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Tang Bolt and mast strength

Jean-Luc Van Den Heede's recent problem with his lower tang pulling down through the mast after a severe knockdown during the GGR got me thinking about the loads the lower tangs see. I've heard of example's of the tang bolt or tang breaking but this failure mode is less common and it acts as a useful data point for the loads in a rollover, Since the rest of the rig survived we can narrow down the loads and failure points.

This is a rough drawing of the setup he had, plenty of unknowns but I have made some educated guesses

8mm rigging wire
16mm tang bolt
4.8mm Monel rivets

8mm wire fails at around 4.6 tonnes . Since there are two shrouds the maximum load would be unlikely to have exceeded 9.2 tonnes and was probably a lot less than this. But the wire yields and would begin to show permanent elongation at approximately half the breaking strain, or in this case a total load of 4.6 tonnes, though it is unlikely the load is evenly shared between both shrouds.

The failure mode was the tang bolt pulling down through the mast 50mm on one side, presumably the rivets must have sheared off and all the load went onto the aluminium wall.

Here is the results from a quick spreadsheet I knocked up.

So if we assume a 16mm tang bolt we see that its Shear strength is about 5.7 tonnes. But since it is in Double shear due to the external strap it should be able to take about twice that load, more than enough to cope with the maximum shroud load to failure.

Look now at the bearing strength of a 4mm wall section mast, It yields at 2.5 tonnes and fails at 3.9 tonnes. The other side attached by 7 rivets fails at between 2.3 and 3.8 tonnes depending on the size of the rivet. (rivet breaking loads from Stanley). There is also likely to be some clamping force helping to secure the plate to the mast, but this is very hard to calculate.

My guess is that the mast wall yielded slightly, putting more of the load on the rivets. this may have happened earlier, as the mast yields at a reasonably low load. When she got knocked down the Pop rivets sheared placing the full load onto the mast wall which tore down, exceeding its bearing stress. the load may also have permanently stretched the wire, and in his latest phone call, he mentions the D2 (Diagonal 2's, discontinuous intermediate shrouds) needed tightening indicating they also may have yielded slightly. I am guessing they are 7mm wire so 3.5 tonne break, 1.8 tonne yield.

We can also see the required wall thickness to support the full load of the bolt alone, in the case of a 16mm bolt we would need a 9.1mm thick bearing surface, but if it's in single shear you would need to upsize to a 19mm tang bolt and make the wall 11mm thick to match the strength of the shrouds.

This mast was absolutely bulletproof for all normal sailing loads, but the incredible shock loads placed on the mast when it hit the water found the weakest parts.

Of course, the failure of the mast wall may have relived the loads enough to prevent the shrouds from failing. Perhaps if the tang had been stronger the whole rig might have been lost?

I am not an engineer, I do have some basic tech school training in these types of calculations (1.5 years at Polytechnic studying a diploma in mechanical engineering and drafting) but not enough to be happy if you use these figures to design anything without first having them checked by a Qualified and competent engineer. Also working with figures past yield or maximum design stress is not good practice. To really nut out what happened the mast needs to be analysed and the calculations made with much more advanced non-linear techniques like FEA.

I'd be interested to hear any real engineers comments and observations.

A dinghy to row. Galifreya

Most dinghies today aren't designed to row, Even ones that you might think are. I was lucky to grow up with two nice rowing dinghies and no outboard motors.

Part of the decision to go for a bigger boat was to be able to get a bigger dinghy on deck that will row much better than the 8 footer on Snow petrel. I can fit a 12 footer onto Snow Petrel II.

Anyway, A good friend was going to build an Auk for his beautiful atkins cutter. I couldn't help myself designing a 8.5x4 foot rowing dinghy that was more suited to him.

Here's the result. I called it Galifreya to go with his yacht Galifrey.

 It had to look good, especially upside down on his deck, And fit under the boom.

The dinghy also had to row exceedingly well, He has a bolger light dory and that was the standard that it was being judged against. But more stability was needed, and better towing. He wanted high freeboard to get a comfortable rowing position,

I chose to pull the quarters up to reduce wetter surface and transom drag when heavily loaded. The waterline beam is also pretty narrow, but wide enough to carry the weight and give about twice the initial stability of the bolger light dory. Most small rowing dinghies have broader low sterns to carry more weight and give more stability. Good for outboards and sailing but very very bad for rowing, especially when loaded.

The bow is fine underwater but rapidly flares to a fuller bow to lift it over any waves and stop bow steering when towing. Coupled with the high freeboard the dinghy is very dry, The sheer is pretty flat to give the comfortable rowing position he wanted, And to give more capacity for deep loading.

 The keel is long and straight with a big skeg. It makes it track very well. possibly two well for my liking, I would probably take 25mm of the skeg and 10 mm of the keel to make it more nimble. But it is a joy to row, You don't need to focus on keeping it going straight. Even when gliding or with a beam wind. It surfs well down the smallest waves. And is stable enough to stand up in.

 Happy! A smooth wake and nice curl to the bow. The dinghy rowed better than any other I have tried in this size range. Next we need to do some speed trials against other dinghies and row it in all sort of conditions but our first trails were better than I could have hoped. Just needs some paint and a few finishing touches and she's done.

The lines plan, the waterline shown is roughly with two light to medium weight people onboard and no gear. It was not a quick and easy dinghy to build, but it is within the capabilities of most people. I generated offsets for the hull planks which where mostly pretty close, except at the bottom of the bow, where they were about 10mm off. It is 6mm ply over bulkheads and temporary stations.

Weather to go? and the herd instinct...

Pondering the weather?

I think we have all been there, in that anchorage or port - pouring over forecasts , grib files and weather maps, trying to decide whether to go or not. Somehow the perfect weather window always seems to have just gone or to be another week away. Our options seem to contain many uncertainties, despite (or maybe because) of the much more accurate long range forecasts available these days. The decision to go is often complicated by other boats all thinking about heading of as well.

The Herd Instinct

It always slightly amuses me how much sheep thinking is coded into our DNA's (or is it human thinking by the sheep?) and I realise I'm not immune to this either. You get 2 or three boats in an anchorage waiting to depart, and everybody starts in subtle ways to find out what the other boats are thinking, and when they are going, there is much at stake in these discussions, ego, fear and respect... This doesn't only apply to other vessels, a similar dynamic can happen between individual crew on a boat.

Ego, comes into it because people don't like to be thought of as wimps, so (typically) the blokes like to make light of the forecast... 25-35 knots, no problems, been in much worse than that many times, we'll be right.. Another factor with the whole ego thing is that it can trap you, if you have stated loudly that you plan to go tomorrow- to other people who thought the following day might be better, it can be hard to then change your mind to agree with them when they are right...

Fear, it’s funny how travelling in groups somehow makes us feel less fearful, watch a group of penguins about to jump into water that may contain a hidden leopard seal to see the same type of reactions... Be careful that you are not leaving against your better judgement because you are afraid of being left behind... Or not leaving on a good forecast because no one else is...

Respect, saying we are going to do something different from others is like saying you think they are wrong... once we are locked into group discussions this becomes a powerful factor, it can be hard to say no.

The factors to consider between different boats

Factors to be brutally honest about are our boat, our crew and our rush factor.

Our boat- Is it bigger, smaller, faster, slower, well found or dodgy

Our crew - it is the hardest one to be objective about; we all like others to think we have heaps of experience, it's that ego thing. And they may be playing the same game, the blind leading the blind…

The rush factor - How much of a rush are we in, have we got pressing deadlines, have we been waiting for weeks already. How much do we motor vs. slop around in light air? Are we ready to go yet or do we actually want to spent a few more days in this place....

Ultimately the decision to leave should be an individual one, and one that you are comfortable with. Don't let that Gung-Ho delivery crew make you feel like you are cowards. Or that boat that has been waiting for 4 weeks for a perfect patch of weather make you feel worried about the conditions as long as you are confident the weather is OK for the boat and for you. Also try not to put pressure on other boats to follow your lead; they need to make up their own mind...

Advantages

In saying all this there can often be advantages to discussing things with others, such as

•          local knowledge
•          A bit of a reality check
•          other boats may have better or different weather information
•          It is social and you get to know the crew from other boats.

You may even end up sailing at the same time and this can be fun (or a nuisance as they call you up every half hour to give you a position report and then expect you to slow down and wait!) If you are lucky you can get some good photos of each boat sailing…

Getting it wrong

I stuffed it up badly once (actually more than once but this one sticks most in my mind). I knew I was making a mistake at the time (Stupid hey...) I had a deadline, impatient crew and a bad forecast. Another boat was going, they reckoned it would be fine, and they had no engine - my ego didn't like that... My crew were starting to think I was a wimp and were really keen to go. I knew I could handle the conditions ok and I had faith in the boat, but I really thought the next day was a much better idea... It looked very unpleasant out there and the clouds were racing overhead. With a sense of foreboding we sailed. The crew got greener and greener as we left the lee of the land but their insistence on sailing meant they couldn't really bottle out, I should have taken the initiative and pulled the pin - it’s the skipper’s job, but I didn't want to be the one to bottle first. 

To windward the sky got darker and then without warning (actually there was good warning, I just ignored it) a solid squall came through flattening the boat. The seas rapidly built, steep and nasty, one throwing us well over and making me think the windows should have popped out. It didn't ease up any, so after a good struggle I clawed down the spitfire jib (we already had the third reef in) and we slogged our way back to the anchorage, motorsailing, arriving very wet and tired at midnight with our tails between our legs. The other boat ended up being towed in...

The next day the wind had eased somewhat and it looked much healthier but the crew were now very wary, they took some convincing before we headed out… We ended up having a great crossing, why I had headed out the day before with that forecast I don't know (actually I do, It was my ego, and I should stop listening to it.)  Now I must say that despite this incident they were a fantastic crew, and I enjoyed sailing with them. It was my error and ego that led to a miserable night.

Doesn't look so bad? Don't take the red arrows lightly...

Getting it right

I remember sitting at the Melchior Islands in Antarctica. We had a shocking system coming though the Drake Passage; the Grib files had it intensifying rapidly into 50 knots or so of southerly. It is about a 3-4 day passage and the trick is to try to time it to avoid a nasty westerly at Cape Horn, it's not normally too hard but in this case the timing would have to be perfect. Too early and the southerly could be dangerous, too late and the next westerly could make it difficult to lay the shelter under the lee of the horn... To make matters more complex five crew had flights from Ushuaia in the next week - And the new crew were to join shortly after...

I was pretty happy with when I had to leave, but I wanted to talk to Eric from Vaihere, he was heading off soon and had much more experience in the area than me. Vaihere is a bigger and faster boat than us and he was planning to leave 6 hours after me. 

It was good to talk to him, because it showed me that he didn't much like the situation either (very bad...) so there was some justification for my nerves... But we were both pretty confident that we could time it right for our respective vessels, and cope with the situation if it didn't pan out how we thought. He waited and I left. He arrived at the horn 2 hours after me, and I was probably an hour or so later than I should have been (because it was starting to get very nasty); it blew like stink that night. Vaihere kept going and looked magnificent sailing past in 50 or so knots of westerly. But I was glad we were tucked up in a safe anchorage.

What worked well about talking to Eric is that we had both dropped our ego's, he admitted that it looked nasty, and he was worried about it, as was I, we weren't trying to impress each other. We both had a pressing need to get away, but we were prepared to wait if needed. And we were aware of the different speeds and capabilities of our boats. My plan was to head out, and assess the situation in 12-24 hours, if I thought I couldn't reach the horn before the westerly’s started to crank up I would head back to Antarctica and cancel the flights... I had not used Eric to prop up my decision, but I wanted the benefit of his local knowledge of the Gribs and their relationship to the local weather systems near the horn.

Anchor Ratios for the bored

Warning, This post contains maths, and other boring concepts, it some of the information has been superseded by better formulas and more information. another post on this will soon follow.

I have been playing around with Excel, you can do interesting things on it if you are bored enough (I was on a plane, planes are boring). Anyway I had been pondering a thread on Cruisers Forum regarding is a big anchor better than a smaller one?

I was keen to see how the law of Mechanical Similitude  applies to anchors and boat sizes.

I found it very interesting, much more interesting than the plane, although Karen, sitting next to me did not share my excitement...

Anyway, for me the discovery's were interesting, if you take the view that holding power is proportional to the anchors blade area (edit: I have since found that it needs to include depth of set as well, so it is normally proportional to the weight, or area times depth of set) then the benefits of going larger are not as great as you might at first think. In my case going from a 20 kg anchor to a 30 kg anchor then the weight increases by 1.5 but the anchors area only increases by 1.3. Useful, but not as big a benefit as at first you might think.

Now to get a bit controversial and way out of my depth, but thinking about what actually holds anchors into the seabed in some bottoms it occurred to me that the shear strength of the seabed might well play a part. and if that's the case then the circumference of the anchor would play a part in it's holding by defining the shearing boundary. Now the little bit I read on soil dynamics on Wikipedia confused the crap out of me so don't go thinking I am any sort of expert...  But the bad news for big anchors is that up-sizing the weight to 1.5 only gives you 1.09 more shear strength. Interesting, not sure how relevant it is, in soft mud area is critical, in clay or firm mud maybe shear strength comes into it? Any soil technicians out there? (edit:still havent found out anything about this, but probably not a big factor)

Thinking more about it the shear strength would also include the thickness of the substrate it needs to pull through, so it may increase as an area rather than a length, the same as the surface area of the anchor...(edit: now I am getting closer... see the next anchor post, comming soon)

I was also curious to see how the colossal anchors carried by some bigger cruising boats like Morgans Cloud and the Dashews stack up against the boat weights and windage. Now boats don't scale properly, no smart designer is going to directly scale up directly. What normally happens is boats get relatively narrower, lower and lighter as they get bigger, so my scaling is rather crude, but it is interesting to see what happens if I scale Sunburst up to 60 foot (18m) by a factor of 1.50. the displacement goes up to a whooping 33 tonnes, 3.37 times more to about 34 tonnes. The windage only goes up by a factor of 2.25. This would require a 70kg anchor to keep the ratios about right. (edit: I think I have this sorted out now, anchors scale in proportion to their weight. so not quite such a big anchor would be needed)

The biggest winner with a big anchor is the tip loadings which scale with the surface area, double the weight gives you 1.59 times the tip load, provided your dip is as sharp as the smaller anchor. This will help your setting in some bottom types since the extra weight of the anchor helps drive this sharp tip into seabed.

Now it also occurred to me in a light bulb moment during a restless nights sleep pondering exciting things like anchors that we compare yachts ratios with numbers such as the Sail Area/displacement ratio, and Displacement/Length ratio. So why not compare anchors to boat size the same way, this would stop half the internet arguments about if your anchor is to big or to small, we could exchange our numbers and we would know exactly where we stand on the continuum of permanent mooring to toy anchor.

So here are a few ratios to play with, they might make sense number wise or just be weird, maths isn't my strong point, I would be interested to hear your Ratios.(edit: I now have a better ratio Length squared/Anchor Wt, should be about 35 or less, 7 or less for metric)

Displacement to Anchor weight ratio = Disp (kg)/Anchor weight (kg)

Displacement to Anchor Area = Displacement (tonnes)/(Anchor fluke area (cm^2)/1000)^(3/2)

These are the easy ones, windage is another critical factor, probably much more important than vessel displacement, depending on the situation. I got a crude idea of my windage in m^2, took side windage and head on windage and averaged them to reflect the normal anchor ripping out angle of 45 degrees. made a bunch of crude assumptions about rigging drag and then even I got bored... So I have a crude guess really. keen for any input on better ways. I need to refer to a few yacht design books to see if I am ballpark but hey a guess done with maths is much better than a guess done by.. well just guessing, isn't it?

So the ratios for windage are

Windage to anchor area ratio = windage (m^2) / (Anchor fluke area (cm^2)/1000)

Windage to anchor circumference = windage (m^2)/(circumference (m))^2

Anyway, even I am getting bored now, My guess is the first few people with a real maths and engineering background will die laughing and probably make spot a heap of mistakes in my logic or my math, but if by some chance the laughter isn't fatal, please make comment so it can be improved or deleted.

Here are my results after some tweaking of the original formula to get the brackets in the right place.. DUH

Cheers

Ben

PS can't work out how to add the spreadsheet to this blog. Any ideas?

A new boat!

Like a hermit crab for a while now I have been feeling like I have outgrown my shell, she feels too small and not exciting enough... Well I have just bought a new boat, or at least I will have in a few days when the bank processes my money transfer!

In my last post I had a list of a bunch of desired features of a new boat, most of which did not make for a cheap boat. Looking back over the list I think I have ticked most of the boxes, or at least the boat has the potential to tick them one day.

Thinking some more about it I guess one of the main goals is to be able to lift my sailing average on coastal passages from about 50-60% up to 70-80% so good light airs and windward performance are important. Also more space for a fully separate toilet and shower and at least 2 separate cabins and room for a kayak and a decent hard dinghy on deck was needed.

Those fellow boat nerds out there will immediately recognize the dreaded lines of an old IOR Two Tonner. yep.. Hrmm OK so they roll like pigs down wind don't they? err yep.. and.. they Broach at the blink of a hat right? (slightly red faced).. Yes so I am told.

Well that's the negative, the positives are the fantastic heavy air windward performance,  the huge amount of room, the strength of all alloy construction and good light air performance. Did I mention that I could also afford her, a big factor for someone with a simple lifestyle and aversion to debt like me, and I can afford to do what is needed to make her a simple fast cruising boat.

She wants a proper interior with insulation (one day), new rigging (urgent), a bigger engine (eventually), a redesign of the cockpit area plus dodger, and the sailing gear sorted for shorthanded work.

Strong 6,5 and 4mm Aluminium, exceptionally
well built by Noel Wilde in Melbourne.

A basic but functional interior. Those chainplate stays look annoying and she will drip condensation everywhere in tassie... 

One day maybe a lift keel could be retrofitted, so I will build the interior to suit a centerboard case in the distant future.

The bad downwind habits may be able to be improved by dropping the spinnaker before the wind gets over 15 knots and reverting to my slow trundling downwind with a poled out headsail. A wind-vane and auxiliary rudder will also help. A friend of mine has a boat with a couple of dagger-boards down aft for running. Apparently they also help considerably...

Anyway no rush, I will sail her for a few years before I do anything to drastic, She is quite serviceable as she is, It will take much time and money but I think she could be a great fast and fun cruiser to sail offshore and inshore.

Oh, by the way I now have an exceptionally tough, go anywhere red yacht for sale at a giveaway price to the right adventurous soul...

Edit, Snow Petrel has just sold, the new owner is Dean, he will cruise around Hobart way, learning the boat before heading off further afield. Sad in some ways, but it opens up a new door, and now I can afford to do some of the improvements to Sunburst.

Cheers

Ben

That dreaded POX

I think I have contracted that dreaded scourge of boat owners. I have all the symptoms, excessive time on the computer, eagerly awaiting emails and attachments. Carefully scrutinizing picture after picture of boats, a dreamy look on my face, with screwed up sketches of possible modifications strewn around.

Poor Karen has to put up with me constantly asking if she likes this or that boat... I almost wish she was suffering from the same illness.  For a while I thought I was alone with this syndrome, but I heard some friends are also suffering the same malady, it must be going around. They have even found a name for the sickness, the dreaded 6 foot-itis. 

Of course Mike and Larissa deserved to get it, spending years living on a 34 footer with two kids is bound to bring on such an nasty affliction, but me.. What did I do to deserve it?

Anyway look on the bright side, it could be worse, it could be 10 foot-itis or even 20 foot-itis.

So yes it is official, I am looking at other boats, nothing to serious yet, it's a big leap. But I always saw Snow Petrel as more of an interim boat, at some point I need to get serious about things and make the plunge. Boats being so cheap at the moment is certainly a factor. I just have to make sure 6 foot-itis doesn't develop (as it so often can) into that most fatal of diseases, the dreaded Dreamboat-itis that will leave me crippled, my back broken forever under a mountain of debt.

I have looked at catamarans, old racing boats, even older rusty cruising boats. My wish list is as follows :

1. Cheap
2. Strong
3. Fast and easy to handle
4. Shoal draft
5. Beautiful
6. Low maintenance 
7. Good light airs performance 
8. Roomy and comfortable at sea and in port

I am guessing I will be looking for a while, but if you hear of such a boat please let me know right away.

A tale of fire and ice

Well, not really much ice, more sort of rain and some cold wind but hey.. got your attention. But the fire, yep a real fire on the boat!

Intentional of course, and nicely contained in the welded metal firebox, nicely warming the boat to 29 degrees, and warding of that icy weather. Finally after many years of procrastination the wood heater is on the boat, and working exceptionally well.

It replaces the smelly little Taylors diesel heater that I never really bonded with. In fairness I did buy it from a garage sale for $100 and it really needed a bit of an overhaul, a very small diesel leak used to develop when it heated up and it gave of a slight whif of diesel... Yuk. 

This wood heater was of my own design, (or rather adapted from my friend Adrian's design). It is just big enough to fit a normal sized log, and has a  mesmerizing window, a secondary burning chamber, and enough controls to keep a concord pilot busy. 

I love it, I love the slightly smoky warm fug inside, the flickering of the flame through the door, and the radiant heat. 

I love the hot kettle simmering away on the top. I love playing with all the controls, stoking it, lighting it, and the lazy way the smoke curls out the chimney. Shame it has taken 6 years to build, and now I have it installed just in time for summer...

See the post on welding stuff for details of the tools I used and a photo of the door being made, I managed to source some heat proof glass to fit inside the scrap stainless steel door. It's welded up from 6mm (1/4") mild steel plate (that I also got from adrian, thanks mate!), and it weighs a ton.

The installation is not quite complete. Hopefully soon the stainless steel heat shields will be fitted instead of the cheap galvanized one, and some tiles will be glued on the floor. I also need to make a new stack top, the old one was washed overboard in the knockdown on the way to Antarctica. And finally weld up some fiddles and guards. But all in good time, I guess I have until next winter!

Maybe amongst this hive of activity I will find time to post a few things on here, my apologies for the long lapse. Some time soon my old man will get his website up and running about his book "Snow petrel". So soon I can post a link to that, and with luck it may stop him harassing me to put something about the book on here...

Ohh, Important stuff I nearly forgot, Playing with fire is something most of us grow out of when we are about five, I clearly have not yet achieved this level of maturity. However I am very careful about shielding, and do not leave the fire unattended. I was told by a firefighter that wood can slowly change into a more flammable state after years of exposure to "safe" temperatures. Then one day it bursts into flame at the same safe temperature it has always been exposed to. A homemade wood heater is also liable to nasty antisocial habits like belching carbon monoxide, flames, and hot embers, or worse. Be careful... 

A tale of woe... Oh and RAIN

Well It's raining outside, and I have antifouling to put on Snow Petrel... Forecast - rain on and off for the rest of the week. I should have put the paint on yesterday morning before the rain started, but I hadn't primed any of the bare metal patches (only some small pinholes 1-2mm diameter) so I did that instead.

So now if I can get the bottom dry enough for one coat of antifouling I will be right. If not well, I'd rather not think about that, be positive, you know.

On the plus side I have taken off the tiller and planed it back and reshaped it. It has always been a bit of a hefty lump of wood. Rather ugly but strong. I have never gotten around to doing anything about it because I want a telescopic fancy aluminium tiller so I have always seen this as a temporary tiller. Anyway I decided I needed to have at least one nice looking thing to cheer me up and I have planed it down to a nice shape and started varnishing it. As soon as I started planing it I realised they did a nice job of laminating the tiller with alternating light and dark strips... WOW it's going to look great. I have put alot more taper into it and it will fit the hand better then the original old lump of wood.

It's amazing what hides under the old grey wood...

I have spent alot of time investigating stray currents because they may be the cause of some of the failure of the base layers of paint. I think that it is mostly due to the old age of the bottom paint and million layers of old antifouling but I want to eliminate any stray currents before I strip all the paint of and start again. It would be heart breaking go to all the trouble of doing this and then find the new paint coming off as well... So if anyone has any tips on a good stray current meter or using a multimeter to find leaks let me know. Some interesting sites on stray currents; this one seems very good, Yacht survey - and I would like to find out more about these meters and if they are any good or just a dressed up multimeter (I have heard one fellow around here swear by them). What other options are out there for testing? I guess my anodes have started working for the first time in 7 years or so so that makes me slightly suspicious. But they still aren't working hard.

I also would like to hear from anyone with information about sandblasting vs. mechanically cleaning with a sander. Or other options such as ultra-high pressure water blasting, soda or dry ice blasting. More research for me before the next slip in six-eight months time...

Anyway the sun is peaking out... time to head down to the boat

Cheers

Ben

BTW what does the rest of the world call coming out of the water, we call it slipping the boat.

A long time...

I just looked at the date of the last post and realised what a long time it's been since I last posted. Well I kind of knew it has been a long time, and I have written two big posts (and re-written them at least three times), But for certain reasons (which I may or may not reveal) I have not posted them yet... sorry.

So I am kind of firing this off to let you know I am still alive. (I am) But I did have abit of a fright the other night, seeing lots of water in the bilge I tasted it to see if it was fresh or salt, (kind of more fresh, not salty so had another taste to check) and looked for the leak. I couldn't find any leak anywhere so I pumped it out and went home...

Light-bulb moment at 10pm, cooling water from engine, antifreeze... toxic? Panic google search YES IT IS TOXIC!! !@#$%

Anyway to cut along story short Karen drove me down (I was suffering from extreme hypochondriac syndrome) I got some samples from the bilge and some salt water I stuck them both in the freezer and they both froze OK. Also the Cooling water was still full and very green (the bilge water wasn't green) so I think I am not going to die (from that anyway).  Many lessons learnt here, many that I should have learnt when I was two, like don't swallow anything unknown.

But seriously I was surprised that 30mls or so of antifreeze can be fatal, but relived that the cure was strong alcohol... so I decided I'd better have lots of the cure just in case.

As well as rewriting posts and trying to poison myself I have just put Snow Petrel up on the slip (the hard? for you Americans). I decided to try slipping her closer to town this time (Kettering where I keep her is 40 mins drive away). So I had to sail her up. With all the weed on the bottom it took much longer than I had planed, and had to motor sail to keep her moving... very sad... It got dark and I learnt that my masthead light wasn't working... Another job to do...

Anyway today she went up and after three hours on the end of a water blaster all the flora and fauna making their unwelcome home on the bottom of my boat were evicted and the bottom was clean (it was pretty bad, kind of glad I don't have a photo...). The reason for such bad fouling, paint detachment - the epoxy paint sealing the old antifouling away is starting to fail badly after 6 years, and much of the 18 year build-up of paint was blistered and loose, with weed growing through any cracks.

So really I think this means a sandblast job to remove the assorted antifouling paint build up on the bottom. Unless any of you have any better ideas... While I am at it I should make all those modifications to the boat underwater that I have planned. I will get around to describing some of these in later posts.

Cheers

Ben

Damage Control

Once upon a time I used to occasionally teach damage control at the Australian Maritime College, it was a fun course (except in winter, when it was cold...). We had an old ship set up with a series of rooms that could be slowly or quickly flooded through various cracks, splits and dodgy pipework, all under the control of a sadistic instructor such as myself... Like I said it was great fun, but I also learnt some bits and pieces from this, most of which I hope I will never have to use for real.

Picture this, a dark night, shall we add stormy? no that would be too dramatic... So a dark night, somewhere maybe a couple of hundred miles offshore, nice sailing, wind vane doing its thing, boat trucking along on a tight reach, and a cuppa hot chocolate keeping the hands toasty warm. You carefully scan the horizon, looking under the headsail, trying to use the edges of your vision, and to be methodical, nothing seen so back under the dodger to get warm again, before the next lookout in a few minutes... Suddenly without warning a loud bang and a shudder as the the vessel rides up something unseen, you curse.... !@#$%^ due to spilt hot chocolate scalding your hand...

Well I guess you know whats going to happen next don't you.. Yep, Sure enough water can be heard trickling from somewhere forward, on the leeward side  Quickly... the boat is sinking!!

Is everyone ok? well then wake up and put something warm on. This could be a long night...Turn on all the bilge pumps, and make sure they are working. Attend to any injury's - put burnt hand in cold water, at least you have a plentiful supply in the bilges. Now start hunting for the leak and grab your damage control kit, we have one of these handy don't we?

Snow Petrel's DC kit (with $1 tipshop bag)

Fortunately we do, our DC kit is conveniently stowed up forward and for our metal boat it includes :

• Instruction sheet with layout of seacocks and reminders and prompts to suit our boat
• Torches- A head torch is good, and a floating torch... well floats.
• Small axe to smash out joinery, and shape wedges then hammer wedges home.
• Softwood wedges and plugs of various shapes and sizes
• A block of soft closed cell foam to initially stem the flow
• Underwater epoxy putty, in small and big sizes, and other suitable goop's
• Quicksetting underwater cement, Ideally in a bag (can be stuffed unto whole to stem water)
• Hoseclamps and screw driver.
• Bicycle Innertube to wrap around leaky pipe
• If hull is foamed, a way to remove foam, like an old chisel.
• A pair of gloves (winter grip gloves are ideal)
• Mask and snorkel 

All these handy items are in a bag that can be carried to where it is needed.

After you have narrowed the leak down to the locker under the forward double berth you quickly clear all the crap out from it - it's amazing how fast you can clear out a locker (but you try to keep it out of the water). You ask for a check on the bilge level... we're losing ! Maybe you should think about a Mayday or Pan Pan - and get those buckets working faster...

The leak is a split on a weld line near a frame, the plating dented, but the frame didn't, tearing the plate in this area, it's not big, but boy the water is spraying in, it's a good job you have that diving mask to put on... Maybe we can heave to on the other tack to lift it abit higher and reduce the outside water pressure, the slower speed will also help and it will be more comfortable...

Quickly you grab a wedge and split it into three smaller wedges with the axe to better fit the curved split. The first two wedges go in quickly and the last is slightly trimmed down to better fit the remaining part of the crack. With the last wedge tapped in the leak is considerably slowed. Phew.... But this no time to rest easy, while that adrenaline is still pumping lets check the rest of the boat, there may be another leak. We notice the pumps start gaining on the water..

It is now under the floorboards and after unlocking them you inspect the bilge and check the strum boxes are clear. We had kept them locked down to stop them floating away, and to reduce the amount of debris reaching the bilge.

After a few minutes you mix some underwater putty and press it around the edges of the swelling wedges, it reduces the flow to a trickle... well done, lets downgrade that mayday and get another cup of hot chocolate and try to calm down those shattered nerves. And a Securitie to alert other vessels of the submerged hazard might be in order..

At no time did the water get near our abandon ship point (with the water somewhere around my knees on Snow Petrel) at this point our efforts would have shifted into getting ready to abandon the vessel.

This situation is hypothetical, and I hope it stays this way. But having a damage control kit gives you plan to deal with a leak, part of it's function is obvious - to put all the gear you might need in a handy place, the other part is not at first so clear. This DC kit and the thought that went into compiling it has given you a plan, and having a plan has prevented panic (or at least controlled it)... Suddenly you know exactly what to do, having the DC kit and a plan gives you a focus that helps to prevent running around in circles shouting and screaming hysterically...

Now I note you can buy some pretty good kits but if you buy one please make sure you have also put the thought into how to use it. Non metal boats need different DC kits to metal boats (you can work out the details), and the old fothering trick with stout tarp has actually worked perfectly for me in flat water, try it on a seacock or when you clean your speed/log paddlewheel if you have one (I don't). I think they are just one more spot to get a leak from.

By the way, The only two times I have had water over the floorboards it turned out to be freshwater from the watertanks. Taste the water before you pump it out.

What do you have in your DC kit, and have you ever needed to use one?

Cheers

Ben

PS - check your memory, what tack was the boat sailing on (on that dark night) before the impact, no cheating by re-reading above... thought about it yet.. well actually I didn't specify a tack but I did have one in my minds eye, I am curious to see if we are port or starboard brained. as part of a world first and highly scientific survey click below on:

(A) for "in my minds eye the boat was on port tack"
(B) for "in my minds eye the boat was on starboard tack"
(C) for "we were running under twin headsails wern't we?"
(D) for "what does port and starboard tack mean?"

And as always you can click on liked to give me a warm fuzzy feeling of accomplishment (and to poke a stick in the eye of all those nasty english teachers who were most unimpressed with my writing)

Fatigue... of the human variety

Watch Bill- 2 on 4 off

I have spent quite a large portion of my life on watch systems of one sort or another, and in general I dislike them all... No matter how clever the watch system is someone still has to be up and alert at 0300, and the human body (at least mine anyway) is just not designed for this kind of abuse... I struggle to keep my eyes open and mind alert, and I know I am along way from my peak efficiency (and it's pretty low even on the rare occasion that it reaches peak..)

I suppose there is one system I do quite like, It's a watch system where someone else always gets the graveyard shift, and I get to sleep. But that's not really very fair is it...

Those graveyard shifts are just bearable if I have had plenty of sleep, and are into the swing of a watchkeeping routine. If I am already sleep deprived and fatigued it is a dangerous combination that I do my best to avoid. I have already talked about Rolf and Deborah's excellent  Sleep bank concept where you make sure you have enough sleep stored up to keep you safe. Go to far into debt and the debt collectors will soon be calling. and then you will pay the price - with interest...

I always remember my father in a sleep deprived state when I was very young. We were sailing up the east coast of NZ and for whatever reason he had been awake to far to long. He couldn't correlate the chart to what he was seeing outside and so took the always reasonable approach and decided the chart was wrong and he had found some new islands... Fortunately Mum still had her marbles, and could navigate us home.

After a decent sleep my old man couldn't believe how stupid he had been (and still denies it..) but the scary thing is, abit like being very drunk, you don't know how impaired you are at the time, and to you your decisions seem rational and smart. Hallucinations are the extreme symptom of sleep deprivation. I have never got to that point, and intend never to (touch wood). But some stories of hallucinations by singlehanded sailors who have mismanaged their sleep are downright scary... Sleep deprivation is probably the root cause of a significant proportion of serious accidents at sea.

If you are alone you need to be particularly careful, to the extent that managing sleep becomes your number one priority. During my singlehanded Tasman crossing in Reiger I was lucky that the cheap alarm clock I had bought from a two dollar store (predictably) died on the second night. So I ended up sleeping at night with no alarms set. and I found that I woke up naturally every time I needed to, if the wind shifted slightly I woke up, If it dropped I woke up, and once I even woke up to see a ship 5 miles away (not on a collision course...) I think the sound of the engine and propeller woke me... It worked for me because I was well rested. If I was sleep deprived my body would not wake up for the slightest sound. I don't think I would recommend this anywhere with more traffic than the Tasman? Around the coast I kept a 20 minute look out with micro sleeps, a punishing routine - that I could only keep up for one night (anybody got any tips on this?). I guess the point here is that I made a decision that mid ocean my biggest risk factor was fatigue due to lack of sleep, rather than being run down...

With crew it is more about making sure everybody is getting enough rest. If crew decide to skip a sleep period because the weather is nice or they are reading a good book it can cause problems latter when they fall asleep on the graveyard shift. This often happens when you first leave port for a big voyage or race, most crew want to be up for the excitement or because they want to be hero's, I normally go for an afternoon nap and they think I am soft. But at 3oclock in the morning I am capable of making sensible decisions and they are struggling to keep awake... Even if I don't actually sleep in my afternoon nap, just lying down and relaxing does alot of good.

I keep away from caffeine when I am on watches. For me It can really effect my sleep patterns, but it is good to have as a backup if I really need to stay awake for 6 hours or so.

I hate the 4 on 8 off watch system, If prefer 2 on 4 off or 3 on 6 off. With only two I quite like 3on three off at night and 6 on 6 off during the day. But it is hard to get much agreement on this... watch systems deserve their own post later.

When sailing through heavy ice getting enough sleep as skipper is a huge problem, on Snow Petrel I should have stepped out of the watch system when we were in the pack ice, and been on call. I got very tired and it could have been dangerous if we had any problems. I drew too heavily from the sleep bank...

As a Skipper you need to look after your own sleep, don't be a hero, It's easy to overwork and overworry and micromanage everything and before you know it you are the one making stupid decisions, or crew take things into their own hands and "let you sleep" for a while, instead of calling you if and when they should. There is alotwatch and give crew a break as a treat... As a skipper it is good to be able to Nana nap, even just for 15 minutes can be refreshing.

On the ships we always write up night orders, with specific instructions for the officer of the watch (OOW), they must be read and signed  (and then followed..). I have used this system on yachts as well. It has many benefits, not in the least being that instructions aren't subject to chinese whispers, and are less likely to be  modified or forgotten at 3am. The night orders apply to that night only and can go in the logbook. The masters standing orders are more generic and can go at the front of the logbook, to be read and signed on joining. Masters standing orders and night orders deserve their own exciting post. But if done properly can help the skipper sleep soundly, knowing his instructions should be understood and that he will be woken when needed.

Finally another Shipping thing from the STCW these are some of the exciting Anti-fatigue rules we must abide by and they are worth considering as a minimum for yachts...

1. All persons who are assigned duty as officer in charge of a watch or as a rating forming part of a watch shall be provided a minimum of 10 hours rest in any 24-hour period.
2. The hours of rest may be divided into no more than two periods, one of which shall be at least 6 hours in length.
3. The requirements for rest periods laid down in paragraph 1 and 2 need not be maintained in the case of an emergency or drill or in other overriding operational conditions.
4. Notwithstanding the provisions of paragraphs 1 and 2, the minimum period of ten hours may be reduced to not less than 6 consecutive hours provided that any such reduction shall not extend beyond two days and not less than 70 (77 under IMO?) hours of rest are provided each seven day period.

If you have any fatigue induced error stories put them below, or any other comments.

Cheers

Ben

Fatigue... of the metal variety

This was the chainplate from an old aluminium open 60 I skippered. This happened before I joined on the voyage back from South Georgia to the Falklands. The boat got badly knocked down and the cap shroud hole in the chainplate pulled out, resulting in the mast getting a rather nasty bend just above the 1st spreader (it was amazing that they didn't loose it!). It took the resourceful Falkland islanders 10 days or so to pull the mast out, straighten it, sleeve the distorted area and re-install it (an amazing job...) While they were at it they welded in a set of massive new chainplates. All done with very basic facilitys. As you can imagine we had our hands full cleaning up the boat and fixing the million and one other broken things from the knockdown.

Also broken was the staysail stay chainplate, you can clearly see another crack underneath the point of failure. This thing was just waiting for an excuse to let go, and it failed before the knockdown... 

A full inspection revealed a crack starting in the stainless steel solent stay fitting (right side, at the top of the weld), This is a common place for failure, right near the heat affected zone, just outside a weld. Once the crack starts it concentrates loads at this point creating a stress riser and accelerating failure, also nasty things like crevice corrosion can start inside the crack, eating further into the metal....

The forestay chainplate wasn't too crash hot either... lets not push her too hard...

The point of all this is not to bag out the boat, just to say that on older boats don't assume that just because things have not broken, doesn't mean to say they won't. Metal fatigue and corrosion can invisibly weaken parts that otherwise look solid. The Open 60 had a complete new rig 7 years before this, but the chainplates were over 20 years old, and possibly slightly underspecified to start with. She had had a hard life, alot of it in Antarctica, (cold may accelerate fatigue - any engineers out there?). Nobody had thought the solid looking welded in chainplates could give any problems....

The most highly loaded parts of any boat are normally the rigging and what they are attached to (and maybe the keel bolts...). Sailors are well aware of the need to replace stainless steel shrouds every 7-10 years or so, but many fail to realise that the rest of the load path is also highly stressed and subject to fatigue. Quite commonly people replace the wire religiously (to keep insurance company's happy..) but never change the highly loaded through mast tang bolts, or the tangs themselves... The tang bolts particularly seem to fail quite often, then dropping both port and starboard shrouds, meaning you can't even tack to stabilise the mast.... Turnbuckles also need replacing every so often, as can the chainplates.

To be really safe I think it makes sense to consider replacing all the components every 2nd rigging change (20 years or so) and very carefully inspect all components at every rigging change. Chainplates should either be massively oversize, or easily replaceable. Be very wary of any stainless that passes through a damp deck, stainless can corrode very quickly in a damp low oxygen environment.

I replaced some U Bolt chainplates as a precaution before a delivery, and was horrified to find two of the ones I removed had lost 90% of the metal due to corrosion, they had looked perfect.... Lucky I had been told to watch out for this by a friend who had one fail on his boat. Stainless is treacherous stuff....

My chainplates are mild steel (with SS edging and inserts) to reduce the problems with fatigue. Mild steel has some pretty forgiving properties, one being that if you keep the stress below a certain point (the endurance limit) it doesn't really fatigue, unlike most other materials which will always get slowly weaker with each load cycle (that year of mechanical engineering was useful after all!). My bottlescrews are also galvanised steel, as is my rigging wire - both come with industrial test certificates and a SWL (unavailable for yachting stuff...). When I next re-rig my boat I will replace my stainless tangs with galvanised mild steel mast fittings as well.

There are some non destructive ways to test for cracks, but they are not 100% and could give you a false sense of security. I normally use a magnifying glass and look carefully, but I really should invest in some dye penetrant and developer, this supposedly highlights any cracks, has anyone used it?

Anyway I guess I have just given you yet another thing to worry about... Thats good if it means you might be less likely to loose your mast. If anyone has had a rigging failure I would be very interested to hear all about it....

Cheers

Ben

Welding stuff for your boat

Chainplates with SS inserts and edging

The of the best boat refitting skills I have is welding, It took me an adult education course and two years at night school classes to get really confident, (I have dreams of building my own metal boat one day..) So far all the pieces I have welded onto Snow Petrel have stayed put... (touch wood - metal?). And some of them are important like the tabernacle, and chainplates. My metalwork is not like the classy shiny stuff that you see coming from a fancy workshop with their TIG welders and polishers, it is more industrial, without the mirror polish and delicate weld beads but still does it's job just fine.

In fact I ended up replacing all Snow Petrel's deck fittings with (much better) welded on homemade stainless steel fittings. Now the only holes in the boat are the windows, hatches and winch bolts. I now have no deck leaks! (an incredible luxury), less rust traps and better designed gear.

My complete kit fits into a small suitcase, (except for the helmet), and can easily live onboard. At the moment I am welding up a little wood heater to replace my smelly diesel heater. I get alot of satisfaction from welding and I really think that If you plan to go to high latitudes a metal boat is a pretty good idea, and if you have a steel boat learning some basic welding skills makes sense. Welding aluminium as a different ball game, much harder, and expensive bigger welders are needed.

My incomplete fireplace door, Special fire glass is needed

It always surprises me that most budget sailors are happy to do their own woodwork, canvas work and rigging but bulk at even the most basic metalwork... If an uncoordinated numpty like me can do it, then most of the budget sailor population should be capable of learning and with some pretty basic skills, and a small amount of equipment some useful gear can be knocked up quickly and permanently from stainless steel. Even If you aren't happy welding you can always save alot of money by cutting out the parts and getting them welded up professionally (or by that mate for a 6 pack or two of beers....). If you take a few pieces of metal into any shop and ask them hust to weld them together it is normally pretty cheap, and they can often do it while you wait. Much of the cost is in designing, cutting and polishing the job.

Some basic tools needed -

A small DC inverter stick welder,  much better than the my old AC welder because it is way smaller lighter and has a much better duty cycle (It can run at 100 amps for 25% of the time, enough for most welding on a yacht), and it will happily run off any crappy power source, even what you might get at the end of an old wharf, or up a mast (I have chucked it over my shoulder and welded at the masthead). Get one that can run off a generator. Or alternately an onboard alternator welder can be used if desperate.

A welding helmet with an auto darkening lens is much easier to use.. also good quality respirator that fits under the helmet is essential to keep the worst of the nasty welding fumes away from your delicate lungs.

Welding Rods: I use 316L for welding SS to SS, 309L for welding SS to mild steel, and 6013 or 6012 rods for mild steel. Keep them very dry, humidity can effect the flux coating. 

A 5 inch angle grinder, I went though a few cheapies until I bought an expensive one. Make sure its a 5 inch with the big stud, taking discs with a 22.2 mm centre hole, not the toy 4 inch ones. I normally don't bother with a 9 inch grinder (even though I have one..) the 5 inch can do almost everything much better and is safer.

A heap of skinny 1mm cutting disks for the 5 inch grinder. (sorry about the mixed units, blame the french or the yanks... ) These things are magic, They cut through SS like its butter and leave a nice clean cut. I also assume they cut though fingers and other body parts just as well so be very careful to secure the work well (Like in a vice), always use the guards, and wear leather gloves and really good quality eye and ear protection... If you can't work out what the fuss about safety gear is, please never go to sea and preferably don't go very far from a well equipped hospital...

The most Important gear.. + Add Earmuffs and suitable clothes.

You will also want a flap disk or two for smoothing off edges, and those ugly lumps of weld, Its really just sandpaper for stainless steel, but it's the easiest way to clean it all up. SS grinding disks are also available, and remove metal faster, but flap disks still needed to finish the job. you can use a polishing wheel if you want, but I normaly use fine flap disks.

Add chipping hammers, wire brushes (SS wire brush For SS only), centre punch, cutting fluid for drilling holes and you are set. Drilling SS is a prick, sharp drill bits, lots of cutting fluid and a slow drill speed with lots of pressure are needed. Ideally a drill press for big holes... It is usually cheaper to take it in to a workshop and get them to drill any large holes rather than trash all your drill bits. A workshop can also cut out stainless steel quickly and easily into complex shapes with a plasma cutter - this can be very useful.

You can use pickling paste to clean up the welds an make them look shiny but it is seriously nasty stuff so I normally don't bother. They can just go very slightly rusty, no big drama if the peice is properly oversized (see here for more info on surface cleaning)

I used to get most of my material from scrap metal yards, but these days it is harder to find it this way, so I am forced to buy it. 304 is fine but get 316 if you can afford it. I have some dodgy stainless on my bow roller. It has a rusted to nice patina that I quite like, and the rust doesn't seem to be to getting any worse. Old rod rigging is awesome as SS edging for any non load bearing application. I collect old stainless steel fittings for parts that can be cut up or modified to make new fittings. 

I am always careful not to rely on stainless unless it is massively overbuilt, It is tricky stuff and can fatigue or fail without much warning. Also when welding and grinding beware of heat build up and sparks. Be very careful about fire risks, I have seen a quite a few burnt out steel hulls, and nearly had a nasty fire inside Snow Petrel, Some ports require a hotwork permit. And it is not allowed on most of the better class marinas or slipways... find somewhere abit more industrial. Oh and also grind well away from anything shiny, white or expensive. grinding dust blows along way and then rusts....

Icing and escape hatches

                     Winch starting to ice up, I leave the winch handles in to stop socket icing up - Ideally a hard cover would be good, to enable instant use. Also in extreme conditions tiller may ice up as happened to Totorore.

The other day I was thinking about Berserk, and it got me thinking about hatches and icing and getting stuck inside a boat.... What got me thinking was that Jarle has finally spoken out
and it makes interesting reading...

So what I was thinking (all this thinking was starting to hurt..) was that in a severe icing condition at sea it seems quite possible that the hatches could get badly iced up. I have always been abit claustrophobic, and the thought of being trapped below decks with a stuck hatch is terrifying.. So I guess it would be smart to have some means of forcing them open and also another escape option, hopefully not also iced up badly and frozen shut...

Sprirt of Sydneys main hatch. Note my boots

 Spirit of Sydney had a main companionway door that opened inwards (into the cabin). This is very unusual in my experience. I have never seen one that opens inwards before on any vessel, and it can be abit of a menace. It is heavy and if it gets loose could do damage to fingers and such. From an engineering perspective it is kind of backwards as well, with the major loads from a wave going entirely onto the closing dogs and hinges and trying to open the door, forcing it off the rubber seal rather than pushing it tighter onto the rubber seal with the loads evenly spread into the rim. But the door is strong enough, it has been well proven over many years and in the worst conditions at sea on this vessel.

Thinking about this strange door in relation to severe icing conditions - It would be much easier to open even if heavy snow and ice had filled the cockpit and blocked the doors. It would also be easy to open with a cockpit full of water, or after any event that meant the cockpit was obstructed (ie a dismasting with a broken piece of boom in the cockpit) - Infact I find it hard to imagine a scenario that would trap a person below with this door. I suppose the whole door frame being distorted might jamb it, but this would jamb any door.

Actually for any offshore sailing getting stuck below decks, or maybe even worse stuck on deck would be pretty dangerous. Rolf and Deborah From Northern Light told me about a main hatch securing rope getting caught in it's V cleat inside the boat locking the hatch shut. They were both on deck and quite a few days away from land - stuck outside with no food, water, shelter or tools (all below decks). Eventually (after long enough for the seriousness of the situation to sink in) the boat rolled heavily and the line freed itself.....Whew!!

Snow Petrel has a backup escape/entry hatches - My lazarette hatch only opens and closes from outside and my main-saloon skylight is always free to be opened from inside even when the dingy is ondeck and covering the forward hatch. But both could still be blocked by severe icing.... Maybe I should add an inwards opening hatch somewhere?

Ice melting fast, and wind dropping.

The only moderate icing I have had was whist at anchor and then the main hatch was protected by the dodger. We had to make sure our ventilators remained somewhat free of ice, but that was all, I think we probably had about a ton of ice onboard at it's peak.... Gerry Clark had some very bad icing on the little 32 foot "Totorore", while heading towards Boyvetoya, deep in the south Atlantic (55 south) in late September. It sounded horrible... It's well worth reading his book, probably the most epic small yacht voyage ever, and it was a voyage that did some very useful scientific work, by getting the first accurate data on seabird populations in the southern ocean and it's islands.

I am interested to know if anybody has experienced severe icing at sea on a yacht, what problems it caused, and how best to minimise it's dangers?

Cheers

Ben