Hi All,

A discussion regarding different propeller types was"hijacking" the JAS Integral thread, so I have started this thread to continue the discussion.

To recap / provide context -
- APC has a substantial amount of information on their website regarding prop design, testing, evaluation, etc.
- APC has a long history of proactively and continually revising/improving their propellers based on new science and field testing.
- APC has focused on an injection molding production process to provide very high quality, high performance propellers at a reasonable price.
- APC has produced propellers using carbon materials, but this has been very limited (to date) due to the substantial increase in production time and end cost to the user, and anticipated limited number of consumers.

Most would recognize the APC-E line of props as the most often used electric prop and certainly it is the most comprehensive line of props for electrics. In recent years, electric power systems have rapidly grown in peak power levels, and the stresses on props increases as well. As noted in the prior thread, there have been some motor/structural failures in pattern planes that were using APC props. Post mortem is often not possible to positively identify the nature of the failure and the contributing factors - which can be very complex when evaluating resonant frequencies of individual components and systems as a whole, especially when considering the wide variety of airframes, mounting methods, motors, props, and RPM combinations.

My history of testing/tweaking/conversing with APC regarding propellers for pattern applications began in the late 1980s when they sent out test samples of their initial propellers for the pattern market (I believe all NSRCA VPs received test propellers at that time). With the recent discussions about stronger propellers being needed for greater safety and/or improved performance, I exchanged some email with APC. APC does not monitor web forums, but is interested (as always) in feedback, and are currently evaluating several data sets regarding high power electric applications, and design/material improvements for future offering. From the CF laminating of APCs I've done in the past year (which APC has seen), APC has reviewed test data and (with an increase in weight of ~10%) can increase the torsional stiffness of the E props. Thoughts regarding, for example, a 20.5x14 weighing ~115 grams instead of 105 grams?

I have no financial interest in APC. However, I (and APC) am interested in gathering data for APC (to be compiled by me) for the purpose of improving APC props, which should provide a benefit to all us.

To that end goal, there are two types of data groups I can see that would be beneficial to have -
1. Any application (pattern or similar) in which an APC is not the best performing prop.
2. Any application (pattern or similar) in which a problem has occurred - structural failure of plane or prop, resonance, unusual noise(s) on ground or in air.

The more data, the better, including-
Prop(s) used
Age / number of flights on prop
Range of operating RPM
Motor
Mounting method
Prop mounting (threaded shaft, thrust collett, etc)
Spinner?
Fuselage construction
Logging data (ESC, Eagletree) or telemetry or timing/radar gun
Maneuver being performed

The intent here is to gather data (post to this thread, or PM to me), and find out what improvements can be made.

Jeff / Brenner, Certainly you know more than I from engineering/process/production perspectives, please feel free to jump in.

Regards,

Dave Lockhart