This article is as printed in Sailing New Zealand magazine November
2000.
VIRTUAL JAVELIN - ARTICLE
VII
The old 80/20 rule definitely holds true in yacht construction.
We managed to do 80% of the job by building three hulls and decks
in a little over 4 weeks, the final 20% of each boat seems to
take forever…
Attaching the Decks
To reduce the frontal area of the hull above the water, the topsides
have been made closer to vertical than is normal in the class.
The desired effect of this is to reduce the wave drag encountered
when sailing upwind in choppy conditions. A conflicting aim was
to make the boat as wide as the rules allow at deck level to
give maximum righting moment to the crew while trapezing. The
solution to this problem was to add small "gunnale wings"
extending about 120mm from the sheer to bring the hull to maximum
width. The gunnales were moulded as part of the hull shell, and
are 20mm thick in a very light 60kg/m3 foam. On top of this the
10mm deck has been added that is made from a more resilient 80kg/m3
foam. The joint between the decks and hull is a pretty simple
one; just mix up a heap of epoxy glue, stick it down the gunnale
and then sit the deck on top, clamp it in place (heaps of clamps),
remove the excess glue, wait overnight and you're done. When
joined together the gunnales are 30mm thick and definitely strong
enough to take the weight of a 100kg crew bouncing down the sides.
The exposed foam edges were then rounded off with a router, and
covered in two layers of 400g double bias cloth. We reckon this
will be grunty enough, however the proof will be if we can survive
a 40 boat startline in a fresh Wellington southerly.
Transom and Rudder
Fittings
The transom was constructed with a lightweight 60g foam with
a piece of thin walled "paddle tube" glued on top.
The top 100mm of my garage broom was sacrificed and ended up
being glued into the middle of the tube where the top gudgeon
is bolted through. A compression strut was taken from the top
gudgeon to the false floor to take the forward load from the
rudder. The bottom gudgeon was a bit more a problem. We didn't
want to cut any holes in the false floor, so were not able to
through bolt through the transom. The solution was to glue a
pre-bolted plywood insert into the transom with the bolt heads
glued in place and then add a couple of layers of carbon to hold
it all together. The mainsheet bridle for stern sheeting is attached
to a strengthened area of the transom inside the deck line to
allow the skipped to get right to the back of the boat to help
hold the nose up.
Mast
This is a bit of a diversion from the original plan, in this
boat we are deck-stepping the mast rather than sitting it on
the false floor. Current skiff rig designs are based around the
concept of locking the rig in place from the hounds down, and
using a more flexible topmast to automatically depower in the
gusts. This new mast is being designed with long spreaders, D1
stays to the spreader base, and check stays to the gooseneck
instead of a mast ram. Deck stepping the mast places ½
metre of mast weight into the measured hull weight reducing overall
sailing weight, but more importantly it reduces the amount of
section down low that can bend. The mast is stepped at deck height
on top of a 600mm stump made of an old broken mast tube which
has been glued into the main bulkhead.
The spar itself will be from Tim Willetts masts. Tim has developed a mast suited to my style of sailing, which is for a maximum of automatic response from the rig, with limited on the water adjustment required. This mast is a contrast to the other new Willetts Javelin section this season being used by Geoff Wilding and ex National champion Craig Gilberd. In this double spreader section everything is adjustable from inside the boat, including an additional set of check stays to the masthead. Both these masts are incredibly light, and will weigh in at around 4.5kg for a 7.5m long section. Tim himself has recently got back into Javelins and is developing a more radical deck stepped over-rotating mini wing section.
Sails
Whilst the top three boats at last seasons nationals all used
sails from different sailmakers we felt that there was only one
choice. Ken Fyfe of Fyfe Sails makes really fast skiffs sails,
has many years of experience, will always work with new ideas
and can help tune up the boat. In our case we are developing
a boat that want to be able to drive fast in the higher wind
ranges. To do this we have reduced our mast height by around
200mm to lower the centre of effort (and boom height), and will
be getting a mainsail sail designed with a slightly longer foot
length giving a lower aspect ratio than is the current trend
in the class. We hope this will give us less drag, less heel
moment and more forward drive, and should also reduce the tendency
of this fine hull to nosedive when pushed hard. The gennaker
is a pretty simple choice, with windward/leeward courses becoming
predominant the sail is cut bigger and optimised for running
deep.
Running Rigging
Many of the systems in this boat are configured similarly to
my current hull. Running rigging runs around the cockpit, not
though the middle, which keep things clear for tacking and gybing.
We have removed the central mainsheet bridle to further open
up the centre of the boat and allow crew movements in light weather
to be subtler without having to work around the mainsheet. The
mainsheet itself will run from the transom into the boom, where
it will have a 2:1 purchase before exiting at the mast. Through
a ratchet block on the floor and then into a tube/foot stop on
the floor back to the centre of the boat. The gennaker halyard
also runs through a tube to the centre of the boat. On a false
floored boat in particular there is always a tendency to step
on lines at the wrong time, putting them in a tube is a little
bit of insurance to make this impossible. The gennaker sheets
are run under the decks (so the skipper can't sit on them) and
back through an exit sheave in the side decks. Lots of advantages
here, but basically, in a messy gybe you can only grab the correct
end of the sheet as the other is outside the hull.
Hitting the Water
All going to plan the mast will have been stepped over Labour
Weekend, we will finally choosen a sexy paint colour and will
be sailing before you read this…