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Old 01-21-2014, 04:48 PM   #1 (permalink)
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Default 4 Blade Main Head: Shorter blades ok?

Hey, Freaks,

I am setting up a 500 with an Align 4 blade multiblade rotor head. I have setup mutliblades on 450s, using scale blades (the shorter chord blades).

I was wondering if it is better loading on the motor to use 4 x 450 blades on this heli instead of 4 x 500 blades? I fly it 6S.

Thoughts?
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Old 01-21-2014, 08:48 PM   #2 (permalink)
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You are missing some information to help us help you but let's go with what you have and then you can add as needed. A 450 helicopter uses, on average, 325mm blades and a 500 size uses 425mm blades. There is too much of a loss to use that short of a blade. You might be able to use 400mm blades but certainly no shorter than that or you will be beating the air with the blades and getting nowhere. You should spend some time reading build threads here to see what the fellows have done to make their helicopters more scale-like in appearance and operation. Head speed should be reduced quite a bit for a 500 size four blade head to something below 2000rpm. Align does not do anyone building their Blackhawk a favour by selling them the head and not informing them that they need to rework the gear ratio and motor KV. Once you get into larger scale helicopters, high rotor speeds are detrimental to the smooth operation and in some cases, 3D speeds can result in damage to the heads and a serious crash. Good luck with your build and take your time.

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Old 01-21-2014, 10:28 PM   #3 (permalink)
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I am flying 2 T500s both scale builds using 425mm blades and low head speed approx. 1600 and the fly great I drop them to 1500 once in a while
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Old 01-22-2014, 02:50 AM   #4 (permalink)
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As above. I would suggest at least 4x 425mm standard chord blades, or perhaps a set of Spin 425mm scale (narrow chord) blades.

I use 2x 465mm wide chord Spin asymmetrical blades on my 500 sized UH-1N and fly it at 1700rpm. The wide chord asymmetrical blades provide more lift and allow for a slower headspeed usually. One thing to watch is loss of tail authority - I run 2x 95mm tail blades to counter this.

Not a great idea to use the ESC to reduce headspeed. Better to get a slower motor and small pinion.

Your OP refers to shorter chord blades which would usually mean narrow chord (skinny) blades, but then you talk about 450 sized blades. Chord refers to the width, not length. Are you talking about shorter length or narrower blades ?

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