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  #21  
Old 11-18-2014, 08:09 AM
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Kevin Horton Kevin Horton is offline
 
Join Date: Jan 2005
Location: Green Bay, WI, USA
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Quote:
Originally Posted by Jrskygod View Post
RVbuilder if the 9 was extensively spin tested why are we plackarding them for no spins
Van's likely used the FAR 23.221 spin requirements as guidance. FAR 23 (applicable to type-certificated light aircraft) requires that every single engine aircraft be able to recover from a one turn spin, even if the aircraft is not approved for intentional spins. The spin is not fully developed after one turn, so it is more of a test of recovery from incipient spins. If the aircraft is to be approved for intentional spins, you also need to show that it can be recovered from six turn spins.

Note: the above is a rough summary of FAR 23.221 spin requirements, and does not cover all the details, including a "let" for aircraft that are shown to be spin resistant.
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  #22  
Old 11-18-2014, 08:48 AM
rockwoodrv9 rockwoodrv9 is offline
 
Join Date: Dec 2011
Location: Meridian ID, Aspen CO, Okemos MI
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Quote:
Originally Posted by Jrskygod View Post
RVbuilder if the 9 was extensively spin tested why are we plackarding them for no spins
That is what I thought. I would still like to know what the spin testing issues were. I don't want this thread to get off track, so if there is other info about spin testing for the 9, pm or email me. Thanks
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  #23  
Old 11-18-2014, 08:57 AM
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rvbuilder2002 rvbuilder2002 is offline
 
Join Date: Jul 2005
Location: Hubbard Oregon
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Quote:
Originally Posted by rockwoodrv9 View Post
That is what I thought. I would still like to know what the spin testing issues were. I don't want this thread to get off track, so if there is other info about spin testing for the 9, pm or email me. Thanks
The official company position is that there were no "spin Issues" (not sure why someone thinks they must be "placarded" against spins). Recreational spins are not recommended. This is not particular to the RV-9. It is the same recommendation for all the side by side RV's. It has nothing to do with ability to recover, or unusual techniques needed. It is because the aggressive entry break and subsequent acceleration towards a high rate of rotation will like scare the %&@#* out of most pilots if that let it go very far.
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Van's Aircraft Engineering Prototype Shop
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  #24  
Old 11-18-2014, 10:18 AM
Sig600 Sig600 is offline
 
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The purpose of winglets (usually on high performance aircraft) is to increase low speed lift, reducing spanwise flow, and reduce drag by reducing wingtip vortices at cruise.

None of these are aerodynamic issues on an RV except MAYBE wingtip vortices drag, but even reducing that to zero would be such a small reduction in total drag you wouldn't notice a difference in day to day flying.

Other than the tip tanks for someone who can sit in an RV for 4+ hour stretches... this is a solution looking for a problem.
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  #25  
Old 11-18-2014, 10:33 AM
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Buggsy2 Buggsy2 is offline
 
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Quote:
Originally Posted by anandaleon View Post
Correction: 14 gallons on each tank = 28 gallons total
Wow, 28 additional gallons...just curious, why so much? I would think 5-8 gallons each tip, for a total of 10-16 additional gallons, would give a very good total range or endurance.
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  #26  
Old 11-18-2014, 11:10 AM
designerX designerX is offline
 
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64 gallons without resorting to a fuselage/baggage tank?! That is impressive. I too am very curious of your motivation.. just for kicks? cross continent ferry service? looking to exceed Jon Johannson's records? inquiring (nosey) minds want to know .

They look great.. congratulations! Have fun experimenting.

Stan
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  #27  
Old 11-18-2014, 11:29 AM
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rv9av8tr rv9av8tr is offline
 
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Location: Portland, OR
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Default RV9 Extra fuel

I have to say putting fuel so far outboard raises significant structual concerns for me. While I don't object to experimenting, I just wouldn't do this particular mod without significant analytical backup.

I too wanted more fuel for my -9A as I wanted to have the same range capability as my Long-EZ had. I decided to keep the fuel weight inside the airplane by building fiberglass tanks that tucked into the space behind the seats. The CG isn't much further aft than the pilot/pass CG. Each tank holds 8 gal, which I've found to only need one tank for the vast majority of my Xcountrys.
I burn this Aux tank off first during the initial climb out when fuel consumption is highest and by the end of the first 45 min or so the tank is empty. It gives me a range of a 1000 miles with reserves.

The tank is directly plumbed into the 3rd fuel port on the standard fuel selector valve. I've regularly used this setup and it works GREAT!
https://picasaweb.google.com/1166542...15801258893730
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  #28  
Old 11-18-2014, 01:00 PM
rockwoodrv9 rockwoodrv9 is offline
 
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Thank you Scott for the answer. The placard comment is what confused me a bit. Thanks again, I appreciate it.

Quote:
Originally Posted by rvbuilder2002 View Post
The official company position is that there were no "spin Issues" (not sure why someone thinks they must be "placarded" against spins). Recreational spins are not recommended. This is not particular to the RV-9. It is the same recommendation for all the side by side RV's. It has nothing to do with ability to recover, or unusual techniques needed. It is because the aggressive entry break and subsequent acceleration towards a high rate of rotation will like scare the %&@#* out of most pilots if that let it go very far.
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  #29  
Old 11-18-2014, 01:28 PM
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Greg Arehart Greg Arehart is offline
 
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Location: Delta, CO/Atlin, BC
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Quote:
Originally Posted by designerX View Post
64 gallons without resorting to a fuselage/baggage tank?! That is impressive. I too am very curious of your motivation.. just for kicks? cross continent ferry service? looking to exceed Jon Johannson's records? inquiring (nosey) minds want to know .

They look great.. congratulations! Have fun experimenting.

Stan
Anyone flying north to Alaska or other similar destinations can use the extra fuel. 99% of the time, having extra fuel is not an issue but, for example, flying the Trench route through BC, from Mackenzie to Watson Lake if you get into weather at the northern end of that leg and have to turn around, it may not be possible to get back to Mackenzie on a "normal" tank of fuel. There are places to land, but no fuel.

Or take Vlad's proposed adventure to the Aleutians and back - another example of a long flight for which it would be very useful to have extra fuel.

Just a couple examples of "why" someone might want to do this.

Greg
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  #30  
Old 11-18-2014, 02:24 PM
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N200PF N200PF is offline
 
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Guys I'm all for experimenting...and I fly a 180hp -4 so the idea of having a bit of extra fuel is certainly appealing to me. However, 14 gallons per side puts a picture in my head.

Imagine sitting on the ramp at an air show and seeing two 84 pound kids jumping up and down on your wingtips using your wings like spring boards...at the same time! That's essentially the force your wing structure and spare would need to endure on a rough landing. Would you worry about your airframe structure if you saw this happen at an air show? I would.

I also can't imagine putting two, yes two, 40 pound bags of concrete in EACH of my wing tips and taking off.

Again, I'm not an engineer so excuse the non-technical perspective but it has served me well thus far in my flying career. Sorry to be a downer on this...I love that we can experiment but this one makes me uncomfortable.
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