Saturday, March 5, 2011

Trap Skiff-Hanging the Garboard

On any boat…The Garboard Plank is the first plank on either side of the keel.

I had temporarily hung the garboard plank last March. …then I was interrupted by a vacation to Kentucky and some medical issues…Summer arrived and it was time to be here I am a year later! I looked over the work, did some adjustments, and decided where to scarf the plank. A Scarf is one way to join two pieces of wood together…it is a tapered joint which can be seamless and as strong as one piece of wood. If I use a 12 to 1 scarf ratio, then each scarf in the 9mm thick wood is approx. 6 inches long. I know there is always a debate about how long of a scarf to use…the longer the scarf, the greater the overlap and the more surface area to glue the lap together. A longer scarf allows the joint to have bending qualities more like the rest of the plank…the glue in the scarf make it stiffer than the unscarfed wood, so a short scarf tends to create a “hard” spot in the plank…if you would let the plank naturally hang down while sighing along its edge, look close and you would see where the scarf is…the shorter the overlap, the more noticeable the scarfed area is. It doesn’t bend as smoothly as the rest of the plank. I tried to take into account where on the hull the scarfs will be by examining where the most twist in the Garboard plank is…or where the planking run was flatter…is the area somewhat flat or is the plank under a lot of tension, such as when near the bow or stern. The Garboard on a Trap Skiff twists nearly 90˚ at each end…a lot of pressure there.

So I had a choice of either placing a scarf near the bow or stern where the plank was twisting or placing two scarfs amidships…making a scarf is not a big deal, so I chose two scarfs, about 3’ apart, where the hull is flatter.


  1. Great shot! I have been thinking about building an NTS so I will be watching your progress with great interest. What kind of plywood are you using for the keel and for the planking?

  2. Hey Dennis,

    I'm using 12mm okoume ply for the keel and 9mm for the planking. Well I should say I was supposed to use 12mm for the keel...several glued layers to build it up to 1 inch or 1 1/4. I used to work at Peterson Builders when they were building 225' wooden minesweepers for the Navy. That project produced a lot of scrap wood. I had several pieces of 5/8 treated ply that were used for bulkhead material on the MCM's. Since I had that wood, I used one layer of 5/8 and then a layer of 12mm for a total of 1 1/8".