Timber
Our timber is sourced from
sustainable managed woodlands. Sustainable woodland management,
often using a variety of species, is a way of working forests
in an alternative way to conventional forestry, such as the
mono-cultural plantation of productive conifers [*EcoNote].
Much of our timber is supplied by David
Smith in Killyman.
Oak (quercus robur
and the sessile oak, quercus petrae) is the wood
with the most versatile uses. Owing to its high tannin content
it was widely used for bark tanned sails, a practice we still
employ. Oak has a substantial sapwood area which is prone
to insect attack and is usually avoided for use. Most of our
oak is imported from Germany, sourced from sustainably managed
woodlands. Bends for knees and frames, though is sourced locally.
European Larch (larix
decidua, as opposed to the more knotty Hybrid or Japanese
varieties) is the classic material for planking, although
pine was also used on Lough Neagh.
Sitka Spruce (picea abies), our
Christmas tree, is traditionally used for masts and spars,
as it is clean and straight.
Hazel rods (corylus avellana) are
springy, bend in sharp curves and can be split lengthways.
They have been coppiced and pollarded for charcoal burning.
We use hazel for the ribs of our Dunfanaghy currachs. See
also Design
(R)evolution
Ash (fraxinus excelsior), which
likes an alkaline limestone or chalk soil, is bendable and
very strong, almost rivalling oak. Less durable than the latter,
however, it is also unsuitable for use in seawater.
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Tar
There are different forms of tar, defined
by their source of raw material and consistency: coal tar,
pine tar (Stockholm Tar and Achangel Tar), bitumen and pitch.
Pine tars have traditionally been used for preserving ropes,
nets and tackle. Or simply for their fantastic smell…
For waterproofing currachs, a mix of coal tar and pitch is
traditional. Here is some information about this process.
Tusker Tar
Tusker Tar is essentially coaltar mix that is solvent based
and quick drying. The best stuff to tar a currach really,
just very expensive and hard to get now. After some experimenting
and sniffing, this following recipe seems to work very well.
Wear gloves and goggles at all stages and do it outside or
in a well ventilated area, have a fire blanket and extinguisher
handy, just in case… Don’t leave any rags with
thinner crumpled up in the corner, they are likely to catch
fire! All materials can be got from well stocked hardware
shops, the costs are much cheaper than Tusker.
1. Heat coaltar and heat some pine pitch (Jeffrey’s
Marine Glue No.2) separately, about two fistfuls of pitch
needed for about 1gallon of coaltar. Careful not to overheat
them as both will easily catch fire when overheated –
its right when the tar is starting to steam, plus a bit longer.
Mix the two together when hot, stir well. Let the mix cool
down slowly and COMPLETELY.
2. Into the completely cold mix, stir 10-25% , the more the
quicker the drying (i.e. 1-2pt for a gallon) of Standard Cellulose
Thinners (this is sufficiently refined). Then add about an
eggcup/gallon of Terebene® or Japan Driers, also named
Paint Driers in the Ruskins range. Don’t add more than
it recommends on the label, less is more with this stuff.
And don’t use the eggcup for breakfast again. Mix all
well. If not used directly, pour into a sealable metal container
(plastic will be eaten by the thinners…). DON’T
attempt to mix in the thinners into the hot mix of stage 1
and DO NOT re-heat the mix. This will clear your sinuses thoroughly.
It will also lift the roof cleanly of your workshop…
You have been warned!
3. Brush on as usual, but cold!, using pure bristle brush
if possible (synthetic bristles tends to flick paint around
if not kept continuously in touch with the canvas) or the
old mob. Don’t put it on heavy, takes longer to dry
then. With the thinners, the paint sinks beautifully into
the weave, even with 15oz canvas. Where it touched the laths
on the other side, it even seeped through on contact. The
thinner does not affect natural fibres and doesn’t seem
to affect polyester twine of the stitching either, but I am
not sure about Nylon® or other synthetic thread (do a
test if in doubt, suspend some in thinner).
4. Ideally let it dry outside in wind and weather. This mix
was dry after 24 hours when I applied it.
Hot Tarring
The traditional hot-applied mix works best when really hot
and thinly applied:
1. Again, heat coaltar and heat some pine pitch (Jeffrey’s
Marine Glue No.2) separately, about two fistfuls of pitch
needed for c. 1gal of coaltar. Careful not to overheat as
both will easily catch fire when overheated. Mix together
when hot, keep heating it until good bit of steam is coming
of it. A tiny bit of Terebene can be added for good measure.
The trick with the smooth grey pebble dipped in to check the
temperature never really worked for me. Neither did adding
a pinch of ground-up toad’s nipples, collected at midnight
at a full moon.
2. Apply very hot with fencing brush or mob. Do it on a hot,
sunny day. Work quickly and keep the coat thin!
3. Let it dry outside in the wind and sun (or rain rather…).
Inside it can take ages to dry! Dropping it into seawater
when still tacky seems to cure it faster, too. The coat is
likely not to dry out completely, and that’s actually
not too bad. It means it keeps flexible. Adding more pitch
dries better, but the coat is likely to crack.
Bitumen-based Paint
Also known as roofing tar, painting tar. This stuff is dodgy,
to say the least. It is affected by UV light: after a while
it shrinks, contracts and cracks up. Even worse it pulls the
canvas with it and away from the gunwale after a few years.
It also does not penetrate the weave well. The only advantages
are that it is a bit safer to use than coaltar and it is easier
and cheaper to get. Even better from this point of view is
the water-based, rubberised paint, but it does not last very
well in use.
Pitch
Make sure your pitch is real pine-pitch, a natural pine resin
product. The bitumen stuff is still known as pitch, which
can lead to confusion. Real pitch looks like bitumen lumps,
but these are totally different, they are a mineral oil product.
Bitumen products and coaltar do not work together! Pitch is
now hard to get but you can buy Jeffrey’s Marine Glue
No.2 Black relatively cheaply, which is essentially pure pitch.
Old shipwrights did chew it in the days before chewing gum.
It is also good to seal under the rubbing strips to stop water
lingering around and rotting the canvas.
Suppliers and Costs
Bird Brand Coaltar c. £ 65 Stg./5gal. From Bird Brand,
also in 1 gal tins
Pitch; Jeffrey’s Marine Glue No.2 Black, c. £
30 for 12kg, www.marinestore.com
Standard Cellulose Thinners, c. £ 15 Stg./gal, any good
hardware shop
Terebene or Rustins Paint Dryer c. £ 6 Stg./500ml, any
good hardware shop
Tusker Tar refined coal tar c. £ 25 Stg. or € 40
per gallon
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Wood Preservative
An old shipwrights wood preservative: Mixing some hot pitch
with pure turpentine (or Paraffin) and some linseed oil makes
a great preservative for natural wood. Even without pitch
– if you prefer the wood not black – this is great
stuff. Mix c.50% pure turps or Paraffin (not the substitute
or white spirits) with another 50% boiled or raw linseed oil
(or a mix of the two) and add a bit of molten beeswax. Brush
on the wood, the turps carries the oil right into the wood.
This polishes nicely after a short while and waterproofs beautifully
when applied a few times. It also lets the wood breathe and
replenishes the natural oils in the wood. This stuff is as
good as all the natural wood oils from the chandlery I find,
stuff like Le Tokinois or Endeavour Marine Oil, etc., which
are very expensive.
For paint we experiment at the moment with organic natural
oils based paint ilke Auro. So far it seems to perform well,
but we will let you know in a few years... Again it lets the
wood breather. Conventional varnishes seal the wood, the gloss
layer works like double-glazing and the wood heats up in the
sun. When it looses its oils through oxidisation, the paint
starts to crack and lets water in, which then rots the wood.
Nasty…
A great essay on wood preservation in boat
building:
http://www.fky.org/restaurierung/menke.htm , unfortunately
in German…
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Canvas
and Rope
We use mainly cotton canvas and calico for currach covering
and sails. Currently it is still very difficult to acquire
organically or fair traded cotton (Gossypium hirsutum)
for boating purposes, so we make do with what is available
commercially. The main issue is the use of huge quantities
of pesticide. As more than 60 countries in the world grow
cotton, spraying amounts to almost a quarter of pesticide
use worldwide. And as nobody eats cotton, there is also little
concern about using particularly nasty toxins for this purpose.
Our canvas is supplied by Whaley’s
Bradford, who offer a variety of weight and sizes. Currach
covering ranges from a single layer of 12-18oz for the larger
naomhóga, to a double layer of heavy calico for the
Tory Island variety. All of these are sewn by hand with waxed
polyester twine. Initially we used an industrial machine but
changed to the ‘Speedy
Stitcher’, an ingenious little tool that is a worth-while
investment.
For the naomhóg sails we use a light 10oz canvas or
heavy calico weave. These are more difficult to get pre-stretched,
but rot-proof material helps. The Lough Neagh boat sails are
traditionally calico too, which were treated with a ‘paste’
to make them less porous. When using cotton canvas for sails
it is important to dry the sails thoroughly, if they get wet
to prevent mildew, which eventually destroys the canvas. Traditionally
all sorts of preservatives were used, from oak bark to earth,
blood and catchecu.
The LN working boat sails are
made of medium weight Duradon, a synthetic woven sailcloth
that resembles canvas. As the sail is often kept on the boat
we decided to go synthetic in this case for reasons of longevity.
More about sail making on the
Techniques and also Sails
page.
No UK chandlery supplies hemp rope anymore, so we use manilla
and poly-hemp instead. Manilla is a natural fibre and is relatively
rot proof, has high strength and is UV resistant. Poly hemp
is strong and even though being synthetic, it has a natural
appearance and feel. Both are easily and widely available.
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Fixings
The rose-head iron nails in the original Lough Neagh boats
usually caused timber disease as a result of corrosion and
galvanic reaction. We therefore use either galvanised boat
nails or, even better, copper nails. For screws, bronze is
preferable over brass, again for reasons of galvanic reaction.
Stainless steel is a good inexpensive alternative, but 316
and A4 marine grade should be chosen over 305 or lesser and
A2 grades. The catalogue of Davey
& Co Ltd. explains the technicalities in greater detail.
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© Holger Lönze,
2006 |
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