Friday, October 31, 2014

October, 2014

The Rubbing Strakes (Continued)

 After removing the clamps and cleats I had to step back and spend some time thinking about what I had to do next. This is delicate finishing work. I can't afford to make a mistake since that would probably mean replacing a rubbing strake piece.

I had to develop a technique that would take me down several steps to achieve a smooth flush surface between the deck and the rubbing strake. I decided to do it in 3 steps, each subsequent step slower than the previous one.
  1. Shaving with my Stanley block plane
  2. Coarse sanding (80 grit paper)
  3. Fine Sanding (220 grit paper)

The blue tape served as protection during the entire process and prevented me from getting too close to the deck. Shaving took me close to ~0.5mm off the deck. From there, coarse sanding took me down to the blue tape until it started to peel off. Then, light sanding to a smooth finish between the deck and the rubbing strake.

Getting to the joint was like uncovering a treasure in the sand. Anxious to get there but cautious not to damage it.

I'm pretty happy with the joints I achieved for being this the very first time I do this type of wood work.


Always sanding along the deck grain too avoid scuff marks.


View of the port side as I sand down the rubbing strake.

The scarf joints came out better than I expected.


View of the port side rubbing strake after the initial 3 step process.


View of the aft port scarf joint between the aft rubbing strake piece and the next piece.

Photograph of port side rubbing strake piece #4 while sanding the excess material off the front, before fairing.

Next, the aft section of the same piece before sanding and fairing.


View of port side rubbing strake piece #4 after sanding and initial fairing.


Working down the aft scarf joint with the belt sander.



Same scarf joint after sanding and initial fairing.


View of the aft starboard scarf joint after sanding and initial fairing.


View of the forward starboard scarf joints after sanding and initial fairing.


Here she is today.

Next steps are to sand and finish fairing the entire outer face of the rubbing strakes. Then, trimming the rubbing strakes to width per station based on Keith Callaghan's drawings.


Until the next update... Fair winds and fun sailing!




Tuesday, September 30, 2014

September, 2014

The Rubbing Strakes (Continued)

Last month I fitted the forward and aft rubbing strake pieces on both starboard and port sides. Then, I scarfed the inner ends in preparation 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.

Next, I placed an 8 ft long x 120mm x 9mm rubbing strake piece against the starboard side gunwale. The curvature of the required rubbing strake piece becomes evident here. I placed the aft end of the rubbing strake piece against the end of the scarf of the aft piece and held it in place with a bar clamp over the side deck. Then, I bent the board around the gunwale and clamped the forward end the same way.


I left about 5mm of excess material over the deck on both ends. Then, I traced a pencil line on the rubbing strake right over deck line and under the  gunwale.





Here I'm holding the rubbing strake piece against the side deck and the beginning of the forward piece scarf to test the fit.

Unfortunately, it will require 4 rubbing strake pieces to do each side since the rubbing strake has to be at least 50mm wide from the edge of the deck.

Had I measured that requirement sooner I would've cut longer aft pieces or cut a board about 180mm wide by 9' long for the mid-section.



Once the lines are traced, I moved the piece over a temporary workbench to measure the width of the piece I'll cut and make sure it is at least 60mm in width (50mm + 5mm extra on top + 5mm extra on the bottom).


Using my band saw I cut along about 5mm off the pencil lines. Noticeable is the banana shape of the mid-section rubbing strake.

Dry run to test the fit prior to applying an epoxy resin with colloidal silica mix. Again, I use 1" scrap strips of 4mm marine plywood to protect the deck from the bar clamps. 

Front view of the clamping setup.


View of the clamping setup from underneath. Making sure the rubbing strakes are tightly held flat against the gunwale is critical to ensuring a tight joint with the top of the deck and the bottom of the gunwale.


Before fitting the rubbing strake permanently to the gunwale, I apply blue tape along the edge of the deck for protection.

Inside the boat, my cedar timber counter weight to offset the weight of the clamps while I'm working.

All clamps on deck!


Over the inner edge of the side deck, I place the scrap strips of plywood for protection.


And here is the view from down under from the rear.



This time the view is from the front.



Next, I followed the same method on the port side.



Another view of the port side from the front. The second time it goes a lot faster.


And the port side view from down under.


For the last piece on the starboard side I used again the 4" x 4" cedar timber over the forward deck to clamp the bar clamps from for the counter torque technique and hold the rubbing strake piece tightly against the top edge of the deck.


View from the front...


View from down under... I used small clamps to ensure the scarf joint was held tightly during gluing.


Same process was followed on the port side.


Thank you for visiting my blog! Happy sailing!















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!