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Old Mar 08, 2013, 08:18 AM
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Mexico, QRO, Santiago de Querétaro
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Question
HeliArtist 425 Carbon 5 set scale rotor blades

Hi guys,

as anybody tried this ones,

http://www.heliartist.com/showroom/h...pcs-p-203.html


I recently recieved a set, but until now im checking them, and they have different weight and dif. center of gravity location. The heaviest blade is 40.1 gr, and the lightest is 39.4gr. Th other 3 are 39.6 to 39.8gr. 3 blades have the center of grav. almost in the same place, but the other 2 are off by 5mm. The weight issue can be corrected, but the difference in the location of the center of gravity, is something i have to fix, or i can leave them like that?

Thanks.
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Old Mar 08, 2013, 11:26 AM
Complete RC Idiot Savant
The Netherlands
Joined Nov 2009
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With a likelyhood, bordering to certainty, the lightest blade has the centre of gravity the most outward, and the heaviest blade has the centre of gravity most inward.
In that case most likely there is nothing to worry about.

If you want to know for sure: Measure of each blade the exact weight, and the exact distance from the rotorshaft to the centre of gravity of the blade.

Calculate for each blade "distance multiplied by weight" and this figure should be equal for all 5 blades. If that is the case, the blades will be in balance when fitted on the head.

For example, a blade weighing 40 grammes exactly and having a CoG distance of 250 mm would balance with a blade weighing 39.5 grammes and a CoG distance of 253.2 mm because (40 x 250)/39.5=253.2

Mind you, you need to use the distance from CoG to the centre of the rotorshaft, as fitted on your rotorhead, NOT the distance from hole to CoG

Brgds, Bert
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Old Mar 08, 2013, 05:55 PM
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Great support Bert! i will try this later. Thanks.
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Old Mar 08, 2013, 07:27 PM
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This are the numbers i got,

b1: 39.5gr dist. 291.2 total: 11502.4
b2: 39.8gr dist. 290.39 total: 11557.522
b3: 40.1gr dist. 290.5 total: 11649.05
b4: 39.7gr dist. 285.6 total: 11338.32
b5: 39.7gr dist. 285.6 total: 11338.32

The heaviest blade (b3) have the most outward cog, so if i take 40.1 as max reference, adding weight to the other blades to match the final number of b3, only the b2 and b1 have no problem, but with b4 and b5 i dont get close to 11649. Adding weight on the tip on b4 and b5, that will add weight and at the same time it will move the cog outwards, right?
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Old Mar 08, 2013, 09:36 PM
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I added weight on the cog on b1 and b2, a single piece of electrical tape of 0.3gr, and a little bit more on b1. Now b1, b2 and b3 are balanced.

The cog on b4 and b5 is closer to the root of blades, so i added tape en the tip to move the cog closer to tip. But i have to add 6 pieces of tape, one next to the other, going form tip to root, just to match the cog with b1,b2,b3. It doesnt look nice 6 pieces of tape on the blade. It is ok to put tape on the tip? i read that is not recomended.
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Last edited by Felipe79; Mar 08, 2013 at 11:47 PM.
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Old Mar 09, 2013, 03:35 AM
Complete RC Idiot Savant
The Netherlands
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First of all, it shows an unbalance of around 1.5% which should not be too much of a problem.
My first action would therefore be, to fit them on the head, and first carefully spool them up, adjust tracking and see how they do.... Because I have not much experience with HA blades but the sets I have seen worked straight out of the box.

You can also try and balance by very carefully removing some material from the tip or from the trailing edge.

Adding weight can also be done by carefully injecting some resin in the tip or adding some clearcoat.

What I used to do was analyze the numbers to see what needs to be done.
As you can see b3 has the highest value, and carefully removing some material from the tip would both lower the weight and bring CoG more inward.. so a little goes a relative long way here.
Opposite on b4 and b5, too light and CoG too much inward: Dipping the tips in clearcoat for one or two cm would not harm aerodynamics, but bring those blades a bit closer to the rest, and I'd say if you could manage to bring b3, b 4 and b5 in the range of 11500, you would be good to go....

But before you do anything: review your measuring methods, because I did not expect this outcome.
Make absolutely sure, that determination of CoG is not influenced by any airflow in your hobbyroom or workshop.
Make sure the weight is measured correct, bij weighing the same blade multiple times and taking the average.


Brgds, Bert
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Old Mar 09, 2013, 07:50 PM
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Hi Bert,

i got those results doing this,

the distance from center of rotorshaft to blade grip screw is 72mm. From there to cog of blade 3 for example, is 218.5mm. So total distance is 290.5mm. Multiplying that with the weight of 40.1gr i get 11649.05. With this you get momentum, right? maybe the units are wrong?

The first pic shows blades 1,2 and 3. Balanced, with cog practically at same place, weight of 40.1gr. Just have to add a piece of electrical tape of 0.3 gr to blade 1 and 2.

Second pic shows blade 3 on top as reference for cog, and below is blade 4 and 5. This two have their cog to the right of the cog of b3 at a dist. of 5mm. The two marks on b4 and b5 show their real cog at the right, and the mark on left is where the cog should be to match b3 cog.

On 3rd pic is b4 on the balancer, with added weight to match the cog of b3. I have to add 4 pieces of tape as shown in the pic.

On 4th image show the weight of b4 with the added tape. Now is 40.8gr. So i will have to add two pieces of tape to b1,2 and 3 to match weight. All blades with tape on them, that doesnt look nice.

I will try your suggestion of adding a clear coat. How much weight you think will add a layer on the tip zone?

Thanks.
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Old Mar 10, 2013, 02:30 PM
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Whatever you do, you can of course not fly with the tape applied like that.

I have no idea how much one layer of clearcoat will add.... that depends on the thickness of the layer, and the length to be coated.

Maybe I am kicking in an open door here, but leave one blade unchanged: that will be your reference blade.

Just comes to mind: you can just select one "reference blade" and balance each of the other blades with that reference blade on a teeter or blade balancer.

As long as you leave that reference blade unchanged, you should end up with 5 blades with equal momentum.... And that is all there is to it....

Brgds, Bert
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