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Thread: Is it possible to cut this with CNC?

  1. #1
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    Default Is it possible to cut this with CNC?

    Two quarters of a stitch and glue double ended rowboat hull nested on a plywood sheet.
    boat example.jpg

    The boat will look something like this (not the same boat but similar concept)

    boat examle perspective.jpg

    The hood ends will need twisting and a tiny bit of torture, but not as much torture as single-chine boats built using this method.

    The gaps need to taper to nothing and then stop about halfway through the panel, but I could not get Freeship Plus 3.4 to draw it that way. I'm planning on further processing the Freeship output with CAD, and am still researching possibilities. Dassault System's AutoCAD clone will read .dxf files but isn't very beginner friendly. I don't need a lot of bells and whistles, just a way to stop the lines where the gaps stop and to erase/add gridlines and measurements.

    The general concept is sound; I've cut two similar hulls from 4mm plywood and successfully folded them together and hope that it works with 5mm and 6mm ply also.

    I haven't been completely happy with any of the saws I tried and am exploring other options, especially ones that might come into their own if building multiple boats.

    Would it be possible to CNC this with a really thin router bit that could create tapering"dead end" gaps of less than 1/8" (3 mm) width at the end? If not, would other CNC cutting methods, like laser, work for this?

    Is there anything like CNC 101 where I could read up on the requirements, possibilities and limitations of CNC? I'm not interested in having my own machine, but am very curious as to what's involved.

  2. #2
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    Default Re: Is it possible to cut this with CNC?

    A laser would cut it with no problem and have a kerf of 1/64". The issue is finding someone with a bed large enough to do the job.

  3. #3
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    Default Re: Is it possible to cut this with CNC?

    I modified a Freeship development in Dessalt Draftsight to nest planks and as it was a glued clinker design I was able to add the laps and cut one strake with a scarfing allowance to better fit the ply sheets.
    It really is quite difficult to build an ugly wooden boat.

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  4. #4
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    Default Re: Is it possible to cut this with CNC?

    Beside the large enough bed the bigger problem is the waterproof glue. It does not laser well so you need the biggest laser you can find in order not to have badly charred edges. I would look for an over 150W laser. Do a test run with your chosen ply.

  5. #5
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    Default Re: Is it possible to cut this with CNC?

    Quote Originally Posted by Rumars View Post
    Beside the large enough bed the bigger problem is the waterproof glue. It does not laser well so you need the biggest laser you can find in order not to have badly charred edges. I would look for an over 150W laser. Do a test run with your chosen ply.
    Interesting! So CNC may be an option to investigate further. At least it gives me a starting point for talking to actual shops. It seems to be mostly sign places that use CNC and Google reveals a sign shop with a 5x10' CNC router in my town. Unfortunately the closest place advertising a laser is a whole day's drive away.

  6. #6
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    Default Re: Is it possible to cut this with CNC?

    Quote Originally Posted by Peerie Maa View Post
    I modified a Freeship development in Dessalt Draftsight to nest planks and as it was a glued clinker design I was able to add the laps and cut one strake with a scarfing allowance to better fit the ply sheets.
    Thanks Nick, that's the program I downloaded, probably based on your mention of it in another thread. I tried it out for maybe a couple of hours, just couldn't figure out how to select a piece of a line and then delete it. I've never used CAD before, and the terminology is just so different from any other software that I'm familiar with. Have you seen a tutorial or something on it? It also doesn't help that my home computer isn't connected to the internet but I cannot download any software on my work computer. Freeship has a bit of a learning curve for the finer points, but I felt that I got a bit functional with it much more quickly. The Freeship instructional pdf is a bit basic but for the most part very helpful.

  7. #7
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    Default Re: Is it possible to cut this with CNC?

    I'm having a hard time seeing the detail on the image. Are there two pieces to be cut from a 4x8 sheet, each piece with a slit on one end? How thick is the plywood...1/4"? The slits can be cut as part of the vector, but the bit would stop whenever the slit gets narrower than the bit being used. From there you'd have to finish the slit with a hand saw.

  8. #8
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    Default Re: Is it possible to cut this with CNC?

    Quote Originally Posted by BOI View Post
    Thanks Nick, that's the program I downloaded, probably based on your mention of it in another thread. I tried it out for maybe a couple of hours, just couldn't figure out how to select a piece of a line and then delete it. I've never used CAD before, and the terminology is just so different from any other software that I'm familiar with. Have you seen a tutorial or something on it? It also doesn't help that my home computer isn't connected to the internet but I cannot download any software on my work computer. Freeship has a bit of a learning curve for the finer points, but I felt that I got a bit functional with it much more quickly. The Freeship instructional pdf is a bit basic but for the most part very helpful.
    If you left click on a line it will be selected. Then go into the modify menu. I suggest that you just play with it without saving any changes until you find your way around.
    Explore the use of layers as well, that can be really useful.
    It really is quite difficult to build an ugly wooden boat.

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  9. #9
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    Default Re: Is it possible to cut this with CNC?

    I would find the person a CNC machine who is able to do the job and send them the dxf the file to them to look at. The guy that is running the machine will be best answering what he can and will do with his machine. When I did this for a similar project the CNC worked out costing too much and I made a template and a router. IMHO CNC is for of value for intricate parts like interlocking frames etc.

    Laser would work well for thinner stuff but finding a bed that size will be an issue. You can lower the watts and do multiple passes.

    I appreciate the tapered ends are an issue, a template and Japanese saw combined with chain drilling or template and Dremel with a 561 cutting bit would work and their router attachment work.

  10. #10
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    Default Re: Is it possible to cut this with CNC?

    I know nothing about lasers,but have a bit of experience with routers.There shouldn't be any difficulty with cutting the outline and ramping up or down is no problem.The very narrow cut will require the use of a correspondingly small cutter and it will have to run at a fairly low feed speed and maybe a couple of passes.A good operator and a good CAM program might use a conventionally sized cutter for most of the outline and switch to the very small tool for the extremely narrow zones.

  11. #11
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    Default Re: Is it possible to cut this with CNC?

    How many do you want to produce? For small numbers, do most of the cutting by CNC with a 5 or 6mm cutter, then finish the tapered cuts by hand with a Japanese saw.

    Leon

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    Default Re: Is it possible to cut this with CNC?

    Or loft full size on the sheets and cut it out with a Japanese pull saw.

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  13. #13
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    Default Re: Is it possible to cut this with CNC?

    Has anybody here seen a Maslow CNC? not sure how accurate it would be in this case. Perhaps cut 1/8" proud, then block plane back to a paper pattern?

    MaslowCNC.jpg

    Pretty affordable, and because they work on a nearly vertical plane, they take up less space in the shop.

  14. #14
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    Default Re: Is it possible to cut this with CNC?

    I keep seeing substitutes for CNC full size machines and have yet to be convinced that any of them are worth having.A used Shopbot would cost a bit more and be many times better.Anything hung on wires has some susceptibility to twisting under cutting torque and I doubt you could ramp into a cut or cut 3D shapes with it.

  15. #15
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    Default Re: Is it possible to cut this with CNC?

    I have been to West Port Yachts Port Angeles, they regularly cut out dovetails with a CNC router. No problem
    PaulF

  16. #16
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    Default Re: Is it possible to cut this with CNC?

    Quote Originally Posted by BOI View Post
    Thanks Nick, that's the program I downloaded, probably based on your mention of it in another thread. I tried it out for maybe a couple of hours, just couldn't figure out how to select a piece of a line and then delete it. I've never used CAD before, and the terminology is just so different from any other software that I'm familiar with. Have you seen a tutorial or something on it?
    There's a tutorial series on it at Lynda.com that you might find helpful as an overview. There's also some CAD/CAM tutorials on the site.

  17. #17
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    Default Re: Is it possible to cut this with CNC?

    Quote Originally Posted by John Meachen View Post
    I keep seeing substitutes for CNC full size machines and have yet to be convinced that any of them are worth having.A used Shopbot would cost a bit more and be many times better.Anything hung on wires has some susceptibility to twisting under cutting torque and I doubt you could ramp into a cut or cut 3D shapes with it.
    ++ to both of these points.

    I've seen demos of some tabletop home CNC machines and they are great fun, but extremely limited in the sizes in which they operate. To get to the point where you can CNC mill a piece of plywood to cut panels, you're talking about investing an awful lot of money.

    That gizmo with the two wires....I have serious doubts.

    Now, what you can do is take your .dxf files to one of the big sailmaking houses. They can cut out extra-thick mylar patterns for you. You pin those down to your plywood and draw your shapes. Then cut as needed.

  18. #18
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    Default Re: Is it possible to cut this with CNC?

    Thanks so much everyone! I have since found out that the closest CNC machine is a whole day's drive away. It is a router and the smallest cutter they have is 1/8" in diameter, so maybe it's not worth it. The ad that mentioned one in my own town was a mistake of yellowpages.ca. I'm definitely not purchasing or building my own CNC of any sort.

    I've tried various saws. While it is totally possible to saw the panels, it is more difficult to get perfection if your saw cuts are a bit wobbly. In the meantime I will make do and figure out how visible a bit of wobble will be on the boat.

    The circular saw works great for very gentle curves but needs a guide firmly clamped or nailed down, which is time consuming, and the saw kerf is widest with this saw. With the Japanese saw I struggled to hold it totally vertically when cutting four layers of 5mm ply at once, that's over 3/4' total thickness. The jigsaw has been the best so far but if I oscillate it more the cut gets wider and more imprecise, if I reduce oscillation it vibrates more and goes extremely slowly.

    Maybe a better jigsaw would do the trick. I also haven't tried using the jigsaw with a clamped-on curved guide yet.

    Perhaps, if I ever find myself with the need of building several boats of the same design I may want to get the guide CNC cut. Would be great to just be able to clamp it on and cut, without even needing to draw the panel layout first.

    In the meantime, the suggestions of tutorials for Draftsight will be followed up on as I have the time.

  19. #19
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    When I first started my apprenticeship, pre cnc, we were selling kayak and canoe kits. We built a jig for a hand held router, the jig consisted of a base board of MDF and 19x19mm timber arranged to represent the profile of the panel to be cut, glued and screwed to the base board. It was a simple matter of temporarily screwing the ply to the jig and following the profile below with the router.

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