Prod bindings

stoneagebowyer wrote:Mac, what do you most recommend for binding material? I have always loved linen, but if you think another type of material is both authentic and servicable, please give us your suggestions.

Dane

mac wrote:
In the past, I have tucked the ends through the bundle of parallel
cords between the figure 8s and the bow, but that's difficult, and never
looks right. I have also brought the end back under the last turn of
the figure8s, but I haven't seen anything like that in surviving
bindings.

I depicted the end simply tucked in between the
bindings and the tiller, because I have not found evidence for anything
fancier. The very end of the cord is not under any real tension, and
the bindings are typically covered with some sort of glue.

When
bindings get loose, it is either because the linen has stretched, or
the wood has collapsed. It is never a case of the figure 8s or the
frappings slipping. All in all, I think it will stay just fine without
any sort of knot.

I've tried soaking the cord in wax to make it less susceptible to
humidity changes, but that dosen't do it. The results are always the
same, whether the cords are waxed or not....come winter, the bindings
are loose. I count this as one of my nemeses.

mac wrote:Here is the next installment.

Ivo wrote:

The few bindings that I've looked at don't seem to be soaked in wax, but rather oily from constant handling. And then again, the other few do seem to be waxed or impregnated with resin like concoction(the *really dirty looking ones* )...still, the best solution I think would be a fresh tight binding...even Samurai got their katana tsuka-ito re-wrapped after a while.

Ivo wrote:
I think I've also seen this wicked bind...never so explored though. Thanks for another great addition, Mac. It's truly great having you here with us!

Ivo

mac wrote:

Ivo wrote:

The few bindings that I've looked at
don't seem to be soaked in wax, but rather oily from constant handling.
And then again, the other few do seem to be waxed or impregnated with
resin like concoction(the *really dirty looking ones* )...still,
the best solution I think would be a fresh tight binding...even Samurai
got their katana tsuka-ito re-wrapped after a while.

Ivo,

I
know exactly the sort of dirty bindings you mean. What is your
impression of the material that is coating them? Do you have any
theories about what substance of substances the coating in made of?

...

Air permeability and smo¨rring (dressing)

During sail fabric testing at UMIST in an attempt
to understand the functioning of wool sails the
decision was made to test air permeability. The
Shirley Air Permeability Tester was used on the
Skuldelev 1 replica fabric and on other similar test
fabrics. Initial tests showed that the fabrics had
such high permeability that the standard pressure
drop of 10 mm water pressure could not be
achieved at the highest flow rate. The test was
modified to 2 mm water pressure before readings
could be taken that were typically between 100–
150 cc/sec flow rate. Fabrics with such high permeability
would not function as sails because air
would flow through the sail and eliminate the
pressure difference between the front and rear that
creates the draw. It had been suggested that half
Figure 3. Schematic diagram of the Otar square sail. (Drawing:
Viking Ship Museum)
NAUTICAL ARCHAEOLOGY, 31.2
208
fulling the fabrics would reduce the permeability
but tests on loom-state and fulled fabrics showed
that air permeability was typically only reduced
by 30–35% by fulling, which was not enough to
resolve the problem.
A fragment of the Nordmore sail was then
tested under the same conditions and was found
to have much lower air permeability, 10–20 cc/sec.
The Nordmore sail had been impregnated with a
resin like finish and this tied-in with comments in
the literature about smo¨ rring (Andersen, 1995).
Smo¨ rring involves a two-stage process of, firstly,
brushing into the fabric an emulsion of water,
horse fat, (from beneath the mane) and ochre.
This is allowed to dry and then hot liquid beef
tallow is rubbed and smoothed into the sail. This
process was used twice to improve the light
stretchy sail of the Roar Ege and was also applied
to the Sif Ege sail (Andersen, pers. comm.). To
establish the effect of smo¨ rring, the Skuldelev 1
fabric and the other test webs were tested before
and after treatment and as part of this experiment
the extension of a 5 cm strip at 100 N loading was
also measured before and after. The air permeability
tests show that smo¨ rring dramatically
reduces the airflow. The sample SK1/4,
(Skuldulev 1 oppsett 4) shows that a high air
permeability of 111 cm/sec can be ‘tuned’ down to
4 cm/sec by the two stage process of horse fat and
ochre followed by beef tallow. The results for
Skuldelev 1 oppset 2 and Skuldelev 1 oppset 5,
both show the effect of each of the two stages. The
first application lowered the air flow from 68–
85 cc/sec down to 18 cc/sec, and the beef tallow
application reduced it further, to close to zero if
required, dependant on the quantity of beef tallow
applied. The other interesting result is that the
three warp-weighted loom fabrics included in this
test, AN1, AN2 and BF all give air flow values in
the region of 30 cc/sec prior to smo¨ rring and this
suggests that it is easier for a woman of average
strength to produce a very tight fabric on a
warp-weighted loom as compared with the horizontal
loom fabrics which all have initial air flow
values above 62 cc/sec, (62–111).
Finally the 5 cm strip testing demonstrated that
smo¨ rring reduced the low load (100 N/5 cm) extension
by approximately 30–40%, thus increasing
the tensile modulus accordingly. Smo¨ rring can
therefore be seen as an important aid in the
successful use of coarse woollen sails. It enables
the air permeability to be reduced to a level at
which the sail will develop a good draw and it also
has the effect of trimming the elasticity of the sail.
The inclusion of ochre in the mix is also of
significance. It undoubtedly acts as a good filler
inhibiting air flow by filling the voids in the fabric,
but it also has anti-bacterial properties which help
to prevent the wet sail from rotting.

Conclusions

The experimental archaeology associated with the
reconstruction of woollen sails for the reconstructed
Skuldelev ships has radically altered the
understanding of the functioning and efficiency of
such sails. In 1975 Svend Larsen concluded his
book, Vikingsernes hav, by stating that beating to
windward cannot be done with woollen sails
because they are ‘fleecy, nappy, yielding and
leaky’ (Larsen, 1975). It is now known that high
cover factor woollen square-sails could beat at 66
into the wind and most likely out-perform linen
and hemp sails. Furthermore it has been proved
conclusively that the process of smo¨ rring enables
the properties of the wool sail to be improved and
‘trimmed’ during use.
In a small way the research carried out at
UMIST as part of the Raphael ‘Seafaring’ project
has added to the understanding derived from
experimental archaeology by providing comparative
quantitative data within a framework of the
fibre physics and fabric mechanics essential for
the evaluation of the results. It is to be hoped that
this work will help to provide the foundation for a
better understanding of the design and performance
of woollen square-sails together with a
clearer appreciation of the high level of technical
skills and knowledge developed empirically by our
forebears.

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and rubber, anti-block in plastic films, porous support for chemical
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mac wrote:Over on this thread, https://thearbalistguild.forumotion.com/t525p15-leather-braiding-to-bind-on-stirrup#4593 there was a call for information on how prods are bound into the tiller.

Here is my first series of instructional sketches. It shows what might be described as a "plain and simple" binding. There is nothing here that most of you don't know already; but it should serve as a sort of jumping of point for the discussion of more complicated bindings.

Mac

mac wrote:I have been thinking on the subject of bindings and humidity changes, and talking it over with a friend who is a mechanical engineer. We came to a couple of conclusions, and thought of a few experiments to perform.

Our first conclusion was that horn would probably not be a good choice for providing an elastic buffer against humidity induced dimensional changes in the wood-linen system. Horn is just plain harder than wood, and if you squeeze the two together, the wood will dent before the horn compresses. The fact that you can dent most woods with your fingernail is sufficient to demonstrate this.

Our next conclusion was that it was probably not possible to seal the linen tightly enough against water that seasonal humidity changes would not effect it. It's a lot like the question of sealing wood. You can slow down the rate in which the material gains and looses water, but you can not really stop it. The historical coatings on the bindings were probably there to guard against occasional rain.

We devised a series of experiments to determine whether the culprit was the linen, the wood, or both. These experiments will involve binding metal with linen, and binding wood with metal etc., and subjecting them to cycles of humidity changes. I will try to do these sometime this winter.

The other experiment we thought of is to test the idea that I have been binding my bows too damn tightly in the first place. The presumption is this. If the bindings are too tight, one or more of the system might already be near to their yield points and, that dimensional changes wrought by seasonal humidity swings may be sufficient to cause permanent deformation. By contrast, if the bindings were "just tight enough" to do the job, it might be possible that the system has enough elastic "give" to survive these changes without ever inducing plastic deformation. To investigate this idea, I plan to bind up a model under low humidity conditions and then subject it to one or more cycles of high humidity to see if the bindings will remain tight enough to do its job.

Mac