Hi All

How does the Standard Vent Fuel Tank compare with the Wedge Fuel Tank when it comes to fuel delivery while flying the full Stunt Pattern?

Hi All

How does the Standard Vent Fuel Tank compare with the Wedge Fuel Tank when it comes to fuel delivery while flying the full Stunt Pattern?

   The top one is the old Fox "Profile" tank, and the bottom is a standard Veco T21 series, intended for conventional fuselages. I am not sure where you are getting the descriptions.

    The profile tank it intended to fit in a short space on many profile models, without incurring the low feed pressure issue discussed in the chicken-hopper tank thread.  The original Fox version had a baffle across the "doghouse" to isolate the pointy "top" (in your picture) section from the rest of the tank, since the fuel tends to slosh inside the bigger section. The makes it like most if not all commercial chicken hopper tanks, in that the fuel is drawn from a small tank. I don't know if that actually worked as intended, nor do I know that the current-manufacture tanks actually have that baffle. I doubt that it matters.

    The Veco T-21 is sort of the starting point for almost all conventional models, variants of it have been made for 60+ years. It's 1" thick which not coincidentally lines up with a Fox 35 needle valve when you mount them to the same flat surface. It also is about 1 ounce per inch of length, so a 4 ounce tank it about 4" long, which is how they sold them (in 1" increments). That tends to be a problem for fitting onto profiles, because there's not enough length, and the pickup tube points right at the head, sucking up another inch. It's also 2" wide, which is a little too far to pull the fuel "up" to the spraybar for some engines (like the 20FP). In an inverted mount, the pickup comes out right next to the engine, so you can push it all the way up to the back of the engine without any real issues.

   I have seen precious little success with the Fox profile tank, but I don't know if that is because it's on a profile from the days of baffle-piston engines like the Fox 35, which effectively won't work properly on a profile without modification (that was not discovered until about 1995!), or there is something wrong with it otherwise. I suspect the former, and I have made tanks that are not dissimilar myself that worked fine.

     The Veco T21 style or something like it is almost universal for full-fuse stunt planes. I think the wedge angle is a bit too shallow for modern engines and airplane, with the superior cornering, because it tends to become uncovered at the end of the tank, making you carry extra fuel just to avoid it going lean in the overheads and 4-leaf (and sometimes even the hourglass). About 15 degrees steeper, and this issue goes away. You can also take the same sort of tank form, and make it thicker (like mine, which is 1 1/4") and wider (2 3/16" in the back) to fit a wider fuselage. Mine are also tapered from front to back, 1 7/8" in the front and 2 3/16 in rear, all of which permits about 7.6 ounces of fuel in a 6" space.

      If those two were my only two choices I would probably use the Fox profile tank on a profile, and a Veco tank on a full-fuse airplane, just like they intended. On profiles, I have had better luck with RC clunk tanks (like the Sullivan SS-4) with the wide side up against the fuselage.

     Brett

Hello
A problem with the plastic clunk tanks is the ability to fit a large enough tank into the small space on models like the Ringmaster, Shoestring, Flite Streak and Peacemaker and using a 'wide' metal tank gives all the problem of fuel draw . The Fox style profile tanks helped solve the space problem. It would be great if you could re-mould a plastic tank into the correct shape easily!
Combat models and hard tanks are difficult as squashing them out wide gives the same fuel draw issues. Perhaps it would work well if you used two centre ribs with a plastic tank mounted flat in between the two ribs along with the bellcrank. Perhaps its time to try this out?

Regards Gerald