SeaRaider Design PDF Print E-mail
SeaRaider Boat Sailing
SeaRaider was Launched Easter Weekend 2006
 In the Spring of 2005, we were building a pair of Storm 19’s when we received a visit from an experienced raid skipper who had been following their progress on our website. Although he liked the design, it became apparent he was really after something bigger. Something withroom for 4 oarsmen and real power under sail, but crucially it had to be comfortable and safe single handing.
Length: 21ft 10ins (6.65m) Beam: 5ft 11ins (1.8m) Weight: 715 lbs (325kg)

Even the most competitive of Raiders are unlikely to do more than a few events a year, so for the rest of the time the boat should be capable of safe coastal passage making without too many heart-in-the-mouth moments.

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SeaRaider
From a very early stage in the design process we were convinced that water ballast was the only way to satisfy the conflicting requirements of rowing and short handed sailing. By creating a false floor to the cockpit, we were able to take on 300kg (660lbs) of water ballast. That is four EU adults lying in the bilges, which greatly increases the stability, and crucially, the self righting capability. When sailing single handed – flood the tanks. When rowing or racing, pump them dry. For simplicity, we decided to have one tank, so it must be either completely full or completely empty (to avoid water sloshing around). However, inflatable crewsaver bouyancy bags could be used in the tank in order to half fill them if desired.
Sail plan
Side Profile/sail plan
The false floor is sited just above the designed (full displacement) waterline, and inclined aft slightly. Opening a large twist hatch in the aft bulkhead allows any significant water in the cockpit (after capsize say) to flood out via the outboard well. This is effectively a self draining cockpit and should increase her seaworthiness and the confidence of her owner considerably. Gratifyingly, she is self righting with the tanks full just as our calculations predicted. Since she is over 6m long, different rules apply in the determination of RCD category, but the ability to be righted by the minimum number of crew (1 person) remains vital. She will be Category C.
Lines
SeaRaider Lines

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The wide transom gives an easy run to her lines
Her hull bears some resemblance to a classic racing dinghy of the 60’s, a very long thin shape with a flat clean run aft. She will plane in the right conditions with tanks empty and a 3-4 man crew. The width of the transom has been cut down from that originally drawn so as to improve her rowing performance (reduce wetted surface drag). Under oar, a pair of rowers sit side by side on each removable thwart and we recommend that the heavier pair sit on the forward seats, the more to lift her stern out of the water. We were reluctant to add a full length deadwood keel fin as this would again cause drag and she manages perfectly under pars with the board down a little.

Image
SeaRaider in Build in Our Workshops
Another requirement was that as far as possible the boat was to be aimed at the commercial market. Provision for an outboard engine was essential (up to 5hp short shaft) and her design was to favour sailing capabilities over rowing. Hence her very firm turn of bilge giving form stability and flat run aft for speed.

We have drawn her with a ketch rig (though this is not set in stone) which has the usual problems of tiller/mizzen confrontation. We have decided to go for a slave tiller mounted near the mizzen with a yoke and wires running either side of the outboard, under the aft deck. The huge advantage of the mizzen however is the wide variety of sail shortening options available to the short handed or overpoered crew. She was designed to maintain great performance under jib and mizzen which are big enough to provide real drive and speed to windward.

The outboard was brought forward into the boat, rather than hung from the transom, as it keeps the weight nearer where you want it and helps keep the prop submerged. The hole in the hull is closed with a fairing flap.

The boat is built from 6mm plywood in a three plank per side, monocoque stitch and glue configuration, sheathed inside and out with glass cloth set in West System. The plywood is light for the weight of the boat but apart from the bottom (which is hugely reinforced with glass) the panels are relatively narrow and so are adequately strong. The main structural feature is the long box section “gunwale” that runs from bow to stern bulkheads providing two functions

  • Torsional rigidity to the cockpit area

  • Buoyancy/dry stowage in the event of capsize.

The water ballast tank runs almost the full length and breadth of the cockpit. Preservation in such tank is important. Glass cloth set in epoxy is used for the tank bottom and a foam core ply/glass sandwich for the top. In extremis the whole tank top can be removed.


You can see photos of the first SeaRaider in build here.

If you would like more information on the SeaRaider please fill in the form on the SeaRaider home page.
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