VansAirForceForums  
Home > VansAirForceForums

- POSTING RULES
- Donate yearly (please).
- Advertise in here!

- Today's Posts | Insert Pics

  #71  
Old 02-20-2017, 02:21 PM
RV8JD's Avatar
RV8JD RV8JD is offline
 
Join Date: Jan 2005
Posts: 953
Default

Quote:
Originally Posted by airguy View Post
This is the first time I've seen any actual numerical figures given for Vans flutter testing in all the time I've been on this forum. That data is jealously guarded, and for good reason, but it's good to see some actual numerical data rather than "You should be fine."
Based on the 217kt number in the report, it appears that Van's did flight test the RV-7A to approximately Vd. I wonder which rudder (-8 or -9/-7) was installed during the flight test.

Van's stating that they flight tested the airplane to Vd should not need to be a jealously guarded secret. Flight testing to Vd should be done by the designer as a matter of course to validate that there is margin above Vne (Redline). The margin between Vne (Redline) and Vd has a parallel to the margin between Limit Load (+6 gs for the aerobatic RVs, which should not be exceed by the pilot) and the Ultimate Load (+9 gs for the aerobatic RVs). And Van's publicizes that they do a Static Load Test to Ultimate Load for their designs.

But I would certainly take the theoretical flutter speed number contained in the report with a grain of salt, until it is known who did the analysis, how it was done, and what assumptions were made. I'm not even restating the number here for fear that folks will latch on to it and assume it is Gospel.
__________________
Carl N.
Arlington, WA (KAWO)
RV-8, 435 Tach Hours
(Pic 1),(Pic 2)
- Out with the Old, In with the New
(Pic)
RV-8, 1938 Tach Hours (Pic 1),(Pic 2) - Sold

Glasflügel Standard Libelle 201B, N564NS - Sold
Rolladen-Schneider LS1-f, N61MP - No longer owned

Last edited by RV8JD : 02-20-2017 at 02:45 PM.
Reply With Quote
  #72  
Old 02-20-2017, 02:43 PM
airguy's Avatar
airguy airguy is offline
 
Join Date: Oct 2006
Location: Garden City, Tx
Posts: 4,363
Default

Quote:
Originally Posted by RV8JD View Post
Based on the 217kt number in the report, it appears that Van's did flight test the RV-7A to approximately Vd. I wonder which rudder (-8 or -9/-7) was installed during the flight test.
The report said it was done on the 7A Prototype, so it would be the earliest rudder version shipped with the 7/7A kits. I don't have personal knowledge of that, do you know which rudder was on the early kits?
__________________
Greg Niehues - PPSEL, IFR, Repairman Cert.
Garden City, TX VAF 2018 dues paid
N16GN flying! http://websites.expercraft.com/airguy/
Built an off-plan 9A with too much fuel and too much HP. Should drop dead any minute now.
Reply With Quote
  #73  
Old 02-20-2017, 03:36 PM
RV8JD's Avatar
RV8JD RV8JD is offline
 
Join Date: Jan 2005
Posts: 953
Default Wow, 6288 Views ...

... in just 7 days! We should charge admission.

(For me, that's what happens when the WX is too crummy to fly!)
__________________
Carl N.
Arlington, WA (KAWO)
RV-8, 435 Tach Hours
(Pic 1),(Pic 2)
- Out with the Old, In with the New
(Pic)
RV-8, 1938 Tach Hours (Pic 1),(Pic 2) - Sold

Glasflügel Standard Libelle 201B, N564NS - Sold
Rolladen-Schneider LS1-f, N61MP - No longer owned

Last edited by RV8JD : 02-20-2017 at 03:40 PM.
Reply With Quote
  #74  
Old 02-20-2017, 03:39 PM
Robert Anglin Robert Anglin is offline
 
Join Date: Mar 2008
Location: houston, texas
Posts: 900
Default Carl and Greg.

It has been a long time now and we did not fallow the 7 as close as we did the 8, so you would have to check with Van's for a good answer. Best I can remember the 7 had the 8 tail to begin with. It was when they got to spin recovery that they did not quite like the recovery and wanted to get a little better response. So the 9 ruder was put on and the fallowing testing show a better result. I think that is how we got the bigger surface area ruder to be implemented for the 7. I really don't know for sure, but they had a contract test pilot doing the testing at the time if I remember correctly so there may be test results from that refit and I just don't know about it. I most often find that Van's try's to get to certified standards with their prototype testing so they have a record of it on the books. You mite E-mail Scott Ryson and ask.
Yours, R.E.A. III #80888
Reply With Quote
  #75  
Old 02-20-2017, 03:45 PM
RV8JD's Avatar
RV8JD RV8JD is offline
 
Join Date: Jan 2005
Posts: 953
Default

I feel sure "rvbuilder2002" (Scott M.) is following this thread and was hoping he might add some facts to the discussion. But I understand that he might feel he would be getting into a hornet's nest, and given the accidents that have occurred, may not want to comment for legal reasons.

Edit addition:

Van's did a great job in explaining what landing gear drop testing was done and which regulations they designed to for the RV-14/14A in this video:

https://youtu.be/KbFMogBNUa0

And for some models they have described what was done regarding Static Load Testing of the wings. I'd love to see a similar description regarding flutter, i.e., describe analyses done, describe testing done (i.e., GVT, FFT), and what regulations or margins were designed to.
__________________
Carl N.
Arlington, WA (KAWO)
RV-8, 435 Tach Hours
(Pic 1),(Pic 2)
- Out with the Old, In with the New
(Pic)
RV-8, 1938 Tach Hours (Pic 1),(Pic 2) - Sold

Glasflügel Standard Libelle 201B, N564NS - Sold
Rolladen-Schneider LS1-f, N61MP - No longer owned

Last edited by RV8JD : 02-20-2017 at 04:01 PM.
Reply With Quote
  #76  
Old 02-20-2017, 07:04 PM
rvbuilder2002 rvbuilder2002 is offline
 
Join Date: Jul 2005
Location: Hubbard Oregon
Posts: 7,873
Default

Quote:
Originally Posted by RV8JD View Post
I feel sure "rvbuilder2002" (Scott M.) is following this thread and was hoping he might add some facts to the discussion. But I understand that he might feel he would be getting into a hornet's nest, and given the accidents that have occurred, may not want to comment for legal reasons.
And you might be right......

I will say that it is incorrect to assume that all testing (old rudder, new rudder, or otherwise....) done by Van's was only done with N137RV.
__________________
Any opinions expressed in this message are my own and not necessarily those of my employer.

Scott McDaniels
Hubbard, Oregon
RV-6A (aka "Junkyard Special ")
Reply With Quote
  #77  
Old 02-20-2017, 10:09 PM
RV8JD's Avatar
RV8JD RV8JD is offline
 
Join Date: Jan 2005
Posts: 953
Default

Quote:
Originally Posted by Vac View Post
Service Bulliten 02-6-1 (8 June 2002) addresses the RV-7 rudder evolution: https://www.vansaircraft.com/pdf/sb02-6-1.pdf
Thanks for this link. It verifies (for me) that the current -7 rudder is identical to the -9 rudder.
__________________
Carl N.
Arlington, WA (KAWO)
RV-8, 435 Tach Hours
(Pic 1),(Pic 2)
- Out with the Old, In with the New
(Pic)
RV-8, 1938 Tach Hours (Pic 1),(Pic 2) - Sold

Glasflügel Standard Libelle 201B, N564NS - Sold
Rolladen-Schneider LS1-f, N61MP - No longer owned

Last edited by RV8JD : 02-20-2017 at 10:15 PM.
Reply With Quote
  #78  
Old 02-21-2017, 08:07 AM
Mudfly Mudfly is offline
 
Join Date: Dec 2011
Location: Alpharetta, Ga
Posts: 152
Default

Quote:
Originally Posted by RV8JD View Post
Thanks for this link. It verifies (for me) that the current -7 rudder is identical to the -9 rudder.
Quote:
Which I believe I remember reading somewhere is also the same as the 14 rudder.
UPDATE:Correction..It was brought to my attention the -14 and -9 rudders are not the same. Sorry. My Mistake. I read that from one of the -14 builders blogs and did not have correct information.

BTW RV8JD, and others, thanks for all the info in this thread. While I'm completely satisfied and comfortable with Vans designs (when operated within their limits), it's nice to hear some of the "behind the scene" physics that make up these limitations. Like most probably, I've been flying airplanes for many years, but didn't know some of this information. Very interesting.
__________________
Shawn Edwards
RV-14A (140174)
www.myrv14build.blogspot.com

Last edited by Mudfly : 02-21-2017 at 12:53 PM.
Reply With Quote
  #79  
Old 02-21-2017, 08:46 AM
BillL BillL is offline
 
Join Date: Sep 2007
Location: Central IL
Posts: 4,553
Default

Quote:
Originally Posted by Mudfly View Post
Which I believe I remember reading somewhere is also the same as the 14 rudder.

BTW RV8JD, and others, thanks for all the info in this thread. While I'm completely satisfied and comfortable with Vans designs (when operated within their limits), it's nice to hear some of the "behind the scene" physics that make up these limitations. Like most probably, I've been flying airplanes for many years, but didn't know some of this information. Very interesting.
Absolutely not. Your 14 rudder has the stiffeners attached to each other like ribs. The 6-8-9 rudders have free floating stiffeners. Look close at the post above to see that.

"Jackie Stewart and Graham Hill would walk through the paddock after the F1 races and the drivers (who lost) would say - if I had one more lap, if i had 3 more liters of fuel I would have won, I am the best . J & G, joked sure, and we could have strawberries and cream, if we had some strawberries . . . . . . and some cream. "
__________________
Bill

RV-7
1st Flight 1-27-18
Phase II 8-3-18
Repairman 11-15-18

Last edited by BillL : 02-21-2017 at 11:36 AM.
Reply With Quote
  #80  
Old 02-21-2017, 05:32 PM
RV8JD's Avatar
RV8JD RV8JD is offline
 
Join Date: Jan 2005
Posts: 953
Default

Quote:
Originally Posted by Mudfly View Post
UPDATE:Correction..It was brought to my attention the -14 and -9 rudders are not the same. Sorry. My Mistake. I read that from one of the -14 builders blogs and did not have correct information.
My Post #42 shows the difference. Although it shows a drawing of the -8 rudder, as BillL points out, the -9/-7 rudder and -8 rudder have the same stiffener concept, but the skins are different thickness.

Quote:
Originally Posted by Mudfly
BTW RV8JD, and others, thanks for all the info in this thread. While I'm completely satisfied and comfortable with Vans designs (when operated within their limits), it's nice to hear some of the "behind the scene" physics that make up these limitations. Like most probably, I've been flying airplanes for many years, but didn't know some of this information. Very interesting.
Thanks. Appreciate that. Before this thread I was hesitant to address flutter questions. Flutter is fairly complicated (not to mention highly nonlinear and unintuitive) and I didn't have time (I felt) to adequately address the subject. I'm still concerned that some folks may glean just enough information to be dangerous. And that may be worse than not knowing anything about flutter.

You might get a chuckle out of these two slides that I pulled from a pitch I put together awhile back:

A quote from the famous aerodynamicist Theodore von Kármán:


Dix Loesch was one of the experimental test pilots on the "Dash 80" program:


Some people still think flutter is a "Black Science", but it's not! Really! (now structural fatigue, that is VooDoo and Black Magic! )
__________________
Carl N.
Arlington, WA (KAWO)
RV-8, 435 Tach Hours
(Pic 1),(Pic 2)
- Out with the Old, In with the New
(Pic)
RV-8, 1938 Tach Hours (Pic 1),(Pic 2) - Sold

Glasflügel Standard Libelle 201B, N564NS - Sold
Rolladen-Schneider LS1-f, N61MP - No longer owned

Last edited by RV8JD : 02-21-2017 at 07:24 PM.
Reply With Quote
Reply


Thread Tools Search this Thread
Search this Thread:

Advanced Search
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

vB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Forum Jump


All times are GMT -6. The time now is 05:47 PM.


The VAFForums come to you courtesy Delta Romeo, LLC. By viewing and participating in them you agree to build your plane using standardized methods and practices and to fly it safely and in accordance with the laws governing the country you are located in.