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SJ .50 on Great Planes Escapade

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Old 10-03-2009, 10:59 AM
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rwsduc
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Default SJ .50 on Great Planes Escapade

Bob,

Good morning. I recently purchased an SJ .50 (thanks for your recommendation) and broke it in on a test stand with a 9x6 prop and bubbleless tank. I ran six tanks through it on the 9x6 and was hitting over 18,000 on the stand. I recently put it in a Great Planes Escapade and put a 10x6 wood prop on it. I used the wood prop because the hub of an APC was so thick that it only allowed a few threads of engagement and I didn't want to risk throwing it and losing the spinner.

This morning I ran it for the first time on the plane, albeit NOT with the bubbleless tank. I don't know if the tank was the issue or the Master Airscrew 10x6 is too much prop load, but I couldn't reach a steady 15,000 rpm. Tuning was very erratic, the pipe would stage on occasion, but the needle was very sensitive. I'll put a Jett tank in there tonight, but I wondered if you could recommend a good prop size for this plane (gift from my girlfriend, and I didn't have a more appropriate motor to install in it). It won't reside there long as I'm waiting on an F20.

Thanks in advance,
Rick
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Old 10-03-2009, 12:43 PM
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bob27s
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Default RE: SJ .50 on Great Planes Escapade

Hi Rick,

First, the prop mounting ...

The jett engines have a removable/replaceable threaded prop stud. You do not want it threaded in so it comes to a hard stop, should be slighly loose. Unscrew it out of the engine, then thread it back in about 6 turns, and you should have no problem installing the APC prop. The engines when new are shipped with two prop studs, usually one is longer than the other.

Install the same 9x6 you used for the run-in period. Compair apples to apples. The engine should perform the same as it did on the test stand. If it does not, then you know it has something to do with the aircraft/fuel system. If it runs fine, back it down from peak rpm about 1000 rpm and just fly it.

The MA nylon 10x6 is just fine, it works and runs as well as the APC. Most wood 10x6 props tends to be a thicker blade - most will work fine, but if they do not turn up, the engine will struggle. Perhaps save that until you get more time on the engine.

The engine should not have any real issues in the Escapade, unless (As you sorta noted) the fuel tank is mounted in there way too tight. The bubble tank is not a 100% necessity, but it does make it easier.

Let me know how you make out

Bob

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