JP Macquet of JPM Shipwrights Pty Ltd was contacted by the owner of an MX2 aerobatic plane (as used in the Red Bull Air Race) who had some issues in assembling his aircraft. An air scoop had been incorrectly fitted into the carbon nomex cowling under the engine, resulting in the majority of the centre section having to be removed, and the realisation that a big mistake had been made.
The brief to JPM Shipwrights in Cheltenham, Victoria, was to repair the centre section of the engine cowling back to original and fit a new air in-take.
JPM Shipwrights made contact with the original manufacturer of the aircraft in the USA to obtain some specifications on resin and laminate.
To re-create the cowl section, a foam plug had to be fabricated to fill the hole and then a mould taken off to make the part. After the foam plug had been faired with Technifill XP and epoxy-coated, a mould was made using a high temperature vinylester resin.
The challenge was that the repair needed to be manufactured with a resin that was stable up to 1070 C to withstand the heat generated by the engine. Technical Manager, Mac Dalton recommended ATL’s Technirez R2519 high temperature tooling epoxy for the application to provide excellent high temperature performance after post cure and stability up to 140oC
The hole was prepared carefully and trimmed precisely prior to the outside skin being laminated and installed into position under vacuum. The nomex core was then fitted and vacuumed, followed by the inside carbon reinforcement.
With the initial cure complete, the next stage was post cure to obtain the maximum mechanical performance. This involved a ramp up of 10 degrees Celsius per hour up to 120 oC. With an ambient temperature of 25oC, it took just over 9 hours to reach full temperature, followed by another 24 hours at full temperature. The process was continuous over a 33 hour period.
The result was a very satisfied customer, and a cowling repaired back to original specs. A certificate of airworthiness was issued after the repair was completed.
JPM Shipwrights Pty Ltd
www.jpmshipwrights.com.au
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