Author Topic: Would this be accurate?  (Read 3199 times)

Biggreen

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Would this be accurate?
« on: June 19, 2015, 02:56:42 PM »
My father had his PhD in physics. Worked at Mission Control during the moon missions. His son however, was behind the door when they passed out the mathematical smarts. I use this to calculate volume of a board... http://www.calculatoredge.com/enggcalc/volume.html

I plug my numbers into the "volume of an ellipsoid". Take those numbers given in cubic inches, scroll to the top of the page where I plug them into the "enter value" box and convert "cubic inches into liters".

Can I consider this reasonably accurate enough? Seems on the low side.  Help?

SUPcheat

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Re: Would this be accurate?
« Reply #1 on: June 19, 2015, 03:30:44 PM »
I think you forgot the angle of the dangle.  That's what they teach you when you get a Phd.
2013 Fanatic Prowave LTD 9'3"x30.5x@134L
Sunova Speeed 8'10"x29.12@131L
Sunova Flow 8'7"x30.25"@121L
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Me: 6'1"@230 lbs 68 years old

surfcowboy

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Re: Would this be accurate?
« Reply #2 on: June 19, 2015, 06:54:43 PM »
It's low by my measure. Download the free Shape 3D or any board shaping program and you can usually pretty quickly mock up something close and those are pretty right on.

peterwSUPr

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Re: Would this be accurate?
« Reply #3 on: June 19, 2015, 06:56:05 PM »
I punched some numbers I have in my head from a race bpard I made recently and it also comes out low.  Of course my board has more boxy rails than an elipsoid.  What kind of board are you doing this for?  A rounded nose and tail and domed deck like surf style board might some out a bit closer. 

If you want to figure out volumes though, I recommend getting the free version of Shape 3D.  It's pretty easy to use if you watch some videos, and you can probably get some other designs there and tweak them to your specs rather than do a design from scratch.

Peter

edit:  surfcowboy, you beat me by over a minute on the reply.  I typed too many words!

TallDude

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Re: Would this be accurate?
« Reply #4 on: June 19, 2015, 08:07:58 PM »
If my board was a flatten out sassage it would be accurate.  It's actually pretty close to what Shape 3D says my 9' surf sup is. Within 5 liters.
It's not overhead to me!
8'8" L-41 ST and a whole pile of boards I rarely use.

Biggreen

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Re: Would this be accurate?
« Reply #5 on: June 19, 2015, 08:56:54 PM »
Thanks all! Yeah I ran numbers on stock boards with posted liters and it seemed to be 10% +\- low. I knew it wouldn't be dead on, but was curious what others smarter than I discovered and thought.  Shape 3D it is! Thanks! Plus...I knew I wasn't riding an 80 liter board. Kind of like looking in one of those skinny mirrors.  :o

And Cheat. Piled Higher and Deeper, right!

55NSup

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Re: Would this be accurate?
« Reply #6 on: June 20, 2015, 02:52:48 PM »
Learn how to use shape 3d.  I used it to design board and calculate submerged volume for a board for my 35 kg boy. It worked out perfect. 

PonoBill

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Re: Would this be accurate?
« Reply #7 on: June 20, 2015, 03:26:15 PM »
basically you can't use simple geometry to calculate the volume of complex shapes unless you use a lot of slick tricks. you have to decompose the volume into a lot of regular shapes that fit together to approximate the shape.  the smaller the shapes are the more accurate the approximation. It's a common problem in game programming.
Foote 10'4X34", SIC 17.5 V1 hollow and an EPS one in Hood River. Foote 9'0" x 31", L41 8'8", 18' Speedboard, etc. etc.

55NSup

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Re: Would this be accurate?
« Reply #8 on: June 21, 2015, 05:38:22 AM »
You can either learn Shape 3D or do the Westlawn yacht design course. Then it takes days and hours to draw your hull and do sections to calculate displacement and center of buoyancy. Shape 3D is better, but Westlawn course will teach you the principles of design. In addition you can read Norman Skenes "Elements of Yacht Design",  available on Amazon in paperback.  Do both and you'll have it pretty well figured out.
My dad had a PhD in Physics and math, masters in EE.  I also somehow didn't get it.
He did teach me to read the effen manual and that it's possible to learn a lot of stuff by reading first, then go out into the garage and give it a try.

 


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