Dual Width Boat Design

[Al Tyler]

My Problem Like many trailer boat owners is that I need a wider boat, but because of width restrictions on trailering this is not an option. It occurred to me that what I needed was a Dual Width boat, a boat with a wide hull that can be easily reconfigured to a narrow hull that meets legal towing limits. with a Dual width design I could have all the features of a narrow hull, a softer ride, the flexibility to move the boat easily by trailer, lower gas consumption when high-speed cruising, and the economy of not having to pay the high slip and maintenance fees required to keep a wide boat in the water. I could motor to my destination in the narrow configuration, then rotate the extended side hulls out and have the advantages of a wide hull, a larger cabin, walking clearance, extra room for fishing, and better stability in the water.

I did a search and was disappointed to find that no one builds such a boat today. My search of patent applications revealed that, although many attempts have been made to design dual width or expanding boats, they all appeared to be too complicated, too expensive, or not rugged enough to be practical. Unfortunately, if I wanted a boat like this I would have to design it myself. I have many years of industrial design experience to draw on, so I decided to give it a try. To make such a boat practical, the boat would have to be manufacturable at a reasonable cost, be easy for a single operator to change configurations, and be simple and corrosion resistant for minimal maintenance. However, the most important requirements are that it must be safe, never leak, stand up to rough seas, and be at least as strong and rugged as a conventional boat. The design process took awhile but I did come up with what I believe is an elegant and simple design solution that meets all the above requirements. Not only did the design satisfy my fantasies about the perfect boat, but also it appeared that it might have commercial possibilities.

The first attached drawing shows how the design increases and decreases the boat width by rotating sealed side hull extensions that are hinged near their center of balance, so they can be easily rotate by one person, Or they can be rotated with electric motors and locked in place with solenoid pins.
Figure 1 shows the hull extensions rotated in to narrow the hull width. In this position they are secured to the hull with pins at the front and back of the boat.
Figure 2 shows the hull extensions rotated out to widen the hull width. In this position they are secured to the hull with six flush mounted deck latches.
Figure 3 Is an exploded drawing illustrating the sealed boat hull and the sealed side hull extensions that make the Dual Width boat possible.
To make the boat virtually unsinkable, the hull design uses a self-flushing sealed deck located above the water line. This is an extremely rugged hull with very little flex. When extended, the side hulls are supported their full length by being seated into a solid groove against a pliable seal strip on the hull sides, so there is no direct force applied against the pivot hinges and latches from the water at high speeds or rough seas. The pliable seal strip prevents water splashing, and also eliminates any vibration or noise from that area. A further benefit of the side hulls is that they are sealed chambers that add additional buoyancy and impact protection. The three additional attached drawings are views of my idea of the perfect dual width fishing catamaran, 26 feet long by 11 feet wide (8 ½ wide in the narrow configuration). With a 12 foot long by 6 foot wide cabin. For more information go to http://www.dualwidth.com or contact me at dualwidth@verizon.net .

Presently I am retired and not interested in financing a prototype or starting a new business, but I would like to see the concept developed. If there is someone that would be interested in building a prototype, or is interested in expanding their business consider the advantages of the design:

•The Dual Width design could create trailer legal boats that are more stable in the water, and have more usable width than competitors can offer.
•The Dual Width design could create wide boats that can be narrowed for a softer ride, higher speed, better fuel economy, and trailer compatibility.
•The Dual Width design could be manufactured at very little additional cost over a standard comparably wide boat.
•The potential market could be enormous, including many different types of boats.
•This new market would not be limited to a local area. The narrow 8½' hull width allows economical shipping by truck or container.

[tspeer]

Originally Posted by Al Tyler

...what I needed was a Dual Width boat, a boat with a wide hull that can be easily reconfigured to a narrow hull that meets legal towing limits...
I did a search and was disappointed to find that no one builds such a boat today. ...

Au contraire. There is a very successful line of variable-width boats for just the reason you state. These reduce from as much as 23 ft in beam to a legal 8.5 ft in beam, and do it on the water in only a couple of minutes. These are trimarans designed by Ian Farrier and built by Corsair Marine. Here's an illustration of the Farrier system:


There are other systems that have been devised for catamarans, including hulls that fold under a central bridge deck (Derek Kelsall), beams that hinge in the middle to allow the boat to collapse together like an A-frame, telescoping beams (Kurt Hughes), and beams that pivot to swing the outer hulls inboard (Quorning's Dragonfly line of trimarans).

Kelsall's method is the one most similar to yours:

He also incorporates tires in the hull topsides so the boat becomes its own trailer, too.

[Al Tyler]

Thanks for your reply. I was aware of the designs you pointed out. There are also similar ideas for pontoon boats. The advantages of the Dualwidth design is that it can be applied to conventional boats to not only improve stability in the water, but to increase usable deck area. I have attached both an animation that show a mono-hull center console fishing boat that is converting from 8 1/2 feet wide to 12 feet wide, and drawings of another mono-hull fishing boat with a cabin. I was hoping to get some inputs and comments on the details of my design, what are your thoughts?