The September Toolbox was a return visit to member Ed Essers project as it takes shape at his purpose built shed just out of Armadale.

Your editor is going to take some license here and repeat some of the salient details of Ed’s project which have been recorded in previous newsletters.  Please refer to the newsletter for November December 2012 and November December 2013 for all the background details to this major project. The new material recorded here will be an update on Ed’s progress since our last visit in November 2013.

Ed has now commenced actual construction of his 14m Mobjack design Herreshoff Ketch. The vital measurements of this vessel are 13.812 metres over the deck, 3.828 metres beam and 1.686 metres draft. The original design was in wood but Ed has made the design changes needed to construct it using aluminium plate which will be welded with a MIG machine capable of using between 1.2 and 1.6mm welding wire. The aluminium is of varying thicknesses – 16mm for the bottom, 10mm for the keel box construction, 8mm for the frames, 6mm for the stringers and for the skin plating. The aluminium is Alcoa Nautic 5083 and 6082.









During this most recent visit we were also able to see the now complete tender for the Mobjack which Ed was working on during our last visit. This is a Catspaw dinghy built from plans obtained from the Wooden Boat Store. The Catspaw is a Joel White interpretation of Nat Herreshoff’s classic Columbia Dinghy. She is 12’ 815/16” long with a beam of 4’ 53/8” and is designed for oar and sail… and in Ed’s case sculling as well. The Catspaw has a housing type centreplate with a lead insert to assist stability.

Ed has used red oak extensively for the stem, keel, transom and the ribs. The lapstrake planks are 6mm hoop pine ply. At the time of our last visit, the stem, keel, transom and ribs were completed over a temporary building frame and the first of the planks at the keel close to being finally fitted. The Catspaw is now complete, painted and with beautifully clear finished oars and oregan mast in place and ready to go. It was very easy to see how this classic dinghy will very ably complement the traditional lines of the Herreshoff Mobjack when both projects hit the water.

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There has been great progress on the major project since we last visited. The frames are now erected on the keel box section and the stem and stern post in place. All the frames are notched out ready to take the stringers. Ed has trial fitted the first stringer and found that the angles that the stringers take to each frame will require further work to get the notch depths correct. He is using a hand power saw with counter rotating blades to do all the aluminium cutting – very successfully it would appear. The stringers will be fitted along the topsides and down the hull but work will momentarily cease somewhere above the keel area.

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This halt in stringer proceedings will facilitate the pouring of the lead keel into some of the  boxed out aluminium sections of the ‘deadwood’. There are other sections that are allocated for fresh water, diesel and the like. Ed pointed out that the lead would be poured straight in to the aluminium box sections – aluminium has a melting point of 6500 C and lead a melting point of 2800 C. Aluminium seal plates will then be fully welded to close off these lead keel sections. Ed has half a ton of lead and needs a total of 8 tons so if any members have a significant amount lying around that they wish to part with, Ed can help you out.

When all this is done, the stringers can be completed and some floors welded in. This will then clear the way for sheeting of the hull to commence. Ed is using 600mm wide plates that will be able to be pulled into place around the hull using a ‘come along’ to provide the horsepower. This will be achieved without any need to roll the sheets. As this phase progresses, access to the inside of the boat will increasing be via the mezzanine floor where Ed has stored much of the inventory required for the later part of the construction process.








The framing out of the vessel includes a 9inch wide by 6inch deep socket on the deck to accommodate the bowsprit which will measure 2 metres clear from the boat. There is also a Samson post constructed from a 100mm diameter aluminium tube with a 10mm wall thickness. At the other end of the ‘ship’ Ed explained how he had modified the stern post and transom design so that a trim tab could be fitted in a practical manner.

All of this raised the question as to how Ed had arrived at the scantling sizes skin thicknesses to use, given that the design was drawn for timber construction. He referred us to Dave Gerr’s book, “The Elements of Yacht Strength” which specifically details this type of conversion and makes recommendations on materials sizes for different types/materials of construction. Incidentally Dave Gerr is also the author of “The Propeller Handbook”.






And then of course there was the inevitable question of “what are you going to do when the boat is finished?” Ed’s reply, “sail around the world”. (he’s previously been around 2.5 times and his previous vessel had done 56,000 miles so the latest objective doesn’t sound like a big deal to Ed).

We thank Ed for facilitating this return visit to see his project literally taking shape. This was a very informative and enjoyable afternoon and members look forward to future visits as this very major project progresses. Thanks Ed.