Growing

We now have an opening for a composite fabricator/shipwright.

Our workload is growing so we would like to take on another team member.
Projects include UAV airframes, customer parts, RC yachts, and our A Class catamaran.
A good mix of one-off prototypes for R&D, and production items.

If you possess skills in carbon fiber pre-peg construction, with an aerospace or marine background, and would like to join a growing team working on interesting products, contact us by email: info@carbonicboats.com

Tamahagane

Another symbolic milestone: the last batch of Katana Marblehead hulls from the existing tooling is here.
The old moulds have been 'retired' and work will begin soon on updated tooling.
Deliveries are expected to start again in mid 2015.
Get in touch for more details...

While You Are At It...

Katana M in orange Durepox

A Different Look

Some quick snaps of the last shell just out of the mould.
We are building a series of 10 Katana Marbleheads using a special hybrid cloth.
The red bits are Kevlar.
No change in structural properties, just a different and unique look.
We will keep the boats in stock so grab yours today!

Digital Age

The first batch of our new Swing Rig Blocks. They come in three different 'flavours' to accommodate different main boom angles for different clew heights between suits.

As our regular followers know, we are always passionate about sharing lessons learned in development and explaining evolving methodologies.

For Katana we engineered and prototyped moulds for making integrated main and jib booms over a short length of 14mm ID carbon tube. The booms were then cut out of foam sandwich such that the core was in the vertical plane. The skins captured the piece of tube which effectively replaced, and created a bulge in, the core around the intersection with the mast. The 14mm ID tube that formed part of the boom/yard moulding would then be bonded to the outside of the mast tube.

Even with well thought out moulds this would have been a relatively labour-intensive approach. The result had good structural efficiency in the boom section but required considerable reinforcement around the junction area, offsetting most of the gains. Windage was marginally higher but the deck sealing effect could be maximised as the booms could be cut to exactly follow the foot droop permitted in the rule.

So we revisited an old solution that seems to have been abandoned due to an irrational preference for the latest material over an objective analysis of suitability for the application.
The difference today is that CNC milling allows exact replicability without expensive fixtures.
Most importantly, the penalty for adding complexity is considerably less than for manual processes (including laminating carbon fibre).

After several iterations, our late stage prototypes use aluminium in the high stress junction area where it is desirable to react the forces on the boom and yard over the shortest possible vertical distance to keep the mainsail tack close to the deck.
Carbon tube is used for the boom and yard as this provides an excellent compromise between stiffness, windage, ease of assembly, and cost.
Being machine laminated, tube has good consistency and, being round, it allows efficient attachments and adjustment systems.

Previous similar blocks by other manufacturers did not incorporate angled main boom connections so the boom was usually either made from bent aluminium (heavy and flexible) or required an elbow somewhere along its length (structurally inefficient).
With the correct angle machined in, efficient straight booms (cylindrical or tapered) can be used.

FEA allowed us to take as much weight as possible out of the part and hard anodising ensures good resistance against corrosion. Different colours are also possible.

Stay tuned to see the parts at work on our Katana test boats.

Glossed

The process and resin we are using for our Katana Marblehead are optimised to obtain the best ratio of resin to reinforcement fibres.
In practice this means minimising the amount of resin that cures around the fibres which are themselves a fixed quantity determined by the weight and number of layers of carbon fabric put into the moulds.

The hull and deck skins are vacuum bagged to draw out entrapped air and any resin that is not closely in contact with the fibres.
The upside is a stiffer laminate because the matrix is effectively more tightly packed with reinforcement.

It also means that the fibres appear extremely close to the surface of the finished material simply because there is no surplus thickness of transparent resin to give the visual effect of 'wetness'.
This is what modern composite parts look like. It is a sort of satin finish with perhaps a utiliterian or militaristic 'stealth' quality to the surface finish.
It is interesting that the actual surface is smooth and glossy, replicating the mould surface which in this case is CNC milled then polished to a high gloss and waxed. However the gloss has no 'depth' because the fibres are densely packed microns below the outer surface.

For those who prefer the 'old fashioned' glossy look showing off the fibres encased in an amber like transparent glossy surface, we offer the no cost option of a tough polyurithane varnish which is applied by specialists at YachtMod.
The aesthetic coating is kept as thin as possible thus minimising the associated weight penalty.

As always, the choice is up to the individual. Some prefer one look and some the other. Some want to save every last gram and others are willing to sacrifice a tiny sliver of weight for the sake of beauty. It must be said that the difference in performance is too small to measure so either option should be competitive.

The varnished option offers the possibility to wet sand the boat periodically which is considered good practice by most skippers. Cutting the surface back with 1200 or 2000 grit paper can get rid of any scratches that may accumulate with use and decontaminates the surface from any dirt or oil.
If done correctly it leaves a low sheen (yet another look) that allows water to form a thin coating over the surface without beading.
There is an argument that this characteristic prevents air bubbles from sticking to the surface and acting as trip-turbulators thus possibly delaying the transition from laminar to turbulent flow until somewhere further aft.

However if conditions are sufficiently rough to cause enough pitching to introduce air onto surfaces below the waterline, then the oncoming flow will be turbulent anyway.
Specific tests on this aspect of boundary layer behaviour are few and in my opinion inconclusive.
As long as the surface is smooth and free of contaminants such as road film or dust, drag will be close enough to the practical minimum.

Volume distribution, foil shape, rig positioning, weight distribution, stability and sail trim have effects greater by orders of magnitude.
In a tight class sailing skill will be the key.
The design that best complements the class rule and can be sailed fast with greatest ease will give the sailor the winning edge.

The New Black

Katana Marblehead specimens just out of the moulds. More to follow shortly...

Production Line

Some images of Katana Marblehead tooling coming together nicely...

Busy Times

Progress continues on RM tooling preparation in the workshop.
In the office the A Cat design is approaching completion.
R10R and IOM developments are in the pipeline and consultancy work continues on aerospace components.

Wax On... Wax Off

Progress on RM tooling: Plugs/patterns have been delivered, now preparations begin for taking female moulds.

In the Metal

Katana appendage tooling machined directly as female moulds from solid metal...
The fin incorporates additional drought so it will be suitable for larger boats such as 10 Raters.
It can also be adapted for classes with restricted drought such as the IOM.
The lower Reynolds Numbers characteristic of IOM class boats makes it advantageous to use the top part of the fin mould, keeping the trunking design common.

Initial coarse passes shown. The machine will then return with progressively finer steps down to less than 0.1mm. The only final hand finishing required is a very light sand and polish.

For such small, shallow, rigid moulds that can be made directly as female tools, the investment in more expensive and slower to machine materials is warranted. 

The step of laminating a female mould from a pattern is eliminated and the final tooling will be capable of withstanding high mechanical pressures and elevated temperatures to produce very compact laminates.

Bulb mould also shown at coarse stage (below). The plate that will form the fin cavity is visible on the left. Pouring hole for the lead and vent holes fore-and-aft are visible on the right.

These shots also courtesy Alex Kryger, Aptec Composites.

Shiny

Progress continues at pace on Katana M hull and deck tooling...
Images courtesy Alex Kryger, Aptec Composites.

Katana Deck Layout

As work continues on tooling, the new deck shape is now visible.
A good opportunity to share the thinking that led to the chosen layout.

Initially a dedicated RC tray moulding was designed with the aim of locating the mass of winch, batteries and servo as low in the boat as possible and close to the LCG to minimise pitching.

Discarded RC tray moulding design

This solution had drawbacks that seem to be accepted in most existing designs but we thought we could eliminate:
- Dedicated un-reinforced openings in the deck would be required for access, sapping stiffness (or requiring reinforcement in the form of lips or additional laminate that would add weight only to restore the stiffness lost by cutting the openings in the first place).
- The openings would have to be very large if the tray were to be glued into the boat after hull and deck were moulded together.
Even if the size of the openings were minimised by separating them into the three functions (winch, batteries and servo), the tray would not fit through any of the holes.
An option was to create three separate trays. However, because each would have to be larger than the hardware it must accommodate, opening size could not be optimised.
Being unable to drop the tray in through the access openings would have closed the door to one-piece moulding of hull and deck as a unitary laminate.

The lateral solution was to suspend the RC gear in dedicated wells moulded into the deck.
An important design constraint imposed when exploring this solution was to maintain the same low centre of gravity for winch, battery and servo.

The radius into the wells actually adds stiffness to the deck, complementing the inherent rigidity of the chambered shape.
Separate patches over each opening facilitate access and improve watertight integrity.

Another choice that will enhance ease of access is the re positioning of the sheet fairlead to the foredeck.
This solution also simplifies the sheeting run and has secondary advantages such as the elimination of a sheeting post, reduced likelihood of entanglement with other boats, and more direct transmission of sheet forces into forestay tension.

Katana Tooling Takes Shape

From virtual to reality.
The magic is being worked by Aptec Composites.
Images courtesy Alex Kryger.

Hull plug/pattern (above) and deck plug (below) machined ready for surface finishing.

Notice the bonding flanges for mast tubes and centreboard case, as well as all deck features, integrated in the tooling to ensure accuracy and repeatability.
The mould flanges and locating features to close the hull and deck mould together are also machined at this stage.

There is an interesting tradeoff between material cost and the expense of surface finishing.
In the case of larger simpler shapes we found it more economical to use an easy to machine stable but comparatively low cost material and go through the process of sealing and hand finishing to get the required surface finish.
Smaller and more detailed tooling will be machined from metal or plastic, requiring only a final polish after fine machining.
Where the parts must be made at high temperature, plastic plugs will be used to make female moulds in the same material as the eventual parts.