315, 325 or 335 Blades

[Cralis]

Which blades? For hovering and learning?
I would assume 335 would give more lift, and use less battery and be more stable, but.. heavier, so less flight duration?

[robgt]

For hovering and learning, stick with the 325 pro's - they're about a tenner a pair and therefore cheap to replace if you crash it.
Cheers,
Rob

[Cralis]

I can get the 335 Pros for a minimal amount more. Are they better, or stick with the 325s?

Also, instead of the long default antenna with the trex, is the 'Micro Antenna (Base Loaded)' any good?

[robgt]

I can't speak for the 335's personally as I've never seen them.
I note that you have a trex450 SE, so the blades should fit ok as you will have the longer boom fitted (no chance of the main and tail blades colliding).

Some base loaded antennas are fine - I've heard of some people having issues with some too though. If your standard antenna is not causing any problems, I'd leave it alone.

Cheers,
Rob

[marktigere1]

I've just fitted some 325 pro's to my 450 XL and they are as smooth as silk.

No balancing required and now track like a razor blade.

Cannot fault them really although I have only hovered them.

Cheers

Mark

[Cralis]

How does the maths work here?
Longer blades = more lift = more stable (Not as twitchy, as you don't need as much power)?
But .. longer blades = heavier to turn, and more wind resistance?

Also, another math-sy type question...

When hovering, a large majority of the power generated by the blades are being used to hold the heli up - balancing on air. When you use forward motion, the power shifts. I believe when you start moving forwards, you get lift. But, doesn't that go against phyisics, in that you're now using less power for lift, as some is being used in forward motion?

[robgt]

Imagine you're holding a fan in your hand pointing it at the floor. The fan is pushing air down towards the floor. If you point the fan slightly to one side, the air will be pushing in the same direction as far as the fan is concerned (the fan only ever pushes air through itself on a straight line), but relative the the world, it's on an angle now. If the fan was strong enough, and not tethered (held in your hand) it would move in the opposite direction to the flow of air.
Gravity will always try to pull it to the floor, so once you tilt the fan to direct the air where you want it to go, the fan is no longer directly fighting gravity to sustain it's position (if it were strong enough to do that in the first place) and should start to fall.
On a heli, when you tilt the rotor disc to move forward, the heli will start moving but descending too, unless you add some more pitch to make it climb a little (to compensate) and keep it level.

Complex question with an over-simplified anser
Cheers,
Rob

[Cralis]

Right, I see. So it does drop when you go forwards. I was under the impression that you gained lift as you moved forwards. Hence, why you would take off into the wind. I guess taking off into the wind just aids lift, but because you're not using all the rotor power for lift anymore, the heli still drops....

I think I see...

[robgt]

So it does drop when you go forwards

Yes, if you do not adjust the pitch, and just introduce forward elevator, the heli will roll forward into the ground.

As you mentioned - wind (atmospherics in general) does make a difference, but thats getting into complex aerodynamics...

You adjust the pitch of the rotor blades to affect the amount of lift produced and use cyclic to direct that lift.

You don't have to take off into the wind, but it can be easier to do so.
Wind underneath the rotor disc will help with lift (it can lift you up all on it's own if strong enough) - whereas as wind on top of the rotor disc will push down insead.

I think my head may explode...
Cheers,
Rob

[Sesame]

just to add we all practise when we start hovering into wind as this also helps keep the tail pointing towards us, when you start hovering tail into wind, it does move about a little with the gusts, but its another thing to get used to doing, makes you a better pilot in the long run.

[moyesboy]

The woodies are fine for learning only problem is they are limited to 2400 so the heli is slightly less stable.
You can run the pro woods a lot faster (People are running them a lot faster despite the 2400 warning on the packet) which makes the heli stable. These blades are wood but impregnated with resin and thus stronger.

The length doesn't seem to make all that much difference to duration and power required to hover. There is as much difference in the different blade brands the same length.

My 315 radix have survived two crashes which would have wrecked the woods and cheap carbons I used before. So over break even for investing the 30 quid in them. however maybe the blades surviving bent main and feathering shafts that might have survived otherwise!

Align 325 is 315 to bolt hole which is same as the radix. the blade measurements are confusing as some are to bolt hole and some are overall length with no common standard.

When the heli tilts to start moving it loses lift so more collective is required (this is in fact the pawer that is accellerating the heli). Once the heli is moving then you get translational lift from the rotor disc which allows the power to be reduced so it takes less collective to stay level when the heli is moving.

The translational lift from the disc is a simple way of looking at it. its actually the lift is increased over the blades on average although airflow is slowed over the backwards moving blade and speeded up over the forward going blade with amny other complexities.

Its the same thing as with a fixed wing. moving the rotor disc through the air is a more efficient way of producing lift than with it standing still, in the same way as using the prop to move the wing through the air is more efficient than hanging directly on the prop in a torque roll.

Also when hovering the heli becomes the centre of its own vortex. Imagine a smoke ring with the heli in the middle. The middle of the ring has air going downwards, the outside of the ring has air going upwards. Now the air can just keep travelling round that ring and it is a stable set up. with the air just flowing round like that the heli has to work harder to stay up as the air is already moving down in the middle of the vortex.
This vorex is suppressed by the ground when the heli is low, but forms when the heli is up a bit - thus the heli needs less power near the ground.

Once the heli is moving then the stable vortex is distorted and new air that is stationary keeps entering the rotor disc so the rotor has something to work with that is not already moving down, thus less work is needed from the rotor to keep the heli up.

now imagine a normal wing that is dagging a smoke ring type vortex along with it. This is what is actually going on with a wing. The wing marks one edge of a very distorted vortex ring that you can recognise spilling off the ends of the wing. Those two straight vortices spilling off the end the wing tips actually meet to close the circle an infinite distance behind the wing.

Hope you are all entertained and suitably confused by now.

IF your head explodes next time you hover your heli then you probably got a bit to close

[robgt]

Excellent post Gordon
I was trying to apply the KISS principle - you did a far better job than I
Cheers,
Rob

[moyesboy]

KISS principal? What's that?
try that on me and I'll have to hit the red card!

[Cralis]

Incase you're serious: KISS=Keep it Simple Stupid

Incase you're kidding: Ignore this posting.

[robgt]

LOL
Cheers,
Rob