How do you tack a ducted fan? If you use a tack set to two blades do you multiply by two than divide by the number of blades on the impeller?

Greetings;

Sounds like the correct math to me. However, I think I'd just go to max then back off a bit. I haven't tried it on mine yet.
I'm not sure I can get an tach reading thru my Byro blaster F-15 anyway!


Good Luck,

Ramjet

You can put a stripe of reflective tape across the spinner and read it like a 2 blade prop. In 13 years I can't ever remember taching a glow powered D/F. I did tach an Electric D/F to compare 2 different motors. I set my inflight needle by going to peak (by ear) and then back of a little, looking for a good smoke trail. I always use a fuel with 23% castor/synthetic oil blend.

I have tach'd a Dynamax fan by painting a white stripe across the center cone with liquid paper. The best results were when the fan was exposed to bright sunlight. The contrast between the black cone and the white stripe was easily picked up by the tach.
I considered painting a stripe on one blade, but was worried that it would unbalance the fan.
Johnny