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 Post subject: Series Drogue Attachment
PostPosted: Sun May 10, 2015 3:23 am 
I'm in the process of building a series drogue for use with my soon-to-arrive Amazon II 550 Expedition Quattro and am considering various attachment options.

The intended use will be with the boat fully loaded for 1-2+ week trips, including long coastal offshore stretches (presume max load on the attachment of around 450kg, even if I never will approach that in practice).

Due to the construction of a folding kayak, it's challenging to find a pair of attachment points, one on each side, for the drogue bridle, which needs to attach to each side of the boat near the stern. I wouldn't trust the stern handle loop to serve as a suitable attachment point, nor the combing, either of which would be the obvious choices. Those are fine for relatively fair weather conditions but not for when the [naughty word] hits the proverbial fan.

Presuming that the boat is strongest under compression longitudinally, the best approach that I can think of so far is to add a polyester webbing strap (such as used as roll-up anchor rodes popular in Europe) around the circumference of the hull, firmly attached to the bow just below the hull/deck seam (e.g. monel pop rivets with an aluminum backing strip inside the skin, running around the bow piece), with D-rings affixed approx. 3/5 back towards the stern, and some strap guides to keep it in position, but not preventing lateral movement under load. This would put all the load on the frame longitudinally along the majority of the boat without stressing the hull or any particular point in the frame, and allowing the webbing strap to stretch slightly under load.

The D-ring placement would also facilitate easy attachment and retrieval/removal, being approx. where the rear seating position is.

Here's a mockup showing webbing strap in white and rivets, D-ring and guides in red.

Image

Thoughts?


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PostPosted: Sun May 10, 2015 7:07 am 
lord high faltbotmeister

Joined: Thu Sep 06, 2007 8:05 am
Posts: 824
Location: atlanta, georgia
Interesting idea, and I am not sure I understand the whole setup so my comments may be a bit naive...

I would be very reluctant to compromise the integrity of the hull with pop rivets, even with a suitable backing, that is just an invitation to problems down the road.

Not sure how you calculated the 450kg force at the attachment point, that seems pretty extreme, are there tables for this from the manufacturer of the drogue? And the configurations I have seen usually use 2 attachments, bow and stern. I have never seen the Wayland carrying handles but I would not hesitate to rely on those (not the handles themselves but, rather, the metal loops) to attach the drogue to my Klepper quattro. Deployment and recovery...that would take some thinking.

And lastly, I would stay out of the typhoon conditions you anticipate :D

_________________
"There is nothing--absolutely nothing--half so much worth doing as simply messing around in boats"

1990 A1 Expedition
2010 carbon Klepper Quattro
BSD sail rig, 24' mizzen + 36' main
36' jib
Torqeedo outboard
1938 Sachs-Fichtel seitenbordmotor


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PostPosted: Sun May 10, 2015 9:23 am 
gbellware wrote:
Interesting idea, and I am not sure I understand the whole setup so my comments may be a bit naive...

I would be very reluctant to compromise the integrity of the hull with pop rivets, even with a suitable backing, that is just an invitation to problems down the road.


I have my reservations about that myself. An alternative I am also considering is to install grommets in the webbing on each side, about an inch or so from the bow, and actually insert a through bolt, with rubber washers, all the way through the webbing, hull, and wooden bow piece. This would firmly attach the webbing to the frame, eliminate risk of any stress on the hull, and prevent any ingress of water.

It would also permit the webbing strap to be removable, when not needed.

Quote:

Not sure how you calculated the 450kg force at the attachment point, that seems pretty extreme, are there tables for this from the manufacturer of the drogue?



The kayak carrying capacity is 400kg and the kayak itself 50kg so I take that as a maximum sustained load (of course, that doesn't take into consideration shock load, so any specific point of failure (loop, d-ring, shackle, etc.) would have to be rated several times that).

The polyester webbing I'm looking to use has a 2000kg breaking capacity.

That said, given the shape/hydrodynamics of the hull, it's highly unlikely that the actual load, sustained or shock, with the drogue keeping the boat stern to the weather and waves, would ever reach, or even approach that 450kg. A sea anchor would be a different story.

Still, equipment such as this should be designed for worst case scenario ++.

Quote:
And the configurations I have seen usually use 2 attachments, bow and stern. I have never seen the Wayland carrying handles but I would not hesitate to rely on those (not the handles themselves but, rather, the metal loops) to attach the drogue to my Klepper quattro. Deployment and recovery...that would take some thinking.

And lastly, I would stay out of the typhoon conditions you anticipate :D


I would also use the drogue if needing to reach shore through breakers, e.g. avoiding the worst of an approaching typhoon ;-)


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PostPosted: Sun May 10, 2015 10:16 am 
Brotherhood of the Golden Paddle
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Location: Arlington, VA (i.e. Wash DC)
I agree with your weight calculation (since it is simply the specs), although the potential peak-load are (of course) far higher, and I think that your general approach is right on-target. However, I agree with g that you should avoid rivets and other hard or metallic fastenings. I think the best method for attachment will be glue. Gluing something along that long an area will distribute the load and hopefully will create the strength of bond you require. I note that all of the attachment points for the sail rigs-- including the stayed ones-- are through patches glued to the hull. The exception is the stayed rig on my Passat, where the side-stays are built into the coaming (the bow stay is still on the hull). The frame and coaming are massive, on the Passat, presumably to take exactly these enormous loads.

My other thought is that perhaps an Aerius 20 or T12 frame would work better, since your perimeter-attachment would lay over the sponsons on an A-2 design (I believe the Amazon is an A-2 knockoff, right?). Maybe you could have long strips of webbing along the hull and deck just above and below the gunwales (i.e. avoiding pressure on the sponsons)-- this would mean that there were four attachment points, which would also further distribute the loads.

_________________
Chris T.
~'91 Klepper A2 w/ BSD schooner rig.
'64 Klepper Passat/Tradewind and T12 restoration projects.
Non-folding: Early '90s Old Town Canoe.
Previously owned '04 Pakboat Puffin II and '05 Swift (prototype), as well as an '84 Hobie 16.


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PostPosted: Sun May 10, 2015 10:21 am 
Brotherhood of the Golden Paddle
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Location: Arlington, VA (i.e. Wash DC)
Since you are waiting for the boat to be built, it seems to me that the best approach would be to consult with Wayland and have the attachment point added during manufacture.

_________________
Chris T.
~'91 Klepper A2 w/ BSD schooner rig.
'64 Klepper Passat/Tradewind and T12 restoration projects.
Non-folding: Early '90s Old Town Canoe.
Previously owned '04 Pakboat Puffin II and '05 Swift (prototype), as well as an '84 Hobie 16.


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PostPosted: Sun May 10, 2015 10:52 am 
chrstjrn wrote:
I agree with your weight calculation (since it is simply the specs), although the potential peak-load are (of course) far higher, and I think that your general approach is right on-target. However, I agree with g that you should avoid rivets and other hard or metallic fastenings. I think the best method for attachment will be glue. Gluing something along that long an area will distribute the load and hopefully will create the strength of bond you require. I note that all of the attachment points for the sail rigs-- including the stayed ones-- are through patches glued to the hull. The exception is the stayed rig on my Passat, where the side-stays are built into the coaming (the bow stay is still on the hull). The frame and coaming are massive, on the Passat, presumably to take exactly these enormous loads.

My other thought is that perhaps an Aerius 20 or T12 frame would work better, since your perimeter-attachment would lay over the sponsons on an A-2 design (I believe the Amazon is an A-2 knockoff, right?). Maybe you could have long strips of webbing along the hull and deck just above and below the gunwales (i.e. avoiding pressure on the sponsons)-- this would mean that there were four attachment points, which would also further distribute the loads.


I did think about bringing the strap over the top deck, even utilizing the existing deckline loops in some fashion. Your point about stress on the sponsons is certainly something to think about. The question is how the load would be distributed across the frame with that configuration.

I don't think, though, that I'd want the straps glued along the entire hull, as that would put stress on the hull itself and could even overstress the hull/deck seam (as the webbing will stretch a little under load).


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PostPosted: Sun May 10, 2015 11:05 am 
chrstjrn wrote:
Since you are waiting for the boat to be built, it seems to me that the best approach would be to consult with Wayland and have the attachment point added during manufacture.


The boat is essentially done and about to be shipped. In any case, this is the sort of thing I'd rather do myself, and know how it's done, and done right, etc. The process for working out a custom feature design and getting it done as expected by the factory would probably result in insanity; both mine and the factory's ;-)


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PostPosted: Sun May 10, 2015 11:39 pm 
Brotherhood of the Golden Paddle

Joined: Sun Aug 16, 2009 10:05 pm
Posts: 1398
Location: South Salem, NY
I understand your weight calculations but I personally think you're a little off the mark with the effective load you'll be dealing with. Yes, the boat can max out at 450 KG or 900#, but hey, you're not dropping the thing off a cliff and expecting the canvas or rubber to hold the dead weight in a fall, you're talking about using a drogue or sea anchor. Either of these anchors move, that's the idea, to help stabilize your boat in rough seas.

I have not used a drogue or sea anchor with the kayak but I have used a sea anchor for fishing on a 23' center console and it's not that big a deal. I recently acquired a sea anchor for my kayak and I hope to play with it this summer, but I have often heard that an effective drogue for a kayak is simply a line dragged from the boat. I'm not sure about the length but I would probably start with 50'-100' or 15-30 meters and see what happens. Got any pictures or links to the drogue you have?

I think a couple really solid D rings sewn into the canvas both bow and stern (so four rings) would allow you to set up matching anchor trolleys on either side of the boat. Overkill I think, but do-able. With an anchor trolly you can deploy and retrieve from the comfort of the cockpit without any crazy gymnastics (to be avoided in rough seas). Attach the drogue and trolly it to the bow or the stern depending on conditions and usage. I would recommend just using one side and have the other standing by as backup or safety line.

I have a 150' anchor line that I run on a trolly for my Aerius II and although I have never used it in rough seas I have great confidence in it. I use the same bow and stern connectors that Greg referred to on his boat. They are plenty strong for this operation and I wouldn't have any issue with attaching my sea anchor to this rig.

Be cautious that the drogue or sea anchor that is not too big for your boat. Too powerful an anchor will cause a whiplash affect and that will cause damage. Also, I don't believe there is a fixed length for something like this, it always needs to be matched with the seas... so adjustment is necessary and having a cleat or something back at the cockpit running through the trolly makes this easy. The whole idea of the drogue is to smooth the movement through crashing waves or surf - that means everything moves and balances together. I don't think you should ever have anything (other than an anchor with plenty of scope) trying to hold a fully loaded expedition boat in place.

Speaking of adjustment, you'll want to be able to drop the thing in an instant if necessary. Plan on having a couple flotation donuts on the line so you can find and retrieve it in the event of a quick release.

Just my .02¢ - I am glad that you brought this up and I'd love to see some pics of your gear.

Looking forward to more thoughts on this topic.

d

_________________
Klepper Aerius II
Klepper T9
Long Haul MK1 Expedition 'light'
Klepper S4 sail rig
Kayaksailor 1.6 +genoa
BSD 36HP


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PostPosted: Sun May 10, 2015 11:49 pm 
Brotherhood of the Golden Paddle

Joined: Sun Aug 16, 2009 10:05 pm
Posts: 1398
Location: South Salem, NY
One more thought... big following seas can be really scary. I've been there in a small boat. Having the option to move the drogue to the bow and face those waves might be a lot easier than being stuck with them on your stern. Of course moving it to the bow really makes it a sea anchor... but hey, why get all tech... ha.

d

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Klepper Aerius II
Klepper T9
Long Haul MK1 Expedition 'light'
Klepper S4 sail rig
Kayaksailor 1.6 +genoa
BSD 36HP


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PostPosted: Mon May 11, 2015 6:20 am 
Brotherhood of the Golden Paddle
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Joined: Thu Apr 14, 2005 4:47 pm
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Location: Arlington, VA (i.e. Wash DC)
I like D's last point, but I think R's original point about the huge strains on the boat sounds right. But I'll qualify all that by saying I've read a lot about these things, but have no direct experience myself. Have others read Roger Taylor's books? He testifies on the use of a series drogue.

_________________
Chris T.
~'91 Klepper A2 w/ BSD schooner rig.
'64 Klepper Passat/Tradewind and T12 restoration projects.
Non-folding: Early '90s Old Town Canoe.
Previously owned '04 Pakboat Puffin II and '05 Swift (prototype), as well as an '84 Hobie 16.


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PostPosted: Mon May 11, 2015 1:11 pm 
chrstjrn wrote:
I like D's last point, but I think R's original point about the huge strains on the boat sounds right. But I'll qualify all that by saying I've read a lot about these things, but have no direct experience myself. Have others read Roger Taylor's books? He testifies on the use of a series drogue.


I've read a few of his articles some time ago, but I did a quick bit of googling and it was good to come across and read a particular segment in one of his books about the series drogue:

https://books.google.fi/books?id=3xcmBg ... ue&f=false

It underscores the importance of the strength and security of its attachment. Not that the plan is ever to be in such conditions in the boat in question, but things don't always go to plan, and I intend to do a fair share of coastal trips, so I'll be happy to have such a tool at my disposal.

I'll have to pick up that book and give it a proper read.


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PostPosted: Mon May 11, 2015 1:35 pm 
DLee wrote:
I understand your weight calculations but I personally think you're a little off the mark with the effective load you'll be dealing with. Yes, the boat can max out at 450 KG or 900#, but hey, you're not dropping the thing off a cliff and expecting the canvas or rubber to hold the dead weight in a fall, you're talking about using a drogue or sea anchor. Either of these anchors move, that's the idea, to help stabilize your boat in rough seas.

I have not used a drogue or sea anchor with the kayak but I have used a sea anchor for fishing on a 23' center console and it's not that big a deal. I recently acquired a sea anchor for my kayak and I hope to play with it this summer, but I have often heard that an effective drogue for a kayak is simply a line dragged from the boat. I'm not sure about the length but I would probably start with 50'-100' or 15-30 meters and see what happens. Got any pictures or links to the drogue you have?


I've not yet built it. I've ordered the cones pre-made from Austrailia, and will attach them myself.

Quote:

I think a couple really solid D rings sewn into the canvas both bow and stern (so four rings) would allow you to set up matching anchor trolleys on either side of the boat. Overkill I think, but do-able. With an anchor trolly you can deploy and retrieve from the comfort of the cockpit without any crazy gymnastics (to be avoided in rough seas). Attach the drogue and trolly it to the bow or the stern depending on conditions and usage. I would recommend just using one side and have the other standing by as backup or safety line.


I can't see any attachment directly affixed only to the deck or hull as strong enough. It would surely tear free under the kinds of load a series drogue will encounter. I'm sure such an attachment is fine for anchoring or using a sea anchor to slow drift while fishing etc. but not in storm conditions.

Quote:
I have a 150' anchor line that I run on a trolly for my Aerius II and although I have never used it in rough seas I have great confidence in it. I use the same bow and stern connectors that Greg referred to on his boat. They are plenty strong for this operation and I wouldn't have any issue with attaching my sea anchor to this rig.

Be cautious that the drogue or sea anchor that is not too big for your boat. Too powerful an anchor will cause a whiplash affect and that will cause damage. Also, I don't believe there is a fixed length for something like this, it always needs to be matched with the seas... so adjustment is necessary and having a cleat or something back at the cockpit running through the trolly makes this easy. The whole idea of the drogue is to smooth the movement through crashing waves or surf - that means everything moves and balances together. I don't think you should ever have anything (other than an anchor with plenty of scope) trying to hold a fully loaded expedition boat in place.

Speaking of adjustment, you'll want to be able to drop the thing in an instant if necessary. Plan on having a couple flotation donuts on the line so you can find and retrieve it in the event of a quick release.


Yep. It will have a float at the tail end, holding the weight 3-4 meters below the surface, which also will serve for retrieval if the drogue must be detached.

Quote:
Just my .02¢ - I am glad that you brought this up and I'd love to see some pics of your gear.

Looking forward to more thoughts on this topic.

d


Once I finalize the design and construction, I'll of course post photos of what I decide to do.


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PostPosted: Mon May 11, 2015 3:06 pm 
Brotherhood of the Golden Paddle
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We can discuss it more in the Coffeehouse, but I'll just say that I heartily recommend Roger Taylor's three books. Preferably one reads them in order. They are good reading. Taylor has really thought things through systematically, and through a lifetime of intelligent thinking. I don't agree with all of it, for myself, but I did thoroughly love reading all of the books.

_________________
Chris T.
~'91 Klepper A2 w/ BSD schooner rig.
'64 Klepper Passat/Tradewind and T12 restoration projects.
Non-folding: Early '90s Old Town Canoe.
Previously owned '04 Pakboat Puffin II and '05 Swift (prototype), as well as an '84 Hobie 16.


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PostPosted: Mon May 11, 2015 4:20 pm 
lord high faltbotmeister

Joined: Thu Sep 06, 2007 8:05 am
Posts: 824
Location: atlanta, georgia
Very interesting conversation, just goes to show what interesting and sometimes curious/obscure the topics we consider!

So for the life of me I can not get to the relationship between the gross weight of a floating object and how that computes in the drogue equation. Isn't this a matter of drag+momentum/inertia (the latter having something to do with mass which has something to to with gross weight)? I have no physics background, but if I imagine the force needed to slow/arrest a drifting or blown or tossed floating object...well...I just don't know. I imagine that the lifting force of a wave could far and away exceed the weight of a boat, but who knows. Not me, but I would like to!

g

_________________
"There is nothing--absolutely nothing--half so much worth doing as simply messing around in boats"

1990 A1 Expedition
2010 carbon Klepper Quattro
BSD sail rig, 24' mizzen + 36' main
36' jib
Torqeedo outboard
1938 Sachs-Fichtel seitenbordmotor


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PostPosted: Mon May 11, 2015 5:18 pm 
Site Admin

Joined: Thu Apr 14, 2005 12:34 pm
Posts: 1754
Location: Southeast Michigan
I would recommend glue-on D-rings secured to the hull, just below the deck. These will distribute the load far more evenly than will frame attachment.

http://search.nrs.com/search/?p=Q&w=d-ring

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