The flying monkeys got me...

Helis and fixed wing

AMA 957918
IRCHA 4345
AMA Intro Pilot Instructor

Tuesday, May 3, 2016

Spitfire Update: Pretty much done!

I've had to redo a few things, some a couple of times, but she's running and ready to maiden with a few adjustments.



Ready to start!





First run (Though Joe Nelson at RCGF-USA test started it before sending it to me). I had a lot of trouble finding the right settings for her. She runs great, but finding her tune spot was tough. To get a nice balance between high RPM and sufficiently slow RPM at idle took hours, of trial and error and I'm still not sure its right. Her high needle pretty much stays where it is, around one turn. The low needle which is tuned to get a clean advance from idle to high, changes everything including high RPM. It is the only needle I adjust, for the most part. That's odd. 

I used a Master Airscrew Scimitar 14x8 and a Master Airscrew 13x8x3, and with both get around 8100 RPM at full sometimes as much as 8400, idle around 280. The servo limits are at the stops for the throttle t about 115% high and 20% low. With the 14x8 I get about 6.8 lbs of thrust, and with the 3-blade, about 7.7. The plane weighs 7 lbs, so I am going with the 3-blade. She gives me over 20 minutes a tank at mid-throttle. I had to dial in a throttle curve to get a true 50% throttle, and a transition at low and high approximating 25% and 75%. All this spinning dishes... changing one thing changed another. I do think I have found her sweet spot. I suspect as she breaks in more, and when I get the cowl on she will need more tuning. I decided I need to create a hatch in the cowl to get to the needles. More on that later.



The left mount cracked during the break-in runs, so I had to replace it. I didn't want to re-grind one, since that's why it broke. So I decided to do it the way I should have, and cut out the triangle wedge that prevented me from putting it there. Later I noticed that the engine was pointing a bit left... so I replaced the right one, also grinding down the wedge, and now its straight and not MacGyvered.




The QuikFire was a tight fit, added weight, and I wasn't sure if the little engine could pull fuel through it making the tuning more difficult. It has taken a lot of time to tune her... She still idles a bit high. 




Cowl on!









I had to go through a couple versions of the choke arm.  Straight out works best. That's the cylinder on the plane's right side next to the cylinder. Works great!




Next will be seeing how things change with the cowl on, then maiden. I am thinking of doing the maiden at the SNHRCC field in Hudson, where there is more open space. 

In fact, I am hoping to head out there again soon. I rode my motorcycle out there the other day, and I like the field, first time I had been back in a year. I love the openness. Its a little further out, and it doesn't have the geo-tex runway, but the grass is short, even if it is a bit of a hill. Lots of room to fly, close in, and nice un-obstructed approaches.

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