Not only did we find a quick swan hiding behind a very ugly slug, but it shows in a visual way how our design process works.
This is what we started with. You can see how heavy all the bits are.
Quite a difference. Not to mention a stellar jump in sailing performance. It really was a pig. If one person stepped aboard the original version it would just about fall over.
This is the story.
A second hand boat with potential but terrible execution:
Duck Flat where I was working part time after my bicycle accident (dates this story to 2005) had something interesting in the used boat section of their yard.
A long, slender hull 24ft (7.3m) by 5ft (1.5m) with an obvious speed potential, but hampered with an excessive amount of deck gear, a silly keel and a mast and rigging that would have been adequate for a boat 50% longer.
The Ducks were told that the boat was a Northeaster or Nor’Easter which, I suspect, had been highly modified during the building process. (if anyone knows who designed it, where and when it was designed and whether there are any others please email me)
In the end it proved almost unsaleable – as soon as anyone looked at the cramped two cockpit layout they decided to walk away.
In the end the owner of Duck Flat, Ted Dexter, decided to buy it, with an eye for making it a fun boat for a bit of twilight racing. He trailed it down to Goolwa (at the bottom end of the Murray River) and entered it in a couple of races. He is not a bad sailor but finished, as they say, stone cold, motherless last.
Now I work for myself, but I also know where my bread is buttered – the Ducks give me quite a lot of work – so I make sure I go up to visit them at Mt Barker at least once, sometimes twice a week.
On one of my visits Ted started to talk to me about what to do about the Orange Boat. We decided to organise an afternoon and take the beastie for a sail. Appointed day was rather blowy with occasional rain showers, so the sail was off, but it gave me a good chance to have a look over the boat in its marina pen.
First, it was sitting well below its lines – the bottom edge of the transom was a good 3 inches (75mm) below the water – very damaging to performance, then second, on jumping aboard there was a clear problem with stability. If both Ted and I were standing on one side the boat would lean over at a startling angle – giving a strong feeling that she was about to go over.
There were four areas to blame
- The hull, particularly the deck was built much heavier than the designer had intended – about 350kg (750lbs) overweight – from the hull’s extra depth in the water.
- The mast and rigging was way too heavy and complex for the boat – (genoa, runners etc) – with the twin cockpit making it impossible to work the gear or to sit out to help keep the boat flat.
- There was an extraordinary amount of heavy deck gear including 4 winches – on a boat small enough for all sails to be handled by . . . hand!
- The keel, despite having a lead bulb at the bottom, had quite a high centre of gravity and was a hydrodynamically AWFUL shape – not just middling bad – but truly AWFUL – see section below.
- All of the above led to hopeless stability. It was truly scary stepping onto the side deck as the boat would lurch over towards you at an extreme angle leaving one clutching onto the sidestay and giving the feeling that she would capsize like a dinghy … if you grab a sidestay and lean outwards intentionally or unintentionally!
Weight Reduction Program:
In the photo to the right, do you see that post in the foreground? It is the mast tabernacle for the aluminium mast to sit on. It extends down to the bottom of the boat. When we pulled that out we found it was hardwood and weighed in at a hefty 39lbs (18kg) . . . let us say, there was a good deal of opportunity for weight reduction!
On my weekly visit Ted and I would stand beside the boat working out what to remove next.
We removed; all the deck equipment – 90kg,
Cut off the stern including a massive hatch – 40kg.
Cut a larger cockpit removing all the hardwood around the two cockpit openings – 90kg, threw away the rigging and mast – 45kg, threw away the rudder and oversized shaft – 15kg, Floorboards – 19kg, the massive mast tabernacle (quite adequate for a 40 footer) – 18kg, external gunwales – 8kg.
Ted also worked from the back to the front of the boat ripping out the hardwood frames and welded stainless steel angle floors substituting with 6mm plywood web frames so the boat wouldn’t lose its shape and to support the new lightweight cockpit that was to be fitted.
The cockpit was fabricated out of 6mm gaboon ply reinforced with a layer of fibreglass. It made the boat self-draining – so any water that comes aboard can drain out easily. The mast now sits on the cockpit floor and the compression loads are distributed through the length of the cockpit as are the keel loads.
Over a few weeks the final drawings and endless calcs to make sure the centre of gravity would be OK created a sense of where the project was going.
Each week Ted and I would have a discussion – me wanting to rip more stuff out (or rather get Ted to do it!) and Ted wanting to minimise the amount of work that I was suggesting.
I could certainly see his point of view, but one of the great things about being a designer is that I can put forward all these great ideas, but I don’t actually have to follow through with any physical labour!!!
In the end the only areas where I didn’t get my way were to replace the foredeck (12mm ply where 6 or 8 would be enough) and the stem knee – a massive grown knee and some stainless steel strapping transferring the forestay load to the stem (overkill – two straps 50mm by 4mm stainless- 40 times stronger than needed – the forestay is only a puny 4mm wire). I guess we can do something about them later if the local competition becomes tougher!
Also see the EPOXY and Boatbuilding FAQ for more detailed info about the methods and troubleshooting and preventing problems
Keel Development – Efficiency with Shallow Draft and Easy Building:
While by blurring our eyes we could see some potential for the hull … as I said, the keel was awful.
There was no attempt at making a hydrodynamically effective wingshape. The drop down section in the middle, when deployed would improve stability, but was completely unshaped – a square sided square edged brick shaped piece of lead filled stainless steel about 40mm (1 3/4 ins) thick. Its pivot bolts simply poked out into the waterflow and it had a cable for raising/dropping also in the waterflow.
There had been some attempt to get some weight low by adding a bulb, but instead of a streamlined shape the front and back ends were simply cut off at a 45 degree angle.
No wonder the boat could never get over 4 knots unless heading downwind in a blow.
Ted wanted to improve things. I came up with drawings for a keel with more regular draft of 4ft, but Ted said that for the Lower Murray River he wanted 3ft. This was well out of the range of normal high performance draft so I was really reluctant.
And then I realised that he was talking about 3ft draft overall. The boat was to be raced against the local fleet of high end performance trailer yachts which had bulb keels that could be cranked up and down at will. We would be stuck with the standard keel draft to get over the sandbars and limestone reefs of the Lower Murray River.
Could we get good performance? It became of question of doing the best job possible but making no promises to Ted. Because we didn’t have span, depth, we had to make up with area. So how much area would compensate for the short span was pure guesswork. Too much area and the boat would be back in slug territory.
With a bit of fiddling and the choice of one of the relatively new computer developed Eppler laminar flow sections which is relatively thick we were able to get a significant lowering of the centre of gravity – 229mm as well as providing a section with significantly lower drag and higher lift.
The rationale was that the long chord (fore and aft) length of the keel made it hit the Reynold’s numbers for laminar flow sections for a further drag reduction … if Ted kept the keel clean.
The upper stub of the keel is a simple ply box. It is a great construction method. If you build of solid timber it takes forever to shape the stub and get it sufficiently accurate for the keel to work effectively. However, when building of ply, if the internal framework is the right shape then the ply will conform producing beautiful fair surfaces that require a minimum of filling and sanding. The lightness of the box for the stub also makes it highly buoyant allowing for quite a few extra kilos of lead to be added to the bulb.
This is a drawing of a different boat keel, but the same method. It allows some degree of taper and rake to be incorporated in the design.
The keel was attached by the now “old” method of drilling oversized holes in the wooden keel structure for the bolts and pouring thickened epoxy around them which is allowed to set. We did use conventional nuts to hold the finished structure in the boat – in case we ever need to remove the keel.
The rudder was changed to get rid of an excessively heavy arrangement and to close the gap between the top of the rudder and the hull for greater efficiency. The boat will now spin in its own length.
|Another Storer Keel – The Fallen Keel|
“MIK – my keel fell off”
No link yet Come back next week
The downsides of the old rig were that the mast was very tall but not carrying a lot of sail. It also was complicated to operate (uppers, two sets of lowers, 2 runners, 2 jumpers and a backstay) and required several genoas and jibs of different sizes be carried. The genoas required winches.
We decided to get rid of all the junk and go for a much lighter mast with a simple dinghy style three stay rig, but with a pair of lowers. We also did away with the backstay which allowed us to carry more sail on a much shorter mast by having a large dinghy style roach.
We are very grateful to Brett Averay at Binks Sailmakers in Adelaide who filled in the details about how the lowers interact with the three stay rig as well making a red-hot set of sails for the boat.
The mast is 1.3m (4ft) shorter than the old one and about half the weight.
Such a set-up can be arranged to have an automatic gust response as wind velocity changes which reduces the workload on the steerer and the mainsail trimmer.
Set up this way it makes sense to have as much of the sail area as possible in the mainsail – as it reacts automatically, and to only have a small jib that can be handled without winches (ie simple 2:1 jib sheets) for fast tacking and quick trimming.
It means you can simply hoist the two sails and go sailing rather than fuss about whether to hoist the #1 or #2 genoa or the working jib for the expected conditions. Performance can be inexpensive when mixed with simplicity
The mast is a new lightweight section that we are able to get made on a custom basis (for a fraction of the cost of similar masts) and is now is light enough for one person to push it up by hand after trailering.
It is a standard round extrusion below the hounds (very cheap) and was fitted with a spun tapered upper mast.
The secret go-fast that the designer never discussed with the owner.
I know Ted very well. He is a thoughtful builder, but he is a blackbird of the first order.
“You can’t possibly throw that away”.
I know that light boats like this are really bogged down if they are used as a rentable storage unit.
The only storage on this boat is under the centre console. Enough for odd bits of string, a bucket, sponge and a bottle of Jif for cleaning.
It will never put on weight in middle age. Also there has never been anything stolen from the boat. There is just nothing there that is not bolted down.
Final touches – it is all in the paintwork.
Initially the “orange boat” was a bit of a joke amongst the Duck Flat Staff as it gradually was hacked to pieces – but as it started to come together the questions changed from comments about “generating firewood” to “just how fast do you think it will be?”. Ted was going to paint it orange again, but as the boat started looking more and more striking, he decided to go with a white hull and deck with light grey non-skid paint.
Keeping it subdued keeps the fundamental shape clear and clean.
By this time it was attracting the interest of almost everyone who entered the factory. A new set of kevlar/carbon sails arrived, put together by the excellent (and very helpful) Brett Averay at Binks Sailmakers in the city (Adelaide!).
As the designer I was nervous about a number of things.
A good example was the question from the Duck Flat workers as the boat started to take shape – “How fast will it be?”. The only answer I felt really comfortable with was “I don’t know, but it will be a lot faster than it was”.
After all we had reduced the displacement by over 25%, increased the stability, added more sail area, made the boat much stronger and stiffer. All of it looks good on paper. But where paper falls down is that it never counts on the interactions between all the different factors.
So on launching day my concerns were
1/ Would it float in trim? Not too bow down or (worse) stern down. The calculations showed that the weights were all a little further aft than ideal. It would have been possible to do a full computer model of the boat, but there was no-one to pay for the time involved. If we had been able to do a computer model concerns 1 & 2 would have been completely resolved and #3 would have been mostly resolved.
2/ Would if float high enough for the transom to be out of the water?
3/ Would there be enough stability to carry the larger sail area?
4/ Would that fancy keel section work effectively to stop all that sail area from sliding the boat to leeward? The conventional thinking is to get good upwind performance, just add draft and put the lead on a bulb. Because the boat was being sailed at Goolwa at the bottom end of the Murray River, the draft had to be limited to 3ft (900mm) because of the shallow water. Would the newfangled Eppler section work at such a short span?
5/ How would the boat balance? Would it have weather or lee helm – would the rig be able to be moved enough to make sure it did balance nicely?
Launch Day – did it float? And how did it float?
After Ted and I loaded the boat onto the road trailer and chucked everything we could think of (including the kitchen sink) into the car we started on the hour drive down to Goolwa. We stopped along the way at the local weighbridge to find that we had removed 320 kg (plus or minus 10kg) from the original 1000kg boat – in line with our target.
Launching – did the boat float and how did it float?
The first moment of truth was as the boat floated free of its cradle . . .
As you can see, both bow and stern are free of the water and (Hooray!), she is sitting very nicely on her lines. The top of the antifoul is now about 65mm above the water at the bow and 50mm above the water at the stern. Formerly the top of the same antifoul line was 25mm under the water. I could cross #1 and #2 concerns off my list.
With Ted and I aboard we could now move about the boat with impunity – with both of us on one side the heel was about 10 degrees . . . Very Acceptable – but the sail area still looked large in relation to the draft of the keel.
Did it sail?
As you can see from the above pic, wind was very light 5 to 7 knots with occasional gusts – so it wasn’t going to be a test of straightline speed. However upwind, my guess was we were doing about 4 knots in 8 knots of wind – quickly overtaking a Farr 750 that was sailing back from Clayton. Considering that 4 knots was the MAXIMUM upwind speed before the mods, to be hitting it in 8 knots of breeze was highly reassuring.
Maneuverability was excellent, the boat able to spin around in its own length – feeling much more like a racing dinghy than a yacht – the result of a good rudder section and minimising the gap between the rudder and the hull.
Downwind with the jib extended on the whisker pole the boat felt quite slippery, accelerating in even the smallest gusts. Tacking angle was pretty close to 90 degrees – not too bad for the light wind.
I went on a quick solo sail while Ted snapped some pics. By that time there was hardly enough wind to fill the sails, but as I came into the dock it was clear that the boat had a great deal of speed (pics left and below)
Ted and I walked away from the first sail pretty happy with ourselves.
So how did the racing go?
Two days later we were down at Goolwa again – rigging for the race while fending questions about about the “New”, “Cool” boat. “er, actually it’s the old boat”.
A nice little breeze – 10 to 14 knots – so a perfect test of the basic concept. Our 22 competitors are mostly hot trailer sailers – Rosses, Elliots, a Blazer, a couple of Magnums, a Spider, the Soling, a Diamond (YW Keelboat), some Restricted 21s with their clouds of sail – all quick classy company.
We are a bit disorganised so we decide to sit just below the start line, and sheet in as the fleet comes up to us immediately before the start. Really rotten tactics, but it is easy to organise!!!
Fleet is coming up fast, gun goes, we have no speed and Ted is tending to pinch a bit, so I get him to sail a bit full and let the boat accelerate – the boat about 4 metres to leeward gets a bit miffed as we drop down on him.
After 30 seconds of settling down we are starting to match their speed, then a bit more, until it is clear that despite having the smallest mast in the fleet we are going to be 5th to the top mark.
Reaching and running, there is no need for excuses as we easily hold our place. We reach the bottom mark at the front of the second bunch (still 5th), but the first 4 boats had a slightly stronger wind so have pulled away from the rest of us.
Upwind again and we finally get completely clear air – quickly pulling away from the surrounding boats and making up almost all the distance to the first bunch – really fast. Ted was finding it hard not to smile! I was somewhat on the cheery side myself.
Since then we have raced the boat six times. It usually finishes within the top 5, occasionally dropping down to 8th out of 20 or 25 if we have a bad race.
It still has the smallest mast in the fleet and is tremendous fun to sail for two or three, quick to rig and derig, and it looks very nice indeed!
What I would do starting from scratch:
This is a doodle of a new version of the Orange Boat. Same rig, same keel, same aesthetics, but a simpler and much lighter build. Ply main panels and soft chines of cedar strip.
The objectives are:
- Easier to build
- Same performance parameters and principle dimensions – proven performance
- Lighter hull – the weight removed from the hull to be put into the keel for more stability – even better upwind performance
- Use of the same keel and rig design as the current boat – proven performance