Tank mounting questions

[Matthew Brown]

I've got three projects working and thinking about mounting the fuel tanks. A couple things have peaked my curiosity.
First, mounting the tank in my Oriental ARF. What is the preferred way to hold the tank in place? I considered gluing it in with a bed of silicone but thought I'd check here first.
Second question came up when looking at plans on a couple profiles. One has the tank deeply recessed in the fuse to the point the pickup is about the same centerline as the needle valve. The other plans show the tank mounted on same surface as engine lugs. Does the inward/outward position affect the running and needling of the engine? I know the height affects the mixture upright and inverted.

Thanks, Matt

[Tim Wescott]

I've got three projects working and thinking about mounting the fuel tanks. A couple things have peaked my curiosity.
First, mounting the tank in my Oriental ARF. What is the preferred way to hold the tank in place? I considered gluing it in with a bed of silicone but thought I'd check here first.
Second question came up when looking at plans on a couple profiles. One has the tank deeply recessed in the fuse to the point the pickup is about the same centerline as the needle valve. The other plans show the tank mounted on same surface as engine lugs. Does the inward/outward position affect the running and needling of the engine? I know the height affects the mixture upright and inverted.

Thanks, Matt

Hey Matt:

Russell Shaeffer comes up from Klamath Falls every year and shows me plastic fuel tanks that are glued onto wood using Shoo Goo.  He says it's 100% reliable.  I tried it once and the tank fell off after a flight.  I think it's because I started with a used tank, where he uses new ones.

For mounting, anything that gives a solid mount is good.  For a metal tank you can solder feet onto it and screw it to the fuselage.  For any tank you can use cup hooks and rubber bands (which melt fast), bands cut out of bicycle tubes (which melt slower), big metric O-rings, or 1/2-A silicone fuel tubing.  I make aluminum or plywood plates to allow for easy up & down adjustment and to "kick" the back out, then I use plastic cable ties.

The inboard/outboard mounting matters.  The less suction the engine has, the more it matters.  More inboard is better.  If you don't care about looks, mount the tank to the inboard side of the fuselage.

[Dan McEntee]

   Hi Matt;
   On a full fuselage model, the tank can be held in any old way, as long as it's solid. make provisions for easy removal for adjustments and service. You can wedge it in place with foam, balsa sticks tack glued between the sides, or even held in place with the cowling. Just make sure it's solid and level where it seats against the engine mounts.
   As for profiles, I think it can make a different how close the pick up is to the fuselage side and recessing the tank into the fuse is one way. I like the metal tanks that come from GRW, I think, that have the pickup come out at the bottom of the tank towards the side where it sits against the fuselage. I usually hold tanks on with rubber bands and hooks or the slotted brackets soldered to the ends of the tank if there is room. If mounted aginst the engine bearers or the ply doublers, I like narrow tanks like the one that Fred Kreuger put out a drawing of years ago. I'm sure it's here on the forums some where. it's a chicken hopper/uniflow hybrid that is easy to make and work very well. Plastic tanks like the Sullivan work well also, and I mount them with the widest side against the fuselage also. You can affect a height change also just by twisting the cork or even rotating the uniflow pick up. They are cheap and easy to service.
   Type at you later,
    Dan McEntee

[Matthew Brown]

Thanks Tim.
I have a vague memory of there being an issue with tanks mounted too far inboard but I can't think of what it might have been. I used to have a pretty decent knowledge base on this stuff but that was back in the mid 80's and my memory isn't what it used to be.

Matt

[Tim Wescott]

Thanks Tim.
I have a vague memory of there being an issue with tanks mounted too far inboard but I can't think of what it might have been. I used to have a pretty decent knowledge base on this stuff but that was back in the mid 80's and my memory isn't what it used to be.

Matt

I don't know about too far inboard, but if it's too far outboard the engine won't be able to suck fuel.  I have some with the tanks mounted on the inboard side of the fuselage, and they seem to work nice.  I haven't done A vs. B comparisons (i.e., mount on the outboard side, fly, mount on the inboard side, fly, repeat), so I couldn't say for sure.

[M Spencer]

What I found with the Phantom , Nobler Sized . Side Mounted FSR 25 - > Magnum Pro actually , with a Fox 25 BB C/L intake bunged in   WAS ,

The NVA , level with the outer Fuse Side , the tank thru the bearers , Outer tank face ( uniflow ) & NVA dead on the same line fore & aft ,

Youd set RICH on the Ground - Get up and whistle thru a few O/Head ' 8 ' s , as it leaned off with hight , O'Head was the test for if you were ' to dry ' . - stagger sag etc etc to lean .

The Good Thing was , as you dropped to the deck / level , you were ' full rich ' , nice , fat & steady , turning the nose ( SUCTION - Not Muffler Pressure ) power would come on .
Level , the higher the leaner . Thus the setting trick . Worked good in thee wind.

--------------------------------------------------------------------------------

The Tank was large - for a 35 , about 5 1/2 Oz , so gave ten minutes on the 25 , 7 on a OS 35 , 7 1/2 on the 21/35 , 5 on a C 35 .

1/8 plumbers copper tube vent / filler . this is thick wall , about 1/16 BORE  .( cap the Vent ) . The Uniflow came out about 3/4 in with the end cut / filed on a 45 Deg. Angle .
I curved the pipe outside round 90 Deg. Facing into the staggering   prop blast one day . At the Field. Straight of I had to go in 1/4 turn for the same ground rpm s .
Two Flights and I put it back straight out , as Id LOST 1/4 turn of ' variation ' , rich ( shoulder hight ) to lean ( top of the wingover ) . So thats a point to watch .

Maybe the Vent Pipe NEEDS to be tangental ( end cut 45 so its not siphoning ) NOT parrallel to the Flightpath , where the wind / airspeed throws the ' weight of fuel ' trick out the window .
----------------
Another Point with my set up . NAUGHTY . If your Familiar with the ' Emulsification Tubes ' in a WEBER CARB , these Pre Mix Fuel & Air ( like foamy Fuel ! ) BEFORE it gets to the Main Jet .
My Staggering   Intake set up ( a Fox intake Filled down 1 mm to plug in Magnum Case , Locked with Cinch Bar . AND a 5.000 year old TAIPAN NVA ( well , about 1970 ) had a . . . .
Horribly loose Needle Valve . One Sided ' clicker ' for lock . A FINGER rolled on the needle to alter a click or three would rock the needle - so youd get a two second ' off ' setting ,
a second after your finger was off , it'd be back to its Old Familiar BURBBLE .

Feeling Guilty at such travestys of decorum   ' we ' fitted a sealer on a few occasions . A 1/4 length of fuel tube compresed when the needle was in the o.k. posn , To SEAL the ' Air Leak ' .
Most of the Burble was GONE , and the Needle had HALF the Adjustment Range . As it was better ' leaking ' it reverted to ' as installed ' as a flat run in the wind was TROUBLE with a .25 .
-------------------

FEAR NOT ,
Saw a chap with a Twister I think , with a OS 40 FOUR STROKE sidewinder . Three Guesses !. The Tank was mounted outboard face level with NVA  longitudinally .
This Thing DEFINATELY ' Fatted Up ' Down Low , and Leaned Off , HIGH . Across the top etc lean clean & on the ball , Dropping Down she backed off . Audibly .

So Know you Know .

Points to watch maybe ;
Small Bore Uniflow pipe ( I thought they ALL neded THAT ).
Uni Pipe inline with the lines , inboard , end filled 45 deg. plus .

Some Engines may like it some mayint . Might dig a picture out of the clapped out old dog . A fingertip on the end of the neddle would rock it 1/16 in, in running posn.  

Young thingowotsit of the Guitars FS 40 4T definately benifitted , CONTRARY to Popular Opinion Then , that 4 strokes DONT speed up . They Didnt believe they were seeing THAt .

Thirdly ; maybe ; its more effective with a Large Biased intake than a weenie high suck one - I think the .25 set up was 15.2 mm Sq. WillCheck that . Tamarra .

[M Spencer]

Does the inward/outward position affect the running and needling of the engine?

definately . You cant run both engines of one tank on a twin C/L , Unfortunately - The Fuel Head is the lateral dimension - so you can start to understand theres No Lateral Dimension Overhead .
Its Become a Vertical One .

[M Spencer]

Measured at 7.4 mm Bore Venturie , pretty much parrallel ( its a Fox Intake , carved down 1 mm to fit the case ) Spraybar is 4 mm .

The Spraybar sits 1 in + above ( outside ) the Bearers . As the nose is 2 in wide , thats 1/8 or 3/16 outside the outside edge of the tank ,
So Always a head from the rotational force , Down Low . Only ' up the Top ' the Spraybars ' OVER ' the Tank .

Hence the , whip it up the top and whistle around in a few 8s , to check the setting . It Has to Get Sufficent Fuel UP THERE .
Down the lower quarter height wise , Its Richened up , to a meaty 4 stroke . If It 4 strokes  .

Spraybar got slightly bent last time it flew a year or so back , Needs finishing straightening , as with No Slack it wont do the Burrble / 4 stroke bit .

MAGNUM 25 PRO ( Wow ) mainly run on comercial fuel , 10 worn to 9 1/2 x 6 . Black 9x6 or 9x4 for flying in a gale . K&B 3.5 schnurle muffler
thrown on with one pipe knocked out & bunged , so 1 exit .Bit of Volume in the muffler , even if its not the most aerodynamic device known to man .

[Steve Helmick]

Some folks have been known to solder a suitably sized brass tube(s) through the tank, allowing them to bolt it through the tube(s). Copper would be better. Not too practical for profiles, unless you build a platform onto the side of the nose for the tank to sit on. That might be a good idea, since it could be tied into the wing to stiffen the nose. Depends on your local Profile rules as to legality. Would be ok here. Steve