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Author Topic: The Lift Method of Half-Hull Modelling  (Read 546 times)


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The Lift Method of Half-Hull Modelling
« on: May 10, 2007, 12:33:31 AM »
The Lift Method of Half-Hull Modelling
By Colin Sheehan

This is a very good method of reproducing a hull, particularly if good sizes of timber are not readily available, as it can utilise thin planks of small dimensions which are usually easily obtainable.

The important part of a set of lines plan for this method are the waterlines. Once the scale of the model has been established and the lines plan reduced or enlarged to the appropriate size, your wood is cut and dressed into thin planks to the same thickness as the distance between each waterline and slightly wider than the half breadth plan. Each plank will become a "lift". A pattern is then made of each waterline as seen in the half breadth plan view either by tracing the plan or photocopying and gluing to a thin card to make a template. In most plans for smaller boats & yachts, the waterlines will most likely be far enough apart to be able to use them as is. If the waterlines are many and close together, such as they may be for a very large ship or a particularly shapely hull, you could possibly use every second line instead to avoid making very thin lifts.

You will notice that in the example here, there are seven lifts needed. Once the templates are all made, place each template on the chosen plank (lift) and draw a pencil line around them, including the transverse station lines, before cutting them out with a bandsaw or coping saw and finish the edges to the lines on the pattern. Transfer the station lines down the edges of the lift for assembly reference later.

The Sticky Bit
Before applying the adhesive, perform a dry run to check alignment and fit between lifts as well as with the station lines on the edges of each lift. While you have them all together, align the template for the sheer plan with the station lines and lift edges (waterlines) on the back of the stack of lifts and draw a pencil line around it. Apply the glue to the surface of each lift and stack them atop each other ensuring that the station lines all line up correctly. (Note: Numbering each station [and template] 1 - 9 (in the case of design above) from the bows to the aft sections will help avoid confusion.)

One excellent idea I have used to aid fit and alignment is the use of two pieces of good straight plywood cut slightly longer than the biggest model you are likely to make, fixed at right angles to each other at the edges to form a "floor & back wall" to stack the lifts against. When protected by a film of plastic cling wrap, this speeds up the process and aids accuracy immeasurably. I found this idea in an excellent book titled "Boat Modeling The Easy Way" by Harold "Dynamite" Payson. Definitely in the must read category. He takes you through the building of nine boats of all types.
Lift Cross-section
Carving the Hull
Once the glue has dried and the hull has been removed from the jig, it should resemble a very jaggy hull of roughly the shape desired. An example of this appears below.
All that remains now is to cut the sheer plan out slightly outside the line drawn earlier. (If using a bandsaw to do this,take extreme care to avoid the blade snatching the wood if the lower edge should lift off the table whilst cutting) and remove these sharp edges from the outside of the hull with various chisels and gouges before sanding the surface smooth. Take care not to cut any more wood away than is necessary to remove the sharp edges as this will damage the accuracy of the lines. Now you have a very fair and lovely hull to finish as you choose. NOTE: You can take off, but you cannot put it back on, so slowly, slowly.

If the vessel being reproduced has a seperate external keel and rudder, these can be made, fitted and added at this stage. Usually, I glue the keel/rudder assemblies to the backing board after I have mounted the hull with a couple of screws.

This is a fairly lean description of the process and I do recommend that any keen boat modeller refer to the boating press for lines plans and books like Dynamite Payson's mentioned above.

1    If you want to make another identical half-hull pointing in the opposite direction, you could glue the two together to make a complete hull.
2    If you are planning to paint the model in original colours, then any available timber can be used to save money.

« Last Edit: October 28, 2007, 11:15:42 AM by magus »
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