I Start My Boat

First, I build a mold.

Assembling the Boat Mold

Next, I join together my EPS sheets. My boat is 12 feet long, but my EPS sheets are 8 feet long. Therefore I butt my sheets together and bond them with expanding polyurethane foam.

EPS Sheets Butted Together for Bonding
Panels are Bonded
Joint after Trimming

I designed the hull in Hulls, a free program for designing hulls. I then transfered the hull and panel layouts into AutoCAD where I completed the more detailed design drawings. The panel layouts were plotted full sized, glued to 1/8″ masonite, and patterns were cut from the masonite. I traced the panels to the EPS sheets from the patterns.

Tracing the Hull Panels

I cut the hull panels using a sharp steak knife.

Cutting the Hull Panels

The side panels are attached to the mold and bonded with expanding foam.

Side Panels are Attached to the Mold

Thickened epoxy is applied to the top edges of the  side panels (which are actually the bottom edges since the hull is being built upside down) and the bottom panel is bonded to the side panels. The jugs of water are used to bend the bottom panel to shape. Drywall screws temporarily hold the bottom panel in place while the epoxy sets.

The Bottom Panel is Attached the the Mold

Once the epoxy sets I shape the hull with a Surform and sanding block. The bottom panel is trimmed flush with the side panels, and all edges are given a slight radius so the fiberglass will drape over the hull properly.

Shaping the Hull - Stern

The photo below shows how much rocker the hull has.

Shaping the Hull - Bow

I also added a bit of V to the bow and stern.

Stern V
Bow V

The hull is ready for fiberglass. I used 4 layers of 6 oz cloth on the bottom and 3 layers on the sides. Getting all of that cloth to drape properly over the hull took 2 days.

Fiberglass is Draped Over the Hull
It Took 2 Days to Get the Fiberglass To Drape Nicely Over the Hull

It took another day to wet out the cloth with epoxy.

Wetting Out the Cloth
Wetting Out the Cloth Took Almost a Full Day

Three hot coats were needed to fill out the weave and get a glossy finish for sanding. The hull was then flipped over and the mold was removed.

The Hull is Flipped and the Mold is Removed

Here I am pouring some expanding foam into the bow.

Pouring Expanding foam in the Bow

Now I am ready to fiberglass the inside of the hull.