Ballast

[JeffM]

Off-and-on toying with the idea of ballast.  Mainly with idea of resistance to knockdowns, easier righting.  Anyone know how to calculate the difference weight makes to righting force at floor level compared to low in centerboard?  I'm wondering what (say) 50lb lead in end of cb would do.  I'm guessing I measure a lever arm from somewhere around waterline, but that probably varies with heel angle in a hard chine hull.  Anyone know how to do the math??

[JeffM]

Read your post, Ray--amazing!  My comfort limit is not much above a steady 15mi/hr when I'm alone--and that's reefed.  Even so, I want to run the numbers.  Like many of my ideas it probably won't go anywhere.  (Ideas that don't generally shouldn't.)  But I do cruise this boat more often than daysail, and I'm planning a trip from New Bedford to Nantucket (both major players in maritime history).  (Fan's of Moby Dick may recall that Ismael and Queequeg sailed that way by packet before joining the Pequod.)  There's a fair amount of open water along the way, although shelter isn't too hard to find. 

[Charlie Jones]

Might I suggest you discuss this with the designer? He's readily available and seriously interested in his designs.

[Ken_Potts]

  When you talk to Graham you might keep in mind the thought of making a whole new centerboard with a bit of ballast in it.  Or at least remember that if you add weight to the board and don't like the results you can always build another lightweight board.

  I wouldn't put weight anywhere on a Core Sound except in the cooler (liquid ballast), on the side deck (live ballast), or at the very bottom of the centerboard.  And if I put weight at the bottom of the centerboard I wouldn't really expect an improvement in performance, I'd just expect a little bit of extra righting moment when the side deck was awash.  But I haven't crunched the numbers and I sail warm waters   I might re-think my opinion if I ever manage to get a gunwale under water (I've tried, really)...

  And definitely keep us posted on the New Bedford to Nantucket trip!  I'm envious  ;D

[Hirilonde]

Step 1 should probably be:

Might I suggest you discuss this with the designer? He's readily available and seriously interested in his designs.

Other considerations are flotation,  how the boat will sit swamped, how it will right after swamping and such safety considerations.  None of Graham's designs are displacement hulls (the B and B ones).

[Designer]

The actual ballast calculations are quite simple. The hard part is calculating the exact center of gravity in a dynamic situation like a capsize and the heeled center of buoyancy. For instance, what are the crew doing and where are they positioned at the time? How much water is in the boat and where it is situated? What is the angle of heel? How was the boat built? A couple of extra pounds aloft can change the vertical center of gravity. Does gear in lockers move or do the hatches leak?

You can see from the above that you can't just say that 51 1/2 pounds of lead will do the job. I have not capsized a CS20 but I found that during capsize tests on the CS17 that I needed to be near the tip of the board to right the boat when the masts were in the water, naturally it takes less force as the boat starts to right. You could turn that around and say that 50# on the end of the board might help prevent the boat from capsizing in the first place. The emphasis should be on "might" because as I said earlier that in a dynamic situation it depends on several issues least of which is the crew which could weigh between 4 and 12 times as much as the ballast. On larger boats with a much greater ballast ratio they have enough built in reserve ballast to overcome the dynamic issues.

Rather than fretting over trying to calculate exact numbers it is more accurate to capsize the boat in shallow waters and put weights on the end of the board to see how much lead that you think that you need. This way you learn how your boat behaves on its side and how much water you get in the boat and if your hatches leak. 

[Craig]

Hey Ray, as I recall you took about 25 with the bulb and I got about 10 arrows with the internal ballast plates.  Makes me wonder what ever became of Jim Manning?  By the by I am moving my lead into a new shorter fin keel as my old keel didn't make it through the grounding very well.  I have cut the entire keel off and am rebuilding to a new design from Paul. I was never real comfortable with that internal lead up there but it really tamed her down and improved tacking.  As Graham says, things flying about as a boat goes over changes everything in totally unpredictable ways.  At ~50-60 degrees those plates were just more stray gear.  I think internal ballast is OK for trim issues but not for any additional righting moment.

[Tom Lathrop]

This thought of ballast is a small sailboat is a new one for me.  Most of my sailing has been in small one-design racing boats where the concept of added weight is anathema.  Who would want to do that ;D 

14 years ago I built a Bay River Skiff with no ballast and no possibility of reefing other than moving masts around.  That was then, this is now, and I reluctantly discover that my taken for granted agility cannot be just assumed anymore.  So Lapwing is going to have reefable sails running in luff tracks.  My first request of Graham in designing Lapwing is that it be just as stable as the Core Sound 15 which I think I can still handle at 76.  Now, I plan to still be sailing this boat into my 80's, so some more loss of agility is altogether possible.  In that event, I will entertain the possibility of some ballast in the centerboard then.  One issue not yet mentioned is: Where is the centerboard in a capsize? 

Unless it is at max depth, the righting moment will be less than optimum.  A big aid in a capsize where righting moment is marginal (as Graham mentioned for the CS 17) is a safety line (best if it's knotted at intervals) that can be taken in hand and allow you to get all the way out to the end of the CB.  A second issue that is even more important in a ballasted CB is that it can be prevented from falling back in the slot when the boat is turtled.

If I have to ballast my CB, I will make sure that it can be fixed in place, even when capsized.  That will probably just mean a stronger than usual shock cord  on the restrainer line.

A downside of a boat like the B&B designs is that the excellent flotation chambers do make righting a boat from a full capsize more difficult as the buoyancy of the downside tanks make rolling it more difficult.  I once rolled a Windmill through 360 degrees and did not get water into my boots until the boat was back upright and I stepped back into the swamped boat.  The lucky part was that it was November and the race was in the North Carolina mountains near Asheville.  My poor crew did not fare so well so I restrained from telling him I was dry until we got back to the dock.  Oh yeah, I was over 35 years more agile then.

[PAR]

In Craig's Vacationer, ballast plates were where many Stevenson design owner's place the extra weight, well forward. In Craig's case around the base of the mast box. In this location, the added weight does very little to the righting arm (if anything), because it's only 2" lower then the CG (if in plate form like Craig's) or possibly slightly over it (detracting from the righting leverage), as if batteries have been placed on a small shelf, like other owners have done.

In Craig's new arrangement the lead weight will be nearly two feet below the CG, which will make a huge impact on a shoal draft vessel. Ray's application does add somewhat to the righting lever, though not a lot, but as much as possible considering the extreme shallowness of the keel. He may have picked up a few degrees of right arm, but more importantly, the weight drew some bury to the forefoot of his Weekender, which eased pounding and sailing lines, especially to windward. It's common practice to move crew weight forward on windward beats in fleet racers to take advantage of this, but in a little boat like Weekender, where you're married to a wheel at the back of the boat, you have less to advantage, particularly sailing solo.

[Dale Niemann]

Personally, I do not think ballast is necessary in a CS 17.  My "Lively" and I have sailed singlehanded in winds gusting up to 25 steady at 20.  I have mast tracks with double reefs.  With the boat double reefed I was very comfortable and felt totally safe sailing her by myself.  Also, I only weight about a 160 lbs.  I have had water come over the side decks only once so far.  As soon as this happened, I released the Main and she popped right up.

Dale

[Doug Cameron]

I weigh about 180 and have single-handed the CS 20 in gusty ~20-25 (with a single reef in both sails), and with a buddy in a little more.  She is wet going to the wind and reaching in 3-4 foot waves, but I haven't had trouble with water boarding while sailing on our inland lakes (at ~25 the water was streaky with breaking ~1 foot waves!).  Hold the main sheet rather than cleat it and use a tiller extension so you can sit on the side deck.  If it starts to knock you over, release the main sheet and she will come up into the wind.

As to ballast, it would slow the Core Sound down and you might miss the exhilarating acceleration in a puff.  You might take a look at the leeboards on a Sea Pearl if you must have ballast.  They have ballasted shoes on the bottom, keeping the weight as low as possible and giving some protection to that vulnerable part of the board.  Sea Pearl sailors don't have to have a downhaul on their boards either.

[JeffM]

Tom, very good points.  I didn't rig the cb lines as per plans, partly because they would have made it impossible to close off both footwells with berths.  I have a two-part downhaul on a releasing clam cleat (Duckworks) --got one on the rudder downhaul, too, after once getting the rudder stuck good on a sandbar.  I like that I can relax, knowing the cb and rudder will both take care of themselves with little help from me.  I also rigged about 8' of line to the midship gussets that I can trail overboard if I'm worried.  Haven't used them yet.  On the other hand, I just got back from a father-son weekend with 7-yr-old Stephen.  He was learning to sail to weather in the 10kt wind when he zigged instead of zagging.  10-15 gallons in the bilge and sloshing over the seats before I got the mainsheet off and tiller back.  Would have been more if my pop-top cabin hadn't reduced the amount of coaming exposed.  My fault, of course.  Scared Stephen so much he swore never to touch the tiller again as long as he lived--an oath he didn't take back for the whole rest of the first day.

Graham's idea to make the experiment is a great one.  I capsized her deliberately the first season (empty), exposing my leaky So-Pac hatches and showing it took nearly all my weight to get it upright quickly.  And I have so much loose stuff when I'm out for a weekend that I probably couldn't right the boat at all if it went over.  I'll have to find a way to secure the heavier stuff low down whether or not I ever decide to do ballast.

With all the uncertainties, I've got to choose my weather for open water trips carefully.  A quote from Charles Stock's book comes to mind: "if at first you don't succeed, quit immediately!"  And I've got to get me a waterproof vhs radio I can keep on my person. Thanks, all!