Jordan series Drogue Attachment

[estarzinger]

Originally Posted by ImaginaryNumber

Evans,
Sorry to drift off-topic, but is your interesting and useful website permanently off-line?

Yes, I took it down, for "reasons". Taking it down (mostly) solved the problem I wanted to solve so it is staying down.

Originally Posted by thinwater

The limiting force, however, is not the water hitting the boat, but rather the maximum speed the boat will attain while pulling the JSD. JSD dragt is the intentional the weak point. That is the a part of the beauty of the design, because if it did not give, the boat would have to. . . . .. . . But would the JSD allow the boat to accelerate to that speed? No. .

Actually I think you are underestimating what could happen (in acceleration and speed) in a 'worst case'. . . . for two main reasons.

#1 A lot of series drogues are in the 150' range. The rapidly moving water in a huge 'breaking crests' can be well in excess of 150' (there were measurements from Sydney to Hobart video). So, in fact the whole boat and the whole (or quite a bit of it) series drogue (at its typical length) might all be moving rapidly and the series drogue not providing as much breaking as expected. . . . so in the case longer is better.

#2 The crests can accelerate the boat very rapidly. I would have to look it up, but I seem to remember in like the range of .5 - 2 secs - if there is any slack in the drogue at that moment it can get up to speed before the breaking action takes place. Yes, I know one of the benefits of the series is more consistent action, but if you have ever pulled one in you will certainly realize that the tension comes off it as you go up the back of a wave (you can then pull it in by hand). There is an argument that this makes shorter better . . . so perhaps a trade-uff with the above dynamic.

I have heard argued a third factor . . . That the vessel direction of acceleration in the 'worst case' is not in line with the series, but pitched down. Remember the analogy of 'falling off the top of a shear 45' wave' . . . in which really extreme case the acceleration is almost 90 degrees to the drogue breaking action. Jordan was convinced it did near to happen with the Winston Churchill. And much of the damage to boat in storms like this is in fact from being being slammed down on incompressible water (on the 'lee side of the boat rather than the side being hit by the waves). There is an argument here for acceleration and damage potential which the series (or any) drogue may not address (eg 'falling or slamming damage').

We had a lot of experience with the drogues in 'storms', but I'v only seen video and dont have first hand experience (fortunately) with this sort of worst case scenario. There is (and was) a school of thought (particularly among folks with lost of southern ocean and winter ocean experience) that in a certain type of extreme storm you just have to sail yourself out of there (or die trying) because you are not going to survive pinned in the storm area. . . . . but again, without personal experience I am just throwing this out there as food for thought.

. . . my point was that many of us have a frame of reference for 'mode 1' (severe storm) conditions. It is frightening and incredible when you are actually in it, but we sort of understand what is going on. 'Mode 2 (the boat either 'planing' and/or falling in severe worst case breaking wave situation) is different and I think perhaps few of us can really imagine it.

[kmacdonald]

Good attention to detail Boston.

[coastalexplorer]

Hello. My cold molded (coast 30) vessel is registered as 6,500lbs and fitting J S D chain plates has been my latest diversion from My otherwise restoration project.

I simply looked up Donald J Jordan's design drawing for the chain plates on the internet and used that, unfortunately for the purposes of posting here I have been unable to locate the exact link to the drawing; where it specified 6 off 3/8" diameter flat head(countersunk) Allen socket head screws. While He specified chain plate bars of stainless steel 1/4" X 2-1/4" wide and 18" long. I supose those with a heavier vessel could use 3?8" thick steel?

If you have purchased a pack of cones

Because of the lighter weight of my hull I used 304 stainless 2" wide X 1/4" thick (12'long bar for $36) I increased the length of the chain plates slightly to clear the raked transom.

MR. Jordan's instruction was to fit them as wide apart as possible and as low to the water line as practical. I fitted large pads of yellow cedar on the inside of the hull 5" wide 20" long into which I had cut a 2" wide dado grove to accept a backing bar of the same 304 SS material. ( another purpose for these was as a build up to match the line up to the 1" X 2-1/2" cleat that the builder had made for the attachment of the transom.
thus the after most bolt passes through this.)

I produced the chain plates and backer bar in my own work shop. I borrowed a 1" diameter drill from the local machine shop and predrilled the shackle hole. I then had them turn up SS Ferrels, which were press fitted in and Tig welded on both sides.

Next I made a drill jig out of Black locust hard wood that fitted into the groove in the yellow cedar backing block/cleat The aft end matching the aft end of the backing bar exactly. for indexing laterally against the transom. This drill jig was counter bored & predrilled to accept three wood screws which were used to temporally hold the jig in position for the drilling operation of the hull. BTW,The drill press was dialed in with a dial indicator on a swing boom to guarantee absolutely 90 degrees of square and a fence clamped to the drill Table was used to assure straight line alignment of the bolt holes.

Into the inboard face of the backing bar two countersunk holes were drilled to accept Silicon bronze wood screws to hold the bar in place. The six attachment bolt holes were tapped prior to installation.

In the hind sight of experience this proved to be possibly the wrong procedure. These 6 bolt holes in the backing bar should be drilled 5/16. tapping size. and the drill jig drilled 25/32.

After installing the black locust jig; by screwing it into the grove making sure it is seated tight and correctly it was used to drill the hull.
after removing it the backing bar was installed and retained in position with the silicon bronze wood screws. From the out side of the hull a 3/8" national course tap can be used to tap the holes this makes for better alignment. This suggestion is based on the fact that my assistant and I had to retap these holes by running the tap back through from the out side.

While completing the port side. We ran into a lot of time wasting problems with the 304 stainless steel screws binding and seizing in the treads. This was finally solved by using Loctite product never seize marine grade grease on the threads. As a result of this 'learning curve' We completed the starboard side in a hour. The only thing left to do is to seal for watertight. After which lock nuts will be added to the protruding ends of the screws on the inside of the hull.

Then back to fuel tank installation. So I hope this description gives ideas to anyone else considering JSD chain plate installation. For anyone thinking this description complex: IMHO, Attention to detail saves time in the end.

[kmacdonald]

Some of the chain plate sizing found on the internet, including Jordans, calls a design conservative when there is no safety factor at all used and a yield strength of about 40ksi. It could be as low as 25ksi. Be careful what you read on the internet.

[thinwater]

Originally Posted by estarzinger

Yes, I took it down, for "reasons". Taking it down (mostly) solved the problem I wanted to solve so it is staying down.



Actually I think you are underestimating what could happen (in acceleration and speed) in a 'worst case'. . . . for two main reasons.

#1 A lot of series drogues are in the 150' range. The rapidly moving water in a huge 'breaking crests' can be well in excess of 150' (there were measurements from Sydney to Hobart video). So, in fact the whole boat and the whole (or quite a bit of it) series drogue (at its typical length) might all be moving rapidly and the series drogue not providing as much breaking as expected. . . . so in the case longer is better.

#2 The crests can accelerate the boat very rapidly. I would have to look it up, but I seem to remember in like the range of .5 - 2 secs - if there is any slack in the drogue at that moment it can get up to speed before the breaking action takes place. Yes, I know one of the benefits of the series is more consistent action, but if you have ever pulled one in you will certainly realize that the tension comes off it as you go up the back of a wave (you can then pull it in by hand). There is an argument that this makes shorter better . . . so perhaps a trade-uff with the above dynamic.

I have heard argued a third factor . . . That the vessel direction of acceleration in the 'worst case' is not in line with the series, but pitched down. Remember the analogy of 'falling off the top of a shear 45' wave' . . . in which really extreme case the acceleration is almost 90 degrees to the drogue breaking action. Jordan was convinced it did near to happen with the Winston Churchill. And much of the damage to boat in storms like this is in fact from being being slammed down on incompressible water (on the 'lee side of the boat rather than the side being hit by the waves). There is an argument here for acceleration and damage potential which the series (or any) drogue may not address (eg 'falling or slamming damage').

We had a lot of experience with the drogues in 'storms', but I'v only seen video and dont have first hand experience (fortunately) with this sort of worst case scenario. There is (and was) a school of thought (particularly among folks with lost of southern ocean and winter ocean experience) that in a certain type of extreme storm you just have to sail yourself out of there (or die trying) because you are not going to survive pinned in the storm area. . . . . but again, without personal experience I am just throwing this out there as food for thought.

. . . my point was that many of us have a frame of reference for 'mode 1' (severe storm) conditions. It is frightening and incredible when you are actually in it, but we sort of understand what is going on. 'Mode 2 (the boat either 'planing' and/or falling in severe worst case breaking wave situation) is different and I think perhaps few of us can really imagine it.

I think this is more of a disagreement in grammar than reality. I threw 25 knots out there as a discussion number, but the worst pitch could be worse. I'm inclined to think the JSD will prevent that, however, and the success of the system supports that guess. Actually, it probably suggests that none have been thrown faster than the wave--they have been held a few knots slower than the wave--which is what matters most and is probably desirable. You want to be prevented from reaching wave speed and pulled gently back through it. That is the point. But as you say, accurate reporting can't be expected. Heck no.

As for the drogue being in the same wave, I've always wondered if a little longer would be better. With a high transom, the first 100 feet will barely touch the water. But with a bridle and leader, I think 220' is more realistic. However, the forward motion of the wave will decrease force, not increase it. Less relative velocity = less drag. Thus, this is off the "peak drag" point.

Dropping speed could also be great. But that is moving in part normal to the rode and does not add that much velocity. Additionally, the entire drogue will be forced into a curve as the boat drops, reducing peak force. This is all part of the genius--peak force is self limiting and is based on velocity, not impact. One of his key principles is that the force on the boat must be moderated.

This is correct because of the laws of nature--the JSD drag fits a formula based on the speed it is pulled. Drag ~ V^2. There is very little inertial effect--and I tested this--because the JSD is never in a straight line. The damping caused by the curve offsets the relatively low mass of water held in the cones (the source of inertia). Logically, the cones cannot hold more than a few pounds each, spread over the length of the drogue. This is VERY different from the case of the 20' parachute, which might constrain as much as 200,000 pounds of water (1000x more). Thus a parachute needs a very long, very elastic, very strong (I think these are routinely underspeced, since the working load of nylon is only ~ 8-10% BS) rode, probably at least 3x the strength of the main rode. A very tough thing to design for.

[kmacdonald]

There are some good examples of the JSD use here: Victor Shane's Drag Device Data Base | Using Parachutes, Sea Anchors and Drogues to Cope with Heavy Weather – Over 130 Documented Case Histories

[powsmias]

Originally Posted by kmacdonald

I have never heard of or read about an attachment point failure with a JSD. All failures were chafe or cone failures. This indicates to me that no one has experienced a worst case scenario or at least never lived to tell about it. I don't plan on getting blindsided by a hurricane so don't plan on designing for such an event. I do plan of eliminating chafe as best as possible.
The best and proven way to eliminate chafe is the use of stern mounted chain plates.

Incredible thread here.. bought one last year and picked it up in orlando used. seems i have some work fo do, never even gave the load on the drogue a second thought and would have used the cleats on the stern.. thanx to all

[Cottontop]

Originally Posted by Wallaby

One way might be to size your attachment points for the breaking load of the line to the drogue. The loading on the attachment will depend on how it is set up.

For example on my 36K lb boat, the line is 1" double braid nylon (once used to tether a hot-air balloon)--30K lbs min tensile strength. When I finally get around to completing the install, I will use two trapezoidal 3/8" stainless steel plates, 12" long by 9" high x 3", attached to the hull so the narrow end will project past the transom about 2" (in order to fit shackles) Each plate has 3/8" bolts, to backing plates. The load is in the plane of the attachment plate, so the bolt numbers have to be adequate to resist the shear force. see table 6 http://www.ssina.com/download_a_file/fasteners.pdf
Assuming a 15k lb load, I require a minimum of one square inch of bolt cross section.

Note that in many shear connections, the bolts are not intended to take the shear loads. The bolts provide clamping force, and the friction between the pieces takes the shear. The bolts remain in tension, where they are strong.

[powsmias]

I am in awe of reading about this guy losing a hatch and how it was retrieved.. beyond belief!!!! not to say i doubt it, just in awe.

D/M-10 Monohull, Charter Vessel | Victor Shane's Drag Device Data Base

[xslim]

Hi Evans!

I have aluminum boat and the cleats are quite big with lot of reinforcement under them, so they seem to be the most easy choice of attachment.

How did you dealt with chafe of the bridle when you attached it to the stern cleats?

[estarzinger]

Originally Posted by xslim

How did you dealt with chafe of the bridle when you attached it to the stern cleats?

We really did not have any chafe concerns.

If you are using a bridle, there should not be that much movement of the bridle (and it would be best to be dacron or somewhat lowish stretch material).

One thing I am not sure many people understand is that the rode is going to be streaming back, pretty much parallel to the water, not at a big down angle. The loads on the drogue(s) are high enough to pull even 300' of wet 3/4" line up near the surface.



This is not a great photo but the only one I can find on this computer (beth would have much better and higher rez ones). But it does show two things.

#1 is the red arrow to the drogue line. You can see the line is pretty much straight out.

#2 the yellow arrow, pointing to a spot just under my elbow, it is hard to see in this small photo but that is actually the drogue (a galerider in this case) near enough the surface to see its high vis yellow color. This is interesting because it means that that wave it is in is +200' behind the boat (our drogue lines were 300' long and we had a little left in the bag). Which in turn means two things (a) that wave is pretty damn big (but fortunately not breaking), and (b) there is 200' of unsupported wet 3/4" line being pulled taught by the drogue load.

Part of this would depend on your stern configuration and how close your cleats were to the transom, and what was in the way aft of them. Ours had a pretty clear path. We did occasionally run the rodes (and shore mooring lines) thru large blocks shackles to the transom corners to get an absolutely clear fairlead, but not always.

Note(s):
-This is a single element deployment, but the rode issues are (mostly) the same as with a series.
-In this picture we are not using bridle. I'm not sure way, as we usually did. -This situation was coming in across a continental shelf boundary (steeply shoaling water), in a coastal current against the wind, in a strong gale. We had just been knocked over rather hard by a breaking crest and decided we needed a drogue.
-experience suggests chafe and other rode issues are much more a problem with para anchors than with drogues.

[Dymaxion]

Bolts come in several strength grades, a factor to consider as well. Someone mentioned carriage bolts, for non-snag/appearance. Make sure you verify quality, hex head bolts are marked on top for strength, never seen a rated carriage bolt. Grade 3 bolts may as well be called twist offs, they are that poor, Grade 12 is highest rating. Additional measure is if threads have been cut into the shank or rolled. Rolled is a forging process that adds strength to the bolt. Shop carefully, saving a few bucks on the cheapest part of the kit is foolish.

[mikereed100]

I would hesitate to use your existing cleats. Most production boats, particularly cats, seem to go light on the cleats and their attachments. I am not familiar with cleat placement on the Mayotte, but I assume they are on the outboard sides of the hulls? If so this would create a problem with the bridle chafing on the sterns during use, even if you were to beef them up to take the expected loads. A cleat could certainly be engineered to take the loads of a JSD, but to what advantage? By using a chainplate you can use a shackle for the attachment, thereby eliminating chafe. We use a chainplate as described by Don Jordan, bolted to the aft crossbeam. This is one of the strongest parts of the boat and easily accessible from the cockpit.

[mikereed100]

You can just see the chainplates in this photo to the right of the bitt. The JSD is in the blue bag on the crossbeam. The parachute anchor is in the green bag and it's rode in in the red sailbag next to it. Both the JSD and the parachute bridles are already attached, ready to deploy from the stern. The JSD bridle is cleated to the bitt to keep it out of the water. To deploy we just uncleat it from the bitts and drop the chain overboard. You can see the the 3/4" 3 strand nylon rode is badly hockled from use, giving some indication of the loads involved. We have replaced the bridles with 3/4" dacron double braid. I would have preferred Dyneema, but already had the dacron line lying about.

[alctel]

Hey so I am going to get a JSD from oceanbrake.com

For attachments, I was thinking about bolting on a stainless steel chainplate to my slotted toe rail, through bolting using 3 or 4 slots and having it extend 4 inches past the back of the toe rail/stern and using that as bridle attachment points.

The toe rail is aluminium and through-bolted the whole length of the boat every 6 inches, not glued on. Anyone else done this? Good idea?