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OS 46AX Prop Size

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OS 46AX Prop Size

Old 02-01-2007, 06:29 PM
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poppy2
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Default OS 46AX Prop Size

This may be silly but here goes. I have an OS46AX engine on my trainer and have an 11x7 prop on it. It seems to take off pretty fast and fly darn fast in my opion. I like the taking off fast aspect but don't really care if it flys super fast. I am just new at flying on my own and don't need it flying at 100 mph.

I have been trying to understand props and what pitch and diameter have to do with take off and flying speed. What I am looking for is lots of thrust, slower landing , slower in flight. This would take in what I have learned a large diameter and low pitch. Going from what I have on my engine now (11x7) and going to a 10x6 would be an equivalent match. And I think that the lower pitch would get me what I am trying to achieve, that is lots of thrust, slower landing, and slower in flight speed.

Now my question. In the manual that came with the Os 46AX engine it gives prop recommandations and they are: 10.5X6, 11x6-8, 12x6-7. I am really wanting to put a 10x6 prop on that thing and see how it runs. Is there a 10.5 diameter prop? (10 and a half) I understand the 11x6 through 8 and the 12 x 6 through 7. I have only been flying for about a year and I don't think I have ever seen a prop that came in half sizes but maybe they do. I know this seems a little confusing. Any clarification would be very appreciated.

Poppy2
Old 02-01-2007, 06:33 PM
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RCKen
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Default RE: OS 46AX Prop Size

They do make the "half sizes", but not all shops carry it and it can be hard to find at times. You can put a 10x6 on that engine with no problems at all.

Hope this helps

Ken
Old 02-01-2007, 06:39 PM
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hezik
 
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Default RE: OS 46AX Prop Size

First of, a 10*6 prop is not equivalent to 11*7. If something were equivalent, it would be a 10*8.

Simply put, size is thrust and pitch is speed. So add more pitch, get more speed. That is, if your engine can handle the prop you've chosen.

If you think the 11*7 is too fast and lacking trust, I would try a 12*6 prop. That should give you less speed and more trust, if the engine can take it. A 10*6 prop might mean your engine will run to fast (RPM). A tachometer is almost a necessity when comparing props.

There are several small programs out there that let you calculate speed and thrust. This is a nice one:
http://www.hoppenbrouwer-home.nl/ika...rusthpv20d.htm
Note that these are calculated values and your mileage may vary.

The page is in dutch, but the program itself in english. You can compare props with it:


Hope this helps somewhat..
Old 02-01-2007, 06:43 PM
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RCKen
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Default RE: OS 46AX Prop Size

I've got a copy on my server, no worries about language

[link=http://www.infinityok.com/review/thrusthp.zip]Thrust HP[/link]

Ken
Old 02-01-2007, 07:07 PM
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Default RE: OS 46AX Prop Size

G'day Mate,
We use APC 12x6 props on 46AX's here, on Skyraider Mk1, to achieve the exact same thing as you reqire, be aware that a 12x4 will do the same thing, with more initial thrust & revs, but less top speed, & slower landing speed, good to learn some aerobatics, more pulling power, try some different props & make up your own mind, you are the only one that knows what you want to achieve.
Don't worry about peak horsepower curves & max thrust crap & so on, it all depends on what YOU require the plane to do. So experiment, it can be very rewarding.

PS. Bolly make 1/2 sizes.
Old 02-01-2007, 07:47 PM
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poppy2
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Default RE: OS 46AX Prop Size

Thanks all for the info you have given me. You are correct that the 10x8 would be more equivalent to the 11x7. I wasn't clear there. What I was thinking was that if I went to 10x8, that would be equivalent but than decreased the pitch by 2 and end up with the 10x6, the decrease in pitch would decrease the speed in flight , slower landing speed, faster take off speed, and be pretty much what I want.

I am happy to know that you can get props in half sizes. Not that I will any time soon. Just happy to know that the manual has correct information in it. Thanks again everyone.

Poppy2

Old 02-01-2007, 09:37 PM
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delman
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Default RE: OS 46AX Prop Size

To slow down your max speed and keep the power for a quick t/o try an apc 12x4. This prop will also set you up for slower landings.
Old 02-01-2007, 10:19 PM
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Default RE: OS 46AX Prop Size

You could also try using the left stick. LOL
Old 02-02-2007, 01:00 AM
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Default RE: OS 46AX Prop Size

I have a 46 on a Kyosho Cap232. I really like the way the APC 11x5 pulls. That prop made my airplane come to life.
Old 02-02-2007, 01:58 AM
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Default RE: OS 46AX Prop Size

ORIGINAL: poppy2
Is there a 10.5 diameter prop? (10 and a half) I
Yes there is, and Bolly make 'em. But a 10.5 x 6 is still not what you want with that engine in a trainer.

11.5 x 5 Bolly is what you want. Purrrrfect for the AX trainer combo. 5" offers superior braking and acceleration, sits in the AX's power band, and is the best match for draggy trainer airframes intended to operate in a moderate speed envelope. Try it and you'll understand.
Old 02-02-2007, 06:06 AM
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Default RE: OS 46AX Prop Size

My personal favorite prop for that engine is the APC 11X5 for trainers, and APC 12X4 for aerobatics. That hits the top end (on the ground) around 13,000, which provides excellent thrust for take off, and gives a nice slow speed at low throttle for landings. Many trainers with an 11x7 are hard to slow down enough to give a good sink rate for landing.

Brad
Old 02-02-2007, 06:11 PM
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Default RE: OS 46AX Prop Size

i have been flying with os .46 engines for 10+years.I have always used a apc11x6 prop. it's a perfect match. [sm=bananahead.gif]
Old 02-02-2007, 06:18 PM
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Default RE: OS 46AX Prop Size

G'day Mate.
If you have not tryed anything else, how do you know an 11x6 is a perfect match.
It depends on lots of variables.
Old 02-02-2007, 06:26 PM
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Default RE: OS 46AX Prop Size

believe me it's pefect.just give one a try you will love it.[sm=shades_smile.gif]
Old 02-02-2007, 06:35 PM
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poppy2
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Default RE: OS 46AX Prop Size

Thanks again for all the info. This is so great to have all this knowledge right at the touch of the keyboard, and to think that it comes from all over the world.

As stated, I am currently using a 11x7 prop on my OS 46AX engine attached to a trainer. (Hobbico Superstar 40) I am looking for fast take off speed, slow flying speed, and slow deceleration speed for landing. After reading all the posts, I am going to use a 11x5, 11.5x5 and a 12x4 prop and make notes. It should be interesting to see how they respond differently.

Poppy2
Old 02-02-2007, 06:46 PM
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Default RE: OS 46AX Prop Size

poppy please try a 11x6 apc youwill love it.[:@]
Old 02-02-2007, 07:20 PM
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Default RE: OS 46AX Prop Size


ORIGINAL: hollywood54

poppy please try a 11x6 apc youwill love it.[:@]
Giving advice like this can be somewhat reckless. What might be a good prop for you and you plane may not be for somebody else flying a different plane. Different planes can and do require different props and setups. It's not something that is set in concrete, so you can't sit there and say that your recommendation is the one correct answer for everybody. Even on the same plane prop choices can differ depending on how the person wants to fly. Higher pitched props will generally give you more overall speed (like high gear in a car), while lower pitched props usually give you more pulling power (like low gear in a car). It just depends on what type of flying you are doing. For instance 3D pilots usually go for lower pitched props because they need the raw pulling power for their maneuvers. Pattern and racing pilots will usually go for a higher pitched prop to give them more speed.

The best advice is to pick several different props within the operating range for this engine and then try each of them and see how they perform. When I am setting up a new plane I will often spend several flying sessions (days) doing nothing but trying different props to see how the plane performs with each one, I'll keep this up until I'm happy with a prop. For what it's worth, I have several 46 FX/AX's and the prop I usually settle on is an APC 10x6 prop. I like to fly a little bit slower and have a little bit more pulling power out of it. But that's just me. What is best for you may differ.

Hope this helps

Ken
Old 02-02-2007, 07:36 PM
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Default RE: OS 46AX Prop Size

Ken i understand what your saying.all i'm asking is to give the 11x6 apc a try.thats all i'm saying later dude[sm=bananahead.gif]
Old 02-02-2007, 07:48 PM
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Default RE: OS 46AX Prop Size

Throw a 12 1/4 x 3 3/4 APC into the mix. Its all personal preferance of what attitude your looking for from whatever plane your flying with the 46 ax.
Old 02-02-2007, 07:53 PM
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Default RE: OS 46AX Prop Size

yo moto your right i'm useing apc 12.25x3.75 on a profile plane. i hover and go 3d crazy with it.but poppy is flying a trainer.[8D]
Old 02-02-2007, 08:21 PM
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Fuel Dinosaur
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Default RE: OS 46AX Prop Size

It looks like we are always trading off on horizontal speed with a short, high pitch prop and slower speed with great vertical performance on a longer flatter prop. Maybe that is why a Moki 2.1 will pull about 25 pounds of static with a nice long prop. Just think what that does for 14-18 pound planes.
Gee, do you think speed and static thrust are relatives? Actually, they are kind of INVERSE relatives? I just love discussions about relativity. Enjoy your flying and be nice to your engines.
Old 02-02-2007, 11:58 PM
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Default RE: OS 46AX Prop Size

ORIGINAL: poppy2
I am going to use a 11x5, 11.5x5 and a 12x4 prop and make notes.
Any one of those three props will work well with the 46AX on a medium to larger draggy trainer airframe like SIG's superb LT-40 or slightly smaller World Models Sky Raider Mach I. It's all about fixed pitch propeller efficiency taking into consideration desired speed and manoeuvring envelopes, engine torque and power curve characteristics plus the characteristiscs of the type of airframe - notably its weight, size, wing loading & aerofoil but particularly parasite drag (which increases as a square of speed). For a more technical treatise offering understanding, the chapter on propellors in Martin Simons book "Model Aeroplane Aerodynamics" is recommended as a start. Have fun.
Old 02-03-2007, 10:34 PM
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Default RE: OS 46AX Prop Size

I will try to point out the obvious here. Your plane is to fast at full throttle, that is not a problem, assuming the engine has a throttle. You can pull back on the left stick to slow it down, and have power to extricate you self from bad situations.

This being said, I have taught many people to fly over the last 20 years, and a 10 x 7 has always been a good match for a 45-sized trainer. You get plenty of thrust, you get good RPM's, but most importantly you can run the engine rich and it will last much longer than your trainer will.

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