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Author Topic: OK for tank to be touching engine on profile model?  (Read 1742 times)

Offline kiwibrit

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OK for tank to be touching engine on profile model?
« on: June 08, 2015, 08:34:24 AM »
I need to put a larger tank in my profile model.  There is just room to put in a fuel tank I have in stock - though it would be touching both the leading edge of the wing and the cylinder head of the engine.  Tight.  Would I get away with that?  First thoughts are no - the tank would get additional vibration (though maybe not a problem if using Armoroil in the fuel) but also the warming up of the fuel by the engine might not be desirable - particularly as the effect would, I suppose, increase throughout the flight.  But does any of you have thoughts on this - or even better, actual experience of flying a model with a tank like that, to pass on?
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Offline Gordan Delaney

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Re: OK for tank to be touching engine on profile model?
« Reply #1 on: June 08, 2015, 09:40:52 AM »
Sorry but NOOOOOOO
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Offline JoeJust

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Re: OK for tank to be touching engine on profile model?
« Reply #2 on: June 08, 2015, 09:44:00 AM »
I had the same problem one time.  The vibrations wore a hole in the tank before the tank was empty.  Better to cut a small chunk out of the leading edge. Better yet get a different style tank.  Check out the Brodak line of tanks. There will be options there.
Joe
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Offline RandySmith

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Re: OK for tank to be touching engine on profile model?
« Reply #3 on: June 08, 2015, 09:45:14 AM »
very bad idea
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Offline Ara Dedekian

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Re: OK for tank to be touching engine on profile model?
« Reply #4 on: June 08, 2015, 10:27:21 AM »


       kiwibrit,

            I've found the next size smaller tank(metal) is usually too small so I shorten the offending tank for a proper fit. I remove the end cap, slice just enough off the tank body and reassemble.

            Place a Dremel cut-off wheel in the drill press chuck. Set the table height and with the closed end held firmly on the table SLOWLY feed the open end by hand along the cut-off wheel. Make multiple, light passes so it won't bind. This is one of those operations (polishing, grinding etc.) where you need 200% concentration on the job at hand. Losing your focus = loss of muscle tension = the work piece getting launched into orbit, hopfully away from you!

      Ara
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Offline Tim Wescott

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Re: OK for tank to be touching engine on profile model?
« Reply #5 on: June 08, 2015, 11:03:27 AM »
Cutting down an existing tank sounds good to me.

You can also consider making a custom tank (which I shouldn't even bring up, because I just don't get along with metal tanks.  However, it works for OTHER PEOPLE quite well!), or mounting the tank on the inboard side.

If you've got almost enough fuel in an existing tank and you're flying on regular glow fuel, you can add up to 2 ounces / gallon of white gas.  That'll increase your fuel economy by about 10%, which is the difference between sometimes crapping out in the clover vs. always having at least six laps to spare.  In the US you'd use Coleman lantern fuel or Zippo lighter fluid.  I don't know what the equivalent brand names would be in England or Oz or wherever you are, but it's basically straight-run petroleum distillate that's too light to be diesel fuel -- you know, the stuff they used to put in cars and call "gasoline", but definitely not the stuff that they put in cars and call "gasoline" today.
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Offline Bill Johnson

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Re: OK for tank to be touching engine on profile model?
« Reply #6 on: June 08, 2015, 11:30:48 AM »
Quote from: Tim Wescott on June 08, 2015, 11:03:27 AM
Cutting down an existing tank sounds good to me.

You can also consider making a custom tank (which I shouldn't even bring up, because I just don't get along with metal tanks.  However, it works for OTHER PEOPLE quite well!), or mounting the tank on the inboard side.

If you've got almost enough fuel in an existing tank and you're flying on regular glow fuel, you can add up to 2 ounces / gallon of white gas.  That'll increase your fuel economy by about 10%, which is the difference between sometimes crapping out in the clover vs. always having at least six laps to spare.  In the US you'd use Coleman lantern fuel or Zippo lighter fluid.  I don't know what the equivalent brand names would be in England or Oz or wherever you are, but it's basically straight-run petroleum distillate that's too light to be diesel fuel -- you know, the stuff they used to put in cars and call "gasoline", but definitely not the stuff that they put in cars and call "gasoline" today.

Naphtha
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Offline kiwibrit

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Re: OK for tank to be touching engine on profile model?
« Reply #7 on: June 08, 2015, 12:44:00 PM »
Thanks for your input guys. I decided to cut back the tank (a commercial one) and was glad I did, since the internal tube layout was not what I expected, and there was a lot of flux on the inside of the end caps - maybe not a real problem, but I don't like to see it). I don't have any suitable copper / brass tube in my workshop, and want to fly tomorrow evening. So I have taken some advice and am going to try a clunk tank on the inboard side, with a fixed uniflow vent. Looking forward to trying it out.
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Offline Motorman

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Re: OK for tank to be touching engine on profile model?
« Reply #8 on: June 08, 2015, 01:32:15 PM »
I know some tanks that are built right onto the motor.
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Re: OK for tank to be touching engine on profile model?
« Reply #9 on: June 09, 2015, 05:18:02 PM »
Quote from: Tim Wescott on June 08, 2015, 11:03:27 AM
If you've got almost enough fuel in an existing tank and you're flying on regular glow fuel, you can add up to 2 ounces / gallon of white gas.  That'll increase your fuel economy by about 10%, which is the difference between sometimes crapping out in the clover vs. always having at least six laps to spare.  In the US you'd use Coleman lantern fuel or Zippo lighter fluid [....] but definitely not the stuff that they put in cars and call "gasoline" today.

That's interesting, Tim, thanks. I learn something new every day.  :)
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Offline kiwibrit

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Re: OK for tank to be touching engine on profile model?
« Reply #10 on: June 27, 2015, 03:13:01 PM »
After some experimentation - cutting down a commercial tank, replacing the pipery with a uniflow set up I liked, and sleeving down the 6.5mm ID venturi to 5.7mm has resulted in strong constant runs throughout the flight. Tank size now: 3oz. Engine: OS FP25.  Plug: Merlin 2003.  Prop 10x5 (either Master Airscrew  Graupner seem fine). Fuel; 25% Castor, 65% Methanol, 10% nitro. Engine richened till it's just hinting at 4 stroke on launch. Very happy bunny.
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