Glenmar Sailing Association
Sailing the Chesapeake Bay

Static Righting Moment

If at the dock a sailboat is pulled over by its mast, there exists a transverse force which tries to set the boat back to where it naturally wants to be. This force is named the static righting moment. It is related to, if not identical with, the Euler force. Somewhat obvious to anyone who may have tried to pull over a boat from the top of its mast, the size of this force varies according to the angle of heel. Furthermore, every boat design is different from all the others. This is a classic example of my general rule for what makes a boat go fast. The rule is “Everything matters”, but that’s a different topic and not the subject of this post

For a particular sailboat, the force changes as the boat is tipped over. When floating upright in dead calm water, the force is zero. Likewise, when capsized, the force is again zero. In between is the problem.

From figure 1 we see that righting moment (RM) can be calculated as moment arm length times displacement force. Here, displacement force is mass (displacement in \( kg \)) times gravity. Thus the units of a righting moment are \[ kg \cdot\frac{m}{s^2}\cdot m = N \cdot m. \] Since the magnitudes of these values are essentially meaningless to everyone (not just Americans), we often see graphs with the righting arm length graphed on the y-axis versus degrees of heel on the x-axis. These graphs, which are called “GZ curves” essentially describe the yacht’s stability. Gz is the traditional yacht designer’s designation for the value that I labeled d in figure 1.

Fig 1. Righting Moment. CG is the center of gravity, CB is the center of buoyancy, and d is the distance between these two forces. In most sailing calculations, variable d is named GZ and referred to as the “righting arm”. Righting moment is the product of the moment arm length and the boats displacement force.

As an example, we have the GZ graph for a J105 in figure 2. Clearly, the righting arm is very small with a maximum deviation of only a little over an inch. We also see that beginning around 130 the graph goes into negative Gz territory. That point is called the “angle of vanishing stability” with all of the values below zero termed “inverted stability”. The good news for this J-boat is that the region is quite small and it is likely that a wave would push the boat back into an area where it would get righted.

Fig. 2. GZ graph for the J105.

Paradise Lost – Or At Least Our Fishing Rods

If you have ever lost or broken a fishing rod you will understand our pain.   13 Penn Internationals gone.  

Many of you fish offshore and know the costs associated running to the canyons.   A thousand-dollar gas tab along with $200 for bait and ice are the norm.  Lures start in the $25 range with $400 for a dredge (you need two) not unheard of.  For those not familiar with the offshore world the rods cost close to $400 and the reels run in the 600-dollar range. Each!  Add 1000 yards of line and it is easy to reach $1000 per rod very quickly. We normally troll 9 lines in fair weather.

So now you are asking about the rods.  Stolen? Fire?  Divorce?  All are good guesses but let me start at the beginning.

1992   An exciting time as Ron, my buddy and co-conspirator in this rod debacle, purchased our first offshore boat, a Baja 28 center console. OK, not a great or even good offshore boat but 30 years ago the choices were few as center consoles were new to the boating scene and larger twin engine varieties were rare.  We had been running my 23-foot Imperial out to the Jack Spot where we would catch our limit of Bluefin tuna before lunch fishing Penn 6/0 Senators and using a handheld Loran to locate our destination.  Basic but as there were tons of fish back then we were happy with this set-up.  

But we all know the 2-foot boat monster that demands a new vessel be purchased every few years which is larger and more expensive.   We justified this move as the new boat would have radar, a life raft, and twin engines but secretly our real reason was to pursue Yellowfin Tuna, Marlin, Wahoo, and Dolphin that resided 40 to 70 miles offshore – out of reach of our little 23 foot Imperial.  Equally important was to maintain our appearance and upgrade our Penn Senators to those expensive Penn Internationals I mentioned earlier.  Gold Penn Internationals do look cool and we all know how important that is!

I know, what about the lost rods??  I’m getting to them.   

We fished this new boat for 13 years trailering the boat to Hatteras winter thru spring and fishing Ocean City in the summer and fall.  Great times but a little scary as this boat was not designed to fish 8-foot seas in January off Cape Hatteras which we did.  Frequently.  Over the years we lost many fishing companions as they came and left with remarkable frequency.  About as often as we lost rods….   While Ron and I were excited to run through the inlet and catch 50-pound tuna we found our guests enthusiasm decreased in proportion to the size of waves we fished. 

This new boat was great, but our techniques were still in the learning curve and the reason for our first lost rod.   It was around 1994 when we, (me, Ron, and Bob), were fishing off Hatteras one cold and windy April afternoon.  Rain was not just falling but coming down in buckets.  Hard to tell it was raining as sheets of water came off the bow as we trolled through 20 knots of wind and 6 footers.  Around 1 pm we had a quadruple knockdown of 50-pound yellowfin which would normally be great but not today.  We each reeled in a fish and then started searching for the fourth rod. What we found was an empty outrodder which was pointing aft and sitting 6 inches lower than normal.  If you are not familiar with an outrodder it is an aluminum bracket that fits into a rod holder and allows you to position the rod to point directly out from the side of the boat.   Great for increasing your spread of lures but when the tuna hit and pulled hard on the line which was tight due to our drags being in the strike position the tension caused the rod holder pin to snap allowing the outrodder to swivel backwards and the $1000 rod and reel to shoot overboard and to the bottom of the sea.  

Now some of you are reading this and saying, “they should have had safety lines on their rods.”  Yes, we should have but this is early in our offshore career and remember we were pioneers in this sport as most who ventured offshore went in charter boats and very few private boats ran further than the 20-fathom line.  But we learned our lesson and built safety lines with snaps and swivels and used them in the years to come.

A safety line did not help the loss of rod number two.   One summer day found us anchored 42 miles off the coast of Ocean City chunking for tuna at a spot called the Hot Dog.  A very popular location even 25 years ago as it can hold thousands of hungry tunas and this day was no exception.   We were enjoying a typical day of hooking tuna that would follow our chunk line up through the depths and provide us some exciting moments.  As a little background I would like to share that Ron and I took pride in our skills and approached all tasks with enthusiasm and perhaps a little too much exuberance.  This day was no exception as when one of our guests pulled a tuna to the surface I gaffed and lifted the 65 pounder over the gunnel in one big swoop.  Unfortunately overtop my head was a rocket launcher filled with International rods and reels.  My gaff caught one which crashed down on my head and immediately launched itself overboard along with a $200 pair of sunglasses.  We did not have safety lines on rods that were stowed in the rocket launcher.  Rod number two gone.

But all this was just a warm-up for losing the next 11 rods.  We had graduated from the minors into the majors and decided that losing one rod at a time was for amateurs.  We were ready for the big leagues and proved it a few years later.

2005 found us entered in the White Marlin Open.  We had three friends fishing with us and a great week of weather ahead even if a bit choppy at the beginning of the week.   Our first day of fishing was not spectacular and at noon we decided to move in from the deep, (we were fishing the Washington Canyon), and fish the tip of the canyon between the 50 and 100 fathom line.   At 3:30 pm it was lines up as deemed by the tournament rules, so we reeled in and started the 65-mile run back to the inlet.   It was a beautiful sunny day so Brian, one of our guests, and I sat in front of the center console enjoying a cold beer as Ron steered a course for home.   

Now is a good time for a lesson in boat dynamics, physics, and stability.  Expecting fish, we had filled the fish box with 200 pounds of ice which was in bow of the boat.   A small cabin, also in the bow, was loaded with gear and a 100-pound life raft.  Brian and I were sitting in front of the center console and I may have consumed a few more cheeseburgers over my lifetime than was good for me and I will just say we added a few hundred more pounds to an already overloaded bow.  The wind was against the waves and what had been fun rolling 6 footers now got a little steeper and less fun and caused us to slam and climb up the backs of the next waves.  See where this is going?

We climbed up the back of one of these steeper waves and zoomed down into the trough as we had been doing for the past hour.  The difference was this time the bow dug in and a wall of water shot back through our open boat filling it and rolling it over as the next wave caught us seconds later. Within 10 seconds our Baja was upside down and I was 100 yards away as that wall of water that came over the bow blew me out of the back and broke a few ribs while depositing me astern of the overturning boat.

Story getting a little better eh?

So, I find myself treading water without a life jacket and with broken ribs far away from our boat. I was surrounded by items that had also been washed overboard and spied a can of WD-40 which I shoved into my shirt hoping it would provide at least some flotation.   I then spotted the back seat floating nearby and gave it my all to swim to and climb on top of.  Now that I knew I was probably going to survive I looked around and spotted my buddies clinging to the upside-down hull of the boat bobbing violently in those 6-foot seas.  I counted heads and saw we were all accounted for but not out of danger as we were 45 miles off the coast and surrounded by a blood / bait slick being constantly discharged from our sinking boat and the gashes on my mate’s limbs.   Again, for those of you not familiar with offshore fishing a great place to fish for sharks is the 30-fathom line which is where we decided to park the boat.

Our rods?   11 Penn Internationals.  A mix of 50s and 70s.  We were done fishing so no safety lines and when a boat is upside down, they fall out.   Poor design on the part of the boat manufacturers but in their defense a low priority by most of their customers.

And us?  We were very lucky as our moving to the 50-fathom line saved us. At the 3:30 lines up we were inside of the fleet and on a rhumb line from the canyon to the inlet and confident a boat would venture by eventually.  About an hour after our mishap a fellow tournament boat, “The Cat in the Hat”, from Montauk, NY swung by to see what was floating off their bow.  What they found were 4 guys clinging to the stern of an overturned boat and one fat guy drifting off into the distance on a boat cushion.  

I would like to end the story by sharing that we saved our boat and retrieved some of our gear including a few rods.   Nope.  The next morning, we were awakened by a call from the Coast Guard alerting us that our boat was still floating and was a hazard to navigation and asking what we were going to do about it.  We made a deal with a salvager but had to alter the contract after he found the boat in worse shape than what we described.   It seems a vessel had lifted our boat onto their deck with some type of crane and cut everything off the boat that had any value.  Gone were the engines, props, T-top, leaning post, etc. and our gear (and extra rods we stowed in the cabin!)  The damaged hull was then thrown back into the water and still had to be towed in as it did not sink and was still a hazard to navigation.

Is there a good ending to this story?  Well, kind of.   We lost 11 rods that day but what we did not lose was even more important.  While we laid in the hospital being patched up the attending physician shared that he hoped we did not have the winning fish on board.  Confused we asked him why he would wish such a thing.   His response was to remind us that losing a boat and all our equipment was bad enough but also losing a million-dollar fish would have been too much.   I guess it was a good day after all!!

The article was written by Joe Borrison

Henry’s Basement

A few nights past, I was knocking about in Henry Roesner’s basement and we came across a Courseboard that I hadn’t seen before.  Henry told me where it came from.  I don’t rightly recall where that was, but it reminded me that there is quite a collection of them on this site and I requested that one to add to it.  Now there isn’t anything particularly special about this Courseboard.  It is dated April, 1989.  By then, I had been a member for a few years and many of you had been a member for eons.

Anyway, I went online today and added the document to our online Courseboard library ( ) but was more than mildly annoyed to see that I couldn’t fetch it back again.  This led to a little poking around in some files and discovering that none of the last 5 Courseboards could be fetched as a historical document (as in using the link above).  All of the old ones worked just fine, but nothing new.  After a short but intense session relearning how to debug php code, I was able to find the problem and apply a band-aid.  Interestingly, however, the fix is truly just a band-aid.  We have WordPress code piled on top of php code piled on top of html code, and spread out all over the place.  I always think “Well one these days I’ll go in there and clean it all up, but just like the second garage, those days just don’t seem to be coming.   If you’ve lived in a place long enough, there are buried treasures that you may dig up and know for sure that you’ve seen them before, but have no clue why you still have that stuff.  In a website, the same thing occurs, but if you throw it out, not only might you need it the very next day, but worse, you may find that you were using it all along and just didn’t know.

That kind of happened with this Courseboard.  I found a couple of files (real important ones as it turns out), that were quite literally in the wrong place and were in use.  I know they need to be moved so that me, or any other half way competent coder would know where to look,  but – they work fine where they are and who knows what would have to change if I relocated them.  Maybe someday I’ll clean it all up.

About that Courseboard, April, 1989.  I took the time to read it and guess what.  It’s no more interesting than the current ones – probably less so.  Here is a direct link if you are also inclined:

There were a few other things that we came across at Henry’s place, and I will comment about those in a future post.

Big Boats can go fast!

Check out this clip.

Moonlight Run

Some of you may have participated, and others may not have been aware of it. But, there was a Sippy Cup race that was intended for the smaller boats on the upper bay that did not want to race in the grueling Governor’s Cup race to St. Mary’s College. The Sippy Cup was held for 10 years, but is no longer. The Northeast River Yacht Club has picked up the peices and is hosting it’s replacement, now called the ‘Moonlight Run Sail Race’. It will be held on Aug. 16th. It is a night race, starting and finishing in the upper bay with festivities after the race at NERYC’s club house. See the flyer below for more information. I hope you can do this race and support our fellow clubs on the upper bay!

Portsmouth Brunch

The Portsmouth sailors had a very successful organizing brunch at the home of Terry Westhead and Mark Roesner last Sunday. There was a lot of food but somehow we ate most of it. A few changes were discussed about starting location and boat storage at the sailing center, but I will leave those details to the Portsmouth Captain.

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