"Marksbark": An 18' Oar Cruiser

“Marksbark” is a Jim Michalak design for a row boat (can also be paddled) that is, in effect, a stretched out Toto (one of Jim’s most popular designs).

Plans for "Marksbark"

Specifications:

• Length: 18' 0" (5.4 m)
• Beam: 36" (914 mm)
• Weight: 90 pounds (40.1 kg) as designed
• Water Line Length: 16' 7" (5.1 m)
• Water Line Width: 29" (737 mm)
• WLL/WLW Ratio: 6.9:1
• Hull Speed: 5.5 knots, 10.2 kph, 6.3 mph

Conversion to an Oar Cruiser:

By adding full decking, a coaming, out riggers for the oar locks and semi-permanent bows (to support a removable tent), she could be converted into a very fast, sea-worthy oar cruiser.

Marksbark Converted to an Oar Cruiser

The bottom, chine and topside panels were cut as designed, which ensures the hull shape is exactly as Jim designed. Once the hull was constructed, the following additions/changes were made to create the oar cruiser:

• Two full bulkheads, with tops crowned 2" (51 mm), were installed 6’ (1.8 m) and 13’ (4 m) from the bow. 
• The frames outboard of these two full bulkheads were permanently installed with the tops crowned to the same radius as the new bulkheads.
• The two new bulkheads are just slightly less than 7’ (2.1 m) apart, allowing a 7’ long sleeping area once the temporary form (10’ [3 m] from the bow) was removed.
• The foredeck is 7’ (2.1 m) long from bow to forward edge of the cockpit.
• The afterdeck is 6’ (1.8 m) long from the after edge of the cockpit to the transom.
• Side decks were installed leaving a 2’ (0.6 m) wide cockpit, 4’ (1.2 m) long.  
• A 3” (76 mm) high coaming was installed on all four sides of the cockpit.
• A ¾” (19 mm) by ¾” strip was installed on the outer top edge of the coaming  to stiffen it. And another ¾” by ¾’ strip was installed on the inner top edge of approximately 2.5’ (0.8m) of the sides of the cockpit coaming. This combination of strips support the outriggers and enables them to be removed, rotated 180 degrees (to act as ‘tables’ while anchored) and adjustable to accommodate the rower.  
• The span of the oarlocks using the outriggers is 4’ (1.2 m) , accommodating 8’ to 8’6”  (2.4 to 2.6 m) oars.
• The forward hatch is 16” (406 mm) wide by 14” (356 mm) long, providing access to the forward compartment;
• And the after hatch is 14” by 14”.
• The support bows are bolted (using wingnuts so they are easily removed for car-topping) to the coaming. The bows provide 4’ (1.2 m) ‘headroom’ from the top of the floorboards, sufficient for sitting on a cushion.
• The floor boards are in two sections (spanning the space between the two new bulkheads (6’ [1.8 m] and 13’ [4 m]) and consist of cross pieces ½” (13 mm) apart. This enables the rowing seat and footrest to be ‘hooked’ into the floor boards to provide a solid and adjustable rowing station.

Interior of Marksbark Oar Cruiser Conversion

If I were to build it full size, I would consider using SOF for the decks in order to lighten the overall weight. Jim calculates the boat will weigh 90 (41 kg) pounds as he designed it, using ¼” plywood. Adding the plywood decks would add approximately 30 (13.1 kg) pounds. 

Marksbark (bottom) Compared to Larsboat Concept Model

Summary-Pros:

• High WLL:WLW ratio (6.9:1) make this Oar Cruiser fast. Jim states in his write-up for the plans "…she'll hit 6 mph (5.2 knots, 9.7 kph) in good conditions and cruise forever at 4 mph (3.5 knots, 6.4 kph)."
• A cruising speed of 4 mph (6.4 kph) for ten 45" sessions per day results in 30 miles (48 km) a day cruising.
• Lowering the stem/transom tops, and increasing freeboard midships, resulting in a reverse sheer, reduces windage, but keeps the underwater lines as designed.
• Adding decks, coaming, splash guard all add up to making her very seaworthy.
• The two water-proof compartments provide storage as well as emergency flotation.
• Jim feels Marksbark could be rowed at 6 mph (9.7 kph) in good conditions and "cruise forever" at 4 mph (6.4 kph).

Summary-Cons:

• The addition of decking and bulkheads adds approximately 40 pounds (18 kg) to her weight. Long narrow boats as heavy as this can be car-topped by one person.