Basalt Fibre for Boat Building
Bang! Crack! Two deafening sounds – a 457 Magnum firing and the bullet hitting a Haines Hunter V19R transom. The big slug pierced the thickest part of the legendary boat and finished up in the layers of sandbags stacked behind, leaving a very neat hole from the high velocity bullet.
I’ve done plenty of boat tests in my career but this was the first that involved a large-calibre weapon. But we weren’t testing the boat; rather we were investigating basalt fibre with the crew at Melbourne-based Nautek Marine, and to be honest it was a real eye-opener, not to mention a load of fun!
Basalt fibre is made from a special variety of basalt rock with high silica and low iron content. First it’s washed then melted at about 1400C before being extruded through fine perforations to produce an extremely strong yet flexible material similar to fibreglass. Its strong and fireproof properties make it ideal for a number of applications, particularly as a textile for the aerospace and automotive industries, and it can also be an asbestos alternative.
It’s claimed to have excellent specific strength, three times that of steel, and Michael from Nautek says it may have properties up to 10 times stronger than fibreglass.
Basalt fibre isn’t new – it was first produced nearly a century ago – but its use in boat construction is a recent application.
The fibre can be produced in many forms but for boating they’re manufacturing rovings for mat, multi-axial woven cloth and even chopper-gun applications that are bonded with resins in similar processes to conventional fibreglass production. It’s relatively inexpensive considering its advantages, especially when seen as part of the overall cost of the end product, and doesn’t require any more training so it can be laid by anyone with basic laminating skills.
READY, AIM, FIRE!
Our testing regime was pretty simple. We had three units to shoot. The first was the 19R. As described, the bullet went through the transom of the old hull easily and lodged in the sandbags.
The next test was to see the results at the same range with a test panel of basalt fibre laminated with polyester resin. The panel was laminated around 40mm thick, with many layers of woven basalt rovings, and the result was the bullet barely pierced the pad. It left a small indent on the surface and appeared to have penetrated the outside layer only, without fracturing the surrounds. Impressive but it was a solid panel of material, unlike the composite lay-up in a boat.
The more conclusive test was on a centre console manufactured entirely from basalt fibre. This construction was similar in laminating process to a fibreglass boat – one layer of 200gsm standard weave, three layers of 780gsm tri-axial basalt followed by two laminated layers of 20mm structural foam, two more layers of tri-axial, one of standard weave and then the flow coat.
YA GOT ME!
The result was amazing. The bullet barely pierced the laminate, similar to the basalt test sheet. The gelcoat shattered, as did the first layer of 200gsm basalt, but there was only a small indent in the next layer and that was all! The entire indent was approximately 3mm into a transom of around 70mm combined thickness with no obvious outward or inward shattering or penetration. The bullet simply bounced off.
History may well have been different if Ned Kelly had used a basalt suit of armour instead of steel. The results were quite conclusive for this test, leaving no doubts over basalt fibre’s impact resistance and overall strength. It will be interesting to keep an eye on the boat in years to come, but I can guarantee you I won’t be around long enough to witness its demise!