Register

If this is your first visit, please click the Sign Up now button to begin the process of creating your account so you can begin posting on our forums! The Sign Up process will only take up about a minute of two of your time.

Page 1 of 3 123 LastLast
Results 1 to 25 of 75

  1. #1

    Join Date
    Nov 2004
    Location
    Blackpool, UNITED KINGDOM
    Posts
    286
    Gallery
    My Gallery
    Models
    My Models
    Ratings
    My Feedback

    How critical is fuel tank level in relation to carb?

    I have a seagull Pilatus PC-9 with an os 46 ax fitted.

    The engine is inverted.

    Usually I would fit the tank in relation to the pre drilled hole in the bulk head. The thing is that the pre drilled hole is not level with the carb. It's a little lower.

    in a pressurised system does this really matter a lot and if so please can someone explain.

    Thanks in advance.

  2. #2

    Join Date
    Nov 2004
    Location
    Blackpool, UNITED KINGDOM
    Posts
    286
    Gallery
    My Gallery
    Models
    My Models
    Ratings
    My Feedback
    It's okay guys I've just read John Buckners post on the 55ax inverted. Plenty of good info there.

    mods you may delete this if you like.

  3. #3

    Join Date
    Dec 2001
    Location
    Upplands Vasby, SWEDEN
    Posts
    7,386
    Gallery
    My Gallery
    Models
    My Models
    Ratings
    My Feedback
    Hi!
    It's vital that the carb is placed in line with the center of the tank when the plane sits horizontal! Ignoring this will sooner or later get you into trouble.
    Jan Karlsson - Supplier MVVS Products

  4. #4
    opjose's Avatar
    Join Date
    Nov 2005
    Location
    Poolesville, MD
    Posts
    12,551
    Gallery
    My Gallery
    Models
    My Models
    Ratings
    My Feedback
    Rubbish.

    The centerline level helps prevent siphoning while the engine is on the ground but once the engine is running it has almost NO effect.

    Otherwise we would have major issues when our planes fly inverted, do up-lines or down-lines. In each case the fuel level is much much higher or lower while the plane is performing manouvers.

    Those who tell you that the centerline is critical, either do not have their plumbing set up properly, or simply don't know how to tune their engines.
    There is an art . . . to flying. The knack lies in learning how to throw yourself at the ground and miss.

  5. #5

    Join Date
    Dec 2001
    Location
    Upplands Vasby, SWEDEN
    Posts
    7,386
    Gallery
    My Gallery
    Models
    My Models
    Ratings
    My Feedback
    Hi!
    I been flying R/C since 1975,both competing in pylonracing on an international level (been to USA on the Swedish pylonracing team in -95), scale and aircombat andflying helicopter and I can assure you that tank placement is very critical on every glow powered plane.
    If you don΄t belive me ; just mount the tank a few centimeters above the carb ...or below the carb and see what happens.
    Attached Thumbnails Attached Thumbnails Click image for larger version. 

Name:	Marutaka DC-3 in pits.jpg 
Views:	136 
Size:	66.5 KB 
ID:	1940611  
    Jan Karlsson - Supplier MVVS Products

  6. #6
    opjose's Avatar
    Join Date
    Nov 2005
    Location
    Poolesville, MD
    Posts
    12,551
    Gallery
    My Gallery
    Models
    My Models
    Ratings
    My Feedback
    I place the fuel tank many centimeters above or below the carb on MANY dozens of planes.

    Except for on the ground siphoning it makes almost no difference. Our planes would be unflyable otherwise.

    Hint: on an 1.20 size plane or larger during an upline the fuel centerline is a good 6-8" BELOW the carb and the engine still runs fine.

    Larger planes with the fuel tank on the wing tube see even larger centerline to carb differences during normal flight.

    This is an example of what was originally good advice ( to prevent siphoning ) taken out of context with unfounded effects read in.
    There is an art . . . to flying. The knack lies in learning how to throw yourself at the ground and miss.

  7. #7
    JohnBuckner's Avatar
    Join Date
    Dec 2001
    Location
    Kingman, AZ
    Posts
    9,318
    Gallery
    My Gallery
    Models
    My Models
    Ratings
    My Feedback
    What Jaka contributed is certainly not rubbish. What is rubbish is the complete disregard and dismissal of the real problem of ground syphoning and the no end of problems it often causes newbies (remember them, this is the beginners forum you know) when first experiencing their first inverted installations. Some of which in some arfs are so badly designed it that it is impossible to avoid "ground syphoning" without modification.

    Such dismissals of this very real problem ("ground syponing") does a complete disservice to those who are newbies to inverted installations even ones who are experienced but just never tried inverted installations before.

    Perhaps this is why One of the most respected and perhaps argualbly, the manufacturer with very best and most comprehensive owners manuals industry wide (OS), very carefully spell out this tank to spraybar (jet) height relationship and express its importance!

    Gentlemen I believe you are both respected and excellent contributors in this forum but this is the Beginers Forum it is not a pylon forum nor is it a giant scale aerobatics forum.
    Last edited by JohnBuckner; 11-20-2013 at 07:05 AM.
    \"Keep your controllines tight\"

  8. #8
    opjose's Avatar
    Join Date
    Nov 2005
    Location
    Poolesville, MD
    Posts
    12,551
    Gallery
    My Gallery
    Models
    My Models
    Ratings
    My Feedback
    The disservice that is done to novices, is to instill a false fear that forces them to cure a problem where none exists.

    I've seen engines go flying off of planes, because the firewall was weakend by the attempt of a novice to drop the tank height, thanks to the hype and fear instilled by those who think they are giving good advice.

    Novices fall prey to comments made here and take actions that undermine safety for NO real gain. They undertake modifications simply because they are convince by people such as Jaka, that "fuel centerline to carb height" is "absolutely critical", as in Jaka's post.

    Yet this is very far from the truth.

    John I suggest you try talking to the engineers that suggested those lines in the documentation of the "manufacturer with the very best and most comprehensive owners manuals industry wide". Ask them what testing and basis went into the assersion. You'll be surprised.

    This was included in the manual, not because of scientific evaluations, but rather it is the result of a long passed down suggestion which in turn is nothing more than a platitude handed down time and again without re-evaluation similiar to the "fuel stays in the back of the tank" myth.

    BTW: I was dismayed to see Clarence Lee purport that nonsense, which will unnerve any applied physics student as it is not based on the real world.

    There are many posts here where some novice stepping up from a trainer inquires about an inverted engine installation in a plane designed for it, such as the U-Can-Do's. The "experts" are all to quick to repeat this mistake. Novices go to extremes to fix what they perceive to be a "problem" where there is none.

    A typical U-Can-Do with an inverted engine mount leaves as much as a 1-1.5 inches of tank/carb height difference.

    Does this make starting the engine problematic?

    No unless the user has been improperly instructed on proceedure. e.g no priming, leave the engine at idle once the plane is fueled, etc.


    Does this warrant ripping up the firewall to establish a new bung hole and tank mount?

    No, if anything doing so runs the far more important risk of weakening the firewall.


    Does this make the engine run differently?

    No NOT AT ALL once it is started and properly tuned.



    This is the VERY place that this information needs to be put forward.

    Novices should NOT be told to modify tank heights, nor that this is "absolutely critical".

    Rather they should be directed to seek the help of people who are familiar with this type of thing and reject suggestions that they MUST modify their planes.
    There is an art . . . to flying. The knack lies in learning how to throw yourself at the ground and miss.

  9. #9
    JohnBuckner's Avatar
    Join Date
    Dec 2001
    Location
    Kingman, AZ
    Posts
    9,318
    Gallery
    My Gallery
    Models
    My Models
    Ratings
    My Feedback
    Hmm, you know everytime someone comes to me with an airplane that drips fuel out the carb everytime you fuel it I will continue to "purport" the "nonsense' (your words) as well as posting how to fix it with a simple three words: Lower the tank!

    Its always worked for me and everyone I am aware of who ever listened. So no matter how hard you try to discredit me or the manufacturers or such famous engineers as the gentleman you mentioned, you are not going to stop me from continuing to try to help folks either in person or using this wonderful medium.

    Oh and by the way you have never seen me suggest to anyone "Ripping a new Bung Hole" never, and of course you would know that if you had actually read any number of my suggestions here at RCU as well as know the solutions I offered.

    So no, I am no engineer of any kind and certainly no great communicator however, what I am is a 'survivor" so I will continue to try to offer assistance in anyway I can. but do feel free to "purport" your own "rubbish".

    John
    Last edited by JohnBuckner; 11-20-2013 at 12:42 PM.
    \"Keep your controllines tight\"

  10. #10
    opjose's Avatar
    Join Date
    Nov 2005
    Location
    Poolesville, MD
    Posts
    12,551
    Gallery
    My Gallery
    Models
    My Models
    Ratings
    My Feedback
    Don't take my words out of context in a vain attempt to discredit my assersion. You normally don't resort to such specious rebuttals. Such is the response of someone that has none.

    Surely you can argue in a more grown up manner?

    I said that Clarence Lee was spouting the "nonsense" about the fuel staying in the back of the tank.

    The assertion that "fuel level centerline to carb height difference is CRITICAL" is erroneous.

    Again our planes would NEVER fly if this were true. Remember the fuel video posted here?

    Siphoning IS a problem, but it can be ameliorated by proper technique.

    If fuel is dripping out of a carb every time you fuel a plane, check the plumbing... this is NOT necessarily a siphoning problem.
    Review the fueling proceedure. Do you need a CLAMP? Do you need to keep the throttle closed until the plane is about to be started?

    Suggesting to NOVICES that they LOWER THE TANK is however a huge safety concern. A 1-2" height difference does not warrant the associated risks.

    Tell that to a novice and they'll do things to cure a problem that could be better handled by mere changes in proceedure.

    Which do you think is more important?

    That their engines don't go flying off when running?
    Or that they need to deal with a different starting routine?

    As I said, I've seen the former occur because of the "Lower the tank" advice. Bad advice when given to someone who is just moving beyond trainers.

    As far as you or the manufacturers, have YOU ASKED? Have you actually TALKED to the engineers?

    Because I'm sure you wouldn't believe what I heard from them, I asked you to find out for yourself. ( Hint: It is not CRITICAL ).
    Last edited by opjose; 11-20-2013 at 01:33 PM.
    There is an art . . . to flying. The knack lies in learning how to throw yourself at the ground and miss.

  11. #11

    Join Date
    Nov 2004
    Location
    Blackpool, UNITED KINGDOM
    Posts
    286
    Gallery
    My Gallery
    Models
    My Models
    Ratings
    My Feedback
    Thanks for all the contributions guys. It's good to see a few different opinions. As a person that has studies physics I too think location should not matter once the plane is running however starting the plane is where my problem lies.

    even if I wanted to lower the tank it would not be possible as there is just nowhere for a new bung hole. Even if I fill the old one and reinforce the firewall.

    anyway going back to the debate above. Great debate by the way chaos. Would it be acceptable for a centre line to be lower than spray bar then? Surely the muffler produces enough pressure to push the fuel through?

    As fas as my pc-9 goes I got it in the air. I had to fuel up, keep e throttle at closed off and right before starting I set to idle. I also removed the plug to check it was dry. It actually started quite easily to be honest. It did cut in the air and I had to dead stick. Wow these planes come in fast.

    I refuelled and checked the high end needle again. The low end is pretty good with smooth transition. I somehow set it too rich and only noticed when airborne. Came in for a landing straight away and set down fine but hit a bloody goal post so now got a leading edge crunch and wing mount bolt holes to refit. No big deal really.

    I think the centre line alignment won't do any harm to follow as a rule but if it's so important surely he manufacturers would factor this into the designs and plans. On most of the planes I've seen it comes through the centre of the mount. Well that's never going to be in the right place so seems daft.

    I'll repair the plane and let you know how I get on.

    I've just bought a travel air from black horse with an Irvine engine and servos for £20 ($30) it meads a repair to the tail plane but only minor. Engine is upright so at least this will be easier.

  12. #12

    Join Date
    Nov 2004
    Location
    Blackpool, UNITED KINGDOM
    Posts
    286
    Gallery
    My Gallery
    Models
    My Models
    Ratings
    My Feedback
    I forgot to add a question I have.

    when I dive my planes for a prolonged period they always seem to cut. I guess because the fuel drops to the front of the engine. Is this usual or should the clunk be able to double back the fuel line to stay in the fuel?

    Surely acrobatic tic planes don't have his issue?

  13. #13
    Moderator AMA 74894's Avatar
    Join Date
    Jun 2002
    Location
    Spicer, MN
    Posts
    1,136
    Gallery
    My Gallery
    Models
    My Models
    Ratings
    My Feedback
    Gentlemen...
    Please don't force me to comply with the request made in post #2.
    I DO appreciate that you've managed not to let this descend into name calling, but this 'discussion' is beginning to skirt the boundaries.
    you've both made your respective points, let's leave it at that, OK?
    Jim Buzzeo AMA 74894
    P-51 Mustang Brotherhood #37
    Sig Brotherhood #95

  14. #14

    Join Date
    Nov 2004
    Location
    Blackpool, UNITED KINGDOM
    Posts
    286
    Gallery
    My Gallery
    Models
    My Models
    Ratings
    My Feedback
    Quote Originally Posted by AMA 74894 View Post
    Gentlemen...
    Please don't force me to comply with the request made in post #2.
    I DO appreciate that you've managed not to let this descend into name calling, but this 'discussion' is beginning to skirt the boundaries.
    you've both made your respective points, let's leave it at that, OK?
    i thought it was very civilised to be honest and good to see a difference in opinion. It gives me the info I need to make my own educated decision. In my case I can't move the tank as there is no more room for a new hole. I could bring the bung inside the compartment but that's going to cause issues as far as securing it properly goes.

    The tank is too high so there should be no fuelling issues, just starting. I have found that using a two line system with a break fjord refuelling in the feed line works okay. It stops fuel entering the engine when refuelling and I just connect it back up right before starting. It's a bit diddly as I brought the line out underneath as I didn't want to effect the look of the plane any more.

    im hoping to repair it tomorrow so I'll let you know how I get on when I go fly again.

    i can say that the PC-9 is a beast of a ship compared to a trainer. Very axial on rolls and just goes exactly where you tell it. Great plane. I just need to get used to the crazy fast landings.

  15. #15
    opjose's Avatar
    Join Date
    Nov 2005
    Location
    Poolesville, MD
    Posts
    12,551
    Gallery
    My Gallery
    Models
    My Models
    Ratings
    My Feedback
    Quote Originally Posted by carl24bpool View Post

    even if I wanted to lower the tank it would not be possible as there is just nowhere for a new bung hole. Even if I fill the old one and reinforce the firewall.
    Yup, and that is one reason I dislike the "lower the tank" advice given so easily.

    If you can do it, by all means DO SO. If it means having to cut joiners or formers, or making any sort of modifications to the plane... then DON'T DO IT.

    As you've seen you will have to worry about your starting proceedure, particularly until the engine is properly tuned.

    One of the problems that often occurs is the engine will have the needles set way too rich from the factory ( I've seen Saito's a good 8-11 turns OUT and yet the engines run this way!!! ).

    Having the needles so far out lets the fuel drip into the carb and the head rather quickly.

    However once the engine is tuned to run correctly, when it is close to an idle throttle setting, the siphoning is VERY slow. No more than a drop a minute or so.

    You should then keep the throttle closed after you fuel the plane. You should NOT prime an engine mounted inverted particularly if there is a height difference, and you may want to set the LS needle just a click leaner at idle to make sure the engine does not bog down due to the inverted head ( not because of siphoning ).

    Hint: Pull the glow ignitor off with the engine at idle. If the engine speed remains the same you have the LS needle set very well. Otherwise adjust until there is almost no change.

    Quote Originally Posted by carl24bpool View Post

    Would it be acceptable for a centre line to be lower than spray bar then? Surely the muffler produces enough pressure to push the fuel through?
    Sure. Note however that some mufflers, particularly Pitts mufflers may have too large exit ports to maintain enough of a pressure differential.
    You can test this by plugging one side of a dual port/tube Pitts muffler... if the engine idles better this way, then you may want to add a bit of restriction to both ports... this is rarely needed though.


    Quote Originally Posted by carl24bpool View Post

    As fas as my pc-9 goes I got it in the air. I had to fuel up, keep e throttle at closed off and right before starting I set to idle. I also removed the plug to check it was dry. It actually started quite easily to be honest. It did cut in the air and I had to dead stick. Wow these planes come in fast.
    Check the idle, it could be loading up in the air. Use the "pull the ignitor" trick.

    Quote Originally Posted by carl24bpool View Post

    I think the centre line alignment won't do any harm to follow as a rule but if it's so important surely he manufacturers would factor this into the designs and plans.
    Correct.

    Good luck with your plane.
    There is an art . . . to flying. The knack lies in learning how to throw yourself at the ground and miss.

  16. #16

    Join Date
    Oct 2002
    Location
    Austin, TX
    Posts
    4,078
    Gallery
    My Gallery
    Models
    My Models
    Ratings
    My Feedback
    I don't know about RC, but experienced folks who fly control line precision aerobatics sometimes raise or lower the tank by the thikness of a playing card. Makes me think that tank placement is important.

  17. #17

    Join Date
    Nov 2004
    Location
    Blackpool, UNITED KINGDOM
    Posts
    286
    Gallery
    My Gallery
    Models
    My Models
    Ratings
    My Feedback
    Quote Originally Posted by Jim Thomerson View Post
    I don't know about RC, but experienced folks who fly control line precision aerobatics sometimes raise or lower the tank by the thikness of a playing card. Makes me think that tank placement is important.
    Im not sure to be honest.

    Once flying the fuel is moving all over the place so what's a cards thickness going to do? Even as the tank empties the forces and pressures will vary.

  18. #18

    Join Date
    Jan 2003
    Location
    Spring Hill, FL
    Posts
    4,700
    Gallery
    My Gallery
    Models
    My Models
    Ratings
    My Feedback
    Tank position matters. There is some leeway but the more you move it from its optimum position the more you're going to see the effects of it in flight.

    A properly set engine is not fully leaned. If it were then those uplines would lean the engine into overheating and probably quitting. The fact that the engine leans in uplines is evidence that changing the tank position changes how the engine runs.

    If the tank is too high then when you fly inverted your engine will lean. If you set the engine to run at it's best lean setting inverted then the engine will be richer when the plane is upside-up.

    If tank position didn't matter then you could set your engine for peak and it wouldn't change during the flight. What we're essentially talking about is fuel level, not tank position. A higher tank makes the fuel level higher and vice-versa.

    Do yourself a favor and get the tank as close to its optimum location as is practical.

    A lot of scale planes have been lost due to engine flame outs because the full scale plane didn't take model airplane fuel tank location into consideration and thus the tank wasn't anywhere close to where it should be.

    Now all that said, you won't see a lot of difference if you only fly straight and level but even then the engine will change as fuel is used up and the level goes down.
    Work is what I do for the love of it. A job is how I pay for it.
    Please visit AirfieldModels.com

  19. #19

    Join Date
    Jan 2003
    Location
    Spring Hill, FL
    Posts
    4,700
    Gallery
    My Gallery
    Models
    My Models
    Ratings
    My Feedback
    "Surely the muffler produces enough pressure to push the fuel through?"

    No. Muffler pressure is not a pump. It reaches a point where the tank is pressurized and the muffler can not pressurize it any further. And keep in mind that pressure setting changes with every throttle change. Higher throttle = higher velocity exhaust = higher tank pressure.

    The pressure in the tank can not increase any more no matter what the attitude of the aircraft. So if you're in an upline then the tank doesn't become more pressurized and gravity makes it harder for the engine to draw fuel.

    Using tank pressure or not you have to set you engine richer to keep running in all flight attitudes.

    Normally what people do is hold their airplane vertically, peak the engine and then back it off a couple clicks. That's very close to an optimum setting for most sport planes. Fly some maneuvers and make small adjustments if there are any problems.

    For me that usually means going just a hair richer than originally set because I don't back off the needle enough when holding the plane vertically hoping that it will work out and I'll have just that tiny bit more power. After a single flight I richen it up and usually it's good to go assuming the engine is broken in.
    Work is what I do for the love of it. A job is how I pay for it.
    Please visit AirfieldModels.com

  20. #20
    JohnBuckner's Avatar
    Join Date
    Dec 2001
    Location
    Kingman, AZ
    Posts
    9,318
    Gallery
    My Gallery
    Models
    My Models
    Ratings
    My Feedback
    Carl I have never suggested cutting a new bung hole, ever I believe that's a poor technique anyway, think about it. The firewall which is the highest vibration concentration on the entire airframe and we are told to stick the neck of the tank directly into a small hole in that firewall while at the same time packing the back end of that tank with foam to prevent foaming. Huh, does not make much sense does it?

    Instead what I have always practiced as well as recommended is in the case of a design that did the bung in a hole thing is I mearly moved the tank to the rear maybe a quarter inch or so sufficiently to allow the tank to be lower to where it needed to be if the nose compartment. Providing support carl for the tank is normally a matter of a few cross sticks. And I am sure the more you become involved in building you will realize just how easy that is to do.

    If the nose compartment is short not infrequently it is quite easy to releve the number #2 bulkhead sufficiently to allow this slight movement to the rear of the tank. Another option in this situation is simply to use a slightly smaller tank i.e. shorter. There is such a hugh variety of tanks out there that using this option usually for me just take a look through my tank supplies.

    Anytime an airplane pee's all over the tarmac after fueling or does not do that until the sun comes up then proceeds to do it then this in my Opinion and yes its always just my opinion, is unacceptable.

    Yes Carl I use a two line system in almost everything (there are exceptions of course) wth a fueling point in the carb line and have recommended this many, many times in this forum, something I have also taken considerable heat over.

    Anyway best of luck and hope to hear of your continuing adventures with your new ship.


    John
    Last edited by JohnBuckner; 11-20-2013 at 04:23 PM.
    \"Keep your controllines tight\"

  21. #21

    Join Date
    Dec 2006
    Location
    ToowoombaQLD, AUSTRALIA
    Posts
    811
    Gallery
    My Gallery
    Models
    My Models
    Ratings
    My Feedback
    On the point of nose down fuel pickup in a modern pumped YS engine F3A aerobatic setup we rely on two things.

    (1) Engine power is usually set to indle in a downline so fuel draw is at a minimum, a 45 deg downline might (?) carry a slight bit of power depending on your setup.
    (2) The "clunk" is covered in an absorbent foam which blocks bubbles AND holds a certain quantity of fuel to prevent air being drawn into the line while the clunk is out of the fuel.
    .....(3) there are also tanks with a bladder in them but they're rare F3A now.

    Now if I were a beginner and flying my trainer with unpumped engine around all day, tank height isn't super critical but if I were flying something which I expected to be pulling sustained high levels of positive and negative g's I'd put in a bit of effort to get the position correct. Even flying F3A I'd only be be pulling sustained (~2-3 seconds) 3g's worst case (except for snaps) so that +1 inch head becomes a +3 inch head and -3 inch. I'd expect sport flyers would be pulling much higher g's for longer periods. eg a 4 sec loop at 130km/hr is about 6g. Pylon racers would be up in the 40+ g so a few millimetres in tank height is critical.

  22. #22

    Join Date
    Jan 2003
    Location
    Spring Hill, FL
    Posts
    4,700
    Gallery
    My Gallery
    Models
    My Models
    Ratings
    My Feedback
    Quote Originally Posted by carl24bpool View Post
    Im not sure to be honest.

    Once flying the fuel is moving all over the place so what's a cards thickness going to do? Even as the tank empties the forces and pressures will vary.
    In control line the fuel is always forced to the outside of the circle. That's why many control line tanks are triangular and they don't need a clunk. The fuel goes to that outside angle dependably. There are exceptions, of course, such as control line combat where the planes are flown violently. They tend to use bladder tanks. I'm not sure if this is the primary reason, but a bladder tank will always pick up fuel until the fuel is gone or the engine quits because there is no air ever in the bladder.

    And I absolutely agree with JohnBuckner on the bung hole. A tank stuffed tightly into a hole in the firewall is getting a lot of vibration. I always completely wrap my tanks in latex foam rubber and never let any side of the tank touch structure. And I never have fuel-feed issues.
    Work is what I do for the love of it. A job is how I pay for it.
    Please visit AirfieldModels.com

  23. #23
    edh13's Avatar
    Join Date
    Mar 2002
    Location
    Mesa, AZ
    Posts
    407
    Gallery
    My Gallery
    Models
    My Models
    Ratings
    My Feedback
    I was a life long nonbeliever up until last week; I never thought in-flight tank height was as important as people preached. I've been flying classic pattern lately with a pumped, piped ST60x on my Tiporare (with a high tank). I think we can all agree tank position is not an issue on a pumped motor. But last weekend I unpumped it while trying a new carb. MISTAKE. I flew two rounds with it and both times my caller had to set the needle way rich to keep it from sagging when held nose high. In flight it never did lean out until I did my first inverted pass. BAM! As soon as it unloaded it went lean, got on the pipe and was screaming! The peanut gallery joked that I should complete all my passes inverted. It's the only way it would run.

  24. #24

    Join Date
    Nov 2003
    Location
    Forest Grove, OR
    Posts
    418
    Gallery
    My Gallery
    Models
    My Models
    Ratings
    My Feedback
    I put a plastic clip on my carb line after fueling. Eliminates any problem caused by tank height. When I start my engine I simply remove the clamp and away I go.
    Simple solution to a possibly complex problem of tank location people seem to have with arf's.

  25. #25

    Join Date
    Dec 2006
    Location
    ToowoombaQLD, AUSTRALIA
    Posts
    811
    Gallery
    My Gallery
    Models
    My Models
    Ratings
    My Feedback
    [QUOTE=CafeenMan;11667259... such as control line combat where the planes are flown violently. They tend to use bladder tanks. I'm not sure if this is the primary reason, but a bladder tank will always pick up fuel until the fuel is gone or the engine quits because there is no air ever in the bladder QUOTE]

    I think the main reason the combat guys us a bladder is that the bladder is blown up like a balloon providing a heap of pressure and the fuel is squirted into the venturi under pressure and not relying on suction so much. The bladder tanks (like the Tettra ones) doesn't rely on the bladder to provide fuel pressure, it's just there to keep the fuel and air seperate in the tank. Muffler pressure can be still used with that type of bladder tank.

    It's key to remember that different setups can be more critical to changes in fuel pressure. I ran a cheap engine for years on 22% castor oil with good success, then changed over to 20% synthetic and could never get it to run right for a whole flight. The drop in fuel viscosity from 22% castor to 20% synthetic was enough to make it too sensitive to changes in fuel pressure from full tank to empty and for nose up to nose level.

    Tank height can be a source of a problem but it won't always be a source of a problem...


Page 1 of 3 123 LastLast

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •  
All times are GMT -6. The time now is 11:49 PM.

SEO by vBSEO 3.6.1 ©2011, Crawlability, Inc.