Mangy Fox Update

[Av8r3400]

I've been a little quiet lately with my 70 hour per week business getting in the way of my Kitfox-ing. But, I do have a bit of a story to tell.

I had a bit of an incident while taxiing. I was turning around into a field next to a friend's grass strip and hit what I thought was just a patch of snow, that turned out to be more of a snow filled furrow. Long story short, I modified the tips of my Prince Prop.

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That day (Saturday 11-16) I gave a call to Hal Stockman (a national treasure in my book) to place an order for a new Luga/NR prop from him. I was surprised to find out he had one on the shelf and would ship it out to me asap. It turns out he shipped it that day!! What a swell guy! With a tear in my eye, I had to leave the Mangy tied down at the grass strip for a couple days (with a winter storm coming) until the new prop arrived.

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That Tuesday (!) my new Luga prop arrived from Hal. (Did I mention what a swell guy he is?). I quickly put the prop on, that Wednesday, and got the plane home. I found out that if I pitched the prop to where I thought it should be the trailing edge would contact my cowling. It was always close on my Prince prop, but it didn't hit. This did. So I flattened the pitch for clearance and got the plane home. I could over rev the engine at half throttle and all I could manage was 70 mph on the way home, but I got her home to her own hangar in time to avoid the coming blizzard. Here's the new prop on my kitchen table:

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My Prince was a 78" diameter by 48" pitch. It was a big prop. It was a takeoff and climb animal on my plane. Unfortunately the large diameter also meant it was pretty draggy and my top speed was a little better than 100 mph on a good day. This was never a big problem, because the STOL performance was so stellar. An acceptable trade off to me. The new Luga is only 72" in diameter. So I was preparing to take a substantial hit in STOL performance.

To install the prop with the way my cowl is configured, I needed to add a 1" spacer. Hal happened to have a used one for a good price and he asked me if I wanted to try a balance ring with it. I had seen these in Aircraft Spruce and was curious. I have similar balance rings on my big truck wheels and know they work awesome in that application, so I said sure, why not. Here is what the stack up looks like. (Spinner options are still being explored)

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AS of today, I have about 4 hours on the prop. I explored pitch settings starting at 15º which is the zero setting on the pitch gage. At that pitch, I would quickly over rev the engine on takeoff and level flight. So I bumped up the pitch to 17º. That only gave me 5200 on takeoff, but my cruise speed jumped up to over 120 mph in rough, unsettled air. I have it now at 16º with is appearing to be a nice compromise.

My takeoff distance may be a few feet more than with the prince, but not more than literally a few feet. Climb performance with the Prince was stellar to say the least. The Luga does well, but not as well. With the Prince I was seeing sustained climb rates of 1700-2000 FPM. With the limited time I have on this new prop, I'm seeing 1400-1600 FPM. Nothing to complain about by any means. However, I am seeing cruise speeds in the 110-115 mph range with 16º of pitch. I am not complaining. More that an acceptable trade off.

Now what everyone is waiting for: The Balance Ring. This thing is AMAZING!! This prop with the balance ring is so smooth, like nothing I have ever flown before. Every 912 I have ever flown has a little rough patch from 2500-4000 rpm give or take. Mine had it too. No amount of carb balancing or Dyna-Vibe-ing the old prop would get rid of it. With the balance ring this is GONE! Incredibly smooth! Our EAA Chapter has a Dyna-Vibe machine. I have used it many times and know they work well enough, but I was never totally satisfied with the results I saw on my plane or any other I helped with. This balance ring has, in my opinion, just obsoleted the need for a Dyna-Vibe or any other balancing machine.

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