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Thread: Mold Fairing Technique

  1. #1
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    Default Mold Fairing Technique

    Anyone know of or have a good technique for fairing molds? In my case they are 2x10 stock so 1 1/2" that needs to be faired (molds spaced at frame locations 12" apart.) Do you stick to fairing along plank seams or water lines or will any reasonable point from one frame to the next produce the right bevel? It seems it is always glossed over without many of the particulars of how it's done. I understand the end goal I am just not sure how to get there.

  2. #2
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    Default Re: Mold Fairing Technique

    Are you going to apply ribbands to the molds then bend or laminate ribs to the ribbands? If so you may be able to move all of the molds 1 1/2" closer to the widest beam and just fasten the ribbands to the "corner" of the 1 1/2" edge.

  3. #3
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    Default Re: Mold Fairing Technique

    Quote Originally Posted by ONeillBoatworks View Post
    .Do you stick to fairing along plank seams or water lines or will any reasonable point from one frame to the next produce the right bevel?
    You will need to run the fairing batten in every direction possible. You are fairing a complete surface, not a series of lines.
    It really is quite difficult to build an ugly wooden boat.

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  4. #4
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    Default Re: Mold Fairing Technique

    Quote Originally Posted by Gib Etheridge View Post
    Are you going to apply ribbands to the molds then bend or laminate ribs to the ribbands? If so you may be able to move all of the molds 1 1/2" closer to the widest beam and just fasten the ribbands to the "corner" of the 1 1/2" edge.
    Gib is right. That's how it's done. The forward edges of the molds forward of the midships station line are placed on the station lines forward of the midships station line. The after edges of the molds aft of the midships mold are placed on the station lines aft of the midships station line. The centerline of midships mold is placed exactly on the midships station line.

    This set up will reduce, if not eliminate, the need to do a lot of fairing of the molds if they are laid out and cut accurately. They should be faired with a batten in all directions (horizontally with the waterlines and diagonally as well,) because this will reveal any errors in the accuracy of layout, cutting, and setup. If you are careful doing the layout, cutting, and setup, you shouldn't find any unfairness in the shape defined by the set up molds. If you do, it is very easy to take a few licks with a plane to fair the corner of the mold. Rubbing the face of your fairing batten with some carpenter's chalk will easily reveal high and low spots where the chalk has transferred to the mold corners, or not.

  5. #5
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    Default Re: Mold Fairing Technique

    I do like the batten on the outside of molds much better than the method I used (the Herreshoff setup from "Building the Columbia Dinghy") and I will definitely use it in the future.

  6. #6
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    Default Re: Mold Fairing Technique

    Quote Originally Posted by ONeillBoatworks View Post
    I do like the batten on the outside of molds much better than the method I used (the Herreshoff setup from "Building the Columbia Dinghy") and I will definitely use it in the future.
    The "Herreshoff method" as in Building the Columbia Dinghy is, I believe, designed for the purpose of production work, knocking out one after the other off of the same jig, hence somewhat unique approach. It also makes bending the steamed frames much easier, or so it would seem. One-off construction might justify another approach, though.

  7. #7
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    Default Re: Mold Fairing Technique

    I am going to be building more than one so having a very solid jig is useful for sure. Half the frames are steamed on the jig and the other half once the hull is off the jig (allowing the first half of the floors enough space to be riveted to the frames). For one-off construction you might want a jig that isn't as substantial for costs purposes. I used 2x10s for the molds spaced every foot on a 12' boat. That's a lot of timber!

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