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Pulling power in the .55 AX

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Pulling power in the .55 AX

Old 07-10-2007, 01:21 AM
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Default Pulling power in the .55 AX

Hey all

I have a new 55 AX that I am running in a 40 sized F3A style aircraft. I am currently running a 12x7 sport prop and a standard muffler. What do you recommend in terms of props for pulling power through the verticals, also what about one of those pre-tuned Jett stream mufflers. I have seen reasonably large increases in RPM claimed by the manufacturer? can I also strap one to a ST 51?

Cheers

Hughie
Old 07-10-2007, 06:01 AM
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Default RE: Pulling power in the .55 AX

I'm not into any specific competition but I have a Strega with a 55AX. After experimenting with props I found that APC 12x8 works very well. Revs are kept down under 11000 but the plane pulls from low throttle all the way out to full power. The plane flies just as fast but does take a fraction longer to wind up the speed. With a 12x6 MAS I can pull unlimited vertical but a 12x8 will only do a hover for a short period of time before falling out.

Having worn out a 46AX and seen other people do the same, I'd avoid going for massive revs. At the first sign of engine problems check the bearings, it's very likely they are starting to come apart.... If you ignore the problem the piston will be chewed very quickly and the engine will never run properly again (without a new liner/piston...which costs fractionally less than a whole engine).
Old 07-10-2007, 07:34 AM
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Default RE: Pulling power in the .55 AX

I would have thought that a 12x8 would be more a 60 size prop, but that is interesting, I will give it a go. I am still keen to find out more about these Jett stream mufflers as well, especially for the G-51. Has anyone tried this before, or what do you think of the idea. I am plkanning to put it in a .36 sized Model Tech Extra 300, simply for the speed it will produce and hole punching ability. A good weekend tear around plane. Obviously I will do some strengthening work before I take to the skies.
Old 07-10-2007, 05:15 PM
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Default RE: Pulling power in the .55 AX

The smallest recommended prop for a 55AX is 12x7 but as they aren't readily available locally I took the 12x8's. The 55 is more of a torque motor than the 46 and thus can get away with much larger props.

The 12x8 lets me fly around at low speeds, right on the stall, and yet be able to pull out of anything with an application of throttle despite the fact the engine doesn't pick up revs instantly. By comparison the 12x6 will not handle that low speed treatment and when opening the throttle the revs will shoot up but it will take fractionally longer for the plane to pick up speed.

I'd say the 12x8 is great for low down pulling power and gives similar top speed to the 12x6. The 12x6 though is more for higher revs and pulling vertical stuff. It's just a matter of choosing what best suits your plane and flying skills.

I have no idea on Jetstream mufflers but I did use a GMS 47 muffler on the 46AX. It gave about 300-800rpm more but whether it was worth it is another story.

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