Wendell111
Member
Has anyone used strakes to reduce stall speed? Here is a Sonerai for sale I am interested in. I have arbitrarily set my stall criteria under 55mph and the Sonerai is considerably more.
Thanks
Wendell
Thanks
Wendell
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Strakes
- Thread starter Wendell111
- Start date
dcstrng
Well-Known Member
Wendell; I'm probably not understanding what you mean by a strake -- often you'll see them on higher performance aircraft, not so much to lower the stall speed -- not a lot of effect on that generally, but as a means of encouraging vortex lift and thus allowing a wing to hang on at higher angles of attack...
At least one theory is that they are simply a means of achieving a localized, very-low aspect ratio, which by their nature aren't terribly efficient, but but will hang on at higher angles of attack than more standard GA 5-8:1 aspects... clearly they work (from delta-wings, which are essentially all strake, to F-18, the SST, etc...). But not sure how they'd work on a Sonerai which already stalls at a higher angle than it assumes in normal landing configuration... but, perhaps one of the old-hands will jump in and explain...
I'm probably missing something... :-\
At least one theory is that they are simply a means of achieving a localized, very-low aspect ratio, which by their nature aren't terribly efficient, but but will hang on at higher angles of attack than more standard GA 5-8:1 aspects... clearly they work (from delta-wings, which are essentially all strake, to F-18, the SST, etc...). But not sure how they'd work on a Sonerai which already stalls at a higher angle than it assumes in normal landing configuration... but, perhaps one of the old-hands will jump in and explain...
I'm probably missing something... :-\
Welcome, Wendell.
From everything I've read on the subject of lower stall speeds in small aircraft, it appears that weight reductions are the first choice. Completely different airfoils can lower stall somewhat, but you'll likely pay for that in cruise speeds, fuel efficiency, and build complications. The Sonerai was not designed for very low stall speeds, but more for efficiency and decent cruise speeds. No matter which aircraft you choose, it will be a compromise.
FWIW, it seems like most who significantly modify any aircraft enter a long term status of "Experimental, Not Flying Yet". Many never finish.
Tom
From everything I've read on the subject of lower stall speeds in small aircraft, it appears that weight reductions are the first choice. Completely different airfoils can lower stall somewhat, but you'll likely pay for that in cruise speeds, fuel efficiency, and build complications. The Sonerai was not designed for very low stall speeds, but more for efficiency and decent cruise speeds. No matter which aircraft you choose, it will be a compromise.
FWIW, it seems like most who significantly modify any aircraft enter a long term status of "Experimental, Not Flying Yet". Many never finish.
Tom
Wendell111
Member
Thank you for the reply. In researching planes with stall speeds under 50 with a decent cruise speed 135+ I came across Sonerai. I really liked the little plane and found one I liked. Then I discovered the stall was 65+ and was wondering if I could get it under 55 with out loosing any speed with mods.
I had read that rv8 builder Mike Robbins had reduced stall speed by four knots by adding strakes which made me curious
Picture at bottom of : www.romeolima.com/RV8/MikeRobbins.htm
He wrote,
Strakes - Before installing the strakes I did a series of power off stalls flaps up and down. Then installed them the next day and repeated the stall series at the same altitude and about the same temperature. I consistently got a four knot reduction in stall speed. May not seem like much, but it makes a difference. I also found that my full stall landings felt much more comfortable. I can approach at a slower speed and touch down slower. I did have a tail shake in a full stall, and the strakes did reduce it. Didn't affect the top end at all.
I had read that rv8 builder Mike Robbins had reduced stall speed by four knots by adding strakes which made me curious
Picture at bottom of : www.romeolima.com/RV8/MikeRobbins.htm
He wrote,
Strakes - Before installing the strakes I did a series of power off stalls flaps up and down. Then installed them the next day and repeated the stall series at the same altitude and about the same temperature. I consistently got a four knot reduction in stall speed. May not seem like much, but it makes a difference. I also found that my full stall landings felt much more comfortable. I can approach at a slower speed and touch down slower. I did have a tail shake in a full stall, and the strakes did reduce it. Didn't affect the top end at all.Thanks for the article, Wendell. Strakes brought to mind something else, but now I see what you have in mind. It would be interesting to see what effect these would have on a Sonerai. 4 mph is impressive for such a small mod.
Tom
Tom
Wendell111
Member
Tom and Larry, again thanks for your responses. I have spent the morning researching RV8 articles regarding strakes. It appears to me the reduction in stall speeds is unique to a situation that caused higher stall speeds to begin with. However, it would still be very interesting to see the effect of strakes installed on a Sonerai.
Wendell
---------------
"It is what it is and that has to be accepted. This does not mean it cannot be improved upon." unknown experimental aircraft builder
Wendell
---------------
"It is what it is and that has to be accepted. This does not mean it cannot be improved upon." unknown experimental aircraft builder
dcstrng
Well-Known Member
I looked at the piece last night -- very interesting to say the least... terminology-wise, I'd call that more of a mini-slat; however, I think the idea is a certainly intriguing...
Looks like the notion is that it compels the air-stream to stay attached at the wing-root and if you can delay the separation there, clearly it won't progress outboard as quickly either...
I'll have to dig around because know I want to know more...
Looks like the notion is that it compels the air-stream to stay attached at the wing-root and if you can delay the separation there, clearly it won't progress outboard as quickly either...
I'll have to dig around because know I want to know more...
DITTO very interesting and do-able mod!dcstrng said:I looked at the piece last night -- very interesting to say the least... terminology-wise, I'd call that more of a mini-slat; however, I think the idea is a certainly intriguing...
Looks like the notion is that it compels the air-stream to stay attached at the wing-root and if you can delay the separation there, clearly it won't progress outboard as quickly either...
I'll have to dig around because know I want to know more...
mhflyit
Well-Known Member
FWIW - My S2L original flight test logs say 'stalled under 60 mph' - empty weight 556lbs
dcstrng
Well-Known Member
After a few hours follow-up reading digging around on the net, I’m of two minds on the slat issue vis Sonerai … but clearly in some configurations of RV8’s it provided a noticeable advantage. Assuming I’ve read correctly, it appears the slat was originally tested to “cure†an alleged tail-plane vibration/shudder at the stall, presumptively caused by disturbed airflow from the landing-gear/leading-edge intersection at high-angles of attack near/at the stall. The slat appeared to have noticeable benefit in solving that "shudder" mystery for RV8 fliers, and some have documented a side benefit of lowering the stall speed 4-5 mph, which is nothing to sneeze at.
Caveat: I’ve never flown in either a Sonerai or RV8, am not an engineer, DAR, ATP, A&P, CFI or even a very good shade-tree wrench… so take with a liberal dose of salt.
My question arises because I note that (not unlike many manufactures) Van’s did not immediately countenance the vibration as an issue – presumably because the factory RV8s flew with all the fairings in place, where many of the builders apparently were flying without the “complete†landing gear fairings in place – or they simply were not available without additional fabrication -- as occasionally occurs in newly built aircraft… Assuming my synthesis has any merit, then it appears the slat forcibly compelled the airflow to stay attached at the wing root for those where the unfaired landing gear/wing root confluence was disturbing the airstream – where, in the case of the RV8s flying with complete fairings, it was unnecessary because the airflow was not disturbed enough on the “faired†RV8s to create the burbling that created the vibrations pilots were feeling.
Whether and what the advantage a slat might be on a Sonerai, might hinge on whether the slat was actually augmenting the RV8 wing, or was simply allowing it to more closely achieve its theoretical designed capability in the absence of using the complete fairing package…
Since, my Sonerai is (even optimistically) at least 20-30 months from completion; I suggest some brave/inquisitive soul confirm the slat on a Sonerai so I’ll know whether I should include the mounting points on my bird…
Hmmmm… :
Caveat: I’ve never flown in either a Sonerai or RV8, am not an engineer, DAR, ATP, A&P, CFI or even a very good shade-tree wrench… so take with a liberal dose of salt.
My question arises because I note that (not unlike many manufactures) Van’s did not immediately countenance the vibration as an issue – presumably because the factory RV8s flew with all the fairings in place, where many of the builders apparently were flying without the “complete†landing gear fairings in place – or they simply were not available without additional fabrication -- as occasionally occurs in newly built aircraft… Assuming my synthesis has any merit, then it appears the slat forcibly compelled the airflow to stay attached at the wing root for those where the unfaired landing gear/wing root confluence was disturbing the airstream – where, in the case of the RV8s flying with complete fairings, it was unnecessary because the airflow was not disturbed enough on the “faired†RV8s to create the burbling that created the vibrations pilots were feeling.
Whether and what the advantage a slat might be on a Sonerai, might hinge on whether the slat was actually augmenting the RV8 wing, or was simply allowing it to more closely achieve its theoretical designed capability in the absence of using the complete fairing package…
Since, my Sonerai is (even optimistically) at least 20-30 months from completion; I suggest some brave/inquisitive soul confirm the slat on a Sonerai so I’ll know whether I should include the mounting points on my bird…
Hmmmm… :
DavidRoss
Member
The RV8 does have a distinct shudder before stall. If you look back, you can watch the tail shake but it's not a danger -- just an effective stall indicator.
So, the slat may have an affect on the airstream in that way.
It's hard to see how it would reduce stall speed that much tho. I'd have to attribute that to flying different days, different density altitudes, different fuel loads and all the other different things that make our airspeed plus or minus 5mph anyway.
It's like weighing yourself with a gram scale to see if that extra banana made a difference.
So, the slat may have an affect on the airstream in that way.
It's hard to see how it would reduce stall speed that much tho. I'd have to attribute that to flying different days, different density altitudes, different fuel loads and all the other different things that make our airspeed plus or minus 5mph anyway.
It's like weighing yourself with a gram scale to see if that extra banana made a difference.
There you go Larry the foot dragging newbie(his footnote) leaving it for the rest us to do...kidding just kidding. ;D Everyone know that Jesus may return before I finish my Sonerai, but this mod does look like an easy experimenters experiment. At worst if it did not work to any advantage and it was taken off there would only be a few attach point holes to patch. If I ever get off my butt, I mean, the ground I will try it.
-Pete
-Pete
a friend have also strakes mount on his One-Design (DR107).
The reason was, on aerobatic figures over 6 G's he had very strong stick buffeting.
After mount the strakes the buffeting was away.
One of the reason for this buffeting was, some air can flow between the fuselage and the front part of the wing, before the spar and this gives air turbulence to the elevator.
with best regards
Juergen
The reason was, on aerobatic figures over 6 G's he had very strong stick buffeting.
After mount the strakes the buffeting was away.
One of the reason for this buffeting was, some air can flow between the fuselage and the front part of the wing, before the spar and this gives air turbulence to the elevator.
with best regards
Juergen
