Design and Use of Drogues

  • 31 Mar 2018 10:25
    Reply # 6009041 on 833331

    The attached photo shows Pete in action repairing the drogue anchor point. He said the caption should read "even the skipper gets sea sick!"

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  • 31 Mar 2018 09:57
    Reply # 6009037 on 833331

    Arne,

    Indeed, there are a variety of stories out there. To compliment what you say,  the wave conditions on that occasion were such that the surge pressure was enough to shear a 1/2 inch stainless steel shackle, anchoring the bridal to the starboard hull. Pete fortunately had a sea anchor at hand (basically a large folding bucket on a long rope), which he fixed to the starboard transom, stabilizing the boat while he repaired the starboard bridal. During THAT process, we got thumped by an excessively large wave coming from port, which lifted the hull  (and rudder) into the air, coming back down with the port bridal caught under the port rudder. Fortunately, an equally large wave followed almost immediately, once again lifting hull and rudder, but this time freeing the bridal from the rudder. By this stage, Pete would have been better wearing a diver's suit, mask and snorkel, while Linda and I observed in relative comfort and awe from the cabin. Had the the port bridal remained caught under the rudder, it would probably have sheared it clean off, but we had good luck....and Pete had a spare rudder.

    I was very happy to go with Pete on my first off shore trip, because I knew he would have several back up systems in place should such an event arise. If he hadn't a spare rudder, he would have built one. I think a lot of it boils down to knowing the boat, what it is capable of, and knowing one's own abilities. All the crew had to do was remain relatively calm and do what the man said.

    Although 1/2 inch 316 stainless shackles are very strong, under fluctuating levels of duress, they can become brittle. This does not bolster my confidence in stainless steel, but it does give me huge respect for the forces that we can encounter. Had the shackle not broken, the bridal would have remained amidships and the rope could not have caught under the rudder. Furthermore, Oryx's windvane system does not require servo pendulums or even trim tabs, and the vanes are well forward of and above the bridal anchor points. So once repaired, nothing could catch, even in those steep and confused seas.

    To conclude, from my perspective based on that particular experience, for the drogue to be safe and effective, everything needs to be strong enough to cope with those forces AND it needs to be set up in such a way that it can't catch on anything once deployed. The main disadvantage of the JSR is the bulk and stowage. During the passage it needs to be sitting ready to be deployed in the event of a big storm, but it is a reassuring sight and makes for a darn good back rest when not in use!



  • 25 Mar 2018 10:29
    Reply # 5996185 on 833331
    Anonymous member (Administrator)
    Roger,  

    On the YouTube clip following the one you point us at, there is another real-life demonstration of the JSD, suspended from a bridle. The launching of the drogue goes well, but we are informed that a few minutes after the camera was shut down, the bridle caught the (servo pendulum?) windvane gear and put it out of action, so the skipper had to steer manually after that.

    This should be a reminder. With the high loads on any type of drogue lines (and bridles), and the wild yawing of the boat, the lines may well decide to catch, bend or rip off vane gears or anything hanging on the transom. Not so fun.

    Arne


  • 24 Mar 2018 22:07
    Reply # 5995841 on 833331

    Hi Arne,

    Here is a clip of the series drogue in action on Oryx. We ran into a short sharp storm off the north east coast of New Zealand late last November.

    As a newcomer to off shore sailing,  I found the drogue to be a very good brake and stabilizer. Apparently it was gusting 50 knots and 21' waves but I suspect the current and tide around the North of New Zealand accentuated wave height and steepness, and possibly even affected wave direction. They came mainly from the stern but we also had several hits from both port and starboard sides. Not for the faint hearted!

    As mentioned in one of the posts, Pete uses the slack moments in the wave trough to haul in a meter or so at a time, and secures it round a robust staghorn cleat fixed to the transom inside the cockpit. It seems to be the sort of job that gets you on your knees!


    https://youtu.be/6WQnnhDfHHE

  • 24 Mar 2018 13:51
    Reply # 5995420 on 5995387
    Arne Kverneland wrote:

    Could someone please explain to me in plain, simple English what makes the Jordan Serial Drogue(?), JSD, so superior over other drogues that it defends its costs, its complex construction and its awkward handling?

    Arne

    It's because when a JSD is deployed, it's inevitably going to be in open waters, with a wind of at least gale force, which is raising seas of at least 4 metres in height.

    Now look at this GIF. You can see that if the wave height is 4 metres, in a gale, or at least 8 metres in a severe gale, you would have to get at least 10 metres below the wave crest with your single drogue to be below the worst of the circular water particle movement. That is difficult to achieve, even with a very heavy weight (and this, I believe, is where the SeaClaw scores a few points, as it acts as a paravane and tries to dive, regardless of weight). 

    So a single drogue is sometimes resisting hard, and sometimes resisting less hard, or not at all, depending on what part of the wave circulation it is in. It is disastrous if the drogue is not providing any resistance to forward motion, because it is at the top of a wave, just at the point where the boat is being hit hard by the breaking crest of another wave. And this is why, with a single drogue, it has to be at a certain distance behind the boat, according to the wave length, and as deep as you can get it.

    So what the JSD does is to average out this pull, if it is long enough to be comparable to the wave length, by putting cones into all the parts of the wave circulation, and thus rendering it unnecessary to set the drogue at a certain distance behind the boat. 

    Now throw in two or more wave trains interacting with each other, and it becomes impossible to keep a single drogue at the right distance behind the boat. This is where the JSD really scores points. 

    Last modified: 24 Mar 2018 14:25 | Anonymous member
  • 24 Mar 2018 12:29
    Reply # 5995387 on 833331
    Anonymous member (Administrator)

    Could someone please explain to me in plain, simple English what makes the Jordan Serial Drogue(?), JSD, so superior over other drogues that it defends its costs, its complex construction and its awkward handling?

    Arne

    Last modified: 24 Mar 2018 12:34 | Anonymous member (Administrator)
  • 24 Mar 2018 00:09
    Reply # 5995113 on 5994574
    Scott Dufour wrote:

    Regarding the multiple-storm robustness of the JSD, John of Morgan's Cloud and Attainable Adventure Cruising has a pretty good backstory explained, and recommendations / developments for beefing them up.  He remains a strong advocate for Mr. Jordan's invention.


    It a pity Morgan's Cloud now only offers their articles on a subscription basis.  Understandable perhaps, and cheap enough. I used to read their articles occasionally when they were relevant to my interests.  They are experienced and knowledgeable sailors. The article sounds like it would be interesting, but I don't want a subscription to his website at the moment.  I already know what you need to do.  Build stronger cones with heavily reinforced tabling around the openings.  If, like me, you have a JSD that you bought from one of these commercial suppliers at considerable cost, only to find the cones pathetically inadequate, you could rebuild them before using it.  If I go offshore again (unlikely) that is what I will do.

    PS:  I have just looked at their free blog, which is perhaps what I had read in the past.  Some interesting notes there about retrieving a JSD, particularly on using the lulls in the troughs to get in a few feet at a time.


    Last modified: 24 Mar 2018 00:26 | Anonymous member
  • 23 Mar 2018 15:48
    Reply # 5994574 on 833331

    Regarding the multiple-storm robustness of the JSD, John of Morgan's Cloud and Attainable Adventure Cruising has a pretty good backstory explained, and recommendations / developments for beefing them up.  He remains a strong advocate for Mr. Jordan's invention.

    Last modified: 23 Mar 2018 15:49 | Anonymous member
  • 21 Mar 2018 16:54
    Reply # 5991140 on 833331

    Thanks David and Graham, this has been enlightening.  I think I may even have a new mantra.  Softly, softly, catchee........  

  • 21 Mar 2018 09:13
    Reply # 5990516 on 833331

    I think that hand-hauled recovery of a full-sized JSD is strictly for the smaller, lighter boats and the younger, stronger crews. Too much risk of injury, when handling heavily loaded lines. 

    I'd use the one or two stoppers method, rolling hitched on the drogue warp, taken to a manual or electric winch, for medium sized drogues.

    But when it comes to drogues for a big, heavy boat, I'd move onto the method generally recommended for the parachute sea anchors.That is: first, a float on a strong 10 metre line made fast at the after end of the drogue, capable of supporting the whole device so that it doesn't sink too far when the boat is stationary; second, a smaller pickup float on a short, light floating line made fast to the larger float. Motor back to pickup float, and recover the drogue backwards, so that there is less resistance as the cones are collapsed.

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