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Doug.Zeissner(at)rdmd.ocg
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Posted: Thu Mar 20, 2008 1:14 pm Post subject: More fuel

I have been considering extra fuel capacity. What have been the positive / negative experiences with fuel tank   

modifications such as welding a section to an existing tank- replacing the tank with a bladder – or adding a separate  

Aux tank?  I am looking to get +/- 12 gallons more capacity in my CJ.   

   

[b]Doug Zeissner[/b]  

email: doug.zeissner(at)rdmd.ocgov.com  

   

      [quote][b]

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ChangDriver

Joined: 15 Sep 2007
Posts: 266

Posted: Fri Mar 21, 2008 5:39 pm Post subject: Re: More fuel

Doug:



The Air Victoria mod (well known) requires some wing rib mods and adds the extra capacity you are looking for.



Fuel bladders can get you to 60 gallons.  They are bladders and will need maintenance and replacement somewhere down the road.  Some installations for bladders also includes fuel tank vent shut-offs so you can more evenly burn fuel on XC flights.



Barry Hancock at Worldwide Warbirds has developed a set of hard tanks that will get you 60 gallons total (well, it may be 59.5 but close enough).  The first set is being fabricated right now for installation in my CJ.  It requires less wing mods that the Air Victoria mod and does not have the issues with bladders.  



The tanks will be welded next week and ready for install right after that.  You can contact Barry at 909-606-4444 for more info.



Craig

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dougsappllc(at)gmail.com
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Posted: Sat Mar 22, 2008 6:54 am Post subject: More fuel

Craig,

 Available aux fuel systems:

  

 My welded tanks give 16.5 gallons per side additional, but on a "per gallon" basis are the most expensive to install, but you do end up with all new beefed up .032 skins aft of the main spar top and bottom (stock skins are about .027).  If you want to install bladders AND my tanks you can push 97 gallons!  With Barry's you could have over 100 gallons USEABLE on board, Hello "Tanker 1"!

   

 Vic Air give just a few gallons additional each side, but cut ribs to get it, and for the cost and trouble really is not worth the small amount of fuel gained.

  

 Bladders give 12 gallons additional each side, but all fuel rests on the lower tank skins, which I am really not crazy about although Blackewll says they have done the math.

  

 I have owned/flown aircraft with all the above and the all have +'s and minuses.  I had the bladders and the managed vent system in my factory new CJ6A and flew lots of 3:45 legs, but the "managed" vent system had issues.  Hopefully Barrys tanks will have better strapping to hold the tanks in the fuel bay during high G loading than the bladders.  

   

 From a marketing standpoint,  what sells tanks is really not the gallons gained, but the dollars per gallon all up finished cost.  

  

  

 



 

 On Fri, Mar 21, 2008 at 6:39 PM, Craig Winkelmann, CFI <capav8r(at)gmail.com (capav8r(at)gmail.com)> wrote:

 [quote]--> Yak-List message posted by: "Craig Winkelmann, CFI" <capav8r(at)gmail.com (capav8r(at)gmail.com)>

 

Doug:



The Air Victoria mod (well known) requires some wing rib mods and adds the extra capacity you are looking for.



Fuel bladders can get you to 60 gallons.  They are bladders and will need maintenance and replacement somewhere down the road.  Some installations for bladders also includes fuel tank vent shut-offs so you can more evenly burn fuel on XC flights.

 

Barry Hancock at Worldwide Warbirds has developed a set of hard tanks that will get you 60 gallons total (well, it may be 59.5 but close enough).  The first set is being fabricated right now for installation in my CJ.  It requires less wing mods that the Air Victoria mod and does not have the issues with bladders.

 

The tanks will be welded next week and ready for install right after that.  You can contact Barry at 909-606-4444 for more info.



Craig





Read this topic online here:



http://forums.matronics.com/viewtopic.php?p=171630#171630

 

-- 

Always Yakin,

Doug Sapp

Phone 509-826-4610

Fax 509-826-3644   [quote][b]

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wlannon(at)persona.ca
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Posted: Sat Mar 22, 2008 9:05 am Post subject: More fuel

[quote] ---

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wlannon(at)persona.ca
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Posted: Sun Mar 23, 2008 2:21 pm Post subject: More fuel

I thought my comments (at the bottom of Doug's  message below) on the modifications to increase CJ6 fuel capacity would generate  some interest and further comment. Apparently not. 

 Brian; where are you?

  

 So, since I believe this subject is of paramount  importance to the continued operation of the CJ, I will try again. My  comments refer to the bladder modification but really apply to all fuel  increase mods. that increase the applied loads and/or change the design load  paths.

  

 The existing fuel loads are transmitted  directly to the front and rear spars through the tank, the support straps  and upper surface inter-spar structure.  A very well proven and traditional  method of supporting metal tanks. 

 The tank access panel is just that, a means of  access. It carries none of the fuel load and is designed only to carry the  structural loads of the skin it replaces.

  

 Aircraft utilizing fuel bladders or "wet  wings" are specifically designed for that purpose. The CJ is not.

  

 My original comments were rather "tongue in cheek"  in that there is no possibility (IMHO) that the tank access panel could ever  come close to supporting a 9G test load as would be required for such a  modification to a certificated Acrobatic Category  aircraft. I doubt that it would reach 4 G's without  failure. 

  

 Of course the FAA does not require any such testing  for the CJ but they do have other resources if CJ parts start falling on  the general public. They simply ground them all and Transport Canada follows  suit. 

  

  Walt   

  

  

 [quote]   ---

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brian-1927(at)lloyd.com
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Posted: Sun Mar 23, 2008 7:17 pm Post subject: More fuel

On Mar 23, 2008, at 3:19 PM, Walter Lannon wrote:

 	  Quote: 	
		  

 I thought my comments (at the bottom of Doug's message below) on the  

 modifications to increase CJ6 fuel capacity would generate some  

 interest and further comment. Apparently not.

 Brian; where are you?


	


Right here. Since we were doing a complete restoration of The Project  

I went with Doug's center-section aux tanks. I still have the stock  

main tanks. The installation and structure appeared to be adequate to  

the task but I am open for discussion.



 	  Quote: 	
		   So, since I believe this subject is of paramount importance to the  

 continued operation of the CJ, I will try again. My comments refer  

 to the bladder modification but really apply to all fuel increase  

 mods. that increase the applied loads and/or change the design load  

 paths.



 The existing fuel loads are transmitted directly to the front and  

 rear spars through the tank, the support straps and upper surface  

 inter-spar structure.  A very well proven and traditional method of  

 supporting metal tanks.

 The tank access panel is just that, a means of access. It carries  

 none of the fuel load and is designed only to carry the structural  

 loads of the skin it replaces.



 Aircraft utilizing fuel bladders or "wet wings" are specifically  

 designed for that purpose. The CJ is not.



 My original comments were rather "tongue in cheek" in that there is  

 no possibility (IMHO) that the tank access panel could ever come  

 close to supporting a 9G test load as would be required for such a  

 modification to acertificated Acrobatic Category aircraft. I doubt  

 that it would reach 4 G's without failure.



 Of course the FAA does not require any such testing for the CJ but  

 they do have other resources if CJ parts start falling on the  

 general public. They simply ground them all and Transport Canada  

 follows suit.


	


Well, so far, not many CJs are falling from the sky. OTOH, I suspect  

that most people who put the extra fuel in are not using them to do 6G  

acro. Regardless, I think your point is well taken.



--

Brian Lloyd                         3191 Western Drive

brian HYPHEN 1927 AT lloyd DOT com    Cameron Park, CA 95682

+1.916.367.2131 (voice)             +1.270.912.0788 (fax)



I fly because it releases my mind from the tyranny of petty things . . .

— Antoine de Saint-Exupéry



PGP key ID:          12095C52A32A1B6C

PGP key fingerprint: 3B1D BA11 4913 3254 B6E0  CC09 1209 5C52 A32A 1B6C

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viperdoc(at)mindspring.co
Guest

Posted: Sun Mar 23, 2008 9:12 pm Post subject: More fuel

Brian,

With the bladder mod as I understand and have seen with the YAK-52, the

access panel does bear the load of the fuel in the bladder. For the 52, we

are talking about 25 gallons per side calculated but with foam and mods to

accommodate the strap mounts it comes out to 46 gal total. As I understand

the YAKOLEV engineers have approved the bladders as stated by one of our EU

listers. Their recommendation is that acro be done at reduce fuel load (1/2

approximately). I could only assume that would be the case with the CJ also.

FWIW, the straps are removed from the fuel bay on the 52 so there is no

distribution of the load to the spar from what I see. It is born by

attachment to the fuel filler mouth on the top of the wing. Again no data on

G loads only the assumption that 7lb/gal X XG's will be carried by the

access panel and the flange mounted to the filler mouth. 

So as Walt says load the fuel bay panels with caution. The floor of the

bladder is supported by that panel and industrial strength Velcro.

I will most likely install the bladders in due time after observing the

progress of the first few installed. I have a couple of questions unanswered

as yet. 

If you are going to fly the plane pretty much in finger tip or some

variation thereof, then I would not be too worried about the  G loads on the

panel. 

This is not being said to disparage the manufacturer or the distributors of

the bladders. I have even looked into having them made for the 50 when my

main tank sprang a leak at one of the button welds for the baffle. There are

again questions about distribution of G loads. The manufactures' (and mine)

calculations indicate that the 50 would pickup an additional 18 gal. That

would be great for XC but not for around the local drome doing Acro or

flying formation. Fabricating a drop tank would be a better choice probably.

Even with the internal AUX tank, the recommendations are that it be flown

with no more than 15 gal in the acro tank when flying acro. Since we do not

have the data from the YAKOLEV design bureau as to why that restriction was

placed on the aircraft I cannot comment but only assume the bulkheads were

not designed to carry G loads at anything above 15 gallons in the bladder

safely when performing acro. I guess that would be in keeping with the

recommendations of the design bureau would it not?

So saying that be careful with those tanks resting on the fuel bay panels.

Now I do know that an engineer has installed the bladders for the 52 and

will be testing them. Time will answer the questions. But for now, it is

150-200 NM legs on an XC. I'm not an aeronautical engineer and I did not

sleep in a Holiday Inn Express last night so I will wait for a few more

answers.

Viperdoc    



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dsavarese(at)elmore.rr.co
Guest

Posted: Mon Mar 24, 2008 2:27 am Post subject: More fuel

One minor correction.  The bladders are not "supported" by Velcro.  IF the 

installer uses the Velcro during installation, it is used to retain the 

bladder shape without fuel in it, along with the fuel filler plate affixed 

to the top surface of the fuel filler opening in the wing.  Installing the 

foam in the bladder is the preferred method of bladder shape retention. 

Plus the foam provides the baffling inside the tank to reduce the sloshing 

of the fuel.  Simulated G-Load testing was accomplished on the 52 bladder 

while installed in the aircraft, to 7.5G's.  The fuel cavity cover plate, 

which on the 52 is a braced cover plate, exhibited no structural stressing.

Dennis



---

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