Stebbo

I've been flying my new Hawk SE for nearly a gallon of fuel and all is well. Thanks to every one on RCU who helped me solve my original build problems.

The heli is great fun to fly and very smooth and stable (with only a small amount of fuel foaming). The engine performs well at idle, hovering and fast forward flight. I seem to have plenty of power from the OS32 using wildcat 15% with a noticable trial of smoke with the Main needle 1.5 turns out.

But.... the base plate of the engine is too hot to touch for more than 1 second after running and when trying the pinch test on the fuel line into the carb, the engine will speed up from idle after only approximately 1 to 2 seconds. And when the engine is hot on landing after flying around as I close the throttle to idle the engine occasionally splutters and four strokes.

Does this indicate that my idle mixture control is too lean ? or should I leave well alone as the heli flys well enough.

marked23

I've been reading up on this... OS doesn't recommend a particular temp range. It would be helpful if they would at least say what "too hot" would be. My guess is that too hot is above 210F.

My OS32 (non ringed), in my Hawk, runs well only after it reaches 165F. (measured at the base of the head.) Any cooler and I get foaming. A typical flight for me will end with the engine at 190F. That's too hot to touch, and I'm not the least bit worried about that being too hot for the engine. I too have a visible smoke trail coming out the exaust. Still, other pilots tell me I'm lean. I say bunk.

Sorry, I haven't done the pinch test on mine.

I never get any 4-stroking when I land.

What you could do is open the mixture a bit more (count your clicks, so you can put it back). Keep opening your mixture until you notice a lack of power. Then close it in a few clicks and see if that is good. That should give you the richest mixture that provides the power you expect/need.

-Mark

fiat

Mark , what fuel are you useing ????? Alan

marked23

I'm using Cool Power 15%.

-Mark

syclic

It sounds like your idle/hover SCREW is a bit too lean. Back it off about a 16th of a turn at a time till any foaming stops and the temp will stabalize..

fiat

Is the low end air fuel needle still affective at mid stick ??? Or mid throttle I meen.

wisdom-seeker

Not merely yes, but it dominates the main needle at mid-throttle. The main needle has little or
no effect at mid-throttle.

fiat

Thanx for your reply, I was wondering because I went from 15% to 30% fuel and now the motor seems to load up at low throttle to mid throttle. I have been adjusting the main needle but end up running a little lean this will explain that... Alan

Stebbo

Thanks for your advice. I adjusted the engine over the weekend and ended up by turning the idle screw out by 1/4 turn.

I now have no foaming and only slight sloshing of the fuel, the temperature on the back plate is slightly cooler, the time doing the pinch test has increased to approx 2.5 seconds and I have no spluttering of the engine.

The biggest difference is a noticeable increase in power from the engine at mid throttle (ie hovering).

I'm much happier with the engine now as it now never misses a beat.

But (isn't there always a BUT), my head spead has increased to 1700 which sounds to fast. What head speed should I be looking for ?
At the moment I'm flying pod and boom but over the winter I'm going to fit a fuselage so should I decrease the head speed ?

marked23

1700... Not a problem. With 550mm blades, you need to be running that fast for normal performance. If you run it slower, you will be behind the power curve of that engine. I found this out by trying it.

A local expert convinced me that my head speed was too fast... He tached me and said that I was running 1750ish. He suggested that I should lower my throttle curve until I was running 1600 or less. So I did that. On the first day, that seemed to work OK, but it was definately harder to fly. The one important thing thing I noticed is that I had to put in full stick to stop a descent.

On the next hot day, I couldn't fly at that head speed... It would bog and the motor would die 3ft off the ground. I changed my throttle curve back to what it was. 1600 might be perfect for a 60 or a 90, but you simply need more head speed for a 30.

If you are below 2000, you are still in the safe range. Use what works best for you.

-Mark