An Introduction to CONSTANT CAMBER
Constant Camber (CC) panels are essentially huge pieces of incredibly strong curved plywood that the boat builder makes in his shop on a curved mold. CC is a “monocoque” building method that uses inexpensive, low-quality wood to produce individual panels, which are then assembled end-for-end into a finished boat with attractive curved surfaces unlike the “flat” plywood we are used to.
Unlike conventional fiberglass boat molds, which can produce only one size, width, and shape of boat hull, and are no good if you want to change anything, an individual CC mold can produce a range of panels that can be used to build widely differing hulls within a certain length range.
(Below) A Constant Camber panel being lifted off a Constant Camber mold.
Full or partial length CC panels are laminated from veneer or plywood strips and glued with epoxy to produce a wide range of hull shapes and sizess from a single CC mold. Fast and economical production of panels is made possible by the fact that every single strip that goes into the mold is exactly the same shape! This is made possible because the mold has a constant curvature both side to side and end to end.
This is a tremendous time-saver for the boatbuilder, because he can cut an entire stack of strips at once from one pattern using a bandsaw, and not have to hand-cut each strip individually as was formerly required by “cold-molded” boat construction methods that produce very similarly-shaped boat hulls (AFTER you spend an eternity building the extremely complex framing underneath that’s necessary to install cold-molded planking on to).
(Below) A hull being “formed-up” from Constant Camber panels. The builder will connect the panels at the keel, then install a transom and internal bulkheads where necessary.
Invented and patented by Jim Brown, the almost single-handed creator of affordable and safe modern DIY cruising multihulls that can be backyard-built by their owners, the CC construction method offers these basic benefits:
- Economical; because CC panels are made from several layers of wood, and the individual wood strips are additive in strength, the quality of the wood used can be very low. This makes CC incredible affordable, as compared to wooden boatbuilding methods that use high-quality, super-expensive wood. When the glue sets up, you have a panel that’s incredibly strong, even though it was made from wood strips with knots, splits, and other defects in them.
- Monocoque construction; this simply means “the strength is in the skin”, instead of in the framing under the skin as in most boats. This is akin to the strength of an eggshell; although very light and flimsy, you cannot crush an egg with your bare hand.
- Simple, simple, simple: an eggshell is a very simple structure; and because all the strength is in the skin on a CC boat, it can also be a very simple structure. Instead of the complex maze of bulkheads, stringers, stiffeners, and other structural members inside many wooden boats, a CC boat only needs bulkheads where the crossarms connect to the hulls, and in other locations required to provide separation for privacy (think “a bathroom”), or for watertight bulkheads. And there is no need for stringers (lengthwise wooden strips) inside the boat for strength, so the inside of the boat is smooth, easy to clean, with no little pockets that catch dirt and junk.
- Economical and profitable for a small commercial boat building operation. Not only are the finished boats simple (see #2 above), you can build a range of boats from 16 feet up to 85 feet from only four or five CC molds, of different sizes and curvatures. Conventional boat building requires a mold for every single boat and boat part. This obviously costs the builder a ton of money, and makes it difficult for the boatbuilder to turn a profit.
(Below) A gorgeous little cruising trimaran made from Constant Camber panels: simple, economical, good-looking curvy, fast, unsinkable, and safe.
One of the biggest benefits of using the CC technology is that the many layers of wood multiply and build strength so quickly that the builder can use very low-quality lumber for the CC panels. Because CC panels are made from 4 to 6 layers of wood in total, this results in serious cost savings for the builder. And if you do want a really beautiful finish on the inside of the boat, simply substitute high-quality wood strips on the inner CC layer in that area, such as teak, mahogany, or Douglas Fir, then varnish it.
It also allows the builder to use low-quality lumber that would be impossible to use in conventional wooden boatbuilding. This is a benefit anywhere high-quality lumber goes for a premium, or isn’t available. And this breaks the mold as far as wooden boatbuilding goes, because “wooden boats” typically are built only from first-growth, vertical-grain lumber for their construction; the most expensive type of lumber there is!
(Below) Another gorgeous little daysailing trimaran made from Constant Camber panels.
Here’s the back story: Traditional wooden boats were typically built using lumber from straight-grain, old-growth trees; except most of those were cut down long ago. As a result, that kind of lumber is so rare now that the cost is astronomical! The result is that traditional wooden boats cost so much that almost none are built these days. As a solution to that problem, modern wooden boat builders started building their boats out of marine plywood, because it was available and quite strong.
Only marine plywood isn’t cheap either! It’s made of Honduras mahogany, Okoume from Africa, and other high-quality woods that are still quite dear. As a result, these boats cost less than wooden boats built with traditional techniques and wood from old-growth trees, but not a lot less! They’re still expensive!
So what’s the solution to this cost problem? Build wooden boats with CC panels, because the wood can be “Construction Grade #2”, which is the grade of wood normally used to frame wooden houses with. This is unheard of in the wooden boat community!
But there’s a huge benefit: making these boats more economical makes them more accessible to more people. That’s why we’re going to be using this technology for our 90-foot Serenity.