Originally Posted by Vicarious

Got 2 vids of different X-41 speed passes to check:

On video #1 the top speed was 84 mph

On Video #2 the top speed on pass #1 was ~115mph and the remaining passes were ~108mph.

The problem I am having dopplering both of these videos is from the doppler graphs I see, it appears the model must be diving first then leveling off (can see it in a couple passes) and that is messing with the approaching frequency and puts a bump in the approaching frequency making it hard to pick the correct approaching frequency. This is more apparent on video #2 and accounts for about 5+ mph. So If you want to get a more accurate speed, I would suggest passes with about 2-3 seconds flat and level coming and 2-3 seconds flat and level going away then the readings will be much more reliable

Don

40mm electrolyte runs.....work your magic don!!!!

about 65 deg. up and down wind passes

6 blade fan

Electrolyte speed pass (1 min 28 sec)

and my dons bi3600 powered RCL cougar...

4.25lbs RTF weight...HET fan. 4s 5000.

Corsair Nut's rclander cougar (3 min 3 sec)

Originally Posted by corsair nut

40mm electrolyte runs.....work your magic don!!!!
about 65 deg. up and down wind passes
6 blade fan

I got 74 upwind and 94 downwind, so 84mph average. That was on the first two passes (0:30 and 0:47) the other ones I had trouble seeing as it is quiet and the background/wind noise was not helping.

Don

Originally Posted by corsair nut

and my dons bi3600 powered RCL cougar...
4.25lbs RTF weight...HET fan. 4s 5000.

I got a 100mph and 95 mph, Nice! Once the turbine got into the air it pretty much messed up any readings afterward since he was flying past you when you were coming by the camera. I have two 70mm kits coming I got from Nitroplanes, the Airfireld Mig-15 and the Airfield F-16. I was thinking of trying the BI-3600 in them.

Don

thanks don!

couple more electrolyte passes..

Electrolyte doppler pass (0 min 21 sec)

Those average to about 79mph.

Don

thanks don!!!

OK let's try this again... now wind noise may be a concern, but hopefully you can get at least one measurement

The clip is edited down, 4 passes back to back with me calling direction AFTER the pass was made

http://www.vimeo.com/17266864

The first two passes were the best, they averaged to 67mph (61mph upwind and 73mph downwind).

Don

Originally Posted by The Don

The first two passes were the best, they averaged to 67mph (61mph upwind and 73mph downwind).

Don

Thanks! Not quite what I was hoping for but not shabby either. Btw it was about 40 degrees out, not sure what impact that has?

I think I need to get a newer/higher C battery. Maybe that'll get me into the 70's.

Originally Posted by habitforming

Thanks! Not quite what I was hoping for but not shabby either. Btw it was about 40 degrees out, not sure what impact that has?

I think I need to get a newer/higher C battery. Maybe that'll get me into the 70's.

You might try an uncut APC prop as well. APC props lose efficiency pretty quickly when they're cut down due to the way they're shaped.

Originally Posted by habitforming

Thanks! Not quite what I was hoping for but not shabby either. Btw it was about 40 degrees out, not sure what impact that has?

I think I need to get a newer/higher C battery. Maybe that'll get me into the 70's.

What motor prop setup are you running?

Originally Posted by Tres Wright

You might try an uncut APC prop as well. APC props lose efficiency pretty quickly when they're cut down due to the way they're shaped.

Good to know. I've got 2 more props but didn't have them reamed & balanced so I elected to go with what I had that day. I'll do a fresh run next time the weather is good with a new prop.

Originally Posted by The Don

What motor prop setup are you running?

Wicked Jr 3200
4.1x4.1 (except it was chipped so trimmed/rebalanced to 3.7x4.1)
Pentium 30
Flightpower 800mAh 20C lipo

I get about 23,000 static RPM, slightly more on a larger 30C battery (~25,000).