Stealth mode - New Generation Ropes

[Seaworthy Lass]

Another big bonus of WSmurdoch’s proposal is that there are no throat issues at all. People constructing a series drogue and using this form of cow hitch are not going to get themselves into serious trouble as they could with cow hitching the two bridle legs onto the leader and making the eye length of the leader too short.

I have just mocked it up. Another bonus is that the bridle legs end up on top of each other, not side by side relative to the leader. The 4 portions of the bridle eyes stack neatly in a 4 x 4 arrangement. This means they are permanently central relative to the apex of the leader, so zero shifting is required as load transfers from one leg to the other.

It helps to mull over it a while, but so far I think it is is looking more and more favourable. I think it is worth setting it up properly with 8 mm loops as I did with the alternatively dressed version of this a few days ago to see what happens when some decent load is applied using our winches.

SWL

[Dockhead]

Originally Posted by Seaworthy Lass

I can’t grasp why the bridle legs need to be interconnected to stop the loose one from pulling on the throat of the leader. As far as I can see at the instance load is equalised before transfer, the only spot the previously loose bridle can be is right next to the other bridle. Maybe I am missing something?

Nick's interlocked loops are the same idea I proposed upthread:

Originally Posted by Dockhead

But there won't be any tearing force, if the bridle leg eyes are looped together. They won't slide apart then.


Downside is you would have to splice all three parts together, and you couldn't take them apart easily. But that's probably not a big deal.


Did you get what I meant? Probably I didn't explain it well:


Two bridle legs -- make one long eye splice, then make the one in the other bridle leg after looping the end through the other eye splice.



Attachment 190771



Then loop the unspliced end of the first drogue section through BOTH eye of the bridle legs, and splice.


Attachment 190772


There would be no tearing force at all, since the bridle legs are joined together.

The purpose of interlocking the two bridle ends is to neutralize any force vector which would pull the leader eye apart. The basic principle is that once interlocked, the bridle legs can't exert any forces on the leader which are different from each other. This is one better than using a spliced loop -- so a spliced loop will prevent any opposing each other forces from being exerted on the leader eye loop, but not on the gasket -- so you will have bridle legs sliding around on that.



I don't think you're visualizing yet how this works. There will be no spreading of the throat of the leader eye loop, and no sliding of the unloaded leg. The interlocked bridles will always be at the apex of leader eye loop so long as there is any force on either bridle leg, because all their forces will be exerted on a single point on the leader eye loop, and in the same direction. Any differential in the direction of the forces between the two bridle legs will be resolved between themselves, via the interlock. An unloaded bridle leg will be captured by eye of the loaded bridle leg, and cannot slide away from the apex of the leader eye loop.



There may be some drawbacks I haven't figured out, but the interlocked loops definitely solve the sliding around problem, and also the throat-tearing problem.

[Seaworthy Lass]

Originally Posted by Dockhead

Nick's interlocked loops are the same idea I proposed upthread:


The purpose of interlocking the two bridle ends is to neutralize any force vector which would pull the leader eye apart. The basic principle is that once interlocked, the bridle legs can't exert any forces on the leader which are different from each other. This is one better than using a spliced loop -- so a spliced loop will prevent any opposing each other forces from being exerted on the leader eye loop, but not on the gasket -- so you will have bridle legs sliding around on that.

I don't think you're visualizing yet how this works. There will be no spreading of the throat of the leader eye loop, and no sliding of the unloaded leg. The interlocked bridles will always be at the apex of leader eye loop so long as there is any force on either bridle leg, because all their forces will be exerted on a single point on the leader eye loop, and in the same direction. Any differential in the direction of the forces between the two bridle legs will be resolved between themselves, via the interlock. An unloaded bridle leg will be captured by eye of the loaded bridle leg, and cannot slide away from the apex of the leader eye loop.

There may be some drawbacks I haven't figured out, but the interlocked loops definitely solve the sliding around problem, and also the throat-tearing problem.

I can see that there is no spreading of the throat of the leader with the interlocking option (the apex can’t slide down the eye of the leader), but the loose leg is still free to slide around and chafe. It may be captured at the apex of the leader, but it is not “locked” there. If we are not going for simple eye splices (with or without a loop connecting them) then I think I would like to see both bridle legs actually locked at the junction point (not just one) so one can’t continually flop around and rub. Maybe all the chafe as load transfers isn’t an issue and the shock load directly on the apex of one of the legs isn’t an issue either. I don’t know, but I am not comfortable with it.

I can see too that there are issues with simple eye splices, with or without a loop between them. They will slide around. That’s why I have kept pursuing a better solution despite wanting to throw in the towel earlier.

I will simulate WSmurdoch’s last suggestion later today under load using 8 mm Acera. It looks promising to me. Dockhead, this is essentially the same as how you are connecting the other sections of the drogue, but the bridle eyes are just put on top of each other and treated as one eye. I have had a more time to think about this option since last night and I still can’t see any big drawbacks. It is the same as the other trial under load, but there I dressed the leader as you would a proper cow hitch. I didn’t consider not doing this .

The bridle eyes with probably swivel around under load and end up side by side (they won’t remain one on top of the other as I thought at first), but unlike the suggestion you and Jedi are proposing, the apex of the bridle eyes will not moving around at all as load transfers as far as I can see.

SWL

[Pete7]

Originally Posted by Seaworthy Lass

I think we need the “best method” of dealing with this junction, taking into account simplicity. Cruisers with not a great deal of experience with UHMWPE may be putting this drogue together, so the less to go wrong with construction, the better.
SWL

Indeed, which is why I am following this thread with all its twists and turns with interest.

I don't think we will need the cost and complexity of a JSD for our future travels. However, having a single drogue which can be used for a variety of purposes including emergency steering will be worth carrying for that just in case moment.

Pete

[Dockhead]

Originally Posted by Seaworthy Lass

I can see that there is no spreading of the throat of the leader with the interlocking option (the apex can’t slide down the eye of the leader), but the loose leg is still free to slide around and chafe. It may be captured at the apex of the leader, but it is not “locked” there.

Well, as long as one bridle leg is under load, then both bridle legs are "locked". Do you see that? One strand of the eye loop of the unloaded bridle leg will be caught between one strand of the loaded bridle leg eye loop, and the leader eye loop.



There will no sliding or flopping unless there is no load on either leg.


It seems very clear to me, that interlocking loops definitively solves at least these two problems. Whether there are other problems with this, I don't know. I was somewhat concerned about the twisting of the eye loops -- the will each make a half-twist. Maybe that's not a big deal. Nick? The bending radius is something like 1:1 but since there are two strands to each eye loop, I guess no strength is lost to that, or is that wrong? The uneven bend around two strands might produce some sharp angle which is bad for UHMWPE -- I don't know. These concerns were why I liked your low friction ring idea -- much better bend radius than any rope-to-rope joint, no chafing possible whatsoever, not even when the system is unloaded.



But if we're going to go rope to rope, I haven't yet heard anything which sounds better than interlocking loops.

[Seaworthy Lass]

Originally Posted by Dockhead

Well, as long as one bridle leg is under load, then both bridle legs are "locked". Do you see that? One strand of the eye loop of the unloaded bridle leg will be caught between one strand of the loaded bridle leg eye loop, and the leader eye loop.

There will no sliding or flopping unless there is no load on either leg.

As far as I can see there is.
The mock up verified that as well (photo below).
One bridle eye when loose is interconnected and locked, but the other one when loose is interconnected, but not locked.

Have I somehow constructed this wrongly? One eye of the bridle is undeniably loose when it is not under load. It may be interconnected so it won’t put any load at the throat of the leader, but it is free to slide around and chafe. There will also be shock loading directly on the apex when load transfers, as it is so loose. This only occurs to one of the two bridle eyes in this arrangement.

[Seaworthy Lass]

Dockhead and Jedi, I am feeling a bit stupid, as I can’t see how both eyes are locked when they are not under load.

I recognise that since both of you are insisting this is occurring I must be missing something here.

SWL

PS Given I just can’t see it, it is best I drop my concerns. I sound like a broken record otherwise .
For now I will pursue WSmurdoch’s latest suggestion.

[Dockhead]

Originally Posted by Seaworthy Lass

As far as I can see there is.
The mock up verified that as well (photo below).
One bridle eye when loose is interconnected and locked, but the other one when loose is interconnected, but not locked.

Have I somehow constructed this wrongly? One eye of the bridle is undeniably loose when it is not under load. It may be interconnected so it won’t put any load at the throat of the leader, but it is free to slide around and chafe. There will also be shock loading directly on the apex when load transfers, as it is so loose. This only occurs to one of the two bridle eyes in this arrangement.

OK, I see what you've got.


Yes, if ZERO load, then the lazy side is free. But with zero load, there is zero chafe. As soon as there is even 1 kgf of load, it will be locked together with the other one in one place -- at the apex of the leader eye loop.


Being loose under ZERO LOAD is common to most of our solutions, and I don't think it's a problem. It's sliding under some kind of load which produces chafe.


I also don't see any special shock load problem here. Every single one of our solutions will have shock load if there is slack in one bridle leg. The method of attachment has zero influence on this shock load. If the end of the bridle leg is somehow fixed, there will still be the same shock load as the slack comes out of the lazy leg.


I don't think this is an issue in any case, as the geometry of the bridle arrangement means that there will have to be a yaw exceeding 22.5 degrees to make one bridle leg go slack. I have seen zero reports of yawing of this degree with a deployed JSD; I think it may not even be possible. And if it were a problem, then no scheme we have examined provides any solution. We would need to rig some kind of snubber, if we thought this was a problem.

[Pete7]

Originally Posted by Seaworthy Lass

As far as I can see there is.
The mock up verified that as well (photo below).
One bridle eye when loose is interconnected and locked, but the other one when loose is interconnected, but not locked.

My immediate thought on this would be to make the two bridle legs out of a different colour rope. Deploying it on a dark night in a storm you really don't want to do it twice.

Pete

[Seaworthy Lass]

Originally Posted by Dockhead

OK, I see what you've got.

Yes, if ZERO load, then the lazy side is free. But with zero load, there is zero chafe. As soon as there is even 1 kgf of load, it will be locked together with the other one in one place -- at the apex of the leader eye loop.

Being loose under ZERO LOAD is common to most of our solutions, and I don't think it's a problem. It's sliding under some kind of load which produces chafe.

I don’t understand the exact dynamics of what will occur when load is transfered from one leg to the other. If the eye taking up load is loose, then maybe there is chafe as load is applied. I don’t know, but I imagine it is not improbable.

I also can’t imagine zero chafe in its floppy state, as the loose leg is moving through water and it may be sliding around.

Originally Posted by Dockhead

I also don't see any special shock load problem here. Every single one of our solutions will have shock load if there is slack in one bridle leg. The method of attachment has zero influence on this shock load. If the end of the bridle leg is somehow fixed, there will still be the same shock load as the slack comes out of the lazy leg.

The difference may be (emphasis on “may”, as I don’t know) that if the apex of the eye is secure, the load does not hit the apex first. Shock load acting on a loose bend first may be worse. I am just tossing out ideas here and I may be completely off base.

Originally Posted by Dockhead

I don't think this is an issue in any case, as the geometry of the bridle arrangement means that there will have to be a yaw exceeding 22.5 degrees to make one bridle leg go slack. I have seen zero reports of yawing of this degree with a deployed JSD; I think it may not even be possible. And if it were a problem, then no scheme we have examined provides any solution. We would need to rig some kind of snubber, if we thought this was a problem.

Isn’t the total angle 22.6°? This would mean the amount of yaw needed to straighten a leg is half that. I can’t find any info anywhere on how much yaw occurs.

Speaking of a snubber, it may be useful to have the retrieval line (which also serves as an emergency steering line and safety line) in nylon. I have mulled a bit over that, but put it on the back burner for now.

SWL

Edited to add: The instant any yaw occurs won’t one leg of the bridle go slack? The rest of the drogue won’t move.

[Steve_C]

This is exactly why I proposed inserting 1 line into the other when making the loops. Neither can shift and it keeps it a nice clean shape around the end of the eye (eyes).

I am now also curious where is the best place to attach the retrieval line? Also in the same Eye of the leader?

[Dockhead]

Originally Posted by Steve_C

This is exactly why I proposed inserting 1 line into the other when making the loops. Neither can shift and it keeps it a nice clean shape around the end of the eye (eyes).
. . .

I think that's clever.

[Dockhead]

Originally Posted by Seaworthy Lass

I don’t understand the exact dynamics of what will occur when load is transfered from one leg to the other. If the eye taking up load is loose, then maybe there is chafe as load is applied. I don’t know, but I imagine it is not improbable.

I think the dynamics are that as long as there is any load on either leg, the leader eye loop will be held out and the legs will be grabbing the leader eye loop at the apex, unless one leg is completely unloaded, in which case that leg will flop around. But when it becomes loaded, it will hook up right in the same place -- at the apex.

Originally Posted by Seaworthy Lass

I also can’t imagine zero chafe in its floppy state, as the loose leg is moving through water and it may be sliding around.

But surely this is trivial in any case? How much "floppy state" is possible, if it even occurs at all? The drogue will turn with the boat to even out the load. The drogue can't work with one leg unloaded for more than a moment.

Originally Posted by Seaworthy Lass

The difference may be (emphasis on “may”, as I don’t know) that if the apex of the eye is secure, the load does not hit the apex first. Shock load acting on a loose bend first may be worse. I am just tossing out ideas here and I may be completely off base.

I'm out of my depth here so can't comment. I don't know. Shock loading -- if a leg goes completely slack and then gets a load, if that's even possible -- will happen whether or not the bridle eye loops are fixed. Is it better if the shock is caught in the apex or a crack of the bridle leg? I dunno. But I kind of doubt that there will be any such shock loads of any significance.

Originally Posted by Seaworthy Lass

Isn’t the total angle 22.6°? This would mean the amount of yaw needed to straighten a leg is half that. I can’t find any info anywhere on how much yaw occurs.

Yes, you're right -- thanks for the correction. But the drogue is not going to keep going in a straight line, as the boat yaws. It will be dragged along and will turn with the boat. I really doubt we will see any kind of slack bridle legs unless the boat is violently spun somehow, but violent spins are exactly what the drogue will prevent. Maybe those with actual experience could comment on the slack bridle leg/shock loads question.[/QUOTE]

Originally Posted by Seaworthy Lass

. . . Edited to add: The instant any yaw occurs won’t one leg of the bridle go slack? The rest of the drogue won’t move.

Why won't the drogue move? It's being pulled along behind the boat, and in tension. As the boat turns, it will bend and form a curve. I would think more or less instantaneously. It has no inertia to keep it going in a straight line -- it has rather anti-inertia, which is its whole point.


My guess is that the bridle legs will be almost always more or less equally loaded. Note that we size the bridle legs at 70% of the total load. If a leg could ever go completely slack, we would have to size at 100%. So either this doesn't happen, or Don made a mistake. I'm betting on the first.

[Dockhead]

P.S. to the above -- note that what the drogue DOES, is not to pull the boat back on a particular course. It will always be exerting force (or drag) in the same direction the boat is traveling. This is important. The bridle legs are not to pull the boat back on course, they are to keep the boat lined up with whatever direction it's traveling in -- in other words, to prevent yawing off the direction of travel -- which is what a broach is after a certain magnitude.

[s/v Jedi]

Just messing with y'all: leader eye splice in red, one continuous line for bridle. no throat loading

I know, when tension is on one leg it doesn't hold up but I got this on the table when making a bridle that has both legs with a static load for lifting our dinghy up in the arch. But I'm back to dull soft shackle and dog bones for lifting harness like every time I make this.

BTW I agree with Steve's setup; did not find a negative yet.

SWL: the throat loading that you worry about is, say 20% of total load. If you allow the apex of a bridle leg to move up to the throat of the leader splice then you could potentially get a 100% sideways pull on the throat, which is why yo want to bridle legs to stay at the apex of the leader eye splice. There are many ways to do it (just a little piece of small stuff tying the three apexes together would work) but I like Steve's method best for anyone who feels it's easy to create and take out these splices. If not, then I like the eye splices of the bridles kept together with the cow hitch from the leader eye splice best :-)