Following my trip to the JEC exhibition in Paris, my eyes were opened to the huge possibilities available to composite engineering due to the huge range of composite fabrics available, in fact too much choice.
Anyone considering building a racing canoe is first faced with the decision regarding which composite fabrics to use, in what combination in with what type of resin. Once a working formula has been reached comprising of the right strength, stiffness, weight, complexity and cost, it is tempting to stay with unless there is a compelling reason to change. This may help to explain why kevlar, first invented in 1965, is still used in many boat constructions even though in the last fifty years, better aramid materials have become available.
In the secretive world of composite engineering, very little knowledge and experience is shared so most entrants to this business have to climb the same learning curve from scratch, as I have discovered since I first started.
The best way to find out what works best for my particular application would be to build a boat out of a variety of laminate combinations, test them all to discover the ultimate formulation, AND THEN DON’T TELL ANYONE! Something I’ve tried to change by publishing everything I do.
Over the years I have experimented with lots of different materials, but I can’t afford to build a boat according to all my new notions. So I approached Wessex Resins (my epoxy resin supplier) with an idea to build a Darkness C1 in four quarters, each made from two different types of fabrics to help illustrate what the differences were within a single finished product.
Wessex Resins were very supportive but extended the scope to include a second type of environmentally friendly resin called Super-Sap from Entropy resins. They also suggested using some plant based fabrics such as hemp and flax.
Both resins are epoxy and the resin infusion method was used to wet out the fabrics.
Finding plant based fabrics was not easy. There are very few suppliers and it is quite expensive but I managed to get some, plus some more unusual carbon weaves.
One side of the boat was constructed using:
- Entropy Resins Super Sap CLR resin
- First quarter: 200g plain woven carbon and 10oz Luxury Jute Hessian Burlap Fabric
- Second quarter: 200g twill woven carbon and 200g 2×2 Twill Biotex Flax Fibre
And the other side used:
- Wessex PRO-SET® Infusion epoxies
- Third quarter: 200g Plain Weave Carbon / Innegra and 240g FISH Weave Carbon fibre
- Fourth quarter: 180g Plain Weave Carbon/Kevlar® Hybrid and 193g Spread Tow Carbon Fibre
Rather than post a whole series of pictures, the method and results are captured in a video which I published on YouTube at: https://youtu.be/sktNXpsyTzk
You can see the resin infusion process and it highlights the sheer amount of time, materials and manpower required to make a boat in this way.
The video was created to go with the finished product, a racing canoe made from a variety of materials which was destined to be shown this year at the JEC exhibition in Paris, before the world got sick. JEC is the biggest composite exhibition in the world and is mostly dominated by aerospace and automotive products, showing high performance cars, boats and planes, so this was bound to be a show stopper!
As epoxy resin is not UV tolerant, a coat of polyester based gel coat was first applied to the mold. The first layer of reinforcement fabric was placed onto the tacky surface and rollered down. The epoxy infusion had to start whilst the gel coat was still “green” to ensure that it bonded.
One side was made using flax and Jute plant based fabrics, plus Super-Sap, an environmentally friendly epoxy resin. The other side was made using typical aramid and carbon type fabrics with Pro-Set epoxy resin from Wessex resins.
Rigidity is usually established using Lantor Soric ribs, but they were not used for this boat because the whole point was to show the difference in the four constructions.
The usual carbon weaves are twill and plain, but I thought I’d also use tow and fish weaves for a bit of fun.
As any composite engineer will tell you, there is no ultimate single solution because construction is based on a compromise across the main requirements of cost, complexity, weight, strength, rigidity and material availability, and many combinations of resins and reinforcement materials will meet these needs.
There is a lot of composite industry talk about more sustainable construction materials, but they have to be proven to be as good or better, cheaper, easily available and easy to use, and produce a finished product of the right quality and performance, and they’re not!
The boat has sat in Wessex Resin’s warehouse since it was built in the hope that one day it will be shown at a variety of exhibitions and help stimulate discussions.