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Frequent Asked Questions


The O-Rings on my V2 tank are swollen and will not go back in the grooves?

     The o-rings are made from Buna-N rubber and are designed to swell once in contact with fuel. That is why the grooves in the manifold are so much wider than the o-rings nominal size. The fuel swells the material and seals even tighter in the tank body. The o-rings will shrink back down to nominal size once you wipe the fuel and oil off and leave them sit in the open air for a few hours. Then you can re-assemble your tank. 

Why doesn’t the vent line reach or touch the very top of the tank body?

      The vent line is made slightly short to keep any pressure or contact from pushing on the manifold/tube joint. You will find a couple of mm of clearance will not effect how much fuel the tank holds. Once the tank is installed and you fill it up the entire tank body will be full.

Why doesn't the clunk line have safety wire on it?

      We are using fittings that have retaining barbs engineered to keep the line firmly attached to the fitting. Years of using brass tubing has trained modelers you "must safety wire the clunk" While that is true with rubber stopper type tanks it is not the case with a Fourtitude R/C tank. Rest assured the clunk line will not come off the barbed fitting. We had lots of fun trying to make that happen! 

Why are the clunks not all the way to the back of the tank?

     Fuel line no matter what type expands once in contact with fuel. A six inch fuel line will grow on average about half of an inch once submerged in fuel. If the clunks were too close to the back of the tank this expansion would cause the clunk to hit and restrict free movement. Second reason is the felt filtered clunks we use do not suck the fuel in from the back. Instead they draw fuel in from the sides. Basically there are like a sponge and will suck out every drop of fuel in the tank. Yes we have flight tested this many times by running the tank dry flying hard aerobatics and after landing there is only vapors left in the tank. 

Can I use fuel tanks for smoke or smoke tanks for fuel? 

     Our fuel tanks cannot be used for smoke due to the filtered clunks element not allowing the higher viscosity smoke oils to flow past the filter. Our smoke tanks are configured for the best smoke system performance posable. We do not recommend using the smoke tanks with fuel under any circumstance.


Why are you not using Tygon brand fuel line for the clunk? 

     Years of testing and experience tells us that Tygon brand tubing sold to modelers gets hard and brittle in a very short period of time. After many different bench and flight test we have found that the fuel line we provide has superior lifespan over Tygon. No fuel lines last forever but we want to provide the best product possible at reasonable cost to you our valued customers.


    Of course we are always listening to our customer’s feedback and learning new ways to possibly make our products better. Hopefully this information will help everyone understand that Fourtitude R/C tanks are not just something that we just decided to slap together and sell. The development process has taken over a year with hundreds of hours test flying to get the product you see today. Thanks for the tremendous response about Fourtitude R/C and we hope to see you at a fly in sometime soon!

© Fourtitude R/C LLC 2017