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Strakes

Wardo

Active Member
Any good info on where to buy a set of strakes that mount on the fuselage forward and above the leading edge of wings.
 
why?

Wardo, someone is going to ask you this (because its a valid question), so I might as well be that guy.

Why in the world would you want to do that?

Maybe they're out there, but I've never seen strakes on any RV.
 
When I was building my -8 back about 7 years ago, there were a number of folks that recommended strakes to smooth the flow over the wing root and prevent "tail shake" in the stall. Then others reported that the tail shake was present only when they were flying without upper intersection fairings, and when they installed those, the shake went away. I think back then, it was more common for folks to "get flying" before they finished the gear fairings (probably because there were few - or no - sources for pre-made fairings, and builders hated making glass parts from scratch), so there was more discussion of the phenomenon.

I have seen little to no reference to the stall/tail shake in the -8 in more recent years, and I attribute it to the fact that most people are doing their intersection fairings before first flight. This has, in turn, led to less talk about the strakes, as they appear to be unnecessary.

This is all a good argument for not doing Phase 1 until you are in a "final" aerodynamic configuration - otherwise, you just need to re-do it....

Anyway, that's a little history as I remember it!
 
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no tail shake

I have not experienced a "tail shake" during stalls/spins in any configuration without strakes - I do have intersection fairings installed.

FWIW
 
RV-8 Strakes

When I first started flying my RV-8 in late 2001 (with upper gear leg fairing installed) and doing all my initial Phase 1 checks, I noted that there was a significant shake just before reaching a stall. In looking around to see what was causing the shake I saw that the left and right horizontal stabs were shaking up and down, maybe 1 to 1 1/2 inches. I figured it was coming from dirty air coming up from the gear legs at that high angle of attack and hitting the horizontal stabs. I installed some strakes on both sides of the fuselage just in front of the leading edge to re-energize the air coming around the gear legs. Next flight, no shake prior to the stall or into the stall. No stall warning at all. In further exploring, I found that my Indicated stall speed was 5 kts slower and there was no top end speed penalty. I have been flying with them ever since.

Some people may not want to install these strakes as it takes away all indications of an impending stall.
 
RV-8 Strakes

Stu, can you tell us the fabrication and install dimensions?

As I remember, they are Cessna 410 (maybe 421) engine nacelle strakes which I reworked to get the right curvature against the fuselage. Two screws, first of which went into drilled out rivet hole at the junction of vertical and horizontal rivet lines just above and forward of the leading edge at wing root. Second screw was so that I had about a 1 1/4 inch space from top of wing to bottom of strake at its aft overhang.
 
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Couple pics from LOE '06

img1240tr.jpg


img1239q.jpg
 
A few VG's on the inboard section of wing will do the same thing. Keeps the inboard wing section active at high AOA. Did it to my four, but it lowered stall so much it floated too much. I took them back off.
On the up side, NO ONE could turn with me.... So there was that.. :)

Dm
 
Carl, I noticed you have strakes and VG's. Can you tell us how each affected performance and flying qualities?
 
Dan, the builder of my RV-8 tested with the strakes and later added (and then removed VGs). He expressed that his VGs did not measurably improve any characteristics of flight.

Carl - do you have before&after experiences. I too am interested in your comments.
 
strakes

a response to me

Marc;
I flew the RV-8 this morning for the first time since I installed the strakes. Wow, what a difference in the landings. I made three landings here and at Omak, and it is now very docile, even in three point landings. The attached picture is of--- landing at Okanogan, and he agrees it is a great improvement in landings.
 
Another data point

I started my Phase I testing without intersection fairings (or any other gear fairings) and had a nice stall, nothing alarming.

After I put the gear fairings and intersection fairings on, I found a very strange sound more than feel just at stall. I don't get any tail shake, but a funny whooshing sound and slight vibration in the side of the fuselage that I believe is the vortex forming at the gear junction and running by the side of the cockpit.

I know this is odd - the reverse of common experience. Also, my stall speed seems high, but I have not thoroughly chased out any possible leaks in the static system. The instrument reads 3 kts high at 55 kt, and my "indicated" stall speed with flaps UP is 61 kts.

So, I don't know if I hit some magic shape with my intersection fairings that does this -- they look about like everyone else's. I've been thinking about adding the strakes.
 
We used strakes in an identical manor on a Pitts S1t experimental. The stock fabric covered gear had no problems, but when that was changed to aluminum gear; it limited max G in high G pulls. Adding the strakes got you about one G more, before onset of buffet, in a pull. Similar science but on a different airframe.
 
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