Building a Wood Duck 12 - Installing footbrace mounting studs

Now it's time to install the footbraces. CLC has this in their manual towards the end of the process, but since I'm using the no-hole stud-mount footbraces, it makes more sense to install them now, before the deck is attached.

My preference for mounting footbraces this way is based on the idea that I'm going to a lot of trouble to make a watertight hull. In that case, why would I want to punch holes into it? Some people are uncomfortable with the idea of metal parts held on "just" by glue, but the fact is that these glued studs are actually stronger than through-bolts.

Through-bolts transfer the entire load to the front and back of the hole and to half the area under the bolt head. Since the hull is so thin, there's not much surface area to distribute the load over. Also, the sharp threads are cutting into the wood, while the bolt head is trying to compress it. There's a lot of force concentrated into a small area.

The studs, however, ride on top of the wood. They distribute the load through the epoxy putty over the entire area under the glass patch, half through compression, half through tension. The area is about 4 square inches. The force is spread out and diffused through the bedding and the glass patch. Best of all, the wood fibers under the stud are intact and contribute their strength, too.

Click on any image below for a larger view

Gluing the studs

This is a trick I worked out on a previous boat. It guarantees perfect alignment and placement, but only works before the deck is put on

The studs are assembled onto the footbraces (don't use the fiber nuts that came in the kit, save them for the final assembly and use standard nuts, instead) and the whole assembly is glued to the inside of the hull using the standard woodflour epoxy mix (mix it thick). The clamping system is effective, yet simple. The plastic sheets are there to catch drips.

Stud glued

Once the glue has cured, remove the footbraces from the studs. As you can see, for the initial glueing I didn't use much epoxy. Wrap plastic packing tape around the threads to keep them clean.

Bedded stud

Here the stud has been bedded in epoxy and covered with a patch of glass. Note the orientation of the patch. This way both sets of thread (warp & woof) share the load of a foot pressing forward. If the patch had been installed with the sides parallel to the sheer, the vertical threads would have made little or no contribution to carrying the load. This orientation is approximately 50% stronger.

Just as with the taped seams, the glass is the primary structural component. Therefore you only need just enough putty bedding to smooth the transition where the glass goes over the stud. Any more is wasted weight.

Perfect fit

The footbrace fits perfectly over the studs. It's ready to be bolted on when the boat is complete. In the meantime the threads on the studs need to be covered with plastic tape to keep them clean.

Ready for deck

The hull is now ready to be joined to the deck (after a bit of trimming on the bulkhead, of course). The seams are taped, the stem & stern pieces are in, the interior is completely glassed and the footbrace studs are attached. Good to go.

Page 1 - In the beginning
Page 2 - Hatching a Duck
Page 3 - Stem & stern pieces
Page 4 - Interior fillets & glass
Page 5 - Glassing under the deck
Page 7 - Building the coaming, attaching the deck
Page 8 - Exterior glass
Page 9 - Graphite bottom, invisible hatch hold-downs
Page 10 - Final outfitting

Copyright © 2009 László I. Mórocz. All Rights Reserved.