Sunday, May 30, 2010

Jig is finished

We managed to finish lining up the jig on Saturday and covered all the edges in packaging tape and plastic so that the foam will not stick to the jig. We put a tape measure of the jig and discovered that it had grown 20mm in length somewhere along the line. I spent several hours thinking about this today and for the life of me still can't find out where we went wrong. I was pouring over this drawings, 3D cad model and measuring everything on the jig, everything was as it was supposed to be except the final length. So once i work it out I'll let you know what it was. This does effect the boat (especially the bow) but it looks like we will be able to fudge / fair it in and we should be alright.

We began placing a full sheet (2200 x 1200 x 10 mm) of foam over the back half of the hull and tested out our methods of attaching the foam to the jig. We tried stitching the foam to the jig with a non-waxed sail makers thread and a small plastic spacer on top (so it would pull through the foam). We would then tighten this row of stitching in one go and pull the foam down to the jig surface.

At this stage its looking like the jig design of only using lateral supports, although simple to setup and line up it may not provide enough support to the foam sheets. As you can see from the last photo we are getting an uneven shape / surface at the chines. I feel this is because of several reasons, the first being that we are pulling to tight on the sewing thread and flattening the sheet against the top of the jig frame, rather than pulling it down to the one edge, which it is intended to sit on. To get around this we are going to try and develop a better way of attaching the foam sheet to the jig frames, which we and adjust each "stitch" on its own.

Secondly, because of the large sheet size it may require it to deform two much when it pulls down to the frame and forcing the foam to buckle or warp between the frame members. We can get around this by trimming the sheet into smaller pieces and joining them as we go, so that the joins form a "seam" such as in a sail.

The above image is of our rudder gantry that has been shaped and ready to be laminated


  1. re the additional 20cm....Perhaps you did not allow for the thickness of the frames

  2. Yeah It certainly looks like it would be as simple as that, especially considering the frames are made of 18mm MDF and the extra length is about 19-20mm, But it doesn't appear to be the case. Unfortunatly i'm fairly busy this week, but on the weekend i intend to go over every little measurement and find out were i went wrong.

  3. Deformation between frames: as I said in an earlier comment this was going to happen and the solution was to put in stringers. I don't think how you are attaching the foam is the main cause. I would suggest that using smaller sheets of foam will not fix the problem.

    Additional 20mm: As long as the mid length measurement is still within the rules an additional 20mm on the jig should not be a problem as you can trim the aft to the correct length later and in fact doing this can be make building a little easier. However, track down the cause of the extra 20mm just in case it affects some other aspects that you are not aware of at this stage.

  4. Thanks Dave. We are going to add longitudinal battens. Yeah, not too worried about overall length, as sure we will fit rules when we shorten it.

  5. Hey Adam, hope you did'nt mind the phone call! Dave has'nt posted anything yet as he has been quite busy getting the new boats out, he might get in contact at a later date. Must be another Dave on the blog. Can't wait to come done and have a look, I'm in the process of fitting a false floor to Cleaned Up, love getting my hands dirty!!! Spice