Birdy II Yacht

Construction

The only model yacht plans I have was the PANACHE, now held together with cello tape, so it became base camp. From my experience of sailing Blue Boat I wanted a more stable model, especially if it was going to carry electronics and sail on larger lakes. I am aware of Universities building autonomous yachts to sail on the open sea, but that was beyond my budget. Panache MM1299, Product Code 21052 @ myhobbystore.co.uk.


The easiest way to make the boat more stable was to make it bigger. So my objective was to scale-up the plans to be twice the size, twice the length & twice the width. Compared to Sun Sail yachts, Blue Boat was fairly narrow and thus heals over. All yachts clearly heal, but to make the proposed boat more stable I decided to scale-up the plans to be 2.5 times the width. Pressing a few buttons on a Scanner and folding the plans in several directions, produced the A3 plan I required. Compared with the aerial view above the boat below is clearly wider, less of an ocean racer now.


Once the Plywood arrived from Wickes I proceeded to cut out the bulkheads and backbone from the A3 plans and having drawn around the plans then used a jigsaw to cut out the pieces. The bulkheads were slightly altered from the PANACHE plan to have cabin superstructure. The initial assembly is shown below.


Chine and Inwale

The next task was adding the side stripes of wood. This step of the construction uncovered the curves of the yacht. Starting from the bows the strips where nailed into the bulkheads. The stripes bow naturally and uncovered some bulkheads that needed to be re-cut.


The next step was to add the Lead Flashing. After several discussions with colleagues at work the final design of the keel will be hence known as the Johnny Glassock keel. Lead is poisons and so wearing washing-up gloves I cut out sheets of 3mm lead in the shape of the keel. The outer sheets were cut slightly shorter to create a curved effect on the keel. With all the lead sheets cut out I then proceeded to weigh the total. It came to around 8Kg on the bathroom scales. Knowing it would be easier to add ballast than to take some away I proceed to hammer nails through the lead sheets and nail them to the 9mm Plywood keel.


The next step was to add 3mm width Balsa Wood to the sides. Balsa wood thinner than 3mm would inward bow between the bulkheads and Balsa thicker than 3mm was harder to bend to the shape of the hull. A skilled craftman would have spent time cutting the Balsa Wood into strips and beautifully layered the strips to form an attractive hull. My approach was rather faster and less eligant but adding Balsa sheets. My reasoning was that my interest and challenge will be in the electronics.


Fibreglass

The boat required being more solid than having balsa wood sides and thus I decided to cover with fibreglass. Fibreglass fabric comes in several weights per meter squared and I decided upon 125 grams per metered squared.


The glue, Epoxy Resin comes in two containers. One container is 5 times the size of the smaller one. Using the supplied pumps they correctly get the ratio 5:1 correct as the combined mixture is added to a Budget Calibrated Cup, or more simply a plastic cup. I then used the supplied brushes to soak the Balsa wood, lay the fibreglass fabric, and then coated with more mixed resin and left 24 hours to dry.


Once dry the boat was turned over and using a knife the fibreglass ends were cut to make a smooth top. A small piece of Fibreglass was added to cover the stern.


First Lake Trials Aug 2011

The boat was starting to become heavier with fibreglass, resin and an 8 kg. The burning question was, is it too heavy? So before the boat was 100% water tight a quick visit to a local lake would give results. The home bath was too small for the boat. Even adding 9 kg of bottles of water, she still floated above her final waterline, a good result.


First Lake Trials Aug 2011

Low Density Filler

Happy the keel was not too heavy, I proceed to mix some powder, low density filler, to more mixed resin. The mixture was spread thickly over the fibreglass, forming an additional shell and watertight layer. Then using wet and dry sandpaper I started on the lengthy task of smoothing the hull surface.


Sanding down with wet-and-dry was taking a long time with no noticeable improvement in the smoothness of the hull. My attempted solution was to use Spray Putty. Spray the boat in yellow paint and then sand smooth.>


Second Lake Trail Nov 2011

Back at the lake of my childhood for the second sea trial. The trail was 100 percent success, namely a long piece of string and no leaks.


The Rudder

Off the shelf rudders available at Model Shops were all too small for Birdy II, I thus had to construct one myself out of an aluminium tube, copper tube and some plywood (shown below). A grove was cut into the plywood and the copper tube hammered in, forming a tight fit. The final rudder then has fibreglass on both sides to solidify the structure.


A rudder clearly creates a hole in the boat. In order to avoid sinking the aluminium tube was cut sufficiently high so that the top end remains above the yachts waterline. The top of the copper tube was filed down until the servo rudder tiller could be fitted (shown in the bottom photo). The aluminium tube was given additional support by fibreglass.


Motor & Propeller

I decided upon the Graupner Speed 720BB Torque.


Deciding on the correct motor size for a model boat appears to be partly experience and partly an art. I basically had none but I did have the 2011 Model Boat magazine construction special issue where several model motors were reviewed.


The propeller was another decision. I decided on the 40mm M4 Threaded 4 Blade Right-handed Brass propeller. The prop-shaft was a Fine Line 18 inch M4 Thread, Stainless Steel rod. The interior end of the prop-shaft was fitted sufficiently high above the yachts waterline to minimise the risk of leaks.


Third Lake Trials

Now with the motor working, the next challenge is for the software to correctly control the servos. With a 50 meter length of string attached the Birdy II performs her exercises.


Lake trial

Lake trial