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Thread: Lining off the Herreshoff dinghy - possible lap issues?

  1. #1
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    Default Lining off the Herreshoff dinghy - possible lap issues?

    First time builder here. Building the Herreshoff Dinghy, 11 1/2 foot, lapstrake.

    I'm currently working on lining off the boat. To do this I used the plank width ratios and diminishing method specified in Barry Thomas' "Building the Herreshoff Dinghy" (basically the same diminishing method in Rossel's "Building Small Boats").

    After I laid out the lines, I checked the laps with some fids. At station 5 (and only station 5), I get a single plank that doesn't lie properly along the curve. In order for the bottom edge to lap over the previous plank correctly, the top edge rises off the mold maybe 1/16 of an inch. I've circled the offending fid in the photos below (for scale, planking is 1/4 inch thick).

    lap_error2.jpg
    lap_error.jpg

    How big of an issue is this? Will this pull together okay when I eventually rivet the planking to the frames?

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    Default Re: Lining off the Herreshoff dinghy - possible lap issues?

    With lapstrake it is necessary to ensure a good fit between the planks with each lap joint.
    The mold will be tossed when the planks are fastened so why worry.
    Looks like you have done a great job to date.

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    Default Re: Lining off the Herreshoff dinghy - possible lap issues?

    It doesn't matter in the slightest. All that matters is that the planks lap nicely and run fair.

    Whether the planks run a little clear of the moulds or not depends largely on the number of planks and the curvature of the mould – the fewer the number of planks, the more they will depart slightly from the moulds.

    In the days when lots of lapstrake/clinker dinghies were built, most yards had a few midship moulds for various size dinghies and they were built on the transom, a midship mould and the stem, hog/keel. Sometimes there would be a couple of intermediate moulds on a larger dinghy. These were general purpose boats so it didn't matter if no two were quite alike. It's different if you are building to class of course.


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    Default Re: Lining off the Herreshoff dinghy - possible lap issues?

    What George said. Some yards saved money by using a half mould, swinging on a vertical shore so that it could be used on either side to check the shape, or swung out of the way for clenching up the laps. It fitted where it touched.
    It really is quite difficult to build an ugly wooden boat.

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    Default Re: Lining off the Herreshoff dinghy - possible lap issues?

    You might check the measurement on the mold, it appears to be the slightest, tiniest, miniscule proud at that turn, maybe the knot forced the saw out a bit or the mold needs a little bevel? A fair curve or wha't pleasing to your eye supersedes what the mold gives up.

    I'm not sure if Thomas suggests it, I'll have to go look at his book later, but will you also be running ribbands (I call them stringers) fore and aft at each plank lap to look for fair curves? We did that per instruction on our Penobscot 14 build, making sure there were no humps or hollows. On the P14 the stringers are part of the boat, they provide a landing for the laps.

    St JACQUES stringers ribbands.jpg

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    Default Re: Lining off the Herreshoff dinghy - possible lap issues?

    I agree,... before FRG,... in the days of wooden boat production what you are looking at wouldn’t have even caught someone’s eye. Here you can see about a 30 foot lapstrake sea skiff being planked up with only three moulds, and the planking is a good couple of inches clear of a mould in one area (and they built about 300 boats over time).
    Attached Images Attached Images

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    Default Re: Lining off the Herreshoff dinghy - possible lap issues?

    Amphicraft PRIM on the molds at HMCo (image credit HMCo)

    PRIM ready for planking.jpg

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    Default Re: Lining off the Herreshoff dinghy - possible lap issues?

    Awesome, glad to hear all this. Thanks for the feedback!

    signalcharlie - yes I will be running battens along the planking lines to check for fair curves. After that checks out I'll cut notches in the molds and run the ribbands. My plan is to run one edge of the ribbands along the planking lines, opposite the side the planking laps will fall on, so that rivets driven through the laps avoid the ribbands.

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    Default Re: Lining off the Herreshoff dinghy - possible lap issues?

    Quote Originally Posted by ptscho View Post
    Awesome, glad to hear all this. Thanks for the feedback!

    signalcharlie - yes I will be running battens along the planking lines to check for fair curves. After that checks out I'll cut notches in the molds and run the ribbands. My plan is to run one edge of the ribbands along the planking lines, opposite the side the planking laps will fall on, so that rivets driven through the laps avoid the ribbands.
    You must have too much time on your hands.
    Just line off the moulds, and spile the planks to your lining off. No need to waste any more time or materials.
    It really is quite difficult to build an ugly wooden boat.

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    Default Re: Lining off the Herreshoff dinghy - possible lap issues?

    Quote Originally Posted by Peerie Maa View Post
    You must have too much time on your hands.
    Just line off the moulds, and spile the planks to your lining off. No need to waste any more time or materials.
    Yep!! A man and a boy would build a 10' dinghy in a week or the guv'nor (my father) would be wanting to know what the problem was

    Sadly the last boatbuilder from that era, Dennis Hayles, died a year or so ago now he started at the yard when he was 14 years of age served in the Royal Navy in WWII returned to the yard afterwards and carried on there until 1990. A wonderful man Dennis always told you how it was no nonsense regardless. He was our dinghy specialist. Though he also built, pretty much single-handed, with a boy to help, Deben 4-tonners, Holman 26's and any other boats that could be built in the 'small shop'

    Cheers -- George
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    Default Re: Lining off the Herreshoff dinghy - possible lap issues?

    Do the plans specify the number of planks? The lowest strakes appear a bit wide for the 1/4" material. Adding one more plank would probably solve your issue and head off other problems due to wide garboards.

    Also, I'm almost always in the crowd saying not to be too precious, just get on with it, but this one would actually bother me. The bent frame will not bear on the lap, its rivet will be exposed slightly between the frame and plank. The plank will have a tendency to split at the fulcrum of where the frame does touch the plank. It isn't the end of the world, and would be fine on a heavier boat, but the columbia dinghy deserves an extra measure of effort in my opinion.

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    Default Re: Lining off the Herreshoff dinghy - possible lap issues?

    Quote Originally Posted by J.Madison View Post
    Do the plans specify the number of planks? The lowest strakes appear a bit wide for the 1/4" material. Adding one more plank would probably solve your issue and head off other problems due to wide garboards.

    Also, I'm almost always in the crowd saying not to be too precious, just get on with it, but this one would actually bother me. The bent frame will not bear on the lap, its rivet will be exposed slightly between the frame and plank. The plank will have a tendency to split at the fulcrum of where the frame does touch the plank. It isn't the end of the world, and would be fine on a heavier boat, but the columbia dinghy deserves an extra measure of effort in my opinion.
    I think that the steamed frame when properly installed will fit there OK. It is not as if the shape of the mould's curve is that far out.
    It really is quite difficult to build an ugly wooden boat.

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    Default Re: Lining off the Herreshoff dinghy - possible lap issues?

    What everyone else said. However if the plank edge vibrates or bounces a bit peening your rivet you can just slip a thin wedge in to make a solid bearing.

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    Default Re: Lining off the Herreshoff dinghy - possible lap issues?

    Quote Originally Posted by J.Madison View Post
    Do the plans specify the number of planks? The lowest strakes appear a bit wide for the 1/4" material. Adding one more plank would probably solve your issue and head off other problems due to wide garboards.

    Also, I'm almost always in the crowd saying not to be too precious, just get on with it, but this one would actually bother me. The bent frame will not bear on the lap, its rivet will be exposed slightly between the frame and plank. The plank will have a tendency to split at the fulcrum of where the frame does touch the plank. It isn't the end of the world, and would be fine on a heavier boat, but the columbia dinghy deserves an extra measure of effort in my opinion.
    Yes, the plans call for 10 planks. The floors should give the garboard something to bear on along its full width right? Although that doesn't do anything for the broadstrakes if those are too wide.

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    Default Re: Lining off the Herreshoff dinghy - possible lap issues?

    Quote Originally Posted by Peerie Maa View Post
    I think that the steamed frame when properly installed will fit there OK. It is not as if the shape of the mould's curve is that far out.
    Is this assuming planking first, the flipping the boat over and steaming the frames in right side up?

    My plan was to run ribbands on the molds and steam frames over them, then plank. For a first timer like me that seems like the easier/less error prone route, but I'll take any advice on the best path forward I can get

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    Default Re: Lining off the Herreshoff dinghy - possible lap issues?

    Quote Originally Posted by Peerie Maa View Post
    You must have too much time on your hands.
    Just line off the moulds, and spile the planks to your lining off. No need to waste any more time or materials.
    Haha, I wish. Just a lack of experience and nerves about messing something up, especially a structural component.

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    Default Re: Lining off the Herreshoff dinghy - possible lap issues?

    Quote Originally Posted by ptscho View Post
    Is this assuming planking first, the flipping the boat over and steaming the frames in right side up?

    My plan was to run ribbands on the molds and steam frames over them, then plank. For a first timer like me that seems like the easier/less error prone route, but I'll take any advice on the best path forward I can get

    Proceeding as you plan will increase the offsets by the thickness of the ribbands plus the thickness of the ribs. And that's fine if the molds have been sized accordingly. But if they have been, why would you do a trial layout of planking as you show in the OP photo? Perhaps I've misunderstood your intention.

    Jeff

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    Default Re: Lining off the Herreshoff dinghy - possible lap issues?

    Quote Originally Posted by jpatrick View Post
    Proceeding as you plan will increase the offsets by the thickness of the ribbands plus the thickness of the ribs. And that's fine if the molds have been sized accordingly. But if they have been, why would you do a trial layout of planking as you show in the OP photo? Perhaps I've misunderstood your intention.

    Jeff
    The ribbands would be notched into the molds to account for those offsets.

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    Default Re: Lining off the Herreshoff dinghy - possible lap issues?

    Quote Originally Posted by ptscho View Post
    Is this assuming planking first, the flipping the boat over and steaming the frames in right side up?

    My plan was to run ribbands on the molds and steam frames over them, then plank. For a first timer like me that seems like the easier/less error prone route, but I'll take any advice on the best path forward I can get
    How were you planning to fasten the planks to the steamed timbers?
    It would normally be with copper nails either roved or turned. In which case you are going to be flipping a boat where nothing is finally fastened. How will you fasten the timbers to the keel whilst on the building form?

    If you hang the plank without the ribbands you can clench each lap as it is completed with good easy access to work. Then when you flip her for timbering out you will have a more robust structure to work in.
    It really is quite difficult to build an ugly wooden boat.

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    Default Re: Lining off the Herreshoff dinghy - possible lap issues?

    Copper rivets for plank to frames and for lap clenching. Joel White builds the Catspaw by partially driving the copper nails so they don't interfere with the ribbands when flipping the hull. Greg Rossel indicates that well placed ribbands also go some ways towards mitigating nail/ribband interference too. My biggest concern is minimizing my opportunity to make mistakes, even if it's extra work in the end.

    As far as frame to keel fastening, I'm still debating. The Herreshoff used floors so that's what I'm leaning towards, but the Catspaw screws frames to the keel, with a wedge on the frame as support between the frame and the garboard.

    I fear I've generated more questions now than before. There are so many options it's hard to know what the best way.

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    Default Re: Lining off the Herreshoff dinghy - possible lap issues?

    Early on I set up my HV 13 for ribband, bent frame and plank construction. Probably due to the big boat influence of my trade school instructor, who I don't believe was particularly familiar with round bilge lapstrake. I still have those molds. They do facilitate a great majority of the work without extra hands. I need only one helper to initially bend ribs over the ribbands. After that I am entirely buttoning up the boat every fastening, plank by plank, single handed. However, the molds are deducted for the ribbands. I am clench nailing everything. I pull ribbands as I plank up from the keel so I can clench unimpeded.

    That is the only lapstrake hull I have ever set up in such a way. It does allow a great deal of control. However, setting up lapstrake builds since - plank directly over the molds, pull and flip the hull upright, set the ribs.

    The way things look now, it would make a lot of sense for ptscho to simply line off and plank over those molds. The very small gap shown at one plank is not really enough to worry about. You can keep fiddling with the line-off, but if this is your best result, then you are fine.

    I was also surprised to read of only 10 strakes at 1/4" thickness. In fact I thought that was a mistake. But sure enough, I looked at my dog eared pamphlet and there they have 10 strakes at 1/4". The design is somewhat slack bilged. Still surprises me.

    FYI - My first couple of small boats I probably used screws, but now prefer ring shank nails for plank ends and garboard to keel. They will hold in the cross grain or end grain of a transom when properly piloted. Others despise ring shanks and are petrified at the prospect of ever having to remove them.

    Also remember that the Catspaw, as far as I know, was intended for carvel construction - where there is no choice but to set up ribbands.
    Eric

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    Default Re: Lining off the Herreshoff dinghy - possible lap issues?

    Quote Originally Posted by ptscho View Post
    Haha, I wish. Just a lack of experience and nerves about messing something up, especially a structural component.
    Trust your eye, if the lap runs look good and fair go with it. I did that on my build, first time builder and the result is fine. Not the ideal photo but an indication. Trust your eye.
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    Default Re: Lining off the Herreshoff dinghy - possible lap issues?

    Quote Originally Posted by ptscho View Post
    Copper rivets for plank to frames and for lap clenching. Joel White builds the Catspaw by partially driving the copper nails so they don't interfere with the ribbands when flipping the hull. Greg Rossel indicates that well placed ribbands also go some ways towards mitigating nail/ribband interference too. My biggest concern is minimizing my opportunity to make mistakes, even if it's extra work in the end.

    As far as frame to keel fastening, I'm still debating. The Herreshoff used floors so that's what I'm leaning towards, but the Catspaw screws frames to the keel, with a wedge on the frame as support between the frame and the garboard.

    I fear I've generated more questions now than before. There are so many options it's hard to know what the best way.
    My point was how are you going to get access under there to drive the fastening into the keel.
    It really is quite difficult to build an ugly wooden boat.

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