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  #1  
Old 12-21-2021, 08:59 PM
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claycookiemonster claycookiemonster is offline
 
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Default Those fuselage mounted vortex generators? Strakes RV-8

I seem to remember a flurry of interest years ago in mounting a small vortex generator just forward of the leading edge of the wing on the side of the Fuse? It was supposed to reduce stall speed? Perhaps also moderate some airflow issues around the wing and gear leg intersection.

I haven't seem any mention of it recently. Is the lack of recent posts everything I need to know about it?

It did look cool.
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  #2  
Old 12-21-2021, 09:32 PM
Sam_B Sam_B is offline
 
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Default Strakes

Search VAF for the word ‘strakes’.

I think they took away a tail shake when builders didn’t finish gear fairings or something like that, but I really don’t know much about them. Good luck.
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  #3  
Old 12-21-2021, 11:10 PM
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Quote:
Originally Posted by Sam_B View Post
Search VAF for the word ‘strakes’.

I think they took away a tail shake when builders didn’t finish gear fairings or something like that, but I really don’t know much about them. Good luck.
Strakes were a common topic of discussion back when I was finishing my -8….but folks discovered that upper intersection fairings did the same thing as the strakes, and reduced drag to boot…haven’t seen many people doing strakes since then (maybe fifteen years ago….)

Paul
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Last edited by Ironflight : 12-26-2021 at 08:34 AM.
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  #4  
Old 12-22-2021, 07:22 AM
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Thanks. Kinda like asking why there haven't been any new threads about dinosaurs. If you have to ask, you already know the answer.
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  #5  
Old 12-22-2021, 08:52 AM
michjor michjor is offline
 
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Quote:
Originally Posted by claycookiemonster View Post
Thanks. Kinda like asking why there haven't been any new threads about dinosaurs. If you have to ask, you already know the answer.
I just installed a pair in my RV-8 after alot of research (speaking with original RV designer, reading Vans testing document, plus others) and flying a couple of different RV's. They are not necessary but do make a difference in 2 areas for me. The upper leg intersection fairing must be a certain shape to assist as there are several versions and not all are the same. Only the -8's of the RV family experience this due to the placement of the gear legs with the leading edge of the wing.

You can fly without them and will notice at high angle of attack and onset of stall speeds what's called "RV-8 tail shake", tail buffeting stall before the wing root stall. Consider it's use as a poor man's pre-stall warning stick shake. It also skews the true stall speed calcs if you are new to the RV and unsure where the buffeting is coming from.

After installation of the strakes, I no longer have the tail shake stalling effect and the true wing stall onset is +/- 4 knots slower and the break more "aggressive" than before. I had to redo my true stall speed in the POH.

My favorite application of the strakes is the landings, it's reduced the mushy feeling at high angle of attack in the pitch and yaw as I touch down and have more control authority to make much better landings. I was amazed at the difference and really glad I added them. Practically removed the "RV dropin" affect. And I do have the intersection fairings that supposedly eliminated the use of strakes but found in application it's not 100% true.

As a builder I'd recommend, if you may in the future add them, to install during build then remove them so you have the fittings ready to go. Then complete phase 1 without the strakes, get the rigging straight and true, the POH nailed down, etc and move into phase 2. After +/- 50 hours of getting to know your plane add the strakes, you'll feel the difference and hone in your landings to leverage their value and revaluate your slow flight characteristics and stall speeds.
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Last edited by michjor : 12-22-2021 at 10:13 AM.
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  #6  
Old 12-25-2021, 12:10 PM
Lt Dan Lt Dan is offline
 
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Default Doesn't Cirrus Use Them?

Isn't that what Cirrus is going for here?
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  #7  
Old 12-26-2021, 01:10 AM
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Bruce Bohannon installed a set of strakes on his trainer RV-8 so the aircraft can be 3-pointed at every landing. Swears by them. He uses the aircraft for transition training and has full dual controls in the back seat.
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  #8  
Old 12-26-2021, 06:47 AM
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Quote:
Originally Posted by michjor View Post
I just installed a pair in my RV-8 after a lot of research ....
Michael, where does one find the testing document, and plans or pictures of the best version?
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  #9  
Old 12-26-2021, 08:15 AM
Presmini Presmini is offline
 
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+1 on additional info on your install. Are there pre-made strakes out there? Or is this a full custom mod?
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  #10  
Old 12-26-2021, 09:44 AM
michjor michjor is offline
 
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I looked through my notes, most of them cut and paste from articles I read to keep it concise. I pasted them into this PDF document. It includes the original findings from a builder who contacted Vans, the Vans testing (from an article in a magazine), Ken's comments (RV designer) and couple of pics. https://1drv.ms/b/s!Ah_qaedfmDRBmksPoItXtdKGQ0x_

Cool, found the old invoice, you can order the strakes from Micro AeroDynamics at microaero.com https://microaero.com/?s=strake . You'll need to call them to make sure you get the ones for the RV-8 (5001-1 Left and 5001-2 Right).
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Last edited by michjor : 12-26-2021 at 10:43 AM.
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