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John Bolding
Joined: 23 May 2006
Posts: 281
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 Posted: Thu Dec 14, 2006 6:11 am Post subject: : Re: vg's |
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This simple picture provides some important information to those who are actually seeking substantiated data on this mod.
If one looks at the height of the wheels off the ground compared to the height of the tail off the ground it is perceived(by me anyway) that the AOA is slightly less than what is achievable with slats.
I know, I know, camera angle will also come into play here but it IS a good picture to start with.
This can be from two reasons I THINK.
One : that's all the AOA you can get with VG's on this aircraft and the STOL performance will be reduced by some unknown value over slats.
Two : the picture was snapped at an instant in the flare where full AOA had not yet been achieved and there is more to come.
AOA is not all encompassing either.
If the same lift can be had at a shallower AOA you could see better on approach and the float guys would love you as you can't get max. performance from the slatted wing unless you have the floats rigged nose low causing a LOT of cruise drag.
I try not to tell people how to run their business BUT if I wanted to sell to this tough crowd I'd have more pictures and several clips on YouTube, maybe a couple 701's (or Savannah's) side by side, one with slats the other with VG's doing a drag race T.O. Many folks are visual learners, SOME are from Missouri. 
I UNDERSTAND that other issues (handling, structural,weight,etc) are involved here, I'm just discussing the STOL performance aspect.
To those who have made up their mind on this issue I can only say "Congratulations" . MANY have not and this thread ain't going away anytime soon.
Beats the hell out of talking about scotchbrite or insurance.
LOW&SLOW John Bolding
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billmileski
Joined: 07 Aug 2006
Posts: 68
Location: Ledyard, CT
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| Posted: Thu Dec 14, 2006 8:10 am Post subject: Re: : Re: vg's |
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John,
I have the same kinds of questions. I am wondering if without slats, the max angle of attack may be slightly less, and with a little reduced drag too, the landing distance may suffer a bit. Testing ought to include takeoff and landing distance estimates (hard to do without help, consistent conditions, etc.).
It also occurred to me that some of us have limited our max flap angles to only 15 degrees. If I remember correctly, the factory cautioned use of the original 30 degree option, because the overall drag was so high that max STOL landings required great timing, or one risked a pretty hard landing. I know my 15 degree setting seems to reduce stall speed, but not add much drag at all (going by indicated sink rates). So now I wonder how the VG-only configuration could do if the 30 degree notch was reintroduced. Or upped to 35 or 40 degrees (a possible pandora's box, admittedly, as airflow over the tail, stability, etc., all would have to be revisited). Guess this train of thought may add to the confusion.
Bill Mileski
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nyterminat(at)aol.com
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| Posted: Thu Dec 14, 2006 9:11 am Post subject: : Re: vg's |
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Bill,
That is a very valid point and it would be great to have someone with vg's experiment with 40 degrees of flaps.
Bob Spudis
In a message dated 12/14/06 11:12:58 Eastern Standard Time, mileski(at)sonalysts.com writes:
| Quote: | So now I wonder how the VG-only configuration could do if the 30 degree notch was reintroduced. Or upped to 35 or 40 degrees (a possible pandora's box, admittedly, as airflow over the tail, stability, etc., all would have to be revisited). Guess this train of thought may add to the confusion.
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vgstol(at)bigpond.net.au
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| Posted: Thu Dec 14, 2006 7:02 pm Post subject: : Re: vg's |
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Yeh, Bill, good point. The flaps on my Savannah without slats now give
almost no drag at all, even at full flap.. I wish I had more, cause it
tends to float and float in ground effect - more like a glider than a
701...... Someday I want to experiment with much higher angle flaps that
have no detent and I can pull on only in the last stage of hold-off to
bring in drag and dump lift, to get it to sit down.....
JG
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