Uploaded 15 Jun @ 14:23pm
A team of 16 undergraduate and MSc engineering students from the ÉTS (École de Technologie Supérieure) in Montréal Canada has recently finished building ‘Rafale II’, an all composite C-Class racing hydrofoil catamaran. Rafale II has redesigned carbon fibre epoxy prepreg hulls and cross beams, which are stiffer, 25% lighter and provide 15% more displacement volume. The speed and handling of Rafale II has also been improved by designing lighter, stronger and better performing pairs of new epoxy carbon fibre L-foil dagger boards and T-section rudder hydrofoils, which provide a higher ‘Lift:Drag’ ratio and greater stability when hydrofoiling.
The first ETS Rafale project started in early 2014 with a relatively small budget. However, the students have benefited from the considerable support and technical advice provided from over 40 project sponsors. This included the Canadian composites materials producer Scott Bader North America, a key sponsor for both Rafale I and II, providing a variety of high performance composite resin, tooling and structural adhesive products, as well as technical support.
The new carbon fibre epoxy prepreg hull half sections were moulded by low pressure vacuum bagging out of autoclave (OoA) using heated tooling with a mould dwell temperature of 93ºC for 10 hours. To minimise weight, the two halves of the hull were then bonded together using Scott Bader’s Crestabond M1-30 structural adhesive in the second stage assembly process, as were the new carbon fibre cross beam sections; the beams were fabricated by ply winding onto extruded aluminium profiles using the same epoxy prepreg grade specified for the hulls.
The new L-shaped daggerboards and T-shaped rudder foil skins were moulded in the same way as the hull in two half sections using a carbon fibre epoxy prepreg, and then assembled around 3D printed cores using a structural adhesive. The assembly of the 25 ft long hull sections proved to be a real challenge for the ETS team, as the students had never bonded composites parts on such a large scale with no other fixings before.
Crestabond M1-30 was selected by the ETS team as the most suitable structural adhesive to bond the new epoxy carbon fibre hulls and cross beams due to a combination of its performance capabilities in use with no need for any mechanical fastenings, along with its processing characteristics, which enabled easier and quicker assembly by the team of six students compared to other adhesives trialled.
Unusually, Scott Bader’s Crestomer 1152PA urethane acrylate-based structural adhesive was also used in both the hull and the rudder and dagger boards moulds, primarily to eliminate sharp edged stress areas, especially in the thin foils and to prevent any dry areas or air inclusions in the corners during infusion; the curved radius corners also helped with fibre alignment and avoided any gelcoat displacement when the vacuum was applied during the infusion stage.
As well as the structural adhesive, Scott Bader’s carbon fibre compatible Crestapol high performance urethane acrylate-based resin was used extensively to manufacture key structural parts for the massive 300 ft2 wingsail; the leading and trailing edges, flap spars, wing foil box fairings and the bulkhead panels, were all vacuum infused using Crestapol 1250LV. The rigid bulkheads were assembled with Crestabond M1-05 and M7-05 structural adhesives, which were also used for bonding a variety of FRP and metal parts on the wingsail.
Further reading: www.scottbader.com
Ben Hayes – Sales Manager, CWST
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