FPB Series

A New Paradigm for Cruising

Design Objectives

FPB 64

FPB 83

FPB 83 On Deck

FPB 83 Interior

FPB 83 Systems

Passages

How Things Are Working Out

Jury Rig

We've got very reliable engine(s), bullet proof transmission(s), prop shaft(s) which are way over strength, and good protection ahead of the propeller(s), yet we are still uncomfortable with total reliance on the machinery to get us home. We know that the odds are significantly in our favor with the reliability of our propulsion systems, but we want a bit of extra insurance. It is not the drive-line which worries us. What has made us uncomfortable is a scenario in which pick up a drift net, or bend the prop(s) so badly in a collision with a floating object that they are unusable. Maybe its all those thousands of miles of 100% self-sufficiency under sail, but we want to cruise knowing we can get home in the event of a catastrophic engine or drive line failure.

Boat Booms

You will recall that we have a pair of large boat booms on the after deck, rigged from our masts. These get the dinks on and off the deck, are used at anchor with flopper stoppers, and can be used at sea when we're slowed down in extreme weather as a paravane rig should our speed be too slow for the active stabilizers to keep us comfortable.

In the process of engineering the booms have gotten quite robust. They are heavy enough, in fact, to act as a mast in a reasonably efficient jury rig.

Taking those booms and topping them up almost vertical, we now have spot from which we can fly a get home sail. The booms are first lashed together, and then raised with their support pennants. There is a set of precut shrouds which provide side, forward, and backstay support. Playing with the system in Auckland, New Zealand, during sea trials with the FPB 83, we got the rigging process down to 30 minutes.

Sail Design

We live in a wonderful time for those of us who love boats and the sea. Gut instinct told us that we could move the FPB 83 pretty efficiently with a sail flown off this "mast". We can crank up our Fast Yacht VPP software, check drags, and develop a performance polar for the boat. The VPP data tells us we should be able to do 75 to 100 miles a day in moderate conditions, as long as we're not beating or running. But we don't know if the FastYacht software is smart enough to evaluate such a strange looking sail.

Enter the amazing tools which today's sail designers have at their disposal. Dan Neri was able to get us some time in the North Sails wind tunnel simulator with JB Braun. This is the same software used to develop America's Cup, Volvo, and other high end programs.

The image above shows a first pass at a sail configuration. This sail is about 68 square meters - 700 square feet.

Once we had the boat afloat we got the guys at North New Zealand on board to look at the real world. They had a couple of ideas, which made the sail easier to fly, and cleared the forward corner of the house (shown as an interference point in the 3D renderings). And here is the real world. In the final design we reduced sail area to about 580 square feet (56 square meters). This was done to make the seal less aggressive and easier for us to control. The sail is constructed from a Mylar/Spectra fabric of just 2 ounces per square yard. Very light stuff, but as it is used in the code zero headsails on very powerful ocean racers it should be more than adequate for our needs. North used "soft hanks" (made from rope) to attach the luff of the sail to our "headstay". The soft hanks reduce the risk of damaging our windows if the sail gets out of control. The sail does interfere with our with our navigation light mast, on top of the two wind masts. However, this has a hinge point and a single bolt holding it upright, so it is easy to lower the Nav light mast prior to raising the jury rig. Here is the view from the aft deck. Kelly Archer is playing with the sheet lead. You can see the red colored Spectra rope side shrouds. This sail is not going to take us anywhere fast. Speed (for once) is not the point here. What we are doing is creating a get home system for a worst case scenario. Realistically, it will probably never be used. But for a few thousand dollars, and the space of a small roll on suitcase, we have a lot of emotional insurance with this system for both the FPB 83 and FPB 64.