AS is usually the way with me, I like to research things before I commit. In the instance of fuel tanks however, I'm thinking I might need to be committed.

I have a chipmunk that I'm ready to start assembling, and I've been thinking about tanks. As it is I have two choices, a brodak uniflow, or a small rc clunk (oval shaped) tank.

Obviously the brodak is already plumbed for uniflow, but I might have to make some changes to it, basically I want the overflow coming out the bottom of the tank, rather than out of the front, but apart from that it's a fixed, known quanity.

AS regards the RC tank, I've found multiple plumbing setups, all claiming to be the bee's knees for a stunt run.

First is the typical single clunk, and uniflow pipe to the outboard side of the tank, and rpm change upright/inverted is set by moving the uniflow pipe in the tank, rather than shimming the tank, sounds reasonable enough.

second is the "siamese clunk" (nicked from Al Rabe's mustunt on stuka stunt) where both fuel pickup and uniflow vent are connected together and float around as one. Wouldn't this make it impossible to adjust for rpm change inverted to upright? Does it even change?

Finally I found a post from Steve Moon that says he runs the vent to the forward inside corner of the tank and the pickup is exposed pretty much on launch. I take it this system is used with muffler pressure, and the resultant pressure head change is so mild that no rpm increase is noticable?

Which would be best for a LA 46 on muffler pressure?

Whats your shutoff like? Where's your vent in the tank on the non-uniflow?

"A Du-Bro rectangular tank set up for "hard" uniflow (not siamese clunk) has worked well, too."

That's also what's in my "Eagle" (.46VF with Nelson AAC and Randy Aero pipe). Runs good until is almost dry. It jumps about 1k+ rpm and starts hauling butt. Runs hard for two or three laps...a warning you can't possibly ignore.

One thing to remember is that if you get burping for multiple laps...you probably need to move your leadouts forward. It's yawing in-out-in-out, as it's running dry. Shimming out the aft end of the tank may also be required, but early in the trimming process, it might just be a tipoff on the leadout location being too far aft.   Steve

I have been running a uniflow clunk(not siamese) on my ARC Cardial with the uniflow halfway down the outboard side of the tank. I put a 90 deg. bend on the outside uniflow tube so it would be easy to raise and lower the height of the inside part easier...without un rubber banding the tank to get to the outside tube with pliers. Problem is the uniflow height is almost at 1/2" above the spraybar and it still goes rich on inverted. WORST case it could be as it is going rich at the topp of the verts and hourglass. I have removed the clunk and put a brodak 4 oz uniflow like you are talking albout. the only reason I didn't in the first palce is I thought the LA 46 would use more fuel but 4 ozs is getting me through the pattern with 3 or 4 laps to spare. Anybody know why with the uniflow that high above the bar (upright) it still goes rich on inverted? This set up worked great for a month and then slowly started giving me crap. As soon as the wind stops blowing I will give the metal tank a go and see...still on the fence aobut tanks just like you are...

That's why I put a bend on the exposed part of the uniflow tube where the tubing hooks up. I just bent it at 90 deg paralell to the centerline so you just grab it with your fingers and raise or lower by twisting up or down. I too have crushed the tube with pliers but the bend fixed that...then the tubing could either go to the muffler for pressure or tuck behind the engine or to a bent tube thru the fuse into clean air. Maybe i should just try shimming the whole tank up or down though...hell...i'll try anyhting once