Actually this sub is modelled after the porbeagle shark. In fact, if you take an outline of a porbeagle shark it will match up to that of the sub, right down to the tail fin. I thought Sand Shark just sounded better. It was built for the 6th International Submarine race in 2001 but never competed due to a stupid shop accident. There is now a sign in my shop that says “USE C-CLAMPS NOT HANDS” Enough said, lesson learned.
For the construction of this sub we used a c-flex core with multiple layers of glass cloth and mat inside and out. It is a heavy, very strong hull built to withstand an occassional bump into the sides or bottom of the tank where the sub race is held.
After the full scale frames were plotted and glued to plywood they were trimmed to size and stacked onto a piece of 2″ pipe. Spacers were added to keep the proper distance between frames. The decision to make the hull in this manner was the type of core material we would be using and the fact that the hull was not symmetrical top to bottom. It was necessary to cut all of the frames and put them back together with strips of wood. This was due to the fact that the hull was going to be one piece and this would allow the frames to be easily removed. The rotisserie arrangement allowed the hull to be rotated.
Here is the hull covered with c-flex material. C-flex is made up of small diameter fiberglass rods woven together in a fine scrim of fiberglass. It is about one foot wide and comes in a long roll. The rods span the distance between the frames and give a pretty fair curve. After the c-flex is attached to the hull with staples the fiberglass scrim is wetted out with a low shrinkage polyester resin. After it sets additional layers are added as required. Alternating rods had to be trimmed at the bow end in order to allow the large change in hull section size. This was the last sub I built with polyester resin. Although I don’t mind working with it, a few of the neighbors had some comments regarding the sweet smell.
Because the tail would be moving and would have it’s own internal framing the hull was cut at the point of flexure. The frames for the complete hull length were originally included in order to have the c-flex generate the proper hull lines.
The canopy was cut out, frames removed, the rear opening was flanged and the tail was attached. What are shown here are polyethylene scales that bridge the gap between the frames and allow the tail to flex side to side. Without these the neoprene skin for the hull pulled into the gap between frames and gave the sub a ribbed look.