I have recently completed a very complicated repair on a boat that required a lot of new techniques and complex processes.
The boat in question was a dyed black Tulipwood Carl Douglas single scull, which had not only suffered severe damage to the fin box but also had a few other serious issues. Since the boat is used on a tidal river the fin had had a number of accidents and repairs over recent years, with this latest incident being ‘the final straw’.
The most obvious problem was with the fin which had been forced all the way into the boat, taking all the internal frame structure with it. The only way to repair that framing was from the inside of the boat; something that would require making a very big access hole in the hull or completely removing the canvas. The boat’s other major issue was a leak caused by substantial movement at the aft bulkhead whilst sculling – doubtless related to the other crash damage.
At this stage you might be thinking “it’s time to go to the original manufacturer” for such a significant repair. Normally I would agree with you, but for various reasons this was not an option. After some discussion and investigation, I was the only person willing to tackle this major repair job.
So that I could think through the key issues and consult with other experienced boatmen, I drew up an illustrated step-by-step repair plan which documented the damage, the stages of repair, as well as some slight modifications to try and mitigate repeat problems. The process of creating this plan and seeking advice helped all involved be more confident about the work to come.
Since I did not have access to a the original mould to make an entire replacement canvas, it was decided to do the repair from the underside by cutting a hole in the hull. Before that drastic step was taken, a mould was taken off the hull so that a replacement patch could be created for later fitting.
Once the hole was cut, the damaged structural framework was cleaned-up and repaired. The repairs did not duplicate the original design, but were ‘beefed-up’ to increase the structural strength. A deeper replacement keelson section was grafted in, long enough to reach the frames either side of the damaged section. The replacement frame itself was made from two layers of 1.6mm ply laminated together with a light fibreglass layer, which should be much stronger than the original plain 2mm ply structure. An additional frame was added to the stern end of the fin box area to increase strength in case of another heavy impact.
During this process I was also tackling the problems in the cockpit. The only way to see what was going on under the aft bulkhead was to remove it, which was done very carefully to ensure that the original framing was retained. The framing here is very minimal in its design and had come completely adrift from the keelson. Without this framing, the entire bottom of the hull was able to flex with every stroke (ie as the footplate is pushed by the leg drive). Using some extra timber sections and the same ply/glass lamination used for the hull framing, a triangular support was added to support the hull and replacement bulkhead.
The work on the hull patch continued separately, with a male mould created from the female one that had been taken directly from the hull. Using wax sheet to compensate for the hull thickness, the male mould was soon ready for laminating the new section of hull. This was done in the same manner as the original boat construction, i.e. a kevlar and core timber laminated in one process, then a second kevlar layer and the Tulipwood veneer in another process.
With the bulkhead repair done, the replacement hull and fin box framing complete, it was finally time to tackle the difficult task of carefully scarfing in the patch over the access hole in the hull. This was the one part of the job that I had been dreading because I had never done this before and it is very unforgiving if you are aiming for a neat finish. Unlike any modern ‘white plastic’ boat, you can’t just use a bit of filler and paint to cover up any untidy edges – you’ve got to get it right first time.
I was lucky to have a boatman, with experience of similar repairs, come out of retirement to assist me. As you can see in the images, there was a lot of careful measuring, scarfing, trimming and trial fitting required. This job took a long time as the fit was more difficult to get right than anticipated.
Once the hull patch was complete, a new jig was used to cut the trench for the moulded fibreglass fin slot (in the exact-same manner as the original construction), with the incorporation of a new feature designed to allow the fin to knock free in the event of any further heavy knocks.
However, there was still further work required in order to completely finish off the boat: It was agreed at the outset that it made sense to respray the entire boat. Therefore a full rub back was required and along the way I found a few hidden problems from previous repairs which made for a lot of extra work.
Eventually everything came together and the boat was finally completed. The bulkhead repair looks excellent with the extra framing adding just 60g to the weight of the boat. The hull patch edges are barely visible, but the area of the repair (caused by the difficult patch shape) can be seen in the light as you look along the hull. The beefed-up keelson and structural frames in the hull and fin box added about 200g. The boat owner is happy to have his boat back in working – possibly even improved – order, and I suspect that the insurance company is pleased to have not had to pay out on a complete write off!