The Dragonfly Darter is my second electric cruiser. The building method is to make a larger boat but lighter then the Bumble Bee cruiser. The Dragonfly Darter is 10 feet long by 4 feet wide with sides at 2 feet maximum.
The plywood layout is placing two sheets of 1/4X4X8 end to end. Using a scrap piece of plywood to tack the two pieces of plywood together with small nails to hold in place. The original curves of the layout are sharp which makes the bottom panels hard to get to make the bend of the curves. It can be done but you will have to build a fixture to pull the plywood to the shape of the framed side panels. You can make adjustments to the layout lines to suit but the shape of the boat is what I was hoping to hold and maybe worth the extra pain.
This is the rear of the boat layout. The 50-degree angle can be changed to your liking and again the curve in the rear can be gentled to your taste. The above layout is the bow. The curve of the bow can be lessened for easier assembly by changing the distance from the bottom of the plywood sheet specified by the drawing at the top.
In the picture above you can see the first side cut out of the one sheet of plywood is then used as a pattern for the second side so they are identical. This is the full side skin cutout with the bow piece.
The framing is from splitting of 1X4's. Laying the pieces out using the skin outline as the pattern for the framing. I started with the bottom piece and went from there. Each piece completed sets the next piece for size. Before screwing the first frame to the skin lay it on the framing wood for the other side as a pattern transfer.
The fixture I had from building bicycle cars came in handy for a workstation for building this model. The complete framing mounted on the skin. You can see the joint for the bow attachment and the void in the bow for the 2X4 that joins the two sides together. The same in the rear, the void is for the stern to joint the two sides together.
The two sides are c-clamped together with the frame on the outside. This way when you sand the edges they will be the same. This will help when you assemble the bottom skin. Pictured above you can see the two sides joined in the front and rear. The stern board has to be cut to match the top of the skin and frame.
The rear board for the stern is screwed directly into the side skins. The frame that runs along the stern is then screwed thru the rear board to the framing piece. You can see the angled cut across the top of the stern. This is a full view of the front bow 2X4, which has to be cut at the angle of the side skins. You can mark the 2X4 holding it up to the skin and then cut the angle. The mainframe pieces of the boat are laid out to the wide of the position in the boat. The front width is 41 inches and the rear is 46 and 5/8 inches wide. You can set the width as far as what the settings will be.
These are different views to show the cut framing. Make sure you are square at the skin frame and the cross framing.
The curves are sharp so I started the bottom skin on the flat surface first. You can see you only go half way on the 1X3 with the bottom skin so you can continue.
You can see the front of the boat is narrower then the rear. The second section of the bottom skin is in place. I used 1 ½ “ screws to pull the bow skin down to the 2X4 then when dry went back and replaced with 1” screws.
Front view of bow with skin in place. This is side view of the 2X4 cut to shape of bow skin.
An extra framing for the bottom skin to attach to was needed to strength the bend. This is the toughest compound curve to get the skin to conform to the bottom shape. A second frame was added ¾ of an inch from this attachment point. If you try to form the sheet with out the second frame piece it will pull the screws out of the plywood as you apply pressure to get it to attach to the stern. Install the second cross frame then glue and screw. Let it dry in this position for 24 hours.
