Building the Transom, and Stem

Transom
The transom dimensions need to consider that it will be holding a 20″ long shaft outboard motor. Since the transom is angled back at 15-deg, trigonometry tells us that a transom height 20″ will yield a little longer vertical height. But the calculator tells us it’s only about 1/2″ so we’re not going to be too conserned about it.

Sea-Trial Edit – After the boat was built, I bought a Yamaha 15hp with a 20-inch shaft length, only to find out that the dimension shown below was not 20″, but more like 23″. So I had to build up the transom height with a “spacer” that allowed the cavitation plate to run slightly below the boat’s bottom. That’s why you’ll see the “on-the-water” pictures with that spacer.

Relationship of Transom Height and Cavitation Plate

Transom Fab

The transom was made up of 3 boards that were attached together to make the 20″ height. To located pinning locations, both of the boards long edges were placed together and marked at 5 spots, equal distance from one another. The boards were separated and a hole guide was used to drill 1/4″ diameter holes at the marked spots, at a depth slightly more than 2″. Five drift pins were cut from 1/4″ stainless (316) rod at a 4″ length and the ends beveled slightly. The drift pins were inserted in one board and Titebond II glue liberally applied to both board’s edges. The boards were brought together and set in clamps until dried. This process was repeated for the 3rd board, however this board had 6 drift pins due to the additional length.


Drift Pin Setting


Transom Drift Pin Locations

Stem Fab

The stem is the very front of the boat and typically made sturdy wood to survive a mishap at the dock, etc. This skiff will have a 2-piece stem, named the stem and a false stem. The stem will be used to attach the side plywood and the false step will go in front of the stem and plywood end to give the front a nice appearance. Both the stem and false stem were made out of thick stock white oak that we bought off an Amish mill about 4 years ago and was well seasoned. These pieces didn’t need to be solid as a laminated build up would have worked just as well. Slightly green would work as well but finally encapsulation in epoxy would have to wait a few years after they were installed.

When the chines were being laid out, we sketched out how the stem was going to be arranged, so we could understand how the chine will mate to the stem.

Layout of Stem Components and Dimensions

The chines were attached at the stem end with a small block so they would retain shape and allow attachment to the future stem. This small block was cut 24-deg on the sides to permit 48-deg entry angle and the bottom of the block was cut at 30-deg to allow the stem to rake at 30-deg. It’s width determined from the sketch.

Chine Block at Stem

The stem was cut out of some leftover 3×4″ white oak I had. As it has a 48-deg entry angle, the saw was set to 24-deg and the width were adjusted to agree with the sketch. The bottom of the stem was cut at a 30-angle so it would sit flush with the bottom. The top was cut at an arbitrary 32″ because I know this is too long but plan on cutting to fit later.


Sawing Stem Entry Angles

Installed Stem

False Stem The false stem was ripped from stock at a 48-deg angle with the base of false stem equaling the nose of the stem that includes plywood thickness. The false stem is blunted (not sharp as shown in drawing above) because the sharp edge would be easier to damage plus it will be difficult to wrap the fiberglass cloth around a sharp edge. The false stem was cut to size by mitering the bottom angle to the stem angle (30-deg) and the top angle made at the shear line (I think it was 50-deg but I may be wrong). But the important thing about the top angle is that you want the shear line to stay continuous all the way forward. The leading edge of the false stem was provided 4 countersunk holes to accept four #12 x 3″ 316SS screws. The countersink was to a depth that allowed 2″ of screw into the stem. A dry fit was performed to locate the attachment holes on the stem. Then the false stem was removed and a coat of PL Premium was applied to the faying surface. The false stem was then permanently attached to the stem. After the glue dried the stem was trimmed down in height to 2″ above the shear line. This is personal preferences as I have seen boats that keep it 4″ high and others cut it flush.


False Stem Ready for Installation

 

IMG_0281.JPG

Glueing (Noting stem has been trimmed to height)

 

 

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