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  #31  
Old 02-11-2007, 12:25 PM
deuskid deuskid is offline
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Quote:
Originally Posted by Steve parkins View Post
A Pedant is a person who overrates or overuses book learning or pure technical knowledge. Such a person values simple knowledge, (in the form of often obscure facts and rules) over common sense and more general knowledge. are you picking on marc ?
I hope not. I highly prize his well founded and helpful insights.

I *might* has cast a slightly disparaging remark towards taking something that is simply suppose to be fun/funny and making it into something more significant.

I actually wasn't 'correcting' Marc ... I was replying to his 'correcting' me by saying ... naw.... exactness isn't needed or called or here.

everybody play nice now...

John
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  #32  
Old 02-11-2007, 12:27 PM
deuskid deuskid is offline
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Originally Posted by John Slade View Post
Would that be as in "laxative". What could you possibly be suggesting, John.
the unconstrained free flow.......





of ideas,



John
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  #33  
Old 02-11-2007, 12:34 PM
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Originally Posted by deuskid View Post
everybody play nice now...

John
NO! Folks not playing nice, to me, is JOB SECURITY (in both my chosen professions )
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  #34  
Old 02-11-2007, 12:36 PM
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Quote:
Originally Posted by deuskid View Post
the unconstrained free flow.......


of ideas,
AND, in some cases, AKA, diarrhea of the mouth.
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  #35  
Old 02-11-2007, 12:47 PM
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Quote:
Originally Posted by karoliina View Post
Laminar flow has nothing to do with stall speed.............
That is true. But I believe the intent of the post was to ask why the aircraft needs to go as fast as 70 to lift off the nose, thereby changing the angle of attack so that the main wing will start flying.

You can't change the AOA (on a "stock" Cozy) without changing the longitudinal axis of the aircraft during takeoff roll until the canard has enough lift to change it. You could put a huge "hershey bar" canard on the front that will lift the nose at 30kts but then the main wing wouldn't fly yet, it would be like a big "air bulldozer" and would eventually make it do a backwards flip. That's what would happen if the canard lifted first.

To acheive a safe flying airplane, the canard and main wings have to be paired (in speed necessary to lift) close enough to allow the canard to stall first, which means it lifts last on takeoff roll, right?
Laminar flow wings shine at high speeds where turbulent flow is minimized by the design. Other types of designs and poorly constructed laminar wings aren't as efficient at high speed.
The original poster was interested (I believe) in a wing set that required less airspeed to achieve enough lift to fly.
I believe that if it could have been done, it would have been done. The compromise is for higher top end speed. A specially designed wing, laminar flow or not, could put it in the air faster, but would not be as fast in the air.

You CAN change the AOA of a flying aircraft to make it stall. You can't change the AOA of a canard (using control surfaces) until it does fly. Generally speaking, if you lower the stall speed of a wing by changing it's shape, then you lower the speed at which it will fly (create enough lift to whatever it is attached for it to be lifted off the ground). The elevators do that but only to a limited extent on a canard. Flaps would make it lift sooner, but you would have to put flaps on the main wing too and they would have to be operated simultaneously. Of course, while the flaps were down, the flow would not be laminar would it?

From experience I know that a Cherokee 140 will lift off the ground at a slower airspeed than a Commanche 250. The 140 will float (seemingly) forever whilst landing with it's hershey bar wings. The Commanche with it's laminar flow wing will drop like a rock when it gets close to stall speed.

Take off slow, land slow. I can put just about any small plane down safely in a field that I couldn't safely take off from. Stalling is more of a "landing thing" than a "take off thing" IMHO.

Pretty much that's why I mentioned the laminar flow wings needing to go faster for take off, all the aircraft I am familiar with are that way when compared. I didn't know there were other wings designed for other 4 place powered pushers enabling them to land at such slow speeds which could be considered as a feasible substitute. I personally am not building a glider or putting a glider wing on my aircraft.
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Last edited by Clutch Cargo : 02-11-2007 at 02:07 PM. Reason: gramer boo boo
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  #36  
Old 02-11-2007, 12:51 PM
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karoliina karoliina is offline
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Quote:
Originally Posted by Marc Zeitlin View Post
OK, so after a bit of research, the CAFE formula is:

CAFE = speed^1.3 * MPH * payload^.6

Gary Hertzler's VE came in at 170 mph, 48 mpg, and 400 lb, for a score of 1.38 million.
Checked from Cafe foundation the numbers:
Gary Hertler's VE got score 2304153, not 1.3 million! It is one million better than Rutan Catbird.
Please see:
http://cafefoundation.org/v2/pdf2/90CAFE400.pdf

Also there is a typo in the abovementioned equation btw.

Which one is the correct equation?

CAFE = speed^1.3 * MPG * payload^.6
or
CAFE = speed*1.3 * MPG * payload*.6

For Gary's VE, the latter results 2.2 million. For the same VE, the first one results the same number you gave.

Maybe worthless to calculate with the old equation as the PAV equation represents better the efficiency since it takes in account
the cost and the speed is there only once and not two times. In the old equation, for example Questair Venture got very high result because of the high cruise speed despite
of having a very bad MPG compared to Gary's VE. Or Maybe I should invent Karoliina's kahvi-equation (Kahvi = cafe in Finnish). It would have the largest emphasis
on MPG since for my preferred mission profile it is the most important parameter of the all different parameters. Sacrificing speed is no problem if it gives better MPG.
A perfect plane for me would beat our hybrid car in MPG. It is very hard though since even Gary's VE can't beat it. For example, if you are flying around the world, the most
imprortant issue comes from the cost and endurance and extremely high MPG would help.
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Last edited by karoliina : 02-11-2007 at 01:22 PM.
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  #37  
Old 02-11-2007, 01:16 PM
SteveWrightNZ SteveWrightNZ is offline
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Default summarizing

points conceded so far are ;

Both temporarily increasing the canard incidence during the rotate, and raising the nose rolling-stance, MIGHT assist offsetting the negative effects of moving the mains back some SMALL amount.

Some people want to fly, some want to test-fly, some want to build, some want to design/engineer - none of them are wrong.

Poor behaviour is childish and wrong.


Rhetorical questions ;

Can the wheels be temporarily moved back an inch or two using adapter plates on the plans strut at the plans location.

Could the canard be mounted in such a way that it might be rotated a few degrees.

The result of all this may not be significant - is it worth it.


summary - a brief statement that presents the main points in a concise form.

S
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  #38  
Old 02-11-2007, 01:22 PM
Marc Zeitlin Marc Zeitlin is offline
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Quote:
Originally Posted by karoliina View Post
Checked from Cafe foundation the numbers:
Gary Hertler's VE got score 2304153, not 1.3 million! It is one million better than Rutan Catbird.
Please see:
http://cafefoundation.org/v2/pdf2/90CAFE400.pdf
You are confusing two different formulae. The RACE 400 formula is:

CAFE 400 score = V * MPG * Payload

as shown on the third page in the link above.

If you go to the CAFE foundation web pages, and search through their documentation, you'll find the CURRENT measure of efficiency, which is:

CAFE = speed^1.3 * MPG * payload^.6

using THIS measure, which is the one that Catbird and COZY are measured against, Gary's VE get's about 1.3 million.

Quote:
Originally Posted by karoliina View Post
Also there is a typo in the abovementioned equation btw.
As previously conceded.
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  #39  
Old 02-11-2007, 01:27 PM
Marc Zeitlin Marc Zeitlin is offline
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Quote:
Originally Posted by karoliina View Post
I just went to your page, took the alleged optimum cruise: 6 gph at 12000 feet, 160 kts, 50% power. If you base the calculations on this, you'll get over 3 million.
Once again, you're using the wrong formula, or using it incorrectly. Put these #'s into the correct formula:

CAFE = V^1.3 * MPG * Payload^.6

and you get a score of 1.6 million. Assuming you trust those #'s - I've never seen quite that performance in my plane :-).
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  #40  
Old 02-11-2007, 01:32 PM
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karoliina karoliina is offline
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Hi Marc,

Thanks for clarification. So therefore, I can recalculate Diamond DA-40 as follows:

156 mph ^ 1.3 * 33.2 MPG * 755 ^ 0.6 = 1255938
(pretty good)

and TL-96 StarSport as follows:

100 mph ^ 1.3 * 31 MPG * 616 ^ 0.6 = 582251
(pretty bad)

Karoliina
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  #41  
Old 02-11-2007, 01:34 PM
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karoliina karoliina is offline
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Quote:
Originally Posted by Marc Zeitlin View Post
Once again, you're using the wrong formula, or using it incorrectly. Put these #'s into the correct formula:

CAFE = V^1.3 * MPG * Payload^.6

and you get a score of 1.6 million. Assuming you trust those #'s - I've never seen quite that performance in my plane :-).
I got the numbers from here from the fine-print:
http://www.cozybuilders.org/performance/range.html

It says 50% at 12000 feet, 6 gph 6 gal/h.
How do I interpret your performance graph wrongly? Or is it so that
the efficiency is always calculated from CAS not TAS?
Could you please then tell how much are the actual numbers for economy cruise in CAS and consumption?
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  #42  
Old 02-11-2007, 04:57 PM
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... to the pain!
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Last edited by MarbleTurtle : 02-11-2007 at 04:58 PM. Reason: paying no attention to the non princess bride posts
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  #43  
Old 02-11-2007, 06:37 PM
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Steve parkins Steve parkins is offline
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Quote:
Originally Posted by Dennis Passey
Marb- did you notice that he didnt misspell anny word there either?!...and pedant, heck he's been reading in the bathroom again. Maybe it was the 'laxative'...
Luv ya Stevo =]


lol
OK then help with this, just did the lip in the back top of the fw and it showed two small left and right side thingies made out of plywood(M7)
i did the 8 lay-up for the mounts long ago
i think my thingies are part of the fw and there for i must have did the lay-ups over the thingies and not before.
add 2 more bid ? 4? never mind it ? re do it ?
i looked at johns web for a clue, and saw his temp fw is the same as my final one and his has the side thingies on it as well. but alas, could find none of his final fw before glassing the hard point..
i photo shopped it to show the thingies and the glassing. if you look close, note the outer right side(the part that has no paint on it) that is where i raped the glass around on the hard point. hopefully you can see the difference between what i did and the plans way, any help here will be gladly payed for with a kiss.

i got more pic's to help show the problem
you can see the plans tracing overlayed and i included the pic from the plans to show my confusion, and a over all shot of the lip.
this post is lost is space and wont come up under new stuff.........rats
Attached Thumbnailshttp://www.canardaviationforum.dmt.n...d=1 171230757 http://www.canardaviationforum.dmt.n...d=1 171230757 http://www.canardaviationforum.dmt.n...d=1 171230757 http://www.canardaviationforum.dmt.n...d=1 171230757
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  #44  
Old 02-11-2007, 06:44 PM
Marc Zeitlin Marc Zeitlin is offline
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Quote:
Originally Posted by karoliina View Post
It says 50% at 12000 feet, 6 gph 6 gal/h.
How do I interpret your performance graph wrongly?
You've got that right - that's what it says. And if you put in those #'s, you get 1.6 million.

Quote:
Originally Posted by karoliina View Post
Or is it so that the efficiency is always calculated from CAS not TAS?
Nope - TAS is right - that's what you're actually getting.

Quote:
Originally Posted by karoliina View Post
Could you please then tell how much are the actual numbers for economy cruise in CAS and consumption?
I rarely fly at 12K ft, but the few times I have I didn't throttle back that far - I generally fly at 60% or better. I'm guessing at 6 gph I'd be a bit slower than 186 mph - probably closer to 175 mph, but I'm really guessing.
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  #45  
Old 02-11-2007, 10:07 PM
swinn swinn is offline
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So how much would you have to increase the wing area of a Cozy IV to reduce it's stall speed by, say 10 knots at gross weight? How much would the induced drag increase? How much slower would the cruise speed be, given the same power?
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