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  #11  
Old 11-19-2007, 09:08 AM
F1Boss F1Boss is offline
 
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Hey Fellas:

Be careful what you read on the internet -- from my experience I'd suggest confirming almost anything you hear!

Evo wing: This wing was designed to fit the M-1, to be built by HPAI. SO, it was designed for a heavier gross weight ship from the start, which gives it a huge margin on the Evo -- a good thing in most cases, except in the weight category: it is approx 50 LBS heavier in comparison to the Sport wing. Oddly enough, performance didn't seem to suffer, tho I'm sure a lighter wing would have given even better numbers. The top speed increase was exactly what the engineer had predicted (5%), but the slower stall was the part that surprised me, tho I should have seen this coming (tapered wings are more efficient at higher alpha angles -DUH!)

Our investigating of using the 230XX instead of the newer foil showed a similiar increase, if we fudged the figures enough. I was worried about the stall, knowing how the RV doesn't really talk to you before it lets go, so we went with the newer foil which gives plenty of warning.

The additional problem with the wing, derived from its intention to be used with a heavier gross weight ship, is its area: simply too large. We ended up with a bit over 100SF, where about 85SF would have been optimal for cruise at altitudes below 12000MSL. I liked the slow approach and stall speeds, and a re0design would have raised the price of the wing about 50%, so we stayed with what we were handed.

As for the Questair Venture wing, it did start with a 230XX foil, but it was changed from that rather quickly (stall characteristics again!). Do your investigating before you report! The narrow chord/CG range of this wing is OK with a SBS design, but would not work on a tandem arrangement for those same reasons. The Venture wing uses similiar PERCANTAGES of chord for CG range as are used on the RV series, but the mean chord is very narrow, so the resulting CG range is also very narrow; it just won't work on a tandem arrangement where the pilot sits in the front seat. Trivia: Do you now the WW2 era B-24 has a 9" CG range, again due to its narrow chord wing??!!

Evo airfoil:
The CZ engineer started with the MS(1)-313, but we ran into the same thing everyone else using the new foils did: high pitching moment. We flattened out the aft camber to the limits of the aileron and flap design, and this gave us a foil with an approx 60KT wide trim band. This trim band talks to the pilot in terms of trim tab adjustments: the pilot more or less trims for load once in climb, and never touches the trim again until the ship is slowed for approach. I have not heard from any pilots who do not like this particular personality trait.

BTW: Glasair uses the LS(1) or GAW foil; Lancair/Columbia and Cirrus use the NLF foils, again all are modified in the TE area to reduce pitching, and also at the LE (Lancair and Cirrus) to tame the stall to certified limits.

The MS(1)-313 is supposedly about 40% laminar, where the 230XX is about 20%; more attached flow is probably better in just about any case. We haven't seen degradation effects that compromises performance to a large degree -- NASA says it (and other later-designed foils) perform more like the 230XX, or other non-laminar foils, with bugs on the LE.

Current sit rep: We had to stop dealing with the CZ boys in the spring due to the dollar/euro slide. The currency situation at present allows us to produce parts and QB kits here in the USA again, but the biggest positive aspect of this is that I get to make changes to the Evo wing to further optimize it for cruise flight, and attend to the slightly slower roll rate.

Stay tuned -- I think you all will appreciate the Evo II, both in terms of performance and price. I'm not quite ready to make a formal announcement of the new developments, but we are close....

Carry on!
Mark
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  #12  
Old 11-19-2007, 09:09 AM
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rocketbob rocketbob is offline
 
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Some of the most successful aircraft designs utilize the NACA 230XX airfoil, RV's, Bonanza's, Swift's, F8F Bearcat, Corsair, etc. just to name a few.
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  #13  
Old 11-19-2007, 01:21 PM
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Bill Wightman Bill Wightman is offline
 
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Default Airfoil choice

OK y'all, I know the Five Digit (NACA 23XXX) airfoils are used in abundance. But I also know - and yes I have done the research - those airfoils were done by NACA (not NASA) in 1931 in an early effort to get rid of pitching moment. In fact, all the NACA airfoils were "lab rats", never specifically designed to be fitted to any airplane. The designers of the day simply used what NACA doled out. The research was mandated and funded by the US congress following WWI when the US was falling behind in aviation technology.

We now know that negative pitching moment is not a problem to control and does not lead to large drag numbers by way of trim loads on the h-tail. There's more than one way a designer can move static margin, CG, and Cm/Alpha curves around to fit his needs. Pitching moment is only one ingredient in the soup of variables that must be addressed.

Bottom line: 70+ years have lapsed since the 23XXX was done. I know, I know there's a whole slew of airplanes that use it. But we've had better since WWII and MUCH better choices these days. In fact, just about all modern aircraft don't need to run a "stock" airfoil the government hands out. Now, a competent designer can cook up a mission-specific section on a desktop computer in just a few days.

I bet the EVO-II is worth waiting for!
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Last edited by Bill Wightman : 11-19-2007 at 03:42 PM. Reason: correct typo
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  #14  
Old 11-19-2007, 07:56 PM
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mark manda mark manda is offline
 
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I gave a guy a ride in my Rocket early Saturday morning around the Taylor,TX race course and he said he had the last set of EVO's(and he wasn't giving them up) so this may all be moot. You can buy an EVO for $250K or

you'll have to wait for the EVO II!
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  #15  
Old 11-19-2007, 08:49 PM
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gmcjetpilot gmcjetpilot is offline
 
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Default The 230XX airfoil is faster than a LS airfoil?

Quote:
Originally Posted by Bill Wightman View Post
But - it was the airfoil on the S**** Playboy that Van reverse-engineered in metal. So we've inherited it here. My old RV4, for one, had just about zero prestall buffet.

Never the less, the old Five-Digit airfoils abound and their sharp stall is engineered out on certified aircraft with planform bandaids, leading edge devices, twist, etc. It has served us well over the decades but I for one wouldn't revive it in the face of 60 year improved technology.

You all will have to wait a bit longer to see what I have in store for the RV world...
Well you sound like a real Aero guy, I have only stayed in a Holiday-Inn and sat next to a real Areo guy.

Stalls - I think personally the stalls on RV's are very mild; in fact they don't want to stall. I agree the buffet is nominal or minimally. Fair to say sharp but not dangerous. RV's need stall strips (to get them to stall) to do good snap rolls. If you want to get into MODERN than get an AOA device to warn you of impending 'danger'. For a plane that stalls in the low / mid 50 mph range, slower than a C-152, the danger is small.

The laminar airfoils are not known for mild stall properties. They may warn you but they break like a sob. The Piper Tomahawk uses a GA (laminar) airfoil. I flew one for 500 hours and taught in them. They had weird and unpredictable stall characteristics, like a snake bite, breaking right or left abruptly. I like the T-hawk a lot overall, had good times, but stalls are not a stong point. It flew fine but the T-tail added some more weird control issues both in flight and landing you had to adjust for.

MODERN - I don't totally buy the "modern" argument when presented with it. Auto engine guys say MODERN, yea but its heavier and slower. Again you know more about Aero than I, but in my experience with LF wings, they promise a lot but never really deliver. Two-dimensional data rarely is accurate for an actual wing, and other factors come into play, which I'll mention below.

LIFT? (l/d)
The Glasair III ( LS(1)-0413 airfoil) lost lots of sales when other planes out performed it, the Lancair and QuestAir to name two. The QuestAir beat a Glasair III silly with less HP. The QuestAir used the 230XX airfoil, 23015 root/23010 tip. Stoddard was confused. It's laminar airfoil was MODERN, it should have less drag, RIGHT? The reason was the LS airfoil had less drag but also made less lift. So the LIFT/DRAG for the QuestAir (230XX) was over twice the LS airfoil of the Glasair III in cruise condition, OVER TWICE! Stoddard made it worse by filling in the lower trailing edge cusp to get the stick forces down, decreasing lift performance further. It was a bad choice of an airfoil. No doubt there are better laminar airfoil choices Glasair could have made; still, modern is not everything. Ever fly a Glasair? They are fast but don't handle as lovely as a RV, especially in roll with the RV's 'frise' ailerons.

BOTTOM LINE
LF airfoils do have a narrow operating range, and they do have more pitching moment and less lift in many cases, apples for apples. Real airframe and real world performance will be different than the 2-D specs. The QuestAir with a 230XX airfoil is a faster plane than the Glasair III with a laminar airfoil? That is not a debate. The Lancair IV uses some custom and non laminar flow airfoil and is also faster I beleive. Yes the 230XX goes back to the 1930's or 40's but things have not changed much. It gets the job done. Bad stall characteristics are over blown in my opinion. Does any one fear their RV's stall? There is more than just low drag numbers to an airfoil, like lift and pitching moment.

Quote:
Originally Posted by F1Boss View Post
Hey Fellas:

As for the Questair Venture wing, it did start with a 230XX foil, but it was changed from that rather quickly (stall characteristics again!). Do your investigating before you report!
Mark two or three refs show the QuestAir uses a 230XX? What did it change to? "The designer Jim Griswold... who also headed the team the QuestAir Venture, also designed the Malibu for Piper... both use the NACA 230XX." Ref http://nuventureaircraft.com/

Laminar flow airfoils are not new. The P-51 in the early 1940's had the laminar flow NAA/NACA 45-100. I reject the off hand comment that they used what ever NACA threw out. They had the Clark Y before. I have read some of the old dead "sea scrolls" of Aerodynamic days gone by. Those guys where smart. They may have not had computers but they knew how to use them slide rules. I really don't think it was a willy-nilly reason the 230XX was and is popular. Even the late model Cessna Citations still used the 230XX today. Is it the perfect airfoil handed to us from upon high? No but it seems to work well in the RV and many famous planes. One KEY to the 230XX working well is keeping weight down. Drag does go up quickly at higher lift coefficients. Less weight the better.

Quote:
Evo airfoil:
The CZ engineer started with the MS(1)-313, but we ran into the same thing everyone else using the new foils did: high pitching moment. We flattened out the aft camber to the limits of the aileron and flap design, and this gave us a foil with an approx 60KT wide trim band......

BTW: Glasair uses the LS(1) or GAW foil; Lancair/Columbia and Cirrus use the NLF foils, again all are modified in the TE area to reduce pitching, and also at the LE (Lancair and Cirrus) to tame the stall to certified limits.

The MS(1)-313 is supposedly about 40% laminar, where the 230XX is about 20%; more attached flow is probably better in just about any case. We haven't seen degradation effects that compromises performance to a large degree -- NASA says it (and other later-designed foils) perform more like the 230XX, or other non-laminar foils, with bugs on the LE.
Carry on!
Mark
Mark in no way am I putting down the Pert-tee (Texas for pretty) Evo wing or its numbers, they speak for them self, its faster. However your comment about filling in the cusp to reduce pitching moment caught my attention, since that lowers life and lowers l/d. Do you fly at a higher angle of attack in cruise than the "sport wing". The Glasair was slower than the QuestAir in part due to lower lift, filling in the cusp lowered lift further. Of course Glasair used a different airfoil than you did. I don't know enough to compare the difference. This goes back to the "NO FREE LUNCH" theory. Yes laminar flow wings have less drag but come with other issues. It's how you handle those issues & mitigate them which determines overall gain/loss.

Here's some experimentals (mostly) w/ laminar & odd ball airfoils:
Swearingen SX-300, NASA NLF(1)-0416
Stoddard-Hamilton Glasair III, NASA GA(W)-2 mod
Evo Wing Rocket, NASA MS(1)-313
Jones White Lightning, NASA 66-215 LINK
Aviat Millenium Swift, NASA NLF(1)-0414F/M1
Mooney 301, NASA NLF(1)-0315 LINK
Neico Lancair 320/360, NASA NLF(1)-0215F
Neico Lancair Columbia 300/400, (root) NASA NLF(2)-0215(H)/(tip) NASA NLF(2)-0215(D)
Wheeler Express, NASA NLF(1)-0215F
Neico Lancair IV, (root) McWilliams RXM5-217/(tip)NACA 64-212 **
Prescott Pusher, NASA NLF(1)-0215F
Sharp/Ericson Nemesis, NASA NLF(1)-0414 mod
Aero Designs Pulsar, NASA MS(1)-0313 mod

** The Lancair IV I think is faster than the Glasair III. Not sure what a McWilliams RXM5-217 is. The NACA 64-212 airfoil is a little infamous (used on BD-5). This airfoil is low-cambered and accounts for low maximum lift coefficient and sharp loss of lift at the stall. It's thickness is 12%. The max thickness is moved aft compared to the 230XX. Why they used it at the wing tip, I'm not sure. The Lancair IV reputation is being a HOT airplane. The SX-300 is a personal favorite of mine, but its approach speed of 105 kts!
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Last edited by gmcjetpilot : 11-19-2007 at 10:47 PM.
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  #16  
Old 11-20-2007, 07:10 AM
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N395V N395V is offline
 
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Quote:
I've flown an earlier Harmon "rocket" with its itty-bitty chopped off wings. It was sled-like, not very fast for the installed HP and bled energy like a pig in turns. I was glad to climb back into my 200HP RV4.
After 3 years and 500 hours in my Rocket why am I suddenly surprised to find out my airplane is a pig.

I think it is quite fast for the horsepower, my wings are shorter than an RV but I wouldn't characterize them as itty bitty. If I crank in 60 deg of bank or more it bleeds energy but during normal ops I bank like everyone else and energy loss is no more noticable than any other plane. The energy bleed at higher angles of bank is quite often a useful tool.

Quote:
The "rocket" I flew would cruise around 230 mph with 260 HP installed. My friends RV4 would cruise about 210 with two fewer cylinders. Power off the Rocket came down faster than it would go up - it roared downhill like a manhole cover on edge. Not my idea of a good time if that happened IFR on top. I just don't have that much trust in these old engines
The rocket does NOT go down faster than it goes up. That statement is pure ****. You just have to know the plane and fly it correctly.

20mph faster is 20mph faster and if that is what you want as a pilot it doesn't matter how you get it. If flown correctly it does not come down like a manhole cover on edge clearly you need more time in a rocket to be able to correctly describe its flight characteristics.

If you do not trust a lycoming IO540 on top IFR you shouldn't trust an IO 360 either. If you cannot safely execute a power off landing when you pop out of an overcast you shouldn't have been up there in the first place. I will gaurantee you my probability of surviving an engine failure in an F1 is the same as surviving one in an RV. You just have to know your airplane, plan your flight, and fly it according to its characteristics.

Quote:
IMHO the F1's are too pricey. What extra performance you get there is offset by much higher cost to operate (the 550 up front), poor tradeoffs in terms of aerodynamic and propulsive efficiency (exception: the EVO wing), and higher kit costs.
The pricing is obvious. If you cannot afford it do not buy it. If your desire is more speed then there is no offset. Speedd costs its just that simple. Don't like the fuel burn pull the throttle back and fly RV speeds. If you want to go fast in a Rocket you can. With a 4 banger you go slower. Depends on what you want.

Quote:
plumb the outer wing panels with extra fuel to get outrageous range.
Thats great till you have to pee or turn 60 and arthritis sets in. Any more than 3 hrs in a small plane is pure agony for some of us. Load more fuel than the plane was designed for and it may go down faster than it goes up and may bleed energy like a pig. The price of adding more tankage may well offset the advantages of owning an RV. But I really do not have enough hours in an RV to characterize them.

Quote:
Have the advantage of industry leading support and a HUGE builders network.
This comment alludes to what I consider an old wives tale. That is most kit manufacterers go belly up and leave the airplane owner with an orphan.

I have had nothing but great support from Team Rocket for many yaers and there is no indication it is going to go away. There isn't a single part on the F1 or Harmon that I cannot make in my shop or buy from Vans or another source. Same goes for my plastic airplane of which only 2 exist. As for the support of a great builders network it is right here on this forum for any plane you choose to build.These guys have helped me and several others builders of non Vans aircraft on multiple occassions.


So if you want an F1 or a Harmon get one if it fits your desires. The F1 is one of the sweetest flying planes in existence and has given me many of the most enjoyable flying hours in my life. They have no unsafe flying characteristics if flown correctly just as in the RVs.

RVs are wonderful planes and if one of them better suits your needs or budget then an RV can't be beat.

If you want to know the negatives about a Rocket ask a Rocket owner not someone who "flew one once".
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  #17  
Old 11-20-2007, 07:10 AM
bostontea bostontea is offline
 
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Quote:
Originally Posted by mark manda View Post
I gave a guy a ride in my Rocket early Saturday morning around the Taylor,TX race course and he said he had the last set of EVO's(and he wasn't giving them up) so this may all be moot. You can buy an EVO for $250K or

you'll have to wait for the EVO II!
What is the EVO II?
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  #18  
Old 11-20-2007, 07:29 AM
gstone gstone is offline
 
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Thumbs up Well said...

Thanks Milt!!

greg
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  #19  
Old 11-20-2007, 08:40 AM
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f1rocket f1rocket is offline
 
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Milt, I've stayed out of this fray because all the "rocket experts" are not rocket owners. Nuff said.
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  #20  
Old 11-20-2007, 09:44 AM
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Bill Wightman Bill Wightman is offline
 
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GMCJetPilot

Quote:
Well you sound like a real Aero guy, I have only stayed in a Holiday-Inn and sat next to a real Areo guy.
20+ years doing this does qualify me to a certain degree. Granted, I only now work as a consultant, not full time but I keep my plate full. Please do not denigrate anyone here.

By the way, planform by far plays the larger role in how a wing performs (a wing is a 3-d shape and an airfoil is a 2-d shape). The aircraft you referenced all have very different planforms, fuselages, etc. Also, I think F1Boss said the Questair design team quickly chose other than a 23XXX section. He's probably right.

Milt

Quote:
If you do not trust a lycoming IO540 on top IFR you shouldn't trust an IO 360 either.
I would fly on top but not for extended periods over low ceiling/vis. My 10000+ hours has its share of lessons.

Quote:
Quote:
IMHO the F1's are too pricey. What extra performance you get there is offset by much higher cost to operate (the 550 up front), poor tradeoffs in terms of aerodynamic and propulsive efficiency (exception: the EVO wing), and higher kit costs.

The pricing is obvious. If you cannot afford it do not buy it. If your desire is more speed then there is no offset. Speedd costs its just that simple. Don't like the fuel burn pull the throttle back and fly RV speeds. If you want to go fast in a Rocket you can. With a 4 banger you go slower. Depends on what you want.
"IMHO" means "In my humble opinion." You can attack that all you want. You have yours and I have mine. I do respect yours, hope the reverse is true too.

As for the extra fuel, you'll find those ideas are being implemented and are selling on the market. I'm only reflecting a real-world trend, not something I've done with my own airplane.

As for safely executing a forced landing from an undercast condition, I think many of us would see that as a "worst case" scenario. Glide time after breaking out, glide speed, rate of descent and time to select a landing site all play a role in hopefully getting on the ground safely. Airplanes that don't do the above things as well are going to present the pilot with more difficulty and reduce the chances of a safe landing. This is a point Van has made from the get-go and I think he's right.

As for "industry leading support, and huge builders network", I think Vans Aircraft has set a high standard. I've been a builder/flyer on several projects since 1987. I'm sure the Rocket people do a fine job too. The builders network I refer to is this forum and the many thousands of RV'ers out there who will help you at the drop of a hat. It IS great, and do not see that reality as an old wives tale.

Finally, I really never intended to join a "fray" either. I'm an enthusiastic builder and designer who has a passion for this hobby like the rest of us do. I hope we can keep the commentary constructive, and if critical, keep it respectful.

Fly safe...
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Last edited by Bill Wightman : 11-20-2007 at 05:26 PM. Reason: added comments
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