I took on the job of building a set of hulls for Kurts 28’ power cat design which we stretched to 31’ by adding about 2.5 inches to every station. We upped the stringer size by 30% and glassed with 8oz rather than 6oz but otherwise stuck with the plan and laminate schedule. We used multiple layers of 8 and 10oz to make up biax tapes, i find it makes for easier fairing and allows for tapering the buildup. We did a half-way-to-yacht quality fairing job, primed with 545 and installed cleats, hatches, fuel tanks, and fuel fills. There will be lightweight 25 hp engines mounted on rear transoms. We finished both hulls and shipped to the owner in maine, who is going to build the cross arms and center cockpit over the winter. I really can’t recommend committing to building a boat over the summer in sarasota, florida in a non-airconditioned space, but, in the spirit of running a marathon, and other ridiculously painful ways to enjoy yourself, we did it. Total build time, including purchasing, hardware, and mounting on a trailer for shipment, was in the neighborhood of a thousand hours. LOTS of pictures after the break-
Continue reading Building power cat hulls
Upgraded the video on this a bit: The layup on a 68′ cylinder molded hull currently under construction in Roatan: it’s speeded up quite a bit, this is about 25 minutes of real time. the half hull panels are approximately 11′ x 71′ – 4 layers of 3mm plywood and 33 gallons of epoxy.
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This office has been a leader in creating efficient, user friendly passenger ferries.
Most of the catamaran ferries that I see are designed by large design offices, and in my opinion, designed badly. They are usually metal, are heavy, have poor efficiency, and a poor ride, compared to what they could have. There are significant reasons for that. Those catamaran ferries come from offices who have been designing single hull ferries decades. They do cats now like they always did the monos.
I come from a sailing catamaran background. Instead of just piling on the horsepower, efficiency is important. I carry these lessons to the passenger cats that I design. I expect the gold plate design offices will figure this out in 5 years or so. That technology here now. For more discussion ofdisplacement power multihulls see this article.
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KHSD Charter multihulls emphasize functional, efficient design combined with longevity and durability. Many of these designs can use rapid construction technologies for hulls and house cabins.
If you could answer these questions and forward the answers to me to help start the design process.
- How long should be between charging batteries, once a day, twice a day, two days?
- Singlehanding needed?
- Shorttacking is fun
- The sole should be flat
- In light weather the boat should power if speed falls below 5 knots?
- Dining seats must be face to face?
- Galley should be out of traffic?
- Head area should be separate?
- All winches should be hand powered?
- Transom steps?
- Boat should be able to be beached?
- Kickup rudders?
- Shoal draft important?
- Unobstructed inside headroom is important
- Leangth of trips planned?
- Motor noise?
- Sea noise?
- Weight/cost tradeoffs
- Resale is important?
- Interior style? Old yacht-eurostyle-plastic boat style-mega yacht style
- Reefing gear type
- Frequency of anchoring intended
- Frequency of tacking and trimming intended
- Racing intended
- Helm should be covered from weather
- Good raingear is all that is needed
- Trimming quality verses helmstation comfort tradeoffs
- Most time under sail will be spent where?
- Most time at anchor will be spent where?
- Previous boats?
- Previous voyages?
- Previous races?
- How important is boatspeed?
- Boatspeed verses comfort tradeoffs
- Examples of best multi you have seen
- Examples of worst multi that you have seen
- Number of persons expected on most or typical voyages, and relationship of those people
- Most work will be upwind or downwind
- Rotating mast or not
- Fractional rig or not
- Fuel choice, why?
- Engine choice, why?
- How good should paint job be?
- Are there any other questions that i should have asked, but forgot to?