News:
2018----><---- T Shirt




  • October 22, 2018, 09:25:41 AM

Login with username, password and session length

Author Topic: Round plastic tank vs rectangle hard tin tank  (Read 1594 times)

Offline Dennis Toth

  • 2014 Supporters
  • Trade Count: (0)
  • Admiral
  • *
  • Posts: 2088
Round plastic tank vs rectangle hard tin tank
« on: November 25, 2017, 11:38:49 AM »
Guys,
Been doing some work with tanks and wanted to get some thoughts that others have with round tanks vs standard rectangle tanks. I like the plastic as its lighter than the tin tank, easy to clean and replace. I set it up as uniflow. One thing I found with the round tank is the engine run goes slight leaning as I did consecutive loops (In the OTS pattern you do 5) particularly as it gets to the 4th and 5th loops. I'm thinking that I might try adding muffler pressure. Anyone have experience with the round tanks?

Best,    DennisT


Offline Dennis Toth

  • 2014 Supporters
  • Trade Count: (0)
  • Admiral
  • *
  • Posts: 2088
Re: Round plastic tank vs rectangle hard tin tank
« Reply #1 on: November 29, 2017, 07:22:53 AM »
Well decided to adjust the plumbing for the two free clunk as it seemed that they were hitting as they flopped from top to bottom. I shortened the uniflow vent 1/8" both now moved freely. Test flew the ship and it caused a very lean run, this is not good.

 I then made up a new combined pickup/vent with the vent soldered to the pickup clunk. I set the vent 3/16" from the end of the pickup. I hooked it up so that the vent is toward the inboard of the tank with the pickup about 3/16" from the back (I think this is the way most people are setting these up). I used the thin walled tubing for the vent and regular medium silicon for the pickup. They flop free with no twisting. Need to test fly. I real like the round tank and hope it will give a steady run. Anyone running this type of tank set up?

Best,    DennisT

Offline Avaiojet

  • 2018 Supporter
  • Trade Count: (0)
  • Admiral
  • *
  • Posts: 6527
Re: Round plastic tank vs rectangle hard tin tank
« Reply #2 on: November 29, 2017, 08:15:12 AM »
Dennis,

Someone put up a diagram for exactly what you are doing. You might be able to find it or someone might know where it is.

Good luck.

Charles
Trump Derangement Syndrome. TDS

Avaiojet Derangement Syndrome. ADS

Please visit my updated Website! www.cfcgraphics.com

If you're Trolled, you know you're doing something right.

Alpha Mike Foxtrot.

Owner of CFC Graphics. "Model Airplane Graphics from a Model Airplane Builder."

"No one has ever made a difference by being like everyone else."

Marcus Cordeiro, The "Mark of Excellence," you will not be forgotten.

I look at the Forum as a place to contribute and make friends, some view it as a Realm where they could be King.

"Ya gotta love it when a plane comes together."

Proverb 11.9  "With his mouth the Godless destroys his neighbor..."

"Perhaps the greatest challenge in modeling is to build a competitive control line stunter that looks like a real airplane." David McCellan, 1980.

Online Dane Martin

  • 2017
  • Trade Count: (0)
  • Admiral
  • *
  • Posts: 2277
  • heli pilot BHOR
Re: Round plastic tank vs rectangle hard tin tank
« Reply #3 on: November 29, 2017, 09:17:33 AM »
Dennis, I did basically the same thing on my RM1000. I did it a little more "temporary" than you. I ran the vent line down along side the pick up line, cut it off about 1/4 inch back from the clunk and put a plastic  tube in the vent line. Then I used those little stainless wire ties to lash them together. The plastic tube was just to keep the vent line from crushing. I used some fuel line from my F2D equipment for the clunk line and vent line. It's extremely flexible.

Online Larry Fruits

  • 2018 Supporter
  • Trade Count: (0)
  • Commander
  • *
  • Posts: 204
Re: Round plastic tank vs rectangle hard tin tank
« Reply #4 on: November 29, 2017, 06:03:48 PM »
 I have a friend that has used round plastic tanks for years without any problems. He plumbs them to normal uniflow standards and mounts them similar to the rectangular plastic tanks. They work fine.

Good luck and enjoy;
 Larry 

Offline Skip Chernoff

  • 2018 Supporter
  • Trade Count: (0)
  • Admiral
  • *
  • Posts: 939
Re: Round plastic tank vs rectangle hard tin tank
« Reply #5 on: November 29, 2017, 07:23:48 PM »
I've used and have been using plastic tanks both round and rectangle. I always put them on muffler pressure. I'm no expert on this but they seem to work well for me. I also like that you can take them apart clean and service them. PhillySkip

Offline Perry Rose

  • 2015
  • Trade Count: (0)
  • Captain
  • *
  • Posts: 812
Re: Round plastic tank vs rectangle hard tin tank
« Reply #6 on: November 30, 2017, 05:17:47 AM »
Use separate lines for the pick up and uni flow and vent. Pressure is better in the wind it eliminates the lean out on down wind. The Du-Bro 4 ounce rectangle tank holds 4.5 ounces.
 http://perrystoys.blogspot.com/  There is a photo at this link showing what I mean. Titled "Plumbers but".
« Last Edit: November 30, 2017, 06:24:29 AM by Perry Rose »
I wouldn't take her to a dog fight even if she had a chance to win.

Offline Dennis Toth

  • 2014 Supporters
  • Trade Count: (0)
  • Admiral
  • *
  • Posts: 2088
Re: Round plastic tank vs rectangle hard tin tank
« Reply #7 on: December 01, 2017, 11:35:41 AM »
Seems people have plumbed this in several different ways and all seem to work. My only problem with this tank was that at the end of the flight when the uniflow uncovers it would go learner than with the hard tank, pushing the engine hard. Not sure if this was because the clunk would pickup the very last drops of fuel better than the hard tank or if rear of the tank was not kicked out enough. The plastic tanks have a rounded shape that could flow a little different that the flat surface of the hard tank. I have the rear kick out the same amount as I had on the hard tank so will see how this works. I have not had good performance when I used a hard tube for the uniflow in either the round tanks or the rectangular ones. I think it was because the fuel can move to far from center and uncover the U vent in the last few maneuvers.

Best,    DennisT

Online Tim Wescott

  • 2016 supporter
  • Trade Count: (0)
  • Admiral
  • *
  • Posts: 10473
Re: Round plastic tank vs rectangle hard tin tank
« Reply #8 on: December 02, 2017, 01:35:33 PM »
Uniflows are uniflow because the vent does not move.  A vent that's a weight on a floppy bit of tubing isn't a uniflow, particularly not on a round tank.  I'd use a rigid tube for the uniflow -- or I'd use muffler pressure, which seems to work great on all of the high-RPM Schnurle-ported engines that I fly with (i.e., OS LA, FP, Magnums and Tower 40).
AMA 64232

The problem with electric is that once you get the smoke generator and sound system installed, the plane is too heavy.

Offline Dennis Toth

  • 2014 Supporters
  • Trade Count: (0)
  • Admiral
  • *
  • Posts: 2088
Re: Round plastic tank vs rectangle hard tin tank
« Reply #9 on: December 03, 2017, 11:09:25 AM »
Tim,
I understand your position on the uniflow position and vent style. Several other and myself define uniflow as the vent being submerged in fuel along with the pickup line and that the pressure reference is the pickup line relative to the submerged vent line. With the flopping style the upright/inverted lap times are tuned by raising/lowering the whole tank. The hard tube method seems to works better in tanks that are thin (1" ish) in depth the flopping style in deep tanks (and round tanks) where the fuel in can move away from the vent in hard turning maneuvers (like the OTS 5 consecutive loops). I also think that the size of the pickup tubing and the routing (number and tightness of bends) has an impact on fuel draw and subsequent engine run. I am working on redoing the tubing in my current tank to have softer bends and a larger diameter to reduce restrictions in the line. Pressure into these tank through the uniflow vent seems to work again because of the pressure reference point to the pickup line (even crankcase pressure seem to work the same way).  At this point I am really trying to get the round plastic tank to work as it is simple, light and fits my ship nicely and allows the tank to have the rear kicked out just like the hard tank.

Best,   DennisT

Offline Dick Tyndall

  • Trade Count: (0)
  • Ensign
  • **
  • Posts: 27
Re: Round plastic tank vs rectangle hard tin tank
« Reply #10 on: December 03, 2017, 06:55:06 PM »
   Since the subject of these posts is about getting a steady and reliable engine run ( with different tank set ups ), I thought I would comment on what I did back in the early 1980's. I wanted to build a Slow Combat airplane that would do 100 MPH and maneuver well. I had a fairly good knowledge of making the engines go fast but was just guessing on a suction tank set up. I started with a Fox wedge style tank and cut out a section of the outer wedge to fit in a #2 Perfect tank as a "hopper". Using a sharp ice pick, holes were punched in the front and the rear of the perfect tank which were on the inside of the wedge of the Fox tank. This allowed fuel to get inside of the Perfect "hopper" tank. The fuel feed line to the engine exited the perfect tank in its usual position. A fill and overflow  were soldered into the upper front outside of the tank and when the tank was full, these were connected with a piece of fuel line. So now we need a vent. I always saw tanks with the vent facing into the slipstream, which I assume would add some pressure to forcing the fuel out of the tank and into the engine. Well, I did something different. I put the vent tube exiting the BACK of the tank. The other end went into the Perfect "hopper" tank. Right into the middle of the tank. The venturi restrictor that came with the Fox .36 MK IV engine was tapered with a tapered prop reamer. From the top to the spray bar hole and then from the bottom to the spray bar hole. This would maximize the suction with the fuel draw. After a few flights we ended up raising the tank 5/16" above the center line of the venturi to get steady runs ( and not go rich ) in the outside maneuvers and we had what we wanted: a steady run for the ENTIRE flight. When the tank was empty it did not give you ANY warning that you were running out of fuel; the engine just cut off. I am guessing with the tank vent coming out of the rear of the tank ( facing to the rear of the airplane ) that it was in a negative pressure area. I never had an airplane with as steady a run as this one had. And yes, it would go 98-100 MPH anytime you threw it in the air.


          Dick Tyndall

Offline Dennis Toth

  • 2014 Supporters
  • Trade Count: (0)
  • Admiral
  • *
  • Posts: 2088
Re: Round plastic tank vs rectangle hard tin tank
« Reply #11 on: December 10, 2017, 07:43:19 AM »
OK, I am working with the round 4oz uniflow set up with the vent solidly soldered to the clunk. When I built the clunk/vent unit I had flattened the vent tube to give better contact area for the solder joint. When soldering I had it in a jig (piece of 2x4 with a V notch cut in it) which allowed me to really heat the clunk and get a good joint. I the course of soldering I managed to fill the end of the vent tube. Once all cooled I drilled out the tube with a 1/16 drill. I had always thought that a small hole was the best for uniflow to keep up/wind down/wind run variations. However, could this be to small? I have been getting strange runs as the motor breaks very hard going into loops but come back after level flight resumed. Could the vent be too small?

Best,   DennisT

Offline Dick Tyndall

  • Trade Count: (0)
  • Ensign
  • **
  • Posts: 27
Re: Round plastic tank vs rectangle hard tin tank
« Reply #12 on: December 10, 2017, 11:16:00 AM »
Dennis,
    Did you ever think to try positioning the vent away from the slipstream ( facing to the rear )? Read my previous post above.  I don't pretend to know much about stunt tank set-ups but this one certainly worked for me.


                              Dick Tyndall

Offline john e. holliday

  • 2018 Supporter
  • Trade Count: (0)
  • Admiral
  • *
  • Posts: 19727
Re: Round plastic tank vs rectangle hard tin tank
« Reply #13 on: December 10, 2017, 08:14:51 PM »
Air moves much faster through holes than liquid.  Now about the rear facing vent, I had one on my Nobler that was not intended to be rear facing.   The old Fox would run like it was supposed to with the uni-flo but if it suddenly went rich I knew the screw had come out holding the vent tube on the inboard side of the fuse.  Tried setting the engine on the ground with the vent to the rear and it didn't work the same.   John Bender I flew with tried the uni-flo vent inside the fuselage right behind the engine and seemed to work the same no matter going into the wind or out of the wind.  HB~>
John E. "DOC" Holliday
10421 West 56th Terrace
Shawnee, KANSAS  66203
AMA 23530

Offline Dennis Toth

  • 2014 Supporters
  • Trade Count: (0)
  • Admiral
  • *
  • Posts: 2088
Re: Round plastic tank vs rectangle hard tin tank
« Reply #14 on: December 21, 2017, 01:56:49 PM »
For several weeks I have been working to get a consistent run, going from flat rich 2 cycle to over rich. At times when very rich I would force a loop and it would break lean and stay lean for several laps. When it ran on the rich 2 cycle I kept trying to open it a few clicks at a time without any real change, finally going open several turns before it changed at all. I have gone through the whole fuel and feed system on my EL D with the Fox 35. I changed the fuel from 27%  50/50 back to 28% 75c/25s oil. While going through the NVA I did feel a small bit of grit on the needle. All was cleaned and the round tank on uniflow muffler pressure installed (again). Off to the field. The engine had a soft compression feel which I did trace to the plug not being tight enough. Once started after the re-clean, it ran rich and would 4 -2 on the ground with nose up - nose down position of the ship. In the air it went off fairly rich (5.2 lap time on 60" C to C). A little soft on the lines but I was able to whip a little to go an inside loop. As it got nose up it broke lean but stayed lean until back to level flight then right back to the prior lap time. I did several loops this way and each time it did the same lean then back to rich. Problem is it should have gone back to rich at about the 2 - 3 o'clock position not at the bottom.

Question for the group - could the deep 1 3/4" diameter round tank depth be the issue as opposed to a normal 1" depth?

Best,    DennisT


Offline Dennis Toth

  • 2014 Supporters
  • Trade Count: (0)
  • Admiral
  • *
  • Posts: 2088
Re: Round plastic tank vs rectangle hard tin tank
« Reply #15 on: December 22, 2017, 01:30:36 PM »
Found a possible problem that could cause the erratic runs. I was going through the tank plumbing and found a split in the blue tubing connecting the muffler pressure/uniflow line. This could only be seen when pulling it to remove the line from the tank tubing. I changed out the blue to the pink.

I suspect that during tight maneuvers the tubing move just enough to opened to leak air and break the muffler pressure causing the engine to go lean, once back at normal level flight it seals and muffler pressure returns to normal. Seems the blue tubing may be sensitive to vibration that an cause it to split at any edge like the hard tubing on the tank. Hope this cures the run problems, I would really like to get this round plastic tank to work.

Best,    DennisT
« Last Edit: December 22, 2017, 03:14:15 PM by Dennis Toth »

Offline john e. holliday

  • 2018 Supporter
  • Trade Count: (0)
  • Admiral
  • *
  • Posts: 19727
Re: Round plastic tank vs rectangle hard tin tank
« Reply #16 on: December 23, 2017, 09:20:41 AM »
I've had that problem with the blue tubing.   So the first sign something is wrong with a plane/engine combo I change the blue stuff.
John E. "DOC" Holliday
10421 West 56th Terrace
Shawnee, KANSAS  66203
AMA 23530

Offline Dick Tyndall

  • Trade Count: (0)
  • Ensign
  • **
  • Posts: 27
Re: Round plastic tank vs rectangle hard tin tank
« Reply #17 on: December 23, 2017, 08:37:21 PM »
   Use the pink silicone tubing that Brodak sells. It's the same as the fuel tubing that Prather sold years ago.  Less likely to split. Many of us use it with the R/C Nitro boats because it holds up better under the vibration, stress, etc. Good stuff!


                             Dick Tyndall

Offline Dennis Toth

  • 2014 Supporters
  • Trade Count: (0)
  • Admiral
  • *
  • Posts: 2088
Re: Round plastic tank vs rectangle hard tin tank
« Reply #18 on: January 12, 2018, 07:27:42 PM »
Well after giving this a good college try I have decided the round tank didn't work well for my installation. Built a tin uniflow tank with a GMA pinch corner. This new tank worked well with no surging, nice solid run.

Best,   DennisT


Tags: