RE: "Eliminator 2" sport jet final assembly  
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RE: "Eliminator 2" sport jet final assembly - 3/14/2005 8:07:04 PM   
daven



Posts: 7026
Joined: 12/7/2001
From: Andover, MN, USA
Status: offline 		I would be concerned flying that with a .61. If your topping 10 pounds, I think its going to struggle getting and staying in the air.

Especially a new design that you are unsure how it will fly.

Supertigre makes a cheap .90 two stroke that would give you a bit more power and not any excess weight compared to the 61 FX.

Does look very good though.

< Message edited by daven -- 3/14/2005 8:08:01 PM >

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RE: "Eliminator 2" sport jet final assembly - 3/14/2005 8:19:35 PM   
seanreit



Posts: 6979
Joined: 4/17/2002
From: Cedar Park, TX, USA
Status: offline 		Tower Hobbies .75 is one of best engines in that class that I have ever flown. If you need a loaner, let me know and I'll send it out to you. It's currently on an airplane I rarely fly (Ucan do) and it will hover and climb that airplane staight up. It weighs 6.5 lbs on a 12x4 prop. I agree that a 10 lb airplane is pushing the 61 fx. If you can get a long enough runway, you might want to consider flying it towards you from a long way out, get it off the ground, hold the line, and make a decision as to whether you want to climb out, or land before it passes you, if that makes sense.

FWIW, I prefer the tower .75 over even the 91 fx. A lot less finicky than a ringed engine. Although I don't think the .61 is ringed.

Sean

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RE: "Eliminator 2" sport jet final assembly - 3/14/2005 8:39:05 PM   
Razor-RCU



Posts: 5294
Joined: 3/21/2002
From: Ramona, CA, USA
Status: offline 		Agree with Sean- the Tower-75 is a beast for the displacement, and my G-90 is great runner.... I do think though that if the Eliminator II flies on a 61 and is a LOT heavier than the production airframes then that says alot- I am sure Mike is well aware of the weight vs power with the 61FX....

My Cermark F-20 weighs maybe 7.5-8 lbs. and did not fly well with the 61FX but the TH-75 is a big improvement performance-wise

Take off 24 OZ. and putt on a Jett-90 and I bet Mikes prop-jet is a hummer!


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RE: "Eliminator 2" sport jet final assembly - 3/14/2005 9:15:00 PM   
Mike James



Posts: 2476
Joined: 1/19/2002
From: Anchorage, AK, USA
Status: offline 		Thank you, guys. I do know you're all right, and appreciate the advice. It spooks me to fly this plane with the current engine, due to the excess weight. I've flown lots of .60-size planes in the past of course, so know I'm "on the edge".

I went and looked at the specs on the Tower .75. They say 2.2 horsepower, versus the OS's 1.9 horsepower, using roughly the same props and RPMs. To me, that looks like a torque difference, rather than an actual thrust difference. After all, a 12-6 at 16,000 RPM's should produce the same thrust, regardless of what it's attached to, right? I'm not an engine expert, so if I've missed something, don't hestitate to let me know.

Sean,

Thank you very much. I have one other option to investigate, and will email you later tonight.


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RE: "Eliminator 2" sport jet final assembly - 3/14/2005 9:33:17 PM   
smchale



Posts: 844
Joined: 6/19/2002
From: Malvern, PA, USA
Status: offline 		Mike,
Let me know if you'd like to borrow a ST 90...I have one I'd be happy to lend you for the testing phases....

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RE: "Eliminator 2" sport jet final assembly - 3/14/2005 10:14:35 PM   
Mike James



Posts: 2476
Joined: 1/19/2002
From: Anchorage, AK, USA
Status: offline 		Thank you, Sean and everyone.

Wow, I do appreciate the offers of loaning us engines. Here's the thing, though...
The plane can't use a prop larger than 12", and still rotate past 10 degrees with ground clearance. That was the original design. Also, the choices in 11 and 12-inch pusher props is very limited, with 12-6 being the norm.

Almost all the engines mentioned in the last few posts, regardless of their horsepower, will not turn a 12-6 prop much faster than 16,000 RPM, which is what the OS .61FX will do. So to do better with prop power, we would need higher-pitched pusher props, to make use of the increased power some of you guys have suggested, or we would need more RPMs.

See what I mean? If any of you find a source of higher-pitched 11 or 12-inch props, please let me know. With either 11 or 12-inch props, we would need something in the 8 to 10 pitch range.

Thanks again, everybody.


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RE: "Eliminator 2" sport jet final assembly - 3/14/2005 11:24:31 PM   
daven



Posts: 7026
Joined: 12/7/2001
From: Andover, MN, USA
Status: offline 		Mike,

I found that Zinger makes a 12x8 pusher prop that would work well with the Supertigre. I have an awesome running supertigre with a pitts muffler that your more than welcome to use if you would like.

http://www.zingerpropeller.com/Pusher.htm

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RE: "Eliminator 2" sport jet final assembly - 3/14/2005 11:38:04 PM   
Mike James



Posts: 2476
Joined: 1/19/2002
From: Anchorage, AK, USA
Status: offline 		Hi Daven,

Thank you for the info on the Zinger props. I should've looked their first, rather than on Tower's site. (where they're not listed!)

Thank you also very much for the offer on borrowing your engine. You guys are very generous, and I can't thank you enough. Let me think this over for a day or so, and I'll get back to those of you who have made the very kind offers. If we take you up on it, we'll take good care of the engines for you, so try and not worry too much.

Now we're on the right track. Knowing that I can get at least a 12-8 pusher prop, that now allows us to consider bigger engines, so maybe we can work around the weight issue of the prototype. It's a huge help, and I thank you again.


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RE: "Eliminator 2" sport jet final assembly - 3/15/2005 2:28:31 AM   
Razor-RCU



Posts: 5294
Joined: 3/21/2002
From: Ramona, CA, USA
Status: offline 		Can you really hit 16K with a 12x6 on the OS-61FX? Is it APC? 16K looks big to me...


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RE: "Eliminator 2" sport jet final assembly - 3/15/2005 2:34:15 AM   
Mike James



Posts: 2476
Joined: 1/19/2002
From: Anchorage, AK, USA
Status: offline 		Who knows? I forgot to tach the engine when I tested it. I'm just speaking in generalities anyway, based on what all the manufacturers say their engine's "practical RPM range" is. (Here's the OS "stats" link - http://www.osengines.com/engines/fx.html )


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RE: "Eliminator 2" sport jet final assembly - 3/15/2005 3:15:53 PM   
SSAN



Posts: 446
Joined: 1/19/2002
From: Queen Creek, AZ, USA
Status: offline 		Mike,

There's no way the OS 61FX will swing that kind of lumber at those RPM mentioned. Even the most powerful BSE Sport Jett .61 will not turn a 12/6 at those RPM. You may want to consider a bigger engine like others recommended since the proto-type is quite heavy. Just a thought!

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RE: "Eliminator 2" sport jet final assembly - 3/15/2005 5:18:38 PM   
Rudeboy



Posts: 3256
Joined: 12/9/2002
From: Bejing, BELGIUM
Status: offline 		Like SSAN said: no way that .61FX will turn up that high with a 12x6.

Jett guarantees 14,300 rpm on an APC 12x6 for the Jett 90L!... , and 15,800 on an 11x5 for the .60. And I think everybody here agrees that Jetts out turn OS's.

I think you'll be lucky to get 11,000 out of it. Bottom line, you need .90 power...

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RE: "Eliminator 2" sport jet final assembly - 3/15/2005 7:59:00 PM   
Mike James



Posts: 2476
Joined: 1/19/2002
From: Anchorage, AK, USA
Status: offline 		Thanks, everybody... I'm receiving what you're transmitting.

The forecast here is calling for rain the next few days anyway, so taking the time to borrow a .90 and do it right won't hold us up.
I'm not anxious to try and prove anyone wrong here. Better to get more power and play it safe.


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RE: "Eliminator 2" sport jet final assembly - 3/15/2005 9:17:55 PM   
smchale



Posts: 844
Joined: 6/19/2002
From: Malvern, PA, USA
Status: offline 		Good idea Mike....you've put so much time and effort in so far, it'd be a shame to be underpowered on the maiden.....there's no replacement for displacement!

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RE: "Eliminator 2" sport jet final assembly - 3/17/2005 9:34:19 PM