mirror70 Posted September 15, 2004 Report Share Posted September 15, 2004 My dream custom would have a holographic projector on it which would project an image of someone trying to carve but doing it really really really badly - that way, when people see me riding nearby, I'll actually look competent (ha!). The women will be all up onz. Quote Link to comment Share on other sites More sharing options...
NateW Posted September 16, 2004 Report Share Posted September 16, 2004 Sean, I had to read your post about shear twice before it clicked. Thanks for writing that up. Quote Link to comment Share on other sites More sharing options...
NateW Posted September 16, 2004 Report Share Posted September 16, 2004 Sean wrote: From a weight point of view, a 0, 60, -60 laminate might be more effective. Then Jack wrote: Did you mean to say 0, 45, -45? I thought from your other post you weren't a believer in the 60/-60 (or 30/-30) fibers? So Nate writes: 0 / 45 / -45 wouldn't give equal distribution in all directions, so wouldn't produce the in plane isotropic behavior he was talking about. 0 / 60 / -60 would, it's all laid out in equilateral triangles. Sean, what does your plate theory analysis say about 0 / 45 / -45 compared to 0 / 60 / -60? Or were you saying that your analysis doesn't model the isotropic behavior? I'm not sure what to make of your statement that "Using a plate theory analysis, a 90 degree fiber contributes nothing to torsional rigidity." And Jack said: BTW, this is really cool stuff, thanks for sharing. And Nate says: What Jack said. Quote Link to comment Share on other sites More sharing options...
Jack M Posted September 16, 2004 Report Share Posted September 16, 2004 Originally posted by Vahur Google for noice cancelling headphone, That was a joke, Todd works for Bose. Quote Link to comment Share on other sites More sharing options...
Jack M Posted September 16, 2004 Report Share Posted September 16, 2004 Originally posted by NateW Sean wrote: From a weight point of view, a 0, 60, -60 laminate might be more effective. Then Jack wrote: Did you mean to say 0, 45, -45? I thought from your other post you weren't a believer in the 60/-60 (or 30/-30) fibers? So Nate writes: 0 / 45 / -45 wouldn't give equal distribution in all directions, so wouldn't produce the in plane isotropic behavior he was talking about. 0 / 60 / -60 would, it's all laid out in equilateral triangles. Oohhhhhh yeah. equilateral triangles, of course. However, I'm still interested to know <i>why</i> Prior's quadrax is 0,90,30,-30. Quote Link to comment Share on other sites More sharing options...
Donek Posted September 17, 2004 Report Share Posted September 17, 2004 First off, I'm no professor. I'll do my best to clarify things. When I talked about 0,45,-45, 90 laminates and then said the 90 degree contributed nothing to torsional rigidity, I was talking about 2 different concepts. The eaqualy spaced lamintes apply to in plane isotropic laminate. In theory, that laminate could be rotated 12.34 degrees (or any arbitrary number) and produce the exact same results as if it were not rotated. That is in essence the definition of isotropic behavior. The 90 degree comment was simply refering to the question regarding 90 degree fibers contributing to torsional rigidiy. Plate theory prdicts no contribution to torsional stiffness. There is an interesting side note to plate theory. It is much like beam theory in that it assumes small deflextions in the material. To my recollection, it never defines the term small. Getting back to the how the 90 degree fiber influences the composite. It builds stiffness side to side in the board. It could, therefore be used to assist in the so called "energy transfer" to the edge. The other thing to consider is that a board rarely sees a pure twisting force or a pure flexing force. It is conceivable that in the situation where the board is loaded at the tip during turn initiation, the bending force is not in a 0 deg direction, but at some angle to 0 degrees. One could say that in that situation, the 90 degree fiber is contributing in some small way to the stiffness (both torsionally, and in bending). To me, this begins to get a bit cumbersome. At some point, it becomes necessary to simplify the model and rely on what can be calculated and believe in the riders ability to compensate for what can not. To me 90 degree fibers seem useless for the most part. Their contribution to the needed stiffness is so small that they are unnecessary. Nate asked about the prediction for the 0, 60, -60 laminate. It's important to first note that in standard constructions for snowboards there are a lot more fibers in the 0 direction than in the +- 45. If I leave the volumes the same, plate theory predicts a 16% decreace in torsional rigidity. If we go with equal fiber distributions, there is a 6% increase in torsional rigidity and a 12% decrease in longitudinal stiffness. I hope I was clear enough and got all the questions. Excuse my engineering approach to spelling. Quote Link to comment Share on other sites More sharing options...
mirror70 Posted September 17, 2004 Report Share Posted September 17, 2004 Sean, It seems that you're using a simple plate model and not a laminate model. is this correct? An important distinction between the two is that the laminate model takes in to account the warp's ability to stabilize the weft, and vice-versa. Quote Link to comment Share on other sites More sharing options...
Donek Posted September 17, 2004 Report Share Posted September 17, 2004 Originally posted by mirror70 Sean, It seems that you're using a simple plate model and not a laminate model. is this correct? An important distinction between the two is that the laminate model takes in to account the warp's ability to stabilize the weft, and vice-versa. Given all the matrices, I wouldn't consider it too simple. I have the ability to build a laminate stack of any composition. I'm using an excel model I wrote in College that was verified against a commercial program called Utah Laminates. I suppose that there could be a problem with it, but I've used it on 3 separate occaisions to verify other programs I've writteno similar sorts of work and always been able to get the same results. I believe there is now a freeware program I found online. I'll check it against that this evening. Perhaps you can explain simple plate vs a laminate model. The text I'm using doesn't seem to refer to these terms. I'm using Jones "Mecahnics of Composite Materials". Quote Link to comment Share on other sites More sharing options...
skeez rule Posted September 20, 2004 Report Share Posted September 20, 2004 but with more carbon fibre and a topsheet with all sorts of tech things on it like lights and terms like "high performace skid theory" on it a onepiece to match them with tassles on it like Billy Kidd wears Quote Link to comment Share on other sites More sharing options...
slopetool Posted September 21, 2004 Report Share Posted September 21, 2004 Skeez! we missed you- thanks for piping in again! You rule the slopes! Quote Link to comment Share on other sites More sharing options...
Guest chillaxin.nl Posted September 21, 2004 Report Share Posted September 21, 2004 That's an easy one: Tomahawk or Virus custom! Quote Link to comment Share on other sites More sharing options...
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