Repair and Maintenance of a Drascombe Lugger

Extending the centreplate arm

This page is about adding an extension to the arm of the centreplate. This is necessary on some older Luggers where the centreplate arm is about 1-2 inches too short. This causes damage when the plate is lowered and the attached shackle 'impacts' on the centreplate case capping.

Sketches showing how capping becomes damaged Defining the problem

Sketch showing how the wooden centreplate case capping can be damaged by the arm of the plate being too short. The solution is to cut off the arm just below the hole and to weld on an extension which extends the arm by about 2".

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Sketch showing modification to Lugger centreplate arm Drawing of required modification

Two drawings showing the details of the required modification.

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Photo showing extension to Lugger centreplate arm Photograph of extended arm

My local chandler suggested an engineering firm that could carry out this modification. They undertook the work at a cost of 15 UK pounds.

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Photo of modified centreplate arm on Lugger The modified centreplate re-fitted on the boat

Photo of the centreplate re-fitted on the boat and a new wooden centreplate case capping fitted. The plate is in the down position and the arm plus shackle is well clear of the top of the capping.

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Project started and completed, February 2002


There is another more drastic alternative which involves a more complex modification to both the centreplate and centreplate case so that they become similar to the design incorporated in the new Luggers that Churchouse Boats and Honnor Marine build. I have not done this on Sospiri, but may do so sometime in the future as it also solves the problem of water ingress through the forward slot on the front of the centreplate casing.

In simple terms the existing plate lever arm is removed and the plate modified by welding on an L shaped piece of steel on the top of the plate. This results in a new higher arm which completely clears the teak capping. This then allows the slot in the front of the centreplate case to be permanently sealed. See sketches below

Sketches showing modification to Lugger centreplate Sketches showing the original and modified centreplate

The upper sketch shows the unmodified plate whilst the lower sketch shows the welded addition which ensures that, with the plate up, the arm is above the teak capping and clear of the forward slot in the centreplate casing

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Project Outline

Remove the existing plate and lay it on a suitable piece of 12 mm plywood (a source of second-hand wood is handy in this respect), and draw round it, including the slot for the axle. Omit the existing arm but draw on the L-shaped extension required to lift the arm above the centreplate capping. The new arm should be at least 4" longer than the original arm. This ensures that the uphaul/downhaul clears the front of the casing when the plate is 'down'.

Use a jig saw to cut out the template and drill a hole near the end of the arm so that the uphaul/downhaul tackle can be shackled on (see below).

Launch the boat and fit the wooden template centreboard in the 'down' position. Measure from the front of the casing to the back edge of the template to see how far the slot in the centreplate case capping will need to be extended to accommodate the broader plate.

Attach the downhaul/uphaul tackle to the hole at the end of the template arm. With the template plate fully 'down' the ropes between the block on the end of the arm and the block attached to the hull forward of the casing, should not chafe/foul the front edge of the case. Remember that there will be no slot in the front of the case to accommodate the rope. If it does chafe then the arm will need to be longer and it should be easy to estimate by how much.

The ply template can either be taken to a steel fabricator so that it can be used to fabricate a completely new plate in 10 mm mild steel. Alternatively get them to remove the arm on the existing plate and just use the top of the template to fabricate an add-on piece which can be welded on See sketch above. In either case the plate will subsequently need to be blast cleaned and hot-dip galvanized.

Before re-fitting the centreplate, the front slot in the centreplate casing should be sealed. I would do this as follows:

Finally the slot on the teak centreplate casing capping must be extended. Mark out the necessary extension of the slot on the teak and cut out using a jig saw.

Replace the teak capping and secure with the self tapping screws. The modified plate can now be fitted to the boat.