Bow/Stern Lines When Cartopping: Purpose?

(PeteCresswell) wrote:
> But my new Thule J-Racks came with bow/stern lines, ratcheting pulleys, and
> beeeeg open-ended metal hooks. Not what I'd choose to keep something attached
> to the vehicle when it's flopping on the pavement next to the vehicle at 60+
> mph....
>
> So, it seems to beg the question: what is the stated purpose of those bow/stern
> lines from the manufacturer's perspective?
>
> Take strain off the rack system? If so, you wouldn't want stretchy rope.
>
> Control the boat in the event of rack failure? If so, you'd want the lines tied
> securely to the vehicle and not held in place by open hooks.
>
> Keep the lawyers happy?

Just because those lines don't do the jobs well doesn't mean that Thule
didn't intend for them to. I would never use ratcheting pulleys on a bow
and stern. Simple 1/4" line tied in a tautline hitch does the job just
as well. Pitch them ratchet straps, or use up to trailer your motorcycle.


--
Steve Cramer
Athens, GA
 >> Stay informed about: Bow/Stern Lines When Cartopping: Purpose? 

Per Michael Daly:
>I still prefer the tautline hitch to silly gadgets.

It that's the same as a trucker's hitch, we're on the same page.
--
PeteCresswell
 >> Stay informed about: Bow/Stern Lines When Cartopping: Purpose? 

Per Steve Cramer:
>Just because those lines don't do the jobs well doesn't mean that Thule
>didn't intend for them to.

But it still begs the question: what's the job?
--
PeteCresswell
 >> Stay informed about: Bow/Stern Lines When Cartopping: Purpose? 

(PeteCresswell) wrote:
> Per Michael Daly:
>> I still prefer the tautline hitch to silly gadgets.
>
> It that's the same as a trucker's hitch, we're on the same page.

Trucker's hitch is overkill. A tautline hitch is simpler and just as useful.

Mike
 >> Stay informed about: Bow/Stern Lines When Cartopping: Purpose? 

Michael Daly wrote:
> (PeteCresswell) wrote:
>> Per Michael Daly:
>>
>>> I still prefer the tautline hitch to silly gadgets.
>>
>> It that's the same as a trucker's hitch, we're on the same page.
>
> Trucker's hitch is overkill. A tautline hitch is simpler and just as
> useful.

A tautline hitch will not hold under strain. A trucker's hitch will.

For light duty, uncritical applications, the tautline hitch is a useful
tool in the kit. For anything that needs to be held securely, and for
which there are serious consequences for not holding it securely, the
tautline hitch is counter-indicated. Note that it's holding abality is
severely compromised when used with "slippery" high tech lines instead
of classic hemp.

Like the square knot (reef knot) it's dangerous in the hands of the novice.

//Walt
 >> Stay informed about: Bow/Stern Lines When Cartopping: Purpose? 

(PeteCresswell) wrote:

> Per Steve Cramer:
>
>>Just because those lines don't do the jobs well doesn't mean that Thule
>>didn't intend for them to.
>
> But it still begs the question: what's the job?

It's a belt and suspenders thing. A belly line alone should hold your
kayak under most conditions. Likewise, a bow and stern line set-up
should be enough. By using both, you can be very sure that you won't
lose your boat when you have to stop or change lanes suddenly at 80 mph.

Or in other words, I like to attach it so that the failure of any one
component will not be catastrophic. Lines break, you forget to tie it
when you're in a hurry, two people are loading the boats and each thinks
the other has secured something critical, etc.

//Walt
 >> Stay informed about: Bow/Stern Lines When Cartopping: Purpose? 

Walt wrote:
>
> A tautline hitch will not hold under strain.

I've never heard anyone make this claim. It's basically a prussik and those are
used by climbers all the time.

Slippery rope won't hold knots of any kind well. However, I've used tautline
hitches with 6mm polyester kernmantle line and never had one slip. YMMV.

If you are using it for a tiedown and the boat launches off your roof, any slip
in the hitch will allow the boat to move away a bit, but will not release.

Mike
 >> Stay informed about: Bow/Stern Lines When Cartopping: Purpose? 

"Michael Daly" <michaeldaly.TakeThisOut@foo.bar> wrote in message
news:eo2dneibFKH0Lq7YnZ2dnUVZ_sydnZ2d@magma.ca...
> Walt wrote:
>>
>> A tautline hitch will not hold under strain.
>
> I've never heard anyone make this claim. It's basically a prussik and
> those are used by climbers all the time.
>

Deja vu.

I don't think its equivalent to a prussic, as its not a symmetrical knot;
its more like a 'half prussic'. The tension on a prussic is divided between
both running strands, which pull the loops tighter. The tension on a
tautline hitch only pulls the lower loops tigher, so it has (at most) only
half the holding strength. And a prussic cannot come undone, while a
tautline hitch theoretically can.

--riverman
 >> Stay informed about: Bow/Stern Lines When Cartopping: Purpose? 

The mid section lines hold the boat down to the vehicle. On most vehicles
where the racks are spaced less than 8' apart the bow and stern lines do two
different and complimentary things provided they are directionally opposed.
The first is to resist the boat twisting and the second is to prevent it
from shooting forward on a sudden stop or slipping back from wind pressure.

Re the type of knot. A truckers hitch gives you a theoretical mechanical
advantage of 2:1. It also allows for the change of direction of force when
tightening. You get to pull down instead of up, possibly over your head. BTW
the truckers hitch is not a stopper. It must be finished with a hitch of
your choice.

Not included in the discussion so far is the type of rope. Nylon will
stretch up to 30% and Polypropylene 22% when wet. This of course is the
reason for tensioning all the ropes. The only caveat is that your end ropes
do not bend or break your boat. I put the knot of my bow rope where I can
see it when I'm driving.

Sincerely,
Carey Robson
Master Instructor
www.CanoeBC.ca

"(PeteCresswell)" <x.DeleteThis@y.Invalid> wrote in message
news:qas5j2t1mt71afe8quuuen0vcnprec2d4c@4ax.com...
> Per Steve Cramer:
>>Just because those lines don't do the jobs well doesn't mean that Thule
>>didn't intend for them to.
>
> But it still begs the question: what's the job?
> --
> PeteCresswell
 >> Stay informed about: Bow/Stern Lines When Cartopping: Purpose? 

Per Walt:
>It's a belt and suspenders thing. A belly line alone should hold your
>kayak under most conditions. Likewise, a bow and stern line set-up
>should be enough. By using both, you can be very sure that you won't
>lose your boat when you have to stop or change lanes suddenly at 80 mph.
>
>Or in other words, I like to attach it so that the failure of any one
>component will not be catastrophic.

That's about where I was in my own view of it.

--
PeteCresswell
 >> Stay informed about: Bow/Stern Lines When Cartopping: Purpose? 

riverman wrote:

> I don't think its equivalent to a prussic, as its not a symmetrical knot;
> its more like a 'half prussic'. The tension on a prussic is divided between
> both running strands, which pull the loops tighter. The tension on a
> tautline hitch only pulls the lower loops tigher, so it has (at most) only
> half the holding strength.

If you look at a tautline hitch under tension, the bend in the standing line
occurs under all three loops of the tautline, not just the lower two. While
it's true that the prussik does add tension to both sides, if a tautline is tied
properly with a rope that isn't slippery, my experience is that it stays tight.

BTW - since the grip is in no small part due to the bending of the standing
part, if you make a prussik-like knot with too many loops, you will get a
diminishing hold. I think that the tautline hitch has somewhat more than half
the grip of a prussik.

> And a prussic cannot come undone, while a
> tautline hitch theoretically can.

True - I always finish the bitter end with a snug stopper to prevent this.

Mike
 >> Stay informed about: Bow/Stern Lines When Cartopping: Purpose? 

On Oct 17, 11:28 am, "Oci-One Kanubi" <rhop....DeleteThis@earthlink.net> wrote:
> You cannot
> break your boat if you cinch a trucker's hitch carefully, but you might
> with a ratchet.

The operational word there is "carefully." I've seen aging plastic
kayaks broken by enthusiastic tightening of a trucker's hitch on a
belly line. Also recently seen a guy break the gel coat on a fairly new
glass sea kayak with ratchets.

Put a trucker's hitch on a bow/stern rope and it's way easy to bend a
boat.

Steve
 >> Stay informed about: Bow/Stern Lines When Cartopping: Purpose? 

Per Oci-One Kanubi:
>I strongly recommend against the use of ratchets, because you don't
>have a good sense of just how much force you are applying. You cannot
>break your boat if you cinch a trucker's hitch carefully, but you might
>with a ratchet.

Also, I don't exactly get a warm and fuzzy feeling when I imaging a loose line
with a ratchet on the end flogging in a 60+ mph slipstream.... -)
--
PeteCresswell
 >> Stay informed about: Bow/Stern Lines When Cartopping: Purpose?