Meet Graeme Wornes, the boat-building craftsman in the Shockwave workshop
With over 40 years’ experience in both aviation and marine industries, he’s an expert in the art of composites and vacuum resin infused fibre glass.
We sat down with Graeme to chat about the finer details of making hulls, cabins and other parts for our Shockwave catamarans.
We soon learnt that Graeme is a perfectionist, he loves problem solving and working out how to do the tricky parts or as he says the shitty jobs – it’s the true craftsman in him – and the key to our Shockwave Marine excellence guarantee.
What is the Vacuum Infused Process (VIP)?
It’s the method we use in the Shockwave Marine workshop – the same used to build aircraft and racing cars. Simply put, the resin is injected into the fibreglass laminate whilst under vacuum; the layers are not laid in by hand.
Why do you use this method and not the conventional fibre glass process?
VIP gives us a lighter, stronger boat. In fact, our vessels have significantly greater hull strengths and are 30% lighter in weight than conventional fibreglass boats. This directly impacts fuel consumption, cruising and maximum speeds, as well as improved handling and performance on the water.
On land, it also means the VIP Shockwave Marine crafts are more easily towed, with their fuel and kit, under 4.5 tonnes on a regular trailer. Craft of a similar scale but made using traditional fibreglass will need a trailer with air brakes and a truck to pull it.
The VIP advantage puts our boats in a totally different class – more boat, more efficiency.
Let’s dive in a bit deeper to understand the vacuum infusion process (VIP) better.
We use ‘vinylester’, which rivals the strength of epoxy resins and the usability of polyester resins, as it provides higher strength, rigidity, low shrinkage, and it’s more chemical and water-resistant than polyester.
Striking the perfect ‘resin to glass ratio’ is the secret to the strength of the hull.
When you laminate by hand, you usually achieve about two parts of resin to one of glass. So, one kilo of glass will take two kilos of resin to wet it out. With vacuum infusion, it’s one to one. One kilo of resin to one of glass is the perfect resin to glass ratio, which you can only get under vacuum, and which gives the lightest weight and highest strength.
We lay the glass layers into the mould dry. Then a layer of ‘peel ply’, which is basically a peel off material that goes over the top of the fiberglass laminate. The resin feed lines go on top of that. Then we cover down using a nylon bag over the top with double-sided tacky tape to seal the whole thing. A vacuum pipe feed is placed all the way around the outside, underneath the bag. Then we hook it up to the three-phase compressor pump which sucks the bag onto the laminate, extracting all the air.
The catalyst is mixed with resin seconds before it is fed in through the feeds to ‘wet it all out through the glass’. Once done, we close off the feed and let it cure overnight. The next day we pull off the bag and it’s all done.
Every single little void and gap in the glass fibres are completely filled with resin. Everything is done at once.
How does this compare to the hand process?
With the bucket and brush method using a hand roller, or a chopper gun to spray, and then rolling it, it’s easy to end up with air bubbles, if you are not an expert.
When a guy goes along tapping a hull, and knocks a hole in it – that’s due to air bubbles where the glass wasn’t rolled properly.
With hand layering you have to let each layer rest before laying the next, as the fibreglass heats up. If you go too fast it will affect the integrity of the whole laminate, maybe even melt your gel coat. When you progress in this step-by-step way, each layer cures at a different rate, which affects the integrity and strength of the end product.
Quality control is a lot better with VIP, it’s exact. But it has to be done by experts, otherwise you risk a mediocre product.
Doing all in one hit is much stronger. With VIP, we take the bag off and trim it to the boat.
Large boats are done in a couple of sections, but mostly we do everything in one hit.
You mentioned air bubbles. How do you ensure there are none?
Making sure there are no leaks during the vacuum stage is crucial.
When we bag up, we go around, before we inject the resin, to make sure we don’t have any leaks. If you have a leak in the bag, it will destroy the process. If there’s a pinhole, it’s sucking air into the laminate, and you don’t have a full vacuum.
We use an ultrasonic leak detector to monitor air movement and listen to the measurement with headphones. It is so sensitive it will actually pick up the air movement created by your eyelashes moving – any air disturbance – batting your eyes can be quite deafening!
How long does it take?
We vacuum on full for about one hour, then turn off the tap for about 10 minutes to see if it holds vacuum. If it falls there’s a leak. We are looking for the level to remain constant, at
29 inches of mercury, to verify that we have a perfect seal before putting in the resin.
Once you have confidence in the vacuum seal, the resin feed is pretty fast – sometimes you can fully ‘wet out’ a cabin and parts in 20 minutes. It’s left under vacuum overnight to make sure all is cured and firm. If you turn off too soon, the resin may be like jelly and the laminate will spring back out. Essentially, it is cured under vacuum in 12-24 hours.
VIP is such a clean process, people can walk around in pristine suits in the workshops where racing cars are made – maybe not in our workshop!