What follows assumes you have an understanding wife
or like me you are single
No responsibility will be taken by the author for battered husbands as a result of following this help topic!
If you are lucky enough to have a fully kitted out workshop - forget what I just said!
I'm aiming this at the kitchen table top builder!
A big scratch built model needs a big stable building base if we are to avoid building twists and kinks into our lovely new hull.
The hull of my Sailing Trawler is exactly 1500mm from stem to stern by 368mm beam so I chose a base of 1625mm by 380mm.
I leveled up my kitchen table by packing up the legs with thin cardboard and by using my long spirit level made sure the table was level length ways and width ways and on the diagonals so that I had a flat base on which construct the build board.
Take one length of white double faced melamine board (they only come in 2500mm lengths so I'm stuck with an off cut!
) by 12mm thick and a bunch of 25mm x 45mm clear straight softwood sufficient to form a stiffening perimeter and a cross brace and a box full of 1 1/4 x no. 6 wood screws. See photos below.
If your building board is clamped to a flat and level surface while you build the hull you could get away without this step, but I could pick up one corner of the board and I could raise it 5mm without lifting the other three corners which is no good. It needs to be stiff and level all ways.
Clamp one length of softwood down one long edge of the board with a G clamps at both ends and set up a taught cotton string line down the seam between the two parts. Go to the centre of the board and check to make sure the seam still follows the cotton string line. If it is bowed, put on a bit of pressure on the wood and board until the seam is under the cotton line and clamp it.
It is a good idea to pack up the cotton at each end with small bits of thin card, this lifts the string line off the wood surface a fraction avoiding the string line being fouled and giving a false reading, this ensures it is dead straight.
Check all along the string line until you’re happy that the string line says the seam is straight and then drill from the melamine side and screw down tight. I had two battery drills set up with a 3mm drill bit and the other with a driver bit to match the screw heads.
Repeat the above with the other long side.
Next, turn the job upside down and clamp to your level table top and fit the two end pieces of wood to form an open shallow box. While the job is clamped to the table, screw everything up tight so that it stays flat when it is lifted away from the table.
The cross brace is made by custom fitting it into your new shallow box with a halved joint at the centre. By plotting its position on the upper surface of the building board, it is screwed down tight from the top surface.
The photos below should clear up all of the above.
Turn the job right side up and with your long spirit level make sure every thing is level all ways and sight down the top edges to make sure they are straight.
We now have a solid and stiff board on which to build any number of future scratch built boat projects.
I would advise giving the wood frame and the exposed ends of the melamine board a lick or two of yacht varnish if it and the model are to be stored in the shed or garage to avoid changes of moisture in the atmosphere causing havoc with your new and flat board.
Next, using our trusty cotton string line again map out a centre line of the hull the full length of the board. My cotton string lines are simply made up with a loop at both ends, one I can hang on a pin in the edge of the board and the other supports a bicycle spoke hook on which I can hang small weights.
The weighted end of the string line hangs over the edge of the board and is allowed to swing free in the breeze and by weighting it to just below breaking point, it keeps the line taught and thus dead straight. We again use the little packing pieces at each end of the line to keep if from fouling the surface.
Set out the model on the building board centrally length and width ways and plot off the positions of each frame of the hull down the centre line of the board.
I do this using the old surveying trick of the three, four, five triangle. Using a set of compasses, plotting a 3, 4, 5 triangle always ensures the corner opposite the hypotenuse is a 90 degree angle. See sketch below
IMPORTANT!!!!
I'm using 12mm exterior plywood for my frames.
The frames from the mid ship section to the bow are set up with their STERN facing faces on the frame position lines just marked on the building board - see sketch below.
The frames from the mid ship section to the stern have their BOW facing faces set up on the frame lines on the building board.
A little later in the build, just before we start planking, the frames are going to be faired so that their edges run in the direction of the planking.
The planks will sit flush with each faired frame edge providing a good gluing and nailing surface.
We are now ready for setting up the frames on the building board.
Next chapter – marking out, cutting out and setting up the hull frames on our shiny new building board.
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Topic: 3/4" to the foot model of Lowestoft Sailing Trawler Master Hand LT1203 (Read 114639 times)