Saturday, 3 December 2011

Hull setting and cradle

In the last post, I outlined plans to build a 1:6 scale work boat. The hull was ordered and arrived on Wednesday. Its well finished including the cut top edge. Nothing was done until Friday night when my Dad came up for his tea, after which we played with various different angles and thoughts. Prior to coming up, he had weighed his Wyeforce Tug which although a different scale, is of a similar physical size and has the same motor set up I plan to use. That weighed in at 6.5Kg minus the battery. So we filled the bath and played boats

As water weighs 1Kg per 1 Litre, I took some 500ml bottles of water up to the bathroom too. My hull weighs 2.2Kg so to match the Tugs weight I would need an additional 4.3KG or 9 bottles of water and a battery. Loaded up with the battery in the centre and 9 water bottles strategically placed to balance it out, it floated beautifully in the bath. A pen mark was put on the bow and stern to mark the water line.

This morning with the water line spotted on the front and back some more work was done. The first job was to get out the laser level, I only had about an hour and a half to spare so didn't think I would get much done.


The level was placed on the sideboard and a line projected over the table. By measuring up from the table top, to the projected line, the table was levelled to create my own "surface table" note the technical use of table mats under the table legs to help this levelling process..


Next the hull was placed upside down on the table and packed up, again using mats, until the line touched the pre marked water line on the bow and stern. This laser line now represents the water line.


To mark this line on the hull would be done using a height gauge, if I had one, so I used a marker pen on a tin of stewing steak, adjusted to height with drinks mats. This was done all round with a gentle pressure on the hull to ensure it wasn't sat twisted. the laser was left on just to check as I went along.


We had decided last night how much higher than the water, the deck was going to be. This line was added after raiding the food cupboard to find a tin of sweetcorn was just right.


My Dad had pointed out the benefits of making a stand as the first job, so that was the next job. I had only planned to mark the lines but it seemed a shame to not carry on with the table set!
I used some conti-board for the uprights. By using 4 tins of baked beans to support the upright over the hull I marked 130mm up from the beans and the hull and a freehand line was drawn that could be cut with the jigsaw.



Note that I left the frame longer each side so it would sit back down on the bean cans, ensuring the straight top edge is parallel to the table. As can be seen the cut is rough and leaves a gap to the hull. I applied masking tape to the hull as a release strip. Then mixed some car body filler, spread it on the support where it contacts the hull and pressed it down, till it sat on hard on the bean cans. This was repeated for the front support and a top plate added.


Once the filler had gone nearly hard ( about 10 mins) the whole thing was turned over and the hull pulled away, the masking tape parted from the filler very well and left an impression of the hull shape on the supports.


The filler squashed out leaving it wider than the wood but was easy to knife to thickness if done before total hardness was achieved.

After peeling the tape of the hull it was then sat back on its perfect fit cradle.



This will be a steady working cradle the pre marked pen lines are now parallel to each other and the table. I will probably make a new cradle with sponge on for when the hull is painted. I am sure old hands at boat building will have much more effective, neat, quicker and accurate methods of doing all this, i admit to making it as I went along!

John




3 comments:

Duckie. said...

Nothing wrong with that I can see, put some window form on it and you are right, but I'm only a kit builder so could be wrong!

Phil Parker said...

Very neat idea for that cradle. I shall be stealing that in the future.

RJR said...

Will have to see if I have any foam in the garage, but I'm guessing having a firm base to work on at the moment will be a benefit?

Phil, steal away!

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