A word of caution regarding these metal tanks--Since GRW is no longer making them, I have no idea who is making them now. When I used GRW tanks, I never had a problem. Now, with a different manufacturer, I have had issues with clogged tanks.
I think the manufacturer is using corrosive flux. I had engine run problems and could not find anything wrong with the engine, filter, etc. so I decided to remove the back plate of the tank. The entire inside of the tank was corroded. The pick up line was clogged with corrosion debris. A few months later, I had the same problem with another tank. They were both so badly corroded inside that it was not worth trying to clean them up and put back into service.
So, if you use one of these tanks, and start having engine problems, check the tank for clogs due to corrosion. It took a while for the corrosion to accumulate so at first you might think all is OK. A few months later, or maybe even a year later, problems show up.
I have seen what Jim describes in many of these tanks. What I think the problem is, is the way they produce these. Flux is flux, and it's all corrosive, that's how it does it's job. It's an acid that cleans metal surfaces. I personally prefer Ruby Fluid flux. It just works better. most people use way too much, but if the joints fit properly, it's like Brylcreem, a little dab will do ya! Heat and capillary action will cause it to flow along the seam, and very little to none should get inside the tank. After water testing for leaks, you can flush the tank out with a little soapy water to flush any flux, then some alcohol or fuel to displace and absorb any water. With the manufacturer of these store bought tanks, I think the way they go about it is the issue. First, they form and assemble the main body of the tank with all tubes, and it's soldered. Then, I think they just dip the ends into a tub of flux and put on the end caps and solder those in place. They simply wipe off the outside with a rag, and don't flush the tanks at all. in a matter of days, the flux will start eating away at any scratched in the tin coating and attacking the steel underneath. Then the stalagmites of rust start forming. I have seen these tanks, brand new out f the package, have a rattle like there was something inside. Remove the rear end cap and the inside of the tank looked like a cave! I advise anyone that when you buy a new store bought tank of recent manufacture, tap the tank on a soft piece of wood a bit to see if there is anything growing inside that will break loose. If you hear something rattling, just send it back immediately without even opening the bag. They can't argue that the tank was tampered with that way. The people that make these tanks, hire unskilled people at minimum wage to assemble and solder these, I believe. I have seen this before from other manufacturers. Turn over rate is high and it's a constant struggle to achieve any consistent quality. It's the main reason I make a lot of my own tanks. I have a big collection of older, store bought tanks that I can modify with however I want the tube arrangement to be also and I copy some of these shapes and designs if I like how they work. A lot of these store bought tanks have issues with how and where the tubes are secured also, and I have even seen it in old Perfect tanks. I have had to fix and modify a lot of those also.
As far as uniflow location, the British and Europeans have been using uniflow long before it was discovered here. I have made tanks with the uniflow tube all over the place, as long as it's along the most outboard wall or corner of the tank, and they have worked like they should. I have seen old British plans that show the uniflow tube end all the way at the front of the tank. If you do not understand what someone is describing or referring to about how to plumb a tank, simply make one up and see how it works. With the plastic tanks available, it's quite easy and basic configurations of the tubes can cross over from plastic to metal tanks also. I use about half metal tanks and half plastic tanks, depending on the airplane and what I have at hand and the type of tank really doesn't matter. The only think I avoid is a wide wedge with the pick up tube all the way out at the furthest outboard part of the tank. Centrifugal force works against the fuel as it tries to get to the spray bar and will lean out an engine run once the airplane is airborne and up to speed. Speed flyers use the shimming of tanks for profile speed models outward to hel tune the needle setting and engine run. You can't fight physics, but you can work with it and use it when needed.
I hope everyone had a nice Thanksgiving!!
Type at you later,
Dan McEntee
Topic: Uniflow tube location (Read 1381 times)