Gas Bag Setups

 

Collapsible bags make excellent gas tanks. They may carry different names – IV bag, saline bag, bladders, etc. We'll use the term "bag", so no one will take offense to differing terminology. This How-To is intended to help you make the switch from the old style hard tanks and even the newer "made for gas" tanks and cells, to an excellent alternative proven by racers and recreational boaters alike.

Advantages:

Disadvantages:

 

 

You will need an appropriate length of Tygon tubing, a Bag of suitable size, a short length of 5/32 brass or aluminum tube, and a zip tie (or similar tubing clamp). Note: It is very important that you do not use silicon tubing for gasoline! Silicone should only be used for water lines on your boat!

Once inserted, secure with a zip tie wrap. Make absolutely sure the zip tie is as tight as you can get it, because if the bag is going to leak, it will do so at this connection! Your bag turned tank is now finished and should resemble the photo.

 

Plan for success, then mount the bag. Mounting methods basically fall into two categories; Lay it flat in the hull, or hang the bag from a hook mounted under the deck or side of the boat. If the bag is laid flat in the bottom of the hull, it may be necessary to remove all the air from the bag – called "burping" the bag. A flat bag install does allow the bag to be positioned under the motor, closer to the CG of the boat.

if the bag is hung at an angle or vertically, with the outlet facing down, there is very little risk of having any air ingested into the fuel line. This can eliminate the need to burp the bag, and simplifies filling. But, it might mean positioning the bag in a traditional location (similar to a hard tank). A good combination is to place the bag under the engine , outlet facing the transom, and elevate the bow end of the bag. A 1000ml bag works well in this case.

In the photos above, you can see a flat mount, using a zip tie with a lock on each end between the stringers and through the hanger hole in the top of the bag. This particular install uses a quick fill device, but this is for convenience only and not a necessity.

In these photos you can see two different "hanging bag" installs to get a good idea of what it takes. This one uses a rubber band to keep the bag from swinging around while the boat is under way. The dark barbed tubing coupler makes a convenient place to hook up the filler line from your gas pump when filling the tank.

ed. Brad Mahs (www.modelgasboats.com)

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