Propellors

[flyingdoc]

Anyone of a technical bent who can explain something for me.??

I have a Black Devil with a small frame and a 99cm aerobat 2 blade prop.

Starts easy, gets me off the floor great sounds ok, possibly a bit thirsty.

I just tried a really nice looking three blade scimitar wooden prop much like the parajet ones.

I was hoping for more thrust, less noise and hopefully a bit less thirsty.

Now I did get off the floor but the thrust seemed a whole lot less even on full throttle. The climb rate was dire and I was starting to get a little worried about clearing some elec lines near the take off zone. Sharp back track and land was definitely the order of the day. One thing I did notice was that peak RPM was severely down only 5000 to 5500, whereas I am usually in the top 6500 to 7500 range.

So unfortunately had to give prop back. But why?

Was the angle of the blade so much deeper and therefore the motor had to work harder to make it go round , hence lower peak revs?

Did the third blade just make the whole ensemble heavier and hence low thrust?

Would the carbon fibre/parajet one have much the same effect?

Is it possible to get more thrust or should I just stop tinkering with my set up and enjoy the airtime.........?

Would appreciate any and all opinions. Really like my rig so far, but still feel you can never have too much thrust????

Help please.

[Farmer_Dave]

Sounds like the prop needed gearing down a bit. You might not have gained much even then, But you might've gained a little. 3's do tend to run smoother. I've both 3 and 2 blade but they both run at the same gearing. The 2 blade has a steeper pitch to achieve this and they're both 130 cm diameter. The 3 doesn't give any more max static thrust than the 2 but it gives more at lower cruising speeds, so slightly better economy on a long flight.

It's a science, that's for sure

Dave