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Thread: First Build - Herreshoff Pram

  1. #1
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    Default First Build - Herreshoff Pram

    Hi all

    I've been lurking on the site for a while, but recently started my first build and thought I'd better post some pictures to share and document the process! There's a wealth of knowledge available on here and I've learnt a lot already, but I'm looking forward to the build and learning some more tips and tricks along the way.

    I'll be attempting a Herreshoff pram, from John Gardner's 'Building Classic Small Craft'.

    I decided instead of lofting the traditional way, that I'd give it a go digitally. Here's a couple of screen-grabs of the SolidWorks model;









    Last edited by thompy.mark; 07-06-2017 at 06:18 AM. Reason: Replace photobucket with google photos

  2. #2
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    Default Re: First Build - Herreshoff Pram

    I liked the idea of the ladder frame that Gardner talks about, but thought I'd add a couple of temporary stringers at say 30deg and 60deg off the centreline. These should help hold the moulds rigid while planking and can be removed progressively as the planking progresses up toward the sheer, allowing a bit more room to work, and for the intermediate ribs between the moulds to be put in place. They're designed to notch into the moulds, so the moulds sit proud by a couple of mm. I've applied a similar approach to the 'ladder', although these are a bit deeper to add some stiffness, and have bevelled ends to match the inside face of the bow and stern transoms. Something along the lines of this;









    One of the benefits of lofting digitally was that I was able to get these bits cut by a local CNC business. Here's the moulds as I received them;










    Unfortunately, I didn't know exactly how thick the ply was going to be, so I had the slots cut a bit narrow. Here widening the slots to the appropriate width, plus cutting the slot for the keel batten (which I forgot to add on the file sent for CNC, doh!);







    I couldn't resist standing them up!


    Last edited by thompy.mark; 07-03-2017 at 04:22 AM. Reason: Replace photobucket with google photos

  3. #3
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    Default Re: First Build - Herreshoff Pram

    I actually had the stringers cut in a separate batch, here they are when the arrived back from CNC a couple of weeks after I had finished the moulds;







    I had patterns cut for the bow knee and stern post at the same time (sitting on top of the deeper stringers in the above pic).


    The slots on these needed squaring up with the chisel as well, but was much quicker than the moulds.


    The stringers needed scarphing to make up the required length. I set up a temporary router jig on the bench, and made good use of the alignment holes I'd had cut in each piece with the CNC;










    I was pretty happy with the my first ever scarphing attempt! Lots of measuring as I went definitely helped;







    All ready for epoxy;







    ...and gluing up;


    Last edited by thompy.mark; 07-03-2017 at 04:27 AM. Reason: Replace photobucket with google photos

  4. #4
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    Default Re: First Build - Herreshoff Pram

    After they were dry, I was finally able to put the building frame together and get a proper look at the shape;













    It all slotted together perfectly, was super happy. I'll need to add some cleats to firmly fix the two ladders together, and the moulds to the ladder. I'll do this once I get it up off the floor and levelled at a suitable height.


    Being in New Zealand it can be difficult (expensive!) to obtain some of the usual boatbuilding timbers that are found in North America and Europe, so I thought I'd try to use some more readily available species.


    Transoms, bow knee, stern post, and a select few other bits (as yet undecided what) will be Australian Blackwood. Keel strip and skeg will be White Oak as per plan. Planking will be Macrocarpa/Monterey Cypress. I'm hoping this should turn out an ok colour scheme.


    I picked up the blackwood and oak first. Again, I set up a temporary router jig on the bench to flatten one side, and then rough thickness;





    More catch-up progress/pics tomorrow. Thanks for reading!
    Last edited by thompy.mark; 07-03-2017 at 04:32 AM. Reason: Replace photobucket with google photos

  5. #5
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    Default Re: First Build - Herreshoff Pram

    Almost looks like you're setting up to build them production line style with that jig. Nice work. Hope she turns out as you envision.
    If one advances confidently in the direction of his dreams, and endeavors to live the life which he has imagined, he will meet with a success unexpected in common hours.
    -Henry David Thoreau-

  6. #6
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    Default Re: First Build - Herreshoff Pram

    Very interesting. By using the computer and having the molds cut, you got a custom kit. Was it expensive?
    Is your build traditional plank on frame? Lapstrake or carvel?
    Thanks for sharing.

  7. #7
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    Default Re: First Build - Herreshoff Pram

    Looks great so far, Mark. I'll be watching with interest.


    Steven

  8. #8
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    Default Re: First Build - Herreshoff Pram

    I think one of the advantages of that style of pram is how easily they are planked (planks are close to straight which lie and fasten easily). Your jig is quite a work of art and design. You have clearly enjoyed working it out but I'm thinking if you'd gone with Gardner's ladder frame and molds you would have finished the planking already. It is good for a production jig as mentioned above. You should consider offering it for sale or donating it to a school after you've finished the boat. Good luck!
    "It ain't what you don't know that gets you into trouble. It's what you know for sure that just ain't so."

    -Mark Twain

  9. #9
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    Default Re: First Build - Herreshoff Pram

    Quote Originally Posted by johngsandusky View Post
    Very interesting. By using the computer and having the molds cut, you got a custom kit. Was it expensive?
    Is your build traditional plank on frame? Lapstrake or carvel?
    Thanks for sharing.
    It was actually quite reasonable, for the amount of time it saved me. Price for the CNC work was NZD$165. They also supplied the ply, at about the same price I would have bought it elsewhere. Plans call for 1/4" lapstrake planking. Should hopefully turn out something like this, except with a reversed colour scheme (dark transoms, light planking);




    Quote Originally Posted by rbgarr View Post
    I think one of the advantages of that style of pram is how easily they are planked (planks are close to straight which lie and fasten easily). Your jig is quite a work of art and design. You have clearly enjoyed working it out but I'm thinking if you'd gone with Gardner's ladder frame and molds you would have finished the planking already. It is good for a production jig as mentioned above. You should consider offering it for sale or donating it to a school after you've finished the boat. Good luck!
    There have definitely been thoughts of turning out more than one (if I enjoy the process!), so the frame was designed with that in mind. I'd definitely make sure it went to a good home as you suggest once I'm finished with it.

    If anyone is interested in the .dwg files to have a set CNC cut for themselves, please get in touch. I'd be happy to make the files available.

  10. #10
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    Default Re: First Build - Herreshoff Pram

    My router had been dropped before I bought it, hence the pronounced ridges in the previous pic. I later shimmed the base, and got a much better surface quality.


    Here's the blackwood after a bit of planing to remove the router marks;







    I was curious to see how the blackwood would come up with some sanding and oil. Seeing this appear got me quite excited to hurry up with the transoms, it has some lovely grain!







    I was able to put the rest of the blackwood boards through my father-in-law's thicknesser and get them down to close to final thickness. I was a bit precious about my nicely planed side, and didn't skip plane this board like the rest. It's consequently got about a 1/8" bow over a 2 1/2' length. Here's trying to straighten it after wetting the concave side with some warm water;







    It took a bit of the bow out, but is definitely still there. Any tips/tricks for straightening it out? I don't have enough material to plane it flat again, and am hoping to avoid buying some more.


    Last night I planed the bow knee down to final thickness, flush-trimmed to size, and gave it a sand. Here's the finished bow knee;







    Very pleased with my efforts, I took it inside to show the other half. At which point I happened to glance at the open book on the table, and my heart sank when I realised I had finished it to 3/4" thick, while the plans called for 7/8". Next to the stern post at 7/8";







    I'm hoping it will be ok, on the basis that I'm also making the transoms 3/4" thick blackwood, which has a higher modulus of rupture and elastic modulus than the mahogany on the plans. At least it wasn't the stern post, as that pokes through the keel batten and mortises into the 7/8" thick skeg. Lesson learnt-keep the plans on hand, and keep checking them!


    Over the weekend I hope to finish shaping the stern post, and get the inner (setup) keel batten screwed into the moulds.
    Last edited by thompy.mark; 07-03-2017 at 04:36 AM. Reason: Replace photobucket with google photos

  11. #11
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    Default Re: First Build - Herreshoff Pram

    Cheers from Florida. Looks great and I love seeing the blend of Herreshoff, Gardner and new tech.

    As for the bow knee, is that your little blue "Moaning chair" in the background? You do have one handy, right? It is also used as a place for the usual visitors to hang out and cheer.

    The moaning chair is defined by Chapelle as "a comfortable seat from which the boat can be easily seen and in which the builder can sit, smoke, chew, drink or swear as the moment demands. Here he should rest often and think about his next job. The plans should be at hand and here he can lay out his work. By doing so he will often be able to see mistakes before they are serious and avoid the curse of the amateur boatbuilder: starting a job before what has to be done to get it right." (Chapelle, Boatbuilding 1941).

    I cut not one not two but 3 transom frames before I got the right shape for our Penobscot




    kb
    Last edited by signalcharlie; 05-19-2017 at 07:00 AM.

  12. #12
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    Default Re: First Build - Herreshoff Pram

    Thanks for the sage advice

    Looks like I should make some inroads past the first couple of pages...!




    Cheers
    Mark
    Last edited by thompy.mark; 07-03-2017 at 04:37 AM. Reason: Replace photobucket with google photos

  13. #13
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    Default Re: First Build - Herreshoff Pram

    Neat work on the jig. Reminds me of a mock-up light aircraft "canopy" I built once to check cockpit ergonomics and head clearance.
    I should have kept it and built a very nicely curved strip-plank cuddy or cabin-top!

  14. #14
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    Default Re: First Build - Herreshoff Pram

    UPDATE TIME!

    Since I left off last time, I marked out the centreline of each of the moulds;




    And then shaped half of the mould to suit the form of the hull and avoid creasing the inside of the planking. The stringers were quite helpful in this regard, as they gave me a guide to the correct bevel;




    I then set the form up on sawhorses;




    And fixed all the members together with angle brackets. This should be easy to undo again when taking the form apart after planking, and also assist in putting back together for the next one off the 'production line';




    The oak I have for the keel batten. It's flatsawn, but is quite dry (had been sitting indoors at the timber yard for a few years). It was one of the few pieces they had that were long enough for me to get out the entire length of the dinghy without a scarf joint;




    Temporary set-up batten screwed in place with 2x #10 screws per mould. The setup batten only extends to station 7 to make way for the bow knee. Note the extra cutout in station 8 for the knee, at the bottom of the picture;

    Last edited by thompy.mark; 07-03-2017 at 05:00 AM. Reason: Fixed rogue spelling

  15. #15
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    Default Re: First Build - Herreshoff Pram

    Then with a judiciously applied jigsaw, cutouts were made to the temporary keel batten between the moulds. This should allow me to fasten the garboard to the permanent keel batten, without the temporary batten interfering too much. I'd like to try and keep some of the moulds in place while placing the 2x ribs between each mould, however that would require either removing or destroying the temporary batten. Not quite sure how I'll tackle this one yet, although if it has to be sacrificed to the boat-building gods then so be it. A small price to pay for a straight hull!




    This marks a milestone for me, as it completes the temporary construction. Everything that goes on the boat from now on will be permanent! Slightly intimidating, but looking forward to the challenge.

    Next up are the transoms. I need to get hold of some large clamps to glue up the panels. I've also ordered a low-angle spokeshave kit from Veritas, 'cos everyone likes new tools! It should also help with bevelling the transoms to accept the planking, especially considering that I'll be working mostly with end-grain.

    Thanks again for reading! Questions/comments/advice welcome

  16. #16
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    Default Re: First Build - Herreshoff Pram

    The building frame is pretty impressive. Looking forward to the next steps.

  17. #17
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    Default Re: First Build - Herreshoff Pram

    Finastkind.

  18. #18
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    Default Re: First Build - Herreshoff Pram

    Your are building one of my favorite yacht tenders! I know that LFH would have approved of your approach and wood working skills!
    Jay

  19. #19
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    Default Re: First Build - Herreshoff Pram

    I love that design. I built one in cedar strip composite, a bit shorter.



    Your mold is excellent.

  20. #20
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    Default Re: First Build - Herreshoff Pram

    Looks awesome. That blackwood is rather fine looking too.

  21. #21
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    Default Re: First Build - Herreshoff Pram

    A good approach to the build.Did you consider using the CNC router to cut the bevels?Its not a huge amount more work.

  22. #22
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    Default Re: First Build - Herreshoff Pram

    Quote Originally Posted by timo4352 View Post
    The building frame is pretty impressive. Looking forward to the next steps.
    Thanks, me too!


    Quote Originally Posted by Ian McColgin View Post
    Finastkind.
    Thanks Ian.


    Quote Originally Posted by Jay Greer View Post
    Your are building one of my favorite yacht tenders! I know that LFH would have approved of your approach and wood working skills!
    Jay
    Thanks Jay, very kind of you to say.


    Quote Originally Posted by JimConlin View Post
    I love that design. I built one in cedar strip composite, a bit shorter.



    Your mold is excellent.
    Thanks Jim. I've had pictures of your boat on file for inspiration for a while-I hope you enjoy using it as much as I like looking at it!


    Quote Originally Posted by Hreoaj View Post
    Looks awesome. That blackwood is rather fine looking too.
    Thanks. I'm quite looking forward to seeing the transoms take shape!


    Quote Originally Posted by John Meachen View Post
    A good approach to the build.Did you consider using the CNC router to cut the bevels?Its not a huge amount more work.
    Thanks John. I considered getting the bevels done on the CNC, but it would have cost a bit more. The machine is priced on run-time, so the straight cut that I got was not too costly-each piece only took a few passes. To cut the bevels in steps would have blown the cost out more than I was willing to pay, plus it was nice to do a bit of work myself in making the moulds

  23. #23
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    Default Re: First Build - Herreshoff Pram

    For those who are watching-does anyone have the recommended lap width for 1/4" clinker planking for this boat? I seem to recall reading 3/4" somewhere, but can't seem to find it now that I need it (I'm having a crack at lining planks)

    Thanks in advance!

  24. #24
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    Default Re: First Build - Herreshoff Pram

    FWIW the lap is 3/4 inch on our Penobscot 14 with 1/4 inch planking.

  25. #25
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    Default Re: First Build - Herreshoff Pram

    Thanks. Will try to get some time in the shed this weekend and see how it looks, as this will be the telling factor!

    I drew up a a couple of cross-sections last night based on the tentative plank widths given by Gardner, but these seemed to require a larger lap width to get everything fitting between skeg and sheer. Makes for a stronger boat I guess, but would add some weight. More investigation required on my part I think...

  26. #26
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    Default Re: First Build - Herreshoff Pram

    Lining off complete!!

    So in the vein of trying to merge traditional skills with a bit of modern tech, I took the tentative plank widths given by Gardner for stations 3, 8, & stern transom, and then plugged these into a spreadsheet to calculate how the plank widths changed along the boat, and along each mould. After a bit of measuring, this was my first attempt;




    Not too bad, but definitely a few wobbles here and there. Some issues at the stern, plus at the turn of the bilge. My measuring technique was to blame here, as I measured both from the sheer and skeg to meet in the middle. It ended up with plank widths at the bilge a bit narrower than those either side. The plank widths also didn't change width in a nice smooth manner.

    So, back to the computer! I graphed the width of each plank along the boat as well as the width of each successive plank across each mould. There were definitely a few humps and hollows but a tweak of a milllimetre here and there yielded some fair curves. From here I printed myself a reference table, for stations 0 to 9 (0 being stern transom, to 9 as the bow transom), and planks A (garboard) to J (sheer-strake).




    To eliminate cumulative errors measuring along the mould, I took a sewing tape and tacked the end to the mould in line with the sheer. From there it was a simple matter of reading off the cumulative distance to the bottom side of each plank (second table of numbers in the above pic).

    And, voila!








    Super happy with how it came out, and that my method worked! One of the battens is missing a couple of tacks up forward, as it covers one of the cutouts for the stringer (I took the stringers off that side so they didn't mess with my eyes). I'll keep looking at if over the next few days to see if anything sticks out but for now am on cloud 9

  27. #27
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    Default Re: First Build - Herreshoff Pram

    It looks great.

  28. #28
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    Default Re: First Build - Herreshoff Pram

    "It ain't what you don't know that gets you into trouble. It's what you know for sure that just ain't so."

    -Mark Twain

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