Extreme Speed Prop Planes Discuss the need for speed with fast prop planes (Screamin Demon, Diamond Dust, Shrikes or any REAL sound breakin'''' plane)

mustang 40 size surpass 91

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Old 08-01-2006, 11:09 AM
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juanpipito
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Default mustang 40 size surpass 91

ive got a surpass 91 running a 12x10 at 10,200 rpm. its pretty fast any suggestions as to make it go faster. maybe another prop?
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Old 08-01-2006, 10:00 PM
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Default RE: mustang 40 size surpass 91

I run a Saito 100 in my 40 size WM P-51. I flew mine for many flights ona 12/12 apc . I was worried about rpms and did not want to blow it. I had dialed it in for around 9600 and it was "okay. I started a thread on this quite sometime back getting opinons on high rpms onthis thing. I went down to about a 12/9 apc and I am up around 10800rpms. It's a basic 100 mph plane and I am happy with it.
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Old 08-01-2006, 11:47 PM
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Default RE: mustang 40 size surpass 91


ORIGINAL: juanpipito

I've got a surpass 91 running a 12x10 at 10,200 rpm. its pretty fast any suggestions
as to make it go faster, maybe another prop?
I think that's about all you're going to get out of it.
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Old 08-01-2006, 11:48 PM
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juanpipito
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Default RE: mustang 40 size surpass 91

thanks for the info.. did you get more speed with the 12x12 or the 12x9 ?
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Old 08-02-2006, 06:33 PM
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Default RE: mustang 40 size surpass 91

Juan,

The Surpass .91 will put out more power if you replace the stock header/muffler with a 4-5 inch long thin walled 9mm i.d. straight pipe. I got at least 300-400 rpm more from mine by fitting one. It's still pretty quiet too; much less perceived noise in flight than your average .46 two-stroke.

I found during testing that the restriction is in the stock header, not the muffler. I did not get any gain by increasing the muffler exit or increasing the internal muffler baffle hole diameter. In fact, there was no difference in rpm between running the muffler and removing it. It was replacing the header that struck pay dirt.

My engine now runs a consistent 9700 rpm with an APC 13x10 and 10,700 with an APC 13x8 (the 13x8 should be a similar load to your APC 12x10). These figures were obtained with 20/20 fuel. My OS .91 now significantly outperforms my Saito 1.00 with these props.

I'd also recommend trying other props - the APC 12x10 is a good choice for your current application but you may gain some by trying props on either side of that spec too. As a general guideline, prop the engine for high nines/early tens static.

As you'd expect with most four-strokes, the .91 responds well to upping the nitro too.

Let us know what you decide to do.
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Old 08-02-2006, 09:34 PM
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Default RE: mustang 40 size surpass 91

ORIGINAL: juanpipito

thanks for the info.. did you get more speed with the 12x12 or the 12x9 ?
No , not at all, you think you would with the pitch of the prop and the torque behind a fourstroke. That was my basic thinking. Dropping down to the 12/9 and the extra rpms is what made it better. I actually would like to try an 11/11 or 11/12 apc if they make the 12. Would need to keep an eye on the rpms but it could be better.
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Old 08-02-2006, 11:10 PM
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Default RE: mustang 40 size surpass 91

thanks harry, I guess im on the rigth track then, I just got rid of my muffler this afternoon and aded a straight pipe. ths I did because I was using a pits style muffler with big exhaust holes when I had the engine on my midget mustang, which I lost in a mid air collision, and the engine was spinning at 10,400 with the 12x10. as to the props I have a 13x8 and a 12x9 Im going to be trying out this weekend.

For those of you who like to try out different props, here's and interesting story: I used to have surpass 70 o.s. on this same plane and the fastest speed I would get with a 11x8 and not a 11x10. I bought the 11x10 thinking that the pitch would increase speed, but that didn't happen, it was actually slower with the 11x10 even though the engine revs where higher. I guess at some point we need to start taking into account the airplane's arerodynamics and drag to trully determine the right prop.

thaks to all of you for the info, will let you know how it goes after I fly this weekend.
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Old 08-03-2006, 12:22 PM
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Default RE: mustang 40 size surpass 91

I have the wm dago red and I replaced the stock gear with a set of B&D retracts. I can't get them to stop bending on landings. I admit, some of my landings with this plane are a little "hot", but last wknd, I came in pretty fast, but more or less greased it and the gear still bent. The weird thing is that I have the same diam. struts from B&D on my F20 and have no probs. I know the Dago is quite a bit heavier, but is there any other way to prevent the bending? I get one flight and can't retract the gear anymore till I bend them back. I thouht about some Robostruts, but I don't think I want to invest much more $$$ in this arf.
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Old 08-03-2006, 12:48 PM
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Default RE: mustang 40 size surpass 91

there are robart landing gears that are very strong without the need of them being robostruts, simply the diameter of the rods is bigger. i've got a 40 size mustang with a 91 surpass which makes for a pretty heavy plane, a have the great planes landing gear, which are pretty bad if not the worse, however my landing gear bending is minimal. maybe your're coming in a little bit to fast. My landing struts have some forward angle that I applied to help then prevent from bending.
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