And the winner is ...

Bob Axsom · #1 07-27-2007, 11:03 AM

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

Bob Axsom

groucho · #2 07-27-2007, 11:47 AM

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 · #3 07-27-2007, 11:50 AM

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

Ron Lee · #4 07-27-2007, 12:13 PM

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 · #5 07-27-2007, 12:48 PM

Quote:

Originally Posted by ronlee

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 · #6 07-27-2007, 01:21 PM

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 · #7 07-27-2007, 02:21 PM

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 · #8 07-27-2007, 06:37 PM

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 · #9 07-28-2007, 06:32 AM

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 · #10 07-28-2007, 07:04 AM

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