Little Red Hen - Clinker Dinghy

Discussion in 'Wooden Boat Building and Restoration' started by goolawah, Jan 14, 2009.

  1. goolawah
    Joined: Oct 2005
    Posts: 96
    Likes: 5, Points: 0, Legacy Rep: 67
    Location: Brisbane, Australia

    goolawah Junior Member

    Hi Folks,

    Chatting with a few fellow wooden boat enthusiasts some time ago, it dawned on me that many of us would like to have the experience of building a traditional clinker boat, without any of us necessarily wanting to add yet another boat to our fleet.

    Personally, I was driven by Andrew Denman's example. Wouldn't you love to build boats like that?

    The conversation, which progressed over several months, recognised that a group project would be one way to do this, but that there were a few obstacles. Firstly, how do you get a bunch of crusty 'old salts' to agree on the best plan from the best designer? That could take years to resolve. Then, where could you build it that was truly a shared experience? It could take quite a long time, and if it got built in any one person's garage it would become 'his' boat, and we couldn't have that. Next, how would we fund the project if nobody was going to 'own' the result (or, possibly, take responsibility for a disaster)?

    While we all agreed that it was a good idea it was going nowhere, so I decided to overcome the first obstacle by designing the boat myself. Having successfully designed and built our little stitch and glue, nesting dinghy Curlew, I thought I could take what I had learned about 'boat CAD' and design a traditional clinker dinghy of about the same size (10ft or 3metres), but with more 'conventional' lines.

    As I thought this through, and played about with FreeShip software, I started to see some other advantages. This was a way to get really engaged with the design process. I also wondered about the possibility of producing detailed dimension drawings of all of the individual components, so that each participant could make a part that suited their capabilities, in their own workshop, and they could all be brought together for final assembly. This would overcome the storage and workspace problem. If participants supplied their own materials it would also overcome the funding problem, at least for a start.

    As the design evolved I contacted potential participants to see if they would like to be involved in the project (which I named 'Little Red Hen' for motivational reasons obvious to those who know their folk tales). There was some scepticism regarding its feasibility, but general agreement and, after some consultation about material sizes etc, I punged into details of the design.

    Once the basic dinghy lines (below) were established I acquired a copy of TurboCAD Pro and started exploring the possibility of exporting the 3D hull shape from FreeShip and doing the structural design in TurboCAD.

    I'll add more posts about progress as time permits. And it could take a long, long, time.
     

    Attached Files:

  2. Landlubber
    Joined: Jun 2007
    Posts: 2,640
    Likes: 124, Points: 0, Legacy Rep: 1802
    Location: Brisbane

    Landlubber Senior Member

    ahhhh he has seen the light, nice one mate!
     
  3. goolawah
    Joined: Oct 2005
    Posts: 96
    Likes: 5, Points: 0, Legacy Rep: 67
    Location: Brisbane, Australia

    goolawah Junior Member

    Aaah, I remember you. You're the one who complained bitterly that my little Curlew nesting dinghy was a Big Mac boat. :p

    Well, here's your opportunity to get really involved, hands on, with helping build a more classic craft. It's happening in Brisbane so you're close to the action. When you see something that takes your fancy we we progress, send me a PM as we'll see how you might be involved.

    One of the biggest challanges will be sourcing timber for the planks. Can you help? Do you have a workshop?

    Quite a few components have been spoken for, but there are plenty more to come, as you will see. It should be interesting and fun!

    Cheers,
     
  4. liki
    Joined: Nov 2008
    Posts: 220
    Likes: 12, Points: 18, Legacy Rep: 114
    Location: Finland

    liki Senior Member

    I am at the same stage with my own design process. I evaluated a number of affordable 2D and 3D CAD programs, I decided that Deluxe was too limited and Pro too expensive, so ... For now I have access to AutoCAD.

    Please let me know how the TurboCAD works for this task, I'll have to consider acquiring it. ViaCAD would work otherwise but I didn't succeed exporting my hull from FreeShip and I don't want to limit the transfer to offsets.
     
  5. goolawah
    Joined: Oct 2005
    Posts: 96
    Likes: 5, Points: 0, Legacy Rep: 67
    Location: Brisbane, Australia

    goolawah Junior Member

    Hi Liki,

    The process worked fine with Curlew. See the study plans attached to that thread. I did all the design in FreeShip and built from those plans. I tranferred to TurboCad after she was built as it was the best way to produce publishable, dimensioned drawings, in case anybody else wanted to build one, and in preparation for this project. Of course, Curlew was all plywood, no solid timber.

    With LRH I struck a problem with TurboCAD 12 using the facility to loft a series of profiles into a solid (e.g for the stem). The lines joining the vertices of the profiles all got crossed over. I reported the problem to TurboCAD and they fixed it in the next version (V15). I was pretty impressed with their response.

    I have no experience with AutoCAD so can't give comparative info.

    Watch this space.....

    Cheers,
     
  6. goolawah
    Joined: Oct 2005
    Posts: 96
    Likes: 5, Points: 0, Legacy Rep: 67
    Location: Brisbane, Australia

    goolawah Junior Member

    Progress

    Coming up with some more-or-less 'classic' dinghy lines is one thing, but it is not a plan for a boat. A true traditional boat builder could do it all from a table of offsets but we have no room for lofting, and no materials yet, so we are substituting CAD for lofting with the idea of producing detailed plans we can build from.

    When you build from purchased plans you get clear information about required timber sizes. If you start from scratch you must determine this yourself. I guess the proper way to do it is to do the engineering calculations about stresses and material strengths. But, if you're not an engineer, how do you do it. For a start, non-laminated wood is not a very predictable material so you would have to allow a greater margin than with manufactured materials like steel or carbon fibre.

    Well, this boat is hopefully going to use 'traditional' timber so we should probably adopt a 'traditional' approach i.e. 'Rule of Thumb". Curlew was the same size, used 6mm plywood bottom and bulkheads, and 4mm ply planks. She is extremely rigid so that provided a starting point. The next step was collaboration with other participants so that we gained from some collective experience and wisdom. For starters we agreed on 19mm for the transom and skeg, 30mm for the stern knee, 100 x 10mm for the hog, 50mm stock for keel and stem (hopefully a grown crook for the stem), and 6mm planking.

    It took a bit of figuring out how to transfer the lines from FreeShip to TurboCAD. I then started 'virtual construction' of the backbone, within the hull shape, according to the agreed dimensions.

    The pix below give an idea of the process but, as with anything to do with building your own boat, it was accompanied by much weeping and wailing and gnashing of teeth. At least when things go wrong there is no valuable wood being destroyed.

    Cheers,
     

    Attached Files:

  7. Landlubber
    Joined: Jun 2007
    Posts: 2,640
    Likes: 124, Points: 0, Legacy Rep: 1802
    Location: Brisbane

    Landlubber Senior Member

    You're the one who complained bitterly that my little Curlew nesting dinghy was a Big Mac boat.....yep, that was me, although I doubt the "bitterly" section...
    I work and live most of the time in China now (last few years boatbuilding in 5 different yards), and am currently project managing a new 120 foot explorer motoryacht.
    If I was at home in Brisbane I would love to spend time helping wherever I could. All the best with your "real" boat mate......oh, and welcome aboard.
    It is nice to see someone get into long pants after wearing shorts sooooo long......
     
  8. goolawah
    Joined: Oct 2005
    Posts: 96
    Likes: 5, Points: 0, Legacy Rep: 67
    Location: Brisbane, Australia

    goolawah Junior Member

    This is, of course, a classic motor yacht built from traditional materials? :D
     
  9. Landlubber
    Joined: Jun 2007
    Posts: 2,640
    Likes: 124, Points: 0, Legacy Rep: 1802
    Location: Brisbane

    Landlubber Senior Member

    Well it certainly isn't Stitch and Glue!

    Nup, it is steel hull with alloy super, singly main engine, mid speed diesel, cruise at 12 knots......very comfortable.
     
  10. liki
    Joined: Nov 2008
    Posts: 220
    Likes: 12, Points: 18, Legacy Rep: 114
    Location: Finland

    liki Senior Member

    Thank you for those images, they certainly were the most helpful. After going through some more AutoCAD tutorials I found out that the problem was that I tried to work with the DXF 3D mesh export which was next to impossible. I guess it could be doable with some other 3D software?

    After exporting using only polylines I got the ball rolling and that precision is more than certainly enough for me.
     
  11. goolawah
    Joined: Oct 2005
    Posts: 96
    Likes: 5, Points: 0, Legacy Rep: 67
    Location: Brisbane, Australia

    goolawah Junior Member

    More Progress

    Hi Liki,

    That's the approach I ended up with after similar frustrations. Fortunately now pretty settled into TorboCAD.

    Questions arise about details like plank lap width and stem rebate bevel width. We've had a few emails and phone conversations around our little group and discovered a surprising diversity of ideas about what constitutes a 'Classic Clinker Dinghy'. My inclination is to use grown crooks for stem and knees, solid timber planks, and copper fastenings. Maybe even produce a 'hewn' keel and stem using broadaxe and adze (on a boat this size?) At the other extreme there are those who prefer plywood planks and a laminated stem on the basis that glued lap-strake ply would still 'look' classic. Then there are all the possible variations in between.

    Of course, it all comes down to availability (and cost) of materials. In the early 1900s there was an abundance of suitable timber for boat building in Brisbane. Great slabs of beautiful straight grained timber, in wide boards, from big trees. Just look at some of the old VJ wallboards from an old Queenslander. It's a bit harder to find these days.

    We are also hoping to keep the cost of this project under control by using 'found' or re-cycled materials so perhaps we can recycle some of those old VJ boards (130mm x 19mm) into planks. Will 130mm we be wide enough for Garboard and Sheer strakes? If not, we might have to use ply. Can we find a suitable grown crook for the stem? If not, we might have to laminate it.

    To help us get real about this, one of our group has made a very nice 10:1 scale model from the plans so far (see pic 1). This helps get us out of the 'virtual' CAD world and actually start bending strips of paper around he moulds to see how it behaves. Wonderful learning experience!

    We sort of agree that, with 6mm planks, the width of the lap and the stem rebate should be about 18mm. At least this will do as a starting point. The problem with testing this on a 1/10 scale model is that you can't realistically scale the thickness. So, it's back to CAD actually apply the 6mm plank width to the moulds in such a way as to end up with 18mm laps and an inner lip about 1mm (rather than a feather edge).

    The hull profile from FreeShip started as a new hull 3m long by 1.2m wide with 0.15m draft, then 'tweaking' until it looked more 'classic'. I paid no regard to the practicality of planking it. It turned out I had made the turn of the bilge much too tight a radius. This meant that the exposed plank width at the turn of the bilge would be about 36mm (see pic 2). This sharpish curve might be OK for strip planking but I worried that for a clinker hull it might look odd due to the great variation in plank width. So it's back to the drawing board. But first, we need a better understanding of the relationship between plank thickness, lap width, lip thickness, and bilge radius.

    As an exercise I drafted up an example (see pic 3). In both cases the planks are 6mm thick, the lap 18mm wide, and the inside lip 1mm. A plank width of 75mm thus generates a radius of 251mm. A plank width of 100mm generates a radius of 367mm. (Yes, I know they're lapped upside down, it's just an exercise). This is all probably blindignly obvious to everyone else, but I have my own ways of figuring stuff out. So, moving on.....

    Armed with this clearer insight I have 'tweaked' the curve of the bilge so that the narrowest exposed plank width is now 52mm and the planks are more similar in width (see pic 4). I still wanted to retain a bit of 'hardness' in the bilge for the sake of stability, so I haven't gone so far as to make it a simple arc as in the test exercise above.

    These changes have necessitated re-drafting the bevels on the keel, hog and stem. I thought I had better check the result for reasonableness, so ran a few splines arond the moulds to see how it looked (see pic 5 and 6). I think we'll go with that. It's a bit of a pain, but better than discovering the problem after the materials are cut.

    I guess that actual laying off of the planks will be whatever eventuates, but at least we have better understanding of the issues, and increased confidence that they will look OK.
     

    Attached Files:

  12. goolawah
    Joined: Oct 2005
    Posts: 96
    Likes: 5, Points: 0, Legacy Rep: 67
    Location: Brisbane, Australia

    goolawah Junior Member

    There are so many boat designs out there, some great, some not so great. Why would anyone bother to design another one? My reason is that I just love the process and the learning and discovery that comes out of it. If you just want the building experience I would definitely recommend using an established reputable design. If you also seek the design experience it seems to make sense to design something that fits into a unique niche. The niche our Curlew nesting dinghy fitted into was very unique (i.e. the inside of our caravan). The niche for this Little Red Hen project is a bunch of guys with a limited budget, a random set of skills and experience, very little long-term available space, and a strong interest in building a traditional craft.

    Having learned a bit about the relationship bewteen bilge turn rdius, plank width, and plank thickness, we are ready to apply our learning and progress a little further. The next step was to carefully dimension all the component parts so that members of the group could choose something within their capabilities. So, starting with the 'core' components I have drawn up the Transom, Stern Knee, Hog, Skeg, Keel, Mast Step, Breast Hook and Moulds. In the fond hope of finding a grown crook for the stem I have just drawn a profile template that I can slap against any promising piece of wood that might be on offer, to see if it fits. I'll take this (and a chainsaw) with me next time we go to our block in the bush, but even though there are many big trees, I doubt if I could find one big enough and suitable for the stem. We live in hope.

    Just to show that it can be done, my wife put up her hand to make the Breast Hook. And very nicely done too. Below are and overall drawing of the 'backbone' examples of some of the detailed drawings handed out to the team including the stem profile.
     

    Attached Files:

    1 person likes this.
  13. Landlubber
    Joined: Jun 2007
    Posts: 2,640
    Likes: 124, Points: 0, Legacy Rep: 1802
    Location: Brisbane

    Landlubber Senior Member

    Goolawah,

    The wood in natural curves that you require mate we used to get in the Mallee in SA.

    You can dig out some nice old stumps (try a bulldozer if possible) and get them from the roots, they are not from branches.

    Just in case you did not know.
     
  14. waikikin
    Joined: Jan 2006
    Posts: 2,381
    Likes: 150, Points: 73, Legacy Rep: 871
    Location: Australia

    waikikin Senior Member

    Hi Goolawah, heres a couple a pics of a 12' clinker, she's planked in Honduras mahogany with silver ash timbers, she got Teatree knees etc, an old bloke in Hawkes Nest in the Myall lakes area got them for us, the boss posted up the templates in cardboard + thickness required & he'd grub out the stumps etc & rough cut em, coat in wax & leave them buried till you come to pick them up. Looks like a cool project you've got going. All the best from Jeff.
     

    Attached Files:


  15. goolawah
    Joined: Oct 2005
    Posts: 96
    Likes: 5, Points: 0, Legacy Rep: 67
    Location: Brisbane, Australia

    goolawah Junior Member

    Yes, me old Landlubber mate. I was aware that the stem timber comes from roots, not branches. Last time I was down in the bush (but without a chainsaw) I had a bit of a scout around for a suitable recently fallen tree but no luck. It can't be just any old thing. Has to be workable for starters.

    I have heard that melaleuca (I guess that's Tea Tree) has been used and there are a couple of abandoned melaleuca plantations on neighbouring properties, but the trees are nowhere near big enough. If I found a tree big enough I probably wouldn't be able to access a bulldozer capable of dong the job. If I can find a fallen tree that the termites haven't yet attacked, that would be great, but probably just dreaming.

    Hey Waikikin, is your old bloke in Hawkes Nest still around? Nice Pics of 12 ft dinghy. I hope we'll end up with something like it. Can you recall how thick the planks were?

    Cheers,
     
Loading...
Similar Threads
  1. StandedInMx
    Replies:
    14
    Views:
    1,882
  2. missinginaction
    Replies:
    6
    Views:
    1,376
  3. mark123
    Replies:
    6
    Views:
    7,256
  4. txriverrat
    Replies:
    16
    Views:
    4,225
  5. boat fan
    Replies:
    0
    Views:
    1,332
  6. cameron.d.mm
    Replies:
    33
    Views:
    28,966
  7. JamesW
    Replies:
    1
    Views:
    1,734
  8. handyman
    Replies:
    7
    Views:
    1,587
  9. Joe Conway
    Replies:
    14
    Views:
    664
  10. messabout
    Replies:
    7
    Views:
    721
Forum posts represent the experience, opinion, and view of individual users. Boat Design Net does not necessarily endorse nor share the view of each individual post.
When making potentially dangerous or financial decisions, always employ and consult appropriate professionals. Your circumstances or experience may be different.