| Author | Message | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
     Gary Hendrickson (Garyh) Rating: N/A |
Message from Scott Graham of Graham & Schlegeter Naval Architects, designer of S2's 9.1 Meter and a friend of the 9.1 Class Association. Hi Gary; I took a look at the keel discussion on the S29.1 website as you suggested. The information looks pretty complete to me. Nice job of assembling all that data! Best regards, Scott Graham | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Gary Hendrickson (Garyh) Rating: N/A |
A few words about the 9.1 deep draft keel postings: The nine messages just posted about the 9.1 standard keel, a sort of compendium of knowledge about the keel, are meant to be working documents that will be updated from time to time as more facts are uncovered by our membership. This has resulted from a keel investigation that was initiated at the Feb. 2001 Annual Class Meeting when Scott Corder, then Class Commodore, suggested a project to look into a couple of issues about the keel that we'd been talking about. I somehow got appointed to get started on it. When the results of the keel investigation were presented at the Feb. 2002 Annual Class Meeting (at the Strictly Sail Show at Chicago's Navy Pier), after some discussion a decision was made by the members present to post to the Class website not only the basic investigation findings that had just been adopted, but also the collection of information that had been gathered during the course of the project. We present this contribution of keel information as a gift from the Lake Michigan Fleet to all 9.1 owners and sailors, cruisers and racers alike. But particularly to those who support the Class Association with their ongoing membership. You'll surely want to return the favor of this gift (and of all the good useful information that's posted throughout the year on this Class-maintained website). Here's some suggestions on how to do that: 1. Join us with your boat and crew at this year's annual class championship, the S2 9.1 Meter North Americans, at the Chicago NOOD Regatta June 14-16, 2002. We'll look after you. And be sure to contact us whenever you are traveling near Lake Michigan. 2. Support our Class and the costs of its website with your ongoing Class Membership, a very reasonable outlay. The membership form can be downloaded from this website. Contributors to the 2001 keel investigation were: Scott Corder, Past Commodore & Sec/Treasurer Scooter #002 Russ Fender, Commodore & Webmaster Sails Call #018 Chris Sundberg, Rules Chairman Stimulator #009 Dick Daniels, Entropy #003 George Darrell, Paradox #070 Don Rychlinski, Race Chairman Kato #032 Greg Young, Past Sec/Treasurer & Commodore Spectra #085 Loren Thompson, Membership Director Kahuna #055 Mike Greenwald, Rules Committee Member Slingshot #013 Gary Hendrickson, Rules Committee Member & Sec/Treasurer Nomad #094 Scott Graham, Naval Architect with the former Graham & Schlageter, NA Scott Smith, Tiara Yachts Gene Hermansen, Racine Yacht Club, for technical consulting & the measurement jig Dan Reichelsdorfer, technical consultant & boat program manager for GL70's Cynosure & Equation GH | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Gary Hendrickson (Garyh) Rating: N/A |
The goals of this investigation were: 1. Validate the specification drawing for the 9.1 keel. 2. Try to get an idea how well keels as-built by S2 conform to that drawing. 3. Determine if the commercial CompuKeels keel template set for the 9.1 conforms to 9.1 drawing specifications 1) Scott Graham of Graham & Schlageter Naval Architects, designers of the 9.1, confirmed to me that the drawing I have was the one used by S2’s vendors to build 9.1 keels. In addition, measurements we made on several 9.1 keels all agreed with the basic proportions & dimensions required by this G & S drawing. 2) A keel measurement project on 9 boats with hull numbers between 002 and 094 (out of 128 built) showed that their keels all complied closely to the dimensions and proportions called for on the G & S keel drawing. This held true for both the earlier keels supplied by the original vendor using the two-half molding method and for the later-keels vendor who used a sand mold for the keel. (The shoal-draft keel was not considered) The measurement system we used collected 12 or more thickness measurements from each keel. The measurement points were located at 20%, 40%, 60% and 80% along each of three section chords. These sections were positioned near the top of the keel, at its mid-point, and near the keel’s bottom. 3) A comparison of dimensions and foil shape of the 5-section keel template set offered for the 9.1 by Computer Keels of Edina, Minnesota with the G & S keel drawing showed very good agreement between the two. This comparison was done by a) carefully extrapolating the G & S keel dimension specifications to the 5 locations on the keel that correspond to the 5 positions for the CompuKeels templates, b) measuring thicknesses along each of the 5 templates, and c) comparing the template thickness measurements to the G & S thickness requirements for each of these 5 locations. Conclusions:
| ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Gary Hendrickson (Garyh) Rating: |
Keel Shape Dimensions for the S2 9.1 Meter Deep Draft Keel Submitted by Gary Hendrickson (#094), Class Rules Committee The Graham & Schlageter keel control drawing is Drawing No. 035-09A Alt. A, dated 6/30/83, entitled Keel Sections & Bolt Pattern. This drawing shows keel section profile dimensions at 13 stations along the shoal draft root chord, deep draft keel root chord, and the tip chord that serves for both keels. A separate square-grid tracing-paper layout sheet contains 1:1 scale keel profiles for the deep draft keel’s root chord and tip chord. These chord locations are at the very top and the bottom of the keel, respectively. The keel has a total height of 48 inches. The location of the actual top of the keel on the boat is often not easy to see, and the keel’s bottom is typically hard to get to when the boat is in her factory-supplied cradle. Scott Graham explains that the keel width dimensions at any other location on the keel can be straight-line extrapolated from the dimensions for these two chords. For the purposes of keel dimension checks, it is useful to define five planes, or sections, on the keel at the following locations: Section 1 -- 40 inches up from bottom of keel The locations of these five sections actually correspond to the locations used for the commercially available keel template set offered for the 9.1 by CompuKeels© of Edina, Minnesota. Keel width dimensions for the 5 section locations on the keel listed above, that have been proportionally extrapolated from the root-chord and tip-chord thickness dimensions, appear in the tables below in the column called "G&S Design Half-Width, Inches." (Note that the keel design profile always divides the actual width by two) Note that the keel shape profile that was chosen by G&S for the 9.1 has its maximum width, or thickness, at exactly 40% of the distance from the leading edge to the trailing edge of the keel, at any location. The maximum design width always equals very close to 10% of the length, or chord, of the keel at that particular section location. For more information and background on the 9.1 keel, refer to the Class Bulletin Board, particularly to a series of informational posts about the keel. Section 1: 40 inches from keel bottom:
Section 2: 32 inches from keel bottom:
Section 3: 24 inches from keel bottom:
Section 4: 16 inches from keel bottom:
Section 5: 8 inches from keel bottom:
| ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| 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) | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Gary Hendrickson (Garyh) Rating: N/A |
Submitted by Gary Hendrickson (#094), Class Rules Committee Original keel vendor used keel mold with two halves Good control of keel dimensions. Keel weight certificates often overstated Used on hulls: up to approx. #070 ± 10 2nd vendor, Keelco, used sand-molding process Fair control of keel dimensions. Weight load caused this mold to tend to expand in width. Used on hulls: #070 ± 10 and above Initial keel design exceeded desired design weight Large holes were bored through near the top of early keels to reduce weight. Holes were covered over with covering and fairing compound This hole fairing area tends to bubble up and leak water; readily fixable Hull numbers up to approx. #012 Keel redesigned to add two 8” deep pocket cutouts in top of keel, in place of holes. Keel stud sizes and spacing pattern also changed. Date of change: 6/30/83 starting with hull numbers above approx. #012 G & S keel control drawing is Drawing No. 035-09A Alt. A dated 6/30/83, Keel Sections & Bolt Pattern | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Gary Hendrickson (Garyh) Rating: N/A |
Submitted by Gary Hendrickson (#094), Class Rules Committee G & S Drawing # 035-09A describes a solid lead keel about 48 inches tall, with a plumb trailing edge. The root chord (length of the keel section at the top) is 60 inches long. The tip chord (length of the keel section at its bottom) is 36 inches long. Maximum thickness of keel at any section = 10% of chord length. i.e. 5 inches thick for a 50-inch long chord. Maximum keel thickness is always at 40% along the chord, for any keel section. The 9.1 keel section shape appears to be a “composite” NACA foil shape. Its entry shape appears similar to NACA 64-010 The design entry shape (first 1” - 2”) of the 9.1 keel is rounded or radiussed, rather than a wedge shape found on a few 9.1 keels, which was caused possibly by extra grinding required to even up the shape after molding. The trailing edge design width varies from 5/16 inch to 3/16 inch, from top to bottom. Most keels actually measure quite a bit thicker here. Where this is the case, measurement will show that the keel’s section chords are 3/8 to 3/4 shorter than called for. This was likely caused by substantial grinding of the trailing edge to remove residual roughness and unevenness from molding. The trailing edge should be square, not rounded. The bottom edges of the keel should be relatively “sharp” all around. Occasional light grounding on rocks & stones can grind off a pretty substantial radius on these edges, but they need to be sharp to control water flow and maintain keel efficiency. In a cradle, this area is difficult to access and fix, unless the boat is raised up and set back down propped up with the keel accessible, as has been done by some. A check of the shaping and dimensions of a number of keels in the Lake Michigan racing fleet has uncovered no significant deviations from overall design shape and no significant differences in specific dimensions or attributes from keel to keel (i.e. no keel redesigns). They were generally in pretty good shape. Several conformed especially well to the design drawing dimensions because they were either early keels or had been professionally faired with accurate templates. Keels tended to be oversize in thickness rather than undersize – After molding, a layer of fairing compound was spread on over the lead at the factory to smooth the surface and prepare for a gel coat finish. | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Gary Hendrickson (Garyh) Rating: N/A |
Submitted by Gary Hendrickson (#094), Class Rules Committee 7 or 8 stainless steel threaded rods are molded 12” - 15” down into the top of the keel, and they extend 3 inches above the top of the keel. Their diameters are all 3/4 inch for earliest keels, and 3/4 and 1 inch for later keels. The keel fastener layout for later hulls built after June 1983 is as follows. There are 7 keel fasteners. Moving forward from the aft end, you see a 3/4 inch stud, then another one, then two of them side by side. Next, down in the first square opening in the mast step "floor" area is a one inch stud, in the middle square opening is a second one inch stud, and finally a 3/4 inch one in the forward-most small square opening. The nuts and washers that S2 used for many boats are ferric, or mild steel, however. These are the parts that are rusting, not the stainless studs. The reasoning for not using stainless steel for the nuts was apparently that dis-similar metals would have less tendency to loosen up over time, we are told. Should anyone replace the keel washers & nuts with stainless steel ones, surveyors strongly recommend applying Loctite # 270 thread compound to the threads. The tightness of keel nuts should be checked every few years, and after an accidental grounding. The recommended torque to use is about 400 foot-pounds. The socket sizes for the nuts are 1 1/8 inch and 1 1/2 inch, deep throat. | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Gary Hendrickson (Garyh) Rating: N/A |
Submitted by Gary Hendrickson (#094), Class Rules Committee The section of the hull that the keel fastens to is apparently a rectangular-shaped heavy-duty construction insert section that S2 bonded into the hull. The outline of the keel stub insert can be seen on the hull when fairing-sanding has penetrated the bottom paint and the gel-coat. Different inserts were used for either the deep-draft or shoal-draft models. The hull – keel joint lies several inches below the bottom of the hull, when viewed from under the boat. The width of the hull insert (the keel stub) where it mates to the keel is a little under-size compared to the width of most keels at their root chord (top). Thus one finds that a lot of fairing material has been slathered onto this area to fair the keel into the hull. This fairing build-up tends to crack along the hull-keel joint over time as the keel shifts naturally from side to side with varying side loads. The surface cracking is usually first noticed at the forward and aft ends of the joint. This process is normal and the cracked area is easily ground out and refilled. When cracking at this joint becomes more pronounced, it can usually be controlled by tightening the keel nuts. | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Gary Hendrickson (Garyh) Rating: |
Submitted by Gary Hendrickson (#094), Class Rules Committee Besides the normal wear & tear on keels – nicks, gouges, rounding of the bottom edges, especially the front knuckle – most keels have efficiency-robbing imperfections that may not be easy to spot. We have observed minor dips & rolls in the side surface on a number of keels. These slow the boat by consuming energy to pump the water as it moves over the keel. Two keels in the Lake Michigan fleet exhibited another similar fault: a shallow concaveness on the starboard side 12” – 14” wide, extending through about 2/3 of the height of the keel. In addition, later keels poured with the sand-molding process showed a tendency to exceed the design width dimensions by as much as 10% - 12%. Checking and fairing the keel is considered to be an absolutely essential project, and we’ve seen two basic approaches used: - Fair the keel to the G & S keel design dimensions using accurate section templates. This approach can entail shaving up to 300# of lead from the keel. A few of the fastest boats in the Lake Michigan fleet have been faired using the no-shortcuts first approach, e.g. Paradox, Scooter. Two other very fast boats have utilized the 2nd approach, e.g. Spectra, Kato. G & S designer Scott Graham states he’s uncomfortable removing too much lead from the keel and favors the 2nd approach. He feels if you’re going to have to put in a terrific amount of effort to trim & fair your keel, you’d be better off starting over with a new keel made right. Whichever approach is used, a good fairing job requires a good technique for finding the high and low spots on the surface of the keel, and also a long-board sanding tool. Checking fairness in the horizontal plane requires a smoothly flexible batten. Checking fairness vertically requires a stiff straight-edge 4 feet long or so, and guide-lines marked on the keel as follows. 1. At three different heights measuring up from the bottom of the keel, say, 8”, 24” and 40”, draw horizontal lines. Measure the length of the keel chord, front to back, along each line. The design of the keel is strictly linearly proportional. That means that when a straight-edge is laid on the keel along these 4 lines, the keel surface should be flat with no bumps, hollows or curves. | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Gary Hendrickson (Garyh) Rating: N/A |
Submitted by Gary Hendrickson (#094), Class Rules Committee Computer Keels of Edina, Minnesota offer a template set for the 9.1 standard deep draft keel that appears to track the G & S keel drawing dimensions well. Visit www.compukeel.com/ |
