CH701 Sans Slats?

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Joe Kidd

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Apr 9, 2008
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Steve,

Please correct me if I am wrong but isn’t the Savanna wing longer than the CH-701’s? I do understand that the Savanna can be built with or without a slatted wing and that; the non-slatted wing option is in and of itself longer. As already evident, here opinions vary on the utility of the slat’s as well as the Zenith’s airfoil and glide ratio so until I have the opportunity to fly one myself I will reserve any such opinion. Interestingly enough the company providing the Savanna aircraft kit’s is opening a manufacturing facility here in Middle Tennessee sited in Paris, TN.

Joe
 

Procreator

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Oct 16, 2009
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Yes, Joe, you're correct, the CH-701's wing is shorter by about 2 feet. There's an Aussie or two that has built the 701 with a longer wing and claim the performance has improved.

Just had a look at the Italian ICP web site, it appears that the only Savannah they offer with slats is the ADV. This is a totally different wing, it has retracting slats, slotted Fowler flaps and seperate ailerons and is also used on the Vimana. If you want slats then you'ld have to purchase the Bingo which is the same aircraft except the engines equipped are not 912 Rotax. I suppose when building you could choise either option.

As far as I understand the wingspan is the same for all models(except for maybe the ADV) but the chord would be greater on their VG wing because they extend the leading edge to make it sharper. The slats really don't form part of the airfoil itself so if you were to retrofit the ICP leading edge some consideration to the CG would be in order. Nothing that moving the battery out of the tail wouldn't solve.

If you're fortunate enough to have a facility close you could perhaps try the same aircraft with and without slats. That would be a true apples vs. apples comparison. The Savannah kits are very well done with almost all of the holes drilled and deburred, not bad when you consider there are about 14,000 holes to drill!

The new XL looks nice, larger and considerably faster in cruise without sacrificing the STOL characteristics. I wouldn't mind some more speed but not at the cost of safety so this could be the answer.

Interestingly the new CH-750 uses VG's on the elevator to keep it from stalling on landings... and they look a bunch like the Australian ones!

Let us know when you've flown both models, the more reports from unbiased pilots the better.

Steve
 

bmcj

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Self actuating slats can be spring loaded into an open position so that air pressure at higher speeds pushes them closed or can be designed to be pulled open by the air at high angles of attack. I'm not sure which the Turbine Cub uses.

NOTE: There should always be a physical interconnect between the left and right side slats to prevent asymetrical deployment.
 

K-Rigg

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has the VG mod been done on an actual ch-701 or just the savannah?

The savannah website say they use a different airfoil for the VG version then the slat version.

there using a NACA61058, can someone find the cordinates for this airfoil?
 
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BBerson

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Self actuating slats can be spring loaded into an open position so that air pressure at higher speeds pushes them closed or can be designed to be pulled open by the air at high angles of attack. I'm not sure which the Turbine Cub uses.

NOTE: There should always be a physical interconnect between the left and right side slats to prevent asymetrical deployment.
The Helio Courier has automatic slats and does not have an interconnect. The slats simply move from air pressure without springs. The slats have support tubes that roll on ball bearings. And the Helio also has a large spoiler to augment the aileron.
 

bmcj

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The Helio Courier has automatic slats and does not have an interconnect. The slats simply move from air pressure without springs. The slats have support tubes that roll on ball bearings. And the Helio also has a large spoiler to augment the aileron.
Provided everything works smoothly and freely, I can see that working (maybe even advantages as it would let each wing taylor itself individually), but I would not want to be the pilot if one side stuck closed.
 

Kmccune

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It has been done on a short wing 701 as well. This guy has taken his slats off ( after this video) and loves it. I have communicated with him. Read the STOL speed website, it explains it all.


Kevin
 
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Tom Nalevanko

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The STOL Speed website is a good one. Arguments for removing the slats abound and those macho Columbian pilots were the first to do it.

But movies like this don't really prove anything because we really don't know the plane weight and other conditions...
 

MrHorsepower

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Mar 22, 2006
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As mentioned in previous posts. I have decided to build a 750. I will be removing (scratch building without) the slats in favor of VG's. I have also considered adding about a foot to each wing. I plan on putting it on floats eventually, but plan to do some backcountry flying in the mean time, before moving it up to the lake house. Since I know I'm going to come in a little heavy with a Corvair and floats, I figured I would try to keep the wing loading about the same by adding some ft/sq. I plan to model the wing in SolidWorks and Simulate a strength compairison to the stock using a couple of differant FEA suites that I have access to. Once my finding are complete I will post to the board and let everyone know what I found.
 

Kmccune

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Actually, this airplane still had its slats, as stated. But he is very happy with it now, with out them. If you want to know more, then find out. Don't just pooh-hoo it.

Kevin


The STOL Speed website is a good one. Arguments for removing the slats abound and those macho Columbian pilots were the first to do it.

But movies like this don't really prove anything because we really don't know the plane weight and other conditions...
 

ultralajt

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Slovenia
Hi!

Maybe I miss something, but it seems that nobody try to think that way about improved performance of aeroplane with removed slats and WG mounted on:

Original Zenith wing with slats is a derivate from an "original" airfoil (2 on drawing below). (Think it is NACA series of airfoil)

The outer contour of wing airfoil with slat (1 on drawing below) coresponds to "original" airfoil.

When one take away that slat, he get an totally different airfoil! (3 on drawing below)

This "new" airfoil instantly get higher thicknes, higher chamber and have blunt nose shape.

We all know that:
Thicker airfoils create higher lift coefficient.
Larger chamber airfoils create higher lift coefficient.
Thicker airfoils allow higher angle of attack.
Blunter nose allow higher max angle of attack.

Of course, we shouldnt forget that wing without slats have less wing area and higher wing loading.

So how to find ouut what those wortex generator really improve (behind the test flight results)?

If we test wing with slats (1) against "original airfoil" wing (2) the wing with slats will defenetely achieve higher CL and AOA. It is a winner when slow flight is the case, but looser in economy (higher drag).

But if we put those wortex generators on the "original airfoil" wing, I think, the STOL winer is still the wing with slats.

The story is totally different when using wortex generators on the wing without slats.
That airfoil (as stated above.. thicknes, chamber, nose shape ) already is a high lift airfoil. But because of blunt nose shape,a nd max thicknes placed very far forward, if suffer permature transition to turbulent flow as soon air cross the nose.(airfoil 3 on the drawing below) Placing wortex generators at this point will allow better flowing of the air over upper wing surface. And this creates even higher CL of that airfoil. (airfoil 4 on the drawing below)

The benefit of WG is larger on such airfoils that on an "ordinary" thinner airfoils.

Thats why the results of testing STOL aeroplane by simply removing the slats and adding WG are so amazing. It is not only WG that do that, but the changed airfoil do its best. Both acting together they resulted in such amazing performance.

As that was just my loud thinking, maybe I am wrong.

It would be interested to see the comparision of airfoil data for original airfoil and modified blunt nose airfoil to see the difference in max AOA and max CL. And of course to do some math about aircraft performance...
And afterthat, that same blunt airfoil with WG, to see the improvement in max AOA and max CL.


Regards!

Mitja


P.S.: dont get me wrong! I believe in WG, but just want to point out, that for improved performances both are merited... WG and changed airfoil shape.
And this is only an ice-berg peak that I touch about that matter. Time and space not allows me to go deeper. :gig:
 

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Tom Nalevanko

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Alpine, WY
Hi Mitja,
Thanks for your analysis. I believe if you dig on the STOLSpeed aero site that you can find some data that might lend itself to further analysis.
Blue skies,
Tom
 

CowPilot

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Jul 15, 2010
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K23 USA
Sliding manual-cable-operated battery tray: Forward for takeoff/landing aft for cruise (but still easily landable in most adverse possible extremes).

Cub-style horizontal stabilizer jackscrew. Why not?
 

clanon

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Jun 6, 2007
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I wonder where L/D Ratio goes when you add slats to a regular airfoil? (like that USA 35B)

I'm almost sure you loose lots of L/D...due to increased drag

Anybody...

Here is a nice analysis from a German friend on the 701 airfoil :

http://www.hagenheckel.de/en/Profil_en.html
 
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