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by David Mancebo - Rolling Bay, Washington (State) - USA

I earned my living for 10-years as a Shipwright, 5-years as a Yacht Designer and 30-years as a Naval Architect. I am now retired from Naval Architecture and have not earned my living as a Shipwright for a long time. But I still design boats now and then. Going over my sketchbooks, there are many boats Duckworks readers may enjoy. I thought Tule in the attached article would be a good example.

The sailing scow Tule is a 20-year old preliminary drawing from my sketchbook. It is a stable family cruiser that sleeps 4-people in two double berths. It has a table that seats six, a modest galley, curtained-off head area, large storage space and a huge cockpit. Tule can sail in very shallow water and dries out flat when the tide recedes. As a scow, it is very stable and has lots of living space for its size both on deck and below. It will pound like crazy under power and at anchor in a chop but is strong and seaworthy in protected waters.


I have a family interest in scows. Not only was my very first cruising experience in the mud-flats and sloughs of San Francisco Bay, but my grandfather immigrated from the Portuguese island of Sao Jorge and was working on scow schooners in San Francisco Bay during the 1906 earthquake. The scow schooner was beached for loading when the earthquake struck before dawn. Everyone aboard was in an absolute panic until calmed by my Grandfather who knew just what was happening. Sao Jorge, Azores, is a volcanic island and earthquakes are very common. When the sun came up, they could see the smoke from the burning city.

All my designs start with a sketch, including profile, arrangements, construction section, weight study and preliminary hydrostatics. Many of the designs in my sketchbook were not completed for various reasons and Tule is a good example. I long ago lost the customer that was interested in the boat. Ideas like this need to be shared rather than dying in my sketchbook.

The sketch has all but the weights and hydrostatics. The weight report shows empty weight of about 1,200 pounds and hydrostatics shows a very high righting moment for a boat this size. The 6-hp outboard will allow a cruising speed of 5-knots at less than 0.4 gallons per hour. The boat really won’t go much faster with a bigger motor, due to the short waterline when upright. The heeled waterline while sailing is over 18-ft. I would expect Tule to sail upwind at 5-knots in the right conditions and better than 6-knots on a reach. Tule is too heavy to really plane but on a good size wave could surf up to maybe 10-knots.

Construction is straight-forward plywood on frame with epoxy glue. There are only 3 frames or transverse bulkheads. Most of the hull, deck and house are 9-mm sande plywood. I changed the sketch from okoume plywood to sande plywood before scanning it since marine sande is inexpensive and reasonably light. There are two longitudinal bulkheads that support the bottom allowing it to be relatively thin at 15-mm (0.6”). 9-mm ply is first glued to the frames. This is followed by 6-mm just glued and stapled in place on the bottom only. 1/2” stainless staples can just be left in place and covered by 6-oz fiberglass cloth. The forward 2/3 of the bottom should have polyester fabric (xynole or dynel) if beaching on sand or rocks is likely. Polyester has much better abrasion resistance than fiberglass.

Pre-finish of most plywood panels really speeds up construction. The plywood is epoxy sealed, primed and finish painted on the inside as flat panels on saw horses. The interior hull structure is also epoxied sanded and varnished on saw horses before assembly. Whenever a joint is to be made, use a pencil to mark the glue joints, scrape off the paint or varnish from those areas with a paint scraper or chisel and lightly sand. After gluing up, clean off the squeeze-out. I have built everything from dinghies to 40-foot boats this way. It is amazing how much faster this method is compared to sanding and painting the inside of a boat. Drips and runs are never a problem and the paint lines are really crisp and look good. 

This scow is modeled after my experience in San Francisco Bay. Summers are often cool and damp with plenty of wind. The cabin can be buttoned up tight in driving spray while sailing in these conditions. When at anchor, good ventilation is available with main hatch and forward hatches open.

There is no real ballast on Tule. If the wind is strong enough, it can be capsized even with it’s high righting moment. Buoyancy forward and aft will provide enough freeboard to bail out the boat in the unlikely event of capsize. Because there is no ballast, Tule is light enough for trailering with a modest vehicle. I think boat, trailer and gear could be kept under 2000-lbs, though 2500-lbs would be easier.

At 19’-6” length on deck, Tule is the maximum length that can be built in common suburban garages. Larger space would be much easier. Tule is 8-ft wide without the guard rails. Legal trailering beam in almost all of the USA is more than 8-ft. The bowsprit and rudder are removable for trailering. The bowsprit is short enough that crew can reach the headstay while standing on deck. The mast is in a tabernacle and is light enough that most people will not need a gin pole or other device to raise or lower it. Also the 3-stay rig is quickly tuned.

The side by side double berths with settees are very spacious. The settees have good legroom and can squeeze in 6-people. Cabin ports offer a nice view outside. The table is big enough to dine with 4-people. The rectangular berths at 39.5”x80”are larger than most v-berths.

The centerboard is not weighted. Tackle is needed to hold it down as well as haul it up. The lower opening of the centerboard trunk has an over-the-counter gasket that keeps most sand and gravel out of the trunk and hydrodynamically seals the trunk when sailing. The rudder can be used partially raised, though it would be hard work holding the tiller on a windy day for extended periods. When sailing up a creek or shallow flat, the rudder and centerboard can be substantially housed, reducing draft to less than a foot.

Tule has 4’-6” headroom. Standing headroom is not very practical on an unballasted 20-footer. However, the hatch next to the galley allows standing headroom and good ventilation while cooking. There is no good place for a head on a boat this size. The position shown, next to the hatch at least has good ventilation. A curtain offers visual privacy. The head can be used anchored or sailing and berths do not need to be disturbed to get to it.

Tule has a very large cockpit sole, enough room for folding chairs and a roll-up table if desired. Lounging in folding chairs under a boom tent would be very comfortable in many conditions. The foredeck is also large and the cabin top is a good seating height. Large storage spaces under the cockpit can be accessed from the cabin but flush hatches in the cockpit sole would make access easier.

I have no plans to finish this design for now, though this could change. Feel free to use any of the ideas on your own boat.

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