Preparation

Plans

I bought boat plans from Tracy O'Brien. 156 Bunker Creek Road Chehalis, WA 98532 United States. Tracy O'Brien's plans and instructions are always very complete. All pieces are shown with complete dimensions. They all fit together just as designed. There is no "Beat to fit. Paint to match" required.

O'Brien plans for the Nemah

Scarphing

The project begins by joining 8-foot sheets of plywood into longer sheets. The sheets are joined by scarphing and gluing, to form sheets 16 feet long. 

I used a John Henry scarphing jig attached to my Makita 4-3/8-inch power planer. This scarphing jig is available from John Henry Inc. POBox 7473, Spanish Fort, Alabama, 36577 (251)626-2288.

Makita power planer with John Henry jig

Underside of jig

Scarphed panels are then glued together with epoxy, to form long sheets.

Scarph-cut plywood

Joining panels at scarph joints

TIP: A COMMON MISTAKE WITH EPOXY IS STARVING THE JOINT. IF YOU HAVE A PERFECT JOINT AND YOU CLAMP TOO HARD, YOU CAN SQUEEZE THE EPOXY OUT OF THE JOINT AND REDUCE THE INTEGRITY OF THE JOINT. UNLIKE WOOD GLUE, JOINTS THAT DON'T FIT-UP PERFECT AND HAVE A LITTLE EXCESS EPOXY IN THEM ARE STRONGER THAN STARVED JOINTS. REMEMBER, THE EPOXY IS WAY STRONGER THAN THE WOOD.

A quality scarph joint is hard to see, even in this cheap CDX plywood.

Cutting, coating and sanding

After creating the long plywood panels by scarphing, it is time to cut the bottom and side panels to the proper shape. The plans provide a table of offsets for each shape. The offset points in the tables are marked on the bottom and side panels.

Laying out stations and offsets on plywood

A smooth curve is drawn to connect the offset points. I used a long supple batten strip to trace the smooth curves.

Using a supple batten to connect the dots in a smooth curve

Then I cut to the line with a jig saw.

Cutting panels to shapes shown in the plans

After cutting the panels to shape, each panel is coated with epoxy-impregnated fiberglass. I use a window washing squeegee to spread the epoxy.

Notice that I did not epoxy the outer 2 inches of fiberglass to the panels. That is where the biaxial fiberglass tape will attach in the future "glue" step.

I purchased my fiberglass from Jamestown Distributors

And I used West System 105 Epoxy Resin and 207 Hardener

TIP: MY 2 FAVORITE EPOXY COMPANIES ARE WEST SYSTEM AND SYSTEM 3. THEY BOTH HAVE GREAT BROCHURES ON WORKING WITH EPOXY. HERE ARE A FEW TIPS ON WORKING WITH EPOXY.

1) MIX SMALL BATCHES OF EPOXY UNTIL YOU LEARN THE APPROPRIATE BATCH SIZE. LARGE BATCHES MAY LEAD TO WASTED EPOXY, WHICH IS QUITE EXPENSIVE. AND, LARGE BATCHES MAY "KICK OFF" CURING IN THE POT BEFORE BEING USED, WHICH CAN BE A DISASTER.

2) IF YOU SPREAD MIXED EPOXY THIN, IT WILL HAVE A LONGER POT LIFE SINCE IT WILL NOT HEAT UP. IF YOU LEAVE IT IN THE POT, IT WILL GET HOT AND CURE TOO FAST.

3) THIN FIBERGLASS CAN BE LAYED UP "DRY" (PLACED ON DRY WOOD THEN SATURATED WITH MIXED EPOXY). THICK FIBERGLASS LIKE BIAXIAL TAPE MUST BE SATURATED BEFORE LAYING UP. WHEN LAYING F/G FABRIC, BE SURE THAT THE F/G DOESN'T FLOAT IN THE MIXED EPOXY AND SEPARATE AWAY FROM THE WOOD SURFACE. IF IT FLOATS, THE STRUCTURAL INTEGRITY IS STILL GOOD AND THE FINISH IS STILL BRIGHT BUT THE BUMPY IRREGULAR SURFACE WILL DRIVE YOU NUTS.

4) USE PUMPS THAT DISPENSE THE PROPER PRE-MEASURED RATIO OF EPOXY AND HARDENER.

5) WHEN WORKING WITH EPOXY, EVERYTHING SHOULD BE DISPOSABLE. YOUR GLOVES, BRUSHES, MIXING POTS, STIR STICKS, ROLLERS, SPATULAS, SQUEEGEES, SHIRT, PANTS AND HAT WILL GET EPOXY ON THEM. CLEANING EPOXY REQUIRES SOLVENTS THAT ARE CARCINOGENIC. IT IS YOUR CHOICE, CANCER OR DISPOSABLE.

6) ABOUT BLUSHING: NEAR THE END OF EPOXY'S CURING, A REACTION WITH OXYGEN CREATES A WAX ON THE SURFACE AND A WEE BIT INTO THE SURFACE OF THE CURED EPOXY. THIS IS CALLED "BLUSHING". FUTURE EPOXY AND PAINT WILL NOT STICK TO THE WAX. REMOVAL OF THE WAX REQUIRES WASHING WITH WATER THEN SANDING. WHEN MORE EPOXY MUST BE APPLIED TO A PREVIOUS EPOXY LAYER, SUCH AS ADDITIONAL COATS OR GLUING TO A COATED SURFACE, APPLY THE NEXT EPOXY LAYER/GLUED ITEM BEFORE THE PREVIOUS LAYER CURES. THAT WAY, YOU WON'T HAVE TO SAND ANY WAX AWAY AND YOU WILL GET A CHEMICAL BOND BETWEEN THE LAYERS WHICH IS WAY STRONGER THAN THE MECHANICAL BOND THAT RESULTS FROM SANDING. OR, USE A NON-BLUSHING HARDENER LIKE WEST SYSTEM 207 HARDENER. 

Once the epoxy has cured, I sand away the excess fiberglass.

   

Although the plans say to sand the entire panels, since my final finish will be bright uncoated epoxy, I did not sand the entire panels. This starts the discussion about UV exposure. This boat is an experiment. My hypothesis is that, here in Alaska (where even on the sunniest days this boat will see little sun and in the winter there is no sun) UV exposure is not an issue. I'll let you know the result of the experiment in 20 years.

I did not apply fiberglass/epoxy to the 2 inches around the outside edge. This is where the biaxial tape will be applied to stem, chines and transom joints during the future "glue" phase of the stitch and glue boat building. I sand only the areas where there will be future epoxy such as the stem, chines and riblet locations.

Riblet locations sanded

TIP: POWER SANDING AND POWER CUTTING CREATE LOTS OF DUST THAT CAN MAKE A MESS OF YOUR SHOP AND CREATE PROBLEMS FOR EPOXY, PAINTS, VARNISHES AND MARRIAGES. I DO ALL OF MY POWER SANDING, TABLE SAW CUTTING AND CIRCULAR SAW CUTTING OUTSIDE.

TIP: MY RANDOM ORBITAL SANDER IS GOOD FOR REMOVING LOTS OF MATERIAL IN A WELL-CONTROLLED MANNER. BUT IT LEAVES THEM LITTLE SWIRLIES EVERYWHERE. THOSE SWIRLIES HAVE A WAY OF SHOWING THROUGH PRIMERS, PAINTS AND VARNISHES. FOR SURFACES THAT WILL BE VISIBLE IN THE FINAL BOAT, I ALWAYS FOLLOW RANDOM ORBITAL SANDING WITH A PALM SANDER TO REMOVE THE SWIRLIES.