Transom, Chine and Inwale... the build resumes Late July

TRANSOM AND STEM...



Transom mounted to strongback.

Now that we are flush with material (for the forseeable future anyway) I am pushing forward with finalizing the frames.  I left off in the assembly with the transom.  That would be the back of the boat that you typically see adorned with the ship's name.  This particular one is made from two layers of 1/2" ply, laminated together with epoxy glue and screws.  This will also be covered in a layer of mahogany lumber and finished clear with a thin white band of paint along the sides and bottom to represent the edges of the hull planking. That comes later. This paint border is a design feature that works for this classic take on what is already a classic, and thanks Brad for the "yacht styling" tip.

Stem and Frames #2 & #4

The other end or bow (pronounced as in "to take a bow") needs a vertical post for the plywood to join.  This is referred to as a stem.  Like the transom, it attaches to the strongback to hold it in the proper position relative to the other frames and at the proper angle. You can see it to the right. At the same time I attached the last two frames that form the short fordeck.  They are different in that they have a solid, arched deck beam.  You can see it in the same photo titled "Stem and Frames #2 & #4, hanging at the bottom (remember we are building upside down).

INWALE & CHINES... 

Now that all frames are in place we need to attach them together along the boat's length.  The chine and inwale serve a structural purpose and provide a fair curve along the hull to scribe the plywood sheets along.  As a structural element they provide reinforcement along the plywood joints where bottom meets sides, and sides meet deck. For the side to bottom joint I will use a 1" x 3" member referred to as the chine and for the structural member along the deck and hull side joint called the inwale, a 1" x 2".


Jig mounted to table with a chine clamped in place.

For material I am using the same clear southern yellow pine that the frames were constructed from.  So, my wife and I were back in the shop working both ends of the planer and tablesaw.  God Bless her... she wears the battle scars as proof that we just spent some quality time together. 
The maximum length of my stock is 12' so I need to join the 12' strips into longer pieces so that when they are bent to the pre-notched frames, the resulting curve will be smooth and continuous.  If I tried to just join them at a frame, the result would be a hard bend or kink... not good.  So, how is this accomplished you ask?  Well, this is done using what is referred to as a scarf joint.  That is basically a very long, shallow angle milled or cut, on each end of the board matching each other and provides a lot of glue area to join the boards.  The first step is to cut the joint.  Some plane these stacked in a pile, others saw.  I used a router with a jig constructed on the table saw that gave me 8" of joint on a 3/4" thick board.  Why 8"? Use the rule of thumb that you want 8x (or more) of the thickness of the board being joined.



Bottom view of router base

Marking the angle to joint to

I cut a piece of ply that attaches to the router in place of the plastic base via the same screws used by the original base.  I also slid the router perpendicular to the jig and marked the stopping points for the router bit.  I used some scrap pieces of hardwood to create stops so that the bit wouldn't bite into the jig at the ends of travel.  also, I screwed down a piece of 3/4" x 3/4" scrap along the inside edge of the jig to stand the chine off so that I could cleanly pass the router bit across the chine.  The only thing that I found was that when I got near the feather edge of the cut, the router bit would grab that piece hanging onto it and tear it off.  I decided that instead of nibbling off in multiple passes, I would just marke the angle and take it to the jointer to hog out almost all of the wood and just use the router to clean and true up the joint.  Like so...



Now that this is done I have a stack of scarfed pieces ready for glue...

Folks, we can't stress this enough but when you truly have a wood joint that is going to see alot of tension (and bending these chines in two different directions at once qualifies) you need to use the strongest glue possible.  If this joint may also see moisture (the bilge of a boat), you need a waterproof glue.  Not water resistant, waterproof. You don't want this joint coming apart down the road.  Use epoxy.  We will use in excess of 20 gallons on this project and its is time to put on the respirator, gloves, glasses and whatever else is needed to keep it out of your lungs, eyes and skin and get with it.  We use a combination of fillers to add

thickness to the consistancy and strength.  For this purpose I use fumed silica (respirator) and milled fibers.  The epoxy is Raka brand which I like and is a 2 to 1 ratio resin (2 parts resin to 1 part hardener). Observe all safety precautions, ventilate the area well and work quickly if you are using a medium hardener and, it's 90 degrees out like I did.  To extend this "kick over" point, immediately pour your mix into a flat paper plate to spread out the surface area.  Epoxy sets faster if contained in a cup.  I laid down a layer of plastic film over my work bench and started gluing. I used pocket hole screws with a backer piece of polyethelene cutting board with two screws across the scarf to serve as a clamp until the following day.  They came out easily and the HDPE backer just fell off.  In the "Transom View" you can see the finished pieces laying across the frames, approximately 28' or so long. 





Transom View... Chines and Inwales laid across frames ready to be fastened into notches

Now, all that remains is to get these on the boat.  Notice that there are notches in the corner of the frames. There are also notches in the transom at the upper corners and notches where the arc of the transom begins.  The purpose of these is to recieve the chines and inwales.  Since these will lie at an angle to the vertical plumbed frames, I will skip the gluing now and install with #12 - 316 stainless 2" screws...2 per joint.  When the boat is flipped, we will create an epoxy glue fillet at these joints and along the chines and inwales from one end to the other for added strength. We started in the middle and worked our way toward each end.  They bent in just fine. Here is the final result... 

Ready for Plywood

 

In this view you can see the compound curves and get a sense of the shape of the hull.
In the foreground you see a 4' x 8' cut table for ply.  Set the saw depth slightly deeper than the ply and cut through. It will only make a harmless kerf on the top surface of the 2" x 4" frame.  Everything sits in place, no dropping parts on your shins and cord.  It's about 32" tall.