For the very latest activity, click here: From a Bare Hull

Sunday, March 05, 2006

New Bandsaw and More Floor Timbers

My wife selected and purchased a new bandsaw and some accessories on Friday. I spent most of Saturday morning putting it and the mobile base together. Lots of fasteners between the two. Along with it she bought an "extension kit" which raises the maximum cutting height by 6 inches. This required taking the factory-assembled saw apart then re-assembling it with the extension parts. It also took some time to adjust and align the blade and bearings. So with the new bandsaw I was able to finish the mizzen mast step. With the lamination done last week, I used the bandsaw to trim/smooth the curved edges to the hull. After about three passes I got a perfect match to the shull shape. For now the step will just rest in place on the hull until we are ready to do the final glass. Also this weekend I laminated and tacked in the floor timber/thrust bearing plate. This is laminated similar to the mizzen mast step, but using only two pieces of 3/4" Coosa board. This is the piece that will hold the thrust bearing assembly for the Aquadrive. Instead of bearing compression forces it neads to bear lateral (sideways) forces, so layers of laminate are not as critical. Instead it will get four to five layers of glass skinned over the outside to minimize deflection (as recommended by the Aquadrive installation manual). More on what an Aquadrive is described below. Cut/shaped and placed the lower bulkhead between the aft stateroom and the engine room. We can now place a temporary floor in the aft stateroom. Next phase will be the main salon bulkheads/timbers and tank space. We have more Coosa board on backorder. Hope it arrives in the next week. What is an "Aquadrive"? Traditional sailboat engine installations usually are just a engine+transmission coupled to a straight shaft that goes directly to the propeller. In this setup, the force from the thrust of the prop is transferred, via the shaft to the transmission/engine, then via the engine mounts to the hull of the boat. That is how the boat gets its forward motion. There are some downsides to this setup. Wear and tear on the transmission for having to bear the forward thrust can cause transmission failure (rare, but it happens). The engine mounts need to be pretty stiff in order to sustain the shear forces from the shaft. This means that noise and vibration from the engine are also more directly transferred to the hull, which accounts for about 50% of the "engine noise" one hears throughout the boat. Finally, the shaft alignment must be very precise. This requires precise alignment of the engine as well. Now moving a 600 pound engine up/down/left/right in 1/8th inch increments while inserting shims can be difficult if not annoying. The Aquadrive solves these issues by isolating the engine/transmission from the prop shaft. It splits the traditional straight shaft into two shafts. The prop shaft pushes on a thrust bearing and plate that is attached directly to the hull. This eliminates the wearing forces on the transmission in a straight shaft setup. The thrust bearing is then attached to the transmission via a shaft with two CV (constant velocity) joints. The CV joints make the engine placement less critical. And you can actually dilberately offset the engine up/down/left/right a few inches without issue. Alignment of the propshaft is still critical, but it is easier to achieve since the engine does not need to be aligned with it. By isolating the engine from the thrust forces, softer, more vibration absorbent engine mounts can be used, thereby significantly reducing engine noise and vibration from the hull. The Aquadrive is made in Sweden and soley distributed in the US by a NW company. For more information click here.