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What prop size for .15 Sport UC plnes?

Old 09-02-2012, 01:00 PM
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franchi
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Default What prop size for .15 Sport UC plnes?

Hi All:

.

What prop size would you suggest for the following engines, Fox .15 with DDD head, ST G-20 .15 D and a MVVS D7?

In the past I have used 7x4, 7x6 ,8x4 and 9x4 props. My favourite props were the old Cox black plastic 9x4 and the Taipan 8x4 gray plastic. Sad to say, these are no longer availablle.

I have been advised to go to a 10X4 but I an a bit leery of overloading the crank pin with this large prop.

It seems that the 7x6 props turn up too much speed! How does an 8x5 sound as a possible solution! The 8x6 may be too much of a load on these small engines.

Suggestions?

Tia,

Franchi
Old 09-02-2012, 01:13 PM
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Default RE: What prop size for .15 Sport UC plnes?

FRANCHI Looking at the Davis data sheet for conversions a 15 gets a 9x7 and a 20 10x6 martin

what size cc or cubic inch is the MVVS?

post note my minnie telemaster with on old OS10 FP Davis head turns around 9.5K + with A 9X4 WOOD ZINGER Davis sheet reads 8x5
looks like you can go up an inch in diameter and cut the pitch an inch or cut the diameter an inch and raise the pitch an inch there is some flexibility
Old 09-02-2012, 01:34 PM
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franchi
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Default RE: What prop size for .15 Sport UC plnes?


the












Hi:

The MVVS D7 is a 2.5 cc or a .15 c.i..

Franchi


















is a 2.5ccmvvsD
Old 09-02-2012, 01:51 PM
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Default RE: What prop size for .15 Sport UC plnes?

Franchi on the box the MVVS 15D prop sizes read 8x4, 9x4, 9x5 the glow version 7x4, 7x5,8x4 quite a power increase on diesel no surprise martin
Old 09-02-2012, 03:18 PM
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Default RE: What prop size for .15 Sport UC plnes?

For sport CL flying I haven't yet found a .15 diesel that doesn't like an 8x6, and that's usually what I end up using. 9x4 is also fine, and we've been getting good results with the APC 8x5.
Old 09-02-2012, 03:33 PM
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Default RE: What prop size for .15 Sport UC plnes?

Steve I do not fly c/l at this point 9x4 or 8x5 may depend on the plane what gives more thrust the 8x5 or 9x4 ??? martin

What RPMs do you turn on the above they certainly will swing an 8x6 martin
Old 09-02-2012, 03:40 PM
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Default RE: What prop size for .15 Sport UC plnes?

In our c/l club we use the Taipan 8 x 4 white on motors like the MVVS and the STG20/15D in stunters/combat models, and the APC 7x6 in club racers. Both work well with those props.

The white Taipan is available in Australia and may be also available in the US.

The APC 8 x 5 works very well on Oliver Tigers and their clones.

Ray

Old 09-02-2012, 04:26 PM
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Default RE: What prop size for .15 Sport UC plnes?


ORIGINAL: AMB

Steve I do not fly c/l at this point 9x4 or 8x5 may depend on the plane what gives more thrust the 8x5 or 9x4 ??? martin

What RPMs do you turn on the above they certainly will swing an 8x6 martin
Thrust is determined by diameter, airspeed by pitch, so a 9x4 will give more thrust than an 8x5.

And I agree with Steve about the 8x6 as a great start point for all 2.5cc diesels.

Old 09-03-2012, 07:01 AM
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Jim Thomerson
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Default RE: What prop size for .15 Sport UC plnes?

I have found an 8 x 4 to suit me best on ST G20-15 diesels flown on Old Time Stunt airplanes. A 9 x 4 works OK, but I think the engine is happier with an 8 x 4. I am presently running a Taipan 9 x 4 on an AM 25 and happy with it. I have run 9 x 5 on CS Oliver and the # 13 Taipan. Ed Racer ran best on 8 x 6. I ended up running a 9 x 8 on one of Ian Russel's Cheetah engines. I plan to try an 8 x 8.
Old 09-03-2012, 03:00 PM
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Default RE: What prop size for .15 Sport UC plnes?


ORIGINAL: Jim Thomerson

I ended up running a 9 x 8 on one of Ian Russel's Cheetah engines. I plan to try an 8 x 8.
8 inches of pitch! Wow, thats a lot.

Is it intended for a free flight application?

Old 09-03-2012, 10:13 PM
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Default RE: What prop size for .15 Sport UC plnes?

In the end the best prop for any plane/engine combination is the one that makes the plane fly as close as possible to how you want it to go.

I tried a Peacemaker (Rustler Olly power) with an APC 10X4 last Saturday. Just loverly, may go back to an 8X5, or a 9X4 just to see how it changes the flight characteristics.

It's all a learning experience that you must do for yourself if you want to optimise the performance for your style.

G
Old 09-04-2012, 02:28 AM
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Mr Cox
 
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Default RE: What prop size for .15 Sport UC plnes?

Yes, it is all about testing what goes best for the engine and plane together. There is also a Bolly 8.5x6 prop (whith a shape similar to the APC), which is a good match for the Modela Junior (2cc).
Old 09-04-2012, 08:00 AM
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Jim Thomerson
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Default RE: What prop size for .15 Sport UC plnes?

There is a review of the Cheetah, Lynx, and Jaguar in the reviews posted by Downunder. They seem to run in the 7,000 more or less RPM range. i was flying my Cheetah on a Ron Prentice Big Fry, and tried various props. I am building another airplane for it, one more streamlined than the Big Fry. It is a favorite engine, one flip starts, and runs without change through maneuvers.

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