CNC/Plywood Trimaran?

Discussion in 'Boat Design' started by jmolan, Jan 3, 2010.

  1. jmolan
    Joined: Dec 2008
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    jmolan Junior Member

    After seeing Russell Brown's 18' runabout:

    http://www.ptwatercraft.com/

    I was exposed for the first time really to the CNC Plywood boat building methods. Jim Brown of Searunner fame was there, and told me he could build this boat (he is legally blind) seeing as how there are tabs and the way the wood jigs together. It all fits so well.
    So the idea has been swimming in my head.....why not be able to build a Long lean Trimaran the same way? I have spent some hours searching the web for various designers and kit builders of CNC Plywood boats. SO far no Big Trimarans. Dudly Dix has a 21' that I think is kit. And this boat really caught my eye from Lavranos.

    http://www.lavranosyachtdesign.co.nz/sc_10m-multi.htm

    So here are my initial questions: Can you convert an existing design into a CNC design? A boat that is already designed like?

    http://www.bajayachts.com/seaclipper-tri-41/images/images1.htm

    The 41' Sea Clipper is a John Marples design. But if it is in paper only, is it more trouble to covert it to CNC or better just to start over?

    Does anyone know of anyone doing a Trimaran in CNC? I see a few Cats but that is about all.

    Can someone convert say a foam glass design into CNC Ply? Or again is this too labor intensive and better to start from scratch?

    Thanks ahead for reading my questions.
     

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  2. gonzo
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    gonzo Senior Member

    There is no such thing as a CNC design. You convert any design into code the CNC can use and it will make it for you.
     
  3. Chris Ostlind

    Chris Ostlind Previous Member

    Jack,

    I've done a couple of trimarans (18 footers) that were specifically designed to take advantage of the potential of having the principal parts cut with a CNC. None of them had the tabs of which you speak.

    With a comprehensive .dxf file of all the parts, and the completed design in 3D, one could easily convert the bulkheads to be tabbed for location during assembly.

    Converting paper plans to a set of drawings for the computer is a bit of work and it would probably be easier to just create a fresh boat from scratch, using the existing design as a jumping-off point, provided that you really like the original.
     
  4. jmolan
    Joined: Dec 2008
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    jmolan Junior Member

    Thank you both. I am starting to get a handle on it. In some ways it reminds me of remodeling a house....how many times have you heard "I should have started from scratch"
    "The only thing standing between any paper design and a CNC file is time & Money"
     
  5. apex1

    apex1 Guest

    As mentioned by Gonzo, you can get CNC files out of every design drawing. Most yards or CNC cutters prefer to convert the drawings themselves, even if the designer / NA is able and willing to do it.
    So, take care, when you do it yourself you might probably end up with a effort for nothing!

    Regards
    Richard
     
  6. gonzo
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    gonzo Senior Member

    There was someone in the forum advertizing his services for that.
     
  7. jmolan
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    jmolan Junior Member

    I am going to contact the company that is doing the cutting for the runabout already. See what they have to say about converting plans from paper to digital CNC usable files.
     
  8. gonzo
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    gonzo Senior Member

    As I understand it, you can scan the blueprints and digitize them.
     
  9. guzzis3
    Joined: Nov 2009
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    guzzis3 Senior Member

    Contact Ray Kendrick. Several of his designes are built in ply and I believe he can supply the required dxf's for you at a small extra charge.

    www.teamscarab.com.au

    CNC isn't standardised so it depends on the system and tool they are using, that's why the cnc provider usually wants to do the setup themselves. I know boatcraft pacific does this sort of thing in Queensland, there are no doubt providers nearer you.

    To be honest panelling up the hull isn't the hard part. Chined ply requires signifigant fairing, and even with a clip together ply kit you have to avoid wavy panels, make and seal the beam to float joints and teh internal bouyancy chambers etc etc.

    This is why I have long argued that strip plank is a fine method. The age old argument that applying the strips is time consuming is a nonesense in the context of the total time required to build the boat. Conversely "fast build" methods address an issue which is amongst the least important.

    Anyway....</soapbox>
     
  10. jmolan
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    jmolan Junior Member

    Yes thanks for the input. I talked with the company that does CNC work on Brown's skiff www.ptwatercratft.com . He usually has to "place" the pieces so they fit well on a sheet. He also came up with the "jigsaw" joint to replace the scarf. Get a good look at them on the website. Think how nice things will line up with that joint, as opposed to a scarf...... I am learning a lot here. And find the whole idea intriguing.
     
  11. ThomD
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    ThomD Senior Member

    Came across this thread while look for something else.

    I don`t think there is any way this makes sense for a one off. The work load, at least the way I did it was enormous. It is just a load of routine stuff but the work to convert a page of Kendrick`s plans was way more that I had thought, and there was a lot of waste. The waste came from a lot of things. I wanted to CNC the parts, then make up kits so that I could have all the port ama parts, all the starboard ama parts, and so forth, and the parts to those parts. This is not how they are laid out in the plans. Half the aft parts are on one panel, half the mid ama parts are on the next, but the pieces on each panel are not related. That was the right way to do it for the method contemplated. The Kendrick way was based on the first step being the joining of the panels, as with a lot of boat building . Just a minor point that has a huge impact on how you end up cutting things. Of course for a CLC they can get the machine to fit the parts efficiently, but that, and retrieving the parts logically is a whole other exercise.

    Take another thing, the insertion of tabs into the side panels, to register parts. Not really necessary, but since you are trying to do it stitch and glue, it would be nice. Can't remember with the Kendrick, but a lot of these plans don't come with a full set of views. You may not have any idea from a drawing, where parts fit together. You build a form, and assemble the parts over the form. So where do you get the locations on such plans, then you need to know the interface angle, plywood thickness, etc... to get a good fit. Of course tabs are not such a great idea, anyway. Particularly when cut into narrow panels in say an ama...

    Simple build stuff like the tabs, might be talking down a little to the average builder of a big boat, at least as they get to the end of such a construction. These are not just pencil in items, for instance for the tab to have a neat fit it`s geometry is not going to be simple. Meaning 6mm tab fits into 6mm slot, and what 6mm are we talking about. Not all ply is the same size. This kind of thing works with a printed kit, because the maker controls all aspects of the construction. Even then, read the CLC kits article on their life in CNC, it has taken a lot to get them where they are today. Pretty much wiped out my interest.

    Then there is the whole design aspect. When you make a small skiff regular parts cut out of plywood make a lot of sense. You can get stiffness, enough strength, and the simplicity of regular dimensioned materials out of 6 and 9mm ply. This will create a boat with performance and ruggedness than one wants in a small skiff. I believe the approach makes sense for some multis also, particularly if people would just design in the weight cost without assuming every boat has to be capable of sleeping 6 in doubles, while winning whatever is the Ostar today. The problem as has been alluded to, is when you want to build to the potential of ply for weight and stiffness. What you end up with is a Gougeon 35 weighing 2200 pounds. Miraculous, yes, probably several thousand, pieces of wood bonded together. Granted it might be great to have just such a project pre-cut, but it probably isn`t going to leverage a lot of benefit for assembly, it is a very complex structure, not one that can just be jigsawed together. Would the market accept a 24 footer in 3/8" ply, main hull anyway? The weight penalty is probably 45 pounds, or 100 pounds for going to 1/2" If you did that you could reduce the complexity a lot, and cut only a few pieces that would slot together simply enough. You would only have to increase the volume of the boat by the thickness of the heavier planking. But designers tend to build these hulls out of 5-6mm ply to get the fastest boat.

    OK, so in contradiction to the above, we have the CLC boat Madness. Most experienced CNC builders in the business, presumably the kit is great. The price is shockingly reasonable, compared to other boats in their line (and is presumably based on the usual materials and time dynamic). The price is even more reasonable when the quality of materials is considered. I have used mostly crap materials in my multis, you can make a great boat that way, but 1088 is an upgrade however one looks at it. Too bad that the boat is of such limited practical use, (I would have built such a thing in a flash when I started out).

    The other example that comes to mind are some large cat kits that have been produced with CNC, like the Oram ones, when he was in business. They dealt with the limitations of plywood by building with panels of cored material.
     

  12. UNCIVILIZED
    Joined: Jun 2014
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    UNCIVILIZED DIY Junkyard MadScientist

    jmolan,
    The VAST majority of designers work via CAD anymore, & as such many/most will happily sell you a set of mylar patterns for all of the key parts in the boat... Or, simply sell you the design, including electronic patterns for the key parts of the design. From there, it's only a matter of finding someone who has/can hook up a laser to their computer in order to cut out your full size parts, regardless of material. It's been common practice for like 25 years.

    Also, there are a lot of designers out there who are creating their designs as kits, or e-plans (as above) such that the pieces fit together like giant 3D jig saw puzzles. Then it's your job as the builder, is to cove, rove, & tape (or weld) the pieces together. KISS
    Dudly Dix has created a LARGE number of designs which are built in exactly this manner. Have a look at the Didi 950, here http://dixdesign.com/didi950.htm as well as on his blog, where there are build reports on said design/kit http://dudleydix.blogspot.com/
    And here's just a partial listing of his kit boats (designs) http://www.dixdesign.com/kits_plywoodUSA.htm

    As to finding multihulls built in such a manner, sadly, for the most part you'll have better luck looking outside of the US. Like say to Australia, http://www.schionningdesigns.com.au/our-kits & you may have some luck searching through this site for what you're looking for http://www.multihull-maven.com/

    Oh, & to my knowledge (semi-limited) Kurt Hughes is the go to guy for building big stitch & glue multihulls in the US (ones even as big as 60'). He's been doing it & designing them for like 25-30yrs http://www.multihulldesigns.com/ it surely ain't rocket science. - Do a little bit of studying on his cylinder molding technique, & if you're at all curious, the DVD on it could be a good investment for you. The only thing is, his boats aren't kits, & thus, you do the panel cutting yourself.
     
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