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     Gary Hendrickson (Garyh) Rating: |
Submitted by Gary Hendrickson (#094) With some careful measurement, you can make a rough comparison of any boat's keel dimensions to the original G&S design shape, using the dimensions from 3 of the 5 profile tables in a separate posting entitled Keel Shape Dimensions for the S2 9.1 Meter Deep Draft Keel. The tools needed are a lead pencil, tape measure, straightedge 3-5 feet long, measurement calipers that have a throat at least 2 feet deep, a 12-inch scale, and perhaps a calculator. Another pair of hands is helpful, but not essential. Here’s a way to go about it. 1. Draw horizontal lines at three different heights on the keel, measured up 8”, 24” and 40” from its bottom surface, on both sides of the keel. These chord lines are the locations of the section chords for 9.1 keel sections 5, 3, and 1, respectively, in the tables given in Keel Shape Dimensions. 2. Next, check how well the lengths of the keel chord c, measured front to back, for each of these 3 chord lines correspond to the “c” dimensions shown in the tables. These section chord lengths will likely measure 1/4 to 3/4 inch short on most 9.1 keels. 3. For each of these 3 sections, locate and mark 4 measurement points at 20%, 40%, 60% and 80% along each chord line, on both sides of the keel. These “Front-Back Locations” are listed in the second column in the tables. This is the distance you will measure back from the leading edge (along the keel chords drawn above in step 1) to each point where the width of the keel will be measured. 4. Next, use the calipers to gauge the keel width at each of these 12 locations. Be careful not to disturb the caliper span while measuring it with the 12-inch ruler, and record each measurement. Due to the natural curve of the keel, it is necessary to measure the 20% & 40% widths from the front of the keel, and the 60% & 80% widths from the back. Your keel measurements, divided by 2, can be compared to the dimensions shown in column 3 of the tables. A calculator can help convert fractions to decimals, where needed. (If a more detailed assessment is desired, measurements can also be taken on keel sections 2 and 4, and at more points along each chord) |
