I agree with your anaylsis Dave.
Here's a portion of a letter I wrote not too long ago:
Over the past few years I have been conceptionalizing a small RIB (Rigid
Inflatable Boat) tender for the use on cruising sail and power vessels, and
sportfishing vessels in particular. It would put emphasis on a number of
enhanced features that I do not believe are adequately addressed in the
current market. I had written in brief on two previous occasions:
I was searching for a short, wide, open-transom tender/dive/sport craft
that could be carried on the front deck of a gamefishing catamaran of my
design (preferable two such tenders). I was seeking a relatively small craft
that comfortable could carry 4/5 persons with some dive and/or dive/fishing
gear. Too many of the existing RIBs are too confining in their interior
space,
particularly with their big round tubes. I wanted two persons to be able to
sit on the tubes directly across from one another, and yet still have the
leg-room and passage room to clear a central straddle-seat that might house a
jet-ski type power plant. That would necessitate a fairly wide craft with a
central hull that could house the water-jet drive unit. A wide craft needing
a
central hull rules out the cat configuration. I could have a transom for its
structural contribution, but it needs to be 'open' to allow for immediate
evacuation of any water that might swamp it as a result of a large wave
washing over the bow stowage area of the mothership. With width I could
accommodate the people without excessive length, and thus keep the boat size
small and light-weight for the continuous hoisting service it will
experience.
You chose to build your own tender. I have one in mind myself. It would be
a RIB, possible with a foam collar rather than inflatable tubes. It would be
virtually transom-less, or at least maybe just a rigid frame at the transom.
The purpose being it would totally self-bail in an instant when subject to a
big wave, and particularly when stored on the bow as with many sportfish
vessels. It would be 'extra wide' for its length for increased capacity and
'across the aisle seating'. It would have a modified 'tri-hull' bottom akin
to
XXXXX for superior performance in a chop as opposed to shallow deadrise of a
very wide deep-vee. It would have a central saddle seat that would cover an
optional inboard jet-ski style engine in lieu of a traditional thief-prone
outboard (especially in third world)...
...also safer no-prop diving usage. Ultra light model in carbon fiber,
traditional model in stamped ABS.
I made a trip to the Miami boat show this Feb 06, and I was disappointed
again. As I look thru the market I'm not finding a RIB tender/sportboat that
could be carried on deck, or in davits, that is really 'self draining'. They
all appear as a captive 'tub', that if flooded by a random wave would become
a
very heavy 'big bucket' of heavy water hanging from the davits or sitting on
the foredeck. So I am seeking a virtually 'transom-less design', or at
minimum
a 'framed transom' that would allow for very quick water egress.
I also find most of the smaller RIBs to be very confining and tight on the
interior space as a result of the full diameter tubes utilized in their
design. The actual width of the boats between the innermost tube sides is
very
confining with respect to allowing for two full size adults to sit across
from
one another, let alone a steering console, cooler etc. Then if you add in all
of the 'stylized' seats for passengers, center console for driver, engine
mountings and drains, etc, etc, you end up with very little interior volume
to
carry people, dive equip, etc, and all of those other items (food, supplies,
bikes, etc) being transported to and from the shore.
Remember, in the islands your tender becomes your car!!
One solution to increasing the onboard space of any RIB is to make use of
only
'half-round' or 'D-shaped' buoyancy tubes at the beam extremities of the
craft. This idea is at the core of the 'SAFE' system (I've attached a
reference drawing). These 'tubes' might be constructed of either an
inflatable material as normal for the current industry, or simply be a foam
collar that might be glued on, or a combination of both.
Another solution to increasing the onboard space of the smaller RIBs is to
make them wider....exaggerated wide. One manufacturer currently refers to
this
as his "wide body" models. The problem here is the deadrise angles at the
bottom surface of the hulls become pretty small, or as it might be termed
more
'flat-bottomed' rather than V'd. This results in a vessel that slaps or
pounds
more on the water surface, particularly a choppy one. And this flat bottom
loses it directional preferences (control).
My design reconfigures the bottom of the RIB into a sort of tri-hull
arrangement. This totally changes the shallow deadrise equation of the main
hull, and provides two 'channels' that allow for a sort of air suspension
within them. The outer rib keels, or what might be termed sponsons of the
tri-hull configuration, act to contain the channels themselves, provide
additional buoyancy at the extreme beams of the vessel, and provide a turning
edge much like the tunnel sides of the older tunnel-hulled craft. These outer
sponsons do not extend forward to the bow area of the craft, which might be
confused with being similar to the old 'cathedral hull' that was so poor
about
pounding in choppy waters. It's totally different. The more 'convoluted
bottom
shape' of the design will lend 'form strength' to the bottom surface, as well
as longitudinal rigidity to the whole vessel, allowing for a lighter
fiberglass lay-up to achieve proper strength than is the case with the large
flat-panel areas of the traditional V-bottomed hull.
This could be a fun little hi-perf powerboat project with lots of commercial
market potential, costing a relatively small amount in development money, and
probably sellable to another RIB manufacturer at any point along the
development path, either domestic, European, or Asian....if someone's
interested
------ Original Message ------
Received: Mon, 01 Jan 2007 02:09:34 PM EST
From: "Dave Cooper" swansong@gmn-usa.com
To: "'Passagemaking Under Power List'"
passagemaking-under-power@lists.samurai.com
Subject: Re: [PUP] What you look for in a dingy?
Scott et al, Your dinghy is your SUV once you've cut the docklines.
Anchoring out isn't always close to where you'd like to be or in calm
waters. A 10 mile trip to get some provisions or a part can be a bad
experience in a small dinghy or a cake walk in a larger on. We have gone
from 10' to 11' to 13' to our present 14' 8". It would be very tough to go
backwards! We have the range and the freeboard to run in some pretty tough
water and get there and back in a short time. Often there are others
wanting
to bum a ride as their dinghy can't handle the situation.
Where we are in currently is 5 miles from the supermarket. It is in
sheltered waters but still we run outside and get there and back in 15
minutes with 4-5 people aboard, aka hitch hikers, and we return with a ton
of groceries for all. This is not an atypical usage.
Taking 6 to 8 people off to snorkel a reef several miles away...another
good
use. There's only Nancy and I but as soon as we get the hock down Nancy has
organized something for everyone in the anchorage. Perhaps this is why I
try
to anchor in the lonely places with no other boats ;-)
We have anchored in open roadsteads with a 3-5' sea running onto a lee
shore....not a pleasant place and not something we planned on but a 180
degree wind shift of the tradewinds. Going ashore and working with other
boaters was not a worry with our large dinghy. Others could not even get
into or in some cases launch there small dinghies.
We are having a tube cover made here with a heavy push pad built in to the
bow. This will add both sun protection, abrasion resistance and give us a
little better bow protection when we are suddenly called to be a tug boat.
So big is better IMHO, we tow it, have a larger motor (60HP 4 stroke),
carry
plenty of fuel for it and it has its own VHF with DSC, depth sounder, chart
plotter, GPS, LED running lights, spotlight, flood lights and radar
reflector. A tender not a dinghy is a better name for it I guess.
We see so many folks come to the Caribbean over the years with a 10' or so
roll-up or RIB and within a few months they have traded up to a 12' or
larger. Its lots cheaper to do this in the US than in some island where you
finally decide to bite the bullet. Unless of course you are in Venezuela
where they make the AB Inflatable line....very good prices compared to the
states ;-)
No matter what you get you need a chain to lock it up. Cables are cut with
impunity in most places. A minimum of 5/16 SS chain with 3/8" SS better,
about 25' long will do nicely. Also the OB needs to be thru bolted to the
dinghy or it will be gone. Those various OB locks rust so quickly in the
warm Caribbean seas!
Remember that your dinghy/tender let unlocked is way to much of a
temptation. In many areas its fenced value will exceed the yearly income or
more of a worker. You wouldn't leave a Lexus SUV parked with the windows
open, doors unlocked and the keys in it in most places so don't do it with
your dinghy.
As always, YMMV
Cheers
Dave & Nancy
Swan Song
Roughwater 58
Puerto La Cruz
Venezuela
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