Annie Buck Chesapeake deadrise oyster / crab working boat Build Log

[Ignatius27]

7. Annie Buck Build Log

Today's tasks: Fairing the hull, final dry fitting and gluing Pilot House and Cabin, re-doing engine block.

Progress pictures from the last couple of bench sessions. Spent alot of time shaping the hull following the 4 component hull lines:
(1) chine line rising at the bow from waterline to flare line,
(2) flare line with concave sides, from chine to sheer line,
(3) the sheer line from transom to bow, and
(4) bow line from false stem to tumblehome.

Shaping done mostly with home-made dowel/sandpaper jigs in 80, 120 and 220 grit.

Started using some cherry sheet stock for the top of the engine box and the back wall of the pilot house. It's the only 1mm sheet stock I have.

Showing pics of some real Chesapeake Bay deadrise oyster/crab working boats. The flare in the port and starboard sides has to be concave and the vertical angle of the bow is severe (over 60 degrees) in these type of boats. I added another layer of balsa at the bow to increase the verticality of the bow, which ultimately (after much sanding) will join both sides into a false stem.

I learned alot about the difference between "planing" hulls and "displacement" hulls. The Annie Buck has a planing hull because the chine and flared sides effectively lift the boat slightly above water by forcing water down along the line of propulsion -- as opposed to displacement hulls like a ship of the line or tall sailing ship which effectively pushes water outward from the hull for stability from the line of the keel.

After fairing the sides of the hull from the sheer line to the chine line, I planed the toprails to get the sheer line as close to smooth as possible. This pine stock that I am using for the hull is pretty grainy and accepts the planer well. The trick is that the grain of the transom is cross-ways (perpendicular) to the grain on the hull sides. So using the planer I had to pull up as the plane approached the transom. I separately used my sandpaper jigs to also sand a flare into the transom cross-wise from the line of the hull.

The front of the vessel will dry overnight, then tomorrow will be spent filling the sides of the pilot house with wood putty (homemade or store-bought), fixing a couple of divots in the inner wales and prepping everything for pre-staining / pre-painting with shellac. After the shellac dries, I will use the window decals as templates for stenciling on the window outlines and painting the windows. For the rear door of the pilot house, I will probably fabricate the door out of the 1mm cherry stock I have on hand.

 

[Ignatius27]

8. Annie Buck build log

Question for SoS members:

"To chine or not to chine, that is the tumblehome."

I learned something interesting about hulls today, that is, for some hulls the chine operates to make the lower hull more hydro-dynamic. By having a "second flare" below the bottom chine line results in a second convex flare leading down to the keel. This shape lifts the boat out of the water with less hull area, aka a planar hull, so it is more efficient at higher speed for crab boats.

This build of the Annie Buck has an odd feature...instead of having a full taper of the center line of the hull plate (this is a waterline model). The alternative paper model that you can build in this book "Fundamentals of Model Boat Building" has a rounded hull at the bottom of the bow. More characteristic of an oyster working boat. This is picked up in the scratch wooden build model of the Annie Buck deadrise oyster/crab working boat. As shown in the pictures, the bottom of the wood build ends with a rounded hull at the waterline.

The book also has a second, easier, paper model of the Annie Buck, but does not have the hydrodynamic flares as in the wooden build hull. So if you wanted to replicate the paper model in the wooden build you would need to add a SKEG below the water line.

What is a Skeg? I have the design for the paper model skeg in the pictures. It's a triangular spike that runs from below the bow to below the stern.

Having the Skeg below the waterline makes sense if you are more of an oyster boat because they operate closer to shore. The deadrise crabbing boats have what is called "tumblehome," which is a nautical design term that means the vessel has a wide / broad deck at the beam and the hull tapers to a narrow keel. The crabbing boats need to travel further from shore to crab so they need hulls that are efficient at the high speeds more characteristic of a sea going vessel.

A boat that has tumblehome would generally not have a bulbous rounded hull below the waterline. The Skeg makes a flat-hulled boat easier to sail straight at higher speeds than a flat-bottom boat. But it is like a sow's ear, the flat bottom of the oyster bost does not allow for travel at high speeds.

So if I were to make this a full-hull model instead of a waterline model, it would either have a thin hull at the keel (i.e., it has tumblehome), or a skeg appended to a rounded hull just below the chine line.

I chose to keep this build as planned, with the rounded hull at the waterline and an imaginary Skeg below the waterline.

But a full "second flare" between the bottom of the chine line and the keel would require convex shaping at the keel a second time. Choices, choices!

 

[DAWarden-(Jaager)]

This is the midship forward cross section of the French La Bellone 32 1757 captured by the English added to the fleet and renamed Repulse .
The blue arrows point to the tumblehome. The French were much better at it.

 

[JacquesCousteau]

Nice work! As DA-Warden suggests, tumblehome is the narrowing of the hull above the waterline.