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Sport Jett .50 - 8/5/2005 3:20:55 PM   
MJD


 

Posts: 1682
Joined: 5/27/2003
From: Orangeville, ON, CANADA
Status: offline 		Hi,

I have a question regarding applications of this engine.

I bought it and plan to install it in a Whiplash, but haven't got around to that yet. I have another aircraft with an OS .46FX that begs for more power, and I plan to fly it over the next month while on vacation. So I started eyeing the Jett .50 as a quick changeover. This is appealing because than I get to play with the Jett.

With regards to ABC issues, operating temperature, piston fits and overall performance etc. - if I begin this engine's life running 10-6 or 11-5 props in a sport application [which I realize it will turn quite strongly as well] then install it later in the Whiplash running higher rpm on smaller props (8-8,8-9 etc.), have I compromised anything by doing so?

Buying another one would certainly take care of my concerns, but that needs to $wait a $bit..


Thanks,

Mike Dennett
       Post #: 1

RE: Sport Jett .50 - 8/5/2005 6:07:01 PM   
bob27s



Posts: 4819
Joined: 4/9/2002
From: Cleveland, OH, USA
Status: offline 		Hi Mike....

Thanks for writing. Good question.

You should have no problems.

If you were running it with the longer muffler or a turbo-jett, turning 12" props at 14K rpm, yeah... you might have a concern. (although my old SJ-46 didnt seem to care going back and forth)

Break the engine in per the instructions. That is the first step. You want to break it in on a 9x6 set to turn 17 - 17.5K rpm (slightly rich)

The 10x6 will turn 17,000 or therabouts after break-in. That is the 'baseline' for the engine, and it loves that prop. You can fly it like that all you want. The 11x5 may be ok too... likely will drag down to 16,500 or so, but that is ok.

The key is the RPM, which is goverened a bit by tuning range for the muffler. You want to prop to run between 15,500 and 18,000 rpm with this engine/muffler.

When you get to the Whiplash, no problem. You want to prop it to run the engine at the same 17,000 rpm (peak ground) anyway.

Use a smaller 8.5 or 9" diameter. APC 9x8, 9x9 are ideal. You can try an 8x9, but those props have a tiny hub on them...scares me to try and turn those at these rpms.... you would be best to use a 9x9 and cut the diameter down. Also experiment a bit with the Q-500 props - 8.8x8.75, 8.75x9W, 8.8x8.5. All of those will keep you in the power band and go like heck. Also the 8.8x9 works well... trim the tips a bit as needed (about 3/8" each)... get the engine up over 17K rpm with it.

Let me know how things go. Send me a few photos if you have a chance.

Bob Brassell


_____________________________

Bob Brassell
Jett Engineering - Engine Mfg Support Forum Host

(in reply to MJD)
       Post #: 2

RE: Sport Jett .50 - 8/5/2005 9:16:49 PM   
MJD


 

Posts: 1682
Joined: 5/27/2003
From: Orangeville, ON, CANADA
Status: offline 		Thank you Bob. I'll stick with the 10-6 if I do this, and let the engine run where it's happy. RPM is good, I detest lugging engines. The 11-5 appears to be about 10% more load factor than a 10-6. Besides, if a 10-6 turning 17k plus isn't good enough for the aircraft I have bigger problems!

BTW thanks for anticipating a question I had about the Whiplash, which was which of the pylon props versus the sport props to look at when the time comes!

I will be getting my feet wet on speed-only planes with my Magnum R first; the orientation issue with the delta is an extra factor I'll leave until I have the top speed issue under my belt.

Al the best,

Mike Dennett

(in reply to bob27s)
       Post #: 3

RE: Sport Jett .50 - 8/5/2005 9:43:01 PM   
bob27s



Posts: 4819
Joined: 4/9/2002
From: Cleveland, OH, USA
Status: offline 		Always glad to be of help

Enjoy the weekend.


_____________________________

Bob Brassell
Jett Engineering - Engine Mfg Support Forum Host

(in reply to MJD)
       Post #: 4

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All Forums >> Glow Engines, Gas Engines, Fuel & Mfg Support Forums >> Engine Manufacturers Direct Support Forum >> Jett Engineering Support >> Sport Jett .50
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