Restoring traditional Whitby lifeboats
How boatbuilder and lifeboatman Mike Coates ensured the survival of two classic Whitby lifeboats
Mike Coates on the array of techniques needed to repair double-diagonal construction
In the late 1960s I joined the RNLI as crew on the inshore lifeboat and often made up the crew on board the a 41ft Watson Class vessel. She was a nonrighting twin-engine motor lifeboat built in 1937 by Groves and Gutteridge on the Isle of White and was at the time state of the art in lifeboats.
Thirty years later she was in poor shape and needed some fairly serious repair work, but her double-diagonal construction was a major hurdle and was threatening to be the death knell for this classic vessel.
My first foray into repairing double diagonal was from the same period in the late 1960s, repairing Firefly dinghies that were mass-produced using hot moulded double diagonal. The hulls were constructed using flexible 3mm thick wooden veneers laid diagonally over a fully battened building form and temporarily stapled in position. A second (and sometimes third layer) was then laid at approximately 90° to the first with a layer of glue between each. Usually the planking would start approximately midships with strips of veneer being butted each side of the initial strip. Once the layers were finished, the whole thing was covered over and fed into an autoclave to cook, creating a hard, light, durable shell.
A cry for help
The Mary Ann Hepworth entered service at Whitby on 11 April 1938 and remained on service at the station until 1974 having served for 36 years, launching 372 times and being credited with saving 201 lives.
After her decommissioning in 1974, she was sold by the RNLI and converted to a motor cruiser on the Broads and the River
Trent. Later bought by local lifeboat crewmember Barry Sneddon, she was restored as an open lifeboat and put into service as a passenger vessel at Whitby.
In 1999 I was saddened to hear she’d been damaged; rumours quickly spread she was beyond economical repair. Barry asked if there was any way I could help as he’d heard I previously repaired double diagonal hulls.
I explained my experience had been limited to glued double diagonal hulls and that the Mary Ann was built with nailed double diagonal planking, but I was his last hope of finding someone to repair her locally. Having examined the damage, I believed I could carry out a satisfactory repair using layers of veneer. But there were plenty of hurdles still to come.
Initial repair difficulties
Unlike the double-glued veneer construction of the Firefly, the Mary Ann was built with an inner plank of 8mm Brazilian mahogany, a layer of calico cotton soaked in white lead/linseed oil mixture and an outer 9mm mahogany planking. The two layers were then fastened with three rows of copper nails and roves at approx. 50mm (2in) intervals. The calico and white lead mix provided a flexible waterproof membrane between the two layers of planking.
However, as a passengercarrying vessel, any work on the Mary Ann had to be overseen by the Maritime and Coastguard Agency (MCA). They insisted on full-length plank repairs from gunwale to keel not only making the repair complicated, but also prohibitively expensive. I asked for an on-site meeting with the surveyor, who reiterated his repair recommendations. His view was that it wouldn’t be possible to bend (even steam bend) short lengths of planking into place without causing stressing at the end of each plank and that this stressing created the possibility the joint wouldn’t lie flat or may even open up in use.
Additionally the surveyor insisted that I use a traditional non-setting oil-based mastic between the planks – which immediately put gluing out of the question.
During our somewhat frustrating meeting I explained my plan of attack: I was hoping to use multiple layers of veneer to make up each plank thickness – 3x3mm for the outer plank and 2x3mm and a single 2mm for the inner – with each layer glued with epoxy. In my opinion this would allow the contour of the original planking to be formed with very little stress within the new plank.
While he accepted the virtues of laminating each plank he wasn’t happy about me using epoxy, suggesting it would create a hard spot on the hull and would cause a problem where the repair joined the original hull structure. However, he did eventually concede that a flexible adhesive might work.
My thoughts immediately went to Sikaflex, but on seeing a tube of black Sikaflex 221 he rejected the idea on the grounds that a polyurethane sealant wasn’t a suitable adhesive. So I was left to submit a number of glued veneer samples for destruction testing; these were made up using Sikaflex with the addition of Sika Multipurpose primer, but this time I used white! The samples were supplied with planed edges showing the white line of the Sikaflex without any reference as to what had been used. A few days later I got their response... ‘Excellent! On each sample tested the timber failed before the adhesive. You may commence the repair work’. They did however make a proviso on minimum plank lengths insisting on a stepped lapped joint rather than the scarf joints I’d proposed. All work would have to be signed off at each stage.
The only problem I could foresee was to ensure any signs of Sikaflex were kept well out of sight!
‘Mary Ann was built with an inner plank of 8mm Brazilian mahogany’