prop selection methodology

[Ragwing nut]

Re: prop selection methodology

I was hoping Mike Redpath would join in with some of his actual knowledge on the subject..
JH

I just typed up a huge response and got erased somehow when I hit the post button. I will try again later when I more time

[Ragwing nut]

Re: prop selection methodology

let me try this again. Prop selection from airplane to airplane is really a black art when dealing with fix pitched props. What works great on one, does not always work on another, and one persons needs is not always the same as anothers. To further complicate this, not all manufacturers use the same blade profile, or measure the advertised pitch from the same point on the blade which is generally around 75% chord length, but can vary. Throw in operating altitude and just completely changed the requirements of your propeller needs.

Couple truths have already been mentioned above. Flatter pitch will climb better, which requires longer blade to absorb rpm so as not to exceed redline, thus coarser prop to offset a shorter length for cruise. Metal props are more efficient than wood due to them not moving underload like a wood prop does. Wood props will change shape and even blade angle sometimes. Max efficiency on any prop is roughly 85%, wood props are normally in the 70's.

Best thing to do is start with what you currently have, and ask yourself some of the questions above. Do I want climb or cruise, wood, or metal, what altitude do I operate out of, and fine tune your selection from there. I have flown many taylorcrafts with many diffferent engines, from 65, 75, 85, o200, o235, and i think I could put a 71-48 mccauley on almost all of them (except the 65) and be happy, but then again that is just me.

[flyguy]

Re: prop selection methodology

Excellent summary above. Choose by other people's experience according to aircraft and engine. Tweak to your specific needs.

I have a 7146 on an 12D-85 and it goes just to redline,full throttle, level flight, and climbs and cruises excellent. I had a 7446 on a 12D-65 and it was a good all-around performer also.

Darryl

[N96337]

Re: prop selection methodology

Thanks Mike! It's nice to hear from someone with manufacturing "knowhow"!
John