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Invited to describe the procedure we used at the boat plants for installing the Atomic 4 driveline, struts in particular, here it is. The steps described were what I did on the Newport 30’s but were typical for the era (early 70's) throughout the industry with minor variations.
Unlike what we go through as boat owners for alignment, tweaking the engine to align with the shaft and bearing (tail wags the dog) at the plants it was the opposite (dog wags tail).
The engine was installed on its mounts first. For the N30 it was mounted to the molded stringers in the interior liner before the liner was installed in the hull. Once the engine was in place a rectangular hole approximately 2” x 12” was cut through the hull on the centerline for the shaft log, a filament wound fiberglass tube. The prop shaft was placed in the engine coupler and the strut was slid on the shaft to determine where its base was to be installed in the hull. Once marked, another rectangular hole was cut through the hull to accommodate the strut base. See alternative method below.
The strut was removed and it’s base waxed, the shaft log was slid into place and shimmed fore and aft to center it on the shaft. The strut was slid back on the shaft so that its base fit inside the hole cut for it. At this point the aft end of the shaft was supported with a stick from the shop floor to counteract the shaft sag due to the weight of the strut.
Masking tape was applied on the outside of the hull to seal off the strut and shaft log holes and mish-mash was poured from the top onto the holes filling them roughly flush with the inside of the hull. ‘Poured’ isn’t quite accurate, the viscosity was similar to yogurt. Mish-mash was laminating resin thickened with asbestos fibers and once cured it had tremendous adhesion and strength. It’s true, I’ve lost more than one friend from those days to mesothelioma. The asbestos was kept in the shop in open sacks, we’d mix it by hand.
With the mish-mash cured we’d apply several mat and roving laminations on the inside of the hull at the two locations, approximately 12” x 12” each. We really had to watch the catalyst because the thickness of the lamination could create a heat driven chain reaction and crystallize the bonds. This happened once on a Newport 41. It was discovered at launching as the boat was being measured for racing handicap. The waterline kept getting longer!
With everything cured, 3/8” holes were drilled through the countersunk strut mounting holes. The pictured strut shows square holes for carriage bolts but ours were countersunk for flatheads. The masking tape was removed as well as the prop shaft and strut (that’s why it was waxed – to release it from the mish-mash). What was left at the strut location was a perfectly molded and aligned mounting recess. The strut was cleaned of wax, bedded with polysulfide (this was the early 70’s) and bolted in place with silicon bronze flathead machine screws, nuts, flats and locks. The aft end of the shaft log was cut and ground close and both it and the strut were filled and faired flush with the hull.
The prop shafts were made with extra long keyways on the inboard end. The shaft was put in place to measure for length, 1” between the strut and prop hub, 1.5” from the prop tip to the hull. The shaft was removed again and cut to length with a hack saw and dimpled to match the coupler set screws. The stuffing box was installed, then the shaft, then the prop.
The result was everything in alignment based on the engine attitude. It sounds like a lot of steps but after I’d done it a few times it was maybe a few hours’ work. It really helped having the deck off the hull.
Alternative to the hole for the strut base
The Newport 30 had a pocket molded into the hull for the strut. It more or less fit, sometimes needed a little persuasion with a grinder. Without the hole in the hull I’d make a mish-mash bed under the strut base with the waxed strut in place on the shaft. No additional laminations were required inside the hull for the strut. When the mish-mash cured it formed a perfectly shaped and angled shoe for the strut to mount. Drilling and bolting went as described above
The recently posted Ericson drawing
According to the drawing Ericson embedded the strut bolts on the inside of the hull. Catalina did something similar. Like I said earlier, there were minor variations from brand to brand.
Unlike what we go through as boat owners for alignment, tweaking the engine to align with the shaft and bearing (tail wags the dog) at the plants it was the opposite (dog wags tail).
The engine was installed on its mounts first. For the N30 it was mounted to the molded stringers in the interior liner before the liner was installed in the hull. Once the engine was in place a rectangular hole approximately 2” x 12” was cut through the hull on the centerline for the shaft log, a filament wound fiberglass tube. The prop shaft was placed in the engine coupler and the strut was slid on the shaft to determine where its base was to be installed in the hull. Once marked, another rectangular hole was cut through the hull to accommodate the strut base. See alternative method below.
The strut was removed and it’s base waxed, the shaft log was slid into place and shimmed fore and aft to center it on the shaft. The strut was slid back on the shaft so that its base fit inside the hole cut for it. At this point the aft end of the shaft was supported with a stick from the shop floor to counteract the shaft sag due to the weight of the strut.
Masking tape was applied on the outside of the hull to seal off the strut and shaft log holes and mish-mash was poured from the top onto the holes filling them roughly flush with the inside of the hull. ‘Poured’ isn’t quite accurate, the viscosity was similar to yogurt. Mish-mash was laminating resin thickened with asbestos fibers and once cured it had tremendous adhesion and strength. It’s true, I’ve lost more than one friend from those days to mesothelioma. The asbestos was kept in the shop in open sacks, we’d mix it by hand.
With the mish-mash cured we’d apply several mat and roving laminations on the inside of the hull at the two locations, approximately 12” x 12” each. We really had to watch the catalyst because the thickness of the lamination could create a heat driven chain reaction and crystallize the bonds. This happened once on a Newport 41. It was discovered at launching as the boat was being measured for racing handicap. The waterline kept getting longer!
With everything cured, 3/8” holes were drilled through the countersunk strut mounting holes. The pictured strut shows square holes for carriage bolts but ours were countersunk for flatheads. The masking tape was removed as well as the prop shaft and strut (that’s why it was waxed – to release it from the mish-mash). What was left at the strut location was a perfectly molded and aligned mounting recess. The strut was cleaned of wax, bedded with polysulfide (this was the early 70’s) and bolted in place with silicon bronze flathead machine screws, nuts, flats and locks. The aft end of the shaft log was cut and ground close and both it and the strut were filled and faired flush with the hull.
The prop shafts were made with extra long keyways on the inboard end. The shaft was put in place to measure for length, 1” between the strut and prop hub, 1.5” from the prop tip to the hull. The shaft was removed again and cut to length with a hack saw and dimpled to match the coupler set screws. The stuffing box was installed, then the shaft, then the prop.
The result was everything in alignment based on the engine attitude. It sounds like a lot of steps but after I’d done it a few times it was maybe a few hours’ work. It really helped having the deck off the hull.
Alternative to the hole for the strut base
The Newport 30 had a pocket molded into the hull for the strut. It more or less fit, sometimes needed a little persuasion with a grinder. Without the hole in the hull I’d make a mish-mash bed under the strut base with the waxed strut in place on the shaft. No additional laminations were required inside the hull for the strut. When the mish-mash cured it formed a perfectly shaped and angled shoe for the strut to mount. Drilling and bolting went as described above
The recently posted Ericson drawing
According to the drawing Ericson embedded the strut bolts on the inside of the hull. Catalina did something similar. Like I said earlier, there were minor variations from brand to brand.
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