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Preventing Potter knockdowns

Page history last edited by PBworks 15 years, 8 months ago


July 29, 1991 -by- Bruce Hood


After an exciting afternoon sail in some nasty 25 knot winds in Racoon Strait on San Francisco Bay, several of us had congregated for some coffee in Sausalito. Earlier in the day, the run downwind out of Richardson Bay, under reefed mainsail and no jib, had been exhilarating. Our son, Paul, and sister-in-law, Betsy, helped balance the boat, and we had reefed down the mainsail quickly after hearing from Rob McClain that there were some very big gusts to deal with.


Then, attempting to return, as we came back out of the shelter of Angel Islands Hospital Cove, we had been hit by such fierce blasts of wind roaring down on us from the Golden Gate that I had let discretion be the better part of valor and had furled both sails. We made the bumpy 4-mile ride back using the 2 HP Honda outboard, steering with both rudder and motor tiller, against 4-foot waves and streaming whitecaps. I was glad to get us back to the dock in Sausalito, and I also was grateful for the weight of my crew who helped keep the boat balanced on the bronco ride back.


Barbara Simpson told us about two fellow Potter sailors who had recently suffered a knockdown from a large gust of wind in the southern San Francisco Bay. Their boat had turned over, taken on water in the cabin, swamped, and they had to be rescued. Their abandoned drifting boat then went aground upside down, and the mast was ruined, corkscrewed into a mud flat on the falling tide.


Though I didn't get all the specific details of what happened, I was glad to hear the two sailors made it home to safety.


As most sailors learn at some point in their sailing career, a knockdown occurs when an exceptionally large gust of wind, perhaps in combination with a wave, knocks your boat over onto its side with the sails parallel to the water. In a Potter 15 the footwell and cockpit begins to take on water. In the next instant, if a second wave rolls in to the boat, more water begins to rush into the cabin if the hatch is not in place and latched. This is even more seriously aggravated if the sailors are thrown to the low side of the boat or were caught sitting on "the wrong side." If a lot of water gets quickly into the cabin, sometimes the boat will roll completely upside down. (See Joe Osborn's article entitled Poseidon Potter in the October 1990 issue of the Potter Yachter.) If the centerboard was not locked or tied down, in that moment it may fold with a crash into the centerboard trunk. By now the boat is no longer a boat; it is a floatation device you must cling to until help can come. Fortunately help is often forthcoming, so the key thing to do should matters progress to this state is to calm yourself and stay with the boat.


Can such emergencies be avoided? Perhaps they can, if we learn from experience. I had my lesson in knockdowns in 1987. Here's the story:


Sailing alone up and down outer Mission Bay in San Diego, I was experimenting with just how tightly one should pull in the main and jib sheets and how close into the wind I could get Aillte to tack. By now, I was also curious as to just how much wind it would take to lay the P-15 on her side. Shortly, I was to find out.


It was January, and I was the only person on the bay. The surface of the water had gradually developed a sharp, shallow, one-foot chop. Here and there one could see small whitecaps. Still, it was very sheltered, actually a lagoon behind Pacific Beach, and I felt that if I dumped it I could get to shore easily. As the day progressed I was careful to keep my weight on the windward side of the boat.


It was blowing about 10 or 12 knots, moving the boat nicely, but every so often a very big gust of 20 knots or more, would sweep over the water, and Aillte would lay over on her ear. I'd instantly back off the tiller, let her luff up in the gust, and she would pop back upright, without loosening the cleated main sheet at all. This went on for about an hour, and I was feeling pretty much of a smarty-pants, as I continued to get away with just turning her into the gusts and not touching the cleated main and jib sheets. The Potter legend of the little boat's forgiving nature and great stability seemed to be working for me.


Just about the time I was feeling rather too smug about my newfound "skill," I looked upwind toward the northwest end of the bay and saw the water turn black with catspaws on the waters surface.


"Uh-oh!" I thought, "thats a really big gust coming!. Lets see if this one will lay us over," and I tightened down the mainsheet a little harder, confident I would be able to luff up at the last moment.


"Wham!" The gust hit with terrific force and, to my astonishment, Aillte was flat on her starboard side, the sails were flat in the water, and 30 gallons of Mission Bay was rushing over the starboard rail into the cockpit. There had not been a split second to throw the tiller over. I threw myself upward to the port cockpit railing, grabbed the stainless steel tubing, and vaulted astraddle then over the rail, my legs over the side, now hanging completely out of the boat, like a rider vaulting off of a horse.


My mind was racing, and I was thinking I'd need to try and stand on the centerboard, as I'd seen in sailing manuals, in order to get her back up. Then she lurched slightly back toward me; she was coming back up by herself.


The gust passed, and slowly she righted herself, pausing for an instant in a secondary gust. I boosted myself back into the cockpit as she rounded up into the wind, heavy with the weight of water in the cockpit. I lunged to uncleat main and jib sheets, and let the sails turn into noisy flags. Kneeling thigh deep in the bathtub full of water that the cockpit had become, I reached down under the water and pulled the transom plug, and she slowly began to drain herself. I quickly looked inside the companionway, expecting to find more water in the cabin. I had been lucky. With the cabin hatch out, I had only taken a gallon or two of water below decks. Gingerly, I took in some sail and tacked away from the shore I was now blowing down on. The cockpit gradually drained almost completely, and I sailed the rest of the afternoon much more cautiously, hand holding the main sheet and watching the water carefully for clues to any other big gusts that might be coming our way!


What had I learned? Had I been reefed down, I probably would not have been knocked over. Had I hand held the main and eased the sails to a near luff, the classic "fisherman's reef," I might not have been knocked over. Had there been heavy waves, a lot more water would have entered the cabin through the open hatch.


I now saw that being able to drain the cockpit quickly was a vital step, which would indicate that having the transom drain unplugged or perhaps even a much larger diameter transom drain opening would be a good idea.


Most importantly, I learned that my Potter 15 could definitely be knocked down. The little P-15's basic stability has its limits. Based on the experience of others, I now believe that had there been continued high wind and, especially, larger waves, that my Mk. 2 might have swamped completely and turned over.


Having a means of locking the centerboard in position and having the hatch closed and secured is indicated in rough weather. In high winds it is smart to hand hold the main sheet so that sudden gusts can be dumped off the sails. It is very important to learn how to de-power the sails, as well as how to power them up.


Here's a review of some preventive measures: Listen to weather and wind reports as you get ready to go sailing. A $20 Radio Shack weather radio will let you have a much better idea of conditions. Get a simple hand held wind force gauge, and read it at the dock before you leave. If the wind force is greater than 15 knots you will feel better if you reef at the dock and start out that way. If you were too cautious then you can hoist to full sails later. The Many Ways to Potter Manual is right! If the thought of reefing crosses your mind you probably should do it right away. From Joe Osborn's Poseidon Potter experience we all should now be aware of his good advice. On a stormy day always:


1. Reef before leaving the dock in high winds.


2. Tie down the centerboard.


3. Put in the cabin hatch door and latch it securely. (You can tie the hatch closed with a little piece of cord through the padlock hasp. Just attach a piece of cord to it today, and it will be there when you need it.)


Know how to keep the boat balanced. At the dock, enter your boat alone first, and check your centerboard position and rudder position, make sure they're down. Note that "all the way down" may not be as effective for high wind as having the board partially up with the leading edge at a 30 degree angle, which lessens the tripping action of the board and lets the boat skid sideways rather then heel over. Secure the board.


Now call your passenger from the dock on to the boat with you. Before leaving the dock explain to your passenger or crew the importance of them helping to balance the boat by sitting on the same side with you, or directly opposite you, promptly at your request.


Next, put on life vests. Do not take for granted that friends can swim or know anything about sailing.


Teach your passengers how to be a crew. Practice changing sides a few times while still tied up at the dock. Next show them the jib sheets and the main sheet, "the ropes controlling the sails" (mine are color coded), and explain that they must never sit on them and to get them out from under their bottoms right away if they do!


I sit as close to the side of the cabin door as I can get, which keeps me very close to the jib and main sheets, and have my friends duck under my tiller arm to sit close beside me. The tiller arm pivots upward so you can make a kind of "London bridge" for them to duck under. Soon, when they see you raise the tiller high they will take the cue to duck under it and sit beside you without further signals. The main principle here is keeping the passenger and you on the "uphill" or windward side of the boat .


In very light winds or with the wind behind you, having your passenger directly opposite you will be the best way to keep the boat balanced and flat.


I have an inclinometer mounted on the inside of the transom. This is a little gauge that costs about 15 dollars and shows how many degrees your Potter is leaning over. I explain to my friend that I will be wanting to keep the heel angle as small as possible, which will be between five to fifteen degrees. I let them know I will say "come to my side" when I want them to move, and I will want them to do so quickly and smoothly. Most people enjoy "helping you sail the boat" rather than just being a lump in the cockpit, and they soon begin to anticipate from a glance at the inclinometer the need to move a little in order to keep the boat flatter in the water. At this point caution them to wait for your signal. In their eagerness to help they may start to mo ve too early!


As an example of how important your weight and your passenger's weight can be in balancing the boat, especially when the winds are high, consider this:


A Potter Mk. 2 is advertised to weigh 485 pounds - 70 pounds in the iron centerboard and another 30 pounds in two concrete blocks glassed into the bilges alongside the centerboard trunk. This would mean she has around 20% of her weight in ballast, which is high for a tiny dinghy and one reason she is very stable for a boat of her type. Remember those "punch 'em" inflatable clowns that would pop back up when hit? That's how weight in the bottom of the boat helps.


Now let's add two 180 pound men to the cockpit. Now we have 360 pounds of live ballast - almost 75% of the total boat weight! Add to this the levering force of crew weight on one side of the boat at the rail, kind of like getting out on the end of a playground teeter-totter board, and you can see the importance of the skipper or crew being on the right side at the right time and, conversely, how strong the effect of being on the wrong side can be.


The moral to this: Teach your passengers the importance of their role and how to help.


An alternative to having your passenger or crew sitting out on "the right side" with you in the Potter 15 cockpit is to have them crawl forward into the cabin to lie down and relax.


Of course in this arrangement you want to have the hatch open or easily unlatched from inside. My wife Kathryn loves to curl up in the cabin with a bag full of books to read, where she (and the books too!) make excellent ballast right at the center-forward part of the boat, where the Potter's designer, Stanley Smith, designed the boat to carry loads of equipment. Some forward weight in a Potter is a good idea. I have seen a dory fisherman off the Isle of Barra, in Scotland, move heavy ballast stones right up into the bow in order to help hold his boat down in rough seas.


Don't overestimate the boat's capabilities. I think there may be three causes for overestimation of the Potter's stability. (Don't mistake me; the P- 15 is a very stable small boat, however it is still just that - a small boat.)


First would be Potter Legends, such as designer Stanley Smith's Potter sail to Sweden, which tend to obscure the fact that he was a very experienced, talented, and in some cases, lucky, sailor. On that famous journey he also used some very clever gear to survive, including a concrete filled tire sea-anchor suspended on lines ten feet under the boat for additional ballast. When he was swept ashore at Hvide Sande in Sweden, he deployed "roll-a-boats," which were large tubular air bladders, on the boat's sides, to help keep her afloat.


Second would be the fact that Potter 15s are indeed more stable than most boats of their type in light to moderate wind, as many of us found when first we learned to sail in our Potters. The P-15 will forgive all sorts of beginner's mistakes in light air conditions, such as "being on the wrong side." This may cause us to assume the P-15 is totally foolproof. The truth is we must learn to be more alert and smarter sailors as the winds rise.


Third is the fact that Potters look like a big boat in miniature, therefore the tendency is to infer that they will always behave like a big boat. The fallacy in this is that the big cruising sloop headed for the open ocean, which our little boats some what resemble, has 10,000 pounds of ballast lead in her keel.


In other words, most large cruising boats have as high as 40 percent of their weight in ballast, as well as having broader beams, longer waterlines, and deep keels that have significant effects on stability.


A 500 lb boat requires the use of the crew's weight as live ballast. And the Potter-15 is a 500 lb. boat.


I hope my description of a knockdown has some value for you, and that perhaps the analysis of cause, effect, and prevention will be useful in the future. My sincere hope is that all of your sailing days will be happy ones and that you will never find yourself in a situation where you have to test the ideas we've discussed!

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