Ecalc questions

[Al M]

What prop constant is usually used for APC E props in the 10-12 inch dia. range? Also is it normal to use 1.25 volts/cell or would it be better to use something lower such as 1.1 volts/cell?

[Dick Huang]

Al,
For the APCE fixed props I use the following in E-Cal:
K prop =1.21;K pitch = 0.20; and K eff = 1.05. I don't use volts greater than 1.2. More importantly, the cell mohm determines motor run time and amps draw.
Dick Huang:)

[Gordon]

Dick

How did you arrive at those values? They are all quite a bit different from the original Ecalc figures of .90, 00, .99.

Gordon

[Dick Huang]

Gordon,
These numbers were derived from static test by cut and try matching of computed and test data of RPM,amps,volts,and static thrust. I offer it for what it's worth and hope some one else will do some measurements.
Dick Huang:)

[ejectionseat]

Hi all,
please take a look at this !http://custompaintjob.com/ezcalc/dma.asp
REGARDS;
0TTO:D

[vintage1]

Originally posted by Dick Huang
Gordon,
These numbers were derived from static test by cut and try matching of computed and test data of RPM,amps,volts,and static thrust. I offer it for what it's worth and hope some one else will do some measurements.
Dick Huang:)

I think the slofly constants should be even higher. Maybe 1.5 or more.

I didn't do the measurements myself, but took them from a test report on a plane in a mag, and the only way I could get close to the sort of RPM current and my estimated thrust figures was to go way up on the prop constants on the 10x7 slofly.