Sunday, August 31, 2014

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!



Friday, August 15, 2014

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


Monday, June 30, 2014

June, 2014

Painting The Inside

After applying two coats of Interlux Epoxy PrimeKote 2-part primer, I lightly sanded and cleaned the hull as prescribed, and applied the first coat of white Interlux Perfection 2-part polyurethane high gloss topside paint.

I followed the recommended roll and tip technique using a West System foam roller and a badger brush.


About 48 hours later, I lightly sanded and cleaned the inside of the hull in preparation for the second coat. For the second coat, I added Interlux's Flattening Agent for 2-part polyurethanes.

Mixing 2-part paint with thinner and then with 2-part flattening agent requires different part ratios and a specific mixing sequence to obtain the desired result per Interlux's instructions. I created a spreadsheet to calculate the combined ratios to mix only the amount of paint I needed.

View of the hull after the second coat was applied.


Finishing The Deck Frame

In preparation for the deck, I had to build up the deck frames to ensure the top surface of the deck frame is leveled with the sheerline. This work included building up the king plank, the breasthook and the deck beams.

My mistake was not to interpret the drawings correctly when I fitted the deck beams, the breast hook and the king plank, although the drawings were clear. 




Western Red Cedar strips added over the deck beams... 
...and 30 mm x 4 mm marine plywood over the spaceframe tops.

Western Red Cedar added over the king plank and the breasthook, shaved and sanded.
View of the added Western Red Cedar over the main foredeck beam...

View of the added Western Red Cedar over the forward foredeck beam and king plank after shaving and sanding.

Next, I cut two 6 mm plywood pieces to fit between the jib cleat and the aft deck beam on the starboard side. I glued both pieces together with epoxy resin and colloidal silica. Then, I shaved the starboard plank angle and fitted the 12 mm plate with more epoxy resin and colloidal silica. The same process was followed on the port side.

This doubler is for the main and lower shroud sheaves.

I decided to add more curves to the deck to smooth our her lines around the aft deck beam where it intersects the king plank and where it turns around towards the jib cleat.

I cut a couple of 48" long x  30 mm wide strips of 4 mm thick plywood. I made the cut across the grain to facilitate the bending of the plywood around the desired turn radius. The width, from a point in the rear deck beam, was reduced to 25 mm at the king plank. One piece was enough to go around from the king plank to the aft deck beam and to then to the jib cleat.

For the rear, I cut a couple of 24" long x  20 mm wide strips of 4 mm thick plywood. I also made the cut across the grain for these to facilitate the bending of the plywood around the desired turn radius.

Next, I added Western Red Cedar reinforcements behind the plywood bends between the king plank and the aft deck beam. Also behind the bend between the aft deck beam and the stringers reinforcing the carlin. 
Likewise in the rear, behind the plywood bend between the stringer and the transom

The Deck

Varnish will cover the deck around the boat so I made sure to select a couple of 4 mm sheets of marine plywood with a pretty wood pattern to show off. This is the one I selected for the foredeck.

Firstly, I measured the distance between the aft end of the king post and the forward edge of the breasthook where the deck will end. I added 1 inch to that dimension and cut the plywood sheet across. Secondly, I centered the sheet of plywood along the king plank leaving half an inch extra aft and forwards so I can then plane it to shape after it has been glued in place.

Jeremy Deacon, fellow Merlin Rocket sailor and builder, recommends this procedure. This way not only does one have a slight margin for error but one gets a really good straight join when doing the gunwhales. Jeremy has also done several top-notch boat restorations. Thank you, Jeremy!

Once over the deck, I secured the foredeck with clamps and using a pencil I traced the outer edge of the gunwhale underneath. Then I moved the foredeck to a temporary work bench protected with poly to avoid damaging the face of the plywood that will be exposed. I traced parallel lines to the gunwhale lines, half an inch apart for cutting the foredeck with an extra margin for error.

Using a power jigsaw, I cut along the lines. Then I placed the foredeck back on the deck frames, centered and secured with small clamps. Next, I traced the curves  under the foredeck from the aft deck beam to the king plank. Later I added parallel line half an inch apart for error margin before cutting.

View of the new foredeck from above. I'll follow a similar deck pattern as done on Rob Holroyd's WICKED. Two triangular pieces left from cutting the foredeck will be squared off and used to cut the adjacent pieces to the foredeck that will go half way down over the doubler for the main and lower shroud sheaves.


Next, I cut the second 4' x 8' sheet of 4 mm marine plywood in half along its length, ending with two 2' x 8' pieces. One for each of the side decks.

Later, I clamped the two 2' x 8' pieces over the side deck and over the transom. 


For tracing the outer gunwhales on both side decks, I followed the same process as with the foredeck, then adding a parallel line about half an inch apart for error margin.

Same process with the inner carlin lines except some careful foot work and balancing inside the hull was needed to trace the pencil lines.


View of the foredeck, the side deck and the deck piece between the foredeck and the side deck that was made from the plywood triangular pieces left from cutting the foredeck.


Aft view of the side deck turning around towards and over the transom. A narrow 25mm plywood strip was cut and placed over the transom, connecting both side decks.



All deck pieces in place before epoxy coating and fitting.


Looks like she's already smiling and just waiting for makeup!