So here we have the 20 foot by 16 inch 3/4 inch plywood platform on the basement floor. It has been shimmed and leveled and some parts are held down with bricks. I have laid out the pattern using offsets from CAD and have screwed in pieces of angle aluminum at each bulkhead, which is every foot. The center 8 feet has a constant cross section and the tapered ends are 5 feet long and symetrical. The hulls are 10 inches deep and 10 inches wide with 4.5 inches of rocker at each end. The round hull will be made with 1/4 thick red cedar strips and the top will be flat for now. The sides ar 5 inches high and are marine plywood, as are the bulkheads and top. I was going to use a backbone but in the end decided not to. Still a little nervous about having a flat thin top that I might step on and through....but.....
The bulkheads, sides and tops were cut on a CNC router table by my pal Kevin at Atlantex Creative Works in Porter's Lake, NS. I supplied the CAD files and voila!!! Kevin has already been a big help on this project and many others. We ripped and planed the nailing strips while the CNC was cutting the plywood.

The V-goove in the bottom of the bulkhead is to allow water to run from one end to the other to make easier to drain in the highly unlikely event of water getting in!

The square cut outs are for the 1 inch by 1 inch nailing strip to attach the deck to the hull. I did end up cutting notches every three inches over the last 6 feet to make them easier to bend. The sides were cut from an 8 foot sheet so I hade to add a section in the center. I made the joints between bulkheads and used the  trimmed ends to form a lap joint instead of scarfing. I did scarf the nailing strips (badly, no pictures) and added a block to each end to allow an anchor point for lifting and for rudder attachment. I also added a double strip at the points where the cat frame will attach to the deck.

Clearly I should have put a little more thought into the joint between the nailing strips and the end block so I will have to make some adjustments. It was suggested that I screw the sides into the nailing strips when I glued them together but I was concerned that the nailing strip was so strong that it would dimple the plywood instead. As it turns out I should have been a bit more carefull about wedging the strip out, and I will have to check for gaps when I remove the hull and turn it over. It may be necessary to cut a bit and fill with thickened epoxy but most of it looks good. Since much of this will be very hard to get at when the cedar strips are in place I decided to seal as much as I could with epoxy at this stage. I used the bulkheads to hold the nailing strips and then used bricks to hold the nailing strips flat to the platform until the epoxy was dry.

At this point I did not have the cedar strips ready so I pulled the hull and hung it from the ceiling while I built up the second one to the same stage. I corrected a few of the mistakes and made a couple more but I now have two frames pretty much exactly the same.

I am going to use a slightly different method of stripping this boat and see how it works. I tried a demo with cutting each strip from full width at the 5 foot mark, down to a sharp point at the end. I am making a cap to cover the very end of the tip of the hull and provide a small landing strip for each strip. I will cut them off 2 or 3 inches from the end. The strips will alternate between 11 feet long and 7 feet long. I installed a doubling section on the 2 bulkheads 7 feet from each end. This will allow a better surface for the adhesive and make fitting the pointy ends of the strips much easier than cutting both ends of an 18 foot strip. The strips ended up being a bit wider than planned but we (the royal we with the help of Kevin!) only cut enough for one hull so I think it might be a good idea to make them a little narrower for the second hull. Either way, much of the strip will be sanded away and then some of the craks filled with thickened epoxy before adding one layer of glass to the hull at least. All this adds weight of course but I think I will need the extra protection  operating in the bay.

I have learned a tremendous amount from people posting on the Boat Design Forum and many of these ideas will find their way into the propulsion and steering systems etc.

I am currently drawing up the frame for the cat and trying to come up with a clever (quick and easy) way to attach the frame to the hulls. I have been designing outriggers for the single hull version of this too but my designs are all 4 feet long. This may be due to the gale force wind that came from behind and snapped the gold plated sheet of marine plywood on my roof in half and sent it flying over the hood of my car.  "Should have seen that coming...." ......I see more scarfing in my future.......

Progress is being made......



The basics….

This boat will a catamaran first. The hulls will be 10 inches deep, ten inches wide, and 18 feet long. The hull sides will be 5 inches deep and then the bottom will be a semi-circle. The flat top and sides will be made of 3 or 4 mil marine plywood and the rounded bottom will be stripped with ¼ by ¾ cedar strips. The hulls will have 5 inches of rocker and be symmetrical on the bow and stern. There will be Meranti plywood bulkheads every foot and these will have a large part of the material removed to save weight. There will also be a backbone running the full length made of either Meranti of marine plywood and it will also have much of the center material removed. I will put extra blocks in two places on each hull where the deck fixtures will be mounted, and where the rudder attachment points are.

The surfaces on the inside will all receive a coat of resin and the outside may get a layer of cloth as well. This boat will be used mostly in the ocean and needs to be able to withstand a careful drag up the beach.

The hulls will be spaced 6 feet center to center and the mounting frame will be made out of aluminum with two attachment points per hull. Not sure on the attaching details yet…..There will be a rudder fixture on each hull but in the cat configuration I would expect to use just one in most conditions. I may find that having the rudder attached to the main frame is better, but I don’t know at this point. It may also not be necessary to have the rudder in the water at all times.

The cat will be set up initially for one rider but the eventual goal is to have a tandem. The rider will sit in the middle of the frame on a seat similar to that on a recumbent bike.

The drive mechanism will consist of a  bicycle bottom bracket mounting a bike crank and sprocket, a bike chain running forward to a smaller sprocket modified to drive the input shaft on a 90 angle gear drive. There will be a shaft running from the output to the rear of the boat where a propeller will be mounted. I am not sure at this point what the shaft and propeller configuration will be but……….This will be the same type of drive system that will be used on the single boats as well. Eventually I would like to switch to something more like the

Seacycle Drive

on the tandem but have the riders one behind the other instead of side by side.

Step 1

The first step now is to lay out the pattern for the hulls. They will be constructed upside down with the deck added last. I am laying out 19 feet of plywood 16 inches wide which will be supported in numerous places by cross strips of the same material. My basement floor is quite level but I will trim the pattern using a laser level. Then I will use a snap line to lay out three straight parallel lines for the full length. The center 8 feet of the hull has a constant profile and both ends have the same taper for 5 feet each. I did a test previously to see how the strips would work so I will use the curves from that to lay out the profile on the plywood. I have aluminum angle pieces to screw into the plywood to hold the sides in position while I install the rest of the frame. Once I have the pattern drawn out on the plywood I can cut and join (scarf probably ) the pieces for the sides and backbone.

Good morning all,

This site is intended to give a blow by blow story of the building of various projects, as well as a few pictures of bike projects from the past.

The big project this winter is the construction of a pedal powered propeller driven catamaran. The two hulls can also be used with outriggers to make two single boats. Most of the ideas for these boats come from information provided on the net by people who have already been down this path, and have graciously offered their results to the community.

I hope you will find something interesting in this as I  tackle my first boat project!

Glen