Michael Storer Boat Design - Norwalk Island Sharpie NWIS

Rig Modification:Norwalk Island Sharpie 18ft - NEW Ketch and Yawl Versions


Michael Storer Design, apart from designing boats from scratch and selling plan packs also can advise on changes to existing vessels or existing plans.  We specialise in rudders, keels, centreboards, sailplans, sparring, accomodation layouts and alteration of plans to suit other building methods. 

The following is one example of our work ...

Robert Ayliffe, who is worldwide agent for the Bruce Kirby designed Norwalk Island Sharpies recently contacted us to modify the 18ft model.

For more information about the Norwalk Island Sharpie range click here for NISboats.

History:
Robert, perhaps more than anyone, has been responsible for refinements to these boats to improve safety, performance and ease-of-use.

I have spent a bit of time sailing them (that's me on the right in non-racing mode on Pittwater, Sydney - my schoolday stamping ground - note the uncluttered deck and general lack of stress! NWIS23).  I have had the opportunity to steer Robert's own boat to some race victories and near victorys.

The boats are easy to build, fast, incredibly easy to sail and a great deal of FUN.  Tacking or gybing the boats is a no-brainer - just put the tiller over - no need to have to explain guests how to handle the jib or genoa.

Perhaps the biggest breakthrough for the boats has been Robert's development of a light but rugged tabernacle system for the boats, so now the mainmast simply winches up from the cockpit in a few seconds - it is completely self aligning and self supporting through the whole process.  Raising the masts used to be the biggest bugbear with the boats, requiring the rigging of the mizzen mast in the fore hatch to act as a crane or a circus like juggle of the mast to try and lift and drop it into the slot before a gust caught it - do-able but not much fun!

The Project:
I have had a long design link with the boats too - in the early days when I worked for Robert I had developed a computer program to print out full size foil templates to 1/72 of an inch accuracy - so Robert asked me to make up foil templates to further improve their good windward performance by using a thicker, carefully shaped foil rather than the metal plate that was being used at the time.  It worked rather well so the foil templates have become a permanent part of the NIS plan packs

All that was about (gosh!) 15 years ago, but Robert contacted me recently to see whether I could do some work on the smallest of the breed - the very portable looking NIS 18.  All the other NIS's are ketches, but the 18 was drawn with a large single mast and a large mainsail for sparkling light wind performance.

With the introduction of the tabernacles it makes the large stick very easy to get up, but the problem is, that, when dropped it overhangs the transom by almost 2 metres (6ft).  In many places around the world (including Australia) it is illegal for there to be that much overhang.

From a mix of marketing and cruising perspectives there were advantages in going to a "split" rig .
    1/ There is a consistency of appearance through the whole range of the designs.
    2/ There are a wider range of sail distribution to reduce steering loads and increase control for different windspeeds and wind directions.
    3/ The boat will sit happily head to wind for extended periods with the mizzen sheeted tight so the main can be raised, lowered or reefed at leisure.
    4/ The ability to get rid of one sail or the other without losing control through loss of steerage way.

Robert asked me to take a look at the rig with the idea of changing over to a ketch or a yawl rig.  I was happy to take the job on, but did express some concern that it could be difficult to retain a similar sail area, perhaps sacrificing some of the light wind performance.  I am always very reluctant to reduce ANY performance as it is responsible for a considerable part of both safety and FUN aspects of any boat - and it would be such a shame to ruin the pedigree of boats as good as these.

The Result:
However with some careful fiddling we managed to retain the same sail area by increasing the roach of the mainsail (the curved bit on the back of the sail) and by going to a ketch version.  There was also a small shift in the position of the mast and a move to a slightly more upright position.

In the lowered position the mast only overhangs the transom by 500mm (less than 2 ft) - even less visually if the rudder box is left in place on the transom - which is normal practice with these boats:  A situation to keep even the hardest working highway police officer happy!

The mizzen mast in the standard spun tapered aluminium is very light (less than 20lbs 9kg ) and drops into place through the cockpit floor making it really easy to pick it up and drop into the hole.  The sheeting is on the transom which keeps the clutter out of the boat.  The tiller just misses the mizzen mast as it swings from side to side (for those of you who have read L Francis Herreshoff's wonderful "The Compleat Cruiser" you can guage the weather helm without looking by touching the mast with the thumb of your tiller hand)
 
"TURBO" For Hoons:
In Australia, "hoons" are people who like to draw attention to themselves by having loud, fast cars with excessive stereo systems and noisy exhausts.

It is also used in perhaps a more jocular sense for people who like going fast.

After completing the ketch version I realised one of the by-products of the ketch rig is that the geometric centre of the sail area is a bit lower than the original boat.  Also the centre of gravity of the rig is a little lower.  This opens the option to increase the height of the mainmast a bit to add a square metre or two of sail without making the boat to heel more than the original.  It would counteract some of my good work in reducing the transom overhang of the mast, but ... you just can't stop some people!

Why a Yawl:
The reason for choosing to draw up the ketch first is that it is possible to cram a more sail into the mizzen.

Basically the further back the sail goes, the smaller it has to be to keep the boat in balance.  In this case the mizzen for the ketch version is 4.82 square metres and moving the mizzen aft for the yawl brings it down to 3.3.

1.5 sq metres (16 sq feet) may not sound like a lot but it may make the difference between sailing fast enough to steer reliably when you have the mizzen only up or the mizzen may not be large enough or tall enough to hold the bow of the boat reliably up into the wind. 


It would be possible to have it bigger by moving the centreboard further back, but I was very keen not to monkey with the well proven structure and assembly of the original boat.

Also a bumpkin has to be fitted for the mizzen sheet - another spar that slots into the coaming and extends aft of the transom by about 900mm (3ft).  It can be easily removable for trailering, but there may be the odd occasion where it gets in the way - while picking your way though a crowded marina berth - could be one example.

The only way to be sure is to build the boat and test it.  The yawl mizzen may be perfectly fine in both situations

On the plus side it does eliminate almost all of the mizzen clutter from the cockpit, which may be an advantage at times.  It also opens the possibility of fitting a boom tent over the whole cockpit without having to make a hole for the ketch version mizzen mast to pass through - no leaks!

Conclusion:
The upshot is that there are now three different rig versions for the NWIS 18 with slightly different mixes of performance and convenience.  My feeling is that the Ketch is the best compromise, but that's me imagining using the boat.  When you imagine using the boat, the answer might be quite different!

Launching:
First Ketch NIS18 is launched on Lake Burley Griffin.  Kits etc available from NISboats.com

NIS18 sharpie by bruce kirby

Norwalk island sharpie 18

nis18 norwalk island sharpie bruce kirby


Norwalk Island Sharpies come in several sizes - 18ft, 23ft, 26ft, 29ft, 31ft and even larger
For more information about the Norwalk Island Sharpie range click here for NISboats.

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