Author Topic: Round plastic tank setup? (Read 924 times)

Dennis Toth · « **on:** March 15, 2024, 12:43:35 PM »

For some time, I have been trying to get the round RC plastic tank to work. A fellow flier has used them with the double clunk uniflow setup, and it worked well. For me it was very inconsistent. I stopped trying and switched to a hard tin tank. It was also inconsistent at first then I moved the uniflow vent line to be on the inboard side of the fuse and it was solid as a rock. I was thinking about the old round tank and thinking the vent location may have been the problem. The thing I like with the plastic tank is it is light, easily replaceable and cheap. Anyone use these how did you set up the venting?

Best, DennisT

john e. holliday · « **Reply #1 on:** March 16, 2024, 11:19:51 AM »

As you discovered with your hard tank the uni flo needs to be in clean air. Make sure the pick up tube does not hang up. If you do a search on here you will find some of the set ups.

Ken Culbertson · « **Reply #2 on:** March 16, 2024, 12:58:02 PM »

Quote from: john e. holliday on March 16, 2024, 11:19:51 AM

As you discovered with your hard tank the uni flo needs to be in clean air. Make sure the pick up tube does not hang up. If you do a search on here you will find some of the set ups.

Mike Greb · « **Reply #3 on:** March 29, 2024, 09:47:39 AM »

This is the setup I use on my models, it is a hays tank set on the side using the filling vent as an uniflow vent. Unfortunately the hays tanks have been taken over by MEOCA and the 3 and 4 oz tanks have been out of stock for years.

Dan McEntee · « **Reply #4 on:** March 29, 2024, 01:30:46 PM »

A round tank really isn't any different than any other tank. Centrifugal force is going to push the fuel load the same as it always does. The fuel pick up tube goes at he apex of the tank, that is furthest outboard, Uniflow can be a solid tube or the double cluck some like. You can twist the cork to a certain extent to affect run upright or inverted but you may want to actually raise or lower the tank a bit.
Type at you later,
Dan McEntee

Dennis Toth · « **Reply #5 on:** March 29, 2024, 05:19:42 PM »

Dan,
I agree that the round tank should be just like any other tank. When I tried it I tried putting the vent line up in back of the engine. The thinking was it would put vent in a dead zone and eliminate the upwind/downwind pressure variations. This was wrong. What it did was causes all kinds of pressure fluctuations and the engine run was all over the place. It did the same thing when I switched to a hard tank also. When I moved the vent to the free airstream on the inboard side above the side fuse profile the engine was rock solid.

Best, DennisT

Dan McEntee · « **Reply #6 on:** March 29, 2024, 08:12:03 PM »

Quote from: Dennis Toth on March 29, 2024, 05:19:42 PM

Dan,
I agree that the round tank should be just like any other tank. When I tried it I tried putting the vent line up in back of the engine. The thinking was it would put vent in a dead zone and eliminate the upwind/downwind pressure variations. This was wrong. What it did was causes all kinds of pressure fluctuations and the engine run was all over the place. It did the same thing when I switched to a hard tank also. When I moved the vent to the free airstream on the inboard side above the side fuse profile the engine was rock solid.

Best, DennisT

Well, that was not a problem with the tank, it was how you executed the installation. You can deal with the up wind/downwind variation in the run with a simple restrictor in the vent tube. you might still get some variation because of airflow into the venturi also. That can depend on how the engine sits in the nose of the airplane, but you don't want to block off any airflow into the venturi or you get other problems.

Type at you later,
Dan McEntee

Steve Helmick · « **Reply #7 on:** April 02, 2024, 04:56:27 PM »

Not regarding a round plastic tank...because I don't know what tank he uses, plastic, metal, round, CF, whatever...but I was shocked to see that Bruce Perry's uniflow inlet is on the inboard side of the nose, but pointing straight DOWN. It works, but I don't know why. I have not tried it, because....

My solution is almost always muffler pressure. It solves the upwind/downwind rich/lean nonsense and also keeps the tiny seeds and bugs out of the tank and therefore, the fuel filter. It is NOT for somebody who tends to have mufflers get loose or
fall off. I do NOT recommend using a gasket under the muffler flange. And, Randy Smith doesn't recommend muffler pressure at all, so....

Steve

Dan McEntee · « **Reply #8 on:** April 03, 2024, 11:23:13 AM »

Quote from: Steve Helmick on April 02, 2024, 04:56:27 PM

Not regarding a round plastic tank...because I don't know what tank he uses, plastic, metal, round, CF, whatever...but I was shocked to see that Bruce Perry's uniflow inlet is on the inboard side of the nose, but pointing straight DOWN. It works, but I don't know why. I have not tried it, because....

My solution is almost always muffler pressure. It solves the upwind/downwind rich/lean nonsense and also keeps the tiny seeds and bugs out of the tank and therefore, the fuel filter. It is NOT for somebody who tends to have mufflers get loose or
fall off. I do NOT recommend using a gasket under the muffler flange. And, Randy Smith doesn't recommend muffler pressure at all, so.... Steve

Pointing down just makes it a vent with no pressure. Still uniflow, but no increase in air flow from prop blast or forward motion. I just posted a response on another thread about my results from some flight testing and for the first time using a restrictor on the uniflow vent that faces the front. My only question about pointing down is, would you tend to get a slight vacuum produced from the "chimney effect" of air flow past the end of the vent? Maybe nod, or so little that it has no effect, but still give a very even venting to the tank? I all my flying in all my life I have never had the need nor the idea that I needed to restrict the uniflow vent, but on one specific model it made a significant difference. it will make me take a look at all the other profiles I have set up the same way.

Type at you later,
Dan McEntee

Dennis Toth · « **Reply #9 on:** April 04, 2024, 06:51:36 AM »

I understand the idea behind pointing the uniflow vent downward but Dan brings up a good point. Since it is on the inboard side of the fuse it might be seeing a stable pressure but it could be hit or miss depending on weather conditions. I tried to put the uniflow vent in back of the engine in what I thought would be a dead zone on my El Diablo. This was hit or miss on the engine run, when I remembered an old GSCB winter forum where a guy explain about putting the vents on the inboard side of the fuse in the free airstream I move the vent and just like magic solid engine run set anyplace you wanted. So my experience is keep the vent on the inboard fuse side and up in the free airstream.

Best, DennisT

Ken Culbertson · « **Reply #10 on:** April 04, 2024, 10:12:03 AM »

Back in the day when I flew IC I had many an encounter with uniflow tanks that just didn't flow uniformly. My best results always ended up coming from the most popular tanks of the day. Two vents on the inboard front. One top to bottom, the other bottom to top. Both bent to face the front on the inboard side. Fill through the top then maybe cap off the bottom vent if you were so inclined. Simple and it just worked. You might ask how we shimmed the tank height. Simple we didn't. How things have changed.

Ken

Dan McEntee · « **Reply #11 on:** April 04, 2024, 02:35:17 PM »

Quote from: Ken Culbertson on April 04, 2024, 10:12:03 AM

Back in the day when I flew IC I had many an encounter with uniflow tanks that just didn't flow uniformly. My best results always ended up coming from the most popular tanks of the day. Two vents on the inboard front. One top to bottom, the other bottom to top. Both bent to face the front on the inboard side. Fill through the top then maybe cap off the bottom vent if you were so inclined. Simple and it just worked. You might ask how we shimmed the tank height. Simple we didn't. How things have changed.

Ken

You just described a standard vented tank. It will cause an engine to speed up as the fuel load goes down. Muffler pressure can help a little bit. I advise newcomers using this type of tank to cap off over flow tube, and to cut a 45 degree slice on one end of a short piece of fuel line and put that on the fill tube with the angle cut facing forward. The keeps a positive pressure in the tank and eliminates any chimney effect from air flow over the ends of the tubes. You gotta let physics work for you.
Type at you later,
Dan McEntee

Ken Culbertson · « **Reply #12 on:** April 04, 2024, 04:09:02 PM »

Quote from: Dan McEntee on April 04, 2024, 02:35:17 PM

You just described a standard vented tank.

That was my point. It was standard for a reason - it worked for the limited reliability we expected back then. The speeding up at the end was welcomed. Hourglass, Overhead 8, Clover. In some ways it was better than the same speed start to finish we worship today. Just my opinion, and I could be wrong.

Caping the overflow and putting the dog ear on the other works. I bent both into the wind. When the evil mufflers came along I capped the fill tube (top) and hooked muffler pressure up to the overflow (bottom).

ken

Dennis Toth · « **Reply #13 on:** April 05, 2024, 07:41:50 AM »

The conventional venting works fine and as Dan and Ken said it will tend to speed up through the flight particularly if you are running a 4-2-4 run setup. There is a way to control the amount of change by using a tall thin tank, so the fuel head changes less. Other way is to move the tank inward on a profile (putting part of the tank between the mounts) this also can reduce the amount of change some. The 2-2-2 setups don't seem to be affected as much (OS FP/LA 20, 25 Brett setup) nor do 4 Strokes.

If you use the round tank the in-tank vent line would go to the inboard middle of the tank with the external vent end needs to be located at least 3/8" above the top of the tank (in the free airstream above the fuse profile best on the inboard side of the fuse). This works fine for upright engines or if inverted starting them from the inverted position. If you like to flip the ship over to start you need to keep the nose pointed up 20 - 30 degrees ish to keep the fuel from running out the vent, just like you would with a uniflow tank.

Best, DennisT

Author Topic: Round plastic tank setup? (Read 924 times)

Dennis Toth

Round plastic tank setup?

john e. holliday

Re: Round plastic tank setup?

Ken Culbertson

Re: Round plastic tank setup?

Mike Greb

Re: Round plastic tank setup?

Dan McEntee

Re: Round plastic tank setup?

Dennis Toth

Re: Round plastic tank setup?

Dan McEntee

Re: Round plastic tank setup?

Steve Helmick

Re: Round plastic tank setup?

Dan McEntee

Re: Round plastic tank setup?

Dennis Toth

Re: Round plastic tank setup?

Ken Culbertson

Re: Round plastic tank setup?

Dan McEntee

Re: Round plastic tank setup?

Ken Culbertson

Re: Round plastic tank setup?

Dennis Toth

Re: Round plastic tank setup?