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#1
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100% Plywood Carvel Hull?
Hi,
I've been doing a lot of thinking recently about building a sloop with classic lines. It's not the first time this has crossed my mind but the idea just will not remain dead. I recently replaced the cockpit sole in my 'classic' soling and upgraded the sail controls. Now the crew only moan about my driving and not about putting their feet through the floor or the condition of the sheets. While working on the sole I did some investigations into having plywood CNC milled. It's not that expensive! I also prefer engineered wood to natural timber. With this new found info my mind quickly raced into overdrive. In theory it should be possible for me to design and build a carvel hull from plywood without me having to do much more than glue and clamp, no measuring no cutting, think lego not woodwork. Here's the way I'm thinking. Alignment. If two pieces of plywood are to be joined then an accurate means of locating them needs to be done. I'm thinking the use of dowels with the holes reamed on the CNC machine. Two dowels would locate any join. Scarfing. You can mill the 12:1 ratio into the plywood along with the alingment holes for dowels. Epoxy the scarf insert the dowels and clamp. Keelsome, ribs, beams etc. These could all be made from laminates pre milled on the CNC. Again epoxy, dowels and clamp. Planks. Scarf joints as above. Rabits milled. Even the holes for rib screws could be pre drilled/counter sunk on the CNC machine. If all the majority of the time building a fair hull is spent in the measuring cutting stages would not the above method produce a such a hull in less time than other methods. Also it would be easily repeatable. I think I've given enough details for people to get the idea. Now what is obviously wrong with this idea? Does anybody have existing examples? |
#2
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Hi
It is very nice to be able to mashin various things in plywood, my experience though is that the most important issue when building a boat are the framework. Check this link to find a very different attitude towerds what make the foundations to place the panels upon. http://groups.yahoo.com/group/Cyber-Boat/ P.C. |
#3
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On 24 Jul 2005 04:55:46 -0700, "
wrote: Hi, I've been doing a lot of thinking recently about building a sloop with classic lines. It's not the first time this has crossed my mind but the idea just will not remain dead. I recently replaced the cockpit sole in my 'classic' soling and upgraded the sail controls. Now the crew only moan about my driving and not about putting their feet through the floor or the condition of the sheets. While working on the sole I did some investigations into having plywood CNC milled. It's not that expensive! I also prefer engineered wood to natural timber. With this new found info my mind quickly raced into overdrive. In theory it should be possible for me to design and build a carvel hull from plywood without me having to do much more than glue and clamp, no measuring no cutting, think lego not woodwork. Here's the way I'm thinking. Alignment. If two pieces of plywood are to be joined then an accurate means of locating them needs to be done. I'm thinking the use of dowels with the holes reamed on the CNC machine. Two dowels would locate any join. Scarfing. You can mill the 12:1 ratio into the plywood along with the alingment holes for dowels. Epoxy the scarf insert the dowels and clamp. Keelsome, ribs, beams etc. These could all be made from laminates pre milled on the CNC. Again epoxy, dowels and clamp. Planks. Scarf joints as above. Rabits milled. Even the holes for rib screws could be pre drilled/counter sunk on the CNC machine. If all the majority of the time building a fair hull is spent in the measuring cutting stages would not the above method produce a such a hull in less time than other methods. Also it would be easily repeatable. I think I've given enough details for people to get the idea. Now what is obviously wrong with this idea? Does anybody have existing examples? This method is apparently in use for plywood kayak kits, all beautifully precut into numerous swaths for multi chine hulls. So the problem is not practicallity I don't suppose - but rather commercially worth while volume. Brian Whatcott Altus OK |
#4
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If it works for plywood panels it should also work for fibreglass panels, aluminum panels, and steel panels - any sheet goods. Where do the panels get the strength to hold the shape of the hull? -- ------------------------------------------------------------------------------ William R Watt National Capital FreeNet Ottawa's free community network homepage: www.ncf.ca/~ag384/top.htm warning: non-FreeNet email must have "notspam" in subject or it's returned |
#5
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Hi William,
the laminated ribs should provide the shape of the hull, just the same as traditional plank on frame construction. |
#6
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Hi Brian,
I don't have any plans to do this commercially. But for home construction it would be nice to complete a hull in a more timely manner than is currently possible. |
#7
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Hi.
With small hulls you most often can rely on the panel strength , you hardly need any ribs and having no ribs also mean that you can't make the most important part in terms of creating structural strength, -- the stringer. But at some point with just some size boat hull, you will need the box structure at some point you can not rely on only the "strength" of the panels, you need a few stringers ,an extreme strong part of the boats structure , then the box structure follow the shape of the hull as it is made panel-rib-stringer. A 3D-H framework are making it all into a box structure. Now if you are not to build the hull anyway, you can say whatever you want, --- but if you realy want to do reliable works drawings, you need to know and understand the feature that nomatter what modern material, are the fundamental part of it -- the box structure created as soon you strongly attach a stringer. Now you can make all the most fancy drawings you please, but fact is, that when you understand the fundamentals , what make the hull, from a shivering collection of panels, into a rugid structure ;-- with the 3D-Honeycomb you both avoid the lofting and get a set of frames that will form just any shape keep that shape while you slot assemble the frames so each frame are allready from the basics , supporting and supported by all other frames, one huge collection of ready to cover cubes, and at the same time, when you cover inside and outside with panels, you get a boat hull capable of twisting , something that only add speed btw. a sort of strength that is very important for a boat hull , The most important issue building from panels and frames are, to have a reliable framework to attach the panels, a framework that will not bend or move, a 3D-Honeycomb framework produce just that, produce an extreme strong framework for any shape hull. ------ insert a 3D model of the engine ,subtract that from the 3D model and when frames are cut and assembled, the engine bed are there allready. P.C. |
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