Vortex Generators

Discussion area for builders of Pietenpol aircraft, both beginners and experienced folks. Share ideas, ask questions and help build the Pietenpol community.
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douwe blumberg
Posts: 24
Joined: Sun Mar 05, 2017 5:46 pm

Vortex Generators

Post by douwe blumberg » Sun Mar 05, 2017 5:55 pm

well, here's my first official post! what a great new website, I think it is going to be a huge boon!!

after sitting in a bag on my workbench for two years while I procrastinated, I finally went a head and installed VG's on "RE-PIET" and flew her for the first time today. I had debated and debated then after my talks with PF Beck, decided to bite the bullet. After my first flight I'm really pleased. Can't tell how much, because of the Johnson vane-type airspeed indicator, but my stall speed has been reduced noticeably. She's always stalled very mildly, but just above stall she's pretty much "rock solid". The slowest I used to be able to maintain altitude was around 1700rpm, how I think she's maintaining altitude in the 1500's. Don't notice a reduction in cruise speed.

Overall, I'm stoked. they're small and clear so they're hard to see, though you can see them at three-point attitude if you step back and that certainly isn't vintage, but I think it's worth it.

Douwe

Steve D
Posts: 50
Joined: Sun Mar 05, 2017 9:50 pm
Location: Grand Republic of Texas

Re: Vortex Generators

Post by Steve D » Sun Mar 05, 2017 10:22 pm

Douwe, try using a GPS with stalls done into and with the wind. The average should be pretty good.

douwe blumberg
Posts: 24
Joined: Sun Mar 05, 2017 5:46 pm

Re: Vortex Generators

Post by douwe blumberg » Mon Mar 06, 2017 9:08 am

yep, gotta do that. will report back

habickford
Posts: 8
Joined: Fri Mar 03, 2017 9:58 am

Re: Vortex Generators

Post by habickford » Mon Mar 06, 2017 11:30 am

Douwe,

How far back from the L.E. did you position the VGs for the initial testing? As I recall you use the standard Piet airfoil..........

thanks,
Harold

Steve D
Posts: 50
Joined: Sun Mar 05, 2017 9:50 pm
Location: Grand Republic of Texas

Re: Vortex Generators

Post by Steve D » Mon Mar 06, 2017 8:28 pm

Beechcraft Bonanzas have been putting on VGs for years and the general consensus is:

You lose 1-2 Knots cruise speed.
You get 4-6 Knot slower stall speed.
The real advantage is that the planes seem to become more controllable in slow flight. And stalls are gentler.

M2C
Steve D

KTOWN
Posts: 2
Joined: Mon Mar 06, 2017 11:35 pm

Re: Vortex Generators

Post by KTOWN » Mon Mar 06, 2017 11:44 pm

Douwe,

Just registered on this site...been following you and much of the group on the Matronics site, but lurking in the weeds there. I just signed up for a 2-year subscription! I hope to start posting about my build, but just started training for a new job today!

Any chance you could attach a few photos and where you got the VG's? I'm 90% completed with "The Piety Project" (my affectionate name for my build), which means I only have 90% to go. I'm close to slapping rags on my sticks and need to know if the VGs should go on first or after! If after...then I won't need to be in a rush to put them on!

Cheers,
KTOWN
"The Piety Project"
(soon to be "The Fabulous Princess Di"...when completed)
Wire Wheeled Air Camper/Grega hybrid
O-290G conversion powered
Reserved Tail Number N694YU
Lancaster/Rosamond CA area

douwe blumberg
Posts: 24
Joined: Sun Mar 05, 2017 5:46 pm

Re: Vortex Generators

Post by douwe blumberg » Tue Mar 07, 2017 4:25 pm

the VG instructions recommended about 10% of the cord back from the leading edge which in a piet was about 6" back to the middle of the VG. seemed to work.

just cover your plane and if you ever decided to put some on, it's a simple matter of glueing them on. I'd say fly it first and then decide if the tiny bit of improvement is worth it. I like it, but that's just me

Douwe

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taildrags
Posts: 283
Joined: Tue Mar 07, 2017 10:39 pm

Re: Vortex Generators

Post by taildrags » Tue Mar 07, 2017 10:56 pm

My first post to this discussion board... just signed up and just renewed my newsletter subscription, so I'd better stay alive for another 2 years to get all my money's worth out of it ;o)

Discussing the VGs with Joa Harrison, who designed and manufactures the Landshorter molded polycarbonate VGs, he said that the noticeable improvement in his back-country and unimproved strip flying in Idaho came from installing them on the horizontal stabilizer as well. I don't recall whether they go on the upper surface or on the underside, but that's in the instructions that come with the VGs from Landshorter. The improvement is in low-speed handling near the stall and in ground effect. The ones on the upper surface of the wing will of course also improve airflow adhesion at higher angles of attack and improve aileron authority in those flight regimes.

I have heard people use double-sided tape on the aircraft surfaces to adhere the VGs in place in a semi-permanent fashion that would allow them to be removed later if the desired results weren't achieved or if the appearance didn't satisfy. Over on the KRNet, some years ago there was a lot of discussion about installing aileron gap seals and the method was to use strips of medium-stiff Mylar film attached to the wing with 3M double-sided tape (I forget the 3M product number but could look it up), on the leading edge of the gap seal, with the trailing edge free to follow the control surface as it moved. I suppose the same tape could be laid down along the wing and tail surfaces and the VGs adhered in place for test flights. At higher speeds (higher than the Air Camper), even the edge of a a very thin tape can act as a tripping surface for laminar flow, but I doubt that that would be the case with our airplanes.

Thanks, everyone.

-Oscar

douwe blumberg
Posts: 24
Joined: Sun Mar 05, 2017 5:46 pm

Re: Vortex Generators

Post by douwe blumberg » Wed Mar 08, 2017 3:51 pm

a temp suggestion in the instructions is two-sided carpet tape.

I bought enough to do the underside of the elevator just before the hinges, but elevator control remained strong even at stall speeds so it is apparently not needed on a pietenpol. Other's mileage may vary.

I may still install them there because... why not? you can't see them.

I would imagine a possible impact at cruise speeds with a very fast, aerodynamic airframe. One a piet, I didn't see ANY noticeable reduction, nor did P.F. Beck who's been flying his for almost a decade.

Douwe

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cdnCruZer
Posts: 1
Joined: Wed Mar 08, 2017 3:59 pm
Location: East St. Paul, MB Canada

Re: Vortex Generators

Post by cdnCruZer » Wed Mar 08, 2017 4:11 pm

For you guys that would like some more info... check out - StolSpeed at
http://www.stolspeed.com/id/3

I built mine out of 0.025 6161 alumnum! Here is my web page!
http://www.ronleclerc.net/vortex-gen.html
Ron
CH750Cruzer
Ron
CH750CruZer

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