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ronlee

Joined: 25 Dec 2006
Posts: 141

Posted: Tue Dec 26, 2006 12:47 pm Post subject: Re: vg's

I now have over three hours flying time and several landings on my 701 with the slats removed and VG's on. I have over 75 hours in/on this plane. At this time I see no reason to ever put the slats back on. I will leave the mounting tabs on, as some day when I sell the new owner may want to try the slats. I have lots of them, (56 VG's) on each wing They are placed in the CCI pattern, which is, 2 close together then about a 5" inch gap and so on. The leading edge of the VG's is ten percent back from the leading edge of the wing chord, which includes the flaperons, but not the slats. My plane is ever so much easier to land. It sure feels like it climbs better. No stall just the mush as before. Trims are identical as with the slats on. If I didn't look out the window in flight I would never know the slats were missing. I think I have more VG's on then I would need though, as a result I may be getting some drag as I only gained 4-5 miles per hour at the same RPM. One thing I did lose is the uniqueness of the plane. Those slats are a real attention getter and conversation item. Could it be that's why Zenith retains them? Of course if a designer were to put VG's on his plane it would look like he/she was trying to correct something!

_________________
Ron Lee
Tucson, Arizona

billbutlergps(at)aim.com
Guest

Posted: Tue Dec 26, 2006 1:15 pm Post subject: vg's

Ron, 

 If the new owner doesn't want the forward slats give me an email and I will.

 Bill

 

   

  

 --

robert.eli(at)adelphia.ne
Guest

Posted: Tue Dec 26, 2006 1:15 pm Post subject: vg's

Ron,



Thanks for your report on removing the slats.  It is interesting that your 

experiences seem to parallel the experience of others regarding the equal or 

improved landing/takeoff, cruise, and stall behavior.  How about any 

differences in the takeoff and landing roll distances?



Bob Eli



---

jpspencer(at)cableone.net
Guest

Posted: Tue Dec 26, 2006 1:29 pm Post subject: VG's

I just cut the slat brackets off my 701. I was  able to match the claims of the our Aussie friends. The thing I found on my 701 was that the slats  aren't active on approach unless the plane is forced into a high AOA, high  drag attitude and kept there thruout the approach/landing(dragged in)-not  usually considered good form for all the obvious and well known reasons unless  necessary for high priority mission reasons of some sort. Also when the slats  aren't active my plane was unstable on approach unless flown at Cessna 150  like speeds-hardly stylish for a proper STOL plane. Along with the rather nasty  stability issue there was all sorts of airframe buffet with the slats on. The  vgs fixed all the above and made my 701 what I consider to be a decent flying  airplane-I couldn't say that when the slats were on it.

 I've got something like 16 pages of flight test  data. I consulted with an aero engineer on a possible structural issue  here. The only downside I could find was that on takeoff I do believe you  lose a minute amount to the slats(difficult to get any flight test numbers  on this) but it's hardly relevant(except for showing off) since the thing  will still come out in about a third of what it takes for a max effort  landing(with the vgs in just the right position-I found placement to be  important).I have followed all the recent posts on vgs and considered their  merit before deciding what was right for me. What I noticed was that most  of the more opinionated posts came from those who had never flown a 701  much less tried to do an objective before/after evaluation. At any rate I  decided that the right thing for me was to cut the slat hangers off and bondo  the holes up. 

 Aviation folks being what they are I know you will  decide what's right for you-thats what i did.

 Joe



   [quote][b]

Float Flyr

Joined: 19 Jul 2006
Posts: 2704
Location: Campbellton, Newfoundland

Posted: Tue Dec 26, 2006 1:53 pm Post subject: vg's

Just like trim tabs and slats... Right!



VGs are just another tool to help planes fly better.  Some need 'em some

don't.  Depends not only on the plane but also the use of the plane.   E.g.

speed vs. STOL

I almost forgot Do not archive again.



Noel



 Of course if a designer were to put 

 	  Quote: 	
		   VG's on his plane it would look like he/she was trying to 

 correct something!

 

 --------

 Ron Lee

 Tucson, Arizona

_________________
Noel Loveys
Kitfox III-A
Aerocet 1100 Floats

Float Flyr

Joined: 19 Jul 2006
Posts: 2704
Location: Campbellton, Newfoundland

Posted: Tue Dec 26, 2006 5:04 pm Post subject: VG's

Don't cut too fast... one of  those slat hangars could make a nice camera mount.   or even a landing  light mount.

  

  

 

Noel [quote]   

   --

_________________
Noel Loveys
Kitfox III-A
Aerocet 1100 Floats

robert.eli(at)adelphia.ne
Guest

Posted: Tue Dec 26, 2006 5:15 pm Post subject: VG's

Bully for you Joe,

  

 One question - you said that you found that  positioning the VG's is critical. What position, in terms of % chord (or  some other suitable reference) did you find gives the best  performance?

  

 Bob Eli

 N701K

 [quote]   ---

raymondj(at)frontiernet.n
Guest

Posted: Tue Dec 26, 2006 7:51 pm Post subject: vg's

Ron,



	Have you experienced any change in your angle of climb (Vy)?



Thanks,

Raymond Julian

Kettle River, MN.



--

jpspencer(at)cableone.net
Guest

Posted: Wed Dec 27, 2006 6:07 am Post subject: VG's

As for placement I tried 12%, 10%, and 8%. I  settled on 8 %(LE of VG at 147mm forward of rivet line on top of spar on my  plane). 12% was too far back. At 10% on an extremely aggressive takeoff rotation  the vgs would occasionally "uncover" and result in an extended takeoff roll. I  haven't been able to force this situation at 8%.

 I would stress that it is important to do your own  flight testing before making this commitment as each of these planes is  different and your results may vary considerably from mine.

 Good Luck

 Joe

   [quote][b]

jpspencer(at)cableone.net
Guest

Posted: Wed Dec 27, 2006 7:13 am Post subject: VG's

Forgot to mention on my last post that I am looking  for some sort of CG range data for the slatless wing-if anybody has or knows  would appreciate it

 BTW the last paragraph on my last post wasn't some  BS liability disclaimer-it's real.

 Happy New Year

 Joe

   [quote][b]

daveaustin2(at)can.rogers
Guest

Posted: Wed Dec 27, 2006 7:23 am Post subject: VG's

Re VG positioning..

 I'd recommend you put more (closer together) VGs  out at the wingtips to help make sure the inner wing stalls first.  JMHO.

 Dave Austin  601HDS - 912, Spitfire Mk  VIII

     [quote][b]

vgstol(at)bigpond.net.au
Guest

Posted: Wed Dec 27, 2006 4:18 pm Post subject: VG's

<I am  looking for some sort of CG range data for the <slatless wing-if anybody has  or knows would appreciate it 

  

We have three slatless 701’s at  our airfield, and some experience with adjusting CofG. 

<?xml:namespace prefix = o ns =  "urn:schemas-microsoft-com:office:office" />  

Hans’ (912S) weighs in at 503kg  (1107lb) at 26% m.a.c., loaded for travel, with 82kg (180lb) pilot, 95litres  (25gal) fuel in wing tanks, two jerrycans of fuel 28kg (62lb) on pax seat, and  20kg (44lb) baggage.   

  

Gene’s (912) weighs in at 496kg  (1091lb) at 25% m.a.c., loaded the same as above. 

  

Hans’ and Gene’s were actually  weighed in that loaded condition on professional scales. 

  

Phil’s (912) was weighed empty,  and the loaded conditions calculated.   It weighed in empty at 283kg (623lb) at 22% m.a.c.  This a/c has the original 40litre  (10.6gal) fuel tank forward in the cowl, and 40litre (10.6gal) in the  wings.  Calculating the most forward  CofG, (single pilot 82kg and full forward fuel), gives CofG at 21% m.a.c.  Calculating full load CofG, (full fuel  (80litres), pilot 82kg, pax 82kg, no baggage),  gives 502kg (1109lb) at 28% m.a.c.  Due to that forward fuel tank we had to  put the battery right back in the tail to get the most forward CofG to 21%,  which is still quite far forward......   This a/c has a history, in that when we bought it in a crashed condition  the battery was forward of the firewall, so what was the actual CofG!  The crash occurred when a ferry pilot,  unfamiliar with 701’s, tried to take off from a short strip and then tried to  abort too late when the aircraft didn’t want to rotate easily........  More detail on that in a separate post –  there’s lessons there I think.   

  

Of the three aircraft, Phil’s  balances the best with a CofG at about 27% (pilot + pax + part fuel),  Hans’ balances well at 26%, and Gene’s  feels just a little bit nose heavy at 25%.   This is testing the balance in glide, and the ability to  flare comfortably at idle power.   The next testing we will be doing is to adjust Gene’s to 27% to see if it  feels better there...... 

  

Wishing fair skies and tailwinds  all year. 

JG

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