the aircraft will fly faster when running in excess of 100 inches. The argument presented is the fact jet thrust from the exhaust stacks is increased at the higher manifold pressure resulting in a higher air speed.

With all these radical modifications, the engine now has to spin up faster. A stock Merlin is red lined at 3,000 rpm. This may not sound like much but remember, this engine has a 6 inch stroke. By modifying the 'speeder' spring in the propeller governor, Dago Red runs at 3,400 rpm. It would be nice if the engine could be spun faster, however, engine speed is limited by several factors; lowest reduction gear ratio for a Merlin is .420:1 and secondly, propeller tip speed. When tip speeds approach or exceed 1,000 feet per second, propeller efficiency goes down hill. In the past folks have tried to make their own reduction gears with lower ratios than .420:1, however, this means using a smaller pinion and a larger gear. The smaller pinion introduces unacceptably high gear tooth loadings so at the present, this is not an option (see illustration). Two massive oil jets squirt oil into the reduction gears at the point of engagement, so it's not a question of too little lubrication.

Airframe Modifications
All external airframe skins are smoothed out. The so-called radiator 'Dog-House' (the device which responsible for the P-51D being able to develop positive 'jet thrust' sufficient to offset cooing drag, sometimes referred to ad the 'Meredith Effect named after the RAE engineer who is generally credited with the concept) is totally redesigned with reduced frontal area. Interestingly, Dago Red's dog house does not feature a laminar flow splitter as one would normally expect to see. A tiny bubble canopy replaces the stock P-51D's. Wing area is reduced by clipping the wings. The propeller is stock, albeit highly polished on the front and flat black on the rear. It would be nice to polish the prop on both sides, however, this would introduce severe glare resulting in a serious safety concern for the pilot.

After Monday's qualifying, it was noticed that an exhaust stack on Dago Red's 'B' bank was smoking. After further investigation, coolant was found on the center spark plug - a bad sign. The crew set to and removed the head and bank assembly. Sure enough, a large crack was found in the center of the cylinder head that had migrated into the intake port. That head is now an expensive paper weight, it is unrepairable. A spare head and bank assembly was installed. For those who have not worked on a Merlin, this is a major operation, particularly for a race Merlin.

During a 15 minute race, it is not unusual for Dago Red to consume an astounding 2,200 pounds of liquid in the form of fuel, ADI fluid and spray bar water broken down as follows: 900 pounds of spray bar water, 300 pounds of ADI fluid and 1,000 pounds of fuel.

Dago Red is owned by Terry Bland and flown by Skip Holm.

Race #5 Voodo - P-51D Modified:

Voodo was a non show this year, however, it is worth taking a look at. It was intended to race but suffered a catastrophic engine failure just prior to the races. Voodo has always been a top contender but to date has been a bride's maid. For 2001, Jack Hovey built up a special race engine. Time was flown on the newly rebuilt engine and everything was looking good. The power was brought up in increments to 90 in. Hg. At this point the engine back fired. Normally, an engine back firing is no big deal. But with a highly supercharged engine it is serious stuff. Backfiring can be caused by a number of factors, the primary ones being; lean mixture and leaky intake valves. With Voodo it is thought that the carburetor (Bendix PD-18) was set up too lean. When an ignition source is introduced into the intake system, such as a back fire, this lights off a highly explosive, compressed fuel/air mixture. The pressures generated from this uncontrolled combustion are so great it wreaks havoc through the entire engine. Serious damage is incurred by the supercharger and intake ducting. More seriously is the fact that this high pressure momentarily blows open all the intake valves. Allowing high pressure gasses into the cylinder at the wrong time produces what is in effect a 'hydraulic lock' resulting in bent connecting rods. Jack had built this engine with Merlin 622 connecting rods, the ultimate Rolls-Royce built rods. Voodo's back fire and its consequent unacceptably high loading on the power section resulted in bent rods. After the back fire, Matt Jackson, the pilot, kept the engine running but when he pulled the power back for landing a connecting rod failed resulting a destroyed engine. This was too bad as it would have been a top contender. As an aside, Jack Hovey is one of the more experienced rebuilders of Merlins. He built the race winning engine for the 1972 Gold champion, the Roto Finish Special.
A unique feature of Voodo is its use of a carbon fiber cowl. This represents a weight saving and makes it easier to remove the cowl. A stock P-51D cowl is a real chore to take off due to the gazillion Dzus fasteners that have to be removed.
Voodo is owned by Button Transportation and flown by Matt Jackson

Race #7 Strega - P-51D, Highly Modified

Strega is right up there with Dago Red for being at the top of the heap for Unlimited racing. Its engine features all the modifications incorporated into Dago Red, in fact both aircraft share a lot of race technology and even look very similar. One interesting deviation from Dago Red is the placement of the coolant header tank. P-51Ds have a coolant header tank that is horse shoe shaped, wrapped around the engine nose case. In the case of Strega, it is repositioned behind the pilot. Probably does not enhance performance but makes for additional room to work on the engine consequently making maintenance chores simpler to perform.
Flown and owned by Tiger Destafani

Race #9 Cloud Dancer - P-51D

Owned and raced by Jimmy Leeward, a real estate developer in Florida, little is known about this racer. Its stock looking appearance may belie some engine modifications. This aircraft appeared at many earlier Reno events as a highly modified contender in the Gold Race

Race #10 Critical Mass - Highly Modified Hawker Sea Fury

One of the last great piston powered fighters developed was the British Hawker Sea Fury. Developed for the British Fleet Air Arm (FAA), incorporated Hawker's experience learned from developing a number of high performance fighters in WWII. Originally, it was powered by the massive and impressive Bristol Centaurus XVIII sleeve valve engine rated at 2,470 horsepower. Although this engine was a superb example of aircraft piston engine development, its uniqueness, particularly in the US, has dissuaded folks from overhauling them or modifying them for racing. This has resulted in the vast majority of Sea Furys' flying in the US being converted to Wright R-3350 power. Over the years a considerable amount of experience has been gained on how to make R-3350s perform. Perhaps most, if not all the credit, should go to Lyle Shelton who has campaigned a Grumman F8F Bearcat 'Rare Bear' powered by the R-3350. With this experience in mind, Critical Mass has what is essentially the same type of engine with the same modifications as Shelton's. Like many other aircraft engines that remained in production for a long time, R-3350s went through a lengthy evolutionary development phase. Starting out with the under developed and problematic B-29 engines, R-3350s evolved into possibly the most advanced piston engine in the form of the R-3350 turbocompound powering such aircraft as the Douglas DC-7 and later versions of the Lockheed 1049 Super Constellation. Turbocompounding was experimented with by all the major piston engine manufacturers but Wright was the only one who managed to get one into production. Turbocompounding simply means that the exhaust gasses are utilized to power a blow-down turbine which feeds power back to the crankshaft. Or, as Wright referred to them as; power recovery turbines (PRTs). Although the concept sounds great and in fact it was for large transports due to the considerable fuel savings it generated, for racing, the PRTs, three per engine, represent too much weight for too little power gain. However, the PRT engines also represented the strongest and best components. Critical Mass employs a PRT engine but with the PRTs removed. An adapter plate between the power section and blower section accomplishes this with a weight savings and reduced engine length. Unlike inline V-12s, radial engines do not tolerate over revving. Several factors account for this, one being the extreme loads imposed upon the master rod bearings. Remember, with a blade and fork rod set-up in most V-12s, only two cylinders are acting on each connecting rod bearing big end bearing. A radial, on the other had, needs a master rod bearing that can withstand the loading of nine cylinders. With this in mind, Critical Mass races at 3,100 rpm - still a very high number for such a massive engine. By comparison a stock R-3350-26WD is rated at 2,700 horsepower at 2,900 rpm. One of the best propellers developed for the R-3350 was the one installed on the Douglas Skyraider. As with all the other racers, the holy grail of power and efficiency is a low(er) revving propeller. Critical Mass accomplished this via a rare and hard to find nose case. At the end of the piston engine era, Lockheed developed the ultimate airliner, the magnificent 1649 Starliner. Although it superficially looks like a Constellation, it was really an entirely different aircraft. Wright developed a special engine for this aircraft called the EA2. It had a very low reduction gear ratio of .355:1, ideal for driving the Skyraider prop. 287 of these engines were built, most of which have been scrapped, however Critical Mass uses one of these hard to find EA2 nose cases. Again, by comparison, the popular R-3350-26WD uses a less desirable .4375:1 ratio.
The exhaust system is fabricated from scratch utilizing North American T-28 parts. A total of 10 pipes are used - five per side. The outlets are arranged to promote 'air pumping' through the cowl and residual jet thrust. Critical Mass team members admitted to 4,100 horsepower; reality may be considerably higher. Of course, with this amount of potential power on tap, massive amounts of ADI is used to keep detonation under control as well as contribute to lower head temperatures. A stock (Sea Fury) sized spinner is used although made from carbon fiber. The engine cowl is modified from a Douglas DC-7 component. Sea Furys' use a single rectangular oil cooler housed in a wing leading edge. For the power generated by Critical Mass, this would be totally inadequate. To keep oil temperatures under control, two stock sized oil coolers are used - one in each wing. To further control oil temperatures, spray bars are used.
Although the basic airframe is a Sea Fury, little remains of the stock configuration. The wings are clipped, a new and larger vertical tail is used and a small bubble canopy replaces the stockers' larger canopy.
Owned and flown by Tom Dwelle, Critical Mass is clearly a top contender and in the same class as Dago Red or Strega.

Race #11 Miss America - Modified P-51D

This aircraft has been on the racing circuit seemingly forever. Its new owner has completely revamped and spruced up this aircraft although he has retained the beautiful red, white and blue paint scheme. It's not known how modified the engine is but does not sound stock. Airframe modifications seemed to be limited to clipping the wings.
Miss America is owned and flown by Brent Hisey

Race #15 Furious - Modified Sea Fury.

This is another highly modified Sea Fury. Interestingly, this aircraft is powered by a Pratt & Whitney R-4360-63A. This highly complex 28 cylinder engine represented the largest piston engine to enter series production. Its 28 cylinders arranged in four rows of seven displaced a total of four thousand, three hundred and sixty three cubic inches. Due to the fact relatively little racing experience has been developed with this engine, modifications are quite few. The modifications seem to be restricted to changing the stock -63A nose case for a -59 nose case. The reason for this change is; -63A nose cases use an odd-ball SAE #70 spline propeller shaft. This means the only propeller available is the three blade Douglas Globemaster propeller, the aircraft originally powered by the -63A. So a -59 nose case, used on the Boeing KC-97, replaces the stock -63A. With an SAE #60 spline the -59 propeller shaft offers a far better choice of propellers even though the reduction ratio remains the same at .375:1. Like the R-3350 powered Sea Fury brigade, Furious uses a Douglas Skyraider prop. The R-4360 propeller shaft rides in three bearings; a massive rolling element bearing installed at the front of the nose case. This bearing handles thrust loads and radial loads. In the middle and at the rear are two copper/lead plain bearing that run inside the hollow crankshaft. At race speeds, up to 6Gs can be generated on the airframe. These tremendous loads are also imposed upon the propeller. Exacerbating the situation is the fact the prop acts as a huge and powerful gyroscope. Of course all these loads are transmitted through the propeller shaft and consequently transmitted into the crankshaft via the two rear propeller shaft bearings. These additional loads require the front main crankshaft bearing to be beefed up, otherwise it would suffer undue stress. Fourteen ejector exhaust stacks are used. This set-up siameses appropriate pairs of cylinders for maximum exhaust scavenging. In a similar fashion to Critical Mass, Furious uses two stock oil coolers, one in each wing. Again, spray bars are used to augment the oil coolers. Spray bar fluid is sprayed at the rate of one gallon per minute at 25psi. Being air cooled, the R-4360 need all the help it can get. As with all the top radial engined powered racers, a beautifully designed convergent/divergent duct is designed from the spinner and inner cowl. To further augment cooling, a controversial method is used. But before going into that, the basic cooling system of the R-4360 needs to be understood. Unlike single row or double row radials which simply deflect cooling air from front to rear, the R-4360 is made up of 7 plenums. Each plenum is formed by the space between each row of cylinders. Cooling air enters the cowl and is forced into the seven plenums where it is then directed through the cylinders, almost cross flow fashion. On the leading edge of the inside diameter of the inner cowl, seven spray nozzles are incorporated. At race speeds and powers, these nozzles spray water into each plenum thus getting atomized water directly on the cylinders. A stock R-4360-63A is rated at 3,800 horsepower. It would be safe to say that Furious has in excess of 4,000 horsepower on tap.
Furious is flown by Bill Rogers and owned by Bill Rogers and Dale Stolzer.

Race #21 Modified Hawker Sea Fury.

This stock looking Sea Fury is one of the few race aircraft to sport military markings. It is painted up to represent an RCAF aircraft. It is powered by a Wright R-3350-26WD, a Douglas Skyraider, non PRT engine. As with some other Sea Furys', it uses a carbon fiber copy of a Blackburn Beverly spinner. Even though this leaves the remarkably narrow annular gap of 1.5 inches for air entry into the cowl, cooling is not a problem. This is accounted for by the excellent design of the R-3350-26WD cylinder. It incorporates a forged cylinder head with all cooling fins machined in. The forging process offers a more structurally sound design without any of the limitations of a casting. The fins are closely spaced and deep, thus offering a large cooling fin area. The cylinder barrel has Wright's patented 'W' finning which, again, offers considerable cooling area and efficiency.
Race #21 is owned and flown by Joseph Thibodeau. Probably a good contender for the Silver or Bronze race.

Race #22 Merlin's Magic - Modified P-51D

This aircraft can truly be called a wolf in sheep's clothing. Belying its stock appearance, except for clipped wings, it sports a Dwight Thorn, balls to the wall race engine except it does not have G6 Allison rods. Even though the racers were just warming up on the last day of flying, Monday, September 10, it achieved its personal fastest qualifying speed at 432mph. However, it may have been pushed just a little too hard. After landing, a maintenance check revealed metal in the oil screen - a bad sign. Rather than risk a $150,000.00 race engine, it was wisely decided to remove the race engine and replace it with a stock Merlin.
Owned by Stu and Marilyn Eberhardt, it was flown by Stu and his son Bill Eberhardt.

Race #27 Miss Trinidad Modified Yak 11

Yaks are now becoming increasingly popular among warbird owners. This is due to their availability and relatively low cost compared to, say, a P-51D. The original Russian power plant is all but impossible to find so most are powered by US built engines. In the case of Race #27, a Pratt & Whitney R-2000. Normally, one does not think of an R-2000 as a race engine. However, when paired with the Yak 11, it makes for a good combination. R-2000s only powered a handful of aircraft, the most numerous being the Douglas DC-4 followed by the Canadair Caribou. Pete Law designed an ADI system for this racer which allows a manifold pressure of 52 in. Hg. Further helping power output are ejector exhaust stacks.
Owned by Sam Davis it is flown by Tom Camp.

Race #31 - Stock P-51D (Speedball Allice)

Little can said about this aircraft. Being a stock P-51D, the owner pilots simply wanted to go racing and have fun.
Owned and flown by Dan Vance and Art Vance.

Race #38 Precious Metal - Highly Modified P-51D

We normally think of P-51Ds being powered by Packard built Rolls-Royce Merlins. However, the last piston engine mass produced by Rolls-Royce was an even larger engine than the Merlin. Displacing 2,239 cubic inches, the V-12 Rolls-Royce Griffon entered service in the early 1940s. As good as the Merlin was, it still had some fundamental problems that would have been difficult to fix once the engine was in production. The Griffon recognized these problems and benefited from previous Rolls-Royce experience. Except for the pair of oil lines that feed the contra-rotating propellers, no external oil lines are to be seen on the Griffon. The profusion of external oil lines on Merlins have proved to be a maintenance headache over the years. Another key change made to the Griffon was to drive the camshafts from the front of the engine. Likewise, the single magneto is also driven from the front of the engine. This reduced the torsional vibration the cam drive and magneto drive gear trains are exposed to, particularly when driven for the rear of the crankshaft like the Merlin (see illustration). The Whittington brothers in Ft. Lauderdale, Florida, originally modified this aircraft for Griffon power. Engine modifications follow the same concept as the race Merlins. Precious Metal uses a conglomerate of parts from different mark numbers of the Griffon. The power section and contra-rotating nose case is from a Griffon 58. The two-stage supercharger is from a Griffon 74 which normally would normally power a British Fleet Air Arm Fairy Firefly F.R. Mk. IV and N.F. Mk. IV. An adapter plate is required to mate the 74 blower to the 58 power section. Like the full race Merlins, the after cooler is removed and replaced with a tube. All charge temperature issues are dealt with by massive doses of ADI. Griffon 58s were normally used to power the Avro Shackelton, a British maritime patrol bomber. The engine drove a pair of contra-rotating propellers. Precious Metal retains this propeller and nose case, albeit in modified form. First off, the propeller diameter is dramatically reduced and at the same time more pitch is used. The engine runs at 3,200 rpm, stock redline is 2,750 rpm. A modified speeder spring in the propeller governor allows the higher engine speed. All stock Griffons used up-draft carburation. Precious Metal uses a down draft Bendix PR 100 carburetor originally used on Pratt & Whitney R-4360s. For the Griffon application, a PR 100 is overkill to the point of being over carburated. However, this may be due to its prior life as a power plant for the Miss Budweiser Unlimited hydroplane boat racer. Jeff Neff, the Budweiser crew chief during the Griffon era, built three engines for the Whittingtons. One of these engine was a stocker for ferrying the aircraft. The boat racers used to turn their engines up to much higher engine speeds than aircraft racers. In the future, I would not be surprised to see a PR 58 carburetor replace the present set-up. A ram air scoop on top of the cowl feeds air to the PR 100. Converting to the PR 100 carburetor requires the use of an adapter plate that rotates the intake elbow 180 degrees in order to accommodate the down draft set-up. An additional adapter plate is required to mate the PR 100 carburetor to the Rolls-Royce intake elbow. A modified radiator is augmented by spray bars. As with full race Merlins, lubrication is enhanced via an additional pump driven off one of the accessory pads. The Griffon, like late model Merlins, used what is known as an end-to-end crankshaft lubrication system. This means the oil is fed in at both ends of the hollow crankshaft rather than the more conventional method of feeding oil to the crank via each main bearing. The advantage with end-to-end lubrication is that it eliminates the necessity for oil distribution grooves in the main bearings in order to feed the connecting rod journals. Precious Metal's Griffon utilizes the additional oil pump to feed extra oil into each main bearing. Not only does this provide enhanced lubrication, it also carries away heat thus preserving the life of the grossly over loaded bearings.
Of course, modifications are not restricted to the engine and propeller, Precious Metal also has a radically modified airframe. A small bubble canopy replaces the stock one, wings are clipped and overall aerodynamic clean up has been done.
Precious Metal is flown by Ron Buccarelli and is owned by Lake Air Inc.

Race #44 Sparky - Stock P-51D

Little to be said about this bone stock P-51D. No modifications. Like others in this class, the owner/pilot simply wants have fun racing around the pylons - and who can blame him?
Sparky is owned Steve Seghetti and flown by Brant Seghetti.

Race #45 Risky Business - Modified P-51D

This aircraft is another wolf in sheep's' clothing. Apart from clipped wings one would not guess that under the cowl sits a very potent Merlin. This aircraft is powered by a Rick Shawnholtzer built race engine. It races at 110 in.Hg. Abs manifold pressure at 3,400 rpm. The cooling system is augmented by three spray bars spraying on the radiator core; two for main engine coolant and one for the oil cooler.
Risky Business is owned and flown by Bill Rheinschild

Race #47 - Southern Cross Modified Hawker Sea Fury.

Powered by a Wright R-3350-26WD; with the exception of the engine, this is another stock looking Sea Fury. Painted up in Royal Australian Navy colors, this attractive airplane was another good contender for the Silver or Bronze. Relying on ADI, manifold pressure at race speeds is 57 in. Hg. and 2,900 rpm. Two oil coolers with spray bars keep oil temperature under control.
This aircraft is owned and flown by John Bagley.

Race #50 Miracle Maker - Slightly Modified P-51D

This P-51D is absolutely stock in appearance - even the wings have not been clipped. However, the engine has ADI which allows a manifold pressure of 100 in.Hg. Abs and 3,200 rpm at race speeds. It also features spray bars on the radiator.
Miracle Maker is owned and flown by Ike Enns.

Race #66 Fury- Modified Hawker Sea Fury

This stock looking Sea Fury has potential as a fast racer. Its exhaust system features eighteen equal length exhaust stacks. The exhausts exit through what appears to be a very modified cowl. Judging by the design, it is optimized to take maximum advantage of jet thrust and pumping effect to get additional cooling air through the cowl. It is powered by a Wright R-3350-26WD. Race power settings are; 57 - 58 in.Hg at 2,900 rpm. The engine picks up induction air via a pair of wing root mounted scoops. This arrangement is a throw back to the days when it was powered by the Bristol Centaurus. The Centaurus featured a pair of intakes to the supercharger located at mid height of the engine. Of course, the R-3350 has down draft carburation so this wing root location is not ideal for good ram induction. For the future it is planned to have a ram scoop mounted on top of the cowl. It's estimated that this simple modification will pick up another 3 in.Hg. Abs manifold pressure. A carbon fiber copy of a Blackburn Beverly spinner is used. The resulting annular gap of 1.5 inches is still sufficient to keep cylinder head temperatures down to a remarkably low 180 degrees at race speed and power.
This aircraft is flown by Howard Pardue and is owned by the Breckenridge Aviation Museum.

Race #81 Lady Jo - P-51D

This P-51D is a bone stock aircraft painted as a warbird.
Owned by Darryl Bond and flown by Robert Patterson.

Race #86 Czech Mate - Highly Modified Yak-11

In the 1960s and into the early 1970s, Unlimited aircraft racing was dominated by Darryl Greenamayer flying a highly modified Grumman F8F Bearcat powered by a Pratt & Whitney R-2800. This aircraft went on to gain the world's air speed record for piston driven aircraft. This record has subsequently been beaten. With the foregoing in mind it is surprising that more racers don't take advantage of this formidable power plant. The small and light Yak 11 airframe is ideal for the powerful R-2800. Little is known about the engine except that it was built up by Ray Anderson, owner of Day Air, a Pratt & Whitney overhaul facility. The engine is a commercial version of the R-2800, a CB 3. It is thought that Czech Mate may be using some of the go fast modification used by Darryl Greenamayer all those years ago. What is known is that it features ADI and a pair of Grumman S2 oil coolers which are situated behind the pilot. Cooling air for the coolers come in from scoops on the side of the fuselage under the cockpit canopy. A reduced in diameter Skyraider propeller is used. No cowl flaps are used, cooling air is augmented by the pumping effect of the ejector exhaust stacks. Induction air comes in from ram air scoops in the wing roots which is then ducted to the top of the engine into the Bendix PR 58 carburetor - again set up by Pete Law.
Czech Mate is owned by John & Marcia Moore and is flown by Sherman Smoot.

Race #87 Miss Merced - Modified Hawker Sea Fury.

This modified Sea Fury sports a spiffy looking flame paint job. Little is known about this aircraft except it is powered by a Wright R-3350 and drives a Skyraider propeller. Although it was intended top race, it was a no show due to an engine failure after Oshkosh.
Miss Merced is owned and flown by Jim Michaels.

Race #104 Russian Roulette - Yak-9

In the 1990s a number of newly built Yak 9s were made. Hard to say what category these aircraft would fall into. They were not restorations and yet it would be difficult to call them replicas. Made in Russia, they used the same tooling and manufacturing techniques used to make the originals in WWII. Even aircraft serial numbers continued on from the last one built in WWII. The main deviation from the original aircraft is the installation of an Allison V-1710 in place of the original M-107, a Russian development of the pre-war French Hispano Suiza Y series. As a soap box comment; did you ever know of the Russians coming up with an idea that they did not steal from some one else? Original engines are now all but unobtainable. This immaculate aircraft is powered by a Bud Wheeler built and maintained Allison. To date it is not highly modified, however plans for the future may include an engine with a G6 power section and various other modifications such as changing blower gears to boost manifold pressure.
Russian Roulette is owned by Shawn Carrol and flown by famous test pilot Dave Morss.

Race #105 Spirit of Texas - Hawker Sea Fury

This stock looking aircraft, except for the Wright R-3350-26WD engine, has a few modifications worth looking at. It is another immaculate restoration to come out of Nelson Ezell's shop in Texas. At race speeds the engine is run at 57 in.Hg. Abs and 2,900 rpm. It retains the stock aircraft's single oil cooler. However, the oil cooler installed in this Sea Fury uses a fin and tube radiator matrix instead of the honeycomb matrix installed on the original aircraft. Honeycomb radiators and oil coolers were very common in the early day of cars; and aircraft continued to use honey comb oil radiators right up to the end. The honey comb radiator is simply a bundle of tubes sweated together. Oil flows around the outside diameter of the tubes and cooling air flows through the center of the tubes. The big advantage with this type of cooler is the fact it can withstand extreme pressures, unlike fin and tube radiators. Although installed on the scavenge side of the oil system, one would think that the oil cooler would not be exposed to high-pressure. Under most circumstances, that would be a correct assumption, however, under cold conditions oil can congeal to the consistency of gel. This can generate undesirably high-pressures which, on occasion, can burst a cooler. Nevertheless, Spirit of Texas has opted to use a fin and tube radiator with its enhanced cooling capability.
Spirit of Texas is owned and flown by Stewart Dawson.

Race #111 Stock Late Production Yak 9

This aircraft did not appear for the race line up. It appears to be a stock late production Yak 9 powered by an Allison.
Owned and flown by Brent Hisey

Race #114 Argonaut - Modified Hawker Sea Fury

The Sanders brothers, Dennis and Brian, are renowned experts in the field of Sea Furys and aircraft restoration in general. Argonaut is flown by Dennis. It is powered by a Wright R-3350-26W driving a Douglas Skyraider propeller. This immaculate aircraft has relatively few race modifications. To keep oil temps under control, spray bars are used on the oil cooler. Race power is typically 55 in.Hg. Abs at 2,900 rpm.
Flown by Dennis and Brian (they alternate each year between Argonaut and Dreadnought) Sanders and owned by Sanders Aircraft Inc.

Race #117 Bad Attitude - Modified Hawker Sea Fury

Apart from its Wright R-3350-26W engine, this aircraft is close to stock. As a concession to keeping oil temperature under control, spray bars are employed for the oil cooler. This attractive aircraft is painted up in the colors of the RCAF. A real Beverly, aluminum spinner is used.
Owned and flown by Bill Rheinschild.

Race #232 September Fury - Modified Hawker Sea Fury

This is another balls to the wall racer designed, built and maintained by the Sanders brothers. Powered by a Wright R-3350 PRT engine, it has tremendous potential. Unlike Critical Mass, the other Sea Fury powered by a PRT engine, September Fury simply installed a PRT engine and removed the PRTs. Whilst this will work for producing a prodigious amount of power, their is a size and weigh penalty by not incorporating an adapter plate between the power section and the blower section. This engine also retains the direct fuel injection used on most PRT engines. Two massive nine cylinder fuel injection pumps are mounted on the 'master control' unit, a mass air flow measuring device that replaces the carburetor. Fuel is injected right into the combustion chamber. Pete Law designed the ADI system (from an early model R-2800 system). Pete also designed the unique oil cooling system on this aircraft. Rather than use a conventional air to oil system, Pete designed a so-called 'boiler system', similar to the one used on Darryl Greenamyer's Bearcat in the 1960's. Using a massive Douglas DC-7 oil cooler with 7,000 tubes, it is mounted in the fuselage, under the pilot. The cooler is immersed in ADI fluid. As the temperature of the oil increase, heat is rejected through the ADI fluid and as the fluid boils, steam and gasses are dumped overboard. ADI fluid is used because of its low boiling point of 170 degrees F. Although this reporter did not get definitive power settings, it is safe to say that under race conditions the engine is operating in excess of 60 in.Hg. Abs manifold pressure and over 3,000 rpm. Clearly, this aircraft is another top contender in the Gold battle. A Beverly style carobn fiber spinner with a 1-1/2 inch annualr gap is used.
September Fury is owned and flown by Michael Brown.

Race #711 Blayak Moose - Modified Yak 11

One would normally think of a Yak 11 powered by a V-12. Apparently some were powered by radials. Blayak Moose is powered by a Pratt & Whitney R-2000. It qualified at 332mph indicating it is a basically stock engine. It does not have ADI - yet. It is thought that the propeller may be modified from a North American T-28.
Blayak Moose is owned by Dr. Kent Carlo Magno and is flown by G.P. 'Sam' Richardson.

Race 911 September Pops - Modified Hawker Sea Fury

This stock looking, except for the Wright R-3350-26W engine, is a two seat version of this aircraft. The German air force used a number of Hawker Furys' up to the 1970s as target tugs. September Pops is, in all likelihood, one of these former German aircraft. Like several other Furys', September Pops uses a Blackburn Beverly style spinner made from carbon fiber resulting in a 1.5 inch annular gap for cooling air to enter the cowl. It also uses F-104 wheels and brakes. This is another popular modification that gets away from the original and idiosyncratic British pneumatically operated brakes. In fact few, if any, Hawker Sea Furys use the original wheels and brakes.
September Pops is flown by Randy Baily and owned by Fury, Ltd.

Ramp Rats

A question that often arises is; why don't the top racer use nitrous oxide. As Bill Kerchenfaut jokingly put it '....we are already good at blowing up engines, why would we want get better at it..!!?' With the stresses already imposed upon these engines, it simply would not be practical to use nitrous - but it has been tried. Nevertheless, when running at 140 in.Hg. Abs manifold pressure, even injecting all the ADI the engine can stand will not quell detonation. The next recourse is to use a high performance number fuel. The top racers are burning 160PN fuel. Even more exotic fuels such as Triptane would work even better, but this much desired fuel is no longer available.

The foregoing synopsis is overly brief. For a thorough description, each of the top racers could easily fill a book.

One has to admire the professionalism demonstrated by the owners and crews that work on these ultimate hot rods. Running an aircraft on the ragged edge of destruction, as many do, takes skill, nerve, determination and the finest possible equipment maintained by people who are at the top of their game. Shadetree tactics simply do not work with these aircraft. Incredible ingenuity and quality of workmanship abounds in the pits at Reno. This is what Unlimited racing is all about.

 Back to top