[Bob Axsom]

John Huft in RV-8 Race#18. 235 mph average from Daton to Oshkosh (that's west bound folks).

Bob Axsom

 

[groucho]

Ok, that's fast! That plane is registered with an O-360-A1A. Nice lookin' plane & that tinted canopy looks sexy too. Nice tail wheel pant!!

 

[brianwallis]

Details

WOW.... Does anybody have any details on what makes it so fast?.... He is cousins with Tracy Saylor?
Best
Brian

 

[Ron Lee]

John Huft

I found his website and he apparently has 10:1 pistons that should help some. But he must have done beaucoup more to get that kind of speed. Since he lives in Pagosa Springs (pretty airport), I may have to fly down there to get some advice.

 

[gmcjetpilot]

10:1 pistons, not key to speed?

I found his website and he apparently has 10:1 pistons that should help some. But he must have done beaucoup more to get that kind of speed. Since he lives in Pagosa Springs (pretty airport), I may have to fly down there to get some advice.

It's the flame paint job that gives the speed not the 10:1's. Seriously 10:1's is not a speed secret or key to speed. If your RV speed is so-so and you slap in 10:1's you will be disapointed with the results if the idea is massive increase in speed.

From my eye the speed comes from, in part from:
-Prop (Hartz BA)
-cowl/plenum (James)
-induction (custom)
-exhaust (4-into1)
-ignition (lightspeed)
-rigging and attention to detail

Speaking of Tracy Saylor a few years ago (Tracy, a Californian w/ super fast RV-6). He went to 10:1's after a long course of other modifications to his already fast plane with top place race finishes. He got very little speed increase. You might expect a few ponies more for HC pistons, but that equals only a mph or so, may be, at ++200mph. You can gain more speed with aerodynamics (drag reduction) than raw HP. Don't get me wrong, HP is good, can't hurt speed, but as I said Tracy Saylor did most of his racing with stock pistons and felt HC pistons where NOT a must. After his engine up-grade to 10:1's, he told me he regretted doing the high compression piston mod as not worth the effort. Sure, if starting a scratch engine build-up, consider HC for your boy racer, but with gas going to 92/95 octane, sticking w/ 8.5:1's might be a good idea? Unlike a car, HP is not as critical for top speed as efficiency of airframe, prop and cooling drag.

BTW way John Huff's site is http://www.lazy8.net/rv8.html. I talked to him. Nice guy and some cool experimentation with induction, which he claims gained amazing increase in manifold pressure, thus HP. From his race result, it's hard to doubt. His unique induction set-up is on his site. BTW its a vertical induction system not horizontal system that some think is better for speed. Remember the air has to make at least on 90 degree turn to go up into the cylinders.

For you guys thinking of PROPS? John has a good write up on Hartzell (old 7666 blade), Aerocomposite & MT. He tired them all. He NOW flies a Hartzell BA, and that IS a speed secret.

The other obvious things as I mentioned above are: James Aircraft cowl/plenum and 4-into-1 exhaust. The latter, 4-into-1 is almost free HP with little or no down side (but cost). It's the gift that keeps on giving. The only down side I heard of with 4-into-1 from one gent is more floor drumming? Installation is harder than X-over (may be), but with off the shelf units now, the fit is worked out for plug and play.

These are the obvious secrets to my eye, along with a "straight airframe" rigged properly, where aileron is not fighting gear leg fairings and so on. There is "close enough" rigging and than there is perfect. Every little bit helps at +220 mph. They're other "secrets", but I am not going to tell you all of them.

 

[atreff]

More RPM?

In speaking with Tracy approx 6 years ago at SnF, I think I remember him telling me that he turns in the 3000+ RPM.

IN talking to Monty Barrett, he indicated that the airshow performers and racers routinely turn their Lyc's and Conti's up to 3600 RPM-fastest way to more ponies, many more ponies. And then, TBO becomes more like 250-500 hours.

I agree with George, HP increases are very disappointing payoffs in speed for all the expense. HP cubed gives speed increases? That's a ton of HP for little speed.

Art in Asheville

 

[JoeLofton]

Kent Paser's Book

I attended a forum at OSH this week where Kent Paser talked about performance improvement mods to his Mustang II (O-320 Lycoming) over a number of years. All told, he increased his top speed by 64mph, cruise speed by 60mph, climb rate by 800fpm, service ceiling by 8,000ft. For economy cruise, the fuel burn was reduced to 4gph (12,000ft, 2200rpm, 173mph TAS).

Aerodynamic improvements accounted for 49mph; change from 7:1 to 8.5:1 pistons, with some timing advance, accounted for 2mph.

Kent is an aero engineer, and his experience is well documented in his book, "Speed with Economy". Contact info is Paser Publications, Kent Paser, 5672 West Chestnut Ave, Littleton, CO 80128, phone (303) 904-3417.

Joe Lofton

 

[Bob Axsom]

It is interesting how 2 mph is dismissed

2 mph is a lot of speed gain and if the money is available, I don't know any racer that would pick and choose which speed gain they would ignore. When the oportunity comes I will get blended airfoil prop blades even thought the cost is very high. More horse power? oh yeah any way I can get it. With the Hartzell constant speed prop you cannot rev up to the high numbers but I have my governor limit screw backed out to get the available 2,720 rpm. I have come around to the point of view that if you are going all out for speed the fixed pitch prop is probably the way to go. I communicated with Barrett Precision Engines and the thought was with my O-360-A1A I am limites to something in the 9:1 compression range which he said would give me 7-8 more hp. There are still several aero things I can do but in my opinion the prop is where I could get the biggest increase in speed. In addition to the photo I took at the start of this thread I took many of John's external refinements close up. I will just say he paid a lot of attention to detail. Some of the cleanup probably only got him a 10th of a knot but he didn't ignore anything.

Bob Axsom

 

[pierre smith]

Gap seals?

Bob, and others,
Dave Anders has gap seals on his record breaking-4, plus canoe type fairings on the aileron hinges and fuel drains. I asked quite a while back about gap seals and didn't get any decent answers. What do they do to control pressures, if anything. I heard that the friese type ailerons get heavy with gap seals. That wouldn't matter if you're into speed anyway.

I built a Cassutt F-1 racer in the mid seventies and when I added elevator gap seals, the airplane was noticably faster and I had to hold forward elevator until I shimmed the front spar of the stab with washers. Do you have gap seals on Bob?

Regards,
Pierre

 

[Bob Axsom]

No I don't

I have seen them on several planes but I haven't gone there myself yet. I have seen several including John Huft's RV-8 that have the hinge cutouts in the leading edge of the control surfaces closed by various techniques but I haven't worked out how I want go about that yet either. "Noticably faster" from you gets my attention for sure.

Bob Axsom

 

[Nuisance]

Speed = Efficiency

Thanks for all your kind words. I did have a heck of a run this year, and a few knots of tailwind didn't hurt anything either.

On Friday morning at OSH, Dick Keyt, Jon Ross, and I gave a forum on the race, and I gave away all my speed "secrets". They are not really secrets because most of them have been on my web site all along. See...

http://www.lazy8.net/speedmods.htm

and other pages. They are also not secrets because I learned many of them from Dave Anders, Tracy Saylor, and Rich Jankowski. They have always been generous in sharing what they have learned, and I intend to continue this tradition. Ron Lee and anyone else who would like to drop in and talk, you are welcome.

George Jetson is close on many things, but it has been a while since he has been to my website. I have changed from the elbow induction to an ECI cold air intake system. When I did this the 4 into 1 would no longer fit, and in the face of no support from Sky Dynamics, I went to Larry Vetterman for a 4-pipe exhaust. His support and willingness to work with me has been outstanding, and in my opinion there is no performance difference between the 4 into 1 and the 4 pipe. Since I had to change both at once I can't separate the results, but the total was a 3 knot increase in cruise speed at 9000 ft. density altitude.

I will make some more posts on this subject as I recover from the trip and get caught up, but I would like to state the following...

1. I ran the race wide open, full throttle, 2700 rpm.

2. I used 27.5 gallons of gas. The guys I beat all used more gas, and that is important. Drag reduction is the key. Look at the results and you can see an EVO rocket with IO-540 and Dick Martin's IO-390 angle valve are included even though they were in another class..

Results

More later, John

 

[Alan Carroll]

"Nuisance" speed secrets

John is perhaps being somewhat modest about another factor in his success, a superbly detailed airframe. The basic construction quality is excellent (resulting in several awards), and I'm sure he's tweaked the alignment of control surfaces and other components to be near perfect. Some other details I noticed: custom aerodynamic fuel vent masts, plastic gap-filling spacers for the aileron hinges, hand-carved (?) "canoe" fairings for the hinges, fuel drain fairings, very clean tailwheel fairing, custom wing-fuselage intersection fairings, etc.

Of course, the most important secret is no doubt his special roll of red tape, used to seal off the oil filler door and a few other seams before the race. I copied this on my plane, and I'm sure it was good for at least 10 knots...

 

[DanH]

<<plastic gap-filling spacers for the aileron hinges>>

John, can you tell us a little about that? Got a picture?

 

[Ron Lee]

Nuisance speed improvements

I noticed some past race speeds for John's plane on his website and it appears that in the last year or so he has made some dramatic improvements. I would agree that the picture of his plane posted does suggest "clean and fast."

I also checked race results and John is faster than the plane previously known as "The fast one."

 

[Bob Axsom]

WOW! This Is Getting Pretty Elite

Allan Carroll was third in the race averaging over 220 mph. I thought I was the only one going over John Huft's airplane for speed detailing but Allan mentioned everything I saw. I took 8 or 9 photos of John's plane shamelessly trying to capture details and I photographed Allan's RV-8 (Race 12) as well. I tried several times to post the aileron hinge fairing photo but Imageshack can't get it for some reason. I will e-mail them to to Doug and perhaps he can post them.

Bob Axsom

[ed. Here you go with the #12 image, Bob]

 

[scottg]

I noticed some past race speeds for John's plane on his website and it appears that in the last year or so he has made some dramatic improvements. I would agree that the picture of his plane posted does suggest "clean and fast."

I also checked race results and John is faster than the plane previously known as "The fast one."

Be careful when trying to make speed comparisons from one year to the next. These speeds are average ground speed, not TAS. In the past, the race was flow with a headwind. I?ve been told this year had a tailwind.

What is truly impressive is the 14 mph speed difference between 1st and 2nd place. That?s the same margin that separates 2nd and 9th place.

 

[Bob Axsom]

A little bit more actually

Be careful when trying to make speed comparisons from one year to the next. These speeds are average ground speed, not TAS. In the past, the race was flow with a headwind. I’ve been told this year had a tailwind.

What is truly impressive is the 14 mph speed difference between 1st and 2nd place. That’s the same margin that separates 2nd and 9th place.

2nd place was Jon Ross at 221 mph who had beaten John Huft before in this race. 9th place was Jean-Pierre Verdier in an RV-7A. Jean-Pierre told those of us at the dinner at the Dayton Engineering Club the night before the race about assembling his engine and building his airplane. He said "I am going to take it easy and baby my engine." Maybe you are talking about 8th place at 207.13 in an RV-6A. I can assure you on the best authority that that old guy was doing everything possible to get every micromile per hour out of his airplane.

There was a tail wind component this year on the first leg of the race which is the long 303 degree leg of 185 nautical miles from Dayton Wright Brothers Airport (MGY) to Kankakee (IKK) in Illinois. The rules this year imposed a minimum en route altitude floor of 2,000 ft MSL. At Kankakee all racers were to make a low approach down runway 34 (preferably below 200 ft. AGL) past the first intersecting taxiway on the left then climb on course to turn two. Even with a shallow climb covering several miles the speed reduction in that climb was many kts.

At the briefing the night before the race a navigation wrinkle was made when another turn point was added before the one at Rockford (RFD), Illinois. The racers were to proceed to GILMY intersection at the race floor or above (2,000 ft) before turning to the third turn at RFDs runway 07 intersection with taxiway H. This created a flight planning problem for some. GILMY intersection is not in all GPS databases, it is not on sectionals or IFR enroute charts. It does appear as the localizer outer marker on the ILS Rwy 01 chart for RFD. Transferring the location to a sectional was tedious and not the most precise of tasks but when cross checked with the coordinates given verbally at the briefing, it was close enough to be confident that the depiction was correct and the course line was drawn.

The flight to GILMY required a 19 degree right turn to a track of 322 degrees for 85 nautical miles. After leveling off at 2000 ft the speed slowly built up but it was about 5 kts slower than the first leg for Race #71. No altitude change at GILMY but there was a 32 degree right turn to a track of 354 degrees for a short 5 nautical miles to the next turn at RFDs runway 07 & taxiway H.

The last race leg was supposed to be 90 nautical miles on a track of 020 to the private strip by Quadgraphics at Lomira but there were two complications.

First, the City of Rockford was a very sensitive area. All racers were told to remain clear of the downtown area by remaining west of the river until clear before turning directly toward the finish line so the length of the final leg depended on how much margin a pilot provided to stay clear of the city. Legally, the floor of the race provided sufficient altitude over the city but disqualification was the penalty for violating this no-overflight rule.

Second, all racers had to climb above 2,500 ft before crossing Beloit, Airport; again with disqualification as the penalty for violating this rule. This was imposed by the FAA directly so the penalty of disqualification may not have been the end of the problems for a violating pilot.

On this last leg the air just seemed to die and the 500ft climb requirement bled off speed that didn't come back.

At the finish line a significant left diving turn has to be made for a low pass up the center of the runway to the finish time line. Some speed may have been lost in that maneuver but the numbers are so far above normal that there is no way to tell.

The weather was as good as one could hope for and there was tailwind for most of the race but you should not think it was a straight 365 nautical mile flight with a constant tail wind and no deviations. I know that a lot of work went into getting those speeds up to where they were even though it must be acknowledged that tail wind was a factor where head winds are the norm.

Bob Axsom