What a view huh...

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In order:

Good picture. 

You've done a sufficient job of tacking the tubes down -- they don't need to be married to the tank wall, just nailed down at the ends so they don't vibrate all over.

AFAIK that's the correct way to arrange the uniflow and pick-up tubes, at least mostly.

The only two problems I see (and there's a lot of people who know more about this than me) are that the may be too close to the pickup, and it is a bit low (with respect to the installed orientation, not outside-down as you have it in the picture).

Putting the uniflow too close to the pickup gives you a tank that picks up bubbles from the uniflow.  I the rule of thumb I've heard here is 1/2" -- but see my disclaimer about lots of folks knowing more than me.  The further away the uniflow is the sooner it stops uni-flowing, but the less chance you have of getting bubbles.  Given that your symptoms in prior posts sound like bubbles -- you may want to fix that.

As for vertical position, the whole point of the uniflow is that it makes the tank act like the vent is right at that uniflow outlet position -- you've got the uniflow taked down about 1/8" low, which will make the tank act like it's 1/8" lower than if the uniflow was centered.  Having the uniflow not be at center isn't a bad thing in itself -- if you've shimmed a tank to its limit and can't move it any more, you can reset the tube inside and get some more wiggle room.  I have a tank in a plane now with the uniflow almost at the bottom edge of the tank for just that reason.

Either a propane torch or a big soldering iron will work.  I find a torch easier -- but also a lot easier to burn the tin off of the tank.  Move quick and keep trying to pop the lid -- it should all come off at once, and then you know you're done (except for groveling around on your floor looking for where it landed).  Someone (Brett Buck, I think) uses a hot plate, which seems like a really good idea to me.  You CAN get a tank end off with a big iron, but it's fussy, and you risk bending the thing if you get impatient.

What is AFAIK anywho?  I didn't build the tank, it's just a popped open Brodak tank.  I do get plenty of air bubbles while running. In fact all 4 uniflow tanks from Brodaks have all given me plently of air bubbles. Hopefully someone can give me a good distance away that will give me the best results. I took the 4.5 oz off for a 5oz on both my Tanagers. 4.5 just seemed like it might  cut it close at other locations. This 5 oz tank won't cut off clean at the end like the 4.5 did. I've got the back of the tank kicked out the same as the 4.5oz tank. However I was hoping to see a reason for that after opening it up butt nothing is jumping out at me.

How far away did you make your uni on your soup can tank?

Are you using a fuel filter?   I know with out one I get bubbles to the spray bar.   I also bevel the ends of the tubing inside the tank.  I do make sure there is at least 3/8ths of an inch between the ends of the tubes.   Yes soldering to the side of the tank solves a lot of minor problems.   But, having the Uni-flo really centered has not been a problem in my case as long as it is soldered to the pick up tube.

AFAIK = as far as I know

Thanks!  I'll probably forget that the next time I see it.

Either a propane torch or a big soldering iron will work.  I find a torch easier -- but also a lot easier to burn the tin off of the tank.  Move quick and keep trying to pop the lid

What do you mean by burn the tin off? Is tin a coating? I assume if it turns blackish and purple its too much propane heat.

What do you mean by burn the tin off? Is tin a coating? I assume if it turns blackish and purple its too much propane heat.

The material the tanks are made of is tin-plated steel, which is what makes them so very easy to solder.  That purpleish-gray color means you've burnt it, and you can't solder to that bit (and, it'll probably rust quicker).

Ooooops I cooked one of the 4.5oz tanks then... yes I'm a impatient individual.

   Don't use a torch, ever, for tanks. To remove the back, use the burner on the stove. It works particularly good on an electric range, but OK on a gas range with it set very low.

     Brett

Do you put something between the electric range and tank or just slap the back of the tank on top of the range?

Your opinion on the distance of the pickup and uni line?

   Just put it on the electric burner.
 
    Mine are absolutely as close together as they can get, and I never get bubbles. My tanks are tapered, so put the uniflow vent right at the peak and about 1/4" from the rear, then put the fuel pickup line on top of it, with a crook in the end to get it absolutely in the corner. It's about 3/16", more or less. I do have the underside of the pickup line to hypothetically block any flow of bubbles toward the pickup, but it's not like there is a torrent of fuel rushing out through pickup.

    If the tank is not tapered, you can put the uniflow vent anywhere along the length of the tank. I think Paul figured out that it was best with the vent about halfway from the front to the back, so, 3" from the back of the tank on a 6" long tank.

     Brett

If your house comes equipped with a wife this may not work.

Just sayin'...

Ah yes,  forgiveness vs permission....the eternal household struggle.  Permission checks are to be considered the oppressive check to the creative. 

   Just put it on the electric burner.
 
    Mine are absolutely as close together as they can get, and I never get bubbles. My tanks are tapered, so put the uniflow vent right at the peak and about 1/4" from the rear, then put the fuel pickup line on top of it, with a crook in the end to get it absolutely in the corner. It's about 3/16", more or less. I do have the underside of the pickup line to hypothetically block any flow of bubbles toward the pickup, but it's not like there is a torrent of fuel rushing out through pickup.

    If the tank is not tapered, you can put the uniflow vent anywhere along the length of the tank. I think Paul figured out that it was best with the vent about halfway from the front to the back, so, 3" from the back of the tank on a 6" long tank.

     Brett

I guess you don't use muffler pressure on your uniflow line?

Chris

My most effective soldering tool for tanks is my dual heat 250/325 Watt Weller gun with a broad tip. I can't do anything but botch it with a torch. And I'm disappointed to find that my new Butane soldering iron with a wide tip has not enough horsepower to do the job. I was unpleasantly surprised, but the Weller does the job with ease, instantly flowing solder where you want it.
Rusty

I have a Weller too but I can't remember the watt.

Chris

If the crappy runs with this tank are on the engine with the extra large venturi,  then that's probably the reason,  not the tank.
The larger the venturi, the less fuel suction the engine has, especially if you are trying to run it at lowered control line rpm's. If you have good fuel draw,  you won't need muffler pressure. Imo.
In my opinion that is.
Is this that same fp40 with the large venturi and small os needle valve?

You changed your name???

No, they are 2 tanagers with LA46's. I've got the mesh over the venturis currently and it does help.  Just sucks a lot of air bubbles.

Chris

You changed your name???

Chris

Sort of,  but not really. This website requires registration with a true name. But since my nick name has been "target" since 1983, and i have to stop myself from signing posts that way,  i figured I'd just give in and make the screen name switch for my own comfort.
I hope you get your engines running smoothly.

Get yourself a balancer from Tower or local hobby shop and learn to use it.   Yes the ends of the tubes inside the tank are beveled on my tanks may be 45 degrees maybe not.   But the uni-flo is ahead of the pickup tube.   I have had filters that did leak until I took pliers to them to tighten them.  Also check your fuel line as I had a line give me fits until my son replaced it.  There are so many things that could be the problem, wish I was there to see it in person.  Cause bad engine runs will not help flying better,  don't ask me how I know.

I know intuitively this is very bad advice but just my opinion...

I tried to heed the advice of so many on these sites ---that always recommended ---OPENING every new tank to fix and secure...or even replace brass tube with copper

I got a few tanks from Brodak and some from RSM, the GRW brand, and a few Hayes or Sullivan type plastic clunk tanks...this post is about all hard tanks

On the advice I shook the hell out of the hard tanks and the RSM GRW brand did NOT rattle....so I used them as delivered....so far zero problems

Both the Brodak Tanks rattled... trying to relearn, I mangled one of them, learned from my mistakes, so the second Brodak tank repair, went OK, and is in use without problem

I really hate to bad mouth Brodak and all John does, but some few of the products are inferior and I find myself always looking for alternative sources

I know this may sound petty...but just two examples

Tom Morris control parts vs Brodak
RSM GRW tanks vs Brodak

in each case there is basically no price difference...but quite a bit of product quality difference

Grain of salt worthless observation.... I am a sport flyer

IMO if I were a serious about this,  I would get the metal bending gear from Lee or MBS and good material from dozens of places and make my own tanks

One reason for this seemingly negative post is....

We are well over 75 years away from the pioneers of model airplane flight with fuel engines

I would like to think the STATE of the ART for design, and best practices for construction, was achieved sometime in the 40's ~ 50's and perhaps some leap in thinking (like Uniflo) a bit later

Basically, it seems to me---- I SHOULD be able to (for a fair price) to BUY a Perfect (PUN) tank ----that does not require me to rebuild from the get go

Get yourself a balancer from Tower or local hobby shop and learn to use it.   Yes the ends of the tubes inside the tank are beveled on my tanks may be 45 degrees maybe not.   But the uni-flo is ahead of the pickup tube.   I have had filters that did leak until I took pliers to them to tighten them.  Also check your fuel line as I had a line give me fits until my son replaced it.  There are so many things that could be the problem, wish I was there to see it in person.  Cause bad engine runs will not help flying better,  don't ask me how I know.

I have 2 Durbo wheel balancers and one top flite magnetic balancer. Personally I think both of them are pieces off S***. The cones are not true on all three of them to make me feel happy about them.  And the wheels on the dubro balancers seem to hang up from dirt and dust. Does anyone make a good one besides these mass produced ones?

  The fuel flow that is about 2/3 ounce a minute?   I am very highly skeptical that is your problem, given that I have been running somewhere around 1/8" spacing for the last 20 years with no problem, with 50% more flow rate.

     Brett

If I understand you correctly you are using 10-15oz for a 5 minute pattern of you're using 50% more than me??

Chris;

Have you tired any of your LA46's on the Primary Force yet with the tank that is already on it?
Carl

Hi Guys,
Old guy and kinda new to the board.

There's a lot of information in this thread and I'm not sure if this was mentioned about how the uniflow makes for a more even run. Just something I heard or came up with, can't remember.

Without uniflow and muffler pressure, centrifugal forces and the weight of the fuel decreasing slowly reduces the pressure at the fuel pick up in the tank.
Since the venturi vacuum doesn't change, the reducing fuel flow pressure leans out the engine toward the end of the tank.
This we all have experienced.

Muffler pressure adds a constant pressure throughout the tank which helps a lot but we still experience a slight leaning out toward the end.

I don't know who came up with Uniflow Tanks theory but it adds another constant pressure right near the pickup. It does this using bubbles to stir the fuel at a constant rate. The bubbles coming in from the muffler raises the tank pressure and and stirring causes a slight constant low pressure at the fuel pickup. These two constant forces helps to negate the pressure differential problem caused by previous mentioned centrifugal and the decreasing weight of the fuel.

Bubbles too close to the pickup is a bad thing, too far and the stirring doesn't have a beneficial effect.
Without Muffler pressure the uniflow doesn't work as good, if anything it creates its own problem due to the air entering the tank has to push through all that fuel at the bottom of the tank before the bubbles do their job.

Thank You Mr. Uniflow!

If you have bubbles in your fuel line to the engine, it can be caused by a hole in the fuel tubing or filter, hole in the brass pickup tube in the tank or the tank is mounted too solid to the vibrating wood. Bottle tanks absorb some vibration but I have yet to see one working well as a uniflow tank.

Helpful tips:
If your flight leans out badly, replace your muffler pressure line, it doesn't last forever.

Don't adjust your engine speed until fuel has been pushed out of your pressure line, this line gets filled by fueling your tank and the tubing is usually above the center of the tank which gives a rich start and leans out badly after it takes off.

Need to work on my smoothie tomorrow.
Al T.

Chris ,I'm no expert on this topic but would like to weigh in. I too have had some problems with Brodak tanks (not all of them). Eventhough the tanks are not great I will continue to support John Brodak in anyway I can. Without his efforts, control line as we know it, may have become extinct years ago.

Regarding tanks in general,when given a choice....I much prefer plastic clunk tanks. For many reasons:
(1) There are so many sizes and shapes that we can use.
(2) They are serviceable,and you don't have to worry about rust or corrosion
(3) They are "tunable" by simply repositioning the vents and feed lines

I have found only two "negatives"
(1) Sometimes you have to redesign a tank area to fit them as most plans show 1" high tanks
(2) At the end of your run they have a tendency to lean out even with uniflo on muffler pressure.

I don't mind a little leaning out so much because you're in the overhead 8 and cloverleaf which require power. Also the leaning out tells you you're running out of fuel.

Again I'm not an expert on this,just some of my observations. Now get that metal tank sorted out!...PhillySkip

Chris ,I'm no expert on this topic but would like to weigh in. I too have had some problems with Brodak tanks (not all of them). Eventhough the tanks are not great I will continue to support John Brodak in anyway I can. Without his efforts, control line as we know it, may have become extinct years ago.

Regarding tanks in general,when given a choice....I much prefer plastic clunk tanks. For many reasons:
(1) There are so many sizes and shapes that we can use.
(2) They are serviceable,and you don't have to worry about rust or corrosion
(3) They are "tunable" by simply repositioning the vents and feed lines

I have found only two "negatives"
(1) Sometimes you have to redesign a tank area to fit them as most plans show 1" high tanks
(2) At the end of your run they have a tendency to lean out even with uniflo on muffler pressure.

I don't mind a little leaning out so much because you're in the overhead 8 and cloverleaf which require power. Also the leaning out tells you you're running out of fuel.

Again I'm not an expert on this,just some of my observations. Now get that metal tank sorted out!...PhillySkip

I find plumbing them pretty frustrating, but then again I'm sure I go at it all wrong. I made one last year that involved shrink tubing and soldering a wire with a loop. I think it's in a bag with other failed tanks
 I talked to Dan about making one uniflow, when I fall flat on my face with the metal tanks ill probably give them a shot. If I can remember how Dan told me.

I guess you have to go with a big 6oz clunk if you are using 4.5-5oz? What are the best ways to attach a clunk tank to a profile?

Chris

Chris, I feel your frustration. It's probably because everybody's Armorall bottles are 25 years old and an older formula. As is my Son-of-a-Gun, same stuff back then, 38 years old. I think I got it when I bought my first new car, a '79 Camaro Rally Sport, sparkly 2-tone blue, stripes and all. And it still works for me. I take the cap off the gallon and give it a PSHHHHT into the empty cap, flip it over and screw it back on and can't make it foam for nuthin'. But I hear the Armoral is not the same today as it was years ago.

Have you still got the drawing I made of my Sullivan 6 oz. slant face clunker? They don't make a 5 oz. as far as I know.

Give me a call sometime. I'm not doing the Stunthangar show tonight, just puttering around in the shop.
Rusty

Chris, I feel your frustration. It's probably because everybody's Armorall bottles are 25 years old and an older formula. As is my Son-of-a-Gun, same stuff back then, 38 years old. I think I got it when I bought my first new car, a '79 Camaro Rally Sport, sparkly 2-tone blue, stripes and all. And it still works for me. I take the cap off the gallon and give it a PSHHHHT into the empty cap, flip it over and screw it back on and can't make it foam for nuthin'. But I hear the Armoral is not the same today as it was years ago.

Have you still got the drawing I made of my Sullivan 6 oz. slant face clunker? They don't make a 5 oz. as far as I know.

Give me a call sometime. I'm not doing the Stunthangar show tonight, just puttering around in the shop.
Rusty

It is rather frustrating. I thought about putting a ad on Craigslist for a 30yr old bottle of Armoral  but figured everyone would think I was nuts. Cherish that old bottle of Son-of-a-gun Rusty! To the right person its worth its weight in gold.

My hard drive stopped working hard and driving so I lost it a couple months ago

Battered but not beaten yet...
Chris

I use a plywood plate or a thin (1/32" -- whatever gauge that works out to) aluminum plate, bent into a shallow "U" and with lightening holes all over it.  Make mounting slots in the plate so you can easily adjust the tank height.  Hold the tank to the plate with zip ties.

Russel Shaffer uses Shoe Goo to glue his tanks to plywood plates, which works great for him.  I tried it, and it failed miserably -- but he only doe
Chris
s it with new, clean tanks, and I was trying it with an old one that I'd scrubbed with dishwasher detergent -- apparently that wasn't enough to get the castor out of the pores of the plastic.

I you really want the best fuel feed, mount the tank on the inboard side of the plane -- it's not as pretty in the air, but it seems to work slightly better.  See here for an example, or just look at the picture:

Those pictures I just posted is where I'm at right now. I probably should have used 4 screws to hold it on instead of two.

I tried mounting to the inboard  side last year with my Skyray after you gave me the idea.  I personally didn't like the setup, I had it screaming lean and when it got up it was dog rich.

Kewl

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