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  1. #136
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    Yep, my math is pretty bad at this time of the day. 50 pounds would be a light version of this boat. So anywhere between 22 and 44 kilos, depending on how heavy you made her, species used, decking, thwarts, etc.

    6 mm bottom and 4 mm strakes would be okay, but a delicate boat, plus there'd be a little longitudinal flexing and twisting in some conditions.

    CNC files are difficult to arrange and not cost effective on low cost plans. There would have to be a fair bit of interest in this hull, to warrant setting up a cut file for CNC.

    I haven't done a nesting file on her, but 4 to 6 sounds reasonable with a fair bit of waste.

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  3. #137
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    Thanks PAR. Sorry if I am posting too much Richard. Just that a beach launching coastal rowing boat that sits on the width space on my roofrack is a rare thing.

    I have just been down to the dinghy park after very heavy wind and rain last night and one cover had blow off (temporary one on the Skiff) and the other water logged and stretched. Would really like to just get on the water from home, car top using my Kari-Tek rack. This 14.9 is beginning to fit the bill somewhat.

    http://www.kari-tek.co.uk/ELRRIntroMulti.html

    In my impoverished future I will have to cut costs especially dinghy park costs, club fees, insurance demanded for racing etc. Will not miss it really. Much happier in the old days windsurfing out of the car, no costs, no "club" hassle.

    So, I was wondering what a 42" rowing boat might look like in the flesh. Had a search round and found that the CLC Chester Yawl is very close on length and 42" wide. Just imagine two pointy ends instead of the wineglass transom.



    PAR, I will contact the guy I know who quoted me very reasonable programming costs and per sheet cutting and see how he feels about something like the 14.9. To save buying a whole sheet for the centre plank, could it be doubled up on the hull planks?

    Or, after my recent prototyping problems wait till Richard has built one!!!

    Brian

  4. #138
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    Brian, take it easy with this mania for CNC cutting, all it does is produce pieces cut to predetermined numbers ... and you have to hope you got the numbers right.

    I'll accept that lofting a boat is scary at first but quite doable by the novice. Maybe Paul might consider providing a set of coordinates for the molds (paper patterns being troublesome because the paper moves with humidity). Once you've got your molds however, you are far better off making patterns from your actual boat and cutting your planks to those patterns. In this way, each new plank adjusts for the idiosyncracies of the previous plank and you have a chance to sort out any hard spots or kinks as you go, you can't do that with a precut kit.

    Nor are you saving much time with your kit - you can make a pattern for the next plank, cut and fair a pair of planks (always work in pairs) and glue them in place in a few hours. Sure, a kit means you don't have to do all that, but you still have to wait till the next day for the epoxy to set.

    Spiling planks is easy. Sure, a lot of amateur boat builders and, sadly enough, a lot of people selling their own patented methods make spiling seem complicated and difficult, but that's just nonsense and complexity for complexity's sake. Making a pattern for a plank is simple and the best way of making sure the plank fits YOUR boat.

    Richard

  5. #139
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    I am sure your correct Richard, it's just that I can picture the hull with horrible wavy lines and the whole thing coming out a mess! Doing the Snipefish with a pal is helping a lot. The Snipefish is a two plank single chine stringer design so just about as simple as possible. Still it's taking us ages as we learn so slowly.

    As a past Production Manager, good tooling was the secret of repeatable quality production, so I just come from that viewpoint. Just reading the "Stitch and Glue Boatbuilding" book by the guy who started CLC. Now realise how their LapStitch works, with the upper panel sitting into the rebated end of the panel below, thus using less tape and gaining the clinker look.

    I would also like to put a small volume rowing boat such as this into small scale "production". It's just something I seem to want to do, daft really. You can sense that recreational rowing could take off, and for England that has to be coastal/ estuary. Scotland now has river access for all, something we are denied.

    Don't mean to divert things - 14.9 is looking very good.

    Brian

  6. #140
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    You're not diverting things Brian, this is useful.

    Stitch and glue is a different animal to lapstrake - there the shape of the panel is critical to the final result and it's a good use for CNC.

    Sorry, Lapstitch seems to me just a way of making lapstrake complicated. It introduces processes and requirements that are un-necessary.

    Pure lapstrake does not rely on 'accurately' cut pieces. In many ways, it demostrates one of the of the myths about accuracy ie, accuracy is only about reproducing numbers. CNC is very good at reproducing numbers, but how good are those numbers in the first place? Just taking them off a computer model isn't always good enough.

    In the case of Paul's double ender, the 'numbers' would be good enough to get the shape of the molds (I think). Cutting the molds probably is an area where a CNC cutter might be useful. However, once you have a strong back set up with a line of molds bolted in place, you need to determine where the plank lines run. Far and away the most accurate tool we have for doing this is the human eyeball aided by a batten. In fact, that same eyeball combined with battens is the best tool for ensuring that your molds are accurate and for making them so if they aren't. We can see deviations that just aren't apparent when looking at a computer model. I'm sure there are programs that can smooth all this stuff out for us but you don't need that stuff, you've got your eyeball. Even CNC cutting will have sufficient errors to create wiggles in the lines - you'll still need your batten and eyeball to fine tune things ... if you bother that is (and I suspect most kit builders won't).

    Once you've determined the plank lines, ie, where they run along the molds, the rest is easy. The planks overlap each other so there is no need for super precise edges. However, if one plank goes on slighly wrong, and the twists mean that they always need massaging into place (it's not like fitting two dimensional pieces together) the shape of the next plank will be affected. The overlap means that this isn't critical but if you're working with a precut piece of timber, you're stuck with what the original numbers give you. By taking a pattern from the boat, you get the opportunity to ensure that the new plank gives the fairest fit to the boat and again, this is done by eye. How do you get that pattern? Whack a lump of cheap ply on the boat and draw around the edge of the existing plank and a batten on the other side of the new one with a pencil - there's not much to it.

    CNC cutting is a great way of producing kits - once the original set of numbers has been created, you can bang the things out without the hinderance of human handling. It's a great production process, but all it's doing is automating a process to produce a set of average fitting parts. Doing it by hand allows you to produce the best fitting parts ... and also to make a massive cock of the whole thing.

    Lapstrake seems scary until you've done it ... or it should be. Unfortunately, many amateurs and quite a few people promoting their own patented systems (such as lapstitch) turn it into a complicated mess. The reality is that it's a very simple method and to be honest, no harder than stitch and glue or even chine log building, it's just different with a few more planks to put in (you get bored after the fourth plank).

    Richard

  7. #141
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    Richard has it about right. CNC is wonderful, particularly if you need several of the same thing. Yes, I provide mold dimensions with the plans set. Even with perfectly CNC cut molds and planks, you'll have alignment and other issues that will toss off the plank runs. Having just one mold a fraction off it's line on the strong back or maybe a slight bit off plumb, can be enough to cause a hump or hollow to appear in the plank runs when you start hanging lumber. So much for machine precision when a human erects the molds.


    Lining off isn't difficult and it's fairly enjoyable. The same is true of making station molds. These things seem difficult, but once you've actually tried it, you wonder what the fuss was all about.

    The same is true of lap strake building. It has a mystery and air of difficulty about it, but really it's not hard. You just have to get you head around the processes. Once you've hung a plank or two, the mystery goes away and with glued lap, much of the difficulty does too.

    Back to CNC work, most of the time, it's rare that the first run comes off with perfect parts. There's a glitch or two, maybe in the cut file, maybe in the original work, but in either case you've got some useless molds. This is material and machine time someone has to buy, just to test the process. Eventually you end up with a perfect set of parts from a refined cut file, now what? You can hope that someone will want to buy those pieces, but how often does that happen? In any case, I'll do CNC files for custom design work if requested, but unless there's a batch of clients beating on the door for a particular boat, I'm not in a hurry to add this feature to my stock designs.

    A final note about machine cut pieces would be, there's a great deal of satisfaction we get, convincing a bit of lumber to be a boat part. The tactile sensations of finding imperfections with your fingers, not your eyes, electing to skip a batten's "tick" mark or two, so it lies fair and sweet, even though the offsets say something else, but your eye's know better. Many things about boat building haven't as much to do with machine cut precision as they do tempting the senses of a builder's sole. I'd rather not have a cut file rob me of this enjoyment, even if it means I'll cuss over the blade being on the wrong side of the line every so often.

  8. #142
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    Son thinks it's somewhat like the Herreshoff Rowboat in Gardner's book, plank keel and all

    http://images.google.co.uk/imgres?im...a%3DN%26um%3D1



    Gardner version


    http://images.google.co.uk/imgres?im...a%3DG%26um%3D1


    Brian

  9. #143
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    Richard and PAR, thanks for your good advice, makes a lot of sense. Lets not run before walking.

    As a kid I guess I made up Airfix models, not planes from solid balsa. Lots of people must enjoy making up kits boats as well, CLC and Pygmy must prove something.

    It is nice to know though, that, well you know, just if......

    Brian

  10. #144
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    Quote Originally Posted by keyhavenpotter View Post
    As a kid I guess I made up Airfix models,
    Then you'll understand all about bits that should fit together but don't quite

    I've been a model maker all my life and kits have always been the bane of my life thanks to poor cutting of the parts (and daft design but that's not a problem here is it Paul ). CNC promises that such problems shouldn't exist but ...

    Kits are for people who've chosen not to cut the pieces. I haven't built a kit boat, nor do I have any interest in doing so, but I have build kits of model aeroplanes and you know something, they rarely made any real difference to the overall build time. Oh sure, if you're being paid by the hour there's a difference, but if you're working on amateur's time using the sort of time scale that says "I started in May and finished a year after I hoped to", kits don't actually do much.

    Besides, building the hull is such a small part of the overall build process, even in this simple rowboat.

    And you're right, Paul's 14.9 does look like Herreshoft's rowboat

    Richard

  11. #145
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    14.9 and the Herreshoff have a few things in common, the most obvious are the shape of the sheer and rocker. The keel plank on 14.9 is wider and the actual beam is comparatively narrower, as I included the rub rails, the planking is about 40". Freeboard is about 19" at the bow, which is proportionally taller for the longer Herreshoff and the ends are fuller above the water line.

    The biggest differences are weight and volume distribution. A very lightly built Herreshoff with 3/8" solid lumber planking and dainty frames would be in the 150 pounds range, though most would be around 170 pounds. This is a pretty heavy boat to car top.

    The Gardner/Herrsehoff rowboat is heavier still, because he did two things to the Herreshoff model. He made the keel plank wider (22") and added a lot of volume in the forward sections, above the LWL. He also raised the sheer a little too.

    If the Herreshoff used softwood laminated ribs she would be a fair bit lighter. The stems could be built lighter too.

    Thee is no discounting the beauty of both the Herreshoff and Gardner boats. I've seen them built with as few as 5 planks (typically the Gardner) and as many as 8 per side. 7 seems about right for the longer Gardner, I've used 6 on RYD-14.9, though she'd look nice with 7 too.

    Side by side, you'll see differences between all three boats. The most obvious is 14.9 will be the smallest. She'll be "stiffer" then the Herreshoff underway, but not as stiff as the Gardner. The Gardner will look much fuller in the ends at the sheer. 14.9 will be the lightest and look noticeable leaner then the Gardner, but maybe not as much as the forefoot on the Herreshoff. I suspect the RYD-14.9 will be slightly more maneuverable, but not as much as say a narrow bottom guide boat of similar proportions.

  12. #146
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    You know Paul, that's the sort of information a buyer of your plans would really appreciate. It's hard for most of us to appreciate the finer differences and to have them explained like that makes the build just that little bit more special.

    Richard

  13. #147
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    Thanks PAR for that insight. Richard, your original post really seems to have come up trumps, as we say.

    40" beam is the same as the Solway Dory sailing canoe I had. They have a rowing system for their canoes as well.

    Thought you might enjoy seeing their new web site with super video of their Shearwater (16' x 40") fast reaching. Note the use of outriggers which are clear of the water most of the time. They use these on large stretches of open water and on the sea.

    http://www.solwaydory.co.uk/videos/10

    Brian

  14. #148
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    Brian, with the 14.9 I think you could avoid rowing cross oared with 8ft oars and some spacers on the rowlocks.

    One thing about cartopping the guideboat, I carry it on saddles right way up as when inverted the ends hang down in front of the windscreen. This may not be a problem with the 14.9, how would you mount it on the Karitek racks?

    Brian, was it you who asked about guideboat plans? This book http://michneboat.com/ has an appendix with very detailed plans and offsets of a Grant guideboat and there are less detailed drawings and offsets of a Rushton Saranac Laker guideboat in the appendix of this book http://openlibrary.org/b/OL8048942M/...rican-Canoeing . There is an analysis of the two designs at http://www.guideboat.ca/16ft_guideboat.html which also sells plans for a simplified S&G version.

    Kelvin

  15. #149
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    There is an article on using the Kari-Tek here

    http://ukhbbr.wordpress.com/how-to-d...e-built-boats/

    It uses the standard rack plus 4 small mounts which bolt to the rack and are designed to carry an inverted canoe. Cannot quite see them on the web site though.

    Thanks Kelvin for the links.

    Brian

  16. #150
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    RYD-14.9 has much less sweep in the sheer then a typical guide boat, so I think upside down car topping would be possible, more so if the rack had some height off the roof.

    I think guide boats would be a good choice, if alterations where made, to address the needs of an open water craft. RYD-14.9 carries a lower prismatic coefficient then the two guide boats in that analysis article. Those (newer designs) carried too much in my opinion, for the S/L they'll be expected to propel at. Even with a small outboard, you'd be hard pressed to take advantage of these high Cp's, so you're just creating drag, which he apparently confirms at the end of the article, finding his studies brought him full circle back to antique design formats. 14.9 is in the .56 range and just about right for a displacement mode craft with the potential to slip past the hull speed limits every so often, like down the face of a wave or with an especially powerful stroke.

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