Bob Japundza's Report

A flight home from Oshkosh 2004
I was fortunate enough to be able to keep Mark's airplane for a few days to ferry it back to Taylor from OSH, and wanted to pass on some of my impressions.



First off, I have to admit that I’m a little biased. Having flown my last 600 hours in RVs, I’ve grown quite accustomed to them, and their delightful handling characteristics. It’s a pretty high bar to measure against, especially handling-wise. The RVs really have no match in that regard, with the exception of the F1.

The F1 kicks ass in a pretty serious way. It’s a MACHINE. The new wing adds quite a bit of good to the whole, some of which is at a compromise which I will discuss later. I hear all the time about guys trying to compare a RV-8 to the F1 when making a purchase decision. I really don’t think there‚s much to compare other than both handle nice, both have two seats, one is a hell of a lot more fun and faster than the other, and, you won’t see a dozen of them at any given airport.

Anyway, on to my observations:

In roll, the stick has sort of a high-friction feel near neutral; if you nudge the stick either way an inch or two, the airplane rolls in that direction but the stick feels almost like there’s some sort of friction lock on and doesn’t center once pressure is relieved; you have to move it back to center.
Further over from neutral, and the roll rate gets responsive, similar in roll rate/feel at higher deflection to the RV’s. Since Mark’s airplane has the prototype ailerons and push-pull tubes, it sounds to me like this issue may already have been fixed with the changes made to the control linkages and the ailerons in the production wings. A new set of production wings will be installed very soon on Mark‚s ship to test the new setup. These have integral gap seals and the lever arm distance is increased from the pivot point. If it stayed the way it is on the prototype set it wouldn’t be objectionable, just takes some getting used to. Again, this is coming from an RV driver, the guys who are used to flying spam will think its light as a feather in roll. Sounds like the production parts may do the trick in making it RV-like in roll.

Slow speed: this is where the new wing really shines, and it’s just as important as going fast. It honestly handles like a 150 Cessna in the pattern; very easy to land. The no-power sink rate is nowhere even close to the square wing; it’s like a glider in comparison. The airplane slows down easily, and feels rock solid at slow speed. On approach, trim for 70kts, the airplane tends to stay at trimmed speed regardless of power. So, if you change power, no trim changes are required. RVs are sensitive to power changes and holding speeds in the bumps takes a bit more work than it does with the Evo. Part of this is because the F1 in general has higher wing loading. However, there’s no doubt in my mind the new wing handles better the square wing when slow. In the event of an off-airport engine out situation, the Evo wing could definitely make a positive difference in survivability. Landings on my 2500’ grass strip were no problem. I didn’t try any short field landings, but was easily getting stopped in the same distance I would in the RV.

I routinely pegged the VSI at 3000fpm on takeoff after a short level-off in ground effect. 2200-2300 fpm was more common. On climbs to 10,500, I would see 1800fpm just before levelling off. Climbing to 10K in five minutes is awesome, awesome, awesome.

I typically saw an average of 178kts down low in the bumps at 2100-23” @ 12.3gph on three-way gps runs. Flat out I saw 225kts groundspeed, but had a little tailwind so there was nothing scientific about that run. It seemed to go faster up higher. At 10,500, I ran 2100-22” @ 10.6gph and consistently saw at greater than 195kt ground speeds in varying winds. On my trip back to Taylor from west of Indianapolis, made it there in exactly 4:00 flight time with an average speed of 188.25kts, including two climbs to 10,500, landings, and a slowdown for the bumps down low near Taylor. Pretty dang good, considering I was getting 22mpg and the engine was humming along at a nice low rpm. Flying from OSH to Indy with Jim Winings (who was flying my RV-6), I was burning less gas in the F1 (8.8gph) at RV speeds, which are typically 9.5gph @ 165kts.
If I put the hammer down I could make the RV next to me seem like it just chopped the throttle.
With the new wing, the length of the mean aerodynamic chord is shortened. The center of lift is ~4” forward of the square wing. Because the MAC is shortened the cg range is smaller; because the CL is moved 4” forward over the square wing, the cg moves aft. It was moderately light in pitch as it was solo with half to full tanks, really about just right in feel. Mark told me if I wanted to take a passenger up they had to weigh under 200lbs, and to expect it to be light in pitch. Keep in mind with the riveted trailing edge elevators, the stick felt pretty heavy before the wing switch, which it should with that type of trailing edge. The fix for this is bring the cg forward: heavier engine, Hartzell three-blade prop, move the battery forward, etc. This also can open up some new possibilities with engines, which weren’t available before, due to cg limitations in the opposite way (nose heavy). I would have to think an angle-valve 540 is now possible. All of this has yet to play itself out; I expect that with the new wing some aft-cg carrying capacity will be lost compared to the square wing, even with a heavier engine. One thing I was not used to was seeing the wingtips dance in the bumps, and a couple of times I slowed down just to be on the safe side. Probably not an issue, but it is a new wing and I was sure that I
didn’t know how strong it is. I think seeing some data on a loaded wing like a FEA analysis, fatigue data, etc. would be helpful to know other than just somebody’s word that it’s strong enough.

Overall, I like the new wing, but I like the square wing too; its hard to beat. I love the stunning looks of the new wing, and really like the slow speed handling. It definitely rode like it was on rails compared to the RV, but that’s the case even with the square wing. The question I kept being asked was, “would you get those wings if you had to do it over?” I don’t know, probably. Would I upgrade? At this point, the wing I have is plenty good enough for me. The square wing does quite well but it too has its own compromises. I strongly believe the only compromise of the new wing even after more development work will be cg-related, but will likely be more than acceptable as refinement to the airplane happens.

Regards,
Bob
#80

Addendum to Report
Apparently there has been some misinterpretation about my comments regarding the wing tip bobbling.  First of all let me quote myself here so you don’t have to look for it:One thing I was not used to was seeing the wing tips dance in the bumps, and a couple of times I slowed down just to be on the safe side.  Probably not an issue, but it is a new wing and I was sure that I didn’t know how strong it is.  I think seeing some data on a loaded wing like a FEA analysis, fatigue data, etc. would be helpful to know other than just somebody’s word that it’s strong enough. First off, seeing wingtips moving around in turbulence is not unusual in many airplanes I’ve flown or rode in, with the exception of RV’s.  I’ve seen the wingtips bounce around in a C-177 I used to fly.  On the way home from Austin on a B-737 the wingtips were moving up and down by a foot during the descent into Indianapolis.   Last year I flew an old 310 with tuna tanks, the wingtips bounced around 4-5” or so.  99% of my last 600 hours as PIC has been in RV’s so I’ve gotten used to not seeing it. In the F1, when I slowed for turbulence in descents, I was well up into the yellow arc, the wingtips bouncing around (no more than 1⁄2” deflection).  Slowing down for the bumps is standard operating procedure for me in my RV.  The difference which I want to clarify, is I am not used to wingtip movement in RV-type aircraft as they have short wings that do not visibly flex (I’m sure they do) but its not obvious.  Same goes for the standard F1 wing.  While I was flying Mark’s airplane I had no idea how accurate the pitot system was and I was not familiar with the load limitations of the new wing, so  I played it safe.  Being a pragmatist I do stand by my statement that yes, I would like to see some data on the strength of the wing.  Not that I doubt the F1 wing strong enough, but it would be nice to know.  It sure as heck looks strong and judging by my eyeball comparisons with other metal high-performance homebuilts (SX-300’s, Venture’s, etc.) which operate at much higher speeds and wing loadings; it likely has more than adequate strength for the mission profile of the F1.   
Regards,Bob