Dreamboats
by Jeff Gilbert


Gumboots -In blue or hot water?
by Jeff Gilbert

I’m currently doing the final build plans for Gumboots, a simplified 31foot dory derived catamaran. A gentleman named Bob Sacher asked me about her offshore capability, specifically in Alaska, the Horn and other inhospitable spots. I was glad of the question, and here is the substance of the reply:

Gumboots prime aim is simplicity (hence speed) of build with the proviso that it must be UTTERLY SEAWORTHY.

Hence much of the design is based on the question: What can & cant we do without? We cant do without a certain amount of hard work in the way of:

  • 3 main bits: -two hulls and a main beam
  • 4 lesser bits: 2 simple beams and 2 boards.

I however reckon she can be built in 1200 hours. That’s 4 months full time for two people. The main cost is 78 sheets of quality marine ply.

Gumboots is a true offshore boat designed for ocean travel at a good clip despite a good hammering, with a reliable program producing predicted passage times are 220nm per 24 hours in good 20knot winds.

In brief,
we dispense with the bridgedeck accommodation, and replace it with low slung sail, so that the windage that blows you off course is transferred to sail power and the waves that try to topple you go thru the boat.

Gumboots deliberately sacrifices accomodation space for offshore safety and seakeeping ability, but she is however comfortable as long as you think in camping/minimalist way and don’t take a crowd on passage. You can take 12 people day sailing, but I wouldn't cruise with more than 3 adults or 2 adults/2 kids.

You can stand to cook, sit in a comfy armchair and sleep in a comfy bed.

You can ablute without making the boat uninhabitable, a massive attraction. Offshore boats with dunnies in the middle are all wrong IMHO. People ARE sensitive, and are embarrassed. On Gumboots you can even change tacks so that a sensitive crew member can use the toilet opposite and behind your sailing position, close the hatch and open
the port and there you go.

In detail, note the following:

  • Unlike most multis you sit in, not perched on, the boat - the cockpits are deep and safe with a 4 foot wall in front of you affording full visibility while protecting the bulk of your body. Full dodgers are a possibility, but I don’t like looking thru glass or plastic other than sunglasses occasionally. . The cockpits are deep but still self-draining, and directly steal potential internal space.
  • There are no companionways to fill the cabins with water. You can talk to the cook thru an opening port in the rear cabin wall.
  • The bridgedeck should be mostly slatted letting storm waves thru the boat.
  • The centre of effort is low 20 ft ASL -the raked mast and angled boom mean that the boom still clears your head on the odd occasions you are not close hauled. You can put nearly 40 horsepower into the boat thru the sails before you have to reef at 27 knots wind speed, or at least 14kts boat speed.
  • The beam down the CL means you can rig her any way you want. For single-handing you could rig her as a schooner or ketch breaking up your sail area into small chunks. Id also use double the standard 3 wire standing rig - its only 3 lines - spectra rig her and double lines. Safety plus.
  • For really heavy weather sailing one can make provision for water ballast OR carry a lot of drinking water, 200 gallons or so, filling up equally under berths and cockpits for trim whilst retaining headroom areas. Loading the boat to 3 tons wont worry her, it will just mean more sail carrying power.
  • A powerful outboard fully protected in a central box behind the rear beam will give you the ability to outrun most weather patterns if you cant outsail them. You could even make her a super motorsailor -use a Honda 90, with a 13inch prop -this will cruise at 3600rpm & 46HP at 2 imperial gallons per hour, the most economic outboard ever (all the motor development of the Honda Civic car lies in this engine) and send a fully loaded Gumboots along 17knots or 8.5nm per imp gallon (6.7 US) with a top speed of 23knots. Personally for serious cruising I'd look at
    • The Yanmar 27 diesel outboard - this will give 10knots @ a US gallon per hour, or
    • a 4-stroke Honda 30 (cruise 10kts, max 14)
    • or direct injection 2 stroke which give the same economy as the 4stroke without having to bother with oil changes.
    • and carrying a spare 6HP in the head (they now weigh 25kg and will give 6 knots on the main boat while powering a riubber duck which can lash on half the fore-tramp area.)
  • If you are taking heavy breaking beam seas, you can raise the lee dagger a bit and sideslip instead of flipping. The flat-bottomed touring cat Fallado survived a beam hammering around the Horn in this manner. If you dont have the searoom to lose this sort of leeway, start the motor and make some.
  • Hove to against a sea anchor theres not much for the sea to grab (see section)

I would hesitate to take any sailboat around Cape Horn.
Discretion is the greater part of valour.

On the other hand I would not hesitate to sail Gumboots anywhere. It is primarily designed for a gent who intends taking with his wife around the Pacific.

Were I taking Gumboots to Alaska/ice areas Id build her of 12mm ply instead of 9mm., and foam the first 3 feet or so to a crash bulkhead. The extra 400lbs wont worry her and the gains in insulation would be worth
it.

In Gumboots I have attempted to retain the ease of build and proven safeties of the Polynesian style, while upgrading the accomodations to provide standing headroom to cook and put your jeans on. Many good cats are butchered above the sheerline in taking this too far. .

A navigation cuddy with a cockpit behind and full length hull accoms was rejected equally because

  1. It raises the centre of effort of the sail plan 3 feet and thus lessens sail carrying ability massively.
  2. It raises build time.
  3. It raises windage.
  4. we have one in a rear cabin, and a toilet in the other.

I hope 2004 is a good year for all.

Jeff Gilbert