Fuel Tank

[Poorman2]

This week I built a box with internal demintions of 26 inches long x8inches wide x 6inches deep just as a proof of volumn. I put a plastic garbage bag inside and added 5 gallons of water. There was room to spare for expantion of gas vapors. This size will work above my fuselage top bar if I raise my wing attach square tube up to where my wing is flush with the top bar (approx. 2 inches) and spread the square tube bolt centers to 4.5 inches instead of 2.5 inches. Since I am building the LEXL this should be easy. Of course this causes the streamlined struts to be longer. Are there any other reasons I may be missing that this can't be done? Just adding food for thought. It would not be as easy on the plain LE.

[scottiniowa]

This week I built a box with internal demintions of 26 inches long x8inches wide x 6inches deep just as a proof of volumn. I put a plastic garbage bag inside and added 5 gallons of water. There was room to spare for expantion of gas vapors. This size will work above my fuselage top bar if I raise my wing attach square tube up to where my wing is flush with the top bar (approx. 2 inches) and spread the square tube bolt centers to 4.5 inches instead of 2.5 inches. Since I am building the LEXL this should be easy. Of course this causes the streamlined struts to be longer. Are there any other reasons I may be missing that this can't be done? Just adding food for thought. It would not be as easy on the plain LE.

Ok, being we are calling out exact dimensions, lets do some quick math.

you have tube bolt centers called out at 4.5 inches- yes
and wing rib edge is 2" to center of strap hole (sheet 35)  -yes?

So we add these and get 8.5" MAX space between centers- yes? for a 1/4" tank gap (outsides)
And if we use the 1/2" radius also called out on sheet 35 for the wing straps this would consume 1" fore and aft of tank- yes? or a 1/4" distance at least past your tank sides.
And using the strap distance of 27" spread, this also gives you 1/2" for your nuts to fit in.
While tight, I guess things have been in tighter places. And there are tools for holding nuts for situations like this.

Now for strength calculations- Someone, somewhere probably knows how to do the difference. I don't.

[Poorman2]

Scott, My intention is to leave my wings attached after I first install them, then add the tank. The tank is just a simple rectangle. Should be easy to make. If I wanted to remove the wings so I could trailer it, I would shorten it just a little and add the upper shape of the wing to get my volume correct. I like the idea of having the tank right over the CG. You could add a rollover valve from a dirt racing supplier to the vent on the cap to keep the gas in the tank in case of a tip over. They are very cheep and they do work ( been there, done that ). Just weld aluminum angle to each end to fasten to the square wing cross tubes. As far as the outlets, one in the right front and one in the right rear with a fall of about 6 inches back to front and a tee  where they meet at the front. I know this would have it's pros and cons. Just thinking out loud right know. I would like as many people to share there input as possible. Thank you. Randy Q.

[scottiniowa]

Scott, My intention is to leave my wings attached after I first install them, then add the tank. The tank is just a simple rectangle. Should be easy to make. If I wanted to remove the wings so I could trailer it, I would shorten it just a little and add the upper shape of the wing to get my volume correct. I like the idea of having the tank right over the CG. You could add a rollover valve from a dirt racing supplier to the vent on the cap to keep the gas in the tank in case of a tip over. They are very cheep and they do work ( been there, done that ). Just weld aluminum angle to each end to fasten to the square wing cross tubes. As far as the outlets, one in the right front and one in the right rear with a fall of about 6 inches back to front and a tee  where they meet at the front. I know this would have it's pros and cons. Just thinking out loud right know. I would like as many people to share there input as possible. Thank you. Randy Q.

Not sure about the height of your rectangle, but having the top profiled to the wing, looks good and is not hard to do. Wind drag would be far lower as well, that XL has plenty of drag already.
Yes, on the CG thing
Yes, you could on the rollover valve as well.
The angles for the support/attach areas are done just like you said.
Not sure where the 6" of fall comes from, as the angle is about 2" if you are talking the center fuselage tube, but if you meant where you would combine the front and rear outlets, then yes I follow you.
On the fuel flow/ simple ground test, at max climb and max decent angles should tell the story.  
All sounds good.

[Flyguyeddy]

I realise this is an old thread, but i have thoughts on this.   

What if a person were to angle the rear of the tank forward on the bottom, perhaps it would move the rear sump parts away from the person’s head an inch or two and also give better access to the wing hold bolts?   Ive been thinking seriously about a center tank that holds 4 gallon or so and maybe a 1 gallon header tank.   Id make the top airfoil shaped and use a windshield like putt putt to cover up the front part of the airfoil (like a cub sort of has).  Thoughts?

[PropMan]

I built an aluminum tank to drop in the wing panel. The top of the tank is airfoil shaped and serves as top of wing in that location

[stevejahr]

It appears that the top also doubles as the mounting flange in addition to being the top of the wing?  Very cool.

I love the pressure test balloon too 

[Tom H]

Very nice, Frank.

[PropMan]

Thanks fellas , 
Steve,  yes that's the plan with the flange.

[MontanaMan]

Hi:  

First ... I want to say that looks like very very nice work, Frank.  Congratulations.  

I have a J3 kitten, which has a heavy fiberglass tank between the panel and the firewall.  I'd like to move the tank up top ... preferably between the wings, but I'm not sure of the headroom there.  I'll have to measure tomorrow.  Your idea is excellent, and I'll be doing something similar to that.

A few questions:

1. What grade of AL did you use?  What thickness?
2. Will you add internal baffles?
3. What did you use to seal the tank?
4. How do you plan to seal the upper joint ... where the top of the tank joins the sides.
5. What will you use as a filler cap?  Any links to where I can get it?
6. How did you attach the filler cap to the top of the tank?  Is it a problem to attach a flat filler cap to a rounded surface?
7  Do you intend to mount the upper flange to the tops of the ribs?  Or will you add additional bracing to the ribs first?

Thanks.

[Terry Lundby]

Check out Bob Hoover's website, (no, not that Bob Hoover), on aluminum tanks   https://bobhooversblog.blogspot.ca/2006/12/av-yo-fuel-tank.html
Also if your an EAA member...
How About An Aluminum Fuel Tank? By Tony Bingelis (originally published in EAA Sport Aviation, December 1986)
It's an easy search.

Good luck.

[PropMan]

http://www.eaglersnest.com/forum/index.php?topic=1636.0
MontanaMan- Here is my thread for the XL fuel tank.
It should have the answers to your questions. and several photos, i  will be adding a few edits to update it soon too.

[MontanaMan]

Thanks for the help.  Frank ... your work is really good.  I just finished reading your entire XL thread.  Can't wait to see how that 3VW motor performs!

-Robert

[Flyguyeddy]

This week I built a box with internal demintions of 26 inches long x8inches wide x 6inches deep just as a proof of volumn. I put a plastic garbage bag inside and added 5 gallons of water. There was room to spare for expantion of gas vapors. This size will work above my fuselage top bar if I raise my wing attach square tube up to where my wing is flush with the top bar (approx. 2 inches) and spread the square tube bolt centers to 4.5 inches instead of 2.5 inches. Since I am building the LEXL this should be easy. Of course this causes the streamlined struts to be longer. Are there any other reasons I may be missing that this can't be done? Just adding food for thought. It would not be as easy on the plain LE.

Ok, being we are calling out exact dimensions, lets do some quick math.

you have tube bolt centers called out at 4.5 inches- yes
and wing rib edge is 2" to center of strap hole (sheet 35)  -yes?

So we add these and get 8.5" MAX space between centers- yes? for a 1/4" tank gap (outsides)
And if we use the 1/2" radius also called out on sheet 35 for the wing straps this would consume 1" fore and aft of tank- yes? or a 1/4" distance at least past your tank sides.
And using the strap distance of 27" spread, this also gives you 1/2" for your nuts to fit in.
While tight, I guess things have been in tighter places. And there are tools for holding nuts for situations like this.

Now for strength calculations- Someone, somewhere probably knows how to do the difference. I don't.

My plans show mounting hole centers on fuselage at 2.5” center to center.   Is 4.5” acceptable?

[Flyguyeddy]

Ah wait, i see where 4.5” comes from now. 

Is that ok to do if one uses 5/8 steel tube and a wider gusset?