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      Abbreviated rules   07/28/2017

      Underdawg did an excellent job of explaining the rules.  Here's the simplified version: Don't insinuate Pedo.  Warning and or timeout for a first offense.  PermaFlick for any subsequent offenses Don't out members.  See above for penalties.  Caveat:  if you have ever used your own real name or personal information here on the forums since, like, ever - it doesn't count and you are fair game. If you see spam posts, report it to the mods.  We do not hang out in every thread 24/7 If you see any of the above, report it to the mods by hitting the Report button in the offending post.   We do not take action for foul language, off-subject content, or abusive behavior unless it escalates to persistent stalking.  There may be times that we might warn someone or flick someone for something particularly egregious.  There is no standard, we will know it when we see it.  If you continually report things that do not fall into rules #1 or 2 above, you may very well get a timeout yourself for annoying the Mods with repeated whining.  Use your best judgement. Warnings, timeouts, suspensions and flicks are arbitrary and capricious.  Deal with it.  Welcome to anarchy.   If you are a newbie, there are unwritten rules to adhere to.  They will be explained to you soon enough.  
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Shu

32 ft Trailer Sailer

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If you're going to build with plywood only, the big portion of the bilges shown with large radiuses will be a pain. Maybe a hybrid with ply topsides and heat thermo-formed foam round bilge shapes? Otherwise you're just creating a lot of work for the sake of using plywood when a different material would be easier to form.

 

Now if you did a Dudley Dix (see his Black Cat 38) hull form with true radius chines, then plywood makes a bit more sense.

 

I like plywood for little boats, where foam core has to have to have too much glass to make the skins tough enough. But for a 30' boat I'm not sure I'd recommend ply core any more. Resale value will be much better with foam core too.

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Proa,

That reminds me of my Fortran programming professor at University. He seemed old as the hills, and I suspect he had worked for NASA or a NASA contractor, since most of our programming problems revolved around orbits, satellites, and such. Coming from the era of slow, heavy computers and needing to do extreme weight shaving, he taught us to be very stingy with computing time. He always had a more efficient way to program.

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Here is the "corrected" body plan, along with profile and plan views. No diagonals yet. Note that the points of max beam and max hull depth are more than two stations apart.

 

 

Maybe it's just me but I can't make sense of those lines. At various points it looks like you have a hard edge or chine that doesn't make sense. Is that the software anomaly that was loosely discussed in the other thread?

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Proa,

That reminds me of my Fortran programming professor at University. He seemed old as the hills, and I suspect he had worked for NASA or a NASA contractor, since most of our programming problems revolved around orbits, satellites, and such. Coming from the era of slow, heavy computers and needing to do extreme weight shaving, he taught us to be very stingy with computing time. He always had a more efficient way to program.

 

University High Performance Computing types get very good and stretching their computing grant money a long way, especially when it comes to the highly sought after super computers. Didn't matter how big your computer was, you milked that sucker for every cpu cycle and bit of memory you could get your hands on.

 

While I wouldn't dare trust a bit of code in my hands, I've more than once looked over someone's shoulder and gone "you need to flip that 'for' loop" or similar. A bit of a dying art I fear...

 

When I was a kid, North sails had a program that ran (albeit slowly) on a portable computer for sail design. it was very simplistic and had a limited number of elements but showed the fluid flow and load paths of the sail in colours. My first real appreciation for computers doing something other than games and basic word processing and have been hooked since. I've lost touch, but I still love CFD and HPC. I could geek out on it for hours. I wonder if Norths were not one of the first lofts to do computer simulations?

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That "Corrected body plan" has a long way to go before it is fair. In this case I think "computer aided design" is making it harder for Shu than it would be if he sat in m y office for three days and used a spline and pigs. The effort should go into producing the desired shape and not into learning how to manipulate the program. I'm not knocking lines fairing programs I;m just saying that I don't see any progress on Shu's shape despite the numerous splashy examples from others. They do not seem to be helping. When Will Porter stayed with me he produced a hand drawn set of lines first then he went to the computer. He understood what fairing lines required before he got on the computer.

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No way! Gosh I remember when they swore grasshopper would never be available for the mac version. That's fantastic. I'll have to check that out; I wonder if plugins will work with the mac version. Once you start using GH in earnest, you'll find that there are some plugins that you can't live without for whatever reason. edit...just checked, apparently not.

 

I agree with Bob about fairing. Working with splines on paper or a loft floor (who does that anynmore?!?) makes understanding what is happening with your fairing program much easier, and your results will show.

I just started messing around with grasshopper today- it's now available in the newest WIP Rhino for Mac build. It's a bit buggy still, but I've managed to work my way through a few tutorials. I'm blown away by how cool it is.

 

http://www.grasshopper3d.com/page/grasshopper-for-mac

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I fear this discussion may turn into one of those esoteric discussions about various guitar pick ups where the gear heads get all excited about details. Problem is that they can't play.

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Proa,

That reminds me of my Fortran programming professor at University. He seemed old as the hills, and I suspect he had worked for NASA or a NASA contractor, since most of our programming problems revolved around orbits, satellites, and such. Coming from the era of slow, heavy computers and needing to do extreme weight shaving, he taught us to be very stingy with computing time. He always had a more efficient way to program.

 

One of my programming gurus, Niklaus Wirth, wrote a book called "Algorithms + Data Structures = Programs" (1976) that emphasized the importance of efficiency when writing code. There are many ways to get a computer to generate a given result but some are WAY FASTER than others. That was more important when computers were slow but it's still possible to bring a computer to its knees and literally crash it when the code is bad. Grasshopper can easily do that if you don't understand its data tree/list approach.

 

Wirth was the chief designer of the programming languages Euler, Algol W, Pascal, Modula, Modula-2, Oberon, Oberon-2, and Oberon-07. He was also a major part of the design and implementation team for the Lilith and Oberon operating systems, and for the Lola digital hardware design and simulation system. He received the ACM Turing Award for the development of these languages in 1984 and in 1994 he was inducted as a Fellow of the ACM. He designed the simple programming language PL/0 to illustrate compiler design. It has formed the basis for many university compiler design classes.

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I've been lax about responding to comments:

Bob,

I've been in work deadline purgatory. I did a quick fix on the presentation of the previous hull form and posted that a few weeks ago; the "correction" was only to the presentation. I started working on the form again last night. I would love to be using my splines and weights (I actually know how) but as noted before, SWMBO has banished the drafting table to the barn.

 

Rasper: You posted earlier about using a variable fillet between two lofted panels in Rhino. I only see the option of choosing a single value for the surface filet. Do you have any further enlightenment? By the way, once I faired the two edges of the panel, the loft function created a beautifully fair surface. No lumps and bumps! That is much better than the lumpy surface created with the sweep two rails function. Thanks.

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Raz'r:

Brad actually let me sail Woody with his crew one day about 4 years ago. It is the narrowest possible boat within the rule, and has the easiest helm. Even when it heels, which you are generally not supposed to do in a skiff, the helm was light and manageable. I think that is what narrow gets you. However, it's angle of no-return is also less than the typical 14. So it feels great, right up to the point where you capsize. Beautiful, beautiful boat. Will you be bringing it to Hawaii this year?

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Rasper: You posted earlier about using a variable fillet between two lofted panels in Rhino. I only see the option of choosing a single value for the surface filet. Do you have any further enlightenment? By the way, once I faired the two edges of the panel, the loft function created a beautifully fair surface. No lumps and bumps! That is much better than the lumpy surface created with the sweep two rails function. Thanks.

 

Shu, Have you tried the Filletedge command? It has many options for filleting joined edges.

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Raz'r:

Brad actually let me sail Woody with his crew one day about 4 years ago. It is the narrowest possible boat within the rule, and has the easiest helm. Even when it heels, which you are generally not supposed to do in a skiff, the helm was light and manageable. I think that is what narrow gets you. However, it's angle of no-return is also less than the typical 14. So it feels great, right up to the point where you capsize. Beautiful, beautiful boat. Will you be bringing it to Hawaii this year?

 

Yep, she's coming to Hawaii!

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Thanks Jose. I'll give that a try.

 

Raz'r, I'll see you in Kaneohe then. Two bright finished wood 14's in the regatta will be great.

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Yep. I hit one 4 years ago with both of us out on the wire and the spinnaker up. Just a sickening noise. The boat was ok, but I bought a new daggerboard from Kris Henderson that evening.

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I've only hit one going upwind. Funny when the crew stands up and the water comes just to his knees.

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I fear this discussion may turn into one of those esoteric discussions about various guitar pick ups where the gear heads get all excited about details. Problem is that they can't play.

 

What about a detailed esoteric discussion between gear-heads who can play picking guitars.

 

http://www.youtube.com/watch?v=TzRv9k_JoYs

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That's a shame. SWMBO liked the interior photos. I might have to find a bigger rig for it here in Southern California though.

 

Progress is being made on the 32.5 trailer sailer. Still no luck with the fillet edge command. Seems like I can only do a constant radius and edit it afterward. For now I'm back to drawing lines, and using lofted surfaces at times to collectively clean up the lines. Yesterday, I made the revisions spoken of before: more depth in the fairbody aft, less in the fairbody forward, larger half-angle of entry. Preliminary hydrostatics indicate the displacement is a bit light and the Cp is still only .53. I will try for a little more depth to the fairbody forward and aft.

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Join up your topside panel and the bottom panel and then in Rhino run 'VariableFilletSrf' and you will be able to change the radius at any point along the edge. It just starts with the beginning point and the end point but look carefully at the options in the command line and you will see that if you type 'A' for AddPoints, you can create as many points at which you can enter the radius of the your fillet. Take your time and check out the options in the command line. The command line options offer a lot of functionality in Rhino and if you don't look up and see what it is making available you will never get very far in Rhino.

 

Have fun!

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