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ptc-46596211-Visitor
1-Visitor
June 12, 2013
Question

Surface Area of Hull below Waterline

  • June 12, 2013
  • 3 replies
  • 3174 views

I have an assembly of a makeshift hull, and I have computed the hull's waterline. I've made an extruded cut to remove all material above the waterline. I want to compute the surface area that is exposed to the water, but the surface area calculation from mass properties includes the top of the assembly, which I don't want (as it isn't actually exposed to water).

Does anyone have any ideas as to how I would accomplish this outside of adding up the surface area's of each individual surface? Eventually I will need to programmatically find this result using the Creo Toolkit, but for the moment am just trying to accomplish it manually.

Your help's appreciated.


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3 replies

Patriot_1776
Patriot_177622-Sapphire II
22-Sapphire II
June 12, 2013

If I remember correctly you can simply copy the surfaces, and do an area on that and choose one-sided. Haven't done it in a while, can't remember the exact sequence......

T
TomD.inPDX17-Peridot
17-Peridot
June 12, 2013

Sounds like a bug. What version are you using?

I just created a square; 100x100 and trimmed it down the middle (saved both sides) and each half measures 5,000.

I like Franks suggestion. Offset the below-waterline surfaces by 0; merge them, and see if that returns a more realistic number.

P
ptc-46596211-VisitorAuthor
1-Visitor
June 12, 2013

Also, I tried what you first said and it doesn't give the correct (well correct as in what I want) surface area. With a 10x10x10 cube, S.A. = 600. Making an extruded cut to remove half of the material and rerunning the measure area tool returns a S.A. of 400, not 300.

Shrinkwrapping the assembly and then measuring that didn't do the trick. Copying the geometry looks like it's my only option, but because it asks you to redefine the constraints doing it programmatically isn't feasible. Looks like I'll have to explore other methods.

Thanks for your help.

T
TomD.inPDX17-Peridot
17-Peridot
June 12, 2013

Okay, let me check your math. 600sq/units at 10x10x10 ...Check.

400sq/units for 10x10x5 ...Check! 5x10x4 + 10x10x2 200+200=400... yep

P
ptc-46596211-VisitorAuthor
1-Visitor
June 12, 2013

Sorry, I realized the description of a hull is not fully correct. It's an amphibious vehicle, so it isn't just one nice body or part, it has multiple components that are exposed to the water.

When I use just measure, surface area it doesn't look like it gives correct results and I've read that using this feature in an assembly will return the surface area of all of the parts, even if some surfaces mate with others. So that's why this is returning an answer that I'm not expecting.

When I use the copy surfaces method, it ends up asking me to redefine the constraints. As the assembly becomes more realistic and complex this might not work, or at least be a big pain. Is this (or I've read possibly shrinkwrap) be my main/only option? I feel as if it might be.

Thanks for the replies.

T
TomD.inPDX17-Peridot
17-Peridot
June 12, 2013

You could also export the assembly and import it is a part. You would still be doing some work to it but at least you can tackle it at will.

Shrinkwrap should also work. Haven't done enough of that to know how accurate or simple it is.

You can also use the merge feature into a part from the assembly so things become one.

I really don't know what would be simplest, or what the implications are for making it programmatic.

Patriot_1776
Patriot_177622-Sapphire II
22-Sapphire II
June 12, 2013

Shrinkwrap tries to copy all the surfaces inside the assembly. It will go into holes in an exterior part and grab the interior surfaces. this can be alleviated by accuracy settings, but it's going to be a pain because as the accuracy settings get coarse enough not to try and go inside holes, the surfaces get coarser too.

Sounds like he needs to copy the surfaces from each part manually into a dummy part, and then measure it. I remembered wrong, there is no "one-sided" for surfaces. It measures the area until it reaches an edge. If it's a sphere etc., you only get either the outside or inside area (which are the same), but not both. I did a 1" square to test it.

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