General Blade balancing

[D.O.G.]

When it comes to balancing blades, how much is to much tape? I have one blade that weighs 23.1 grams and the other blade is 25.6 grams. I applied tape to one of the blades and I'm only 0.2g off which is not bad but to me it looks like to much tape on the blade. Can I use it like that or not? They're matching brand name RJX 325mm blades.

 

[Tony]

If these are high end blades, I would be taking them back. They should not be that far off. But, you can use as much tape as you need as long as it's not going to come off in flight. If I have a cheap blade that needs a lot of tape, I just use vinyl since it's heavier and looks a little better. And also can be used as blade tracking tape.

 

[D.O.G.]

Thanks Tony. The reason the blades are that off is because I purchase them at different times but from the Same place and same brand. I try to keep the same brand blades for each heli just in case of an accident.

 

[Tony]

Ah, copy that.

 

[KLA]

That is a pretty big difference in weight, but since you bought them at different times it is understandable. Instead of putting a bunch of tape on the lighter blade, can you clip the corners off of the heavier blade and sand them smooth to bring them a little close in weight? I have done that before and it worked good for me.

 

[Tony]

How are you balancing the blades?

 

[KLA]

I balance blades with tape but if his blades are off as much as he said then it's gonna take a LOT of tape. That's why I suggested to clip a small corner off of the heavier blade to bring the weight close to the other blade then finish off with tape on the lighter blade.

 

[Tony]

There are different ways of balancing blades. You can do the very methodical method of weighing each blade, then setting the CoG of each blade and then setting the moment of force. Or you can just do the moment of force balance method (teeder todder).

If doing the first, try the second. If doing the second, try the first. Just a little experiment. Even though the blades don't weigh the same, they could balance out on a cheap blade balancer and will be fine. It's what's known as Moment Of Force and the CoG of the lighter blade being farther out to the tip can offset and actually balance against a heavier blade with the CoG closer to the root. Hope this makes sense.

 

[KLA]

Makes total sense and you are exactly right. It's just hard to explain in a way that most people would understand, so I didn't try. But, you couldn't have said it any better.

 

[Smoggie]

If you need to add weight to the tip you can drill a small hole from the bottom surface just in from the tip and put some lead shot in there, glued with epoxy. Smooth the epoxy off and put a blob of paint on and you would hardly know. This is only safe at the tip though, you dont want to go drilling holes anywhere else on the blade!

 

[KLA]

Ahhh, just go for it!!! Make it look like Swiss cheese, it will be fine! Lol!!!!!

 

[D.O.G.]

How are you balancing the blades?

I'm using a digital scale.

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If you clip the edge of the blade, wouldn't that separate the the blade where the two meet at the seam where they mold them together?

 

[KLA]

Never had that happen. Any time I did that I didn't really clip it, I basically just sanded the end a bit to remove some weight, keeping the form of the blade.

 

[Smoggie]

Never had that happen. Any time I did that I didn't really clip it, I basically just sanded the end a bit to remove some weight, keeping the form of the blade.

Depends what type of blade you were working with. With wood blades they are solid, so you could sand/clip some off. Carbon blades on the other hand have a very thin skin over a foam or hollow core. Anyone who has ever broke a carbon blade will have seen this first hand. So if you sanded/clipped anything significant off the tip of a carbon blade you would expose the foam/hollow core, or at least cause the upper and lower skins to become separated.

 

[D.O.G.]

That's what I was talking about splitting/separted the CF blade if clip.
Well I just balanced the blade with the clear packing tape. It has worked before but not as much tape. There wasn't any vibration,shake or wobble upon spooling up. I'll give it a try today when morning comes. It's just for the time being til my new blades come in sometime this week.

 

[D.O.G.]

If these are high end blades, I would be taking them back. They should not be that far off. But, you can use as much tape as you need as long as it's not going to come off in flight. If I have a cheap blade that needs a lot of tape, I just use vinyl since it's heavier and looks a little better. And also can be used as blade tracking tape.

In stead of clipping or sanding the blade, I took your advice Tony and tape the one blade up. I had the chance to fly today and all went well. The tape didn't come off during flight and the 450 flew like she had new blades. Thanks again for your help. Cheers!