jinhusong wrote: ↑
February 19th, 2020, 7:54 pm
CookiePie1 wrote: ↑
February 19th, 2020, 6:22 pm
coachchuckaahs wrote: ↑
February 19th, 2020, 6:07 pm
On an Ikara prop, you carefully twist the spar inboard of the blades. Best with two needle nose pliers.
However, if anything more than small changes, it will break after 2-3 adjustments. So pitch them initially to get them the same, and pitch them to a range of pitches (separate prop for each pitch) rather than plan on adjusting multiple times to find an optimum.
what do you mean by twist? Are you rotating the spar along its own axis or bending it?
I will answer for him: rotate (twist) the spar along its own axis.
Strange, we need to dramatically reduce the prop pitch to match with the rubber came with the kits. Maybe the other extreme end also work? We will see after we receive the new prop.
Generally, as you increase pitch it will increase load, which for a given torque (given rubber width) will slow the prop down. Somewhere in this thread someone referred to "torque" as "power". It is not. Power is torque x RPM. The torque is driven by the rubber width (and the launch torque is set by backoff). The torque remains the same (with same rubber) regardless of prop pitch. So pitching up will slow the prop, which will reduce power, which may help limit initial climb.
If you over-pitch the prop, you may reach the point where you do not have enough power to climb. You may also over-pitch the prop and stall the blades, resulting in very poor power transfer, and no significant thrust.
In either case, more likely the first, you will find there is an optimum pitch for a given prop and rubber, where optimum in this case is the rate of climb or the total attainable climb. There will also be an optimum for duration (again, assuming same rubber). It is not necessary that the optimal pitch for climb also is optimal for duration. So, to merge these, you need another variable, which would be rubber width (or linear density, g/in). Now by adjusting both pitch and rubber linear density, you should be able to bring these two optimums together, so that you maximize altitude within the confines of your contest venue, AND maximize time aloft. Of course, this optimum will change for different venue heights. This does not even touch on prop planform, number of blades, etc.
The short of it is pitching up may help control initial zoom, but may be detrimental to duration if the rubber is not thick enough to provide enough power during letdown. The kit-supplied rubber is not necessarily optimal, it is a starting point.