Dudley Dix Yacht Design: June 2018

Sunday, June 3, 2018

Sportfisherman 26 - Over She Goes

The last of the hull sanding on Kevin Agee's 26ft sportfisherman was completed last week and epoxy barrier coat applied on the bottom, then she was ready to join the right-way-up rest of the world. See the video link at the end of this post for a time-lapse video of the turn-over.

Sanding and bottom barrier coat done, ready to go.

The turning was to be done with chain blocks hanging from a pair of 2x6x12ft planks bolted together, with 2x6 spacers between them, the planks braced by straps tying them to anchor bolts in the floor.

Previous boats of my own that I have turned over (34, 36 & 38ft) were all outdoors on earth surfaces and did not have turning frames around them. These differences changed how we had to accomplish the turning of this smaller boat on a smooth concrete slab and in rectangular protective frames.

We did it in two stages, with some rethinking and adjustment of equipment between the two stages. The rectangular frames meant that we needed to turn the hull 90 degrees, reposition equipment, then turn another 90 degrees. With my previous turns we could do it all in one extended process, lifting with lines attached to bulkheads adjacent to one sheer clamp and keep them there, simply lifting that side until the balance point, then lowering it slowly with those same lines and attachments. The hull had to be walked sidewards during the process, to always keep it close to the lifting gantry and it ended up rotated 180 degrees and back in the same place that it started.

Turning the hull of Didi 38 "Black Cat". This was done in one continuous turn from upside-down to upright.

Adding the frames around the hull creates pivot points at the corners of the frames and means that the boat must stop at 90 degrees and 180 degrees. We still needed to walk the boat sidewards during both stages and I had cropped the corners of the frames at 45 degree to help the frames to slide on the concrete slab during these movements. We had some issues with the frames sliding more than expected on the concrete and had to add precautions to control the sliding. In retrospect, it would have been better not to crop the corners, to leave hard 90 degree corners to grab onto the concrete rather than slide.

The boat dropped a few inches at the end of the first stage when the frames slid on the concrete. No harm done because the frames and padding did their protective work. But it warned us that sliding could be an even bigger problem in the second stage.

End of the first stage, time to change the lift point and reassess.

Looking at the boat on its side I realised that we weren't going to get this done with one chain block. The chain block already in use would be needed to control the last part of the turn. But, with the frames holding it very stable at 90 degrees, it was not going to continue the rotation without first being lifted at the other sheer clamp. So, we hunted down another chain block and rearranged the post staying before continuing. Mindful of the sliding problem of the frames on the concrete, we added two ropes tied to the frame and led through secure points against the wall, then under the boat to the safe side, where helpers could pull without risk of the boat falling on top of them. We also sourced two large tyres to serve as cushions under the frames if gravity did decide to take over control of proceedings.

The rest of the turn was done by lifting with one chain block until the balance point was reached, then easing out with the other chain block to lower the boat, interspersed with walking it back toward the lifting post before continuing.

Kevin was very relieved to get his baby safely grounded and stable again. The equipment was all removed then we all helped Kevin ad Michelle to celebrate this milestone in the project, with snacks and suitable beverages.