The object: Build a multihull in the most cost effective manner, easily able to be replicated by inexperienced builders at the F-48/Mini40 scale size.
Econo-maran POST #1
With the holidays over and daughter firmly moved and planted in her new home, thoughts are again turning toward the potential to try a building method incorporating flat slab sides and a curved deck and hull bottom of composite material construction.
To start, I found an interesting build process for a large (and subsequently) inexpensive full size trimaran. I have decided to try the process in the r/c size format. As you may recall from a previous post, the full size boat has slab sides of plywood, and the company furnishes a “pan” or bottom hull fiberglass laid up shape that bonds to the bottom of the slab sides, providing rocker fore/aft and curved underwater sections cross beam. The full size boat uses plywood for a fairly flat deck, but I am thinking of providing a similar “pan” for the curved top deck to help shed water should the deck be forced under. In both cases of these “pans” - I will use extruded household insulation foam to provide a material that can be easily shaped. I suppose, one could lay up balsa strips, but that is tedious and time consuming, and the foam, covered with glass is both cost effective and easy to do for a beginning home builder. Later, if it warrants and easy mould can be made for pure glass hull bottoms and decks - doing away with the added glass weight.
I have attached two photos that represent the start of the project. More photos to come as I move forward with the build. I am starting the project with four pieces of balsa sheet, 48 inches long and 1/8 inch thick. These will make up the two hulls for my proposed Econo-maran. To keep costs down, and make the process easy to construct, I am going ahead with a catamaran design, which is only two hulls to be built - not three. I also will use a piece of 1/4 inch thick balsa for my bulkheads and stations where the shape of the hulls will be derived. The balsa only cost was (gulp) an unexpected $20.00 (US) from a local hobby shop. Next time I will mail order and receive double the number of sheets. Lesson learned. The foam was picked up with approval from a local home building site as a discard. It happens to be 2 inches thick - I think 1 inch thick would work, and will probably cut this down to prevent waste.
The hull you see in the background is one of two resurrected from a first attempt at an F-48 catamaran that was scaled from my real cat. Unfortunately as I began to build it (circa 1998 - 1999), I found there are issues in trying to make a cat “look” good, and still house the radio gear equally balanced in port and starboard hull. Will have to rethink, as I hate the look of a big box sitting under the mainsail housing the radio gear. Since this is a test of a new building process, I will forge ahead and deal with radio control later. I will use the old hull dimensions with modifications to come up with a more modern catamaran design. Hopefully something like the full size Formula/Inter 17 catamaran hulls will emerge. When done, I expect the final platform to be about 48 inches long by about 32 - 38 inches wide. Not sure at this moment if I will use a separate daggerboard in each hull and separate rudders, or center mount the daggerboard and only one center located rudder. Likewise, the rig/sail may come from an existing 36/600 or 1 meter for starters. Can always increase sail area later.
As I move forward, I will try to provide photos as the build progresses. I intend to keep track of total build time if possible to allow others considering the process an idea of time involved. I currently have left-over WEST System epoxy, so for starters, that cost will not be included.
Materials to date:
4 pieces of 1/8 x 48 inch balsa (hull sides)
1 piece of 1/4 x 36 inch balsa (bulkheads, bracing, mounting tabs, etc.)
1 chunk of 2 inch thick foam (deck and bottom of hull)