21' Racing Trailer Yacht
Boat Name: Stealth
The layout and set up is very simple. No winches, just
double purchase on the headsail halyard and sheets, with
two
Harken
ratchet blocks each side to take the spinnaker loads. The
main, no.2 and masthead asymmetrical spinnaker are all from
the
Boyd and McMaster
loft, with the no.1 and no.3 made in
Technora
cloth by
Doyles.
When first launched,
Stealth
had a semi-circular deck mounted vang, however
Smith
has now replaced it with a “49er” style
arrangement. This has reduced clutter and makes it easier
for the crew to scramble under the low boom when tacking or
gybing. The boom is very low to keep the centre of effort
as low as possible and reduce the heeling moment. The other
advantage of the vang system is that vang tension remains
the same no matter how the mainsheet is trimmed. With most
conventional systems, vang tension increases as the main is
eased and therefore requires constant adjustment to
maintain sail shape. The mainsheet is also a ratchet block
system attached to a full width traveller. All deck gear
is
Harken.
The hull was built in
Airex
foam, moulded over a temporary male mould and then glassed
in
E-glass
unidirectional cloth with
kevlar
reinforcing at stress points, frames and bulkheads. The
deck is a similar laminate but incorporates
Divinicell
rather than
Airex
foam. The laminate and lay-up were specified by
High Modulus
and are suitable for amateur or home building. So while it
is still high tech, it does not require vacuum bagging or
autoclave heating.
A professionally built boat using these techniques would
probably be slightly lighter, but
Dibley
estimates it would also add another $7-10,000 to the cost.
The rig is a
carbon fibre
mast designed by
Chris Mitchell
of
Applied Engineering.
The
carbon fibre
boom is from
C Tech.
The lightweight rig has a lower centre of gravity than
alloy, resulting in less pitching that slows boats down.
The resulting rig is light and flexible with the top
section almost self de-powering in gusty conditions.
Stealth is currently being sailed in Christchurch NZ,
by
Darryl and Leanne Pender
where they recently took out the
2003 Twilight Series.
Over-all results: 1st on line winning 6 out of the 7
races
SPECIFICATIONS
AND PRINCIPAL DIMENSIONS
LOA 6.500 m 21’ - 4”
LWL 6.000 m 19’ - 8”
Overall Beam 2.500 m 8’ - 1”
Draft 2.000 m 6’ - 6”
Displacement (1/2 load) 680 kg’s 1,500 lbs
J 2.300 m 7’ - 6”
I 8.100 m 26’ - 7”
P 9.300 m 30’ - 6”
E 3.000 m 9’ - 10”
Disp/Length 88
SA/disp 39
Review written for Boating New Zealand by Michael Cahill -
April 1999:
Wind conditions for a test sail were almost ideal - 15-20 knots south-westerly. With a crew of four we had adequate power and opted for the no.2 jib. We waited for the camera boat by the Westhaven breakwater, then hoisted the masthead asymmetrical kite for a reach down to Stanley Point. Stealth immediately lifted out and planed at 10-12 knots, light on the helm and under easy control. The spinnakers are set from a two metre long carbon fibre prod. The masthead kite was a little too full in the shoulders, but gave us an exhilarating and dry ride, easily outpacing the MRXs out for a Friday race. The kite was dropped and bundled down the companionway before we ran out of water and we settled down for a beat back to the Harbour Bridge.
With the breeze now at 20 knots the no.2 was right at the top end of its range. Smith has found that the boat has to be sailed flat, with the main constantly played to achieve this. If she gets any large degree of heel then the leeward wing starts to dig in and slow it down. Even with the main fully eased Stealth maintained an easy 5.7 - 6.0 knots to weather. There was almost no helm and she almost sailed herself upwind with little effort or fuss. The only complaints were from the older forward hands (this writer included), who had forgotten about the joys of hiking over the side dinghy style!
Back around the weather mark with the extra breeze we opted for the fractional kite, scavenged off one of Carl Smith’s 12 footers. Despite the reduced sail area, the heavier breeze and better sail shape resulted in an even faster ride, sitting on around 12 knots and peaking at 13 in flat water. Smith’s top speed so far has been 18knots. The whole performance was very dinghy-like, flat wake, fingertip control, wet and fun! The non Dibley designed rudder did have a noticeable hum and cavitation that will be fixed when it is replaced by a new foam carbon composite to Dibley’s design. This is a tapered teardrop shape with an almost pointed tip and a smaller chord than the existing ex-skiff rudder currently in use.
Overall Stealth has met both the designer’s and owner’s expectations. A fast, fun boat with all the modern go-fast gear at a relatively modest cost, around $32,000. Dibley also has a similar concept “750” currently sailing very successfully up North. This has a fixed keel rather than a centreboard but has a similar hull shape and ‘wingspan”. To date, she has collected as many guns as she has had starts.
Contact Dibley Marine
for more information