Ball, needle and self-aligning bearings are suitable for use in heavily loaded environments such as winches, genoa car blocks, rig and main rudder mounting. The loads involved in transmitting a steering impulse from the windvane to the linkage are tiny, so mountings here can be quite simple. The bearings mentioned can be used for the main bearing and the pendulum axle bearing, but fitting a shaft seal to protect them against ingress of salt water or crystals impairs their smooth running. Unprotected ball bearings begin to seize as salt crystals accumulate and require a degree of maintenance to keep them running smoothly.
Anybody who has ever been driven by curiosity or boredom to take a windvane gear apart will surely have been shocked at the amount of dirt from the air and water which manages to accumulate in the bearings even in just one year. Salt crystals are easily removed at sea just by pouring on a little fresh water, but if your boat has spent a while moored downwind of a large town or city, you can expect to find much more troublesome deposits of oily harbour water in the bearings. Stripping down a bearing, as anybody who has tried it will confirm, takes steady hands and strong nerves as well as a good memory to ensure there are as many ball bearings at the end as there were at the beginning!
Sliding bearings, made from PE, POM, DELRIN or PTFE TEFLON achieve their good sliding properties by absorbing a certain amount of moisture (air/water) and tend to be slightly larger. The sliding properties are barely affected by accumulated salt crystals or dirt in the bearing. Sliding bearings are more reliable and durable in long-term service and are easier to replace.
This series of photographs shows the manufacturing procedure for sand-cast aluminium a. Model and core of the Pacific Light in wood b. Model assembly on the moulding plate c. Model impression in sand with cores inserted d. Removing the sand mould e. The result
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Lets start by identifying what exactly certain boats are. Sometimes the terminology can get lost on beginners, so well look at some of the most common boats and what theyre called. These boats are exactly what the name implies. They are meant to be used for fishing. Most fishing boats are powered by outboard motors, and many also have a trolling motor mounted on the bow. Bass boats can be made of aluminium or fibreglass.