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R. Hankins
Joined: 18 Jan 2006
Posts: 185
Location: Grants Pass, Oregon
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 Posted: Sat Sep 08, 2012 1:55 pm Post subject: STOL Speed VG's |
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I finally got the STOL Speed VG's installed on my Firestar KXP. They are a lot less obtrusive than the homemade ones and look a lot better. I went out and put the firestar through it's paces after the install and am very happy with the results. I installed 105 VG's on the wings and 20 on the underside of the horizontal stabilizer trailing edge (10 per side). Larry Cottrell added VG's to his elevator and recommended I try it.
The results were positive. I have more elevator authority (didn't feel lacking before, but it is awesome now),a slighly slower stall speed compared to the home made VG's and a more gentle stall. I flew lots of power off stalls, power on mushes (it won't stall at full power) and tight turns in both directions 'til I was dizzy. Suffice it to say that I have gone to the dark side. I was OK with VG's before, but now I'm a true believer. The STOL-speed VG's look better than my home made versions, and the results are a bit better as well.
Power off stall speed went down slightly from 34 to 32mph indicated, but control authority in the elevator and ailerons was noticeably better. Part of the improvement, I think, is due to having VG's installed all the way out to the wing tips and using closer spacing out at the tips. I can hold the firestar in a stall now without one wing wanting to drop. This is how it performed before any VG's were installed. The homemade VG's made this a bit worse, kind of like balancing on a ball. With the Stolspeed VG's I have my original Firestar handling back, but with the lower stall speed of VG's. The differences aren't huge, but they are definitely noticeable and positive. If you are interested, visit Stolspeed.com for more information.
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Roger in Oregon
1992 KXP 503 - N1782C |
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russk50(at)gmail.com
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| Posted: Sat Sep 08, 2012 3:14 pm Post subject: STOL Speed VG's |
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Thanx all that info on VG's. Who suggested putting them in the trailing edge of the hor. stab?
do not archive
On Sep 8, 2012, at 5:55 PM, R. Hankins wrote:
| Quote: |
I finally got the STOL Speed VG's installed on my Firestar KXP. They are a lot less obtrusive than the homemade ones and look a lot better. I went out and put the firestar through it's paces after the install and am very happy with the results. I installed 105 VG's on the wings and 20 on the underside of the horizontal stabilizer trailing edge (10 per side). Larry Cottrell added VG's to his elevator and recommended I try it.
The results were positive. I have more elevator authority (didn't feel lacking before, but it is awesome now),a slighly slower stall speed compared to the home made VG's and a more gentle stall. I flew lots of power off stalls, power on mushes (it won't stall at full power) and tight turns in both directions 'til I was dizzy. Suffice it to say that I have gone to the dark side. I was OK with VG's before, but now I'm a true believer. The STOL-speed VG's look better than my home made versions, and the results are a bit better as well.
Power off stall speed went down slightly from 34 to 32mph indicated, but control authority in the elevator and ailerons was noticeably better. Part of the improvement, I think, is due to having VG's installed all the way out to the wing tips and using closer spacing out at the tips. I can hold the firestar in a stall now without one wing wanting to drop. This is how it performed before any VG's were installed. The homemade VG's made this a bit worse, kind of like balancing on a ball. With the Stolspeed VG's I have my original Firestar handling back, but with the lower stall speed of VG's. The differences aren't huge, but they are definitely noticeable and positive. If you are interested, visit Stolspeed.com for more information.
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Roger in Oregon
1992 KXP 503 - N1782C
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R. Hankins
Joined: 18 Jan 2006
Posts: 185
Location: Grants Pass, Oregon
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| Posted: Sat Sep 08, 2012 9:36 pm Post subject: Re: STOL Speed VG's |
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Well I guess I could have been more specific in my first post. I said that Larry had put VG's on his elevators. What I meant is that he put them on the underside trailing edge of his horizontal stabilizer, which is the correct location if one is trying to increase elevator authority in the nose up direction. As I said, he recommended them and now that I have tried them, I can see why he did.
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Roger in Oregon
1992 KXP 503 - N1782C |
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Dennis.Kirby(at)kirtland.
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| Posted: Tue Sep 11, 2012 8:32 am Post subject: STOL Speed VG's |
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kinne russ asked:
<< Who suggested putting them in the trailing edge of the hor. stab? >>
Russ –
Placing VG’s on the underside of the H.stabilizer – just ahead of the elevator hinge line – has been an oft-suggested bit of advice for a long time.
The idea is, since your plane now stalls at a lower speed, you’ll likely be at a somewhat higher angle of attack, just before stall. Many folks have observed that, at this high AoA, they begin to lose up-elevator effectiveness at the airplane approaches stall speed. Airflow flowing aft from the stab is separating at the hinge line because of the steep deflection of your elevator. Placing several VGs just ahead of the elevator keeps the airflow “connected” as it flows past the elevator hinge line, thus maintaining elevator authority all the way down to below stall speed.
I installed VGs on my Mark-3 last fall, including on the stab. Although I was not losing elevator authority prior to installing them, I did notice that, after installing VGs there, my pitch authority just before touchdown was now a bit more sensitive. Not a bad thing – forces me to be more precise in my elevator movements to get that smooth touchdown!
Dennis Kirby
Mark-3, 912
New Mexico
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