Correlation between blade's weight and blade's flex

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Hello everyone, I searched for this question online but didn't find a truly exhaustive answer. I would like to know your opinion and experience on this: Is there a correlation between blade's weight and blade's flex? I think lighter blades should have more flex compared to the same blade but heavier, right?
I think it's quite intuitive that generally speaking for two blades of the same composition the thicker one will be slightly stiffer because it's physically harder to bend. This will probably make it a bit faster and harder. Consequently the slim one it's going to be physically less rigid and easier to bend thus probably making it a bit slower and softer. But then doesn't this means that for two blades of equal composition the lighter one is also generally speaking going to be the flexier one? If it's lighter it could be due to either less glue, lower density wood, thinner overall thickness or a combination of these; all things that intuitively should have less rigidity and more flex as a consequence. Does this matches your experience?
 
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Don't think there is a obvious correlation between weight and flex, because a thicker blade could also be lighter. So if lower density means more flex, and thicker means less flex, would they cancel out?
Sorry, maybe I wasn't clear enough about the blades being the same. The blade composition has to remain a constant. Because of this I would assume that most of the thick Viscarias are going to weight more than the thin Viscarias. Am I missing something?
 

ZFT

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ZFT

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You are putting an assumption the weight is distributed evenly. If a weight is put in the handle it may not necessarily mean the heavier blade is stiffer, in my example it’ll just mean the centre of balance is shifted more toward where the weight is.

When working with wood there are so many variables to arrive a final weight. The core may be denser/heavier, offset by lighter medial and/or outer ply or handle.

The only uniform input I can think of for Viscaria would be the ALC layers though can only be a small % of the total composition.
 
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Sorry, maybe I wasn't clear enough about the blades being the same. The blade composition has to remain a constant. Because of this I would assume that most of the thick Viscarias are going to weight more than the thin Viscarias. Am I missing something?
Composition being the same doesn’t necessarily mean the thickness of those layers are the same. Also what @ZFT said.
 
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Ok, so practically speaking if I had to assume which Viscaria is the slower and softer one between a light and a heavy one without trying them, wouldn't I probably be right if I said the light one is the slower one?
 

ZFT

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I think the variables both myself and @DukeGaGa have tried to explain is precisely why you haven’t been able to get your truly exhaustive answer 🙁 Sorry!
 
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Hello everyone, I searched for this question online but didn't find a truly exhaustive answer. I would like to know your opinion and experience on this: Is there a correlation between blade's weight and blade's flex? I think lighter blades should have more flex compared to the same blade but heavier, right?
I think it's quite intuitive that generally speaking for two blades of the same composition the thicker one will be slightly stiffer because it's physically harder to bend. This will probably make it a bit faster and harder. Consequently the slim one it's going to be physically less rigid and easier to bend thus probably making it a bit slower and softer. But then doesn't this means that for two blades of equal composition the lighter one is also generally speaking going to be the flexier one? If it's lighter it could be due to either less glue, lower density wood, thinner overall thickness or a combination of these; all things that intuitively should have less rigidity and more flex as a consequence. Does this matches your experience?
In theory yes, and if so only marginally. There are plenty hard materials out there that can still bend. Thickness and less wood plies is more obvious in terms of flexibility. Also, what you loose most with too light a blade is the almighty crispiness no amount of flex can make up for.
 
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You guys are guessing! It is a good thing engineers don't design by opinions.
Why are I-beams common in structural designs?
Think! How would you orient a 2 x 6 for maximum resistance to bending/flexing?
Nope, we're not guessing. We're trying to use plain simple words to explain there are just too much variables to consider, and weight can't be isolated.
 
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What Brokenball is saying is that stiffness is highly dependent on the individual stiffness of the outer layers and how far apart they are. If we talk about commercial blades, let's say Viscaria for example, we can assume the weight of the handle is the same, so the only difference in weight is on the blade itself. Wood density can vary a lot within the same species, that's why you end up with such a big weight range within the same model. Now, you can't know for sure where the difference is exactly, which of the layers is heavier, and that will have different outcomes. You can even have two blades with the same weight, and a different density distribution along its thickness. For example, one has denser outer plies and a lighter core, the other has lighter outer plies and a heavier core. What usually happens with wood, specially within the same species, is that weight and hardness go hand in hand. This means that generally, given the same composition, a heavier blade will also be stiffer and harder.
 
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What Brokenball is saying is that stiffness is highly dependent on the individual stiffness of the outer layers and how far apart they are. If we talk about commercial blades, let's say Viscaria for example, we can assume the weight of the handle is the same, so the only difference in weight is on the blade itself. Wood density can vary a lot within the same species, that's why you end up with such a big weight range within the same model. Now, you can't know for sure where the difference is exactly, which of the layers is heavier, and that will have different outcomes. You can even have two blades with the same weight, and a different density distribution along its thickness. For example, one has denser outer plies and a lighter core, the other has lighter outer plies and a heavier core. What usually happens with wood, specially within the same species, is that weight and hardness go hand in hand. This means that generally, given the same composition, a heavier blade will also be stiffer and harder.
Thanks for translating Sergio!

There you have it OP, you won't get a better answer.
 
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Nope, we're not guessing. We're trying to use plain simple words to explain-glue and the other with epoxy there are just too much variables to consider, and weight can't be isolated.
agreed. with most variant having been discussed like different materials, thicknesses etc, may I also mention the kind of glue that is being used. Use exactly the same laminates but assemble one with huf-glue and another with epoxy or vinyl-ester and voila :"3 completely different blades"
 
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Weight has little to do with it. It is more a function of the cross sectional inertia and the property of the material. I very thin piece of titanium , 2inx2inx1/16in can not be bent even if you grab it by both sides with pliers and try to bend it. I know. I have tried. Somewhare around work we have such a piece.

An I beam has a lot of cross section away from the axis of bending supplied by the top and bottom parts of the I beam.

My Dr Neubauer Firewall+ weighs around 70 gm but it is 9mm thick. It doesn't flex in the high speed videos I have made.

You have to know the right terms to search for.
 
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I very thin piece of titanium , 2inx2inx1/16in can not be bent even if you grab it by both sides with pliers and try to bend it. I know. I have tried. Somewhare around work we have such a piece.

Now sorry but that is just complete bollocks. I am an old cripple but have good memory of having
to bend titanium strips to be fitted into the tips of white- water kayak and canoe paddles.
They are a real bastard to bend in comparison with a same size aluminum strip but bend they will.
 
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to bend titanium strips to be fitted into the tips of white- water kayak and canoe paddles.
They are a real bastard to bend in comparison with a same size aluminum strip but bend they will.
The titanium tips are probably some alloy like my glasses which are supposedly non breakable titanium but they flex too.
 
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One thing that may make it more clear: stiffness is function of thickness power 3 but function of modulus of elasticity power 1. Stiffness of material used will usually have less effect on stiffness than thickness of the blade - unless we are comparing very different materials with large difference in moduls of elasticity like coparing wood to titanium.
 
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