View Full Version : Thinking 320mm is too long

05-26-2006, 04:24 AM
I recently changed from SAB 305mm main blades to 320mm SABs. While I like the added stability, I think the motor is working to hard to spin the bigger disk. I have said in the past 305mm is the best size for a 400 size heli. I still think that is correct.

The most notable improvement when running the 320s is when coming down from up high. The heli tends to drop straight down when the left stick is pulled back. With the smaller rotor disk, coming down is an adventure as the heli tends to slide from side to side.

However, the sound of the 320s chopping the air is much nicer than with the 305s. The 400 sounds much larger with 320s on it. I like that. :wink:


05-26-2006, 04:27 PM
I'm flying the Align 315s. The cheaper ones. They say "315 CARBON" on the blade, but I believe they are actually just carbon fiber reinforced plastic. They cost about $18. Anyway, they work great for me. As you mentioned much more stable coming down. I'm using an AstroFlight 803T motor with an 11t pinion.


05-26-2006, 10:16 PM
I'm flying the Align 315s.Align measures their blades from end-to-end. Most others measure from the middle of the screw hole to the tip. This means Align blades are actually shorter than most others of the same specification.

So, Align 315 blades will actually be about the same length as SAB 305s.

Anyway, I have flown most of the Align blade types and find them quite good. However, when you put on SABs (and I assume other high-end blades), you really notice the difference.

By the way, 305s came down much better than the 280mm (woodies) did. I assume a longer airfoil will usually be more stable in a glide (which a heli is in when droping, sort of).


05-27-2006, 11:37 AM
I am running Align 305 woodies on the factory MX400Pro motor, 14T gear and ESC with an Apex 2100 3S 15C, pitch is -2 to +8, head speed is around 24 to 2500 in hover and set to 100% at full stick.
I am having two problems:
1. Maintaining any altitude in a hover out of ground effect, the heli is very sensitive to minor pitch/ throttle inputs, just a nudge and climb or descent is initiated but arresting either requires a large stick deflection. I have checked for binding in the pitch linkages and found none.
2. Slowing from a moderate descent rate (1.5 to 2 foot a second) to hover requires using full throttle.
I thought possibly the lager blades were the issue so I installed the factory 280 blades and got the same basic result with less stability.

06-27-2006, 11:53 AM
Increase your pitch to +10. Your heli is probably hovering around +6 right now. You don't have much extra pitch with the +8 (max) you currently are using.