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Thread: Atkin's sailing dinghy Nymph

  1. #1
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    Default Atkin's sailing dinghy Nymph

    Hello,
    It's been awhile since I've been on here and I have a question. A few years ago I purchased from Pat Atkin the Small Boat Book in order to build the 10-foot sailing dinghy Nymph. I'm just getting to it now and have started a quick lofting on rosin paper just to get my bearings and to make sure I understand the plans, I'll do a more accurate lofting when I'm ready to build. Anyway, there are 4 stations between the stem and stern. I started with the L.W.L and layed out the 4 stations for the forms which are 24" apart. I lofted the stem according to all the measurements and all was going well until I started to draw the sheer, from a point of 16" from L.W.L at the stem, 15" at station #1, 11" at station #2, 10" at #3. When I lay a batten on the points it makes a nice curve from the stem to stations #2 and #3, BUT, station #1 falls at 13", not 15". There is no way to make a nice sheer curve from 16" to 15" then a drop to 11" and on to 10" etc. There are a few places on the plans in the book that I needed to use a magnifying glass to make sure I was reading them right and his 5's look kind of like "S's" sometimes. Could 15" that is written be a mistake? I emailed Pat Atkin and asked her this question hoping she can verify the measurement, although I'm not sure whether she is that involved in the business to know the answer. I was hoping someone here may have built this boat and can verify the measurement for me and or give my any other advise about the plans. There are a number of measurements that are not on the plans but I have found that once I started lofting a lot of those measurements revealed themselves and it's working out well, except for L.W.L to top of station #1 of the forms. Thanks for listening.

  2. #2
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    Default Re: Atkin's sailing dinghy Nymph

    Does the embedded image illustrate what you've done? I don't see where you include the numbers for station 4 or for the transom. You should hopefully get a fair curve. It's worth keeping in mind the line is a two dimensional representation of a three dimensional object - the sheer comes "out" of the page as you go from bow to amidships and back "into" the paper as it returns to the transom.

    This is a backwards way of doing things, but since the numbers aren't clear and you have a profile view available, scale from the drawing and plug the numbers in, including station 4 and the transom, and try to draw the sheer. Maybe the numbers aren't properly transcribed in the offset table or by you.

    Also, what are you using for a batten? Stiff enough, too stiff? Additionally, you need to run past the points with the batten. If you are running out of batten and are only spanning the distance from the stem to station 3, you need to marry the curve drawn with one that goes from station 2 to the transom. That's a small enough boat you should be able to find a piece of PVC pipe at a home improvement store that will let you loft the lines in one pass. Good luck!
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  3. #3
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    Default Re: Atkin's sailing dinghy Nymph

    Wiley Baggins,Yes the image you posted is pretty much the same as the Nymph. Station #4 is 10 5/16". As I said in my post I was just doing a quick lofting just to get an idea as to what I was doing. The piece of rosin paper I had was the end of the role and was only about 7' long. I lofted the transom, stn 4 and stn 3 on one side and the stem and stn 1, 2 and 3 on the other. The aft end lofting went well and the sheer and the line of the bottom of bottom plank worked nicely, looks good. I figured I'd do the other half on the other side, everything made sense and lined up with numbers on plan, there is no offset table. I'm using a decent piece of thin straight grain fir for batten about 8' long. This was going to be just a test to see if my perception of how to do this was going to work, and it did until stn. 1 measurement of 15". I intend to make a nice long batten when I loft the whole boat. Maybe the bend will line up with the measurement points that make the sheer when I loft the whole 10' length and my batten is better. I would think though that even though I'm bending a curve along 6', even with a not too perfect batten, the sheer line would come somewhat close to all the point of measure. I've had to bend curves building cabinets and architectual woodwork before and to me the bend from 16" to 15" then from 15" to 11" (a 4" difference),and then continue that curve to 10" just doesn't make sense. The 13" I end up with at stn.#1 makes sense and looks right. I guess I should loft the whole boat and see what happens, I won't be surprised if I'm doing something wrong or missing something. I will do as you suggest and see if I've got all the numbers right. Thanks for the input.
    ,

  4. #4
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    Default Re: Atkin's sailing dinghy Nymph

    Wiley Baggins, I just noticed something else about the Atkin plans. When talking about the stern he says you must deduct the thickness of the planking from the measurements given on the plan, so 1/2" from each side. He doesn't mention doing that regarding the measurements for the molds but, I noticed the station mold at the beam, #3, is given as 22" ( they only show half the mold) which would mean the boat is 44" inside the planking. The dimensions given for the boat are 10' long by 3' 8" wide, which is 44". If I made the mold according to measurements on plan the boat would be 45" wide. I'm thinking I need to deduct plank thickness from all the station molds listed. I'm trying to find someone who may have built this boat or another small Atkin design to see what they have to say about all the vague instructions, I guess an experienced boat builder would just know what to do.

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    Default Re: Atkin's sailing dinghy Nymph

    It's pretty typical, in fact I would say the norm, to have to deduct plank thickness. I imagine it's a function of naval architects/boat designers drawing to the outside of the planking to run their calculations and the expectation that builders, particularly professionals, are easily capable of managing the deduction of planking thickness on the lofting. I'm quite confident you can as well. It's a trivial exercise with a hard chine design - just draw parallel lines. The image below illustrates a gauge to help with round bilged designs/curves. I didn't come up with this, but saw it illustrated here on the forum, "WoodenBoat" or another magazine, etc. Your pencil or lofting pen pokes through the hole in the disk and you run the outside of the disk along the inside edge of your lofted line. I might suggest lofting the Nymph on paper at half size. You'll get the same amount of lofting practice and get all the lines in front of you at one time. You can build a basic table of offsets from the scale drawing you have and expand it to half size on one side of the paper you have.
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    Last edited by Wiley Baggins; 07-10-2021 at 07:47 PM.

  6. #6
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    Default Re: Atkin's sailing dinghy Nymph

    WB, that's a clever little gauge, I'll have to remember it, could be used for lot's of different applications. I've kind of come to the same conclusion regarding the size of forms. Would deduction include not only side plank thickness but the thickness of bottom too? He has measurements from L.W.L to top of forms, which stay as they are, and to bottom, should I deduct from that measurement for bottom planking?
    I don't think I'm going to loft at half size, going to do full, I think it will help me to understand and figure out the grey areas better, actually seeing how big things are etc. I'm sure there will be things that don't make sense but I think by lofting I'll be able to figure them out. Not that I want to but I don't think the boat will be a total disaster if I'm off a whisker here or there, as long as I'm off the same amount on both sides of the boat! I would like your opinion on my using white pine for bottom planking, 1x4's. I've asked other people about it and they all have said it won't be a problem, just not as rot resistant. This boat will not live in the water and it will have a well cared for life so I'm not concerned about rot resistance. I know White Pine has been used for years on some pretty large boats. I'm going to be pitching pennies to build so want to save as much as I can on material. I am wondering if I should even bother caulking (cotton wicking) and putty as Atkin suggests prior to applying 1/2"x4" keel. I'm thinking the boat will swell up pretty tight without it. I can also dump water in the day before we take it out again, which may be once a week or two to three times a month from May to Nov. I also contemplated using quarter sawn 1/2"x4" Fir square edge decking, a lot more money but strong. Not sure it will swell up as tight as W Pine being quarter sawn.
    Last edited by Saltwater; 07-10-2021 at 03:49 PM.

  7. #7
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    Default Re: Atkin's sailing dinghy Nymph

    I recommended half size just for the lofting practice. Full size is definitely the way to go for building. I’ll defer to others for your wood question. Best choices lumber wise is very much a local thing and there are plenty of folks on the board that can do a better job advising you. I will say I’ve had good luck buying from a small local mill rather than a lumber yard. Probably even better (more economical) if you can do your own resawing for thickness. Depending on your timetable and the space you have, you could sticker up the lumber and air dry it yourself.

  8. #8
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    Default Re: Atkin's sailing dinghy Nymph

    Thanks for the help. There is a saw mill not too far from me that I've been too before in regards to wood for a boat. They will also look out for certain kinds of wood I may want to use although that could take a while to get. I have quite a bit of odds and ends left over from 43 yrs. as a carpenter/cabinetmaker and from taking care of a wooden cat boat that we used to have. I may only need to buy planking, which is four planks and the bottom planks. Can't do resawing but the mill has an great ancient surface planer and they will dimension for me if I need it.

  9. #9
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    Default Re: Atkin's sailing dinghy Nymph

    Quote Originally Posted by Saltwater View Post
    I've kind of come to the same conclusion regarding the size of forms. Would deduction include not only side plank thickness but the thickness of bottom too? He has measurements from L.W.L to top of forms, which stay as they are, and to bottom, should I deduct from that measurement for bottom planking?
    Sorry I missed this question in my earlier reply. Unless noted otherwise, I think it's safe to assume the deduction applies to all planking, side and bottom. It's more intuitive with a round bilged hull as "planking is planking." A chine and a flat bottom could be read to imply a distinction that is most likely not there. There may be a detail for the transom indicating it's drawn to the finished size and not treated as a station mold requiring deducting the thickness of the planking. Happy building!

  10. #10
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    Default Re: Atkin's sailing dinghy Nymph

    Awesome, really good to know. Thanks again for the help.

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