James Canova
  • Vancouver, BC
  • Canada
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About Me:
Long-time interest in flight, space and R/C modelling. Currently living in British Columbia, Canada.

Moved to electric r/c from gas a few years ago before the new lightweight Li-Poly batteries available. Prompted me to start measuring propeller performance data and write software for analysis of powertrains.

Interested in control theory and long endurance flights.
Hometown:
Vancouver, British Columbia, Canada

James Canova's Blog

Matching powertrain components to suit requirements (www.flightsolver.com)

Posted on December 11, 2007 at 3:08pm 2 Comments

Since I started flying r/c airplanes in the mid 70s when I was in high school I always wondered about the selection of propellers and glow engines for a particular airframe.



After a long break from r/c, I built a couple of electric powered models in 2000. Neither model flew more than 20 feet off a hand launch until, after trial and error, I found correct combinations of propellers, gearboxes, motors and batteries.



Not happy with the trial and error method, I wrote analysis… Continue

Comment Wall (5 comments)

At 11:00pm on December 11, 2007, Howard Gordon said…
James -

I have more than a few APC's. When I first started this project, I tried a large number of prop and motor combinations, and found the APC thin electric props to be the more efficient than most alternatives over a fairly large range of sizes. I'd be interested to see how this stacks up against your data.

Where I don't have good data is how to efficiently combine fixed pitch coaxial props. I know that the lower prop needs to be higher pitch than the upper prop because it's seeing higher incoming air velocity, but given the limited options in pusher props, I haven't really been able to explore many combinations, and would welcome suggestions.

Howard
At 12:20am on December 13, 2007, Howard Gordon said…
Thanks for the lead. I haven't yet located that specific paper, but I'll continue to look.

I've been using 12x6 for the upper prop and 12x8P for the lower prop because that's the best in tractor/pusher combination I found. The lower prop needs to have a higher pitch because it is moving through an accelerated ariflow caused by the upper prop. I don't have a model, but imagine there are some parallels with multi-stage compressor or turbine design.

I need to run some tests with my current coaxial setup to measure efficiency. My earlier design, which was a lot heaver, was getting 8-9 grams of thrust per watt, which actually wasn't bad. The current setup is a lot lighter, and I expect the efficiency to be somewhat higher, but I really do need to take some measurements.
At 2:07pm on December 14, 2007, Mike Mc Smith said…
Hey there....

:@)

Kirrie is a small place - I was at school same time as stuart-

I think morag is doing really well- my mother meets her more frequintly than I do.

How do you know the family?

For reference we are the smith's from east hillbank-
if there is any struggle when trying to explain.

I have no technical question to tax your expertise yet.
Shame.

But I've just started building a multiplex cargo-
Should be flying next week some time.

Anyway-good coincidence.....

Cheers- mike
At 1:53pm on December 15, 2007, James Canova said…
Hi Mike,

What a coincidence. The Cable's are relatives on my mother's side. I just spoke to my mom to figure out what the relation is. I think, roughly, my mom and Morag's late husband are third cousins. My mom is over this side of the world because her grandfather immigrated to Canada from Scotland in 1906.

I've met the Cable's a few times. I was in Kirriemuir in 1972 and 1989 and then Morag and Jackie came to visit my parents a few years ago here in Canada (Victoria, BC). I met Stuart and Jackie when I was there in 1989. Stuart was quite young, maybe 11 and Jackie was still at University, Harriet Watt? I think that was the name of the University.

In 1989 I had just moved myself to England and was looking for a job - I returned to Canada in 1999.

My mom keeps in touch with Morag. I'll pass your name on to my mom so she can mention that I have spoken to you on email when she speaks to Morag next.

Let me know how your multiplex cargo works.

James
At 4:51pm on December 18, 2007, Howard Gordon said…
James -

I just dug out the notes from the tests I ran. I was testing much lighter loads - generally around 100g or 200g - and I noticed that efficiencies dropped off as the load increased, especially with smaller motors.

The best numbers were found with the combination of an APC 10x5 and PJS motor (AC22/7) - 9.4g/W @100g and 8.2g/W @200g. The larger Hobby Lobby SK400XT yielded 9.1g/W @ 100g, but maintained 8.5g/W @200g.

I didn't test any pushers, and I didn't experiment with a wide range of pitch ratios. I really do need to measure the current draw of my latest coaxial to see how it compares in efficiency.

Howard

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