Scarfing the chines and sheers

The weather has been too cold to do any epoxy work in the garage so after ripping the oak for the keel, chines and sheers, I moved to my basement to put them together.

The keel is a 4 inch wide piece of oak with 3/8" plywood epoxied and nailed to it. The design states that the plywood helps prevent splitting. 

The chines and sheers need to be 18' long so they can extend from the stem to stern. Well, you usually can't buy lumber that long so you have to make it.  This is done by gluing two pieces together using a scarf joint.   A scarf joint is a long angled cut that provides sufficient surface area for the epoxy to make a strong joint that is the same dimension as the pieces being joined.

To make the joint, you need a way to make the cut.  A sliding miter saw will do it, but I didn't have one so I made a jig for my circular saw.

The oak pieces are inserted in the slot and the circular saw is moved along the guide to make the long angled cut. This picture shows how the two cut pieces would be aligned and glued to make the joint.

Scarf joints are expressed in ratios such as 8:1 or 12:1.  An 8:1 ratio means that 1" material would have an 8" long cut. If you know your trigonometry, it as also means an angle of about 7.2 degrees, which is the arcsin of 1/8.

I used some scrap lumber to make a long right angle fence to align the two pieces I was joining.  I lined the box with parchment paper, applied epoxy and then used the fence to align the two pieces.  I used a nail gun to nail the two pieces together so the joint wouldn't move while I wrapped the paper and applied two clamps per joint.   Here is the resultant joint.

 

I thought I could remove the nails after the joints set up. I had nailed through a small scrap of 1/4" plywood which I could pry off to expose the nail head to give me something to grab.  However, the combination of white oak and epoxy made removal almost impossible.  The black circles in the sheer above mark where the nails are still embedded. 

The nails aren't a problem in the chines, but they are in the sheers.  The lumber is 13/16" and sheers need to be 5/8" thick per the plans.  I planned to use a planer to reduce the thickness.  The embedded nails now present a problem as I cannot run them through the planer.  I tried several Dremel bits to grind them out but nothing worked very well.  I ended up using a 1/4" spiral router bit set to a depth that would give me the clearance needed.  I tilted the router into the nail marks and it worked very well as it cut through the nail and wood.   When planed to finished thickness there should be but a small indentation.    Here is a picture of the routed out nails. 

I hope I measured correctly!  I guess I'll find out when I plane the lumber to thickness.