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Those fuselage mounted vortex generators? Strakes RV-8

claycookiemonster

Well Known Member
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.
 
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.
 
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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Thanks. Kinda like asking why there haven't been any new threads about dinosaurs. If you have to ask, you already know the answer.
 
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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Doesn't Cirrus Use Them?

Isn't that what Cirrus is going for here?
 

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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.
 
+1 on additional info on your install. Are there pre-made strakes out there? Or is this a full custom mod?
 
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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My RV-8 has the strakes as well. I don't know any different, but my airplane is capable of being three-pointed. My friends who've flown my airplane, as well as their own without the strakes have noted quite a difference in the flare.
 
Generally, aerodynamically, for everything you get, you often give up something else. Those strakes are small enough to not be a weight issue, but perhaps a slight speed loss? Clearly, if they assist in three-pointing, they help with higher AOA and slower speeds. How are they when you're tail-chasing your buddy at higher than landing speeds? Has anyone modified their upper intersection fairings in any way to work with the strakes?

If they were without a downside, everyone would have them.
 
When I was flying with Bruce Bohannon back in October, we accidentally figured out that the tiniest touch of power in the flare seems to break up these vortices. You get a smooth 3 point and no tail wiggle.
 
Does anybody have another supplier for strakes, I called micraero and they told me they only sell the strakes as part of a kit that includes vortex generators for $395. I only want to try the strakes.
 
Roll Your Own Strakes?

Question: If I try to create a RV8 specific wing leading edge strakes, can I create from a mold of the leading edge? Is there any consideration if I plan to roll my own version? The strakes in the pictures don't follow the leading edge profile but I suppose there is a reason for that. Any online reference I should look into?

Thanks.
 
Question: If I try to create a RV8 specific wing leading edge strakes, can I create from a mold of the leading edge? Is there any consideration if I plan to roll my own version? The strakes in the pictures don't follow the leading edge profile but I suppose there is a reason for that. Any online reference I should look into?

Thanks.

Unable to provide any advice on the creating your own, shape or placement - I'm sure the company that sells them tested the fluid mechanics to some degree for safety reasons. They also don't need to be the shape of the leading edge as it serves a different purpose.

I searched ebay for the part number and found these results - they seem to be similar to the ones on the RV-8. https://www.ebay.com/sch/i.html?_fr...57.m570.l1313&_nkw=cessna+310+strake&_sacat=0
 
The strakes came factory installed on the Cessna T303, would not take much effort to reproduce a set by tracing a paper template.
Bend a 90 on a piece of Aluminum and stretch the small edge to form the shape.
 
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