One thing all Wharram catamaran owners have in common is,
they like to have their lady tightly bound
I’m talking of course about their catamaran.
Loose lashings and she will sail like a pig.
Drum tight lashings and she becomes a greyhound,
able to be powered up, and driven hard.
Wharrams are a very popular breed of catamarans,
or, more accurately, double- canoes.
Lashed together with rope, they have the most proven safety record of
any multihull.
These designs deliberately lack bridgehouses
to minimize windage and increase safety by keeping
the centre of gravity low while keeping bridgedeck clearance high.
So, instead of a bridgehouse to join the hulls together,
they use cross-beams. Cross-beams can place large loads at their
attachment points to the hulls. To prevent failure at these stress points,
rope lashings are used It’s the same principle as the tree that
bends to the wind, but doesn’t break.
We re-lashed Luckyfish in February, 2017 on the island of Grenada.
Terrence O’Connell runs a boat care service for absentee owners.
Through Terry, I was able to arrange Kevin, Shanti and Solomon to provide the manpower
to do the lashings. The Tiki 38 has 12 lashings,
3 on the outside and 3 on the inside, of each hull.
Lets get the jargon out of the way. The lashings are comprised of turns.
The turns provide all the strength to the finished lashing.
Each turn passes over the top of the crossbeam and under a lashing strake on the hull.
Once the turns are completed the Frapping is applied.
The frapping provides extra tension to the turns.
well good morning everyone. it’s lashing day.
i’ve arranged with terry to come along with three of four guys to
help us heave on the stick i’ve just had this piece of oak lathed up
hopefully its got the strength we are going to get these guys trained up
on the marlin spike hitch
and also the in-seam lashing method that we learned from hokulea
lets see that again do that again
that’s just to fast, come on its just like, you lay it on top,
you flip it over and then you just roll it under like that
and you flip it over like that
so, you know how i told you that you get two guys each side
sure so with a bigger stick we would pull like
this and we would pull it together.
so it should be an interesting day. and a fun day.
well this is the rope i will be using to replace the 8 mm braid
which has stood up pretty well for 5 years there’s no sign of any wear on the rope
if we follow what bruce was saying on hokulea the braid simply cant be stretched out
you cant get all the stretch out with man-power so im replacing it with this 6mm or ¼”
polyester or dacron
from new england ropes it’s got a breaking strength of 2,000 lbs
it’s 3 ply laid rope hopefully its going to be up to the task
because of the reduction in the strength of the 6mm
over the 8mm the number of turns around the beam and hull
needs to be increased and i am hopeful that we’ll get 8 turns
in whereas the braid had just 6
from the calculations on the strength of the two ropes
8 turns on this should provide strength equivalent to 6 turns on the 8mm
for the 6mm it has a 4% stretch before breaking
which is pretty good. with the guys heaving on the stick
we are going to be able to pull out probably half of that stretch
leaving what, a couple of percent maybe for shock loadings on the boat
which is what the lashings are really there for
just to absorb those peak loadings from wave impacts and that sort of thing
Oh shit
but the principle is to try and eliminate as much of the stretch
as much as possible to make the hull as rigid as possible
so we can get all the energy from the sails straight into the hulls and
into forward propulsion any flex in the boat dissipates that driving
energy and just reduces the efficiency of the boat
so rigidity is key, with just a small amount of
shock absorption left for those extreme loadings
It took us 2 days to re-lash Luckyfish.
But, before we could get started, the guys had to learn the marlin spike hitch.
OK, one more demonstration You've got it man
Hold and that twist That's it
Oh Yeah I got it
Who's next? One more
The pressure is on, Kevin. You've got it
That's looking good. Yeah man. Is that first time is it? First time? Yeah?
The lashing begins with a starter rope, tied to the lashing strake with a round turn
and two half hitches. A bowline is tied at the correct length in
the other end. The bowline should be positioned at the point
where you want the frapping to begin.
The lashing rope is secured to the starter rope with a bowline.
I told the guys that their objective was to try to break the rope.
At 2150 lbs breaking strain that didn’t seem possible,
but it would get the lashings as tight as can be.
The first turn begins against the inside edge of the beam pad
and against the hull under the lashing strake spacer.
Each turn crosses over the previous turn on top of the beam.
On this side And so you have this one that you need to
lock, yeah? And so you need to go over this one
But you lock between the seam here, like this And then, when you are going to come up, you
are going to come up between the seam
and then lock... It takes a lot of force to pop the turns into
the seam. I want to hear that popping sound.
Alright Yeah
That's beautiful Yeah, when they pull down, I just want to film it.
As the rope is passed from under to over it
is pinched to hold the tension. This process is aided by the friction from
popping the rope into the seam. Tension is applied from the underside and
the topside on every turn.
Once we completed 8 turns, we passed the end
of the lashing through the bowline on the other end,
released the starter rope and pulled down hard,
before securing with several half hitches. Finally, we applied the frapping.
This can be done with a separate rope or the tail of the lashing.
We wove the frapping under and over and applied tension on each side,
before securing with several half hitches.
Small wedges aided this process by providing
a space between the turns and the lashing pad.
This is very much an organic process and we found that
each lashing improved as we went around the boat.
These guys have got this stuff so well worked out now
They are going to be teaching others how to do it.
When we started on the inside lashings, the boys did manage to break the lashing rope.
Probably due to friction and heat over the bowline as we completed the turns.
This made me reconsider completing the whole boat with 6mm,
as it was very much a test and not the 8mm double braid
recommended by the designers. So, we used the old 8mm double braid on the
inside of the boat as a precaution, and would monitor how the 6mm works on the
outside over time. We left the two inside aft lashings until
last as these two undergo the most load on the
Tiki 38.
By this time the guys were really working
as a team. The tension they were able to apply on those
last two lashings made me realize that,
with experience, there would be nothing wrong with 8mm double braid all around the boat
using just man-power and the methods shown to us by Hokulea.
By way of back-up, if you do find a lashing is becoming loose
on a long voyage, as we found on our trans Atlantic crossing,
you can add a wedge, until the lashing can be redone.
With the lashings comes the ability to dismantle the boat for shipping.
For example, the Tiki 38 can be transported anywhere in the world
in two 40’ high cube shipping containers.
So, one of the neat things about the Wharram
is this lashing strake. On both the inside and outside of both hulls.
It's so useful for so many things. But, one of the main ones is
scrubbing the hull. It gives you something to hold on to
apart from being a good thing if you have a man overboard as well
It is something for them to grip onto the sides.
Yeah, so that is quite easy. I can get right to the base of the keel.
It's not really any effort at all. And, it saves you from having to use ropes
and goodness knows what to try and get down.
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