Author Topic: Whitewater rafting bow knot  (Read 1415 times)

Learner

  • New Member
  • *
  • Posts: 2
Whitewater rafting bow knot
« on: May 15, 2018, 02:55:28 AM »
I am setting up an Aire whitewater raft.  You can view the bow of the raft here:

http://www.aire.com/aire-raft/r-series.asp

Note that there are two D-rings, left and right of the centerline of the boat. Ordinarily, there is a single D-ring on the centerline of the boat, in which case, attaching a "bow line" for mooring the boat is as simple as tying a "bowline". But not this particular raft.  In the photo in the web site cited above, you can see how the boat owner has tied a line between the two rings.  You can see that the line is pulled up into an inverted V.  What you can't see is that the bowline is attached at the top of the inverted V, is draped, coiled, over the back side of the thwart, and that coil of line is dangling, just out of view, but ready to be uncoiled at a moment's notice.

I can't tell what knots have been used to secure the line to the D-rings. In fact, I can't see any knots at all.  My concern is that the inverted V creates a potential danger in the event of a flip of the raft.  If the raft flips, the inverted V is a potential loop which can snag a swimmer's arms or legs.  I know this sounds gruesome and unlikely, but my I request that the reader trust me: this is a real possibility.  Moreover, there is no reason not to put some thinking into an improved knot. 

Also, I am interested in a one-line (one rope) solution.  Meaning, a single line connects the two D-rings, and leads to a long coil draped on the backside of the thwart.  But the inverted V is gone, and there is a single knot halfway between the two D-rings.

Your thoughts?

Learner

Dan_Lehman

  • Sr. Member
  • *****
  • Posts: 3903
Re: Whitewater rafting bow knot
« Reply #1 on: May 16, 2018, 12:26:59 AM »
Conceptually (even!), I don't see how you get out of
what I see as essential to the structure --i.e., that with
two anchor points one necessarily creates what you fear:
a triangle formed by the raft-between-points, and whatever
ties to them !?!?

If you give up one, then you have a non-loop structure.
But once you've tied to a 2nd, . . . <above> .
Quote
there is no reason not to put some thinking into an improved knot.
And this doesn't have a *knot* as a solution..

E.g., trying to reduce the loop size to minimal,
and thus snagging risk ... ,
one has a straight line between the anchor points
(which is the eye of an eyeknot or whatever),
and THAT puts unkind aggravated loading on
the rings --in force and angle.

PERHAPS one could create a structure that entailed
some solid (counting mesh/fine-netting as "solid")
material to fill the loop's "triangle" so to preclude
penetration ... !?  This will require some skill in
materials selection and stitching (presumably).

Or maybe a preliminary question is needed ::
what's the purpose of this line?
If it's largely something about handling the raft
away from in-the-water operations, then one might
go with some one-anchor attachment that can
become two-anchor when needed --e.g. an eyeknot
with long tail adequate to
 (a) bind eye together with a strangle knot for operation
 then
 (b) untie for making a reach and 2nd-anchor-tie as needed?!



|-:

« Last Edit: May 16, 2018, 10:52:55 PM by Dan_Lehman »

agent_smith

  • Sr. Member
  • *****
  • Posts: 1173
Re: Whitewater rafting bow knot
« Reply #2 on: May 16, 2018, 08:41:22 AM »
Hello 'Learner',

If you want to use rope (and rope is the obvious material choice) to attach to both D ring anchor points on the front of the raft, there is no way to avoid creating an 'included angle' / triangle.

I would suggest a composite knot structure consisting of #409 (double overhand noose) and a #1053 (Butterfly). Each knot attaches to a 'D ring' and is then centred so force is equalised to each D ring. The #1053 Butterfly eye is enlarged/lengthened to reach the other D ring.

Now, to reduce the risk of entrapment of a paddler, you could try:
1. Pulling the rope back inside the raft to create continuous tension - this holds the 'V' legs snugly up against the raft bow. This assumes that there is an anchorage point located somewhere at the bow on the inside.

2. You could use 'velcro' to hold the V legs of the rope snug up against the bow of the raft. This would means gluing velcro strips to the raft. Obviously you would need both 'hook' and 'loop' strips so that the rope can 'mate' to the bow and be held secure.

I do a lot of white water kayaking so I understand the risk of river hydraulics...although the chance of getting caught up inside the 'V legs' of the rope attachment to the front of the raft is remote - in 'big water', you could have arms and legs going everywhere so anything is possible...

Mark

SS369

  • Global Moderator
  • Sr. Member
  • *****
  • Posts: 1877
Re: Whitewater rafting bow knot
« Reply #3 on: May 16, 2018, 03:17:46 PM »
Good day Learner.

Since the rope attachment is primarily used for securing the raft and not necessarily a high load scenario, I would make the "v" as straight as possible leaving very little room (or none) for an appendage to slip under.

An adjustable sling of sorts could be another avenue to explore.

SS

NautiKnots

  • Full Member
  • ***
  • Posts: 93
    • Nauti Knots
Re: Whitewater rafting bow knot
« Reply #4 on: May 16, 2018, 03:35:27 PM »
Why not make a bridle (the v-shaped piece) with snap-clips on one or both ends?  When underway, you could disconnect one end or remove the painter (the bow line) altogether.  Then there'd be no danger of getting snagged in a capsize.  For towing, docking, or mooring, you would simply clip the bridle to both rings, which would distribute the load.

Another option would be to construct the bridle from a braided cover with a shock-cord core (or other integral shock cord).  When under load, the bridle would pull into a V-shape to better distribute the strain, but when stowed, it would pull up snug to the tube, offering less opportunity for snagging.

Regards,
Eric

Learner

  • New Member
  • *
  • Posts: 2
Re: Whitewater rafting bow knot
« Reply #5 on: June 01, 2018, 11:14:13 PM »
Sorry for being so tardy in replying to Dan Lehman, Mark, SS and Eric.  Just got back from a 7-day raft trip, and have been putting my boat away, playing catch-up at work, etc.  I really appreciate your thoughtful comments, all of which I read prior to my trip, and found very useful.

I will give detailed responses to your comments, below, but thought I ought to state up front what I decided to do, which was to secure a cam strap between the two D-rings, and tie a bowline at the midpoint of the cam strap.  Not very elegant, and definitely not the long-term solution I need to find, but it worked okay for this trip.  By tightening the cam strap, I was able to keep it snug against the thwart of the boat, and thereby minimize the entrapment danger. 

There are several things I don't like about my short-term solution.  It's ugly.  It's unconventional.  There's nothing to prevent the cam strap from loosening if the bow of the boat hits a rock head on, and thereby depresses the tab that opens the cam.  Tying a bow line to a cam strap is awkward because the rectangular cross-section shape of the strap interferes with cinching the knot tightly.  The metal cam presents an angular metal edge on the exterior of the boat, and thereby endangers swimmers who may happen to be tossed out of the boat in a big rapid.

Dan, your response was a spot-on analysis of the problem at hand: that a trio of lines creates a triangle, and the three-way forces are difficult to balance.  Your idea of a solid fabric to fill the triangle is intriguing, though I fear trying to engineer a working device that is up to physical stress that a whitewater rafting painter is subjected to when it is lined past a waterfall (which I have done five times in my boating career), or even just moored for the night in swift water (which I have done twice).

Your alternate suggestion is good that an system be implemented which switches as needed between a centerline two-D-ring system, and an off-center one D-ring system.

Mark, you helped me understand that there is no way to avoid an included-angle.triangle with 2 D-rings and a bow line.  I appreciate your specific suggestions of a 409 and a 1053 knot system, and scurried to my local library in the hopes of finding those in "Ashley Book of Knots".  But my library's 1944 edition doesn't show "double overhand noose" at 409, nor "butterfly" at 1053.  Can you please point me to where I should look for these?

Your idea of pulling the inverted V back inside the boat is difficult, because there are no D-rings on the interior of the boat, and I fear plastic welding new ones on the centerline seam.

Velcro strips is a great idea.  Have you seen anyone on a river with velcro glued to Hypalon, etc.?  Be nice to find out if glued-on velcro can survive the expansion/contraction of  thwart material as a boat is pumped up/down, or cools down/heats up.

SS, under ideal circumstances, the bow line is never under a high load.  Yep.  Hmm.  I rowed the Grand Canyon last summer, and the oar  tower of one the boats in our group rotated out of position while the boat was just entering Crystal.  The boat ended up in a ferocious eddy on the edge of massive hydraulic turbulence.  (Good thing it got trapped there, from the point of view of those on the boat!)  We portaged the entire contents of the boat down through cabin-sized bolders.  The boat itself came by the same path, at mountain-climbing angles.  Lots of stress was on the bow line.  Weird stuff happens on Mother Nature's rivers.

I am interested in understanding better your idea about an adjustable sling.

Eric,  thanks for your idea about snap-clips.  That's really a great idea.  Maybe a sturdier implementation would be those carabiner-like devices which conect via a threaded collet.  Your idea has the virtue of zero entrapment hazard.  I need to try this one out on my crew, which sits in front of me when I am rowing, and is responsbile for handling the bow line when we come to shore.  I wonder if they'll grumble?!

I don't think I am following your integral shock cord idea.  Can you post a picture of this fabric, or whatever it is?

To all, I really appreciate your ideas and help.  I chatted with a couple of other oarsman, and they were stumped, but thought I ought to contact the boat manufacturer for advice, which I will do.

I will keep you all posted as I make progress. 

Your further comments are welcome.

Thanks,

Learner

NautiKnots

  • Full Member
  • ***
  • Posts: 93
    • Nauti Knots
Re: Whitewater rafting bow knot
« Reply #6 on: June 02, 2018, 01:20:21 AM »
Your idea of pulling the inverted V back inside the boat is difficult, because there are no D-rings on the interior of the boat, and I fear plastic welding new ones on the centerline seam.
YKK makes an adhesive-backed snap-stud called a SNAD (see http://hub.ykknorthamerica.com/youtube-all-videos/snad-plastic-adhesive-snap-component-instructional-video).  They're often used on inflatable boats for attaching covers.  If you wrapped a short piece of webbing around the V-section of your bow line and installed the cap portion of a snap, you could pull it into your boat and attach it with a SNAD.  No plastic welding would be needed.

Quote
I don't think I am following your integral shock cord idea.  Can you post a picture of this fabric, or whatever it is?
You can see something similar at https://www.iboats.com/shop/davis-minishockle-black-18-snubbers.html?cm_mmc=&gclid=EAIaIQobChMIoIPXrtaz2wIVh7rACh3F_QUtEAQYCSABEgKJd_D_BwE .  If you're using tubular webbing, or flat-braid line, you can simply snake a short piece of shock-cord through it.  If you're using double-braid line, and the cover is strong enough by itself, you can remove the core and replace it with a bit of bungee half the diameter of the original line.  Either sew it in, or tie the ends to the d-rings on the bow.  Use a length that keeps the line taut when not under load, but stretches out under strain.  If you are using twisted line, you can worm shock cord into the middle between the strands.

I hope that helps,
Eric

Mik3e

  • Jr. Member
  • **
  • Posts: 13
Re: Whitewater rafting bow knot
« Reply #7 on: June 02, 2018, 02:38:23 PM »
Running Rig:
Option 1: Put in two stop-knots, before and after the first D-ring. Two are necessary to prevent the line from running out from either end.

Problem 1: if the D-ring is large and the line is thin it will not be possible to create a sufficient stop-knot. Try option 2.

Problem 2: the line tail can hang over the bow and drag in the water. If this is unacceptable then this whole idea doesn't work.

Option 2: hitch the line to the D-ring with an Anchor Hitch or equivalent.

With either option the tail can be as short as possible or several meters so it can be stowed in-board with a chance to stay there.

Bow-Line Rig:
As needed, feed the working end through the second D-ring and tie off on the standing end with a Bowline or equivalent.

Problem 3: with Option 1 the loop is somewhat self-adjusting between the two D-rings. With Option 2 it might be difficult to tie a loop that is properly balanced.

Mike
« Last Edit: June 02, 2018, 02:41:31 PM by Mik3e »