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CS20 Dismasted


David Hughes
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On my 11th wedding anniversary no less; hope it is not a sign of things to come. 

 

Also, with my wife and kids (5 & 8) on board. All are fine but we did lose the sail to Davey Jones.

 

We had spent the day out on the water here in Casco Bay, Portland, Maine stopping off at one island in the morning for church and then sailing off to another to have lunch and to do a little exploring. At about 4:30 we left Great Diamond Island to head home. The winds had been light all day but had picked up to about 12 knots. I had been on a port tack for about 3 miles and was just about to tack to head to the boat ramp when the mizzen mast snapped at the center thwart just above the wood plug of the aluminum mast. When the mast went over, the down haul was still attached to the bottom of the sail and the base of the mast ended up resting on the combing with the fully deployed sail acting as a sea anchor, which pulled the boat hard to port  starboard causing the mainsail to violently jib. Between the mizzen sail acting as a amidships sea anchor and the uncontrolled jib, the boat was healing hard to port starboard. Fortunately I saw what was holding the mast and was able to release it quickly thus allowing me to come up into the wind. The sail was still attached to the boat via the mizzen sheet but now astern of the boat. I started the motor and hope to motor to the ramp towing the mast behind me but the 2 hp Honda couldn't handle it. I eventually just let the mizzen sheet run free of the sprit, came into the wind and doused the main. Once secured I came around but could not locate the sail.

 

The winds were about 12 knots, with gusts about 15-18 knots. The seas were flat. I was sailing with the main sheet in hand, easing the sheet when there was a gust. I did not have, nor did I feel the need for any reefs. Now that I can inspect the remains of the mast, it appears corrosion of the aluminum was the culprit.

 

As always, you second guess yourself and there are things I could have done differently to save the mizzen, but I was more focused on securing the safety of my family. No one got hurt nor did the boat go over; the 5 year old was crying because he got scared but the 8 year old was very helpful in keeping the boat into the wind as I doused the main.

 

Oddly enough the wife and I had been talking just before this incident that we both felt that this boat is not the one for the family. We need one with a little more cockpit space with less going on within it. I think the boat heard us talking. In a separate post I'll be listing the boat for sale. I'll either sell it as is this fall/winter or build a new mast in the spring. At least now I have a chance to use the new sail track.

 

Dave Hughes

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Wow, sorry to hear about this. You certainly did the right thing putting family first. We can always come up with other actions after the event is over and we have time to think clearly about what happened. Glad you didn't capsize!!! The CS-20 should be able to handle 4 people in the cockpit. I think this was a "freak" accident and not the fault of the boat size. Maybe a reef would have been a good idea but I have never sailed a standard CS-20. I did build and sail the one and only CS-20, Mk-2. It had water ballast and I would have either reefed or filled the ballast tank somewhere around 15-20 knots of wind. My boat had the sails with full battens. I'm sure others will give their thoughts on this.

 

Not quite sure what the  "wood plug of the aluminum mast" is.

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I also do believe this was a freak accident and frankly has no bearing on the desire to sell. With regards to the wind/reefs I never felt overpowered and was very comfortable with the conditions.

I'll see if I can attach a picture of the bottom of the mast but there is a two foot section of wood that was inside the aluminum mast base.

Sent from my iPhone using Tapatalk

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Wow, BAD corrosion. Looks like the wood plug is salt treated lumber. Wonder if that has caused the corrosion? The end of the wood plug definitely causes the strss to be concentrated at the top of the wood. Is this the way Graham specifies the top of the plug to end rather than some kind of taper?

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That certainly looks like corrosion damage caused by the salt water sitting right at the seat level due to the plug.  I bet the wood acted like a wick and just held that stuff in there where it could sit and do serious damage.  A new mizzen mast without the wood plug (mine has the plastic end plugs that Graham mills to fit) would solve it and provide years of service at a reasonable price.  How old is this mast?  Just curious from the viewpoint of a new CS user. 

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Looks like the treated lumber corrosion I see on decks, some folks will cover parts of their home deck with aluminum. It will always corrode quickly. Most treated lumber is treated with COPPER and will attack the aluminum very fast. When building a deck for a customer that has any aluminum on it for cosmetic reasons, I always separate the two with a barrier of plastic or such. Don't know if this is the problem you have or not, but sure looks like it. For the same reason you cant use copper bottom paint on a aluminum boat.

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What "plastic" is used for the mast plugs? HDPE?

 

I ask, as I made some plugs for my aluminum Spindrift mast from Doug Fir and Spruce. They slid into the ends of the mast sections easy enough, but after some moisture got to them, they swelled so much the lower mast would no longer slide through the upper mast step ring on the fore deck. I had to work pretty hard to get the plugs back out. It was about then I decided some type of stable, inert plastic would be a better choice. Thus my question about what type of plastic is being used? Either that or find a hard, stable, rot resistant wood like black locust or osage orange to turn the plugs from.

 

Scott.......on the corrosion with treated wood, that became a serious problem when the switch was made from the original CCA treatment to the first generation replacement, which was ACQ. ACQ proved to be highly corrosive with carbon steel and aluminum, and has since been replaced with MCA and MCQ. But if ACQ was the lumber used in the photo, that would explain a lot.

 

A quick summary for the morbidly curious:

 

http://www.deckmagazine.com/wood/the-new-preservatives.aspx

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I have come to very much dislike any permanent connection of wood to aluminum but treated wood is an absolute NO. I have recently been using plastic as much as I can. Home construction manuals always caution about using treated lumber against metal siding, flashing or galvanized posts etc. suggesting to at least isolate with tarred felt or similar. 

 

I used to use wood plugs and sleeves with aluminum tubes because it was cheap, easy to make and everyone has wood and epoxy. Even well treated with epoxy, it seems to have issues. Plastic does not hold moisture, swell or shrink enough to cause issues as long as it is caulked between the plastic and the aluminum. The main reason for the caulk is just keep moisture from between the two. Almost any plastic will do depending on what the job is. For end caps I have been using Starboard because it I have it and it is reasonably priced. Unfortunately the thickest that I can get is 1". If I want to sleeve a tube to reinforce it at a tabernacle, I use the next size smaller aluminum tube and and build up the diameter of the sleeve with epoxy and glass until it is a sliding fit. It can then be epoxied in place.

 

We have increased the wall thickness of the CS20 mast lower section to 1/8" because it is impossible to get the original wall thickness any more. While the new section is heavier, it is stronger and there is no need to sleeve the mizzen mast on the CS20.

 

While I hate to see this problem occur, it is heartening to see that even with the worst possible combination of materials it still lasted 10 years. If you look at the wood plug in the picture at the upper left side, you can see the dents in the wood where the oxidation kept expanding. It had nowhere else to go but into the wood because it is softer than the aluminum. Eventually after the aluminum gets weak enough to where the wood is stronger, then cracks will start to show on the outside of the tube. This mast must have been close to that point.

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