Balancing 5 blade head - Solved

[Trooper7]

I looked around but couldn't find much guidance for balancing a 5 blade head. So I took what I knew from 2 blades and then some common sense and good judgment. When I was done I had a beautifully flying heli. (I'm using Spinblades and I can't say enough good things about them - came out of the box within 0.02 grams of each other and CG's within a 1mm - Impressive)

So here's what I came up with:
- Disassembled the head.
- Spun the empty hub on the Dubro. No balance issues here.
- Weighed each feathering shaft. Surprising amount of variation here. Noted each.
- Weighed each Blade grip with all bearings in. Variation here as well. Noted each.
- Took heaviest shaft and lightest grip and matched the rest accordingly. Maybe dumb luck but that put them all within 0.1 grams of each other.
- Assembled head placing heavier grip assemblies opposite each other and put on Dubro...darn near perfect balance.
- Attached blades.

This is where I was surprised. I was expecting it to be perfectly balanced considering how close the blades were but it had a definte heavy side.

- I numbered the blades. 1 being the heaviest.
- I aligned the blades by setting them to 90deg pitch (held in place with elastic-band) and then paralleling each blade to the edge of the bench. With the big blades(600mm) they needed to be perfectly straight WRT the hub or it will throw things off.
- Looking at the rotor assembly from the front as it sat in the Dubro I put The No.1 blade at the 3 o'clock position. Obviously it fell to 6 o'clock so I added equal amounts of tape (at the CG of course) to blades 3 and 4 as they are the direct opposites until No.1 stayed horizontal.
- Then I placed blade No. 2 at 3 o'clock. I added tape to 4 and 5 till it balanced.
- I repeated this process for each blade until all were balancing horizontally. Some blades had multiple pieces of tape so I removed those and then made one long piece the same total length and reapplied it.

It took a while but the results were amazing. There is nothing more satisfying than a bird with virtually no vibrations. And with the pitch of each blade set to with 0.1 degrees tracking was bang on as well (Spinblades - worth the money I'd say)

So that's how I did it. Hopefully it will help someone else delving into the world of 5 blades like me.

[Jim Hansen]

Nice work, in the real world we take the 5 ,6 :0r 7 blade.
Blades come close to the same weight.What we look for is hover hover load
hover load then at speed because when you have more the one blade you get one or two that will not fly together ie one climbs or two dives or simply put will not fly together. But in full scale you have trim tabs to take care of that.Any my 2 cents. Good job Trooper7