ideal aerofoil

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Kiwi303

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En Zed. Aka The Shire.
Unless the Mods spin out this as a Hangar Flying thread for Nuclear-strike Bean powered Rockets this'll be the last post on the off-topic Kiwi notes.

YEAH THE BEANS I FORGOT THEM! Sixty Bean Power to the tin....

Also I believe the KIWI undercarriage is strengthened for NAVAL CARRIER LANDINGS! From the hopping off the banks it can do......

And because it usually only comes out at night it must be STEALTHY.

Never mind the KIWI-TNT nuclear test, SHHHH the Greenies do not know about that one. It was to be tested at Auckland as well.....

Do not tell anyone about New Zealand's Uranium deposits either, remember the Pike River coverup/s....:cool:

Perhaps the Uranium affected the copying of the KIWI's airfoils process?
Those fuzzy Kiwi feathers are as quiet as an OWL, so Yup Stealthy until it passes, with secondary defensive weapon of unburnt bean gas disrupting targeting of suddenly alerted AA units...

As to Nukes... if I swim the river, then cross the road - Eh, hang on, I'll just go up the track to the road and cross by bridge!- on the far side of the road from here is a crag called Uranium Corner where there is a big hole carved out by uranium prospectors in the 50's... the found it... but before it got commercialised we got the Nuke Ban of the 80's.



Down to airfoils, I have to agree with the above post, design the wing first, Aspect ratio, sweep, dihedral, taper... all that BEFORE then looking at what foil fits that wing.

For MOST homebuilt, TLAR with thickness around 12% of chord just works well enough for the basic simple low speed hamburger acquisition vehicle. Higher performance needs higher optimisation, but for the low and slow just look at what the slide rule and eyeball design planes from the 40's and 50's coming out of peoples garages have.

While I haven't built anything myself yet, despite a set of Jodel plans causing me to join this forum in the first place, from my admittedly armchair perspective I have to say I'm not a great fan of Laminar foils, Something simpler and which does not mind raindrops or piles of bug guts changing profiles seems far more suited to flying at VFR levels.
 

blane.c

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There is argument for dirt. Real dirt. Mud, ice, bugs and what have you. Some airfoils are awesome if you keep them sanitized, but put some dirt on them and they fall out of the sky. So I like an airfoil that will fly with everything on it, you know dirt, mud, ice, frozen mud, bugs, and the occasional remnant of sandwich that has been chucked out the window.
 

WINGITIS

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Wellington, New Zealand
I started out with Raymer's guide which helped me understand the "dynamic components" that were required for an aircraft and then looked at airfoils after understanding that.

His Spreadsheets take a bit to get used to but are useful and a lot quicker than formulating your own.

Heres what it looks like:


I have a PDF copy as well as the book, but as he sells it, Its really appropriate to buy a licensed copy.

Amazon have 2 copies left:


K
 

ypsilon

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Austria
The ideal laminar flow airfoil is the combination of the Wortmann FX-62K-131 and the FX-60-126. I know this because those are the airfoils that Gerhard Waibel used, at different spanwise locations, on the best all-around racing glider ever built :)
You were right, until it started to rain. ;)
 

Aesquire

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I've got a little time in the air with a 225-75-R15 airfoil. You bend the rib around a tire that size for the curve in front. Pretty good low speed lift, predictable stall, ( rectangular wing with washout ) but drag increases rapidly as you speed up. Did a polar chart once. I've seen worse in TOWS from WW1. Not a terrible choice if you stay under 40 knots.
 

WINGITIS

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I've got a little time in the air with a 225-75-R15 airfoil. You bend the rib around a tire that size for the curve in front. Pretty good low speed lift, predictable stall, ( rectangular wing with washout ) but drag increases rapidly as you speed up. Did a polar chart once. I've seen worse in TOWS from WW1. Not a terrible choice if you stay under 40 knots.
That is a diameter of 28.3", that is a LARGE PLANE!?

 

Norman

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That is a diameter of 28.3", that is a LARGE PLANE!?
You only use the tire as a bending fixture to set the camber. 30 or 40 degrees is all the arc you need. The rest of the airfoil is a straight line of whatever length you need to get the chord length you want. Ideally the straight part should be 3 or 4 times the length of the curved part. If it's more than 4X you should probably get a bigger tire. The airfoil in the attached drawing is 46". Pretty crude but like the man said "Not a terrible choice if you stay under 40 knots"
 

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WINGITIS

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You only use the tire as a bending fixture to set the camber. 30 or 40 degrees is all the arc you need. The rest of the airfoil is a straight line of whatever length you need to get the chord length you want. Ideally the straight part should be 3 or 4 times the length of the curved part. If it's more than 4X you should probably get a bigger tire. The airfoil in the attached drawing is 46". Pretty crude but like the man said "Not a terrible choice if you stay under 40 knots"
OK, now I get it, thanks for that.
K
 

Topaz

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... from my admittedly armchair perspective I have to say I'm not a great fan of Laminar foils, Something simpler and which does not mind raindrops or piles of bug guts changing profiles seems far more suited to flying at VFR levels.
That's old news. Any laminar airfoil designed since about 1985 doesn't lose significant lift when contaminated with reasonable levels of dirt, bugs, etc. Riblett's laminar sections, the NASA NLF series, and all modern sailplane/motorglider airfoils retain lift when contaminated, and only suffer the increase in drag from having their boundry later "tripped" to turbulent. Airfoil designers figured out how to do this decades ago.

The "get a laminar airfoil dirty and it falls from the sky" thing might have been true in the 40's-60's, but it's not true anymore.
 

Lendo

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Roncz suggests that even when dirty Laminar Airfoils are better than Turbulent Airfoils - I tend to agree with him.
George
 

TFF

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Bombardier CRJ leading edges in regional airline duty have to be washed every three days so stall speed will stay book.
 

TFF

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Our FAA caused a big stink, when I did that kind of thing. Of course no one will say how bad it messes it up. I use to watch the landings during the push. You can always tell who is flying.
 

cirrus232

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Roncz suggests that even when dirty Laminar Airfoils are better than Turbulent Airfoils - I tend to agree with him.
George
As someone else said -- it is too broad. And usually not correct. Especially not usually correct if looking at stall speed, but it does depend on the airfoil design. You can have airfoils that have laminar flow at cruise, and at the same time handle Clmax nearly same dirty vs clean, and thus get the same stall speed. So back to ... the statement is too broad. I wonder in what context Roncz said this? I'm guessing that some qualifiers were included. He has designed airfoils that are vastly different (not desirable) when 'turbulent' (dirty).
 

Aesquire

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One thing people forget is the NACA series airfoils were not actually intended to be "used". Oh, they are, all the time, but the Original idea was to test a series of shapes and try to derive an actual science out of it. You were supposed to look at the numbers and pick the shapes you needed for your purpose.

That is an over simplification, but once there was a book full of airfoils to draw from, it became the default instead of the starting point.

In a very real way Riblett was doing exactly as intended, originally, taking a known airfoil and making it better for it's purpose.
 

davidjgall

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One thing people forget is the NACA series airfoils were not actually intended to be "used". Oh, they are, all the time, but the Original idea was to test a series of shapes and try to derive an actual science out of it. You were supposed to look at the numbers and pick the shapes you needed for your purpose.

That is an over simplification, but once there was a book full of airfoils to draw from, it became the default instead of the starting point.

In a very real way Riblett was doing exactly as intended, originally, taking a known airfoil and making it better for it's purpose.
Except Riblett was wrong about how to "assemble the parts."
 
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