The Dinghy
You
know things are getting close to the end when we start making the final decision
on the dinghy. The actual process, however, started with the early concept discussions
on the FPB design. What sort of dinghy (or dinghies) to carry is always a part
of the initial layout for a new project. The smaller the boat, the harder the
tradeoffs. Yet for a serious cruising boat, the dink is a critically important
piece of gear. With the right dinghy, all sorts of opportunities are opened. Some
of our needs have changed with the march of time. Others remain the same. Amongst
the considerations are: - An
easy boat to get into and out of from the swim step, both for us while holding
young grand kids, for Steve's dad, who will be in his late 80s when this boat
is launched.
- A
reasonably smooth and dry ride in moderate chop.
- The
ability to push the mother ship around in very tight harbors on the odd occasion
when we cannot properly maneuver with our twin screws (maybe once a year).
- The
ability for one of us to set a kedge anchor when we go aground (still a certainty
even though our draft is down to five feet).
- Finally,
and this is the toughest - the ability to stay on the back of a medium sized wave
as we ride moderate sized surf ashore.
For
the past 20 years we've carried a combination of inflatable and fiberglass rowing
dinks. We almost went the inflatable route again. Had we done so, we'd have purchased
another AB inflatable aluminum-hulled RIB. We like the hull shape of these a lot
more than the fiberglass models (there's a lot more V-shape in the bow), and they
are quite a bit lighter than fiberglass. We had one of these on Beowulf. But RIBs
are a little skittish, especially when getting into or out of them, and they don't
do as well in a chop as heavier, more conventionally shaped hulls. One
of the big advantages of our new FPB design is her large aft deck. There is space
for up to a 15-foot (4.6m) dink on the starboard side and something substantially
larger on the port. We're reserving the port side for possible use by a sailing
dinghy, or combination of dinghies, and the starboard side is where the skiff
will reside. As you can see in the image below, the skiff fits between the engine
room access hatch aft and the main door into the saloon. 
There
will be two feet (60cm) of space between the bow and the coaming/door. The bow
rail on the dink will provide a good handhold at sea. Between this, and the rail
around the house, we'll be very secure when moving out of the saloon and forward
down the starboard side. 
Although
we dearly wanted to buy an off-the-shelf skiff, we could not find one that met
our needs (amongst which is the ability to bounce off rocks!). So we reluctantly
undertook the design of our own, to be built in aluminum plate by Circa. This
may sound funny, but after all the large yachts we've designed, we've never even
considered doing a dinghy. In this case the hull shape, and economics, called
for a "hard chine" shape that could easily be fabricated from aluminum
plate. We are indebted to Bruce Hays at Anteon Corp, who supplies most of our
software, for his assistance in doing a hard chine hull. 
The
hull shape tradeoffs in the dink are similar to what you find in a full-sized
yacht. We want a fine entry for slicing through the waves to keep us dry and comfortable.
But if the shape is too sharp, it will lock in on the wave faces when running
or riding a wave to the beach. A broach and capsize is the likely result! Above
is a first look at the hull shape. In this view it looks very V'd - in fact, so
sharp that your first impression would be that this would not be a good boat in
the surf. But
now look at the image below. 
Notice
how the forward section of the hull rises gently at first, and then more aggressively.
The knuckle of the bow is well clear of the waterline (especially if the crew
is all the way aft as they would be riding a wave to shore). This keeps the bow
from digging in. 
Above
is another view, this time abeam. We spent many hours discussing this design with
our old surfing buddy Mickey Munoz. Aside from being a hell of a good seaman,
Mickey is also a preeminent surfboard shaper (and has been for 40+ years). He
has ridden Mexican "Pangas" through shore breaks after many a day of
surfing. So when we started work on this design, Mickey was the first person we
called. Over the course of a week we probably talked a full day about bows, waves,
and how the the two of us could get the boat out of the backwash of the wave and
safely up the beach. The phone lines were humming with images going back and forth. A
mutual friend, Phil Edwards (another surfing and sailing guru) has designed a
series of small skiffs. Turns out Mickey had one of Phil's early boats on his
roof, and he had a tape measure. So if this boat works as well as we hope, Phil
and Mickey are due a lot of the credit. 
One
of the problems with taking a boat through the surf is getting water out of it
in a hurry. When (not if) you make a mistake, the odds are the boat will be heavily
laden with water. Bailing this out is never fast enough. What
we're doing to solve this problem is building in a double bottom - the same as
is done in surf rescue boats and modern sailing dinghies. This double bottom forms
a huge tank with the bottom of the hull, to provide ultimate floatation. The "sole"
level (or is it the deck level?) is 3" (75mm) above the loaded waterline,
so any water finding its way aboard will naturally flow back whence it came. 
In
the image above you can see two large drains through the transom. These will be
left open when we head to the beach. 
At
the forward end of the hull is a short deck. This serves three purposes. First,
when we have a dock that requires us to head bow-in, the deck gives us an easy
jumping off or boarding platform. The handrail is positioned to help keep our
balance when coming or going from the dock. Between this deck and the sole level
is a storage area for ground tackle, emergency supplies, and anything from shore
that needs to stay dry. The door into this area will be gasketed with a small
locking hasp. 
Another
feature of the bow is a welded pipe from side to side. This will be a towing point,
and allows us to insert a piece of aluminum pipe, which will act as a handle to
help dragging or lifting the bow up or down the beach. 
The
odds are we'll steer this boat most of the time standing up. Standing gives a
better view of traffic, keeps the drivers pants bottom drier, and allows the legs
to absorb shock when heading into chop. Notice the brace aft. The brace gives
us something to hang onto or lean against. In nice conditions only the "driver"
will use this. The passenger(s) will be on the middle seat. But in a chop, both
of us will be aft, standing against this brace. And
when the dinghy is lying across the swim step of the mother ship, the brace will
make getting into and out of the dinghy a lot easier. The
rub rail (an aluminum pipe) that wraps around the hull strengthens the edge of
the hull, and provides a soft edge for riding against rocks and pilings. The rail
curves back onto the transom, creating a tie-off point and another set of hand
holds for dragging up the beach. 
We've
yet to decide on outboard size. Odds are whatever the horsepower, it will be a
two-stroke engine made by Yamaha. Our 30HP Yamaha on Sundeer and Beowulf
lasted 17 years and was still going strong when we sold Beowulf. Size depends
on water skiing. If we decide we still want to ski, 30HP is what we'll end up
with. That's just enough to drag Steve up on a slalom - if he watches his balance
carefully and uses a large sized jumping ski. Otherwise it will probably be a
20HP motor. That's plenty to keep the boat moving at 20 or so knots, with enough
power to push the mother ship around if required. The
hull bottom is built from 4mm (3/16") plate while the deck, seats, and topsides
are 3mm (1/8"). There is an egg crate framework between the bottom and sole
comprised of three frames and three longitudinal supports. This vessel will definitely
be in the rock-crushing category. Weight
is always a tradeoff. While we want the boat as light as possible for performance
and ease of handling, it first has to survive the abuse to which we know it will
be subjected. The bare hull, with all its rails, seats, and lockers will come
in at about 368 pounds (167kg). This is more than twice the weight of our last
inflatable. But this boat is larger, more stable, and will last a lifetime. An
inflatable of the same length (15') would weigh almost the same. By
the time we add the outboard, gasoline, ground tackle, oars, life jackets, and
emergency gear we'll be pushing 600 pounds (272kg) before adding crew. In terms
of dragging the boat up the beach, the weight makes this impractical for the two
of us. That
leaves four possibilities. The first is to ride the back of the wave fast enough
onto a gently enough shelving beach that our momentum carries us up the beach.
The second approach is to mount a set of wheels just aft of the center of gravity
- between the middle and aft seats, and roll the boat up. Another system is to
roll the boat on fenders. And finally, what we've always done in the past - row
the fiberglass dink ashore. We're making provisions to be able to add wheels later,
but we'll start with the fenders. And then after we test this boat in New Zealand
we'll decide if we have to carry the lighter rowing dinghy for those occasions
when we need to drag the boat up from the water's edge.
| 
