August, 2014

The Rubbing Strakes

The Rubbing Strakes for Pícara are made of solid Mahogany wood stock. With a thickness of 9mm, the rubbing strakes run from the bow to the transom reaching a maximum width of 50mm between stations 5 through 7. I opted for a multi-piece rubbing strake for my boat.

The method I chose to fit the rubbing strakes is to avoid any plastic nails or screw holes on the face of the rubbing strake. Not the easiest method, but I want to learn how to do it. And it has taken me the longest to learn it.

The biggest challenge is to secure the rubbing strake tightly against the gunwale while gluing them together. Most importantly, ensuring that the top edge of the rubbing strake tightly fits against the top edge of the deck, without any gaps.

The problem is, how to clamp the rubbing strake against the gunwhale? Where to clamp it from? The gunwale's angle and curves resemble the movement of a Chinese Dragon.

Many thanks to Keith Callaghan for providing a drawing on the rubbing strake clamp detail with a timber batten. This clamping method proved very useful.

I'd also like to thank fellow Merlin Rocket builder/sailor Jeremy Deacon, Miles James and Al Jackson for their build photographs, drawings and expert advise.

All recommendations for this particular method included the temporary addition of wood blocks screwed under the gunwale every 150mm or a 8mmx12mm strip stapled the length of the gunwale using 15mm staples, stapled every 75mm.

I deviated from using the wood blocks and instead I used metal eye screws because I can easily drill a pilot hole at the desired gunwhale angle per location and the eye screw provides a strong pad for the clamp foot in parallel to the gunwale. 

Here are the eye screw fitted on Pícara in preparation to fit the aft starboard section. 

View of the eye screw fitted on Pícara in preparation to fit the forward starboard section. 

First dry run clamping the bottom of the aft piece first. I leave 1 mm or so of extra material on the top edge so I can shave and sand flush with the deck. It also leaves most of the stock at the bottom where it will be shaped to the right width per station according to the rubbing strake drawing.

As you can see, the lower clamping torques the top of the rubbing strake away from the deck.

View of the eye screws underneath the rubbing strake piece where the clamp food can get a good grip.

Another view of the eye screws underneath the rubbing strake piece.

Next, I clamp the upper side of the rubbing strake tightly against the edge of the deck. I also added a piece of scrap wood over the inner edge of the deck for protection. Now I have a perfect joint.  Of course, once epoxy with colloidal silica is applied, things can get very slippery. All of a sudden the static energy can be released and the piece can move out of place. Given the warm weather we're experiencing in Austin, Texas, I continue to use West System's 209 Extra Slow Hardeners. It fully cures in 24 hours.

A blue tape protects the top outer edge of the deck to avoid epoxy contamination over the area that will be varnished.

The same process was followed for the rear port side piece.

For the forward starboard piece I have to solve for a different problem. The forward deck provides no opportunity for clamping anything from so I had to get creative to implement a counter-torque technique recommended by Keith Callaghan.

The counter-torque technique consists of adding a rectangular stick of wood about 12" long placed between the rubbing strake and the outer foot of the lower clamp.

The creative piece was the addition of a temporary 4" x 4" cedar timber about 6' long over the deck to secure the bar clamps from. I used scrap pieces of 4 mm plywood between the timber and the deck for protection. I secured the timber with larger clamps at the breasthook and at aft deck frame.  

But the bar clamps would slip off the 4" x 4" timber so I clamped a scrap piece of 15 mm x 30 mm x 6' pine stock along the back of the cedar timber so the bar clamps can get a great grip. Clamps, clamps and more clamps. Had to get more. Said it before, say it again. You can't have enough of them. And the slipping and moving stopped!

View of my enhanced clamp collection from the bow during the dry run.

The same process was followed on the port side. View of the port side while setting up the clamps in place before gluing.

Now with protective blue tape on the outer edge of the deck while gluing the forward port side rubbing strake piece to the gunwale.

View of the clamps from underneath looking from the rear.

View of the clamps from underneath looking from the bow on the port side.

After removing the clamps, I scarfed the forward and aft rubbing strake pieces in preparations for the mid-section piece. I projected a tangent line off the gunwale to the rubbing strake and proceeded to shave and sand until a smooth flat scarf joint surface was achieved. 

View of the aft piece after shaving and sanding.

Thank you for visiting my blog!

Fair winds and happy sailing to you!

July, 2014

The Deck   ...continued from June

Prior to fitting the deck pieces, I coated the undersides with 3 layers of epoxy resin. Once fitted it would be extremely difficult to crawl under and apply the resin. Good call out and timely reminder by fellow Merlin sailor and builder Jeremy Deacon.

Later, I lightly sanded all surface areas to be glued.  

A day later, I mixed West System epoxy resin with West System 206 slow hardener, added colloidal Silica and applied over the deck frame only where the forward piece goes.

Once over the deck frame, I aligned the forward deck to its final position and clamped it in place. 

To ensure a flat and tight bond against the deck frame, I added several wood pieces to weight down the deck against the deck frame.

You really can't have enough clamps...

This cedar beam was used to hold down the forward deck over the king plank.

A day later, after the forward deck was fitted, I removed the clamps and weights on the forward deck and setup to fit the starboard and port forward side decks. Before applying the epoxy I tested the fitting of these pieces, especially where they join the forward deck.

To help align the edges on these plywood joints, I added a 1 inch wide strip of  4 mm plywood under the outer edges of the forward deck. Gluing only a half inch under the forward deck side, thus leaving a half inch lip to receive the forward side deck.

View of the starboard front deck piece after fitting.

View of the port side forward deck piece after fitting.

One day after the forward side decks were fitted, I setup to fit the starboard and port side decks. Again, proper pressure applied to the plywood to attain a tight joint.

Starboard deck view from the rear. Clamping at the transom was done relatively easy by placing a sacrificial strip of plywood on top of the deck and clamping against the plank landings below. The clamp pads have rubber covers to prevent damaging the wood.

Same process was followed on the port side. View from the port side deck from the transom.

Here too, proper pressure applied to the plywood to attain a tight joint.

Lastly, I cut a 40 mm wide strip to fit over the transom between the port and starboard deck pieces. I cut it just a millimeter longer and snapped it tightly in place with a healthy amount of epoxy resin and colloidal silica. 

This view shows how I clamped this piece over the transom.

The deck pieces had an extra half inch of material for margin of error at each side. I started to shave the excess off but it was going too slow. I decided to try my router on the outer edges of the deck. For this, I used a carbide tip trim bit.

Because of the gunwhales' angle, this special router bit with a bearing only trims the edge of the deck down to 2 mm from the gunwhale's upper edge. 

I used this same router bit to trim the excess plank material at the transom so I knew what to expect. Nevertheless, I was extremely careful not to go too fast so the bit could do its job.

Very glad I used the router trim bit. It took me less than 1 hour to trim the inside and outside edges of the deck.

After routing the excess wood, I sanded down the edges of the decks flush with the gunwhales using 80 grit sandpaper.

View of the aft deck and around the transom. The finish is really smooth and a great base for rubbing strakes and carlins.

Very little is left to sand after the trimming the edges with the router. 

Front view after fitting the decks.

For the chute opening I planned to make a 1 piece cap made of solid Mahogany. I placed the Mahogany stock over the chute area and traced the shape. Then added a half inch to the outer edges for margin of error and then cut the trapezoid shape piece.

I applied epoxy resin with colloidal silica to the deck frame, placed the cap on top and placed a little bit of downward pressure to ensure a tight fit.

The next day. I used the plunge router to make a hole at the center of the chute opening. Then, I ran the router with the trim bit to cut the opening. Well, big mistake.

As I routed the opening, wood shavings were falling down the chute. At some point while I was cutting the chute opening, the router bit got really hot and ignited the wood shavings that were falling. I ended up with a couple of embers on top of the wood shavings over the bow tank.

Fire in the hull!

Smoke started to come out of the chute opening. Fire images flashed through my mind as I grabbed a bottle of water next to me and dumped its contents down the chute opening. 

Needles to say the cap was damaged and I had to remove it. Using a sharp chisel, I proceeded to chip away the old cap. 

Plan B was to use single pieces made from solid Mahogany stock.

Here's the finished cap. I still need to add a rounded Mahogany edge in front of the breasthook and round the corner of the chute opening to guide a smoother spinnaker launch.

 

And here she is today, ready for her rubbing strakes and carlins.

Naming The Boat

Perhaps one of the hardest things to do has been to figure a proper name for her. Not to be taken lightly, I believe the name must reflect a bit of the boat's character and personality, its ancestry and its destiny. So, after careful consideration and thinking Neptune and Aeolus will approve, I've decided to give her a Spanish name that means:

• Naughty
• Impish
• Cheeky
• Wicked
• Astute

I therefore name her...

Pícara