Sunday, February 20, 2011

Lapstrake Planking - cutting a rolling bevel

I recently received an email from Patricia Hong, asking for some clarification on the system I use for cutting plank bevels when building lapstrake (clinker).  I thought the email and my reply (attached to the original in red to save time - we were still in flood-recovery mode) might be of interest to others. Here it is, along with some illustrations for clarity.

That is me, cutting a plank bevel on the first Periwinkle
  1 :  Is this plane just drilled and a threaded rod put through the body of the plane ? I just drilled one of my low-angle block planes (on a cheap drill press) to accept a piece of brass rod which I had on hand. The rod is a neat fit in the hole, and can slide through to project any length I want, on either side of the plane.

2 :  Does the rod align flat  with the bottom / bed of the plane ? The bottom of the hole (and the bottom of the rod) are 11mm above the bed of the plane. I did this because I had access to cheap pine square-section moldings from the local hardware store which were 11mm x 11mm, and I used these as battens. See answer to next question. 

3 :  The guide / rod appears to be riding on the batten fixed to the mold stations and frames/bulkheads to  follow the rolling bevel of the laps .
Does this batten have to match the thickness of the planking stock in order to cut the correct bevel on the planking stock ?
No, it is independant of the planking thickness, but the batten needs to be the same thickness as the distance from the bed (or sole) of the plane up to the bottom of the rod (or the hole). So if a tangent to the rod was positioned 12mm above the sole of the plane, you would need to use a 12mm batten, and so on. All that you are doing is ensuring that the sole of the plane is parallel with an imaginary line drawn from the point where the next plank touches the mold (i.e. where the batten is positioned - in fact parallel with the bottom surface of the batten) to the bevelled lap on the plank which is already in position. I think my description is confusing, but the attached sketch may explain.

I hope you don`t mind all the questions No, I don't mind at all, and I'm only too happy to help where I can , and I hope they make sense to you Yes they do, and I think they are very sensible questions , as  I would really try my hand at clinker / (  lapstrake? )  boat building , and your method of cutting rolling bevels appears to be the best way to do this. Glued lapstrake is my favourite method of construction for small craft. It is nowhere near as difficult as some people imagine, but it does need the application of some common sense. Please let me know if you want more information. There are several excellent books on the subject,including Iain Oughtred's "Clinker Plywood Boatbuilding Manual" , Tom Hill's "Ultalight Boatbuilding" and "How to Build Glued Laptrake Wooden Boats"  by John Brooks and Ruth Anne Hill.

1 comment:

  1. Ross. That method looks very precise and easy to do. I just completed my first boat using the stitch-and-glue method, and though it turned out well, I would prefer to use the glued lap method in the future. A friend of mine built your Phoenix III and I'm very impressed.