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VNE

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Posted (edited)

Hi! 

Can someone explain me what is the correct VNE for an Avid C basic STOL wing?

I have an old Avid paper stating 90mph, another Avid paper stating 95 and kitfoxes are 100.

Now, assuming my aircraft is really light and i'm really light (around 130 lbs) can i use at least 95 VNE in no turbulent air?

Is an issue cruising at 90 indicated solo in perfect air?

Thanks

Edited by Airwolf

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Posted

What engine do you have? If it's a 582 cruising at 95 isn't really possible. I've been told that the early VNE was due to the fabric only being glued to the rib caps on the under cambered wing and the windshield not collapsing in on your face. Many people with bigger engines are cruising at 100+ with rib stitched wings and upgraded windows. 

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Posted (edited)

Thanks Joey (I follow you on Youtube).

Well i have a 582 blue, around 5900 rpm static and 6100 on takeoff with a 3 blade Woodcomp, and because of my weight i can take off in around 250ft .

My "fast" cruise at 6000rpm before restoration was 88mph IAS, and we have done some little aerodynamic improvements, like fairings of the "internal tubes :D " of the (original) landing gear, prop spinner, fabrics of the gear, removal of all lights and beacons, all metal turtle deck and roof (no sky view on top) and better fairings of the wing struts.

I hope to have the plane ready at the end of this month, and i expect a 3-5mph gain.

I have some pics on my "introduction" topic.

 

Edited by Airwolf

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Posted

With my MK IV and the Jabiru engine, I could do right at 100 MPH on top end.  The .060" windshield would push up against the tubes at times at that speed.  The MK IV has a VNE of 135.  I wouldn't want to try it with that thin windshield.  JImChuk

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Posted

Thanks. Mine is 0.080", but, like C5 said, i think i don't have the problem of exceeding 90-95 with a 582 on normal operating revolutions  :))

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Posted

When I got to fly my mkIV last time in January I was seeing around 116mph indicated and gps was 113mph. No windshield push or anything . I run a 582 with 3 blade warp drive tapered tip. I also have the true speedwing . 

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Posted

what is the difference about early models STOL wing and MK4 STOL wing? (pure undercambered no HH) Rib stitching? 

I see the MK4 STOL have a greater Vne

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Posted (edited)

Based on the sandbag test in the Avid literature, the maneuvering speed Va should be 104 mph.  Why they list something lower as never-exceed speed I don't understand.  That Va I quoted is equivalent airspeed, or EAS.  Errors in the static pressure measurement could easily cause your ASI to read high or low, though.  Change AOA, open or close your vents?  All act to bugger the cabin pressure, which is used as the static pressure.  I'm tempted to build a static cone or other device to try to get a decent static pressure measurement then calibrate the ASI.  The total, or ram pressure is relatively easy to measure accurately.  The static is difficult to get right.

Edited by Turbo

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Posted

Based on the sandbag test in the Avid literature, the maneuvering speed Va should be 104 mph.  Why they list something lower as never-exceed speed I don't understand.  That Va I quoted is equivalent airspeed, or EAS.  Errors in the static pressure measurement could easily cause your ASI to read high or low, though.  Change AOA, open or close your vents?  All act to bugger the cabin pressure, which is used as the static pressure.  I'm tempted to build a static cone or other device to try to get a decent static pressure measurement then calibrate the ASI.  The total, or ram pressure is relatively easy to measure accurately.  The static is difficult to get right.

fabric separation from the ribs without stitching was a major driver in the lower VNE.  I stitched mine and on long descents I have busted the VNE pretty good.  Controls get pretty tight and its not a really great feeling.  Overall the plane is much happier keeping it under 100.

:BC:

 

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Posted (edited)

It's more fun just putting around the sky anyways, unless you're actually trying to get somewhere.  You Alaska flyers amaze me.  I must still be a little shy of trusting the 582 like you guys do.  Hey, I'm still trying to nail down my landings.

BTW, it's easy to go fast when you're descending.  

Edited by Turbo

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