Making the Thwarts

In the last post I stated that I was ready to start making the thwarts.  Well, almost….

I need to finish the centerboard case once and for good.  That means installing the centerboard in the case, and then mounting the case more or less permanently into the hull.

A bronze pin is used as the pivot for the centerboard, but none of the local boat chandlers had any in stock.  I thought briefly about using stainless steel for the pin, but all of the other fittings are bronze and I didn’t want to run the risk of galvanic corrosion.  A check on the interweb verified that Duckworks (www.duckworksbbs.com) carried bronze rod.  I’ve ordered materials from Chuck and Sandra before and always been very pleased.  An order was placed Sunday evening and the bronze rod was in my mailbox on Wednesday.  With the bronze stock in hand, it was easy to cut off a short length for the pin and mount the centerboard.

2017 11 04 Installing the centerboard.

To mount the centerboard case, I used bronze screws and Life-Caulk sealant by BoatLife.  Some people permanently epoxy the centerboard case to the hull, but I wanted this one to be removable for future repairs, if necessary.  Make sure you wear old clothes when using this stuff; it has a habit of getting on everything.  NOW the centerboard case is done, and we can start thinking about the thwarts in earnest.

Thwarts are structural members of the boat that help stiffen the boat.  They are so named because they run athwartships, meaning from one side to the other.   Tammie Norrie has two thwarts, and serve the dual purpose of not only stiffening the hull, but also bracing the centerboard case.  As an added bonus, thwarts also serve as a convenient place to sit, and will be used for sitting when Tammie Norrie is being powered by oars.

Two of my boatbuilding rules come into play when making the thwarts:

Rule #2:  There’s only two types of lumber – not cheap and very expensive.

Rule #4:  Always make a pattern for complicated shapes.

The thwarts are made from cherry (very expensive), so we’re going to make a pattern first from shelf pine stock (not cheap).  The thwart has a compound bevel where it meets the hull, so to make life a little easier, I’ll intentionally cut the pattern a little short to start with.  I’ll “stretch” it to full length later on.

The thwart is attached to the hull by cleats on either side.  These are also made from cherry.  The temporary thwart is clamped to the centerboard case, with the edge almost, but not quite, against the hull.  The stock for the cleat is then clamped to the hull and spiled to fit against the hull.  The edge against the hull is curved, and due to the flare of the hull, that curve will be beveled.

2017 11 11 Spiling the thwart cleat.

This tends to be pretty much an iterative process.  Cut, check for fit, mark the excess, and repeat.  Right now I’m only concerned with the face that meets up against the hull; the inboard face has a decorative curve, but that comes later.

2017 11 11 Temporary thwart with cleat.

It takes a bit of work, but patience will get you four cleats.  In the photo above you can see the forward cleat on the port side; I’ve laid masking tape against the hull so I can mark where the cleat fits against the hull.  Since the hull has already had two coats of Clear Coat, I’ll sand the area where the cleat lies to insure a good bond with the epoxy.

Repeat the process for the starboard side, and then it’s time to “stretch” the temporary thwart to full length so we can use it as a pattern to cut the real thwart.

2017 11 11 “Stretching” the temporary thwart.

A diagonal cut across the temp thwart and some scraps gave me a full length pattern that I could use to make the real thwart from cherry stock.

2017 11 11 Aft thwart with cleat.

With the thwarts cut to shape, we can now cut the decorative curves on the inside edges of the cleats.

2017 11 12 Final shaping of cleat.

The cleats will get varnished; this is a lot easier to do prior to epoxying the cleats to the hull than waiting until after they are glued in.  A total of six coats of varnish are applied to the cleats.

2017 11 12 First coat of varnish on the cleats.

With the varnish complete, I’m ready to epoxy the cleats to the hull.  To hold the cleats in place while the epoxy cures, I’ll clamp the cleat to the thwart, which in turn will be clamped to the centerboard case.  It sounds like a dubious method, but it worked.  While I want the cleats to be epoxied to the hull, I do not want the thwarts to be permanently attached.  The thwarts will be held in place with mechanical fasteners only, no glue.  To keep from gluing the thwarts to the hull, I wrapped the ends with waxed paper.  Since Christmas is not too far away, this is good practice for wrapping presents.

2017 11 19 Covering ends of thwarts.

Finally, the cleats can be attached to the hull.

2017 11 19 Epoxying cleats in place.

We’ll let the epoxy cure, and then fasten the thwarts to the cleats and the centerboard case with temporary fasteners.  In the photo above, you can see the cross brace running from wale to wale.  Tammie Norrie has two cross braces, each located at the oarlock location.  They have been in place since the boat was turned right-side up and the molds removed.  When the thwarts are fastened in place, those cross braces will finally be removed.

 

 

 

 

2 thoughts on “Making the Thwarts”

  1. I’ve been doing woodcraft for more than 30 years, professionally and as a hobby…. STILL impressed with Adm. Al’s craftsmanship !…. incredible patience Al…..

    Like

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