Jump to content

Sign in to follow this  
Drew

Rating the Coresound 20 Mk3

Recommended Posts

Has anyone attempted to get a rating for their CS 20#3 to enable club or event racing? I am faced with the dilemma of whether to apply to Australian Sailing, the body that determines local rules and handicaps, for what is known as a class-based handicap (CBH). It is needed to participate in any point scoring racing and seems to be quite a process. If anyone has done anything similar and succeeded elsewhere the details could be helpful to me if I pursue this here.

Interested to hear your experiences, especially those who have participated in events such as the Everglades Challenge.

Share this post


Link to post
Share on other sites

Since there are only a few 20mk3s out and about I think you may be the only one blazing this trail. As far as the Everglades Challenge goes it's very non-ratings based. In fact it's not even a consideration. "Run what you brung" as they say. All sailboats are lumped together and only differentiated by number of crew (1 person or 2 people or...now...3 people aboard) since that is a much larger factor in speed for the sailors since a two person crew does not have to stop if they have a cabin or shelter for sleep aboard. The only thing that matters is finish time. 

 

 

Share this post


Link to post
Share on other sites

Thanks for your reply Alan. I will keep you posted on progress. Can you tell me the designed waterline length (DWL) as I can't find it in the plans data.

Share this post


Link to post
Share on other sites

223 1/2" or 5.67m. Good Luck!  We are interested to see how it goes. We have some buoy racing here in our area on the Neuse river but we tend to just go camping or to the beach when we have free time and haven't gotten into the social racing scene yet. Back in the day Graham used to race Spindrift 10s with all the builders here. I wish i was there for those days. I would love to have an active Spindrift race fleet again. 

S101.jpg

s102.jpg

  • Like 2

Share this post


Link to post
Share on other sites

I'd suspect the CS series in general would get spanked pretty bad, by the current rating systems, so you might be better off just letting your local committee offer you a rate, on observed performance potential and race finishes. Depending on politics within the committee and your experiences with them, the rate will move around, but after a season, they'll get you reasonably sorted.

Share this post


Link to post
Share on other sites

OK guys, next question (Alan). I know the CS20 Mk3 self rights from over 90 degrees but have you worked out a self-righting index for them?

Share this post


Link to post
Share on other sites

Drew,

 

It took me a  google or two to see a reference to that index rating. I'm still not sure how its calculated but I had done some analysis of the 20m3k hull with and without water ballast previously. Attached below is a pdf of the graphs (imperial units at the moment sorry).

 

Both the ballasted and un-ballasted cases assume no crew aboard and i did one with two crew sitting on the wrong side which could simulate a very poorly executed gybe perhaps.

 

Interestingly the masts (if sealed) provide a not insignificant amount of righting just after capsize. A good reason to seal all those rivet holes. This effect presents as a second "hump" in the righting moment curve after 90 deg is passed again assuming the masts don't take on water. 

 

While not shown, the weight of the sails is accounted for. It is assumed that the centerboard stays in the down position. Which may or may not be the case. We have thought about adding a cleatable downhaul line for the CB to make sure it stays down in a situation like this when sailing in deep water. Also note that the cockpit coamings are not included at all as part of the buoyant volume although they would help the down-flooding angle slightly. At 110 deg, the cockpit hatch is still above water.

 

Here is a link to the files, they were too big to upload here....

https://drive.google.com/drive/folders/1a5RWgDJGvyTCfyEOj0PosHYcIn2pxI0B?usp=sharing

 

 

Share this post


Link to post
Share on other sites

Wow! You are truly amazing. This should b encouraging to all of us. I am about to submit the initial paperwork and will let you know the outcome.

Share this post


Link to post
Share on other sites
On 25/02/2018 at 9:19 AM, Alan Stewart said:

Drew,

 

It took me a  google or two to see a to that index rating. I'm still not sure how its calculated but I had done some analysis of the 20m3k hull with and without water ballast previously. Attached below is a pdf of the graphs (imperial units at the moment sorry).

 

Both the ballasted and un-ballasted cases assume no crew aboard and i did one with two crew sitting on the wrong side which could simulate a very poorly executed gybe perhaps.

 

Interestingly the masts (if sealed) provide a not insignificant amount of righting just after capsize. A good reason to seal all those rivet holes. This effect presents as a second "hump" in the righting moment curve after 90 deg is passed again assuming the masts don't take on water. 

 

While not shown, the weight of the sails is accounted for. It is assumed that the centerboard stays in the down position. Which may or may not be the case. We have thought about adding a cleatable downhaul line for the CB to make sure it stays down in a situation like this when sailing in deep water. Also note that the cockpit coamings are not included at all as part of the buoyant volume although they would help the down-flooding angle slightly. At 110 deg, the cockpit hatch is still above water.

 

Here is a link to the files, they were too big to upload here....

https://drive.google.com/drive/folders/1a5RWgDJGvyTCfyEOj0PosHYcIn2pxI0B?usp=sharing

 

 

Hi Alan,

 

Really nice analysis! I was thinking about a floating topedo at mast top and forgot about the air inside sealed mast. Got surprise about how big is the varnishing stability angle for a water ballast boat.

Share this post


Link to post
Share on other sites

Thanks for the comments to date. I have made a request to Sailing Australia for a class based handicap and they have been helpful so far. Fortunately, my club in Canberra has two national inspectors as members so we have made a tentative date later in the year for measuring. The one issue that keeps coming up is the low centerboard to total weight ratio. I have said that, as well as Alan's righting graphs, I am willing to emulate the righting experiment and take the masts down to water level, but there is a bit of skepticism on that, arguing that it might not represent what could happen in a sudden squall (a la the incidents recently in the EC). I guess some people feel uncomfortable with water ballast as a substitute for centerboard weight.

Comments from you guys, especially from Graham, about the potential effect of adding say 100lb to the centreboard mass in the form of a steel plate CB with a heavy bottom end would be much appreciated. I note that the Norwalk Islands Sharpies seem to carry a lot of ballast weight.

Share this post


Link to post
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now
Sign in to follow this  


Hate ads?
Love messing-about?

Become a Supporting Member - $12 for the next year - and we'll remove the ads for you. Pay by PayPal or credit card.

Give $12 to Support Us




  • Similar Content

    • By Paul356
      Reacher and I tried something new on Saturday.  We took our boats out with the PHRF fleet on Green Bay, and the heck of it was, we did pretty good!
      Reacher is a member at M&M YC in Menominee, Michigan, where they have a fairly active big boat racing program.  This includes the annual "100 Miler" (which is only 45 miles long, for some reason) that usually attracts a lot of boats returning from the Chicago-Mackinac Race.
      Last Saturday, M&M held their annual Joey Shepro Memorial Doublehander, a more or less "fun race" and fundraiser for Make-a-Wish.  Reacher suggested I trailer up from Milwaukee and we could enter our Core Sounds and see what happened.  He has a 20, I have a 17.  This race is c. 14 miles from their Club, out around Green Island in the middle of Green Bay and back.
      They were nice enough to give us PHRF ratings, which was interesting.  Mine was 252. (That's seconds per mile, deducted from the final time, so I had about 62 minutes deducted.)  Reacher's was 246, so they pegged him theoretically as 6 seconds a mile faster.  For comparison, a Cape Dory 27 is 243 (New England PHRF) and a CD 22 is 282.  The slowest boat in the fleet was deemed to be a Com-Pac 19-2, rated at 283, while the fastest was a Tripp 33, rated at 90.
      This was set up as a reverse start.  The race started at noon, but each boat was given a unique starting time reflecting the handicap.  In theory, in a perfect race, all boats would cross the finish line together.  In practice, wherever you are in the race is your position at that time, since the handicap has already been accounted for.  No need to figure out if you need to "give time" to a boat at the finish line, since that's all been handled at the start.
      Thus the Com-Pac, as the boat with the highest handicap, was supposed to start at noon, precisely.  It never did, and we learned later that it could not point into the light breeze without starting its engine.  Tip to consumers:  don't buy a Com-Pac if you want to sail upwind in light air.
      I was next, at 12:07:02, and Reacher next after that 12:08:23.  So it went until some 34 boats were off the line, with the last (fastest) one at 12:43.  (Make sense?)
      The first leg was a beat of about 1.75 miles to a buoy before we turned to the island.  Reacher and I kept company on the upwind, tho he passed me as we neared the mark.  It was a blast sailing together.  It was about 80 degrees out, full sun, the water sparkling blue, the wind maybe 6, puffing to maybe 8 mph, from the north east.  I had us moving at 4 to 4.5 mph on the gps for most of the upwind.
      Then came a 3.5 mile close reach out the island.  It wasn't until then that other boats in the fleet started to catch up.
      I decided to go south-about the island; Reacher and most of the fleet went to the north.  Not sure if there was an advantage one way or another.  I was hoping for more puffs on the broader reach back on the North side -- dreaming of a bit of planning -- but those puffs never materialized.  GPS showed c. 5 mph on the way out, c. 6 on the way back.  Reacher's larger sails definitely helped as the wind stayed around 6ish or a hair more.  The water got a bit choppier, too, which hurt our light little craft when we had to punch into it but was still "flat" for the big keel boats. 
      The last leg was around the buoy and back DDW to the finish.  Almost caught up to a Catalina on that leg, but not quite.  My speed was 3.5 to 4.5, depending.  Their speed was flogging....
      Results:  As one of the big boat skippers said, in that light air, "it was a waterline race."  In general, boats with longer hulls and therefore lower handicaps did better, which is typical for a PHRF fleet in light air.  But Reacher was 18th of 34, and I was 26th, finishing in 3 hours 29 min.  Reacher was done in 3:09. (Full disclosure:  two boats abandoned and four were DSQ for whatever reason).  Of the 28 that finished, I was in ahead of a S2 11.0 (handicap 161) and a Catalina 309 (HC 186), and Reacher also bested a Hunter 27, a Hunter 38, an S-9.2 and a Catalina 28, among others.  I should add Reacher's a pretty fine sailor.
      Needless to say, Reacher and I were pretty darn pleased with these little boats.  They kept moving in the light air, pointed well, reached well, ran well.  We spent a long time after the race admiring them and talking about what mods we like on each of ours.  We couldn't have kept up with the big boats in this year's Mac race, of course, given the 6 to 8 foot waves and the 30 mph winds on the nose.  But in this race, hey, we were right in there.  And it was a blast to be out on the water on such a beautiful day.
      And photos?  I wish I had some, but sorry folks,  can't race singlehanded and take pix, too.  I might have one, and might have a gps track.  Will see if I can find download.
      But be glad you have a Core Sound.  Great boat. 
    • By tfrei
      Any racing advice for someone who’s about to start a race in light air with My core Sound 17? I’m in the second day of racing. Had some trouble yesterday getting stuck when tacking. Wondering whether my weight should be forward since I’m going solo? I’m welcome to any other Css 17 sailing tips. 
×

Important Information

By using this site, you agree to our Terms of Use.