Union Jack

$15.00 - $863.00
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a 31' semi-displacement trawler yacht

For a PDF study plan download, click HERE

Our UNION JACK offers a high degree of seagoing ability, comfort, and economy all with the security and safety of steel hull and deck construction. The low resistance semi-displacement hard-chine hull requires only minimal power for exceptional cruising range at operating speeds from 7 to 8-1/2 knots. Full walkaround decks include the security of a raised protective bulwark all around, forming a convenient full width cockpit seat aft. The rudder, propeller, and shaft are all protected from damage by a deep 1/2" thick solid steel skeg. Flaring topsides plus a deep convex forefoot deflect waves and cushion the ride when the going gets tough. The plans give options for either the curved cruiser stern, or the more basic transom stern.

Accommodations aboard the UNION JACK are especially complete and well suited to the cruising couple or family. The forward stateroom contains luxurious accommodations for two, isolated from the rest of the boat for privacy. The head is complete with lavatory and shower, while the stateroom has plenty of storage including a big hanging locker. The pilothouse features full circle visibility, a seat for two, space for working on charts, and sliding doors port and starboard for quick and easy access so handy when operating with a minimum crew. The main cabin aft features a complete galley with large ice box or refrigerator, a range with oven, sink, and spacious worktop. The L-shaped dinette is raised so that crew members can see out while seated, and also forms a berth for sleeping. The settee to starboard also converts to an upper and lower berth so that total sleeping capacity is five adults. For ship-to-shore use, you can carry an 8' dinghy on the housetop. Emergency steering provisions are accessible through the aft hatch, along with additional storage facilities. A watertight collision bulkhead separates the chain locker from the cabin area forward.

Construction of UNION JACK is aimed at the abilities of the amateur builder who has welding skills. Full Size Patterns provided make the lofting process unnecessary, however, a Table of Offsets is provided for those who wish to loft the lines. Hull lines are such that the sheet steel conforms to the framework without the necessity of heating or forming the plates. Hull, decks, and bulwarks are all welded steel construction, while the cabin superstructure and interior are conventional wood and plywood construction with exterior plywood surfaces sheathed in fiberglass. The plans cover all phases of the project and are supplemented with numerous standard detail sheets as well as an instruction manual. Hull building costs can be estimated beforehand by multiplying the weight of steel hull components by the cost per pound of steel in the local area. Study plans are available if further information is required.

Length overall:
Length waterline:
Hull draft:
3'-4 1/2"
17,100 lbs.
Weight of steel hull components:
7000 lbs.
Hull depth:
Freeboard forward:
Freeboard aft:
Height (with stack):
12'-7 1/2"
6'-2" to 6'-8"
Cockpit size:
3'-3" x 8'-5"
Fuel capacity:
350 gals.
Fresh water capacity:
250 gals.
Cruising range (at 7 knots):
1000+ miles
Sleeping accommodations:
Hull type:
Semi-displacement hard chine hull developed for sheet steel (10 ga.) construction with practical speeds to 8 1/2 knots.
Single diesel engine of 40 to 70 continuous shaft horsepower for 7 to 8 1/2 knot speed using appropriate reduction gear and propeller.
Can the hull be extended or shortened?:
Yes. Up to 10% by re-spacing the frames from the aft end of the stem to the transom a proportional amount. We do not recommend increasing the beam.