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Old 10-03-2016, 03:25 PM   #1 (permalink)
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Default 3 blade difference

Is there really a difference between buying a 3 blade set or using 2 pairs and having an extra, I've read the 3 blade sets are lighter. I converted my goblin to 3 blade it came with a set of 690 thunderbolts, I can not find the 3 blade set in stock anywhere. Should I wait or just buy another pair of 690's
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Old 10-04-2016, 05:52 AM   #2 (permalink)
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Sets of blades tend to come matched and balanced and ready to install. If you mix and match blades from different sets, you will most likely have to spend a little bit of time balancing and matching them.
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Old 10-20-2016, 05:58 PM   #3 (permalink)
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Zeal has the 3 blade pack for 690
If you send them an email, they make a "3 blade set" out of any blade they stock

I got them to send me a 690mm Energy Yellow mains and 95mm tails in a 3 pack
Same for the Goblin 380 (expect, that uses the 360mm 3 blade pack).

There is nothing "special" or different about anyone's 3 blade pack.
They are the same as the 2 blade pack, expect there is a 3rd blade.

If you are a manufacturer of blades, you make a batch of 50 or 100 and then start matching up pairs and triplets by weight.

If they get a special request for a 3 blade pack, it is pretty easy to dip into the bin of 690mm blades and find one that matches the weight of 2 others.
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Old 10-20-2016, 06:10 PM   #4 (permalink)
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Quote:
Originally Posted by ticedoff8 View Post
If you are a manufacturer of blades, you make a batch of 50 or 100 and then start matching up pairs and triplets by weight.

If they get a special request for a 3 blade pack, it is pretty easy to dip into the bin of 690mm blades and find one that matches the weight of 2 others.
There is more to matching blades than purely weight. You need them all to be balanced and balance is not only dependent on weight but also where the centre of gravity (CoG) of the individual blades is. CoG can vary quite a bit on unmatched blades which is why the process of balancing blades is more complicated than just weighing them.
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Old 10-20-2016, 06:35 PM   #5 (permalink)
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Quote:
There is more to matching blades than purely weight. You need them all to be balanced and balance is not only dependent on weight but also where the centre of gravity (CoG) of the individual blades is. CoG can vary quite a bit on unmatched blades which is why the process of balancing blades is more complicated than just weighing them
While theoretically correct, there is no need to go to all that trouble

A manufacturer's layup, curing and material selection process is such that every blade in a batch is practically identical to every other blade in the batch.
Otherwise, they end up with a sh!t load of blades that have no partners due to CG or weight problems.
And then, they go out of business because they couldn't figure out how to make a consistent product.

And, even blades that are not from the same batch will still be perfectly fine together as long as their weights are close.
Why?
Because their internal layup places the weights, safety wires and root reinforcement at the same, exact position on every blade they make.
Otherwise, they could not turn out 100 blades at a time that all match each other.

This ain't the '90s anymore with wooden blades or limited run hand laid fiberglass blades
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Old 10-20-2016, 07:20 PM   #6 (permalink)
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3 blade design is completely different from 2 blade design. If a company is selling you 2 blade design packaged with a third, at least for me it guarantees it will fly like utter crap.

In a proper 3 blade set the weight and CG is changed dramatically. Because a 3 bladed setup has dramatically higher gyroscopic forces, in order to have acceptable agility major changes to blade weight and CG have to be made.

Now if you love very slow flip/roll rates and a "feels like glue" off center feel, than standard FBL blades in a set of 3 might work for you.

Align and SAB make reliable proper 3 blade sets that are safe to fly. Be very very weary of budget companies making "true" 3 blade sets. Way too many stories of blade failure. It's not trivial to pull out blade weight and maintain blade integrity. I'd stick with the 2 brands for safety reasons.

I have ~600 flights on a 3 blade max prototype and I went through all the available 3 blade sets. I like the new Align 3 blade set BY FAR over other options.

The smaller heli's - I have many flights on a 500 and 570 3 blade setups (developing 3 blade presets for Brain2). Those blades are utter crap too. Hopefully soon something decent comes out for those sizes.

Anyway - to answer your question: Go buy the Align 3 blade set. A few shops have them in stock. Major upgrade to your TB's.
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Old 10-24-2016, 01:33 PM   #7 (permalink)
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OTS: IYHO, in lieu of a blade designed specifically for a 3 blade head, would an old FB blade be a better choice for a 3-blade head?

Assuming they can still be found.

The FBL blades are heavier and their CG is forward of a FB blade.
This was to make them more stable than the FB blades

In "early days", the FB blades were not recommended with FBL gyros because they were less stable than FBL blades.

I guess no one advertises "flybar" vs. "flybarless" blades anyone.
The assumption is that everyone uses FBL now.
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Old 10-24-2016, 01:55 PM   #8 (permalink)
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If I had to guess prob wouldn't fly well. Still too heavy. But it's not really something I can guess at. Each set would have to get flown.

If you prefer really low agility and a "dead" feel with bad efficiency prob you have lots of options. But to get equal efficiency and agility I think it requires a purpose built blade.

The new Align 3 blade 690 set is the current state of the art in my opinion.
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