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  #31  
Old 01-26-2018, 08:53 AM
rocketman1988 rocketman1988 is offline
 
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Default tanks

I thought the ER tank installation was pretty straight forward. Everything fit as it was supposed to, and as far as mods go, it was pretty painless.

I am pretty sure that the time involved with installing the ER tanks would be much less than fabricating tanks from the wingtips. Don't forget to account for the dynamic loads imposed on the wingtip attachment due to 5-6 gallons of fuel moving around in them...
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  #32  
Old 01-26-2018, 01:06 PM
Bill Boyd's Avatar
Bill Boyd Bill Boyd is offline
 
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Default Yes.

I'm pondering that right now as I finish epoxying and riveting the attachment piano hinges.

I can always do a chin-up on the wingtip to test a static load equivalent to 30 # of fuel at 6G, but dynamic loads are a different matter. How fast do I jump up and down on the wingtip to test that? Furthermore, what's the consequence of an in-flight failure of a wingtip/integral tank if the hinge unzips under load? Likely the jetsam would clear the empennage, but would the aileron be compromised? Would the lateral imbalance be uncontrollable? Doubtful in either case, but not possible to spitball with complete confidence.

I do know that with reasonable care I could pull this off for far less than 3 AMU and gain an extra 10 gallons. Time and frustration are another matter.
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  #33  
Old 01-26-2018, 01:16 PM
rv7charlie rv7charlie is offline
 
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Location: Pocahontas MS
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Default

I don't intend to call my -7 a 6 G a/c with fuel in the aux tanks. I'd consider it utility category at best; probably closer to 'normal' category in terms of G load ratings. I bet if you look at the docs for any commercially produced aux tanks, they'll say the same thing.

Just something to think about.
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  #34  
Old 01-26-2018, 01:22 PM
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Bill Boyd Bill Boyd is offline
 
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Default You raise a good point.

As usual

I am accustomed to having that 6G figure (9G ultimate) in my head from 20 years of RV-6A ownership. The 10 is not considered aerobatic, and likely rated for lesser loadings. But I can't find that on the Van's website, and I just looked. What's the most G the airframe of the -10 is intended to handle in turbulence and maneuvering?
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RV-6A - N30YD - flying since '98
RV-10 - N130YD reserved - under construction

donating monthly to the VAF - thanks, Doug
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  #35  
Old 01-26-2018, 01:29 PM
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Mel Mel is online now
 
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Location: Dallas area
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Default

Quote:
Originally Posted by Bill Boyd View Post
As usual
What's the most G the airframe of the -10 is intended to handle in turbulence and maneuvering?
This from Van's website: "The design operational stress limit for the RV-10 is standard category (+3.8/-1.5 G)".
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  #36  
Old 01-26-2018, 02:23 PM
rvbuilder2002 rvbuilder2002 is offline
 
Join Date: Jul 2005
Location: Hubbard Oregon
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Default

Quote:
Originally Posted by Bill Boyd View Post
As usual

I am accustomed to having that 6G figure (9G ultimate) in my head from 20 years of RV-6A ownership. The 10 is not considered aerobatic, and likely rated for lesser loadings. But I can't find that on the Van's website, and I just looked. What's the most G the airframe of the -10 is intended to handle in turbulence and maneuvering?
And to add clarity for those that may not know......

The RV-6A (and all of the other RV models approved for aerobatics for that matter) is approved for 6 G's at a specified aerobatic weight that is lower than the approved max. gross weight.
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  #37  
Old 01-26-2018, 02:40 PM
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Bill Boyd Bill Boyd is offline
 
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Default

So I guess that means 3.8G operational and 1.5 * 3.8 = 5.7G ultimate? Pretty close to 6G, there.

The other load-determining factor is the all-up weight of the fully-built-out wingtip, with fuel in tank.

I think my first step beyond asking here is to temporarily baffle the tip, line with a trash bag, and see how many gallons of water the shape holds. Work calculations from there.
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Hop-Along Aerodrome (12VA)
RV-6A - N30YD - flying since '98
RV-10 - N130YD reserved - under construction

donating monthly to the VAF - thanks, Doug

Last edited by Bill Boyd : 01-26-2018 at 02:43 PM.
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  #38  
Old 01-26-2018, 02:52 PM
rv7charlie rv7charlie is offline
 
Join Date: May 2006
Location: Pocahontas MS
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Default

Hi Scott,

Since you brought it up...

It really would be good if kit makers (including Van's) would include the category in their spec sheets. I can just about guarantee that there are owners (even builder-owners) out there that don't realize the acro-capable models have lower gross weight ratings for acro.

All it would take is an extra few keystrokes to include the info (fantasy numbers...):

"Gross weight: 5000 lbs (normal category)
4000 lbs (utility category)
3000 lbs (aerobatic category)"

Charlie
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  #39  
Old 01-26-2018, 03:11 PM
BobTurner BobTurner is offline
 
Join Date: Dec 2011
Location: Livermore, CA
Posts: 5,355
Default

I'm not trying to talk you out of this, if it's what you want. But I don't think you should use the excuse of IFR operations to do it, as long as you're willing to fly LOP. LOP you have nearly 6 hours to empty. That gives you 4 hours to destination, 1 hour to alternate, nearly 1 hour reserve. And, quite honestly, you may well find yourself second guessing things, if an alternate is needed and the nearest one is an hour away. So the tanks really are for if you often want to do a trip that's more like 5 hours away - assuming your bladder capacity is at least 6 hours (if you need to go to the alternate). OR, if you want to run 75% power ROP at 14 gal/hr. Then, the tanks look attractive.
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  #40  
Old 01-26-2018, 03:11 PM
rv7charlie rv7charlie is offline
 
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Location: Pocahontas MS
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Default

Bill,

The 1.5 multiplier is for *ultimate* load (that means permanent distortion/failure).
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