Hull rollover

The Hull inside prior to rollover.



The waterline-pivot rollover method was used (also known as "pig on a spit" method). This was beacause there was not much space around the hull, low budget, far from crane hire yards and already had the materials on site.   Also the hull stays in the same location. It uses A-frames, heavy-duty chainblocks and pivot pipe frames welded to the hull.

Its probably a good method if an existing very strong shed already exists over the hull and the chainblocks can be attached to this instead of building A-frames.

My A-frames were made from 14ft long 6" x 12" hardwood railway bridge sleepers (as used for my building jig) and paperbark tree posts cemented in. 1/2" threadeded rods augered through held them together.

The pivots were 2" pipe welded to the hull at both ends horizontally at the design water-line. The pivot pipes were braced back to the hull with 40mm steel pipes. The building jig-angles coachbolts were removed to detach the hull from the jigs railway sleepers.

Roll-over day

This was done with the help of a few friends.  None of us had ever rolled a 2-3 ton 35ft hull over before. Three ton chainblocks were hired and chained onto the A-frame tops.

I wasn't sure if the center of balance was guesstimated right. So just incase it was a few hunded kilos lopsided, Dr Con bought his 2 ton? turfer winch, usually used haul his 4WD out of bogs. It consisted of a thick steel cable and the lever winch could pull itself along the wire rope. It was rigged amidships to help roll the boat once the chainblocks elevated the hull. A brake rope was also rigged amidships incase the hull decided to roll by its own weight.

Once all was in place the chainblock falls were hauled down simultaneously at each end and the hull began to lift and inch, two inches..a flying boat! When the wylo was about 2-3feet high, which seemed very far to fall, the turfer was hauled on..but it proved redundant because the hulls balance point was just about perfect, so only 2 half inch ropes (without block purchases) were easily enough to roll the hull around 180 degrees by hand, well almost. I had forgotten to cut a wooden A-frame brace pole off and it got caught up on the transom corner! (at about 160 degrees roll) so up the ladder to try to free it with a come-along, then the 2" aft pivot pipe began to bend!  it stopped after about 6 degrees bend as the transom corner released itself from the pole. (The pivot pipes had end plates welded on just incase the pivot pipe bent to a worst case scenario and the roll chains began slipping off). Its hard to describe the feeling of tons of hard work potentially about to crash downwards. We weren't standing anywhere under it that for sure. During all the action no-one even thought of taking a photo! (don't forget to bring a dedicated photographer to rollover day)

The final small lowering onto the keel, was needless to say, a big relief. Props quickly went in under the hull.



Note: The forgotten bush pole that caught the transom.

The wylo suddenly looked different. More like a boat than beached sub.

 Note: The tempoary cross brace amidships.

The foward A-frame and  hull pivot -bracing detail is shown in tree-cam shot above. The exposed hull was quickly covered with old roofing iron to keep any rain out.

Pivot rolling  in retrospect - Place roll-pipe braces very close to the roll chain attachment points. (On the pipe that bent was cause by the roll chain being about 9" out from the side braces attachment point.) or use a wider-stronger walled pipe, a ton or two is hanging off it. Also make sure nothing can snag up during the roll.

Other hull rollover methods

1) Another, probably better technique, is the the "jack-up and lower" method used by Nick for Wylo2. This method needs a large open area one side of the hull maybe 10m wide for rolling (best planned and set up when setting up the boat yard and build jig at the beginning of the project). Then the hull can be rolled by jacking the gunwale up to topple-point, lower the keel to ground with a block-tackle or turfer winch - 4WD winch?, then jack-up/block up the hull to upright position. The boat moves sideways about 3-4m? during this type of rollover.

2) If in town, crane hire with good operator is the quickest way to rollover. The hull can be placed back where it started or anywhere else if desired. Stronger tempoary hull cross bracing would probably be required in two places where the lift straps wrap around the hull.