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HomeAircraftHelicopterCentury Radikal G20-30 N640 Hawk Predator › backwards loops, running out of nitro???
01-12-2010 12:36 AM  8 years agoPost 1
CompyMike

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sacramento, ca

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So I have this Century Hawk Pro with a Hyper 50, TJ PRO, tall gearing, 550 CF blades.
Great flyer. Stock tank and a header tank just above the stock tank on the carb side.
I can start doing some backwards circuits. Counter Clockwise circles. I'll get some good
speed going and when the hawk is flying backwards towards me I will give forward elevator
to do a loop. As I am going through the top of the loop I can hear the Hyper RPM drop. Pretty sure
it is not bogging. It is hard to bog this hyper. It always recovers quickly.

It never does this when I do FF loops. I'm thinking it is a fuel supply issue. Engine is well tuned. Stays
consistent. The TJ Pro works very well.

I'm using just regular fuel line for the clunk lines. I'm thinking as the hawk goes into a backwards loop the header
clunk line stays towards the back of the header tank and the fuel gets pushed towards the front of the tank. The header tank
clunk line is not flexible enough to bend towards the front of the tank maybe.

It will do this with an almost full tank. And a half tank. I'm not brave enough to this with a near empty tank.

I guess I could go with a thinner fuel line for the clunk but I'm thinking that would change the fuel mixture and I would then need to re-tune. But it is hard to fit that smaller diameter fuel line onto the existing fittings.

Mike

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01-12-2010 12:50 AM  8 years agoPost 2
Brokenlink

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Oakdale

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You probably have changed the clunk line in the header tank right?
It's probably just alittle too long and hanging up in there now,not letting it get to where the fuel is.

Jamie Griffith

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01-12-2010 12:54 AM  8 years agoPost 3
Brokenlink

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Oakdale

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I just reread your last post,your header should tank should be full if you have enough fuel in main tank.
Does it do it when main tank is full?

Jamie Griffith

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01-12-2010 01:00 AM  8 years agoPost 4
CompyMike

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sacramento, ca

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The header tanks seems to always be full. It doesn't start looking empty till the main tank is dry.

Re-did all my lines about 5 months ago. The header tank clunk line rattles up and down when I shake the heli.

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01-12-2010 01:03 AM  8 years agoPost 5
Twrecks600

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Round Rock, Texas

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I have never used "regular" tubing for any of my clunk lines. Clunk lines are a little bit thinner walled for flexibility. Also, it is very easy to bog the head with bad collective management in a back flip. I have flown a 32 engine and the owner couldn't perform any advanced trick without bogging the head. I took the controls and with the proper collective management, I did a pretty hard 3d routine with minimal issues.

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01-12-2010 03:34 AM  8 years agoPost 6
CompyMike

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sacramento, ca

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Well it didn't seem like a bog when I was doing backwards loops. Maybe backwards loops are more collective intense than FF loops. So where can I get this thin walled fuel line, if you know? Thanks.

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01-12-2010 03:40 AM  8 years agoPost 7
Twrecks600

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Round Rock, Texas

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01-12-2010 06:38 AM  8 years agoPost 8
Gearhead

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Vt

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edited,,
on my Raven (s) after a flight I always had just a little bit of Air in my Header Tanks, maybe a 1/2mm of air in the Tank after the flight, so if your Clunk Line in your Header Tank is to long I guess it could suck some Air as the Heli goes upside down, so if the Clunk Line is a bit short it will be less likely to suck Air,, my Clunk in my Header Tank is about 1/4 inch from the Back of the Tank..

Jim
Buzz Buzz Buzz

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01-12-2010 07:07 AM  8 years agoPost 9
CompyMike

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sacramento, ca

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Hmm that makes sense Jim. I think I have my line as long as possible with it still able to flop from the bottom and to the top of the tank.

So if it is shorter it will never get to the edge of the tank where it can get to any air.

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01-13-2010 04:19 AM  8 years agoPost 10
Gearhead

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Vt

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Mike, have you noticed Air in your Header Tank after flying ??

hopefully this is the problem

Jim
Buzz Buzz Buzz

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01-13-2010 11:34 PM  8 years agoPost 11
CompyMike

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sacramento, ca

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There is an air gap at the top of the tank but I thought that was normal.

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01-14-2010 12:26 AM  8 years agoPost 12
imnxtc

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BC.Canada

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An easy way to determine if it is sub-tank problem is to try a flight with it out of the system. Just plumb the tank in a matter that by-passes it....fuel line to carb vent line to muffler.

If it flies through the inverted bits properly, then you will know it is and iisue with your sub tank.

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