How do I go from simple hull design/lines plan to dimensioned plans/

Hi There,

I've spent a large chunk of my life living close to the sea. I have owned a 34' Bayliner, a 26' Whaler and I currently own a 29' Searay Amberjack. Looking to downsize to something I can (design and/or build) haul with a trailer. Primary boat use will be fishing and day cruising the San Juan islands.

I have be doing some research (reading) on boat design and building:

Sam Devlin, Ted Brewer, Dave Gerr, Roger Fletcher, Greg Rossel, Francis Kinney, The Gougeon brothers, etc. I think I now have a pretty good picture on many of the keys elements of wooden boat design and building.

Being a software engineer, I would very much like to experiment with a few designs using some kind of design software. I have downloaded some ‘freeware’ FreeShip, DelfShip, Carlson Hull design, demos of ProBasic and MaxSurf.

Surprise, surprise, I ‘bonded’ with MaxSurf. However, at $4000+ (apparently you can only purchase in suite form, now) for a license and then hundreds in annual subscription fees. I can’t afford to purchasing MaxSurf. I’d gladly pay hundreds of dollars for the hull modler. I don’t want to build ships, I just want to have some fun designing small ( 20ft or less) boats. If you work for Formsys and are willing to help me out, just ping me.

The other packages, I appreciate the fact FreeShip, DelfShip and Carlson Hull design are free, but they all lack the usability (user friendliness) of modern software. If any has suggestions for an, easy to use, hull design software package, that does not cost thousands of dollars please let me know.

Anyway, here is where I’m stuck in the design process. Consider the following scenario: I want to design a 20ft double-ender plywood on frame, outboard, power boat. No cabin, just a simple deck and console. I can force myself to use one of the packages above and generate a hull design. My questions are:

1. How do you add frames to the design?
2. How to take the hull design and generate dimensions for frames and hull?
3. Basically, what other tools/information do I need to create a full set of plans

(like I might buy) for my hull.

 

Shawnzoom,

I also wanted to design a boat. After reading the wise words of the professionals in these forums I realized that even with the software available I didn't have the skills to design a successful boat. despite my screen name I work a more than full time job and there was no way I could attend a college for naval architects. I enrolled in the Westlawn course and am now about 1/2 way through. I honestly had no idea how much vital information I did not know. Spending a lifetime on boats did not prepare me to design them. I would advise anyone wanting to design a quality boat to take the time and get the education necessary. I don't care if it is online as I am doing, or a four year university, just do it. I am having the time of my life and learning new things with every lesson and assignment. The cost of the materials and risk of failure make the expense and time well worth the effort.

 

Thanks for you feedback PartTime. I hear what you are saying and I respect the opinions of those who have been at this for a while. However, I'm an experiential ( i need to get my hands dirty) learner. You can attend a gazillion lectures/classes on boat design but until you start building and testing your designs, you'll never know if you can be designer. Take the simple example of trying to dock your boat is less than favorable conditions, you can get as many classrom lessons as you want but until you get out ther and experience it, you'll never know if you'll be good at it. I waited for the worst conditions to go out a practice docking my boat. It was great becuase no one else was stupid enough to do what I was doing.

Playwood and dimensional are relatively cheap. You don't need to use marine grade playwood for prototypes. I have no illusions that I will create a Bertram 31 Moppie, on my first design, or ever, for that matter of fact. However, I will arrive I my design through real world iteration. And, I'll have fun doing it.

Regards

 

Almost every boat built is almost the same as a successful earlier design. If I were you, but also knowing what I do, I would opt for a banks type dory of 22 ft or so. I'd modify the design a bit to make it mine. That way, I'd have some fun designing but also end up with a good proven design.

 

In that case I would take a look at Rhino and Orca3d, a bit of a steep learning curve and not free but the combination will help design a solid boat and with a bit of work produce usable frame dimensions from sections. The Rhino tutorials are good and Orca is not too difficult. I would be happy to help if you get stuck. Dave Gerr's books would help you get proper values for your coefficients and make sure you have enough strength. I built several OK boats just drawing them out full size on the floor using the plywood I later built the boat from. Worked alright for small boats but as they got bigger, over 25' and more complicated it just didn't work anymore. I to love just building and watching things fall into place and know allot of very successful small boat builders who do just that. One of the largest companies I work with has never drawn a boat in their 30+ years of business. They just start with a couple of proven templates and go at it. Very successful boats, one of the leading producers of jet boats for commercial passenger service. If you have the skills I say go for it. I would love to see photos of the completed boat. After reading my previous post it looks a bit preachy, I apologize.

 

Thanks for your feedback Alan. Completely agree on your point about similar designs. I have come across so many 'Dories' in my research. Do you have pointers/links to specific examples you are thinking of?

Regards

 

Parttime, nothing to apologize for. Too many people let other people kill their dreams. Here is a quote from Steve Jobs "Stay Hungry. Stay Foolish." Seems reasonable to me.

 

Shawn you may now have a good grasp on some of the fundamentals, but software doesn't do the most important aspect of the design process, which is tell you if the shapes and volumes you've selected, are appropriate for the SOR you have envisioned. This is where the education part kicks in. There's only a few ways to get it, school or courses or many years having it beat into you by an overlord, I mean mentor.

Don't shy off, but do stick closely to known, well founded designs. Fiddle with styling clues and leave the hull form generally intact, until you have the expertise necessary. There are about a dozen different types of dories. All are sail and/or row boats. Dories make lousy powerboats, unless modified into a skiff with lots of flare (an aesthetic consideration) so they still look like a dory. If you like powerboats, then forget about dories, though you might want to look at the Bartender, if you really just can't get away from them.

 

Par, thank you for your reply.

I agree on the software, to me, it is just another tool. No different than my Table Saw. A powerboat is what I want to build, and I do like the Bartender design. I may end up buying plans from Bartneder boats.

However, I still would like someone to point me in the right direction of/summerize, moving from a hull design/lines plan to dimensioned set of plans.

Regards

 

using freeship, the learning curve it quite fast and it will do what you need. Maxsurf is also very similar method.

After you shape the hull and faired it, view it in bodyplan view then goto the menu and select EXPORT POLYLINES. It will generate a DXF file containing polylines of the cross sections where you defined the stations ( which is where you would put the frames). You can do the same with buttock lines and water lines simply by selecting the export from a different viewing angle.

You must define the stations before any of this will work, and remember to turn on the lines you are trying to export so that they are visible on screen. I turn off all the other lines i dont want. Remember, these exported lines, are the outside surface of your hull where the paint would go, you need to allow for the hull material thickness before you have you frame sizes. So;

I Then open the exported DXF file in Autocad (or you could use any 2D CAD software) and manipulate them from there such as setting your offsets to allow for the hull thickness, draw cutouts and doorways etc

Now you can dimension these however you like using the 2D software and print them or export the file to your local CNC router who will cut everything out for you and save you the time lofting it all out by hand

See my thread here, which contains most things from the beginning of the design to now where ive started building it --> http://www.boatdesign.net/forums/boat-design/efficient-10m-displacement-powercat-38588.html

 

Once you've drawn up the lines, you have the dimensions you need. It's assumed you've divided the hull into stations, which can be used as molds, though depending on the build method, may require some revision in location and count, if for no other reason than to make the build easier.

For example most divide the LWL into 10 sections, which makes the math simple and references to "centers" preferences easier to understand. On some boats these stations could be used directly as molds, but on other builds or certain hull shapes, you may want to refine these mold locations, such as incorporating bulkheads and partitions into the molds, to save some extra work, for example or to better define a heavily shaped area or to permit relatively thin planking stock sufficient purchase on the molds, so they don't sag between them, etc.

This is the education and experience part of the equation. Another example would be how far apart should your molds be on a 3/4"x3/4" strip plank build? How much farther apart could they be if the strips where 1.5"x3/4". Is this an advantage to know? There are countless examples of this type of problem solving, all with application specific approaches, for each build method.

Once you have a set of lines you like, the next step is the GA and weight studies part of the process. You need to get the boat to weigh what your lines say it should and also balance on those lines as drawn. It's one thing to draw up a nice hull, but it needs to reconcile with the build method, materials employed, equipment list, crew and stores expectations, plus what ever reserve you've factored in.

How to get to this point is education. Books will help, but trust me some quality time, with someone that has a clue, can be more beneficial than a dozen books and a lot faster.

 

Toss the computer , build a model that pleases you and take the lines off.

Carving in wood is far more rewarding than staring at a screen.

And the boat will not be limited to what a computer finds easy to draw, so should be far prettier.

FF

 

Using freeship, you divide each panel into its own layer then you can allocate a density to each panel. It will sum the masses of each panel/layer and based on its location, determine the center of gravity of the boat to within the accuracy you have allowed for. Provided the center of gravity = the center of bouyancy, your ship will float on its lines.

There is certainly much experience required to design an entire boat from scratch and do it well so it performs well and so it can actually be built as designed... but whats the point of a boat design forum where it seems you only get - "go and buy a set of plans".... maybe we should rename this domain to boatplansales.net??? Not a dig at you personally PAR, but so many threads here end up with this same damn mentality...

Go for it mate, design your own boat and go build it - the information is already here, just takes considerable searching sometimes...

 

I agree the most often voiced opinion is go buy a set of plans, but this is also knowing the statistics of home builds and wannabe designers. The simplest route is a set of plans, all the math and engineering is done for you and modifications, if not extreme will be fine.

I have to admit being tempered by several "events" the most recent was a guy that self designed a little schooner, because he always wanted one. It was a skiff like hull, with a small cabin and bald headed gaff schooner rig on it. He was one of those, "if it looks right, it probably is" types. I met him at the ramp as I was launching my self designed and built ketch. I mentioned the rig looked too far aft, which he hesitantly agreed with, adding he'll sail by the lee and fix it later.

He launched, motored out about 200 yards, hoisted his three sails, made way for about another 100 yards, attempted a tack and it capsized in 10 to 12 knots of wind. He righted his 18'er, bailed for a few minutes then capsized again. By then I was there in my ketch and I dragged his still capsized boat back to the ramp where he could right and bail again, with a stern warning from me to put it directly on the trailer and go home and think about it.

He did, converting it to a sloop with about 2/3's the area of the schooner. I see him out on the lake occasionally. It sails much better as dry sloop, than the soggy schooner.

 

Groper said

Lol, could not have said it better myself. However, like Groper I appreciate the constructive feeback from all.

Par said

Agree, let me know when you are next in Seattle Likewise, I don't think there is any substitue for the interative and interactive process of builed-test-refine. Fortunately, I have set my sights low. I will start with a simple, small, hard chine, plywood-on-frame, mono-hulled, outboard powered, boat.

I'm starting small and will see if I can work my way up from their. I plan on taking a class at one of the local wooden boat centers in the Seattle area. I may even take a class with Sam Devlin. That is the beauty of living in Seattle. BTW: This forum is kinda like a distance learning class but Groper says, the information can sometimes be hard to find.

Fast Fred says

Nah... I like computers.


Thanks for all your replies.

Regards