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post #141 of 1155 Old 04-26-2013
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Re: Bob Perry's take on Wolfenzee's dream boat

Hello:
Back to reality again..............
I recently tank tested a new design. We tested two models. Cost of each model was $9,000. A new 3D modelling "printer" could not produce the 7" long models we needed for accuracy. Big models tank test best. The total cost of the entire tank testing proceedure, including models was over $50,000. This is not within the budget of most small design office design fees. But it sure is fun and instructive.

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post #142 of 1155 Old 04-26-2013
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Re: Bob Perry's take on Wolfenzee's dream boat

Okay. Best thread ever.

And that is one hell of a camper shell for my pickup:

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post #143 of 1155 Old 04-26-2013
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Re: Bob Perry's take on Wolfenzee's dream boat

bob-
Reality is a subjective and constantly changing concept.

Try Rapid Prototyping, Advance Digital Manufacturing, 3D Printing, 3-D CAD | www.3dsystems.com for 3D printers that run up to something like 21x15x12" and remember, this whole field is breeding faster than rabbits and generating new equipment and lower prices every week. There are also many service bureaus that will print your prototypes for you, so you don't have to buy cow to get the cream.

A 7" model? Plenty of options, the biggest problem would be just finding someone who knows what is available in such a rapidly changing industry. At fifty grand a shot for conventional models, I would think there's time to "make haste slowly".

I'm not presuming to know what works best for your business, just saying there are new tools that have been flying below most radars.
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post #144 of 1155 Old 04-26-2013
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Re: Bob Perry's take on Wolfenzee's dream boat

That rapid prototyping is amazing stuff. I first heard about it in relation to engine parts by the big auto manufacturers a few years ago. Watching a model of a cylinder head "appear" in a tank of resin is as close to magic as it's possible to get

Does anyone here know how the laser beam "terminates" at the correct spot within the tank of resin?

I, myself, personally intend to continue being outspoken and opinionated, intolerant of all fanatics, fools and ignoramuses, deeply suspicious of all those who have "found the answer" and on my bad days, downright rude.
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post #145 of 1155 Old 04-26-2013
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Re: Bob Perry's take on Wolfenzee's dream boat

Hello:
Opps! I hope you guys have figured out by now that the quality of my spelling is only surpassed by the quality of my two fingered typing.

That was suppoosed to 7', seven feet, 84" not 7". We need a big model.
Does your tool spit out a 7' model? Remember that's for a 42'er.
"Maybe some day soon" doesn't work well for me today.

Smackers:
We can build you a camper top any time you like.
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Re: Bob Perry's take on Wolfenzee's dream boat

Dunno, Bob. I didn't go looking for 7 foot models but that might just mean four two by two sections and some crazy glue. Or a 2x2 foot model, with a seven foot rise. 54" wide inkjet printers didn't happen in the first year, either, but they're easy enough to find now.

JonB-
AFAIK the laser beam is "focused" the same way that a beam is focused to read the pits on a CD while ignoring any dirt on the outer plastic. And the cured material blocks the beam. There is a discrete range or radius of how much material is cured/melted by a beam so each machine, each technology, accomodates a different number of angels that can be dancing on a pin.
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post #147 of 1155 Old 04-26-2013
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Re: Bob Perry's take on Wolfenzee's dream boat

Hello:
Now we use CNC programs to carve the mold we need for the big model. I have a CNC half model on my wall. When the day comes that they make a 3D printer the size I need I will certainly consider using it.

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post #148 of 1155 Old 04-26-2013 Thread Starter
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Re: Bob Perry's take on Wolfenzee's dream boat

Quote:
Originally Posted by bobperry View Post
Hello:
Jeff:
I have so many stability plots for my new 60' ketch that I have lost count of them. I do this all the time and as I have said I use stability studies to evaluate keel configs and draft options. I am not blind to this stuff. I have been using computer stability studies for the past 35 years. I still have some that were printed out on that wide, greenish , striped paper with the holes running down each edge. It puzzles me that some of you respond like I am just beginning to figure this out.

I suggest a better breakfast.
I apologize if my comments sounded as if I was implying that you were just figuring this out. I know way better than that.

What I was responding to was your comments about S&S and Phillip Rhodes not doing stability curves. I was trying to put a layperson's perspective on your comment by saying that as designers are moving away from accepted design norms tools like stability curves are helpful in trying to develop a thumbnail understanding of the characteristics of those explorations.

Back in the hand drafting, planimeter and balancing cut-outs on a divider days, I worked on an 'inclining calculation' for Charlie Wittholz. That single angle measurement assumed that the boat rotated about the crossing of the drawn waterline and the centerline and that longitudinal trim did not change. I can understand why they would not do many of those and would have little faith in them when they did....

But at the heart of it, guys like Olin Stephens and Phillip Rhodes did not venture very far from what they knew how to do well, and like you, could eyeball a boat and know she'd stay right side up, or would return to right side up when she was over turned.

Jeff


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post #149 of 1155 Old 04-26-2013
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Re: Bob Perry's take on Wolfenzee's dream boat

Jeff: I think that was well said and accurate. I look at stability curves today because they are easy to get. But I can almost always predict what they will say very accurately.
When I do rely on a stability study is when I do a boat like my "container cruiser", something "out of the box" Oh I'm so funny. I kill myself. Or maybe a very light and beamy boat like STEALTH CHICKEN or FOXFIRE. When you work on the edges it's nice to know just how close to the edge you are.

Still I am dubious as to how accurate a 2D stability study can be given the dynamic 3D world the boat lives in at sea. I have an idea, let's take the boat behind the breakwater on a calm day and tip it over and see what happens. What the hell is that worth? But they do it. The alternative is not really practical. That said, I love to watch those tests.
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post #150 of 1155 Old 04-26-2013
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Re: Bob Perry's take on Wolfenzee's dream boat

As I pointed out in a previous post, one can get a pretty good idea of a boats ultimate stability by simply looking at it .If the midships section bears a closer resemblance to a beach ball, well rounded (( trunk cabin with a high camber on top, a whelhouse with lots of buoyancy in it) then it will have high ultimate stability. If it looks more like a raft (exessive beam, flush deck with not much in the way of buoyant deck structures) then it will have poor ultimate stabiliy. This is before you do any calculating.
Older boats, which Bob mentioned, had no problem with righting themselves in a rollover , before boats became excessively wide and shallow, with flush decks. How about posting the stability curves of some of those deep narrow boats here?
Anyone who believes they can live aboard and cruise full time, without storage ashore, with the amount of gear that takes, and still have a light boat, is self delusional.

Brent Swain, Boat designer, Builder, and author of "Origami Metal Boatbuilding"
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