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07-29-2012, 10:40 AM
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Join Date: Mar 2012
Location: Alpharetta, GA
Posts: 52
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Quote:
Originally Posted by Mel
So, the stall speed stays the same regardless of weight?
Interesting. At light weight the stall speed of the -14 is 5 mph higher than the -7, but at gross weight it is 2 mph lower.
How they do that?
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Yes...remember that a stall occurs when the critical angle of attack is exceeded, not related to weight. My guess is that the wing profile causes your observation, but I'm not an aerodynamicist and I didn't stay at a Holiday Inn Express last night.
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Frazer Middleton
Alpharetta, GA
Paid =VAF= dues for 2013
Friend of the RV-1 http://www.rv-1.org
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07-29-2012, 10:42 AM
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Join Date: Aug 2009
Location: Southern California
Posts: 882
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Quote:
Originally Posted by Mel
So, the stall speed stays the same regardless of weight?
Interesting. At light weight the stall speed of the -14 is 5 mph higher than the -7, but at gross weight it is 2 mph lower.
How they do that?
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Don't know, but I suspect one of the figures is in error. Nevertheless, these are the numbers that Van's has published in their brochure so they should be included in the comparison.
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07-29-2012, 10:47 AM
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Join Date: Aug 2009
Location: Southern California
Posts: 882
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Quote:
Originally Posted by fmiddleton
Yes...remember that a stall occurs when the critical angle of attack is exceeded, not related to weight. My guess is that the wing profile causes your observation, but I'm not an aerodynamicist and I didn't stay at a Holiday Inn Express last night.
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Yes but increased weight typically requires more angle of attack at a given airspeed to produce the required lift...hence critical angle of attack should be reached at higher airspeed when at gross vs light loading. Also, this is supposed to be the same wing section as the -10 which has different gross and light load stall speeds. The -14 does have a lower gross weight wing loading than the -10.
Skylor
Last edited by skylor : 07-29-2012 at 11:01 AM.
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07-29-2012, 11:03 AM
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Join Date: Mar 2012
Location: Alpharetta, GA
Posts: 52
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Quote:
Originally Posted by skylor
Yes but increased weight typically requires more angle of attack at a given airspeed to produce the required lift...hence critical angle of attack should be reached at higher airspeed when at gross vs light loading. Also, this is supposed the be the same wing section as the -10 which has different gross and light load stall speeds. The -14 does have a lower gross weight wing loading than the -10.
Skylor
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I think that works though...in this case weight is relevant with the same wing profile. Lift = Speed * Angle of Attack. Lift has to counteract the weight of the plane, and they stall at the same AoA, therefore the speed will be different. I guess this also just disproved my original assertion about weight...however, the stall AoA on the -7 and -14 is likely different.
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Frazer Middleton
Alpharetta, GA
Paid =VAF= dues for 2013
Friend of the RV-1 http://www.rv-1.org
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07-29-2012, 12:46 PM
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Join Date: Aug 2009
Location: Southern California
Posts: 882
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Quote:
Originally Posted by fmiddleton
...however, the stall AoA on the -7 and -14 is likely different.
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Agreed...different airfoils, different critical AOA...but the stall AOA should be the same for the 10 and 14, at different speeds though.
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07-29-2012, 07:07 PM
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Join Date: Oct 2010
Location: Elkton, Md.
Posts: 1,652
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I am pretty sure one of the Van's staff said that a IO360 could be substituted for the IO390.
__________________
Wag Aero Sport Trainer built,sold and wrecked
N588DF RV12 #336 built, sold and alive and well in New York
N73DF RV12 #244 built, sold and alive and well in Florida
N91 RV RV9 I wish I could say I built this one! Mark Santoleri hit the ball out of the park on this gem.
Currently restoring a 1978 Citabria GCBC
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07-29-2012, 10:19 PM
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Join Date: Nov 2005
Location: KRTS
Posts: 1,798
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It didn't look like it from the "walk around" video, but does anyone know if the -14 uses a reflexed flap position like the -10 in cruise?
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Next?, TBD
IAR-823, SOLD
RV-8, SOLD
RV-7, SOLD
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07-30-2012, 05:16 AM
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Join Date: Aug 2008
Location: 70'N ENNA Norway
Posts: 14
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VNE ????
Anyone know the VNE???
Would be perfect with the IO408 for mogas, 218 HP 
OlaM
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07-30-2012, 06:37 AM
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Join Date: Aug 2005
Location: Dallas/Ft Worth, TX
Posts: 5,686
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Quote:
Originally Posted by Sig600
It didn't look like it from the "walk around" video, but does anyone know if the -14 uses a reflexed flap position like the -10 in cruise?
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According to rep, yes.
__________________
Walt Aronow, DFW, TX (52F)
EXP Aircraft Services LLC
Specializing in RV Condition Inspections, Maintenance, Avionics Upgrades
Dynamic Prop Balancing, Pitot-Static Altmeter/Transponder Certification
FAA Certified Repair Station, AP/IA/FCC GROL, EAA Technical Counselor
Authorized Garmin G3X Dealer/Installer
RV7A built 2004, 1700+ hrs, New Titan IO-370, Bendix Mags
Website: ExpAircraft.com, Email: walt@expaircraft.com, Cell: 972-746-5154
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07-30-2012, 02:24 PM
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Join Date: Mar 2012
Location: Wichita Falls, TX
Posts: 315
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Quote:
Originally Posted by rvnor
Anyone know the VNE???
Would be perfect with the IO408 for mogas, 218 HP 
OlaM
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That engine has a 10.5:1 compression ratio and is cleared for 91 UL. How is the 390 not approved for mogas with a 8.7:1?
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