Cold moulding – veneer or ply??

Before working on any of the planking the hull had to be secured to the floor and adequately supported at the gunwale. This enable the hull to sit true and square with most of the weight taken on the trolley which was supporting the keel.

Tony and I had been trying to source veneers which was our original idea for cold moulding. We were thinking of offcuts from plywood manufacturers. We spoke with Hoop pine ply manufacturers in Queensland and got some sample material. After experimenting with it, it wasn’t going to work as we had hoped. Of course, we could get veneer cut to order but that was going to be very costly. The reason we had thought veneer would be good was to get round some of the tight curves on the hull, particularly the aft tuck at the keel.

Using some old 4mm marine ply I did an experiment to see if after steaming how much of a compound curve it would take without breaking.

From the photo it was clear that it was possible to get very significant bend into the ply even in two directions. Now how this would scale up to big sheets and how to steam them remained a problem but it was encouraging enough to decide to use 4mm marine ply. If we couldn’t get the tight curves, we could use veneer in those sections. Ok we had a plan to move forward!

The other decision we took was to make sure that every component of the hull was coated with a penetrating epoxy sealer. We used FixSeal 1060 epoxy sealer. The timbers had already been coated when they were removed for cleaning up. We would use the 1060 on the ply [both sides and edges in particular] and the underside of all the planking and the keel.

Removing planks and steaming the ply

The process was to remove a few planks from one side of the hull, then fit and glue and screw that section with ply. Once the ply was in refit the old planks or fit new planking. Then move onto the corresponding section on the other side of the hull and repeat. The idea being that the stiffness and shape of the hull would be maintained by proceeding section by section.

The first garboard plank removed! The first three planks from the keel were kauri and were in excellent condition for their 90 years!.

The timbers were slotted into sockets chiselled into the keel. Opening up the garboard plank enabled these sockets, which over the last 90 years had collected all sort of dirt and crap, to be cleaned properly, primed with 1060 and then the timbers to be screwed to the keel – stronger than the original build! The quality and workmanship of Charlie peel and his team was most evident during this part of the construction. I loved the little stop wood in the half lap joint on the keel / stern post that was dried out but still in good condition!

Ply and Planking

Three of the bottom planks plus the stealer plank were removed from the starboard side. This covered the tight tuck in the aft section of the keel.

The ply had then to be steamed and bent onto the timbers. The first attempt was to make a flat steam box for the ply sheets however this didn’t work. The ply was very supple after steaming but given its thin nature by the time it was out of the box and against the timbers it had cooled and was as stiff as before. 

A slower, inch by inch method was employed which worked. Working in parallel lines from the centre of the sheet the ply was screwed to the timbers and using localised steaming, slowly formed into the shape. Surprisingly this worked without any cracking or breaking of the ply. Once it was steamed into shape it was left over night or until it was ready to glue onto the timbers. 

Epoxying the ply was a tedious job. Once the ply was released it sprung back to a ‘half way’ shape. The epoxy was applied to the timbers and then following the same order as originally used in steaming the ply was screwed into place. Guard washers were used to spread the force of the screws over a larger area to prevent the screws bursting through the 4mm ply.

Tony steaming inch by inch whilst I used the screws to pull the ply against the timbers. The first section of hull from the aft with the most extreme curve can be seen screwed in place.
One side of ply completed and glued in position! Definitely worth celebrating.

The next step was to replace the planks by gluing and screwing them back into position. The kauri planks could be replaced as they were after cleaning up and sealing the underside of the planks. Obviously, they would stand proud of the keel by the thickness of the ply but this would be faired after all the planking was completed.

This photo shows the port side with the garboard and first plank back in position over the ply. The planks were edge glued to each other as well as epoxied to the ply. 

Once the kauri planking was completed the cedar planks were removed on one side and the ply steamed and glued / screwed into position.

This picture shows the next section of ply finished ready for planking. The longitudinal joint between the ply sheets was glassed using epoxy and biaxial cloth. Lateral joints in the ply sheets were made over a timber, effectively a butt joint.

This picture shows the next section of ply finished ready for planking. The longitudinal joint between the ply sheets was glassed using epoxy and biaxial cloth. Lateral joints in the ply sheets were made over a timber, effectively a butt joint.

One of the aims of this project was to reuse as much of the original timer as possible. Part of this is to use old cedar planks from below the water line to replace planking above the water line. Below the water line planking was replaced with a mix of new red cedar and hoop pine.

The kauri planking was able to be re planked without any adjustment due to its condition and the shape that was being planked. The cedar planking is an entirely different proposition. Plank 5 which roughly corresponded to the turn of the hull to the topsides was in reasonably good condition on both port and starboard. This became the ‘reference’ plank and effectively the replacement planking was planked hard against this plank working both to the keel and to the sheer plank. Due to the increase dimensions caused by the ply a slightly wider plank was as a shutter plank below the waterline. As the entire sheer plank needed to be new this would be adjusted also to take up any small changes in dimension.

This picture shows plank 5. At the bow much of the planking needed replacing so the new fair lines of the planks were drawn onto the ply.

The plank ends at the stern were damaged beyond repair so every plank was set back approximately the distance of one timber spacing ~ 200mm. All the planking to the bow had to be replaced with new sections cut out from some of the below waterline planking. This required some steaming.

A recycled plank being steamed to fit to the bow. Below, first plank installed. Note the overhang on the stern.

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