Here is where we started. The hull itself is symmetrical top to bottom. Because of this we will make two half hulls and join them together later. We first plotted full size frames and spray glued them to 3/8″ plywood. The frame spacing varied from 3″ to 12″ depending on the amount of curvature in the area. these frames were then attached to the particleboard strongback. The frames were then covered with 1/4 x 3/4 wood strips. They did not have to be tight against each other since they would be covered with foam sheeting.
The foam easily bridges 1/2″ gaps in the wood strips.
Note the radical change in framing size.
Another view showing how the strips looked in the tail.
Ready to foam. Any areas that that would be exposed to the epoxy were covered with packing tape. This includes under all edges of the foam pieces. This will prevent the epoxy from sticking to the wood strips This is important because after the foam is fiberglassed it will have to be pulled off of the frame. To help with this plastic straps will be laid under the foam to be used for separating the hull skin.
Starting to cover the hull with the foam sheet. Because of the amount of curvature in the hull we had to use smaller pieces of foam, heat them until soft in front of an electric heater then quickly form and attach to the hull with staples. The small gaps between the pieces will be filled with epoxy prior to laying on the fiberglass cloth. Note the brown tape under the foam edges.
Since the tail was to move we decided to do it separately from the rest of the hull. After all the foam was attached to the frame we checked of the pieces to make sue that they were tight to the frame. Edges that had curled up were heated with a heat gun to soften them and then they were stapled tight. Next we went lightly over the foam with a coarse sanding block to knock down any high spots. A coating of epoxy was applied to the whole surface and a mixture of epoxy and microballoons was troweled over the joints to fill in any gaps between the foam pieces
After applying two layers of fiberglass cloth the shell was pulled from the mold. Not quite as easy as it sounds since all of the staples that held the foam to the wood had to be pulled thru the foam. The inside of the shell received a coarse sanding, a coating of epoxy and epoxy putty and two more layers of cloth.
Next pull all of the staples from the wood and do it all over again for the other half of the hull.
The halves have been joined together and are being faired with an epoxy microballoon putty. The more care you take when applying the cloth and resin the less time you will spend doing this.
Ready to start cutting.
Here the canopy openings have been cut. The hull is sitting in a frame that was made before the first hull half was pulled from the mold. This keeps the hull in shape and gives a centerline reference surface.
Here is the original pedal drive mechanism The two foot pedals were attached to water cylinders that acted as pumps to drive the cylinders that moved the tail. The reason for this type of drive is that it would allow you to pivot the whole tail for steering while you were pedaling. The later direct drive was much simpler, more efficient less prone to problems. The only disadvantage was that to steer you had to push down on one pedal and hold the tail to one side toact as a rudder. Once you were pointing in the right direction you could continue pedaling. We did manage to take the sub through the slalom course this way at the 8th International Submarine Race.
There are 4 pneumatic cylinders in the tail that act as variable rate air springs. By varying the pressure in the cylinders the stiffness of the tail can be varied from no resistance to flexing to completely rigid, This controls the flexing of the tail to optimize its movement through the water.