Question: What is the typical capacity of the fuel tanks supplied with VMAR ARF models?

Answer: Generally 300-350ml (10-12oz)

Better Answer: To be sure you will need to determine exact capacity using a measured amount of clean water. Tanks with a plastic stopper cap, two lines and a notch in the front are approx 300ml (10oz) in capacity. Tanks without a notch in the front range up to 315-350ml (11-12oz). For more information please review the specifications for the particular tank of interest.

There are some exceptions: Control Line and small RC ARF's have a 100ml (3.3oz) tank. Dornier DO27 45 ARF's with the squat short tank have a 250ml (8oz) capacity and larger models like the 10 foot span Dehavilland Beaver have a 750ml (26oz) tank.

Question: Once the fuel tank is assembled how do I install and secure it into my VMAR Trainer?

Answer: After assembly and pressure test, install the tank with the metal tubes protected and facing up. Use sealant to secure the black gasket to the tank and firewall from behind. Seal around neck from front. Support & surround tank with sponge foam.

Better Answer: VMAR Trainers and other non-cowled VMAR models generally do not have a power module. After tank assemly per the instruction book (all tanks assemble in a similar manner) do a pressure test and then protect the metal tubes from contamination by taping up the open ends or running a short length of fuel line between the metal tubes. Now apply sealant to both sides of black donut like rubber gasket and around the neck of the tank. Use Pacer Dap-A-Goo or clear silicone. Install the tank into the fuel tank compartment of the fuselage with the metal tubes facing up. Press the tank and sealant bead firmly against the back of the firewall and secure the tank while the sealant cures. Seal around the neck from the front of the fuselage to prevent fuel seapage into the fuselage. Support and surround the tank in the fuel tank compartment with sponge foam.

Note that in most cases, the receiver batttery pack is to be wrapped in cling film and installed beneath the fuel tank. Consult your radio manual for more information. In this case, the sponge foam should be arranged to support the tank and the battery pack.

Question: How do I install my fuel tank and seal the fuel tank neck area where it protrudes through the firewall.

Answer: Plan your fuel tank installation per the instructions in the manual that came with your model. Orient the tank and the metal tubes etc and install the tank clunk, tubing and stopper. See the illlustrations in your manual. Once you have the tank prepared, connect silicone tubing between the metal tubes so that the metal tubes are closed off and no dirt or material can get inside the metal tubing or your tank while you are working on it. Plan the position of your tank in the fuel tank compartment. See your manual. You may need some foam rubber pads or other material to position the tank on models that are not equipped with a power module. If the model has a power module, seal both sides of the forward firewall with epoxy or finishing resin and let it dry. Make sure you can dry fit the tank into place where you want it before proceeding to the next step. See your manual.

Once you have everything prepared you are ready to seal the tank into place. You will need some clear silicone or Pacer Dap-A-Goo sealant. Dap-A-Goo is perfect for this job. It's thick, dries quickly and seals well. On VMAR fuel tanks there is a foam rubber gasket around the neck of the tank. Remove the gasket. Apply a bead of sealant to the forward face of the tank in a circle about 1/4" (6mm) away from the neck. Re-install the foam rubber gasket and press it down onto the sealer. If your model has a power module system, apply a bead of sealant to the top of each dowel protruding from the back of the firewall. Keep moving and apply a second bead of sealant to the exposed face of the foam rubber gasket and press the tank firmly against the back of the firewall (and resting on the dowels if you have a power module system). Hold the tank in place with tape, elastic bands or other retainers and let the sealant dry. Apply additional sealant around the tubes (along the sides of the power module dowels if so equipped) and into the firewall passage hole from the front face of the firewall. Let the sealant dry. Remove any unnecessary retainers if they are no longer needed. Your tank is now installed and sealed into place.

Question: After I had flown for about 3 weeks or so, my fuel tank split and fuel leaked into the foreward part of the fuselage. Any ideas what caused the tank to split?

Answer: Well you won't like to hear this... we test all our tanks before shipping and you tested it again after you assembled and installed it. So we know it was not leaking when you installed it into the ARF. We have done extensive testing and tanks that split anywhere from1 day or so to 6 months or more after installation do so when the stopper retaining screw has been overtightened. This compresses the stopper longtudinally and expands it laterally which of course is what seals the stopper in place. However, when the stopper screw is overtightened, the lateral expansion of the stopper becomes excessive and the tremendous pressure eventually splits the tank.

So... if you are using our tank or any other brand of tank, if you overtighten the stopper it will eventually split the tank or split the stopper... usually the tank. There are two ways to avoid this problem... go light on the torque... you want a seal yes but there is no need to really reaf on it. Secondly, recognizing that some folks like to use the same tools for a model airplane as a tractor (sorry but it's true), we invented our safety stopper to further reduce the chances that the tank will split.

Here is some information about our safety stopper.

Question: What does it mean in a VMAR model when I see the term "Safety Stopper"?

Answer: Beginning in mid 2004, the VMAR factory began a gradual change to a new 3 line tank with a metal overcap that aside from the convenience of a 3 line tank, helps prevent tank splitting due to overtightening of the stopper expansion bolt. The metal cap covers the end of the stopper like the older plastic disk units and also extends down and around the neck of the tank to prevent the stopper from being over compressed and splitting the tank. So, we call this new stopper and metal cap system "Safety Stopper" because it helps prevent the tank from splitting.

Question: Which models come with fuel tanks equipped with the three line safety stopper?

Answer: The three line safety stopper was introduced into production across the VMAR ARF line in mid 2004.

Modelers who may wish to upgrade to the three line safety stopper can purchase this stopper as part number VMA-TANKCAP3

Question: My VMAR ARF model came with a three (3) line fuel tank stopper. What is the third line for?

Answer: The third line is a fuel fill line that allows you to fill the fuel tank without using the line that normally supplies fuel to the carburetor.

More Information: With a two line system, one fuel line supplies fuel from the fuel tank to the carburetor and the other line normally supplies muffler pressure to the fuel tank. When adding fuel to the tank, since there is a clunk on the fuel end of the line running to the carburetor, filling must take place through this fuel supply line which necessitates removing the line from the carburetor fuel nipple. This is a nuisance and can result in a split at the end of line when done many times. Such splits can result in leakage and difficulty in setting a reliable mixture setting.

By adding a third line, the fuel line that supplies fuel to the carburetor can be left in place during fueling. Fuel is added to the fuel tank through the fuel fill line (i.e. the third line).

After fueling close the fuel fill line off with a plug to allow the muffler pressure line to pressurize the fuel tank.

Note: Most engine manufacturers stress the importance of NOT flooding the engine with fuel during the fueling process. If you flood the engine with fuel and then try to turn it over with an electric starter you can severely damage any or all of the following components; piston, wrist pin, connecting rod, crank pin. This will not be covered by warranty and will necessitate a very expensive repair. The best way to avoid this is to ALWAYS do the following:

• Remove the pressure line from the muffler during fueling
• Turn the engine over by hand without glow plug or spark plug power. Rotate the engine through a full 360 degrees by hand before using an electric starter. If you cannot rotate the engine by hand, do NOT use an electric starter. Drain excess fuel from the cylinder and try again.

Question: Which models come with fuel tanks equipped with straight tubes?  

Answer: The three line safety stopper was introduced into production across the VMAR ARF line in mid 2004. The straight tubes were also phased in at that time. The tubes can be bent from straight or left as is depending on the application.

Kits introduced prior to mid 2004 may have Assembly and Operations Manuals showing the older two line tank with no safety stopper and bent tubes. The new tank, safety stopper and straight tubes have superceded the assembly shown.

Question: What does it mean in a VMAR model when I see the term "Safety Stopper"?

Answer: Beginning in mid 2004, the VMAR factory began a gradual change to a new 3 line tank with a metal overcap that aside from the convenience of a 3 line tank, helps prevent tank splitting due to overtightening of the stopper expansion bolt. The metal cap covers the end of the stopper like the older plastic disk units and also extends down and around the neck of the tank to prevent the stopper from being over compressed and splitting the tank. So, we call this new stopper and metal cap system "Safety Stopper" because it helps prevent the tank from splitting.