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Russell Peitz
01-13-2013, 07:37 AM
Hello Everyone,

I have a One Design DR-107 with a Prince Aircraft P-Tip Wood/Carbon fiber Propeller. Was thinking it is pitched to fine and wanted input from others.

At WOT I'm getting: (verified off a digital tach & a/c tach)
Static- 2300rpms
120mph- 2700rpms- engine redline
200mph- 3250rpms- Vne

I'm sending the prop in for an inspection/overhaul and now would be the time to repitch if I'm going to.

The prop feels a bit draggy at higher speeds/higher rpms, and as my neighbors will attest it is quite loud!

Thoughts?

Russell

WLIU
01-13-2013, 08:18 AM
Hello Russ,

You might change the pitch a little, but for your airplane you want lots of pull going up, and drag going down is a good thing. Your wing is designed to have a rapid drag increase with speed to allow for doing a snap or a roll on the vertical down without exceeding the airframe red lines (too much).

For an aerobatic aircraft with a fixed pitch prop, most pilots consider the 2700 engine manufacturer's "red line" advisory. Ask around and find out what the S-1 drivers see as max engine RPM. I will guess that 2900 is common and 3100 is not uncommon. You aren't going to get 2000hrs from that engine anyway.

Best of luck,

Wes
N78PS

flyrite
01-13-2013, 11:32 AM
Russell I had the prince on my 1D when I bought it . I when thru several prop combo's till I settled on a 3 blade Catto .

You might join the "one design forum" on yahoo , the subject of which prop as well as whats the best pitch- Diam. has been covered well over there .

RetroAcro
01-13-2013, 05:12 PM
Russell - fixed pitch props are a tradeoff and there are too many variables to say what pitch is best. With the 1D, I assume you simply want best aerobatic performance for (eventually) Intermediate and Advanced level sequences? But even that depends on how fast you're willing to turn the engine. I went through all this stuff in switching from a metal Sensenich to a 3-blade Catto. Started with a 72-56 Catto and ended up with a 72-54. In the Pitts, I feel retaining higher RPM at lower airspeeds (to a point) is the most helpful in getting through Advanced sequences. The first 56 prop turned 2350 RPM on climbout (100 IAS), and the 54 turns 2500. It also has better low speed acceleration, even if it loses a few MPH on the top end. The Pitts is so draggy, that I feel low speed thrust is more valuable than top speed. Top speed, level flight @ WOT is 160 mph IAS @ 3,025 RPM. With the 56 prop it was 165 IAS @ 2900 RPM. But both props achieve the same vertical penetration from top speed, level flight - but the 54 prop does it from a 5 mph slower entry speed. It sure feels like this makes a difference when flying the sequences. But my max RPM is well over 2700 RPM at times. Hard to say, but if I observed the 2700 RPM redline, the 56 prop may actually work better. But then it would be hard to fly this airplane well in Advanced with a 2700 RPM limit. :-)

Not sure what Catto dia/pitch Flyrite uses, but I'm half considering selling the 56...or keeping it for back up. Not sure. The nice thing about working directly with Craig (Catto), is that if you're not happy with it, he can do a minor repitch...or will try to work with you until you're happy. He makes a great prop and stands behind them 100%.

RetroAcro
01-14-2013, 08:03 AM
The prop feels a bit draggy at higher speeds/higher rpms, and as my neighbors will attest it is quite loud!

Sounds like you feel your prop may be pitched too low? From your numbers, it appears you are getting good RPM (HP) out of the engine. That will help you pull through high-energy figures in Advanced. In competition, you don't always have the luxury of diving to Vne for the next figure, and you must start the next figure with whatever level flight speed you exited the previous figure with. Regarding ideal prop pitch for how you intend to fly the airplane, it's probably best to talk to other 1D drivers. I have a friend who flies one in Advanced. PM me if you'd like his contact info. I think he's running a Catto now too.

Russell Peitz
01-14-2013, 01:20 PM
The prop is 76x56. Spoke with Lonnie Prince at Prince aircraft propeller at length about this. Usually they do a 58" pitch on a 1D. Although they state the prop is designed for 2700rpm only, he did say in their testing they didn't start shedding wood pieces until 4500rpms! I think I will fly it for the year, get to know it better and then decide if something else is needed.

Thanks everyone,

Russ