C_Roundy

Not to shabby for a Scale Warbird [X(], and it's engine only fires half the time too!

http://www.youtube.com/watch?v=i-aMbJEF4zs

soarrich

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What motor are you running?

combatpigg

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That's just plain gorgeous..!

It's strange to hear the low pitch sound do such a rapid doppler shift.

C_Roundy

YS DZ-1.70

C_Roundy

ThankYou combatpigg.
Yeah, her Bark pretty much echoes off the whole Sacramento valley. The sound always makes me think of a pissed off Harley top fuel dragster running around looking for the cylinder some a-hole lopped off. It would be alot of fun to fly her in a box canyon.........

In person the sound is more of a:

"BBBWWWWWWAAAAAAAAAAUUUUUUUGHGHGH BBWWAAAPP BUH BWAP BWAP BBBWWWWWWWAAAAAAAAAAAAAAAUUUUUUUUGHGHGH"

combatpigg

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Yep, they do sound like Harleys.
What percent nitro does it run..?
It doesn't sound soft and fuzzy like its burning low nitro.
The engine really fits the contours of that plane like it was made for it.

C_Roundy

My example of the engine seems to be happy on anything from 30% to 65-70% nitro, always with 22-23% CoolPower synthetic oil.
The day of this video I mixed the jug to about 50% nitro. 45-50% is where it starts to "Bark" loud and especially happy.

dasquirrelisme

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Thats a really sweet plane. Please tell me thats not a Hobbyking plane.

SrTelemaster150

From "The Secret Life of Walter Mitty", Ta-pokita-pokita-pokita-pokita

Rudeboy

50% huh... [X(]

That's badass

C_Roundy

No worries mate....

wyo69cowboy

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Very nice! What kind of pitch on the custom prop? Looked really fast; speed?

C_Roundy

The prop is 17" x 16" uncut out of the mold the way I'm flying it in this video, the engine turned it 8700rpm on the ground, and up to 10,300rpm in the air. It is a component prop (two blades bolt into an aluminum hub). The hub lets us shim the pitch up or down from there. In the video the guy holding the radar gun is calling out the speeds just so that the radar readings are recorded to the video too (169mph to 194mph). I'm flying in a 10mph crosswind which lowers the readings maybe 4mph though.

At full length and full pitch, the prop loads the engine a little more than optimum. Cutting an inch of diameter off will raise rpm by about 800, and raise speeds about 15mph.

Leaving it full length, and de-pitching it by one" will let our BearKitty hold about the same speeds as in this video, on the short, tight pylon course that she's built to race on.

Cutting it two inches, and raising the pitch one" will result in extremely high velocity out of a big dive, we shall see exactly how fast in the near future.........[8D]

wyo69cowboy

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Very cool. Thought I could here some speeds being called out, but couldn't make them out...

Might crack 200 out of a dive, huh? [8D]

soarrich

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Would you show some pictures of the prop? Please!

speedracerntrixie

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So I am guessing we will be seeing that Bear at Sams this season?

dasquirrelisme

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When I brought up the video on youtube it was showing some planes from hobby king so I was hoping it wasnt a chinese piece of junk. From the pic you posted looks like you molded your own. Your plane is downright badass and thanks for posting the vid.

iron eagel

Real nice work, and the flight results show just how well built and finished it is!
Beautiful airplane!

telejojo

I WANT ONE............................................... ...............

C_Roundy

Yep, with the prop clipped and re-pitch for that purpose, I can actually promise Waaay more than that.
Our Rare Bear is a very slippery 14 lb airplane and I launch with 24oz of fuel on top of that.
I believe it would exceed 200mph straight down with no prop on it . Heck, if I really needed to
massacre the holy mother of molecule mangling massive dive speeds, I'd load about 8 lb of lead on the C.G.,
and set the prop at about to something like 13" x 22". Picture the results, any volunteers to stand under it with the radar gun?
(By the way, the Bear would take it with no problem, carbon I-beam spars, etc. are your friends).

C_Roundy

soarrich, I'm more than happy to share what I can about the prop design, -but- at this stage thats not much. Here is a picture of the blade planform, next to an APC 16 x 15. Set to it's (nominal) 17 x 16", this prop turns slightly more rpm than the APC.

The prop design work is about 95% my partner's, and the tooling work is 100% his; Not to even mention the $15,000 he ended up spending on his new C.N.C., 3 axis, vertical knee, milling machine so that he could make the molds with the required accuracy.
Also, we are prooobably going to offer the props for sale to the racers in the future (in a diameter and pitch optimized for their beloved YS 1.15s), and it would'nt be prudent to let the design out before we're putting props in their hands.

All that aside, I can tell you that the prop is certainly not pure freakin' magic, just existing technology very, very strategicly applied.
I.E.: pitch distribution, and airfoil distribution, etc., as well as the simple fact that one can achieve MUCH thinner, sharper, lower drag airfoils in a carbon prop than other materials). By the way, the blade in the picture is 100% uni-directional carbon tow, its just a lay-up test blank. The flight props are sandwiched in carbon cloth on the outside so that they have extraordinary torsional strength and rigidity, as well as longitudinal strength and rigidity. They actually ring like a bell......

Best Regards, Chuck Roundy

C_Roundy

Yup, we're there just about every Sat. or Sun. while we're testing prop combos. OH, Wait, you mean racing season don't you [sm=tongue_smile.gif]!
I don't know, I might actually put my Rare Bear on the course with you Gold guys once or twice later in the season, but there are a couple things about that. For one thing, while Bear does handle absurdly sweet & friendly in the air, and its already doing effortless breakout speeds, by the time we settle on the pitch / dia. optimum for the course, it will be going silly fast for that short course. So I'll need to get a good bit more practice around the poles before I decide I'm dialed in right for putting that big heavy mutha' in traffic with spectator crowds there....

C_Roundy

On behalf of my partner FiberFlite and I, Thankyou (and you other guys) VERY much Sir!!![sm=49_49.gif]

Best Regards, Chuck Roundy

freakingfast

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It's lookin real good Chuck. I haven't been out to the field yet this year. hope to see (hear) it fly.

combatpigg

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The prop really looks like a toothpick in that last shot.....!

I'd have to have a couple drinks just to work up the nerve to taxi that bad boy.