Cozy iv questions

[Waiter]

To get up off the ground faster keep the aircraft on diet.

Not to be a smart A$$, BUT,

 

Look at the pilots weight also. If the pilot is 10, 20, 30 lbs overweight, this has a significant impact on aircraft performance.

 

Watch those calories (fats, sugars, starches, etc).

 

It will not only improve the aircaft performance, but also the Pilots.

 

Waiter

[TMann]

The Idea of adjustable canard pitch was appealing to me as a means of trimming the canard at higher speeds. An approach such as this would have eliminated the need for the Roncz airfoild completely.

 

One of the problems with that type of arrangement would be the surrounding areas being modified to accept that amount of pitch change (IMO.) As far as the results others have had with this, I would suggest searching the archives.

[Marc Zeitlin]

The Idea of adjustable canard pitch was appealing to me as a means of trimming the canard at higher speeds. An approach such as this would have eliminated the need for the Roncz airfoil completely.

Huh? How so? And why would you want to?

 

... As far as the results others have had with this, I would suggest searching the archives.

To which archives do you refer? I have a pretty good memory, and have no recollection (in 12 years of following canard developments closely) of seeing any reference to adjustable angle of incidence canard airfoils being attempted.

 

There was ONE anecdotal reference in the canard-aviators archive in 1999 to a memory of two engineers attempting a full-flying canard (like a stabilator), but that's not at all the same thing.

 

Slightly more information would be useful for finding the references you claim.

[Nathan Gifford]

...Look at the pilots weight also. If the pilot is 10, 20, 30 lbs overweight, this has a significant impact on aircraft performance.

 

Watch those calories (fats, sugars, starches, etc).

 

It will not only improve the aircaft performance, but also the Pilots...

Well the aircraft's performance will also improve just as soon as the kids leave for college too...

[TMann]

There was ONE anecdotal reference in the canard-aviators archive in 1999 to a memory of two engineers attempting a full-flying canard (like a stabilator), but that's not at all the same thing.

Heh, heh, heh ....... those wild and crazy engineers.

 

(Sorry Marc, I just couldn't resist. )

[Marc Zeitlin]

Heh, heh, heh ....... those wild and crazy engineers.

 

(Sorry Marc, I just couldn't resist. )

And still no reference.

[Nathan Gifford]

Saw this at the Wings over Houston Airshow this weekend. They had a flying model (1/10 scale as well as a 1/4 scale) and a full size simulator using X-Plane with three projectors. It was fun.....Pretty darn ambitious though.

 

http://www.labicheaerospace.com/

Yep, no full-size flying models yet. Interesting how they are going to get one up and flying and get the kits out to the customers in 2007...

[TMann]

The Idea of adjustable canard pitch was appealing to me as a means of trimming the canard at higher speeds. An approach such as this would have eliminated the need for the Roncz airfoild completely.

 

Huh? How so? And why would you want to?

 

<sigh> An engineer’s explanation can be found here.</sigh>

 

One of the problems with that type of arrangement would be the surrounding areas being modified to accept that amount of pitch change (IMO.) As far as the results others have had with this, I would suggest searching the archives.

To which archives do you refer? I have a pretty good memory, and have no recollection (in 12 years of following canard developments closely) of seeing any reference to adjustable angle of incidence canard airfoils being attempted.

 

Well it’s from some of the information that I read in the past 20+ years that I have been following canard development. ( I bought my plans in 1983.) I could dig through my boxes of publications ( I could read before there was an internet) but I won’t. There were canards long before some guy split a Long-EZ and called it something else.

[Marc Zeitlin]

<sigh> An engineer’s explanation can be found here.</sigh>

While there's some interesting (and somewhat accurate) discussion in the thread you quote, this says nothing about why you'd want to get rid of the Roncz airfoil (and replace it with?), which was the claim that I was asking about.

 

Well it’s from some of the information that I read in the past 20+ years that I have been following canard development. ( I bought my plans in 1983.) I could dig through my boxes of publications ( I could read before there was an internet) but I won’t. There were canards long before some guy split a Long-EZ and called it something else.

Having read all of the CP's and all of the COZY newsletters, dating back to the early 1980's, we're in the same boat on exposure to canard information. There is no mention of variable incidence canards in any of the CP's or COZY newsletters (both of which are on-line and searchable), either. Remember, you referred to an "archive", not to "some boxes of stuff in my basement".

 

Basically, in other words, you think you remember seeing something somewhere about someone who had a problem with trying a variable incidence canard on some sort of aircraft, but you can't tell us who, where, how or when, nor even point us to reference material where we might find it for ourselves.

 

Not a data point. Claims need evidence.

 

Again, I'm not in favor of this idea on Rutan derivative canard aircraft in any way, shape or form, but if there are going to be arguments against it, they should be accurate.

[Hans S]

The thought I had on the canard variable angle is this...

 

You don't need the canard to stall before the main wing as on take off you are trying to go as fast as you can as quick as you can to get off the runway. If you are going too slow and the main wing stalls, the 10-100ft of altitude isn't going to help you in trying to build some speed up anyway.

 

If you are at cruise or max power, you aren't going to stall the main wing anyway. Unless you are doing loops.

 

If you want to over hp the plane to see how fast you can go before the wings rip off, taking the lift and drag out of the canard would be beneficial. Just out of curiosity, what is the fastest Cozy IV out there? Did the wings/strakes need to be beefed up?

 

If you are just putsin around, set the angle to stock.

[TMann]

While there's some interesting (and somewhat accurate) discussion in the thread you quote, this says nothing about why you'd want to get rid of the Roncz airfoil (and replace it with?), which was the claim that I was asking about.

 

Oh! Well why didn't you say so.

Please refer to the original reason for transitioning to the RONCZ airfoil which if I remember correctly involved running out of trim in rain.

 

 

Remember, you referred to an "archive", not to "some boxes of stuff in my basement".

 

 

Is that what an archive is in your world?

http://en.wikipedia.org/wiki/Archive

 

Most of my CPs and other newsletters have my name and address on the front of them. They were not scanned or bought in bulk at some later date. I hope your copies are accurate.

 

Also, not every fatality involving a Vari-eze or Long-EZ shows up in the Canard Pushers during the time they were produced.

<sigh> If it could somehow restore my tarnished reputation, I could furnish such evidence ......... but it does not change the factual nature of the event.

</sigh>

 

As always ...... I've enjoyed the exchange.

Now get to work!

[TMann]

If you are at cruise or max power, you aren't going to stall the main wing anyway. Unless you are doing loops.

Any airfoil that exceeds the critical angle of attack can stall .... at any speed.

[TMann]

Hey Marc, see if you can find this Vari-eze fatality in any of the Canard Pushers (6/16/1990).

http://www.ntsb.gov/ntsb/GenPDF.asp?id=MKC90DCJ01&rpt=fa

[Waiter]

I remember this one.

 

This guy tried to do a roll without adequate airspeed to complete the roll and fell out of the top while inverted and to close to the ground to recover.

\

NTSB report

 

http://www.ntsb.gov/ntsb/brief.asp?ev_id=20001212X23487&key=1

 

Waiter

[TMann]

I remember this one.

 

This guy tried t do a loop without adequate airspeed to complete the loop and fell out of the top while inverted and to close to the ground to recover.

\

NTSB report

 

http://www.ntsb.gov/ntsb/brief.asp?ev_id=20001212X23487&key=1

 

Waiter

Actually what happened is he made a high speed pass down the runway and started his climb out when it rolled 180 and nosed into the ground. Fortunatly I wasn't riding with him that day.

 

I had bought my plans from him a few years earlier.

Point being: If it's not in the CP, did it even happen?

[Marc Zeitlin]

Hey Marc, see if you can find this Vari-eze fatality in any of the Canard Pushers (6/16/1990).

http://www.ntsb.gov/ntsb/GenPDF.asp?id=MKC90DCJ01&rpt=fa

What does this accident have to do with variable incidence canards?

 

You can claim what you like, but without evidence, it means nothing.

 

When one refers to an archive that others should search through to find information to support your claims, pointing to the stacks of magazines that you have in YOUR house hardly qualifies, whatever the definition of an archive might be.

 

If you believe that people should pay attention to what you claim, you should be willing to back it up with facts. The aliens told me so when I was abducted - don't believe me? Look in the archive.

[TMann]

The aliens told me so when I was abducted ......

<sigh>Well that explains a LOT </sigh>

I give up.

[Nathan Gifford]

The only thing I remember about canard incidents over the last few years are builders wanting to change it for shorter takeoff runs.

 

I also remember some discussions about making the nose gear a little longer instead of changing the incident angle.

 

Maybe someone remembers the details...

[Bruce]

Hans,

 

Have you considdered the Spencer Air Car? You get foldable wings, a high thrust line and as a bonus you can land on a lake if you want or need to.

-Guy

 

Now here's my kind of plane/car!

 

Bruce Sturgill

[chasingmars]

You don't need the canard to stall before the main wing as on take off you are trying to go as fast as you can as quick as you can to get off the runway. If you are going too slow and the main wing stalls, the 10-100ft of altitude isn't going to help you in trying to build some speed up anyway.

 

If you are at cruise or max power, you aren't going to stall the main wing anyway. Unless you are doing loops.

 

If you want to over hp the plane to see how fast you can go before the wings rip off, taking the lift and drag out of the canard would be beneficial. Just out of curiosity, what is the fastest Cozy IV out there? Did the wings/strakes need to be beefed up?

 

This is pretty dangerous, as it expects the pilot to know (a) Why an airplane stalls, and (b) how to set it up appropriately, and © based on assumptions that are incorrect.

 

Ask a pilot (a) and most will answer "because you flew too slow", pressed, they clarify "below the stall speed". Stall speed varies with load and c.g.

 

As to ©: An airplane stalls when the angle of attack of the airfoil exceeds some critical value, which is only more or less well defined (i.e. lift loss can be sharp or somewhat gradual depending on the foil's stall characteristics). You can stall an aircraft at any speed up to the square root of it's load limit times the 1g stall speed for that configuration. Above that, you run a risk of ripping the wings off instead.

 

Trying to go fast only affects stall speed somewhat, in a way that is largely dependant on aircraft configuration. it in no way protects you from main wing first stall on takeoff. I suspect that a main wing stall on takeoff (by definition a phase of flight involving low speed operation) is much less benign in a canard than a canard stall (which would limit climbout angle or, if you don't have enough runway, be bad).

 

With regards to (b), the pilot shouldn't have "be an aerospace engineer and set incidence accordingly" on the checklist prior to T/O, cruise and landing.

 

As to the last part... Induced drag (from lift) becomes a very small component of total drag at high speeds, so doing wing things with AoA and expecting drag savings that are significant is unrealistic. Parasitic losses are your concern at the top end. Of course, not being able to get enough down elevator is another issue, and there is some advantage in being closer to neutral on the elevator when operating at high speed, but probably less than you suspect.

 

Flirting with pitch stability and controlability problems is a dangerous game and I'd suggest not worth the trade.

 

The real problem with trying to use variable incidence canards is that the concept misses a fundamentally fixed relationship. The airflow over both wings, at a distance, is coming at the fuselage at a fixed angle. That angle, modified by the incidence of the lifting surface, is therefore affecting both wings (yes, the wing behind the front is also affected by downwash, but that doens't significantly affect the conclusion), therefore, there is an optimum value of difference between the front and rear wing that, given the foils llift curve differences (and downwash), provides adequate protection from a main wing stall. increasing this incidence on the canard therefore, always, will reduce your margin for main wing stall. Decreasing it from this will therefore, always, increase your stall speed (a canard first stall, so perhaps minimum 1g flight speed is a better term). At the end of the day, neither is a good thing. Downwash and other second order issues complicate this, and make it a little less than strictly true, but it's basically the case, given that the elevator on the canard operates as a flap, and to a reasonable approximation, flaps do not significantly alter the maximum angle of attack of a wing.

[Hans S]

I think you missed my point, or maybe I'm off.

 

1. When taking off or landing you are at a slower speed this causes the front canard to lose lift quicker than the main. You either have to be traveling faster to keep the nose up or be pulling way back on the controls trying to keep the nose up. So, my point was to change the angle enough at landing or takeoff that the nose was lifting quicker and stay up at a slower speed on its own.

 

2. At increasing speed the lift that the canard continues to create makes it so you need to constantly trim down, eventually running out of trim. The ability to say, drop the angle enough so that the lift is reduced would bring your controls back into a middle level giving back some adjustment that could be needed to trim for CG adjustments.

 

3. Top speed from what I understand through the Roncz design and the mach number puts it at about 350mph. After that, the canard stalls by itself and the plane becomes a lawn dart, that is unrecoverable, so I read.

 

Pilot wouldn't need to be an engineer to fly, just have a few settings.

a. Straight level cruise, have three or four settings in inclination so every 25 kts has a setting, which would bring the main wing control surfaces back into their middle range.

b. All around flying, stock setting, the safest setting for playing around.

c. Landing and takeoff, equal to or slightly after the main stalls. You'd use this setting under 50'. Stalling the canard at this height wouldn't give you any help to gain speed anyway.

[Phil Kriley]

I think you missed my point, or maybe I'm off.

 

c. Landing and takeoff, equal to or slightly after the main stalls. You'd use this setting under 50'. Stalling the canard at this height wouldn't give you any help to gain speed anyway.

Stalling the main wing at this height will get you killed! You do not EVER want the main wing to stall before the canard - EVER! And so that means that you do not want to alter the canard such that it could allow a main wing stall - ever.

 

It's good to talk about these things, but to change the plane such that you could cause the main wing to stall before the canard is an invitation to disaster. Just don't do it.

[TMann]

Perhaps a tool that may be of use (while still being economical) would be to get a copy of X-Plane. There are files you can download that mimic the flight characteristics of the Cozy (as well as others.) You could implement your Ideas there and then study the results.

 

X-Plane should not be construed as a true design tool but it will answer many basic design questions and is a pretty good simulator.

[chasingmars]

I think you missed my point, or maybe I'm off.

 

No, I don't think I missed your point. To be blunt, I think you're off a bit, no big deal, to be honest, I cring almost every time a pilot trys to explain an aerodynamics concept, you don't need to know how to design a plane to be a great pilot, just don't try to redesign the plane, after all, you wouldn't expect an engineer to hop in a plane and say "well, I know the theory, I can design part of this machine, so I must be able to fly it without any specialized knowledge or training" would you? The reverse holds too.

[chasingmars]

3. Top speed from what I understand through the Roncz design and the mach number puts it at about 350mph. After that, the canard stalls by itself and the plane becomes a lawn dart, that is unrecoverable, so I read.

 

what I think you are talking about here is known as Mach Tuck. It has nothing to do with a lifting surface "stalling by itself". It has to do with a shift of the pressure distribution that occurs as the airflow over parts of the wing move into the transonic region and localized supersonic flow on the wing causes shock waves to form (the flow over the wing is faster than the freestream flow, and airfoils/wings have a critical mach number which is the freestream mach number that produces local M=1 flow)

 

http://en.wikipedia.org/wiki/Mach_tuck