Monday, April 5, 2010

Design of the jig

(top) - All componets for jig
(middle) - Aft view of jig
(bottom) - Front view of jig

The jig is designed on having a vertical frame at a one-foot spacing from the bow to the midpoint with one and a half foot spacing from the midpoint to the stern to reduce the amount of materials used in the jig.

My intentions with this jig design were to employ the use of CNC routing to create very accurate profiles and positioning mechanisms so that it would drastically reduce the amount of time spent on constructing and aligning the jig. The panels will slot into place on vertical boards that are attached to a table. The table will be constructed out of 140 x 45 mm pine for the edges to create a very stiff and sturdy table (as each full sheet of 18mm MDF weighs approx 30kgs). This is important because of how the jig is setup, without the use of battens to fair in the sections it must be very stiff to provide the accurate hull shape.

Another design consideration with the jig was transport and storage. With this design the flat jig MDF panels can be laid flat in a small box trailer and the table tied on top or stored flat somewhere saving space, also the table will act as a work bench once the hull is flipped over and a sheet of form ply is placed on the table top.

The design was given to the CNC cutting workshop just before Easter and are expected to be completed in mid to late April. At this point hopefully centreboard and rudder will be completed and the focus can be placed on the jig and hull shell.


  1. How are you planing to attach the foam to the jig? Are you able to post a lines drawing of the final design?

    I think you have under estimated the amount of resin you are going to need. Given you have 50m^2 of 200gram cloth and achieve a resin/fibre ratio of 1:1 that gives 10kg of resin. You still have to include the resin/bog used to prime the foam and for gluing in the frames/floor/decks etc which can be quite a significant amount. For example to prime the foam for just the hull ~6m^2 you will use around 200gram/m^2 on both sides which equates to 2.4kg.

  2. Cheers thanks for that Dave, I'll make sure i order abit more resin.

    To attach the foam to the jig i plan to drill holes in the vertical MDF jig frames at an even spacing (prob 100mm). I then intent to use a curved needle and thread/sew the foam sheet to the frame. Then i mix up a bog and pipe it into all the little holes in the foam that the thread (either glass roving or a natural fibre) has gone through. When the bog cures the stiching on the outside can be cut away as the threads are glued to the foam. This gives an un-interuped surface on the outside to glass.

    Then when we need to take the shell off we will use a blade or a blade on a stick and cut all the threads from underneath and lift the shell off "Fingers crossed"


  3. Adam,

    Given the way you are planning to attach the foam I'm going to suggest you run a few stringers length ways to give support between the frames. The reason I suggest this is that your design has compound curves in the hull and the foam will not lie fair between the frames and you will end up with hollows (relative to the your desired design shape) and hard spots at the frames. Also, an added bonus of the stringers is that the foam is much easier to tie down to the jig.

    A tip is to cover the edges of the frames and stringers with brown packing tape as epoxy does not stick to it.