Keeping The Water Out #2

A motor boat negotiates its way around floating logs, British Columbia

When we were formulating our long-term list of places to visit during our cruising life, the Pacific northwest was high on our list. And having spent Christmas and New Year on the shores of British Columbia and Vancouver Island, we can confidently say that as a cruising ground it has now gone well up the list. It has everything we like – magnificent scenery, wonderful wildlife, a fascinating culture and friendly people. And that’s just where we were – as you progress farther North into the more remote areas we’re reliably informed it gets better and better.

So, what is there that’s not so good? Well one thing that astonished me was the amount of timber everywhere, both on the beaches and in the water. Not just small stuff either – huge logs and stumps that could easily do substantial (if not terminal) damage to any decent sized yacht. But clearly there’s a sizeable sailing community in the area, so how do they cope with it? And beyond keeping a really careful look-out, and perhaps avoiding night passages, what else can be done?

Watertight Bulkheads

Watertight bulkheads afford an obvious passive advantage. In the event of a really serious collision in the bow area, such an installation offers (at the very least) the chance that the boat will survive the impact afloat. And for that reason alone they must be worth having in my view. Yet they are hardly ever seen outside purpose built high latitude boats, despite the positive safety element they offer. Why not?

I suspect this is largely down to cost, although this is far less of an issue with a yacht constructed in aluminium or steel. In either of these materials installation of watertight bulkheads (or compartments) is relatively straightforward, as no special materials are required, and it’s generally just a case of welding in plate and stiffening at a suitable station behind the bow. But in GRP (fiberglass) it is more complicated, due the need to laminate in reinforcement and stiffeners on either side of a bulkhead material such as marine ply, which is a much more labour intensive (and therefore costly) operation, and in may ways much more difficult to achieve a total seal. And from looking at many GRP boats it’s clear that there has seldom been any thought put to the installation of such a bulkhead in the first place, making the task even more complicated, and retro fitting nigh on impossible.

A Simple Modification

One possible option with a GRP boat that can be employed is to box in the area under the forward bunk and fill it with expanded foam. This isn’t perfect, as it may only come partially above the waterline, and will also cost a lot in terms of lost stowage space, but it can be, at least, a step in the right direction. Beyond that, though, anything else is going to require major surgery, and much expense.

I’m sure that if we, as customers, demanded watertight bulkheads in new built boats, whatever the material, designers could come up with appropriate solutions and builders would oblige – and charge us accordingly. Maybe most buyers don’t think it will happen to them and, in fairness, I can count the number of boats that I know of that were sunk through collision on the fingers of less than one hand. But equally, most of the experienced sailors I know have had at least one serious collision with a floating object that might, were luck not on their side, have sent their boat to the bottom.

Bitter Experience

It’s certainly happened to me, crashing upwind in a good F6 and rough seas, where we had virtually no chance of seeing anything floating until the very last second. And we didn’t – just an almighty crash that virtually stopped 9 Tonnes of boat and smashed me into the wheel and threw another crewmember into a bulkhead. The seconds it took to lift the floors to check for damage seemed like hours, and we were all badly shaken by the experience. When we hauled the boat later to check for any external damage we found just how lucky we had been, as whatever we had struck made the initial impact less than six inches below the keel root, leaving a good ding and stripping off half of the epoxy coating. A foot higher and it might have been a very different story.

So when we had our Ovni built, there was no question in our minds that we would have a watertight bulkhead. It has certainly brought me peace of mind, especially on those dark nights when I’m off watch, tucked up in my bunk and Pelerin is charging along. At such times I’m sure I can’t be the only one who has fervently hoped that there’s nothing floating out there, lying in wait for us. Let’s hope we never have to put it to the test.

Further Reading

{ 17 comments… add one }

  • Chris February 2, 2011, 3:09 pm

    All it takes is a visit to http://www.containershipping.nl/casualties.html to get a feel for the potential utility of watertight/flotation filled spaces.
    In 1980, we collided end on with a 2m diameter circular concrete culvert section that had rolled from a barge in a navigable channel. It had been left there, the loss unreported. We hit it at six knots. Our fore-deck submerged. Our propeller was lifted from the water. We were both injured by the falls we took when we continued at six knots while the boat dropped instantly to zero. I missed fatally breaking my neck by about nine inches.
    We found no leaks, but when I dived on the boat the next day, I found a band of lead (also) six inches below the keel root that had a perfect figure of concrete aggregate imprinted on it. I repaired the keel in about two hours, once hauled out. It took my back about 25 years to come to rights.
    Our present boat has a collision bulkhead forward, with the black water tank and anchor locker ahead of it. The inner-forestay attaches to it, so should the bow be weakened, there is still some mast support. The scantlings for this bulkhead are three to four times the bulkheads elsewhere. The “knuckle” space below it is foamed. The heavy construction is not so much about impact resistance as it is about water pressure.
    In a second instance I was aboard another vessel (I am not a Jonah) which hit a sub-surface, semi-submerged object in 40m water (bow on and to leeward) with no damage forward, but the boat was “can-openered” down the aluminum port side by projections on the object.
    Our present boat carries the heavy submerged-hull layup well above the waterline to help protect against this. Again there is a scantling trade off of weight (performance and speed) vs the likelihood of an unfortunate event.
    There is no perfect answer.

    Reply
  • David Stanwood February 3, 2011, 9:33 am

    …perhaps avoiding night passages…

    I’m from New England and we sail at night a lot and it’s a joy. Once in a GREAT while we’ll see dangerous floating objects during the day. Hitting one would have the same odds as being struck by lightening.
    I hear that Yacht Insurance in the NW doesn’t cover night sailing… I can see why.

    Reply
    • Tim Dunn January 22, 2014, 5:21 am

      You don’t see logs in the inland waters of the Northwest, because they lie parallel to the waves, be they ever so small, and become invisible. And yes, logs are everywhere, especially in the Straits of Georgia.

      Reply
  • Jean-François Eeman February 3, 2011, 10:13 am

    Hey!
    As Chris says, there is no perfect answer…

    One thing: when sailing long days, even when somebody is “on watch” the possibility that you hit something is not excluded. A few minutes inattention are enough…

    With our previous boat, on our passage to South America we hit a whale and a container…
    So for the next boat we wanted apart from a watertight bulkhead, a reinforced forefoot and hull shapes without any edge; a fluent underwater line so everything you hit slides under your hull… same thing when you hit a rock you “climb upon” it…

    For the same reasons, we did not want twin rudders. I believe (and have experienced on a MINI 6.50) that it is very often the windward rudder which, when heeling, is horizontal and will hit floating objects…

    Once in a while you hear of people losing their rudder or damaging it, once in a while they sink following to that (remember ARC 2009 or 2008). On an alloy boat where, as Collin correctly states, it is quite easy to do so, I like the idea of having a watertight bulkhead in front of the rudder shaft. That is now standard on all Boréals.

    Reply
  • Chris A. February 3, 2011, 4:31 pm

    Except for the occasional charter all of our sailing has been between The Sea of Cortez and the Juneau/Sitka area in southeast AK. I don’t have nearly as many sea miles as a lot of people on this forum but it is hard for me to imagine a cruising ground that I would rather be in than SE Alaska. Going north through BC into AK things just get bigger, taller and more remote. The outside trip down Chichagof and Prince of Wales Island offers more anchorages than can be explored in a season. The outside areas are far less used than the inside and you can go days without seeing another boat much less sharing an anchorage.

    Floating deadheads are a part of sailing here though. The problem is that they are often waterlogged to the point that a very large multiple ton cedar log may barely break the surface even when the water is glassy smooth. Add even a little bit of chop and they are essentially invisible even with a good lookout. We have hit logs before but not with the force others have described here, fortunately.

    There is no perfect way to avoid this potential. A good lookout is the best active defense. I don’t have it but have read that forward scan sonar is no help. We have a crash bulkhead aft of the chain locker and a watertight door and bulkhead aft of the forward cabin. We also have a watertight bulkhead aft. These seem like the best passive defense.

    Anybody with other ideas chime in. We are heading back to AK this spring.

    Chris A.

    Reply
  • Ben February 4, 2011, 12:18 am

    Hi

    I have hit a whale, while surfing at 15-20 knots on a plywood Spencer 45 mid-Tasman. Luckily for us it must have missed the keel and rudder because otherwise they would have been badly damaged for sure (probably ripped off). I don’t know why these light racing boats don’t have a couple of cubic meters of foam stashed in the hulls to provide full positive flotation? This has to be the ultimate defense.

    Have also had a whale circle and then charge a 28 footer I was helping deliver to Tonga. The whale chickened out at the last moment, missing the stern by millimeters. Very scary, but I guess us humans deserve this and much more from the whales.

    For the trip to Antarctica I made all 3 plywood bulkheads under the fwd double bunk watertight. The tops are still open and are just above the waterline. I’m not sure how effective they would be, but at least they would give us a fighting chance with a small rupture, and they can be filled with water to lift the stern and access the prop and rudder.

    I appreciate Brent Swain’s concept that a welded in WT bulkhead can be a rupture point in a metal hull, which otherwise would dent. He doesn’t like strong ring frames for the same reason, preferring only stringers on plywood bulkheads. My observations of damaged metal boats supports this logic.

    The 5 Wt bulkheads on the Open 60 I ran all had lots of wiring holes through them that were poorly sealed. I didn’t have complete confidence in their ability to stop flooding (except the very fwd two). And I agree that twin rudders are a complete pain in the backside, especially in ice, weed or if run aground. By the way, I love the Boreals, must buy a lotto ticket…

    Cheers

    Ben

    Reply
    • John February 4, 2011, 9:53 am

      Hi Ben,

      Really interesting point on the hard spot from a ring frame or water tight bulkhead causing a hard spot in an aluminum boat that could actually lead to failure. I had never thought of that.

      One of the things I have always loved about aluminum is how ductile it is. In the 20 years I have owned “Morgan’s Cloud” I have twice hit an object–once a growler (baby ice berg) and the second time a steel dock–so hard that I am convinced that a non-metal boat would have been holed.

      In the first case it was on the massively reinforced stem and no damage was done. In the second the blow was abeam on a flat piece of plate (the most vulnerable place) and a large dent was left, but no hole; we just filled the dent with epoxy putty and painted over it.

      Having said all that, I think that if I were building an aluminum boat from scratch I would specify watertight bulkheads.

      Reply
  • Chris February 4, 2011, 10:47 am

    Pure Aluminum is #6 in ductility. It can be alloyed to greater and lesser ductilities. Welding is an issue. Properly welded for the purpose intended, aluminum properly designed ring frames (with load spreading webs, etc) should not be an issue.

    Improperly welded, any aluminum weldment will fail (crack or tear) along a temper line some distance from the weld depending on the heat and gas used and the nature of the insult. Under-performing welding equipment is the worst because the weld can look good, over-performers tend to burn the work-site.

    “Proper” is the operative word. I ran an aircraft maintenance operation in the mid ’70s and discovered proper aluminum welding is an art and requires an artisan (or a properly functioning computer). My best aluminum welders were all in their thirties. I had 18 year olds who could do as well on steel.

    If an inexperienced amateur plans to weld an aluminum boat, some thought should be given to less weld dependent scantlings and shear resistant/shear absorbing metal-metal adhesives (as used in aircraft and rockets).

    Also a comment on foaming. While rigid closed cell urethane foamers are attractive (refrigerator foam, insulation foam), they are also problematic. Once in place this stuff is an utter (and toxic) trial to remove. Since buoyancy is what’s desired, I personally would spray a thin (2-5 cm) layer on the inside of the hull, fill most of the remaining space with silicone sealant stabilized blocks of closed cell urethane and then foam over the top layer.

    Also remember never put solid foam in a space authorities would otherwise consider ripe for smuggling. You don’t want to have to weld the hull back together when they are done. Foamed in contraband has been done and is on the list of “look fors.”

    Reply
  • Colin Speedie February 4, 2011, 11:20 am

    Some great ideas and real food for thought in all of these comments.

    I can see the point about hard spots in metal boats. But (like John) I have a lot of faith in the ductile nature of aluminium, and would certainly rather have a watertight bulkhead than not, especially after hearing of others’ experiences with collisions here!

    On our boat, the stem is well reinforced, and we have a crash type bulkhead backing the anchor locker, and the watertight bulkhead is just behind that. It’s all been properly installed, and I’d be confident that it would act as a crumple zone before rupturing – anything more and I think we’d be looking to get off anyway. And I certainly picked up on Chris’s point about water pressure, and think that that may be one of the reasons watertight bulkheads aren’t seen more often in GRP boats.

    And the more I hear about twin rudders, the less I like the idea of them.

    Best wishes

    Colin

    Reply
  • Matt Marsh February 5, 2011, 5:31 pm

    Re. water pressure: Yes, it’s one of the factors considered in specifying the scantlings of a watertight bulkhead, but it’s a pretty easy issue to work around on the size of boat most of us would be interested in. Certainly not an excuse for omitting the bulkheads.

    Re. hard spots at bulkheads: Shallow-water jet boats (Duckworths, etc) often use longitudinal framing with the bulkheads set back from the skin, for exactly this reason. But they’re meant to skid off rocks all the time at 30 knots, and they’re pretty light. In a displacement hull, the speeds are slower but (because of the weight) the momentum’s greater, and impacts are more of a “wham-stop” than a “skid over it”. My preference here is the same as Colin’s (strong plating, with watertight bulkheads going right to the skin).

    I would say the main reasons why builders sometimes omit proper watertight bulkheads are:
    – Breaks up the layout too much (ring frames leave big open spaces that look good in magazine photos)
    – Costs too much (a WT bulkhead requires quality workmanship to be hidden away where it can’t be seen, thus the value isn’t visually obvious).

    Personally, my preference is for at least three watertight compartments (more = better), even in the smallest open runabouts. At a minimum, the forepeak should be isolated from the fore cabin, the engine room should be isolated from everything else, and (ideally) the lazarette and steering gear should be isolated from the cabin.

    One other thing I just have to mention is the issue of grounding / impact loads. The minimum design conditions for the keel (indeed, for everything below the waterline) should include an impact with a fixed, submerged object while travelling at top cruising speed. I hear far too many stories about “tearing the hull like a can opener” or “keel bolts ripped out of the bottom” for me to consider neglecting worst-case impact loads an acceptable practice.

    Reply
    • Colin Speedie February 8, 2011, 1:49 pm

      Hi Matt

      I agree with your analysis of the reasons builders don’t want to install watertight bulkheads, and maybe that says as much about customers as builders.

      And I’d absolutely agree about the need for minimum impact considerations – this came up very recently in the UK when a charter yacht hit a rock, lost her keel as a result and was sailed back to base! Much debate since about the whys and wherefores…

      Best wishes

      Colin

      Reply
  • Ben February 6, 2011, 8:25 am

    Hi everyone,

    If I was building from scratch I would like to see WT bulkheads scattered thoughout the boat, but I would give some thought to spreading out the point loads from the bulkheads, either by adding doublers or thicker plate in the area, adding tapered longitudinals or some other cunning engineering solution (maybe a ringframe just ahead of the WT b/h).

    I would want to have additional longitudinal divisions rather than athwartships in the fwd region, ie a centerline divider with a cabin to port and stb.

    Also I would like stability and trim info for all flooded conditions, ie how much freeboard is left fwd if the fwd section is flooded, and can I also flood the afterpeak to compensate for the bow down trim? Where will she float with the midships section bilged, and will she have enough stability?

    Also regular testing of WT doors, the more complex pumping systems and WT integrity of the B/H would be needed.

    Maybe those high capacity engine driven pumps would be worthwhile.

    To put in perspective, Spirit of Sydney is an ex BOC Open 60, lightly plated in 4 mm alloy. She got caught in heavy pack ice near Commonweath Bay, and got absolutely trashed, but the only hole was right fwd at the stem where it was only welded on the outside (or so I believe). I had a look at the horrific dents, sold my Fibreglass boat and bought a steel one. The collision B/H stopped the leak fwd being a problem and she was sailed home 1500 nm across the Southern Ocean, with the tips of both rudders missing (breakaway sections) and the prop mangled. Well done crew, boat, and metal construction.

    Cheers

    Ben

    Reply
    • Colin Speedie February 8, 2011, 2:03 pm

      Hi Ben

      Just a note about my earlier comment on our watertight bulkhead and hard spots – ours is actually a standard ring frame that has been ‘filled in’ by plating over, so is part of the original designed structure. And in common with many other metal boats, she has much of the internal hull below the waterline ‘double-skinned’ via tanks, so meets some of your points.

      Take your point about stability and trim in a flooded state – a British builder sold a couple of supposedly unsinkable designs in the 70’s and 80’s using an inner moulding and outer moulding (the hull) with foam injected into the void between the two. Photos of one of the boats in a flooded state suggested to me that whilst they might be unsinkable, they’d be untenable except in a swimming pool.

      Those engine driven pumps are the business, there was one fitted on a big wooden charter boat I used to skipper, and it could really shift tonnes of water – which was just as well, as she leaked like a basket. I wish they were available in more compact versions to fit the average yacht’s engine compartment, as I believe they really could be a lifesaver in the case of a big leak.

      Terrific story about Spirit of Sydney – what an achievement by the crew, and, as you say, metal construction!

      Kind regards

      Colin

      Reply
  • Paul Mills February 8, 2011, 10:07 am

    I have enjoyed following this thread, and the point about watertight bulkheads creating a ‘hard point’ has been thought provoking.

    On my Ovni 395 we have the anchor locker bulkhead that forms the rear of the reinforced bow; we then have a strong full width deck locker that is about 1 meter deep from the deck. Behind this there are no more water tight bulkheads, and the strength is mainly in the combination of varying plate thickness, ribs and stringers.

    One feature that I really, really like is the ‘kick up’ center plate and rudder, with the remaining upper part of the rudder protected by a skeg continuous with the hull under the prop … so no vulnerable lower appendages for big logs, ice or containers to get stuck on!

    Reply
  • Ben February 9, 2011, 8:16 pm

    Re Engine driven pumps, these look like a good and simple solution http://www.yachtwork.com/product-bilge . But clogging would still be an issue, and the only two times I have really needed a bilge pump they clogged. Buckets to the rescue… maybe a really good big strum box is needed. I must say I really do like WT bulkheads, I just wanted to point out that they are not always the perfect solution, and on smaller boats like Snow Petrel they are probably not worth retrofitting, unless as part of a complete rebuild.

    A good damage control bag is pretty good insurance, mine has lots of fine softwood wedges, a small axe, goops, bungs, underwater plumbing epoxy, hose clamps, rubber tube, and a fothering blanket (+underwater torch, gloves, mask and snorkel).

    Also bilge alarms are important, especially with WT B/Heads. test them regularly. I don’t like those auto bilge pumps, lost half our freshwater once, pumped slowly over the side…

    Cheers

    Ben

    Reply
  • Tom February 25, 2011, 11:31 pm

    Lots of great answers of how to prepare a boat for a collision. But, back to your original question of, “How does the PNW sailing community cope with all the logs?”

    It’s not as bad as it seems. The first thing to note is that there is a cycle: it is much worse in the winter and spring (when you were here) because that’s when the big runoffs happen, bringing down the stumps and trash from all the logged over forests. It is also worse during a spring tide when the high tides lift the logs off the beaches.

    Finally, the logs tend to collect in big windrows, where the tides converge. There’s no way of knowing where these will be (although some areas are legendary), but if you see one log, you’ll probably see dozens.

    In summary, logs are a hazard (particularly vertical “deadheads”), but if you watch for their patterns in time and space they’re not too bad.

    Cheers.

    Reply
  • Douglas Pohl April 13, 2013, 3:56 pm

    All boat construction materials have trade-offs. If I was building a new boat it would be a metal boat. Most likely steel; lower initial cost, high strength, and a long service life. The past years I’ve been visiting a Gulf Coast DIY boatyard and seen over a hundred boats stop in for a “shave and a haircut” after traveling the Great Loop around the eastern USA only to discover at haul-out they have ‘blister’ osmosis problems at various stages from just starting to severe ‘pock-marked’ bottoms. What many of these boats had in common was spending a cold winter in northern latitudes after coming from warmer southern waters before arriving back into the warm and humid Southern Gulf Coast. Did a dramatic change of climate force the osmosis symptoms to outwardly appear? I think so – owners reported never knowing of the problem when they bought the boat recently or several years ago (many of the boats were 10-20 years old). Did the marine surveyor check the fiberglass hull moisture content? Most didn’t know that was possible. So they didn’t even ask the surveyor about it. Hence, fiberglass would not be on my short list of boat building materials – it is inherently a less beneficial selection when compared to steel: costs more thanks to rising oil prices, less unit strength and likely requires more lifetime expense to properly maintain. Here is an informative website regarding fiberglass
    ‘blister’ repairs for those wishing to learn more about fiberglass osmosis problems (http://boatpeeling.com/BP/About_Phil.html).

    Buy a steel boat – what the heck you say – when I came across one for sale in the UK – a Dutch built Bruce Robert’s designed Voyager 432 for a asking £24000 (about US$37000) with Perkins Sabre M92B 86hp & PRM gear fitted it was a ‘no-brainer’. Guess I don’t need to say much more – run, don’t walk, if you would like a great project steel sailboat. (http://www.bruceroberts.com/public/HTML/BOATS-FOR-SALE.htm)

    Happy shopping!
    Doug

    BTW – please remember to insulate it well – steel boats tend to rust from poor coatings on the inside. So much to know, so little time. This forum is invaluable to your boating knowledge.

    Reply

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