Written by Rob Turnbull Thursday, 10 May 2007 00:00
This is a review of the SAB 620mm main rotor blades.
These blades come as a symmetrical balanced pair.
|Width||57mm at the root end - 56mm at the tip end|
|Blade grip size||12mm|
|Bolt hole size||4mm, with a fitted brass collar|
These blades have a quite distinctive look to them due to the 3 tone colouring. The majority of the blade is white with an 18mm wide carbon weave stripe separating that from the root section which is finished off with a metallic grey colour. The blade tips are slightly curved at the top edge and then taper out to a point on the trailing edge, giving that extra 20mm in length.
They are quite stiff when flexing from root to tip, with very good torsional stiffness. They also fit straight into the stock blade grips of a Sceadu Evo 50 without the need for spacers. Be aware that these are 620mm blades, not 600mm and as such may not fit on certain 50 sized helicopters.
Flight testing the blades involves 3D style flying on a heli setup with quite fast cyclics and using V Paddles for their extra crisp response.
These SAB 620 blades offer very good performance and give off hardly any blade noise (flutter) in 3D flight. They handle everything I can throw at them without me worrying that they're going to flex too much and strike the boom or something equally disastrous. There is still room for improvement here though, as there is an element of flexibility to them which should ideally be kept to an absolute minimum.
Being 620mm blades, they also can become a bit boggy in extreme pitch change manoeuvres. Full pitch pullouts are rapid, but can bog the heli down a little more than may be desired. This is where 600mm blades win out.
As far as autorotations go, these blades are great - especially when the wind gets up a bit. The amount of available headspeed at the end of an auto is stunning. I've managed to perform an auto with an aileron roll, medium paced descent to the ground and then hover above the floor for a good few, maybe 5 or 6 seconds, before the headspeed died off enough to necessitate landing! It was quite amusing at the time.
In sport flying terms, these blades are an excellent choice and will perform very well. The high demands put on blades in 3D flight are not present in sport flying and these blades will handle everything the sport flier will require of them.
Pros and Cons
|The finish of the blade looks and feels good|
|You do not need blade spacers when fitting to a standard 12mm blade grip|
|The blades are white, which can be easier to see in the air than black blades|
|They feel slightly boggier than 600mm blades in full pitch manoeuvres|
|They won't fit all 50 size helicopters being 620mm long|
I have had a lot of stick time on these blades now and I can definitely give them a big thumbs up. If you want decent 3D performance from your helicopter and have a mid range budget for main rotor blades, these blades should certainly make your short-list.
( 5 Votes )