4/29/2023 0 Comments 8bit drummer snail![]() Your friendly lathe operator should be able to turn one of these drums for you to try. For all of these drums, the sheeting line is tied through a small hole in the drum at the fully sheeted-out position, at the largest diameter of the drum just where the channel starts. The larger of the step-down drums illustrated (again, upside-down) has a total travel of about 550mm, through four turns at the 32mm larger diameter, and any remaining turns at the 12mm smaller diameter. These drums have two diameters, a larger diameter, and a smaller diameter. The second picture illustrates two "step-down" drums. One revolution at close-hauled pays out about 40mm, so resolution is about 0.8mm per position, and repeatability is about 1.6mm. These black, shiny things are very difficult to photograph well.) The smaller drum has a maximum diameter of about 28mm, down to about 12mm close-hauled. (You may need to turn up your screen brightness to see the detail clearly. The larger drum, shown upside-down, has a total travel of about 600mm, and the smaller drum has about 300mm. The first picture illustrates two "snail" drums, which have an ever-changing drum "diameter". So it is necessary to have a drum whose diameter is less at close-hauled. The winch electronics cannot (at present) do better. The problem is, although the theoretical resolution is1.8mm, repeatability is about twice this value, around 3.6mm, and at close-hauled 3.6mm is a very significant difference. If the drum diameter is, say, 28mm, then one revolution pays out about 90mm of line, or about 1.8mm per position. If we call this a round 250 positions, we get 50 positions per revolution. The 8-bit analogue to digital converter of the RMG controller electronics provides for 255 separate positions of the drum over its travel of around 5 revolutions. But the resolution and repeatability of the RMG at just off close-hauled is not wonderful. In fact, I've broken my servo tray proving it can do this. Please DON'T try this with a Whirlwind, Futaba, HiTec, or ANY other winch! I also have absolute confidence in the ability of the RMG to sheet in from a broad reach to close-hauled when the wind is right at the top of "A" rig within an instant. I have my mainsheet post as low down as possible, and deliberately use the power of the RMG to "sheet vang" - tighten the leech of the main at close-hauled when I want to. The RMG-380 (and, for the IOM class, the more appropriate RMG-280) has outstanding power and speed. I've had two kinds of winch drum turned in my efforts to fine-tune the response of my RMG-380 sail winch at close-hauled.
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