Date: Thu, 15 Jan 1998 20:22:16 +0200 (GMT) From: pine@global.co.za (pine) Subject: COZY: VNE Hi to All I was talking to a model glider builder/flyer the other day and started talking about Vne speed's and how flutter destroyed some of there planes. This makes me wonder what the limiting facter is for Vne on the Cozy Mk IV, and how some of the other canard's can claim higher Vne (Berkut, E-racer, and some Long's) Any Ideas ???? Pine Pienaar pine@global.co.za From: Marc J. Zeitlin Subject: COZY: VNE (fwd) Date: Fri, 16 Jan 98 11:36:43 EST Pine Pienaar writes: >This makes me wonder what the limiting facter is for Vne on the Cozy Mk IV, >and how some of the other canard's can claim higher Vne (Berkut, E-racer, >and some Long's) This is total speculation, but here goes. The Berkut LOOKS like a L.E., but has been totally redesigned using different materials, so it's not surprising that it would have different characteristics and limitations. The E-racer uses the L.E. wings (I believe), so I would guess that any E-Racer or L.E. that claims a higher Vne would have been tested for flutter resistance to that speed in order to make the claim (or else the person claiming it is an idiot). My guess is that the COZY would have the same capabilities, but that no one has tested it to those speeds, so no one makes the claims for it. Given that Nat's COZY could do 230 mph with the Franklin engine, we can probably safely assume that the Vne could be bumped up at least that high, and when the 240 HP Subaru folks start flying theirs, we might get some testing at even higher speeds. My $0.02. -- Marc J. Zeitlin Email: marcz@an.hp.com From: N11TE Date: Fri, 16 Jan 1998 12:06:38 EST Subject: Re: COZY: VNE (fwd) In a message dated 98-01-16 11:37:08 EST, marcz@hpwarhw.an.hp.com writes: << Given that Nat's COZY could do 230 mph with the Franklin engine, we can probably safely assume that the Vne could be bumped up at least that high, and when the 240 HP Subaru folks start flying theirs, we might get some testing at even higher speeds. >> Marc: Since I am installing a 260 hp IO-540, this was a meaningful question to me. I have talked to a number of Cozy builders and almost all verbally reported exceeding these speeds. One, who I highly respect and shall remain nameless for obvious reasons, told me that he had significantly exceeded the above speeds in dive tests with no problems. Perhaps some builders will let us know of their personal experiences? Based upon analysis with a published computer program, with this engine and my airframe modifications, I expect (hope) to be able to cruise at or even well above this 230 mph. Obviously, you are your own manufacturer and you are the sole person responsible for the quality of construction and the risks you wish to take. I certainly caution all to carefully test your own plane using approved methods. (Hopefully this disclaimer will prevent a whole lot of flame bandwidth.) I intend to very cautiously open my plane's envelope. Tom Ellis N11TE@aol.com Cozy plans #25 now AeroCanard 540 Date: Fri, 16 Jan 1998 09:27:36 -0800 From: "LCDR James D. Newman" Subject: COZY: Re: Vne Hi Marc and All, >Marc J. Zeitlin wrote: >snip< Correct. >My guess is that the COZY would have the same capabilities, but that no one has tested it to those speeds, so no one makes the claims for it. Given that Nat's COZY could do 230 mph with the Franklin engine, we can probably safely assume that the Vne could be bumped up at least that high, and when the 240 HP Subaru folks start flying theirs, we might get some testing at even higher speeds.< Vne is expressed to the pilot as IAS (CAS). A plane cruising 230 mph is usually expressed to the pilot as TAS. This was discussed 09/96, so the discussion should still be in the archives. Infinity's Forever, JD From: lschuler@cellular.uscc.com Date: Fri, 16 Jan 98 14:31:18 -0600 Subject: Re[2]: COZY: VNE (fwd) Tom Ellis wrote: >I intend to very cautiously open my plane's envelope. Solid advice. But, before doing that, make sure the 'envelope' was designed to accommodate the additional gust and maneuver loads. The plane may not fall apart from a flutter problem at 250 Mph, but a 20 degree bank and a 30 Mph gust at 250 Mph 'could' rip a wing off if it wasn't designed for same. Not just a flutter issue. If you intend to exceed (essentially change) the specified 'design' envelope, it seems prudent to ensure a diferent envelope is appropriate for the construction. Larry Schuler From: lschuler@cellular.uscc.com Date: Fri, 16 Jan 98 14:19:48 -0600 Subject: Re: COZY: VNE (fwd) Marc wrote: >This is total speculation, but here goes. The Berkut LOOKS like a >L.E., but has been totally redesigned using different materials, so >it's not surprising that it would have different characteristics and >limitations. >The E-racer uses the L.E. wings (I believe), so I would guess that any >E-Racer or L.E. that claims a higher Vne would have been tested for >flutter resistance to that speed in order to make the claim (or else the >person claiming it is an idiot). >My guess is that the COZY would have the same capabilities, but that no >one has tested it to those speeds, so no one makes the claims for it. >Given that Nat's COZY could do 230 mph with the Franklin engine, we can >probably safely assume that the Vne could be bumped up at least that >high, and when the 240 HP Subaru folks start flying theirs, we might >get some testing at even higher speeds. Carefull folks. It ain't just flutter you need to worry about when pushing the VNE 'envelope'. The operating/design stress envelope is just as important as flutter/frequency "modes". Considerably easier to rip a wing off due to a wind gust when doing a shallow turn at 250 than when doing the same turn at 120. Marc, I'll call yer $0.02 and raise ya $0.02. Larry Schuler lschuler@cellular.uscc.com From: Marc J. Zeitlin Subject: Re: COZY: VNE (fwd) Date: Fri, 16 Jan 98 17:07:43 EST Larry Schuler wrote: >Carefull folks. It ain't just flutter you need to worry about when >pushing the VNE 'envelope'. The operating/design stress envelope is >just as important as flutter/frequency "modes". Yes, but generally these are dealt with by the "manuevering speed" (which Wayne Hicks reminded me earlier today is "Va"). This is (for every plane I've ever seen) always less than Vne, so (without the POH for the COZY MKIV in front of me) I'll assume the Va is already less than the Vne, and will stay that way no matter what engine is installed or what Vne is set to. >Considerably easier to rip a wing off due to a wind gust when doing a >shallow turn at 250 than when doing the same turn at 120. Of course. Hence the Va determination for maneuvering and for flying in rough air. >Marc, I'll call yer $0.02 and raise ya $0.02. Watch it, we'll be up to real money in no time :-). -- Marc J. Zeitlin Email: marcz@an.hp.com From: N11TE Date: Fri, 16 Jan 1998 18:26:34 EST Subject: Re: Re[2]: COZY: VNE (fwd) In a message dated 98-01-16 16:51:33 EST, lschuler@cellular.uscc.com writes: << Solid advice. But, before doing that, make sure the 'envelope' was designed to accommodate the additional gust and maneuver loads. >> Excellent. I would love to do so. The problem is that the Cozy is a by- guess-and-by-golly expansion of the LongEz. I asked Nat for the name of the engineer he used so that I could bounce my changes off him but Nat told me that no structural or aeronautical engineer has ever reviewed this expanded design. There is nothing wrong with this... he built his plane and tested it himself for safety before selling plans. Builders just need to be aware of these facts. Also, note the need to respect the maximum maneuvering speed. That should not change. Tom Ellis N11TE@aol.com Cozy plans #25 now AeroCanard 540 From: lschuler@cellular.uscc.com Date: Fri, 16 Jan 98 17:21:43 -0600 Subject: Re[2]: COZY: VNE (fwd) Marc wrote: >snip >Yes, but generally these are dealt with by the "manuevering speed" >(which Wayne Hicks reminded me earlier today is "Va"). This is (for >every plane I've ever seen) always less than Vne, so (without the POH >for the COZY MKIV in front of me) I'll assume the Va is already less >than the Vne, and will stay that way no matter what engine is installed >or what Vne is set to. >snip Darn, I hate it when sombody's righter'n me. :-) But isn't Va just that: max manuever speed, which includes an allowance for a gust-load margin? And, isn't 'design' Vne that single point where manueving stress is such that a turn is ill-advised and all you have left is some gust margin? Maybe I'm wrong, but seems that increasing Vne means you either eat up the remaining gust margin or the plane was designed to handle the higher 'potential' gust stress. Thus my warning for stress analysis to go faster; not just go faster and see if the wings stay on. I AM NO AERONAUTICAL ENGINEER, AND ONLY KNOW WHAT I THINK I READ; OR IS THAT WHAT I READ...... I THINK.? >Watch it, we'll be up to real money in no time :-). Shoot, that happened as soon as I bought the first Wicks catalog! :-) Larry Schuler From: Marc J. Zeitlin Subject: Re[2]: COZY: VNE (fwd) Date: Fri, 16 Jan 98 19:26:40 EST Larry Schuler wrote; >But isn't Va just that: max manuever speed, which includes an allowance >for a gust-load margin? Yes. (Actually, it's "Design Manuevering Speed"). >And, isn't 'design' Vne that single point where manueving stress is such >that a turn is ill-advised and all you have left is some gust margin? > >Maybe I'm wrong, but seems that increasing Vne means you either eat up >the remaining gust margin or the plane was designed to handle the higher >'potential' gust stress. Thus my warning for stress analysis to go >faster; not just go faster and see if the wings stay on. No, that's "Va". You're only supposed to exceed "Va" in calm air, and you're not supposed to apply maximum control inputs when over "Va". Obviously, when near "Vne", you're over "Va" and all the restrictions apply. "Vne" is faster than "Va", and is limited by many things, flutter among them (others are control system forces, etc.). See Part 23 of the FAR's for a fuller explanation of all these speeds and their derivations (it's not exactly easy reading, but might be worth it): http://www3.landings.com/cgi-bin/get_file?pass=6997429&FAR/part_23/toc.html -- Marc J. Zeitlin Email: marcz@an.hp.com Date: Mon, 19 Jan 1998 09:23:17 +0200 From: Rego Burger Subject: Re: COZY: VNE -Reply High Tom, Q: Have you made any efforts to beef things up? Just interested. In forward flight & calm air I don't think we have anything to worry about up to 250 mph indicated..these are thumb suck figures! However in a dive with power on one could get to horrific speeds on a clean aeroplane. There is a point at which the drag from the winglets and wing could start creating pressures that are not so healthy. Also steep turns etc. should be limited to the manouvering speed for safety.. sadly the only way to find the end of the envelope is to test it to destruction which is expensive and dangerous. I take my hat off to guys who push these envelopes but I don't have the courage myself.... :-) The wings are known to twist under normal loads and speeds at the point where they mate against the strakes..the German authorities have insisted in an added bolt in this area as a MANDATORY change before flight authority is granted.. maybe they know something we don't! This bolt serves two purposes. 1) It stops the twist. 2) It holds the wing forward against drag forces. I'm seriously considering it. Ernie Degovia has the Mod. spec. Please fly with a chute if you're going to do the testing yourself and do them high up. Make sure the canopy can disappear at the wave of a hand too. Getting out is not easy as it seems..! Rego Burger, web site: http://home.intekom.com/glen/rnb.htm (home e-mail) mailto:rnb@intekom.co.za Date: Tue, 20 Jan 1998 10:45:07 -0500 From: David Domeier Subject: Re: COZY: Re: Vne Jim, Re " One would be hard pressed to attain 250 knts. IAS with a fixed pitch prop without over speeding the engine and/or prop." I scared the hell out of myself doing the VNE expansion in my LEZ some years back. I started at about 8000 feet by easing the nose over and watched the airspeed build gradually. It went to 180KIAS and stopped increasing so I pushed it over some more, and some more and finally stopped that little manuever as the noise level was very high, but everything was quite stable, thinking this makes no sense at all. The indicator never went above 180. Back on the ground we pulled the airspeed indicator and bench checked it. It had a mechanical block of some sort in it at 180 KIAS! (a new instrument from AS) Needless to say they replaced it and I later discovered it doesn't take much nose down to achieve the 200 knot red line in the LEZ. I have no idea how fast I was going on the first dive but it was over 200 knots by a bunch for sure. Burt designed a great airplane. There's room for dummies like me to screw up and still live to tell about it. dd