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John Bolding
Joined: 23 May 2006
Posts: 281
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 Posted: Thu Sep 04, 2008 7:14 am Post subject: Slats again |
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The little bit of GOOD information I found on the subject 2-3 yrs ago indicated that the best performance increase when slats were incorporated was on airfoils 15% or THINNER. The 65018 is already 18% so in my feeble mind it is like putting lipstick on a pig. I REALLY wish someone with a flying airplane would go to the trouble of building either a new wing with the FULL 65018 or remove their standard 701 leading edge and replace with a full size nose rib.
I'll even beat out the ribs if someone wants to document the results. My airplane will have this mod but life (and $$$ paying projects in the hangar) is getting in the way of steady progress on my 701.
My thought is that because of the fact that the slat has been proved to not contribute much/any (you choose) to lift during cruise, the extra 10 sq. ft. + of wing area you pick up when you put on the full size nose will help on both ends of the speed range (over the bastard airfoil you are left with when you remove the slats). This is just a little better than a wild ass guess but seems to have been born out by the Savannah however. It will also move the center of lift forward a bit which will help with a heavier engine.
For all you float guys out there another thing that bears consideration is the fact that the slats don't really start doing their thing until you reach an AOA that is GREATER than the AOA you can achieve on either landing or takeoff due to the float afterbody.
The question becomes why add weight, complexity, building time, expense etc for something that does absolutely nothing for you. I couldn't find a reason either. Maybe I'm just missing something , certainly happened before.
I fully understand that this gets firmly into the "EXPERIMENTAL" aspect of our hobby and am not suggesting that anybody follow suit without doing their OWN homework.
This has all been hashed over more than once here but few of the newer members (or old ones) search the archives so those that have heard all this drivel before just hit delete.
I also concur with Joe's findings, I flew the 40 hr test time on Brett's 701 and the last few flights were sans slats with VG's (also on the elevator, THOSE help a BUNCH), handled much better on the low end with no loss of short field performance that I could tell.
LO&SLO John
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Joe Kidd
Joined: 01 Aug 2008
Posts: 15
Location: TN
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| Posted: Thu Sep 04, 2008 9:03 am Post subject: Slats again |
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Excellent post John and answer's a question about the 701 airfoil I'd had for some time. I've held off on a 701 build due to the severe trade off in cruise speed for excellent STOL preformance as I knew other's had found alternative solutions that worked very well for them. Guess I'll have to start thinking along the lines of a 701 build in a bit as I am most pleased with it's overall size after a little bit of tweaking for leg and headroom. Sometimes an answer is right in front of you but it has to be pointed out to you by another person. That's called information sharing and it is one of the positive aspects of experimental avaition.
Joe
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vgstol(at)bigpond.net.au
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| Posted: Thu Sep 04, 2008 1:18 pm Post subject: Slats again |
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The little bit of GOOD information I found on the subject 2-3 yrs ago indicated that the best performance increase when slats were incorporated was on airfoils 15% or THINNER. The 65018 is already 18% so in my feeble mind it is like putting lipstick on a pig.
Right on JohnB. This is a subject that's been perculating in my mine lately, and I'm getting ready to write up an analysis when I get the time. When you look at the other aircraft that use slats successfully, Helio Courier, Rallye, Feisler Storch, and the PegaStol wing, all are about 12% thick. And more significantly, very 'lean' on the upper surface of the leading edge - very different from that 18% thick and very 'fat' leading edge of the 701 wing. That sure will affect the airflow thro the slot, and the angle with which it intersects the flow over the top. These other slats also deploy out and below the bottom edge of the wing, which effectively increases the camber of that thinner wing. The 701 originally had the slats mounted so that they projected below the wing, but that caused too much turbulence at cruise for those fixed slats, so they were moved up to where they are now in order to improve cruise. Now have a look at the dramatic effect that slats can have on the Super Cubs with a slim ClarkY or very similar airfoil, see http://www.youtube.com/watch?v=jLa4BikYWtc&feature=related
No 701 can hang on the prop with as much control as this! Very impressive!
Now the flip side of this situation. I've long wondered what the ideal airfoil would be for VGs to have the best effect. Now I'm beginning to realize that that big fat airfoil left behind after the slats are removed from a 701 is just about ideal for VGs. 'Experts' still keep predicting that VGs won't have much effect on a high lift wing... Well, all my experience shows just the opposite - with an airfoil that's already very good at low speed airflow, the VGs put the 'icing on the cake'. That big fat leading edge on the 701 wing turns out to be an ideal platform for VGs. It's a really unexpected but worthwhile discovery.
JohnG
www.stolspeed.com
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kmccune
Joined: 22 Sep 2007
Posts: 577
Location: Wisconsin, USA
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| Posted: Thu Sep 04, 2008 4:14 pm Post subject: Re: Slats again |
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That was amazing!
Kevin
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_________________
“Always do what you are afraid to do.”
R.W. Emerson (1803-1882)
"Real freedom is the sustained act of being an individual." WW - 2009
"Life is a good deal...it's worth it" Feb 1969
Dorothy McCune |
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graeme(at)coletoolcentre.
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| Posted: Thu Sep 04, 2008 5:03 pm Post subject: Slats again |
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WATCHED THE VIDEO.
I WONDER HOW MANY HP THE CUB HAS??
THE CANYON SURFING VIDEO WITH THE 701 IS ALSO GREAT TO WATCH.
GRAEMECNS
[quote] ---
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pdknight
Joined: 14 Aug 2008
Posts: 8
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| Posted: Thu Sep 04, 2008 6:26 pm Post subject: Re: Slats again |
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There is an article about this aircraft in the May 2008 issue of Sport Aviation. Mackey designed it around a Super Cub wing, put 8 ft long flaps and 8 ft long ailerons on it, did mucho pimping on he airframe, and came up with this pretty impressive design. The article stated that it has a 150 hp Lycoming o-320 and an 82" prop. Shows a Vmca of 18 mph at 1450 lbs and 26 mph at 1800 pounds.
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lane_jones(at)bellsouth.n
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| Posted: Thu Sep 04, 2008 9:10 pm Post subject: Slats again |
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here is another interesting one
http://www.youtube.com/watch?v=z985xdXW-3w
Lane Jones
CH 701 3300
Do Not Archive
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lane_jones(at)bellsouth.n
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| Posted: Thu Sep 04, 2008 9:13 pm Post subject: Slats again |
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[quote] ---
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ggower_99(at)yahoo.com
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| Posted: Fri Sep 05, 2008 7:20 am Post subject: Slats again |
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No 701 can hang on the prop with as much control as this! Very impressive!
Apples to apples, that was not a STOL airplane, was an Helicopter 
Saludos
Gary Gower.
Flying a STOL airplane from Chapala, Mexico.
--- On Thu, 9/4/08, Graeme <graeme(at)coletoolcentre.com.au> wrote:
[quote]From: Graeme <graeme(at)coletoolcentre.com.au>
Subject: Re: Slats again
To: zenith701801-list(at)matronics.com
Date: Thursday, September 4, 2008, 8:59 PM
WATCHED THE VIDEO.
I WONDER HOW MANY HP THE CUB HAS??
THE CANYON SURFING VIDEO WITH THE 701 IS ALSO GREAT TO WATCH.
GRAEMECNS
[quote] ---
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