Tuesday, 8 December 2009

How to turn your boat hull over?

Andrew and his scale model of yacht hull Tididi,well worth the effort!

Andrews scale model of his whole set up,while this took a lot of work,it allowed a pin point indication as to where to attatch his turning points.

The picture below shows how well Andrew has his hull balanced,he is tying a control strop on the build stocks underneath,as you can see,the hull is quite happy in the position its in,as it was for the whole 180 degree turn.

As the blog prior to this one shows how Andrew turned his Hartley 37 hull over, I will explain below how I did a larger hull myself,Andrews situtaion was quite similar to my own,excepting he had sand below his hull,while we had concrete! I suggested my own turn method and Andrew did the rest,on the day he could have turned his hull quite easily on his own.

When you do finally reach the time when your new hull is ready to turn,the options on which method to use starts to cross your mind,I have done this a number of times,normally with block and tackle,one to lift and one to control decent,if the boat still has its building stocks in place,its very easy to fit long side rails to that and use those as cross beams for the roll,this way the hull never touches anything.

When I came to roll a 43ft wood epoxy hull I had built (six weeks build time) I had a new problem,the space was far tighter than I thought,in fact so tight I had guys digging the concrete floor out to make enough space,the other option being to remove the roof of the outside shed I was building in,that was not going to suit me,so I took the concrete,big hammer and pick axe route.

Even then I was in a tight squeeze,so how to keep full control with the four chain blocks I had thought to use,I was certain some hull damage would be the result? Then I had an idea,what about a spit turn,just like a rotisserie,make up a turning spindle for the transom and the bow and then turn with an up haul and control with a down haul.

This requires a bit of engineering,welding of steel tubes and foot plates,this done I called on friends Tom and Peter one saturday to help with the turn,we nearly made it but more concrete was required to be moved,so we had another go the following saturday.This time Peter and my wife,Jean, came to work the blocks,all was secure,the turning spits on each end were bolted to the concrete slab they stood on (very important) I had Peter controling the up haul chain block and Jean up a ladder with the down haul chain block.The trick and the unknown bit is whats going to happen when your hull reaches its point of no return and moves from an upside down postition to a right side up position,balance is everthing,if your spit attatchment points are in the right place,its balanced and the hull will be quite happy in any position.

We had a few inches to go,Peter took his Chain block up higher,Jeans chain block was by now at the point where instead of taking up the slack,she now had tension on it,this was our point of no return,how good was our balance point was now on our minds,as it was we were fine and Jean lowered the hull untill it was right side up all on her own.

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