Minimalistic gas tanks

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rtfm

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Hi,
In between finishing off the rear wing of the Fleabike, I'm starting to think more about the gas tank. Fuel pump, gas filler cap, fuel drain - plus all the holes in the tank these pieces require. Surely there is a safe minimalist way of doing things? This super-neat gyro seems to have a store-bought plastic tank. Not sure how the fuel gets from the tank to the engine, but I'm assuming some sort of immersible pump?

Any help of pointers to videos/pictures etc would be helpful.

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rtfm

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I was thinking of two of these fastened to the outside of the Fleabike (12l each). It comes with a vented fuel cap and a fuel pickup/filter fitting. I could run each of them into a single fuel pump?
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Fuel pump possibility?
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On the other hand, I could fabricate a pair of more erognomic tanks myself and buy the fittings? Probably not as crash-resistent as the polyethylene variety...
 

rtfm

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Duncan, your first and most appropriate method by far is to use the Good Lord's own gift of gravity to get the fuel from the tank to the carburetor. There would have to be a really good reason to not use this on the FleaBike.
Hi. Agreed, but where to put it? The only two places which suggest themselves are on the top of the cowl (need to fair it aerodynamically) and the other is inside the front wing (the outline can just be seen). Neither is optimal, although both are single fuel cells, which is good. And both are gravity fed. Not sure how having the fuel in a pivoting wing would work...
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BJC

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Duncan:

There was a thread some years ago about fuel tanks that could be fueled at a gas station then strapped into the airframe. Lots of relevant comments / suggestions there. Hopefully, your search skills are better than mine, because I can’t find the thread.


BJC
 

rtfm

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The advantage of placing it in front of the windshield is that I can fabricate it from vinylester and have it translucent for an immediate fuel gauge reference. Also, easy to fill, and somehow comforting to be able to see the tank, instead of it being hidden in the wing. From initial calculations, it will hold 23 litres.
 

Dana

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What engine? If a 2-stroke, the Mikuni pulse pumps are by far the simplest other than gravity feed. Note that the carburetor float needle size may need to change depending on whether it's gravity or pump feed, and for gravity you may need a certain minimum amount of head (vertical distance between the bottom of the tank and the carburetor).

You should only need two holes in the tank: filler and outlet. I don't know what's available in Australia, but plastic marine tanks are probably a good start, and are already set up with fill and outlet connections.
 

Malcolm C

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Unless the filler cap is vented you will also need a vent otherwise you will suffer fuel starvation due to the vacuum forming in the tank as the fuel is used.
 

Dana

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Unless the filler cap is vented you will also need a vent otherwise you will suffer fuel starvation due to the vacuum forming in the tank as the fuel is used.
True. Most commercial plastic tanks have vented caps, though.
 

Vigilant1

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The vent deserves some thought, and may be worth a separate line going above the tank and pointed into the breeze or otherwise in an area of positive pressure.. You don't want fuel spilling out of it when you change attitude/bank, or when the tank is full and fuel sloshes around (especially when it sloshes forward on braking). Also note that spilled fuel (from sloppy refilling, from a vent, etc) can craze, fog, and quickly destroy some plastics (including polycarbonate (aka Lexan), which is very popular for windscreens).
 
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Hi. Agreed, but where to put it? The only two places which suggest themselves are on the top of the cowl (need to fair it aerodynamically) and the other is inside the front wing (the outline can just be seen). Neither is optimal, although both are single fuel cells, which is good. And both are gravity fed. Not sure how having the fuel in a pivoting wing would work...
View attachment 124033
The HM-14 had the fuel tank in the wing. Another look at the Bouquin might give some ideas.
 

rv7charlie

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What engine? Most carbs only want 2-4 psi max. Facet also makes 'cube' pumps that are a bit cheaper & smaller/lighter; common in many homebuilts.

Depending on mount possibilities, boat tanks are a good option, but many ultralites use light weight general purpose plastic tanks. Here's a link to the ones (direct from a mfgr) that Kolb has used in several models.

Kolb tank
 

Pilot-34

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The advantage of placing it in front of the windshield is that I can fabricate it from vinylester and have it translucent for an immediate fuel gauge reference. Also, easy to fill, and somehow comforting to be able to see the tank, instead of it being hidden in the wing. From initial calculations, it will hold 23 litres.
I think being able to see at least the last two or 3 gallons of gas should be a requirement, not a law or regulation but just one of those common sense things people do and don’t argue about like putting the wheels on the bottom.
 

Skinnybird

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Pull one from the Bede playbook and use hollow struts as a four barrel fuel tank...
 

Daleandee

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Duncan, your first and most appropriate method by far is to use the Good Lord's own gift of gravity to get the fuel from the tank to the carburetor. There would have to be a really good reason to not use this on the FleaBike.

I like gravity. My Cleanex has the tank between the panel & firewall and fuel is gravity fed to a Marvel MA-3SPA carb under the engine. No fuel pump required and as Pops always says, "if it ain't there it costs nothing, weighs nothing, and can't fail."
 
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