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Design 177 – Sea Hawk 21
6.5m Island Hopper

Optional Downwind Rig
Click for: Standard Version

Standard Plans Download: $135.00
DXF files for CNC are here
Other Drawings (With Downwind Rig):

Gen. Arr. (with Magnify Tool).
Interior Plan & Profile.
Frames & Transom.
Outboard Profile.
Typical Frame & CNC Drawing.

LOA (with swim platform) 6.900 m 22' 8⅛"
LoD 6.500 m 21' 4"
LWL 6.000 m 19' 8¼"
Beam 2.430 m 7' 11¾"
Draft 0.550 m 1' 9½"
Headroom in saloon 1.400 m 4' 7⅛"
Displacement on dwl 1650 kg 3,638 lbs
Outboard Engine 7 to 11 kw 10 to 15 hp
Cruising Speed 2.56 m/s 5.0 knots
Spritsail 9.5 m² 102 ft²
Leg o' mutton sail 6.25 m² 67 ft²
EU Category C - Inshore
The Sea Hawk 21 Island Hopper is designed for the most straightforward construction in ply and epoxy. She is especially suitable for CNC cut parts, but all the data (including the shapes of developed surfaces such as the hull planks) is provided for builders to mark out and cut their own parts. No laying off (lofting) or spiling (taking shapes from the hull) is required.

As her name suggests she is basically intended for short sea trips, though of course she is equally suitable for coastal, estuary and lake cruising.

She has a round-bilge displacement hull with a cruising speed of 5 knots (5.75 mph; 9.26 kph). Top speed with, say, a 10 to 15 hp outboard, will be about 6 knots (7 mph; 11 kph).

The hull is designed for simple lapstrake construction – a fairly narrow flat bottom strake with five hull strakes and a coachroof strake. The six frames are made from three layers of ply and the outer edges are shaped exactly so that the strakes will fit directly to them. The outer edges are also made the correct size for their position which results in a stepped bevel; the little steps are filled with thickened epoxy as you fit the skin, thus avoiding the need to bevel the frame edges after assembly.

The CNC frame components also incorporate bulkhead sections, together with bearers for the berth base, cockpit sole, cockpit seats etc., as appropriate – so completing the rest of the boat is made as straightforward as possible – truly pretty much just an assembly job. The backbone and most other components can also be CNC cut from ply and bonded together just like the frames.

The hull planks or strakes can be CNC cut to fit directly on to the frames and backbone, set up in the building jig. No bevelling of the plank edges is required: the plank laps are filled with a thickened epoxy fillet while the hull is still upside down.

177 Sea Hawk 21

The accommodation comprises of two V-berths forward, with stowage and drawers beneath. Then aft of those to starboard is a space for a marine toilet or a port-potti type toilet, and a hanging locker. To port is a small galley with a two-burner and grill stove and a sink, with lockers beneath the worktop and outboard; a flip-down seat is provided for comfort working in the galley.

On deck the large self-draining cockpit has comfortable seating and can be provided with a good-sized cockpit table. The space under the seats is open so that fishing rods and other long items of equipment can be easily stowed. The cockpit can be shaded from the sun (or indeed the rain) with the bimini, which folds down on to the top of the shallow windscreen when not needed. Small swim platforms are provided at the transom. There is a second steering position to starboard, with good visibility forward when standing or sitting; if this is not required, the cockpit seats simply continue to the bulkhead as for the port side. The uncluttered full-width coachroof deck makes a great place to sunbathe.

The outboard sits in a well in the cockpit, completely enclosed under the aft deck, which makes it both secure and less vulnerable to waves and spray. Access for servicing and removable is by a deck hatch. Space for remote fuel tanks is provided either side of the well, under the aft deck. Fresh water tanks are located under the cockpit sole.

With the optional downwind rig the vessel will run and broad reach – she's not designed go to windward! This is both for pleasure, to blow gently and quietly along on a fine day – or to get you to a harbour should the outboard fail. Two rigs are shown – a spritsail which gives 9.5m² (102 ft²) area or a "Leg of Mutton style sail (just dotted in on the drawing) which gives 6.25m² (67 ft²) area. The mast is shown as keel-stepped unstayed, but could equally well be deck-stepped, supported by three simple rope stays. One advantage of a deck-stepped mast is that it will be lighter and shorter, so easier to stow if removed – it could be sleeved in two pieces, so that it would stow down below when required.

The detailed and accurate plans together with true step-by-step building instructions carry builders, professional and non-professional alike, through the building process simply and easily. And for larger boats particularly, they allow a managed build to be carried out very successfully. Plans are fully dimensioned; no scaling or lofting is required. The plans and instructions are practical, clear and detailed, containing everything required to build and complete the vessel. Where CNC cutting files are included, or available, they can be sent directly to a CNC facility as required. Professional technical support throughout the build, is available by email, via the forum or by regular mail. More plan info

The Standard Plan Package below includes all the plans and instructions to build and complete the boat, with all the data necessary to mark out and cut the CNC plywood parts by hand. If you purchase some or all of the CNC Packs, you will still need these plans and instructions. You will find the CNC Packs here

Click here to look at the free study plans and a list of the plans and instructions that are currently available. The first of these boats is in build at the moment (August 2018).