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Fuel Tanks
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super58d

Joined: 15 Sep 2008
Posts: 52
Location: Savannah, GA

Posted: Mon Feb 14, 2011 11:48 am Post subject: Fuel Tanks

Does anyone have pictures, or any factory information, on how the fuel tanks are supposed to fit into the wings? Are they mounted in somehow, or do they just sit in there and rest on the skins? I saw some of the pics on the factory disk, but they aren't very helpful (unless I'm missing the ones I'm looking for). Also, does anyone know of some 640 builder's websites out there? Christian Tremblay had a great one with lots of good pics, but he got rid of it. 



Thanks

_________________
Mark
s/n 094

My Build Site:
http://www.mykitlog.com/stephen363/

Scott Stewart

Joined: 29 Jul 2008
Posts: 30
Location: Windsor, California

Posted: Mon Feb 14, 2011 12:47 pm Post subject: Re: Fuel Tanks

Hi Mark,



The fuel tank needs to be laid into the wing cavity, with enough cork to ensure a snug and consistent fit at all points.  The weight load needs to be evenly supported by all of the rivets holding the leading edge skin to the spar.  Unfortunately, this part of the wing documentation is a bit light.



Christian's site was the best one out there.  Jeff Paden's site is also down.  Perhaps you could start one?

_________________
Scott Stewart
CH-640 built from plans
Flying since August 2014

doug_geese(at)fwmetals.co
Guest

Posted: Mon Feb 14, 2011 1:25 pm Post subject: Fuel Tanks

Mark,



I have a single picture of mine.  They just sit in there on cork.



Doug



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pilot4pay

Joined: 01 Jan 2007
Posts: 171
Location: Louisville, KY

Posted: Mon Feb 14, 2011 2:12 pm Post subject: Re: Fuel Tanks

Chris has an earlier post on the ext. range tank on page 2, but it doesn't show the tank installed in the wing.

I think the 601/650 has a"similar" installation. You might have a look at some of their info.

I'm going to build my own tanks, as I'm going with a 4 tank installation, and the cost of 4 factory tanks will pay for a good TIG welder. Once I make the forming dies, I can make any number of tanks, if any one is interested.

_________________
Craig Smith
CH640 builder
SN: 0078

"Just think how stupid the average person is,
and then realize that half of them are even stupider!"
--George Carlin

super58d

Joined: 15 Sep 2008
Posts: 52
Location: Savannah, GA

Posted: Tue Feb 15, 2011 4:01 am Post subject: Re: Fuel Tanks

Thanks for the pics and info guys. That does help. I'm not sure why they call this a 51% kit. I seem to be doing a lot of planning and engineering on my own! Anyway, I updated my signature block to include my Kitlog page. That's all i have as far as a website and pictures right now. Maybe I can start my own website or a CH-640 webring in the future, I just have too many other things going on right now. Thanks again for the prompt replies.

_________________
Mark
s/n 094

My Build Site:
http://www.mykitlog.com/stephen363/

steveadams

Joined: 10 Jan 2006
Posts: 191

Posted: Tue Feb 15, 2011 12:02 pm Post subject: Re: Fuel Tanks

One thing to remember is that the tank is isolated from the airframe electrically. The plans show a tab welded on the tank to connect a grounding strap to the spar. My tank did not come with the tab so I had to have one welded on. I guess the filler cap likely grounds the tank to the skins, but I would make sure you do something to ensure a good ground if your tanks did not come with the tab.



Steve

super58d

Joined: 15 Sep 2008
Posts: 52
Location: Savannah, GA

Posted: Tue Feb 15, 2011 5:00 pm Post subject: Re: Fuel Tanks

Thanks Steve, I did stumble across a factory pic of that grounding attachment while browsing the disk luckily. It made me start thinking of all the little things that aren't mentioned in the IPLs... I found back in the miscellaneous section that all the grounding straps are for an IFR equipped aircraft. Day VFR shouldn't need them all. Mine will be for IFR, so I will need them. Static wicks too.

_________________
Mark
s/n 094

My Build Site:
http://www.mykitlog.com/stephen363/

pilot4pay

Joined: 01 Jan 2007
Posts: 171
Location: Louisville, KY

Posted: Tue Feb 15, 2011 5:43 pm Post subject: Re: Fuel Tanks

Mark, I think you and I are probably about the same state of build (you're probably a bit ahead with wings). I can make you a set of grounding straps. I have a roll of braided plated ribbon. I'll be flying IFR as well.

What state of kit have you purchased?

As soon as things warm up a bit, I'll be steady in the shop. I have a sheet metal roller, English wheel, TIG, MIG, torch, Smithy lathe/mill.

Let's try to pool some resources. Once you set up to make some things, the tough part is over.

_________________
Craig Smith
CH640 builder
SN: 0078

"Just think how stupid the average person is,
and then realize that half of them are even stupider!"
--George Carlin

super58d

Joined: 15 Sep 2008
Posts: 52
Location: Savannah, GA

Posted: Thu Feb 17, 2011 4:55 pm Post subject: Re: Fuel Tanks

Hey Craig,

  I'm on the right wing, and probably going a bit out of order. I started the wings with the top up, not realizing that bottom up may be the better method. Anyway, I also jumped ahead a bit and drilled and clecoed all the rear riblets. I had to replace the spar extension, and just got that complete. This weekend I'll be putting the  rear top skins on, then flipping it over and starting the other stuff. The grounding straps would be great! Also, I need the front channel and doubler piece made again for one side. If you have the tools (and time) tom make those two pieces I'd be happy to pay you as I'm sure it'll be cheaper than paying Zenair. I can buy the aluminum and have it shipped to your house as well. So far I have the tail kit, wing kit, extended range tanks, fuel system kit, landing light kit and I got all the position lights through other sources. I'll be looking at getting the fuselage and other kits here about mid-summer I imagine. I added my kitlog web address to my signature block so give me a couple days to post everything I've done and you can see what I've accomplished so far. It'd be great if we can help each other out. I'm an avionics guy and get a lot of stuff off e-bay or through other contacts. I have a butt-ton of circuit breakers!!

_________________
Mark
s/n 094

My Build Site:
http://www.mykitlog.com/stephen363/

pilot4pay

Joined: 01 Jan 2007
Posts: 171
Location: Louisville, KY

Posted: Fri Feb 18, 2011 6:39 am Post subject: Re: Fuel Tanks

You are one busy beaver! But I'll bet you have heat in your shop too.

I need to get hot this year. I'll look over your wish list and get back with you.

_________________
Craig Smith
CH640 builder
SN: 0078

"Just think how stupid the average person is,
and then realize that half of them are even stupider!"
--George Carlin

pilot4pay

Joined: 01 Jan 2007
Posts: 171
Location: Louisville, KY

Posted: Sun Feb 20, 2011 3:02 pm Post subject: Re: Fuel Tanks

Heh, the only 2 metal forming tools I don't have are a a shear and a brake. You may want to get them from Zenair. I'll make up a set of strap for ya though, no problem. How soon do you need them?

_________________
Craig Smith
CH640 builder
SN: 0078

"Just think how stupid the average person is,
and then realize that half of them are even stupider!"
--George Carlin

super58d

Joined: 15 Sep 2008
Posts: 52
Location: Savannah, GA

Posted: Wed Feb 23, 2011 9:18 am Post subject: Re: Fuel Tanks

oh, I'm not in a huge hurry. I think I'll be ready to seal up that side of the wing in about 6 weeks. I ran into a slight snafu with the rear ribs. (Check out my aileron bellcrank post I'll submitting here shortly if you are curious). Anyway, I appreciate the offer for the straps. They'll come in handy. Now we have to find an inexpensive place to buy static discharge wicks. They are EXPENSIVE new!!

_________________
Mark
s/n 094

My Build Site:
http://www.mykitlog.com/stephen363/

super58d

Joined: 15 Sep 2008
Posts: 52
Location: Savannah, GA

Posted: Wed Feb 23, 2011 4:29 pm Post subject: Re: Fuel Tanks

Ok, so I have another question on the wing tank. The plans say that from rib #5 to rib #1 there is approximately a 12 degree increase when the wing is flat on the table. When I use a level and angle measure, however, a 12 degree angle puts the fuel line hole way at the top of rib #1. Basically, I was wondering if anyone had a good way to judge where the holes should be drilled in the fwd ribs for the fuel hose placement. 



Also, I want to install a fuel  injected engine. I'm told there needs to be a return back to the tank for fuel injection and am just looking for some idea of where to attach the return line and how to run it. Thanks in advance for the help again guys.

_________________
Mark
s/n 094

My Build Site:
http://www.mykitlog.com/stephen363/

Scott Stewart

Joined: 29 Jul 2008
Posts: 30
Location: Windsor, California

Posted: Thu Feb 24, 2011 11:16 am Post subject: Re: Fuel Tanks

Hi Mark,



I discarded the 12 degree call-out and recalculated the numbers.  The fuel line needs to run slightly "uphill" from the tank outlet to the fuel selector, and this run should be as straight as practical to minimize pressure loss (minimize the force required by the fuel pump).  Factoring the wing dihedral angle and the total distance the line needs to run, I calculated a 10 degree slope through the front ribs.  Depending on how you want to route the fuel line, this value may change for you, so I recommend doing your own calculations.

_________________
Scott Stewart
CH-640 built from plans
Flying since August 2014

pilot4pay

Joined: 01 Jan 2007
Posts: 171
Location: Louisville, KY

Posted: Thu Feb 24, 2011 1:49 pm Post subject: Re: Fuel Tanks

What I know about fuel injected systems.

I'm going with an auto conversion and fuel injection also. My understanding is that each tank must have provision for a return line, and that the fuel selector valve should be a ganged unit, so that supply and return are paired to the tank in use. Bad things happen when this is not followed. I looked into my old T182T POH and examined the fuel system cartoon, and indeed there are fuel return lines in the drawing. The details will end up being specific to your engine choice but I believe that locating the return port as high on the tank as practical is the correct way to do this. The reason for a high port is you won't ever be pushing against the weight of the fuel in the tank as part of the pumping "head". I have some cartoons from my rotary engine group with various configurations of systems. Another method would be to have a header tank located near the engine, that would require one pump for filling the header, and another to pump from the header tank to engine, with fuel return line to header tank only.

There are also marine type ganged fuel selector valves that are hundreds of dollars cheaper than the aviation valves, but their brass bodies are heavier. I will take the small weight penalty, to save hundreds of dollars.

The only problem I have yet to fully solve are my need to have exact fuel consumption data, and the return line system makes this somewhat more complicated. There are certified flow meters that have a subtractive side, but they are an arm and a leg. So that point is still unsettled. There are several ways to skin that cat, still thinking.

If you want more info on fuel systems I can forward you a whole bunch of e-mails worth of discussion, don't forget to search the other Zenith lists too.

Hope this helps.

_________________
Craig Smith
CH640 builder
SN: 0078

"Just think how stupid the average person is,
and then realize that half of them are even stupider!"
--George Carlin

pilot4pay

Joined: 01 Jan 2007
Posts: 171
Location: Louisville, KY

Posted: Sat Feb 26, 2011 2:30 pm Post subject: Re: Fuel Tanks

Hey Mark! I just wanted to touch base with you on those straps. I wanted to be sure that the material I have is what is being referred to in the drawing 640-M-73. It's hard to tell by the drawing as it is a simple line drawing, but the Newark catalog comes up with an Alpha wire braided sleeving. The part number has changed, but I'm sure what I have is suitable and equivalent. Now, there are two ways to skin this cat. One is easy, and it involves using a standard wire ring terminal (sized for the proper cross sectional area) crimped onto the braid. The second and more difficult would be to fabricate a flat terminal. If you will need the height of the terminal to ensure it will fit, let me know and I will get it for you before we make them up. Newark wants $16/ft for the braid. I'm not asking for a nickel.

I can also fabricate the grounding cables from dwg 640-E-17 -2 thru -6.

The-1 cable runs from the rear mounted battery to the engine, and I don't believe I have enough material for that.

_________________
Craig Smith
CH640 builder
SN: 0078

"Just think how stupid the average person is,
and then realize that half of them are even stupider!"
--George Carlin

super58d

Joined: 15 Sep 2008
Posts: 52
Location: Savannah, GA

Posted: Thu Apr 14, 2011 7:09 am Post subject: Re: Fuel Tanks

I ran across a couple more questions about the fuel tanks if anyone can help: 



The fuel sender float arm needs to be bent. Does anyone have a measurement of how far back from either end it needs to be bent and is is a 90 degree angle? I assume the end that attaches to the sending unit only needs to go into the rotating attachment far enough to catch on the opposite stop?



The fuel sender instructions talk about a back plate and cut-out to get it inn the tank. Is it possible to attach the sender directly to the tank, the metal there has been beefed up and looks like it could handle it. If so, what hardware is recommended for use?



The sender goes from 10-180 ohms. Is the lower resistance for a full or empty tank?



For the tank fittings (finger strainer, drain valve, gas cap, etc) do I need to coat them with a sealant, o-rings, or pipe tape or will they make a good seal on their own ?  



I realized that the tank sits too far forward and won't allow the skins to sit flush with the ribs, so I now have to trim the "L" brackets on the spar and and add "L" brackets to them for that isolation mentioned in an earlier post. Craig, if you have any pics, drawings, or data on electronic fuel injection I'd love to see what you have if you wouldn't mind posting it here or e-mailing it to me. Any help on these issues would be greatly appreciated.

_________________
Mark
s/n 094

My Build Site:
http://www.mykitlog.com/stephen363/

steveadams

Joined: 10 Jan 2006
Posts: 191

Posted: Thu Apr 21, 2011 4:04 am Post subject: Re: Fuel Tanks

You don't need a back plate for the fuel senders. Just tap the holes and screw it onto the tank. I used something called "sealube" from aircraft spruce on the tank fittings as well as the screws that hold the senders on. It is like a thick paste which does not harden, and is not soluble in gas. As far as the bend for the floats, it is approximately a 90 deg bend but takes a little trial and error to get right. I actually mounted mine with the floats facing back toward the inboard end of the tank to better measure fuel from 1/2 full to empty. Because of the slope of the tank in the wing, putting them the other way will read empty when there is still 4-5 gallons of fuel in the tank. I am attaching a photo of how I bent one of the senders. It is not pretty, but it works.



Steve

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super58d

Joined: 15 Sep 2008
Posts: 52
Location: Savannah, GA

Posted: Thu Apr 21, 2011 7:53 am Post subject: Re: Fuel Tanks

Awesome Steve, thanks a lot that helps quite a bit. Looks like your finger got caught somewhere you didn't want it to! Ouch.

_________________
Mark
s/n 094

My Build Site:
http://www.mykitlog.com/stephen363/

steveadams

Joined: 10 Jan 2006
Posts: 191

Posted: Thu Apr 21, 2011 9:18 am Post subject: Re: Fuel Tanks

 	  super58d wrote: 	
		  Awesome Steve, thanks a lot that helps quite a bit. Looks like your finger got caught somewhere you didn't want it to! Ouch. 	




Yeah, probably finessing the darn sender in and out of the tank 20 times getting the bend right.

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