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Lauralaunch
27th December 2010, 11:46 AM
I have an 18ft clinker launch that has previously been sealed with Sikaflex or some other sealant. It is now coming away and I want to turn her over and do a proper job. Any tips/hints on how to turn her over, that is after I remove the Morris Vedette engine

PAR
28th December 2010, 03:28 AM
I see this a lot, folks think all they need to do is smear some goo onto the exposed laps and all will be well. I can't tell you the thousands of hours of repairs I've preformed on lapstrakes, that all could have been spared if only I had the right goo!

There's only one goo (okay two goo's) that works and only one way it works. Polysulfide is the only goo that will stay stuck to wet wood, if smeared into a crevasses. Of course this isn't the best application technique. The best way to apply the goo is to open the seam, apply a fairly heavy bead, then close and fasten the seam while the polysulfide is still wet. This places it under pressure during the cure and insures it'll stay adhered.

The usual mistake is folks attempt to employ polyurethane goo, which doesn't stay stuck to wet wood. In fact, you can usually just grab one end of the cured sealant and pull the whole thing off in one big, long, rubbery string. If it is applied inside the seam and under fastener pressure during it's cure, it will stick a little better, but it's still not going to remain stuck to wet wood.

Lastly, epoxy is the other adhesive that does work, but it's a lot more difficult to apply then squirting some polysulfide in a wedged open seam. Generally the boat should be upside down, the planks removed, dressed, dry (very), the seams cleaned, then re-hung with epoxy as the seam glue.

This is also the best way to do the seams of a traditional lapstrake build, but often the boat is too big to roll over on her decks, so you have to curse and talk about other people in unflattering ways to get the job done.

As far as rolling her over, there are many techniques, but the best are ones are where there will be no question, of being able to handle the weight, such as a fork lift, back hoe, tractor or front end loader. You can use a come-a-long from a tree branch, block and tackle or even several buddies that are promised free beer, once the deed is done. A traditional 18' lapstrake will weigh about 1,500 to 1,800 pounds (680 - 820 kilo) if not overly built. It may even be considerably lighter if fully stripped of hardware, engine, etc., possibly less then 800 pounds (360 kilo) so a handful of well fed friends can handle tossing her on her decks.

Make up sturdy braces and a cradle to hold her shape, while she's upside down. Attach it to the boat before rolling her, so she remains rigid. A boat can distort badly upside down and not well supported, especially if planks are removed.

Lauralaunch
28th December 2010, 09:28 AM
Many thanks for the advice on the polysulphide and the turning technique. I had thought of a triangular frame to support her and using a block and tackle to gently roll her but the backhoe idea appeals more. Thanks again.. Bob