AUG 2015 TECHNICAL MEETING

SHOW ’N TELL

Our August meeting took the form of a Show ‘N Tell night with three well known speakers from the crowd addressing us on the night — that’s Ed Essers, Rob Bingham and Harry Speight.

 Ed Essers — An Update on the Building of His 14m Herreshoff Mobjack Ketch

Ed gave us an update on this major boat building project. The framing is now finished including the deck framing and the hatch and skylight surrounds are now also complete.

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The main focus at present is the plating out of the hull which is advancing fairly quickly using block and tackles and come-alongs to gently pull the sheets into shape around the framing prior to welding  each sheet to its adjacent sheet internally and externally. Ed noted that he is not welding the sheets to the framing until all of the sheeting is fitted.

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This process is progressed one plate at a time alternating from one side of the vessel to the other. One edge of each plate is chamfered on the inside prior to welding to the adjacent plate. The outside of the joint is then grooved to provide good metal for the external weld. When required, Ed is using 3mm MDF to make a template prior to cutting the aluminium plates.

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The boat has a 50 % ballast ratio which, having regard for its aluminium construction and the original design being for wooden construction, Ed has maintained by using 8 tons of lead in the keel area. He explained to us his method for installing lead ingots in the aluminium box keel structure and then pouring molten lead over the ingots progressively until the required amount of lead was in each box. Following this Ed welded pre cut aluminium plates over each box. This was done with a rig that Ed had constructed using half of a new LP gas bottle as a crucible mounted on a mobile frame with double pivot points. He used 2 burners, 1 below the crucible to keep the lead molten and 1 at the top to melt the lead ingots into the crucible.

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Ed also explained construction of his chain plates made from 2 layers of 16 mm aluminium plate. The 25 mm hole to eventually accommodate the stays was fitted with a ferrule made from stainless steel tube pressed into the hole with Ed’s 10 ton press. The ferrules were made over length by 12mm on each side so as to prevent the stainless steel rigging shackle from touching the aluminium. An anti seize compound was also used between the ferrule and the aluminium chain plate. Ed has also used a similar approach to manufacture the bob stay fitting. Some of the chain plates have now been fitted to the boat and the 2 mast compression posts are also installed.

 

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Rob Bingham — Bruce’s Heritage

Rob Bingham gave us a very interesting wrap up of the various ‘lives’ of his ski boat Bruce which he titled ‘Bruces Heritage’. In his early years, Rob’s family had a house on Lake Munmorah on the central coast of New South Wales and they spent a great deal of time sailing and water skiing in their spare time. Rob’s father’s name was Bruce and hence the name of the boat.

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Bruce has had a number of inboard engines fitted over its long history. The original power plant was a 1950 flat head Ford side valve V8 with a direct drive (ie the propeller shaft was connected directly to the engine – no clutch). This was removed and replaced with a Ford big block 352 V8 in 1970. In 1977, the 352 blew up and a similar 320 engine was fitted. Bruce was regularly used for towing disabled skiers and show skiers on the Hawkesbury River but lacked the power to pull a 6 skier pyramid. To remedy this, a Ford 390 big block engine was fitted in 1983. This engine produced 400HP but still had a direct drive.

1950 255 Flathead Ford V8

1950 255 Flathead Ford V8

390 FE Series Ford Big Block

390 FE Series Ford Big Block

 

 

 

 

 

 

 

 

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Between 1998 and 2000, Bruce was restored by replacing the frames and deck as well as all of the upholstery. This included the fabrication of new exhaust manifolds and a sump for the 390 from stainless steel to resist the rigors of Rottnest crossings. When the 390 met its demise with three split bores in 2008, it was replaced with the current power plant which is a marinised Chevrolet 350 with a heat exchanger and clutch. Rob designed and manufactured the fully stainless steel heat exchanger and the direct drive engine water pump. This engine has been seriously worked over including porting and polishing. It is now capable of driving the boat at 85 km/h and is the fastest boat in the Heirisson Island Water Ski Club. At a more leisurely pace of 40 km/h it uses only 16 L of fuel to get to Rottnest.

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In closing, Rob presented photos of a similar Chickadee hulled ‘Merlin’ which was fitted with a V12 Rolls Royce engine. Freeboard was clearly not one of its strengths but did it go — 140mph!

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Harry Speight on Mast Straightening

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Harry Speight addressed us on the approach to repairing his bent mast. This was the result of an apparent 50 knot gale that hit the Rockingham area in mid 2013. His Farrier F82A trimaran (see ABBA newsletter Nov Dec 2012) was folded and on its trailer.

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The whole rig was tipped over on its side and rested on the mast which bent when it hit the ground. The bend was at the lazy jack hoist position and it initially looked as if a new mast of the order of $8,000 was the only solution or alternatively a $3,000 cost to professionally straighten it.

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Harry consulted Philippe Peche of ‘Sailforce’ (see ABBA newsletter June July 2013) in regard to a repair. A strategy involving cutting out the crushed section of mast and sleeving each side of it was developed.

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A piece of identical mast section was available from the same design of boat that had tipped over at Fremantle Sailing Club two years previously. The sail track was removed from the mast section and the section was then squeezed in order to fit it inside the full size section.

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At the same time, a compression tube was inserted where the lack of same had caused the spreaders to dimple the mast during the accident. With a full size piece inserted to replace the damaged section, the whole arrangement was riveted together to form a very strong repair.

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Harry has calculated that the wind that would have been just enough to flip the rig was 50 knots and if the mast had been rotated head to wind, the wind load would have been approximately halved.

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Harry subsequently devised a system of ground anchors to hold the boat down in the future. However, after a year of using this arrangement, Harry has been able to take up a pen in Mandurah which makes getting out on the water much more convenient.

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Thank you to Ed, Rob and Harry for providing us with a great Tech Meeting Show ‘N Tell which was appreciated by all members who attended.