Goat Island Skiff - Rig and rigging details for efficient lug sails

UPDATED INFO SOURCES

Buildng a GIS is now about $300 cheaper than any comparable boat.  Sails are now available from reallysimplesails.com a partner company I helped set up and developed the sails for.

More performance info that's relevant to every small to medium size lug rigged boat.*

More GIS articles and information

Sailboat Performance WIKI - theory and methods

We have done extensive research of traditional solutions to rigging and have updated them to improve the performance of the boat on any point of sailing and any windspeed.

Most lug setups are pretty poor - mostly because the designers haven't done the research and haven't spent enough time sailing with the wee
beasties or just don't say how much to tension one part or another.  Also many designers are hampered by being unaware - or even reactionary toward - some of the advances available from the rigging methods and materials that modern boats use.  And others don't document what they know so the builder can set up the boat optimally.

For those who think traditional rigs are slow and cumbersome - they are in for a lesson.  Properly set up a balance lug rig (in particular) has very similar performance to any mainstream conventional sailboat rig when fitted to boats without trapeze or leaning racks.

Modern and novice sailors are horrified about the lugsail being distorted by pressing against the mast on one tack but the effect is quite slight.  I can notice it a little but I have a background in racing boats where (hopefully) I can feel performance differences of a few percent.  80% of sailors are just not going to notice anything at all.  In very, very light winds (0 to 2 knots - glassy water) it can prevent the boat from sailing one one tack - but most sailors would not even be aware that there was any wind in those conditions.  A tad more breeze and there is no problem.

But the great thing is that where a mainstream rig might cost you hundreds or a thousand dollars by the time you have fitted
The lug rig will cost a fraction of the same money and offer 90 to 95% of the performance.

A good equation if you ask me!  (I know you didn't - but I'll tell you anyway!)


* The exception to the advantages of the rigging system shown here is that the halyard system is prone to chafe on long ocean trips.  The halyard on the boat pictured above is 12 years old - and is in excellent condition.  But the wear and tear is different on larger boats that will spend extended periods making coastal or longer voyages.  But for smaller boats they are ideal.

Also I had a long discussion with Brian Pearson who races traditional lug boats in a regular race fleet.  While his rigging setups are perhaps more complicated than my simpler and easy to rig version, there may be something of serious interest to those seeking more performance from their lug rig.  My feeling is the single most useful addition is a loose footed mainsail which allows the rig to be powered up more.  However this will require the boom of my boats to be made a bit heavier to prevent excessive bend.
 

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The picture above is of Peter Hyndmans GIS "Gruff" which is now 12 years old.  Everything is original too - showing how cheap lug rigs are to run.  The pictures below are also of Peter's boat.

If you don't want all the details but just to look at the pictures that show you how to rig the boat then skip down to the Case Study heading below

Spars
The main requirement for the lug spars is that the mast be relatively stiff but the yard and boom be flexible.

With the rig set up this way the boat will have the gust response of a modern rig as the yard and boom bend and allow the sail to twist.  That's why such a light boat can carry a large sail but still be easy to handle in brisk conditions.

The GIS spar tapers have been specified to acheive this result. A builder or two have substituted aluminium spars but have found that it makes the boat quite hard to hold up in stronger conditions (article).  Generally because they have chosen sections that are too stiff.  Aluminium will work but just have a look at the pictures  on this page.

Sail
The sail has to be cut to allow for the bend of the spars.  When the downhaul is tensioned correctly for most wind strengths there is about 50mm of bend in the boom and yard.  Most modern sailmakers will know what to do to allow for this bend.

Fittings
My general choice of fittings for a boat is to choose parts from the budget range of marine fittings manufacturers.

Ball bearing blocks (pulleys) are just not required - leave them to the racing guys who are happy spending $700 to get a stay tensioning system working smoothly.

The biggest development in recent years in racing classes has been the use of thinner ropes.  When run through the blocks used for the older, thicker lines there is so much clearance that the friction is hugely reduced.

The other thing that is reduced is the cost - THINNER ROPES ARE CHEAPER!

This is of course assuming that you want to go to the bother of getting the best performance - and you would probably only be reading all this if you have some interest :-)

Another place I economise is by reducing the number of blocks by using simple rope purchases - like Trucker's Hitch Knots.  With conventional racing boats these are a no no because of the friction - but with traditional rigs there is not that much adjustment - about the only line that need regular adjustment is the downhaul to get tension in the luff of the sail which can be adjusted for different wind strengths if desired.  

A lot of adjustment a few years ago anyhow was just to take up the slack as the ropes stretch - but using some high tech ropes like spectra/dyneema or vectran mean that they don't stretch - so need little or no adjustment.

See how it works?  Modern ropes mean less adjustment which means you need fewer blocks.

Easy!

Ropes and types

Huge leaps have been made with ropes in recent years.

You can rig the GIS with cheap ropes if you like but I would like to suggest using modern high tech ropes in one place at  least.


So fully battened mains and short footed jibs for the most part - and hullweights that end up weighing with fittings around 10lbs/foot.
One of the big advances with small boat rigging has been the use of small diameter ropes.  They are less likely to rub when they pass through blocks (pulleys) so have less friction and are easier to adjust.  

Spectra/Dyneema
A few years ago ropes made of Spectra or Dyneema were expensive.  Now their use is so common that the prices have tumbled.

The one place where you should definitely consider using a high tech rope is for the main halyard (the rope that pulls the sail to the top of the mast) - or indeed the halyard on any boat.

The beauty is that they stretch very little.  So if you hoist the sail at the beginning of the day it will be still in the same position after 6 hours of sailing.  With  a conventional rope it has to be tighten
ed every hour or so over the same period to retain the sail shape.   In reality most people don't realise and wonder why the boat seems so sluggish and hard to get home at the end of the day.

A second advantage is that spectra and dyneema have fantastic UV resistance.

Choosing a slightly smaller diameter is important with high tech ropes.  When ropes stretch there are two phases
  1. Initial stretch - The twisted or braided threads that make up the rope are pulled as straight as the geometry allows.  All ropes made the same way stretch about the same during this phase - no matter what material they are made of.
  2. When the threads have pulled straight the load goes onto the fibers themselves - so spectra will stretch much less than polyester.
The result is that if you use too thick a rope all the stretch will be in phase 1 where the rope will stretch the same as something cheaper.  A bit thinner and you start to get a performance advantage.  The halyard is an ideal rope as the only time it is handled is to pull the sail up or drop it - both times when the loads are quite light.  But once the downhaul is tensioned it takes higher loads than any of the other ropes on the boat.

I would use spectra in a few other places if budget allows.  It is a good choice for:
Lashing the corners of the sails to the yard and boom
Downhaul
Maybe the traveller.

Vectran is another rope type that has even less stretch and can be considerably cheaper than Spectra/Dyneema.  But Vectran doesn't have the extremely good resistance to ultra violet light of spectra/dyneema.  Fine for a small boat that will be kept out of the sun but if it spends extended periods outside Vectran is a poor choice.

Prestretch
Most conventional rope is made of polyester or terylene.  With prestretch they make the rope then stretch it under very high load so that it will stretch less when put on the boat.

If you don't want a spectra halyard then prestretch is the next stop down - much inferior in my opinion - but might be OK for sails under 3 sq metres (30sq ft) - small canoe sails and the like.

Ronstan/Marlow makes a good one called Excel that instead of stretching a braided rope the inside is not braided at all - the fibres just run straight - so it operates as a prestretch.

Prestretch is also a good choice for 

Lashing the corners of the sails to the yard and boom
Downhaul (though I would give Spectra the advantage here and it is a short length only).
Traveller.

Double Braid
Is a polyester that is set up to be really sof t and pliable to handle.  It is perfect for the mainsheet and any other sheets on a boat as they are the ones that spend the most time in peoples hands.  Ofte
n there is a tendancy to get a big thick rope that feels easier to hold.  It is a bad choice - it makes the rope move very slowly through the blocks when released unless they are oversized (and expensive).

VB Cord/lacing cord


So fully battened mains and short footed jibs for the most part - and hullweights that end up weighing with fittings around 10lbs/foot.
This is a cheap white or coloured cord made of  polyester - it is very cheap and is good for lacing sails along the length of the the yard and boom.

Shock Cord
This is a line made up of a bundle of elastic rubber with a woven casing around the outside to keep it all together.  It is used as a bungee cord in a number of useful applications.


CASE STUDY - Setting up the GIS balance lug rig

The Goat Island Skiff (pictured above is a 15ft 6" (4.73m)  long boat with a 105 square foot (9.75sq m) balance lug sail

The hull has a good performance potential in modern terms because of the fineness of the entry and the light weight of the hull.  So the rig and setup also need to match the performance potential of the hull.

Here I go through the process of rigging a GIS and most lug rigged dinghies for the first time.

Rope Sizes and Conversion - Diameters

2mm3mm4mm5mm6mm8mm10mm
5/64"1/8"5/32"3/16"1/4"5/32"3/8"

Rope sizes and lengths for GIS
Rope diameters and types should suit dinghy sails from 70 to 115 square feet
GIS has 105sq ft mainsail
Note - Rope lengths are an estimate.  I have tended to overestimate.

PartRope Type and diamSecond choiceLength
Spar LacingsVB cord 3 or 4mmAnything else 3mm11m
Spar Corner lashingsSpectra 3mmPrestretch 3mm, VBcord
(if using VB get 4.5m)
3m
HalyardSpectra 5mmSpectra 6mm or Prestretch 6mm12m
DownhaulSpectra 4mm
(diff colour to halyard)
Prestretch 4mm4m
Traveller and ratchet block bridleSpectra 4mmPrestretch 4 or 5mm3.5m
MainsheetDbl Braid 8mm-14m
Boom square lashing, block attach. to spars
& ratchet blk bridle
Prestretch 4mmSpectra,  double braid6m
Stretchy rudder retainerShockcord 5 to 7mm-2m

Attaching the corners of the sails to the spars.
Corner Lashings - The correct way to lash the corners of a sail are according to the drawing below.  To get the proper shape in the sail the corners need to be pulled out toward the ends of the spars as well as held in.

Often you see corners lashed as in the picture on the left.  The picture on the right is the correct way.




Initial Tension
The sails need to be pretensioned on the spars - which can be drilled with holes - 8mm (3/8").  This means that there should be a crease in the sail along the length of the yard.  Don't sweat it really tight - but firm so a obvious crease is formed as shown below.  After that the  sail is laced with the VB cord.



Here is a picture of the lacing on the GIS sail.  Instead of using the spiral lacing I tend to introduce half hitches so the rope is a bit more aerodynamic as far as the wind is concerned as most of the lashing hides along the edge of the sail inside the wake of the spars.  This is more relevant for the yard than the boom.



Now that the sail is attached to the yard and boom it stays there - no need to undo all those knots!  

One good trick is to ask the sailmaker to make a long sailbag that the sail still attached to the yard and boom can fit in.

Setting up the mast
There are two things that have to happen with the mast.

A deadeye is fitted to the top for the halyard.  An alternative is to use a block and saddle, but this deadeye has been working fine for 10 years.  It goes on the back of the mast.

If going toward cheap - you can just drill a hole through the mast and clean it up with sandpaper and files so there is a smooth radius for the rope to pull through - termed a "dumb sheave".  I don't really like it except for very small sails as there is a lot of friction and it chews up the varnish so the mast is unprotected.  Some people fit a metal strip to protect the varnish but that's more hassle than the method here.



The other thing is a cleat for the halyard.  This goes on the side of the mast - bottom of pic below.  It needs to be on the side opposite the saddle or U-Bolt fitted to the deck adjacent to the mast.  The cleat is positioned around 350mm (14") above deck level.



So fully battened mains and short footed jibs for the most part - and hullweights that end up weighing with fittings around 10lbs/foot.

We will come back to this pic later.

General Theory of attaching Blocks to Spars
Some people like to screw or bolt blocks to spars.  I've used simple rope loops since I started building and sailing weird wooden boats rather than high performance conventional boats.

The funny thing is that high performance conventional boats now copy my method :-)  The main reason is that they don't have to drill any holes in the boom and risk weakening it.

Actually it is not my method - it is probably a thousand years old using a simple cowhitch to attach the block to the spar.  The loop is tied with a reef knot and the length of the loop is exaggerated in the middle drawing. The length of the loop should result in it looking like the last illustration in the series.



The Mainsail Halyard
This is the rope used to pull the sail to the top of the mast.

Some designers use a two part system where there is a loop of rope to hold the yard against the boom and a separate halyard to pull the yard up to the top of the mast.
'
That system is prone to jamming as if the halyard is eased the back end of the yard drops down which tightens the other lashing garrotlike around the mast.

The method I use was drawn from the canoeing chapter of "The Dixon Kemp Manual of Seamanship" from about 1870.  It is a brilliant system which uses one rope to do both jobs as well as keeping the yard horizontal during hoisting and dropping.  The only other designer I have seen use it is Iain Oughtred, but he doesn't specify it for all his boats.

One end of the halyard is tied through the forward hole in the yard - unlike the pic below I usually pass it through the hole then take it one time right round the yard before tying it with a bowline - this eliminates the risk of splitting the end of the yard.

The block is attached at the midpoint of the yard using a rope loop as above.



The only downside it has is in terms of wear and tear on larger ocean going boats.  I did suggest it once to a fellow who was cruising with a lugger.  He found it worked well in terms of raising and lowering the sail and reefing but it was prone to chafe.  

This is not a problem with small and medium size boats - particularly if you use spectra halyards - my halyard on the BETH sailing canoe is around 10 years old and the one on the Goat Island Skiff here is about 12 years old.

Square lashing the boom to the mast
Back to the photo used earlier.

This square lashing simply holds the boom close to the mast.  Don't tie it too tight - a little bit of slack will allow the boom to move easily.





The sail needs to be set in the right position relative to the mast.  Peter's boat has the front corner of the sail where it attaches to the boom around 400mm (16") in front of the mast.  For boats of other design looks closely at the designer's sailplan for the boat and duplicate the position and angle of the boom in the drawings for the boat.

Peter fitted the neat leather chafe guard to protect the varnish after sailing a few times.  Basically soak some leather in water for a day or two, cut it slightly undersize (about a 10mm gap), punch some holes in the edges that you want to sew.   Sew tight - when it dries it will be really tight.  

Note that the plans suggest that the boom should be 200mm above the partner - this is a mistake - it should be 200 to 250mm above the sheerline as shown in the drawing above

Downhaul
The downhaul is used to tension the sail - so is the most highly loaded rope in the boat. It is probably the most important adjustment in terms of creating the correct sail shape.

It needs to be medium firm for light winds - until the boat is moving reliably.  
Quite firm once the boat is moving well but is not difficult to sail nice and flat in the water.
Fiercly firm once the boat starts to be harder to hold up - it flattens the sail considerably which reduces power.

The diagram below shows two alternatives  The only flaw in the diagram is that the block needs to be higher closer to the boom.
 

Note that the plans suggest that the boom should be 200mm above the partner - this is a mistake - it should be 200 to 250mm above the sheerline as shown in the drawing in the section above.






Traveller and Mainsheet
The plans show a block bolted or screwed to the top of the middle seat.  Peter came up with a much better solution that doesn't risk pain and inconvenience to certain tender regions.

He used a simple bridle from the limber holes in the seat.  That way when the sail is not in use the block just drops to the floor.  Generally it is good idea to use a ratchet block which reduces the load your hand has to carry when holding the mainsheet.  A small simple ratchet block is perfect - no need for a fancy upmarket one and is worth the cost in terms of making the boat simpler and more fun to sail.  If you haven't seen one before get them to show you in the shop - you don't need one with an on/off switch.



The traveller is a rope that goes across the back of the boat above the tiller (yellow in the picture below).  
There is a block threaded onto it that is free to move across the boat.   Make sure the block lines up with the fore and aft axis of the boat - if it is crossways then the system will jam.  If you can't buy a block that will sit facing the right direction buy a shackle and put the shackle on the bottom of the block with the shackle running on the traveller line.




The ends of the traveller line simply tie round the inwale as shown around the bulkhead frame.  That is one of the reasons the screws were put through the inwale into the heads of the frames.



The mainsheet is tied through the eye at the back corner (clew) of the sail then threaded like the purple coloured rope in the photo above - or the more detailed shot below where it is green.

It can be stored in the boat tied to the mainsheet ratchet block.



Setting the sail
  1. Point the nose of the boat into the wind - it makes everything easier
  2. Put the mast in (the halyard should be already threaded with both ends made fast to the horn cleat).
  3. Unroll the sail (yard and boom should be already attached) and thread the main halyard
  4. Tie the square lashing for the boom (it is stored tied to the boom
  5. Hoist the sail almost to the top
  6. Attach and tighten the downhaul(it is stored attached to the saddle on the deck beside the mast)
  7. Thread the mainsheet
Setting up the Rudder and Centreboard

The plans are pretty good with this information, but here are some pics to show what it looks like and how it works.

This is the rudder attached to the transom.  I prefer the single pin type rudder attachment.  It cuts the risk of the rudder coming off the boat.  

A couple of tricks - make sure the rudder pin is not so long it goes in the water.  

The white flecked cord is shockcord - it provides the tension to hold the rudder blade in place.



Rudder blade in place - not loop handle - i've coloured it yellow with Photoshop so it stands out against the sand.



This is the centreboard - note loop handle..

.
If the centreboard slides up and down or won't stay down you can set up a piece of shockcord tied to the mast one end and tied to the centreboard handle at the other.  The tension of it pulling the board forward provides enough friction to make the board stay put.

There is a lot more information on other small details that utterly change the performance of any homebuilt sailboat or boat component.

Buildng a GIS is now about $300 cheaper

than any comparable boat.  Sails are now available from reallysimplesails.com a partner company I helped set up and developed the sails for.

More performance info that's relevant to every small to medium size lug rigged boat.*

More GIS articles and information

Sailboat Performance WIKI - theory and methods


Trailering
The trailer set up for a flat bottomed boat like the GIS is very simple.  Here is a picture of Peter's flat bed trailer.

The cross pieces go through directly under bulkhead 2 and bulkhead 4 so the boat has the maximum level of support.



And here is the tie down on the front of the boat.  It is bolted through at a height just above the front seat level.

The fitting has a metal plate that is fitted inside the boat and Peter has glued a 6mm plywood pad under that area to prevent the risk of the stem splitting.




Satisfied Customers

 

Goat Island Skiff Pages - Peter Hyndman

One of the first GISs built - Mooloolaba Qld.  Now resides in Mooloolaba.

Goat Island Skiff Pages - Dave Graybeal

Building in the USA - posted on the DUCKWORKS website 




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