|Topic Review (Newest First)|
|03-27-2007 03:37 AM|
I have read all this material and the research again. A variety of methods will work for different boats and different levels of sea.
The Jordan drogue is designed to cope with a 40' breaking wave, not one that has broken but is breaking on you.
So that is extreme. The claim is that other methods will not work in that circumstance.
(The peak load is greater than the apparent load on a 35 foot boat at anchor in 60 knots without allowing for wave forces although the normal storm load is rather less. The data for anchoring suggests a 3/4 " inch storm rode is required as a minimum.)
Whether one should cater for such waves depends. However since a certain proportion of waves I think 1/100 are twice the size of others , one might consider deploying it when the waves are smaller like 20-30 ' even though only a few will break properly.
In general one would expect to encounter these conditions predominantly in certain areas on ocean passages
While they could occur elsewhere you have to consider whether a coastal cruiser with normal prudence ( ie sufficient to know about drogues and have one) would be out there on a lee shore.
True some eg Berrimilla didn't use anything and survived the southern oceans and the capes with as I recall only 5 knockdowns in about a 35'. They were highly experienced and perhaps lucky.
However with survival conditions occurring in a small but significant proportion of say NZ to Pacific Islands trips, some sea anchor or drogue system is mandatory for NZ boats. Personally in such circumstances I would not care very much if I were driven off course.
Using a drogue stops the big impact of coming to a stop virtually instantaneously from say wave speed of 23 mph when hitting a trough. The force in mass times deceleration would be substantial. Talk about hitting a brick wall. The drogue would appear to help in cutting down the time one was exposed to the accelerating force of the breaking wave and therefore the resultant velocity, as well as its braking effect.
I doubt warps would suffice though there are some accounts that they help reduce the chance of a wave breaking.
I agree that one might be aware of and use a variety of approaches. I would think though, that changing plans before things get too bad (but worse) might be quite a good idea. It may not always be so easy to swap from lying hove to through beam on to downwind if you leave it too late.
As I said our requirements are that you carry a sea anchor or a drogue. End of story else you don't go. Some of those Maritime Safety Authority cookies are more knowledgeable and experienced than I am. Of course we are talking 1000 mile ocean trips to the nearest foreign picnic spot where the weather will change within that time not daysails in a weather window.
|03-26-2007 11:20 PM|
Well said, John. Those with no fear of the sea, no matter their level of experience, are questionable ship mates when it comes to judgement. We have a saying in the merchant marine about mooring lines, the spring line used while docking in particular, "strain it-but don't part it." The same philosophy can be applied to all seamanship, and, in particular, the decision to leave port.
Like drunk Russians, who either cry or laugh, the seaman in extremis will often exhibit one or the other. I prefer the humor, even if it is "gallows."
I also liked the anecdote of Sir Edmund. When you're hove to, and got her buttoned up, you might as well rest. After you've done all you can, there is no sense to worrying it about, you've already done all you can and it's nature's show now. Go to bed and sleep, bad news arrives quick enough without worrying it to you. This is usually about the time someone cuts a fart, and everybody laughs and goes to sleep!
|03-26-2007 07:32 AM|
Preparing for the storm
Some thoughts about heading offshore at
|03-20-2007 12:02 AM|
|sailingdog||Of course one thing that Robert didn't touch on is that multihulls tend not to get swept as badly, as they tend to sit on top of the waves, rather than getting forced through them, since they tend not to have the inertia and weight of tons of ballast preventing them from rising with the wave.|
|03-19-2007 11:53 PM|
|sailaway21||A wry sense of humor is a rare and wonderful thing. Thx, Rob't.|
|03-18-2007 11:46 AM|
Originally Posted by hellosailor
A catamaran or trimaran and a fast fin keel boat share something in common compared to my current boat, a Tartan 34C. They can sail under bare poles fast enough to lose control with enough wind. They also displace less then the same size full keel boat. I think you want to slow them down quite a bit and the Jordan Series Drogue is the safest way to do that while putting the least shock on the boats structure when you are talking about a light boat. Remember the strain on the drogue is a percentage of the boats weight so a light cat will have a smaller strain on the system then a full keel boat of the same length. With my all up displacement I might have a strain of 12,000 on the Jordan Series Drogue and thatís unacceptable to me.
Also I think in terms of staying square to the wave face while running and I want to slow the boat down but not as much as the Jordan Series Drogue would. If you slow down too much you will lose water flow over the rudder when the waves crest passes and at the wave top you have the greatest effect from the wind. I think itís a mistake to be in a part of the cycle with the greatest wind effect and the least available steering force. My plan is to keep enough boat speed to have positive steering at all points in the wave cycle. So I want less drag and more control. I also have a center board which will act like the feathers on an arrow when it is down just a little bit. The publications I looked at including the paper written by Jordan all seem to agree that being rolled while running is connected to losing control and broaching. The speed doesnít scare me as much as the broach does. You can avoid a broach by having enough drag to keep the stern to the seas or slow the boat and steer. I have confidence in my windvane and because a random wave will have the same effect on the boat using either system I will use lines as a drag.
My thinking also includes the fact that seas breaking aboard in the cockpit and cabin area are not a good idea. I think, and this is just an opinion that adding 12,000 pounds to the stern will hold the stern and makes it a target for the seas instead of having just 5,000 pounds which will more easily let the stern rise to the waves. I have had seas sweep the boat and itís not any fun. I want to avoid that in the future.
I sail in the North Atlantic now and if I wanted to travel in the southern oceans I would approach this differently. Pitch poling is a greater risk there because the fetch permits a larger and steeper wave. I also see a connection between boat sizes and being pitch poled. If I wanted to sail under those condition I would select a larger boat then I have now and because the line pull from Jordan Series Drogue as a percentage of displacement decreases as boats get larger I would consider adding one then. The lose of boat control at the wave crest is also a problem that becomes less as the boat gets larger because of the increased inertia a larger boat has. She will keep moving unless she hits something solid.
Lots of variables and permutations make for lot of solutions available to the skipper. Whatever plan you select you need to keep in mind that changing plans after things get really bad is usually a very bad idea. And one limiting factor is that if you didnít bring it you donít have it. So if you think you might want to try a Jordan Series Drogue donít forget to pack one. I already carry lots of heavy line so I am prepared to implement my plan, and my backup plan, and then my fall back plan. And if all else fails I can switch to my ultimate plan.
All the best,
|03-17-2007 10:38 PM|
Originally Posted by sailingdog
|03-17-2007 10:24 PM|
|sailingdog||The other reason is that a Jordan Series Drogue creates resistance that increases at a predictable rate. The greater the force on the drogue, the more cones that become active in resisting the load as the drogue line straightens out.|
|03-17-2007 10:08 PM|
"The only question now is why not just tow lines instead of a drag device."
I'd expect that the Jordan device creates more drag in less space, i.e. you can stow a Jordan device in a lot less space than the amount of lines you would need to tow for the same effect. Lines don't have much drag, compared to cones.
|03-17-2007 07:08 PM|
My boat is a trimaran, and yes, I believe the JSD will prevent the boat from surfing down the face of a wave. I would hesistate to use a trip line, since I've seen some problems where a trip line would foul the drogue, and that is to be avoided at all costs. The attachment points I am using are two heavy chainplates bolted to the sides of the central hull, which are installed for this specific purpose.
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