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Matrix (A-Class) Build

This blog is dedicated to the step by step construction of the ‘Matrix’ A – Class yacht. This is hull two from this radical design first seen in 2018. Numerous changes have been incorporated within this version, after many lessons were learnt from the prototype’s launch. I invite you to follow Damian Ackroyd’s progress as he constructs the latest version of ‘Matrix’.

Dimensions: LOA – 2000mm / 78.5in Beam 300mm / 11.78in Displacement 14.5 – 15kgs / 32.6 – 33.75 pounds. Sail Area 918028mm* / 1400+sq/in

To give everyone some background to this project, can I first give thanks to Ray Baker, Gosport MYC. He has spent many weeks in his workshop interpreting my strange ideas when constructing the two wooden plugs for this design. His workmanship and patience have been first class.
Hull 1 was built through the winter of 2017. As you can see there are a lot of hollows below the waterline. This ultimately created problems as the water flow ran along the underside of the hull, effecting sailing performance these hollows were producing unwanted turbulence which reduced speed. So it was back to the drawing board to rectify this and other issues.
Hull 2 was then built in 2019, this time the underside of the hull was more of a traditional shape. However, alterations within the stern bustle areas were made, which smoothed off the water flow from the main body to the stern overhang. With this and other amendments to Matrix, we hope to achieve a difference in performance. Now to read below moving forward after the moulding process.

Health and Safety
Ensure builders use a full face mask, eye and hand protection when working with epoxy and carbon. No if’s and No but’s.💀 A well ventilated working area is essential when sanding or cutting material. Personal Safety is of paramount importance at all times. Ensure you do not transfer harmful substances from your place of work to your home. 💀

1. Keeping the hull square from the outset
Wooden beams are temporarily glued in place across the hull. This is to ensure the hull remains at the correct beam measurement and to keep the hull square whilst working.
Tape is used to mark all the key areas such as the mast and keel positions. For a vane boat, tape is also included at the stern, for the positions of the rudder tube and pintle.

2. Join the hull along the fence
When male moulding a yacht hull, you only have one join running down the centre of the deck. Prior to moulding a metal fence is attached to the wooden plug down the centre line. When varying layers of cloth are draped over the plug and wetted out with resin, the cloth is then cut back to half way up the fence. If you didn’t use the fence method, the cloth would simply crumple up against itself or overlay each other, when the two sides of cloth meet in the middle. The use of the fence allows the cloth to keep its true directional shape. Once the moulding has cured the builder can then carefully pull apart the two sides of the hull with ease. This releases the moulded hull from the wooden plug. Tape is used on the inside of the join along with a piece of ‘Peelply’, this ensures the tape stays in the right position to give the builder a smooth even finish.

3. Chine reinforcement
Due to the design of ‘Matrix’ incorporating a chine, the hull will require some reinforcement in this area. As a future vane yacht, it is likely during its competitive life, scratches and minor damage will appear over time. 😧 Adding a strip of tape will strengthen the area of concern along the chine.

4. Joining fence removed
The ‘Dremel’ is a wonderful and very versatile tool. BUT be careful and ask for help if you need an extra pair of hands to hold things steady. Cut and sand the fence away.
Normally keep a 15mm wide flange around the complete deck edge of the hull. Be aware as the builder you may experience some minor issues, there’s always something that may catch you out when working on a new project. The deck area of the plug may not be strong enough to keep its shape when put under vacuum. As a result, the builder may see along the moulded deck flange, some ‘sagged’ in a few places. Annoyingly in this case the uneven parts of the flange are mainly where the deck centre section would be positioned. Therefore, the builder will have to increase the cut further into the flange, a distance of 7mm from the hull in this area would be acceptable. 🙄

5. Digital parts printed
For ‘One off’ parts digital printing is ideal for such items like fins and mast tube mouldings. These items are printed rather coarse to allow better bonding when fixing to the inside of the hull. The fin is printed so a 10mm diameter carbon tube is allowed to pass through the entire length of the fin. The inner wall of the fin and the carbon tube provide strength, once a 6mm stainless steel rod is inserted. The 6mm stainless steel rod runs from the lead ballast, through the fin and hull, fixing in position through the deck to a securing nut. Skippers usually switch the top securing nut into an eyelet, which allows the skipper to lift the yacht out of the water. As for the mast tube mouldings, a plate with a series of holes is made. The holes represent the position of the mast, by inserting a pin at the bottom of your mast, the skipper may move the rig fwd / aft. The rig is then located to a new fixed position as required, in relation to the holes within the bottom plate.

6. Fin and Rudder positions
Mark the centre line of the hull for the fin location. Holes are then drilled through the hull to indicate the fore and aft positions of the fin, an additional hole is then drilled for the carbon keel bolt tube to be inserted. (The cutting of the slot for the fin comes later in a future paragraph). From the deck, a carbon beam is temporarily fixed in position over the keel. This allows for the keel bolt tube to be passed through the hull and the deck beam, whilst ensuring correct alignment is carefully maintained with the hull in all respects. To position the rudder, another carbon beam is temporarily fixed towards the after sections of the deck. Holes are carefully drilled both at the centre line through the deck beam and on the underside of the hull. This enables the rudder tube to be passed through the hull and through the deck beam. It is paramount to ensure the hull is square during this procedure, and to ensure the correct alignment of the keel and rudder tubes is maintained.

7. First deck beams inserted
In addition to the keel bolt deck beam being fixed into position, extra pieces of carbon plate are glued to the underside of the deck flange. Supporting a thinner deck flange because of previous’sagging’, the extra carbon plating strengthens this area of the deck. Additional deck beams in the central area of the boat, such as for the main sheet post can also be glued into position. Ensure all beams are of the same height as the surrounding deck flange, this will make a neater finish when putting on deck patches later.

8. Central deck plate
The central deck section is cut from a flat piece of carbon sheet. The mast box and fin are layed out on the central deck area, to show the correct positioning and to check alignment. Holes are then drawn before drilling through the deck.

9. Keel bolt and mast box fitted – dry fitted only
The keel bolt tube is the first to be fitted, next the mast box is inserted. A short piece of 14mm CF tubing comes in handy. Ensure all structures are checked for alignment prior to fixing.

10. Keel wrapped in carbon
The digitally printed fin has been wrapped in 2 layers of carbon cloth. Just like the hull this is done using the vacuum bag moulding technique. The vacuum bag moulding technique squeezes excess epoxy from the fin, which in turn produces a light but very durable fin. Other structural parts can be made in this way and at the same time if required.

Important: Watch the temperature when working with plastics and resin.
For those builders thinking of digitally printing parts like fins which require wrapping in carbon. Depending upon the type of plastic you are using, ensure you know its operating temperature range. PLA will start to soften at around 45°C, while ABS at 95°C (approx). Combine this with the exotherm from the resin, you don’t need a high temperature within your heat box for these parts. Using a fast hardener in the resin, this will produce a perfect part under vacuum at 25°C for 2 hours. Anything hotter and the plastic will start to sag and distort when under vacuum.

11. Hull floor reinforcement
The areas where the mast position, jib luff box and main sheeting post all connect to the bottom of the hull will require added strength. Placing a few strips of carbon tape in these areas will provide a robust platform, this is because of high downward forces from the rig will be experienced in these areas of the hull. Remember to place a piece of ‘Peelply’ on top whilst drying, this prevents sharp edges and keeps the surface smooth.

12. Fitting the fin and mast box
As mentioned in paragraph 6, carefully cut a slot in the bottom of the hull for the fin. It is of paramount importance to check your alignment from the stern, through the rudder, fin and bow. Ensure also the fin is vertical and not twisted. Once you are satisfied you have the correct alignment, tack in place using epoxy between the hull and fin, when this is dry do the same for the mast box and other structural pieces.

13. Deck plate glued in place
Moving up towards the centre deck section, apply plenty of epoxy to the area of the hull flange and deck beams, offer the centre deck plate to the hull and hold in place with clamps. Again check for alignment.

14. Bond the fin and mast tube to the hull
Once the epoxy is cured from the centre deck section, permanently fix in position and hold the mast box in place. Additionally, tape is used at the bottom of the mast box and fin to the hull. I prefer to place a piece of cloth at each end first, ensuring it drapes around the forward and after ends of the fin within the bottom of the hull. Then to place a piece of tape along the sides of the fin, mast box and over the top of the extra piece of cloth as described in paragraph 11, this provides additional strength at the fin position. Then place ‘Peelply’ over the join to ensure no sharp edges.

15. Bond the top of the mast box to the deck
Finally bond the top of the mast box to the central deck section from inside the hull. Place masking tape around the outside of the join to ensure epoxy does not escape. Use ‘Peelply’ in this area. The time to remove the masking tape will be approximately 2 hours, just as the epoxy feels ‘tacky’ but no longer like liquid. This will make removing the tape easy in close proximity to the join.

16. Bow and stern
The bow and stern will be made from a piece of balsa wood sanded to the right shape and inserted from the inside of the hull. (Future production hulls will have moulded carbon pieces). Using 10 minute epoxy the bow will require pressure placed evenly on each side, be careful not to create twist when inserting these pieces. Additionally a long piece of rod is placed inside the hull and by applying pressure against the shaped balsa, this will ensure the bow does not move. The transom is created in the same way but held with clamps. Once the balsa pieces have cured, sand the ends perfectly square.
Afterwards place a slightly over sized piece of carbon sheet over each end. To ensure there is an even amount of pressure to the bow and transom, use a small piece of wood to help spread the pressure across the area and firmly tape in position. Ensure to cover the balsa inserts with carbon cloth on the inside. This provides extra strength and waterproofs the balsa should water ingress happen in the future.

17. Luff rod box
The ‘Matrix’ uses a sail plan which incorporates a ‘J’ measurement of 500mm. (This represents the size of the jib on the boat, distance from mast to luff rod).
As this is the first hull from this version of ‘Matrix’, we require plenty of rig adjustment forward and aft for the mast, as such the same adjustment will be required for the head sail luff rod. Working out the minimum and maximum angles of the luff rod, given the varying positions of the mast determines the size of the luff box required. The luff box was moulded in carbon, thicker at the base where stainless steel pins would carry the load of the head-sail luff rod when sailing. When you change down to smaller sails, more of an angle for the luff rod is required at the rear of the box.

18. Luff rod box bonded to the hull
Trial fit the box with dummy rods to ensure correct alignment to the mast. Again temporary fix with quick drying epoxy, helps to hold the box in place. Tape the bottom of the luff rod box to the hull and when this is cured do the same to the underside of the deck, in exactly the same way as the mast box in paragraph 15.

19. Trim all boxes and rods at deck level
Trim the mast box, luff rod box and keel bolt tube to the same height as the deck. Along with the central deck edge to the hull flange. These joins should all be sanded to a smooth finish.

20. Fill any gaps on the deck area
If you have any gaps use a bit of filler and sand back. Better to use too much than too little – easier to sand back the filler in one go than to keep building up and then sanding back.

21. Keel fillet
Incorporating a keel fillet enables better water flow from the hull to the fin. Build the keel fillet up with small bits of filler in stages. Sand down to shape with a smooth finish.

22. Protect inside of hull prior to priming
To protect the inside of the hull from primer and paint, tape bubble wrap or paper to the inside of the hull.

Slightly out of sync
The skeg and rudder should be produced and installed at this stage prior to priming. But due to other builds and the good weather outside, it was decided to prime the majority of the hull (leaving the skeg and rudder area clear for building later).

23. Prime the hull
When it comes to painting the yacht, start by brushing high build primer on the outside surface of the hull, include the sides of the deck beams. 3 coats will enable all cloth to be covered – as a rule of thumb if you can still see the weave of the cloth you need to put another coat on. Most will be rubbed down later, too much is better than not enough.

24. Skeg & Rudder
Both the skeg and rudder were digitally printed and wrapped in carbon prior to fitting to the hull.
Note. The recess at the rear of the skeg is to allow the water flow to run smoothly from the skeg to the rudder.
Alignment is checked again before tacking in place with a few drops of epoxy.

25. Rudder shaft and movement check
The rudder shaft was fastened to the back of the skeg and the alignment checked in comparison to the rudder. To allow the rudder stock space and be positioned close to the skeg, a small piece of the skeg at the rear was removed. A further check for clear rudder movement as well as alignment in the longitudinal and transverse planes should be carried out prior to fixing.

26. Fitting the Skeg
Tape around the outside of the joint just like the fin. Apply resin and tape to the inside of the hull with a piece of peelply on top. Remember to remove the tape on the outside as the resin becomes tacky. Repeat the process to the top of the skeg and the deck joint.

27. Skeg Fillet Extended
Extend and blend in the skeg to the hull with a bit of filler. Sand the area smooth and cover with primer paint as per the rest of the hull.

28. Tiger stripes
To aid the rubbing down process, apply some black aerosol spray to the hull just like tiger stripes. When we rub the primer down flat with wet and dry paper it becomes hard to see if you still have hollows. The black spray will enable you to see the hollows much easier. Sand the primer flat using a sanding block and 320 grit wet and dry paper. Use plenty of water and keep inspecting as you sand. If you start to work through the primer the water will start to turn black from the carbon, a little carbon is not a bad thing but not too much. Once you are happy that you have no hollows, a final rub down with 600 grit wet and dry will be the next step. Wash with clean water and inspect that you have no hollows. As long as you put too much primer on the hull in the first place you won’t have hollows, too little and you’re painting and sanding again.

29 Final Primer Sprayed
A final coat of primer is sprayed over the whole hull to ensure you have an even colour and base for the top coat paint to adhere to. If you don’t you’ll be using far more paint than necessary to cover the hull surface, especially with light coloured paints.

30 Sculpting the Bumper
Our bumpers are sculpted from foam which are fixed in position by epoxy. Firstly, place two layers of masking tape around the bow area. This protects the hull sides when it comes to gluing and sanding the bumper to shape. Once the bumper is fixed in position to the hull, quickly sculpt to a rough shape with a dremel sanding tool. Alternatively, you can cut with a fine saw, then sand to shape with a course sanding block, you must be careful not to rub through the masking tape on the sides of the hull. Remove the bumper from the hull by carefully sliding a knife blade between the bumper and the bow. Clean up any glue residue which may be left on the hull. It is better to do the dry fitting of the bumper while the hull is in primer, because you don’t want to catch the top coat of paint. Once the top coat of paint is applied and dry, then permanently fix the bumper back into position.

31 Painting the Top Coats – Sorry for the delay
I know several of you have been asking John when the next stages will appear, the simple answer is ‘lock down’ due to Covid-19′ has caught me out. Just before the pandemic I purchased enough paint to take me through the next three months, or so I thought. Originally ‘Matrix’ was going to be painted in white, but it soon became clear when looking at the hull in primer, the shape doesn’t really suit white. So the decision was taken to paint Matrix in blue, a colour unfortunately I didn’t have enough of it in stock. Once I have delivery of the right paint we will be back to finalising this build.

32 Painting the Hull
Our hulls and foils are all sprayed using 2-pack. Alternatively, you can achieve a quality finish by using a small roller and a set of good quality wet/dry papers, when it comes to rubbing the surface down at the end.

In this example once the spray paint is dry, you can rub the surface area with a fine 1200 grit paper, which removes any blemishes. Later move to a 2000 grit wet/dry paper for a smoother finish. Remember to use plenty of wet/dry and change the water as you swap to the finer grades. If using a roller then you may need to start with 600 grit wet/dry paper, but be gentle and take your time.
After a good clean with water, inspect the hull and remove any localised imperfections. This is done by using cutting compounds, which will bring the gloss of the paint back to the surface.

33 Fitting the Lead
We have been unable to trim the hull in the tank during lock-down, some fine adjustment in the positioning of the lead ballast may be required in the future, when achieving the optimised waterline trim. However, for now she’s ready to be passed to the skipper for the rig and the installation of the deck fittings and lines.

This completes Part 1 of this construction blog. Part 2 will start once ‘Matrix’ is ready to be launched and will feature the yacht during its trial.