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11-26-2012, 05:03 PM
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Join Date: Sep 2009
Location: St. Louis, MO
Posts: 1,788
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Bryan,
I am a home and don't have access to the documents, but as I recall, the speeds are in the documents that come with the final kit
Bill
__________________
Bill Peyton
RV-10 - 1125 hrs
N37CP
First Flight Oct 2012
Aviation Partners, LLC
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11-26-2012, 06:22 PM
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Join Date: Jul 2005
Location: Detroit, MI
Posts: 1,587
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L/D Max vs. Best Glide V vs. Engine-out V
Quote:
Originally Posted by RV10inOz
Has anyone really worked out the best L/D for an RV10? assume 2700lbs.
Just never seen it anywhere on the forum......... 
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I must sound like a stuck needle on a 33 RPM record. First of all, L/D is a ratio, not a speed. The L/D max for a given wing (and usually a given airplane) does not change with weight. The speed at which it is obtained is higher with greater weight. With a few easily obtained facts and one reasonable estimate, both can be approximated with my "triangle" spreadsheet - the latest version. If any -10 owner would like to work with me on that I would be delighted to provide the "answers" on this forum.
A L/D max of <10 for a "10" is significantly low of reasonable since a -6 has a ratio >12. See the CAFE report if you doubt this.
The L/D max and the V for it are useful in planning a flight profile but they are pretty much useless when the noise stops. If there is any thrust, then they apply. That goes for approach speeds except perhaps with the throttle totally closed.
The best glide ratio and the best glide speed with a prop (stuck or windmilling) out front are both lower than without a prop. See the Norris-Bauer experiments in 1995.
The glide ratio and best speed with engine out must be determined experimentally and if the prop is CS then the no-power prop pitch must be simulated. Duh.
I can't comment on the discussion of flap settings. Sorry.
For much more about this, please refer to my website and drill down to the Oshkosh presentations, especially the most recent. On the same page you will find links to the references above, too.
__________________
H. Evan's RV-7A N17HH 240+ hours
"We can lift ourselves out of ignorance, we can find ourselves as creatures of excellence and intelligence and skill. We can be free! We can learn to fly!" -J.L. Seagull
Paid $25.00 "dues" net of PayPal cost for 2015, 2016, 2017 and 2018 (December).
This airplane is for sale: see website. my website
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11-26-2012, 09:41 PM
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Join Date: Sep 2006
Location: Douglas Flat, CA
Posts: 589
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Quote:
Originally Posted by hevansrv7a
...A L/D max of <10 for a "10" is significantly low of reasonable since a -6 has a ratio >12. See the CAFE report if you doubt this...
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Color me skeptical, but given the RV6's much lower aspect ratio I have to accept that assertion only with an apples-to-apples data set. Or a big grain of salt.
__________________
Bob Kuykendall
HP-24 kit sailplane
EAA Technical Counselor
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11-26-2012, 10:10 PM
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Join Date: Jul 2005
Location: Detroit, MI
Posts: 1,587
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which assertion?
Quote:
Originally Posted by Bob Kuykendall
Color me skeptical, but given the RV6's much lower aspect ratio I have to accept that assertion only with an apples-to-apples data set. Or a big grain of salt.
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Bob, if you are questioning the CAFE data I suggest you review it first. If you are skeptical of the 6A result because you accept the <10 for the 10 as correct then I ask that you review the part of my post where I note that the presence of a prop that provides drag alters the result significantly.
I also suggest you review the other CAFE tests that used the Norris-Bauer device. Not all did. The Thorp T-18 did. All the ones that did are listed on my site.
For example, the C-152 without a prop can be compared to the C-152 POH. There is a huge difference. I provide the actual numbers on my website.
The Norris-Bauer zero thrust method, which CAFE used for the 6A, is a proven way to correctly simulate the absence of the prop.
Lastly, I suggest this test: use the 9.6 L/D and the speed at which it was obtained and the weight of the airplane. Compute the sink rate and use the sink rate times the weight divided by the HP value to get the true thrust HP at that speed. Convert that to drag. Now, since parasite and induced drag must be equal at the speed where L/D is max, then project the two drag curves and compute the THP needed to get to the airplane's known top speed. Be sure to keep CAS and TAS straight. Use some reasonable estimate of prop net efficiency (85%? 90%?) and thus compute BHP. You will find that the BHP needed to match the airplane's known performance is greater than what is actually available.
However, if you use CAFE's values you will find a reasonable result.
If this sounds like a lot of difficult math, just use my triangle spreadsheet and it will be very easy. PM or email me if you want to go over this in more detail.
__________________
H. Evan's RV-7A N17HH 240+ hours
"We can lift ourselves out of ignorance, we can find ourselves as creatures of excellence and intelligence and skill. We can be free! We can learn to fly!" -J.L. Seagull
Paid $25.00 "dues" net of PayPal cost for 2015, 2016, 2017 and 2018 (December).
This airplane is for sale: see website. my website
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11-27-2012, 03:10 AM
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Join Date: Oct 2009
Location: Uberaba, MG, Brazil
Posts: 122
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Now what should ailerons be aligned with, 0 or -3?
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11-27-2012, 06:42 AM
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Join Date: Jan 2006
Location: New Smyrna Beach, FL
Posts: 1,339
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Follow Van's instructions carefully and everything will be aligned as required. Flaps full up (against the spar) and then ailerons and wingtips are aligned with the flaps. Don't worry about reflex.
__________________
David Maib
RV-10 N380DM
New Smyrna Beach, FL
VAF Paid 1/21/2020
"In '69 I was 21, and I called the road my own"
Jackson Browne
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11-27-2012, 08:31 AM
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Join Date: Jul 2005
Location: Detroit, MI
Posts: 1,587
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A flight testing issue
I just did a quick look at Mike Andresen's flight testing that produced the L/D numbers at the start of this thread. If I understand it correctly, he used engine power as given by the EFIS to compute HP and convert it to drag.
The good news is that he is using a method that eliminates prop DRAG. The bad news is that I don't see any correction for prop efficiency. A typical prop will give a max of 85%, often less. If you take 9.6 and divide it by 0.85 you get about 11.3. That is a much more reasonable result. If prop efficiency at those low speeds is 80% then the corrected number would be 12.0.
I think it should be greater than 12, maybe even 12.5, but I will test it using my spreadsheet and report back on this thread later.
I also noticed that he has a link to my stuff. Thanks, Mike!
BTW - Mike does a very nice job of collecting, organizing and presenting data. I only wish I could do as well. I think that I can use his data in my triangle spreadsheet (plus published dimensions for the -10).
__________________
H. Evan's RV-7A N17HH 240+ hours
"We can lift ourselves out of ignorance, we can find ourselves as creatures of excellence and intelligence and skill. We can be free! We can learn to fly!" -J.L. Seagull
Paid $25.00 "dues" net of PayPal cost for 2015, 2016, 2017 and 2018 (December).
This airplane is for sale: see website. my website
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