stinky

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Really nice information. How was the boat speed measured?

GPS and GPSAR software. I have a Sony smartphone which is waterproof so it is just turned on before the race and put in the halyard bag (on a lanyard!). I don't know how well GPS would work inside a carbon hull. Badly I suspect!

 

Steve, I'd have said that the Nethercott has a bloody great planing speed "hump". As you say I reckon its all to do with all that noise under the mast area. Tin Teardrop on the other hand didn't have much of one, and nor did my one off singlehander, which although rather wider was much more akin to the newer boats in bow section.

 

Bethwaite did some interesting more detailed analysis of the phenomenum, and what he reckons he found was that on modern style wedge hulls like the 49er, that there is still definitely a planing hump (and so the laws of physics haven't been rewritten), but that the speed that it occurs at varies very significantly with trim. What he reckoned was going on was that talented sailors (and Julian was normally steering the towed boat when they did his tests) were subconsciously altering the trim of the boat so it was always in the lowest drag trim for the speed being towed at. That does make sense to me.

 

 

Jim,

 

That's interesting as his books don't really suggest that - I suppose its too late now for him to make an official amendment, sadly! His tow tests are also shown with the bows being held in position and don't really represent the real world with all the forces focused in the centre of the hull and so were always a simplification.

 

 

Steve

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I think D/L dominates the discussion.

Even though a Nethercott is lighter for it's length than any other dinghy out there, a new rules boat is lighter still.

One thing we have learned over the past half century is that flare forward is slow. The Finns w built at Vanguard were as low and skinny as they could possibly be, and that follows through almost everything else I have tested. In essence the "classic" small boat bow was intended to slow the boat and lift the bow when a wave came along (one in a million, I know) In all cases you want to minimize the energy absorbed by wave encounters and still have enough reserve to go down wind. The New ICs solve this by shifting the CG and LCB aft, essentially making a longer water plane do the work of one that was marginally wider.

Yak Yak Yak

SHC

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...his books don't really suggest that - I suppose its too late now for him to make an official amendment, sadly!

 

Higher Performance Sailing (the second book) pp160-162. I didn't spot it the first time I read it. Trouble is the books are so dense its easy to miss stuff.

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Jim, Modern technology! wonderful isn't it! All we need now is the wind speed and direction to be recorded at the same time. That would give a lot of information.

 

I am interested to know how you identify the added resistance with "noise under the mast", as opposed to some other region of the hull.

 

Your comment about trim is very apposite and can make a huge difference.

 

Anglo Steve, What do you mean by a lightweight Nethercot? Same hull shape but just lighter? Or hull depths reduced to reduce the displacement?

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All we need now is the wind speed and direction to be recorded at the same time. That would give a lot of information.

 

I am interested to know how you identify the added resistance with "noise under the mast", as opposed to some other region of the hull.

 

Wind speed and direction logging: wouldn't that be nice:-) Its technically very achievable, but the trouble is putting an expensive and probably delicate bit of hardware at the top of the mast where its so vulnerable to getting trashed.

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Ok, here's a hull that I've marked on the centerline and BMS (is a poser boar thingie I was messing around with, so pretend...)post-906-0-34809500-1391551146_thumb.jpg

 

Close up of same

post-906-0-67235100-1391551178_thumb.jpg

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Internet is screwed up today, so one pic at a time

 

Hull with centerline and BMSpost-906-0-56872400-1391551288_thumb.jpg

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This is how the BMS wraps around the hull, if the hulls skinny, right?

 

post-906-0-12463700-1391551362_thumb.jpg

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So this string is the 2 m tape, and it's centered on the BMS tapepost-906-0-21151900-1391551433_thumb.jpg

 

So does it move like this?post-906-0-39441500-1391551477_thumb.jpg

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And when it gets to the edge of a chine, it goes like this?post-906-0-64519100-1391551607_thumb.jpg

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Or like this?

 

Or this sweeping radius theory

 

post-906-0-87709500-1391551688_thumb.jpg

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Or, imagine the table glass is the planing shoe, and the bottom of the glass is the bottom of the hull, and the string is the 1 m tape, and the ruler is the exterior chine, but the 1 m tape doesn't touch it, is it ok to have the exterior chine there? Assuming there's 11" inches of freeboard above it, and at BMS it's 30" in beam?

 

post-906-0-19360400-1391552163_thumb.jpg

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And this is how the 2m tape works on the side?post-906-0-87608600-1391552525_thumb.jpg

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Amati,

 

1) With respect to the 2000mm tape, centred on the BMS means that there should be 1000mm of tape forward of the BMS and 1000mm aft of the BMS. I only mention this because your photos do not indicate that.

 

2) Not the radius theory.

 

Interesting fact: If my maths is correct, the minimum possible girth at the BMS is 1126.2mm, so the 1m tape can never reach the sheerline. This means it will always be possible to flare at least 63mm of the topsides below the sponson line.

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Amati,

 

Your picture

lbov.jpg

is how I interpreted the rule. Obviously with the tape pulled tight to lie against the hull and centre on the BMS. It will follow a geodesic line, and what I could not quite understand was how to determine the end points of the tape. The instruction fore and aft seemed to be much too vague. The discussion since has indicated that the ends should be equal distances, around the hull, from the keel line. Still, however, not sure this is the correct interpretation.

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Amati,

 

1) With respect to the 2000mm tape, centred on the BMS means that there should be 1000mm of tape forward of the BMS and 1000mm aft of the BMS. I only mention this because your photos do not indicate that.

 

2) Not the radius theory.

 

Interesting fact: If my maths is correct, the minimum possible girth at the BMS is 1126.2mm, so the 1m tape can never reach the sheerline. This means it will always be possible to flare at least 63mm of the topsides below the sponson line.

I know the 2m tape is not bifurcated in the pics, but since the model was only IC like (and had a big hole in the middle) I figured it got the idea across.

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Amati,

 

1) With respect to the 2000mm tape, centred on the BMS means that there should be 1000mm of tape forward of the BMS and 1000mm aft of the BMS. I only mention this because your photos do not indicate that.

 

2) Not the radius theory.

 

Interesting fact: If my maths is correct, the minimum possible girth at the BMS is 1126.2mm, so the 1m tape can never reach the sheerline. This means it will always be possible to flare at least 63mm of the topsides below the sponson line.

I only included the radius theory because the word 'sweep' implies radius. If the radius theory were correct, you might not need the 1 m tape? But then deck stuff might be inconvenient to the rule, but damn, the resulting aesthetics would be sleeeeeek! Quite rightly!

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Using vertical and horizontal planes as measuring lines would produce problems. For one thing a tape on the hull surface will not follow one of these lines, but a geodesic, that is the shortest lines between the end points. Better to define any measurements by the hull surface. As I see it there are two choices, either define the angle between the BMS and the two metre tape ( I would suggest 90 degrees) or have the tape lying such that its end points are both the same distance from the keel line, as measured across the hull surface. The two could give different results, depending on the hull shape. As the IC is long and thin the differences are likely to be small, and is unlikely to affect much, unless flairs start fairly low down.

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As I understand it, the biggest concern is too skinny a hull?

 

So, the 1 m tape defines the 'fair hull' zone, which means the 'fair hull zone' extends up the side of hull, if the beam is 30".

 

Kind of like this? I think this is the minimum possible skinny hull in planform view (the beam needs a 4" radius, but I'm too lazy to include it, but assume it's there...). I'm arbitrarily setting the max beam position.

 

post-906-0-85237700-1391621211_thumb.jpg

 

And the other end of this is that at max beam, the fair hull zone is a plate at the bottom of the hull because the 1 m tape doesn't make it to 44"? Or 20.1" for that matter?

 

So the fair hull area measured by the 2 m tape ends when it reaches the limits of the theoretical minimum hull for each beam since it only measures fair hull area parallel to the centerline?

 

In reduction is absurdity, perhaps-

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Measurement Diagram II.pdf

 

I try again.

This is all intended to make sure people build boats that are REALLY 750 wide and not 600 wide with 75mm bumps on each side to make them measure in.

 

I don't know what your "shoes" accomplish except adding wetted surface without providing any buoyancy. As such they seem like a bad idea, and I'm not sure what the point of all this is.

Are you just trying to be difficult?

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Are you just trying to be difficult?

 

Are you just trying to be rude? The guys ideas are a bit off field but isn't that what its all about?

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As I understand it, the biggest concern is too skinny a hull?

 

So, the 1 m tape defines the 'fair hull' zone, which means the 'fair hull zone' extends up the side of hull, if the beam is 30".

 

Kind of like this? I think this is the minimum possible skinny hull in planform view (the beam needs a 4" radius, but I'm too lazy to include it, but assume it's there...). I'm arbitrarily setting the max beam position.

 

attachicon.gifimage.jpg

 

And the other end of this is that at max beam, the fair hull zone is a plate at the bottom of the hull because the 1 m tape doesn't make it to 44"? Or 20.1" for that matter?

 

So the fair hull area measured by the 2 m tape ends when it reaches the limits of the theoretical minimum hull for each beam since it only measures fair hull area parallel to the centerline?

 

In reduction is absurdity, perhaps-

The reason for the tapes is to try and have a min beam that is adhered to, rather than the measurement bumps that some other classes have ended up with in the past. Its just a set of rules so we end up with boats similar enough to race against and that look a bit like canoes. :)

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Interesting fact: If my maths is correct, the minimum possible girth at the BMS is 1126.2mm, so the 1m tape can never reach the sheerline. This means it will always be possible to flare at least 63mm of the topsides below the sponson line.

 

I think you're right about the tape not reaching the sheerline, but I think that the 2m lengthways tape prevents flares that involve any reverse curvature within that region.

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Are you just trying to be difficult?

 

Are you just trying to be rude? The guys ideas are a bit off field but isn't that what its all about?

No I'm not.

But there is a limit to attempting to apply a simple and fairly self explanatory rule to every conceivable permutation of shape.

Many of which seem to have been thought up just to see if he can frustrate the rule, even if they are silly, complicated, impossible to sail, slow and ugly.

I have been corresponding with Paul for a number of years and embrace his enthusiasm.

I appreciate his willingness to experiment, but I also think know him well enough to say "Dude, that's a really bad idea, get a bit more normal."

SHC

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Well said Sir Clark, hope to finally meet you and your clan at worlds, thx for all the good times I've had sailing a canoe.

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attachicon.gifMeasurement Diagram II.pdf

 

I try again.

This is all intended to make sure people build boats that are REALLY 750 wide and not 600 wide with 75mm bumps on each side to make them measure in.

 

I don't know what your "shoes" accomplish except adding wetted surface without providing any buoyancy. As such they seem like a bad idea, and I'm not sure what the point of all this is.

Are you just trying to be difficult?

No. This is one amazingly difficult undertaking. I can see where I look difficult. But it's difficult to design a hull when things are, uh, fuzzy? The more I think on it, the more difficult it seems, without dictating dimensions on the wider hulls. Like minimum bow and stern heights, minimum BMS draft and freeboard. It would be a lot easier to just eyeball for bumps n stuff. I was trying with the last drawing to visualize the skinniest hull possible without bumps. Granted it has a prismatic coefficient of 38 or something, and spears for a bow and stern.

 

The wings, on the positive side, if they deliver some planing lift for an IC hull, do it without much weight of displacement. They do give the Phantom 377 way better planing than a pin tail. At displacement speeds, they don't develop the same type of wave drag that slow transomed hulls. I thought I posted the YouTube that showed all this. Granted there is a wetted surface penalty, but unless someone tries it, how would anyone know if it works? And depending on how the 2m tape measurement works, even with wings, I can get the Wetted Surface down to ~35 sq ft (hull level, and down to ~ 25 sq ft at 20 degrees heel. Wave drag is a bit more under control with the wings vs no wings, at least up to 6.3 knots. So it's an attempt at getting the hull to work more optimally at both low and higher SLR's. Blunted has said more than a few times that you convinced him that a hull needs to be about 4:1 L/B to get true planing. A 44" beam IC board with a Maas style tail is massive. This is a way to reduce some of that massiveness.

 

Frankly, I'm happy with the 1m tape sliding fore and aft to the longitudinal extremes of the 2 m tape, as long as my wings, which are an extension of the bottom of the hull aren't illegal just because they're wings. On the drawing I posted of the wings, if you stretch the centered 1 m tape up and down the 2m tape at centerline, the end of the 1 m tape never touches the external chines holding the bottom of the hull /wings in place. It just goes out, wraps around the edge of the wing, and goes back to the hull. No hollows.

 

I just want to know where the end of the 2 m tape goes when the tape runs out of hull. If the tape stops measuring when it runs out of hull, like a chine, I'm fine with that. I don't understand why buttock lines turn into water lines. They might run parallel, but they're still buttock lines, and they will show bumps and hollows clearly in those dimensions.

 

If wings are illegal, just say so. There are other ways to go.

 

Hey Dave- you'll never guess what outfield position I played! And we keep Amati at San Juan Island Wa.- 60% left handed folk! (Me too. :) )

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Seems to me really your 'wings' are just extreme tumblehome. As such, if they fall within a metre of bms then any kind of concavity will be prohibited. I think that's a good way to think of the rule, no concavity q1m each side of Bms.

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Thanks for posting that diagram Steve. I see that the 2000mm tape becomes parallel to the gunwale as it reaches it. This would be important for boats like mine that have a flair within the tape's reach that supports the seat track and chainplates. Or for boats with a rub rail, right? Otherwise if the tape were kept parallel to the waterlines it would detect a hollow. Unless the gunwale was also parallel to the waterlines.

 

Or am I missing something in the rules that places rub rails or flair above the reach of the 2000mm tape? Like that the tape stops traveling up the hull when it reaches the end of the 1000mm tape. That would be fine with me.

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Hi All, now that I have spent two weeks going through this entire 30 page thread, it's time to ask some questions...

 

In the 2009 rules, the max beam was increased from the Nethercott beam to 1100mm (am I correct?)

 

I understand all the other changes, can I ask what the rationale for increasing the beam was? Was it just to give more options?

 

I also acknowledge that the new skinny hulls are obviously faster, based on the 30 pages this thread is now at, but has anyone built a new rules hull with a beam greater than a Nethercott?

 

There is some motive to my questions here, as I am sure will unfold, but does anyone consider there could be a place for a wider hull?

 

For what it is worth, I am the new owner of PhilS's Aus 21 Hollow Log. Amazing boat, min beam and light, and faster than anything I have sailed before. I really appreciate the elegantly simple rig. I have been out to the end of the plank and it was the most fun I have had on a sailing dinghy, without question. I haven't sailed a Nethercott before, but I was doing ok on the Log on the West Coast of Aus in flat water and steady breeze. Not great, but ok… I am finding it much tougher on the Lake where I live now, inland, small and oddly shaped and very flukey shifting wind. I will persevere, but it is significantly harder on the lake than with the steady sea breeze on flat water. Does anyone from the IC community think there could be a place here for a lightweight max beam boat for conditions like here on the lake? There is something that I really like about the development nature of the IC and the possibility of building a boat myself that means I am not interested in an easier class,

 

thoughts?

 

Wow. I saw the silhouette of a sail a few days ago at the other end of Lake Barely Rippling and thought "wonder what that is, it looks like the Log's sail outline but she's in WA".

 

The ACT, possibly the worst city in Oz to sail a Canoe in, now has three boats with another up the road. Mine won't be on the water this season, though, and will never have decent sails.

 

I'm planning to sail the Nethercott as a "semi AC" (not fully converted which would require too much work) so my vote is that Canoes are practical here. I used to sail my Nethercott up the Parra River in Sydney in similar conditions to those of the lake. I tjhink you have to be very aggressive in your sailing in some ways in such conditions; moving around the plank very quickly and using apparent wind to keep everything upright, but it's workable. Of course, the Nethercott is more stable in terms of hull form but old ones like mine with dacron/tin rigs may not be much more stable at high heel angles than the Log.

 

Without having sailed the Log, my 1 cent's worth would be to keep at min beam and work at practising and maybe reducing rig weight and increasing seat buoyancy and dynamic lift for the very fluky stuff we get.

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One question that's a bit off topic, but given the brains on this thread it's a good place to ask; does anyone know where there are any plans or building guides for a fairly quick and dirty sliding seat/plank? The boat is basically a museum piece so a complicated lightweight one is not necessary nor possible with the facilities and skill I have.

 

I suppose the other option to get the boat back on the water is a trap, but that has issues and then it's no longer an IC.

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One question that's a bit off topic, but given the brains on this thread it's a good place to ask; does anyone know where there are any plans or building guides for a fairly quick and dirty sliding seat/plank? The boat is basically a museum piece so a complicated lightweight one is not necessary nor possible with the facilities and skill I have.

 

I suppose the other option to get the boat back on the water is a trap, but that has issues and then it's no longer an IC.

Chris,

 

I've got an old plank and carriage you can have if you want. It's heavy, but solid and servicable. Needs hiking staps and i imagine the carriage may ned to be modified to suit your boat. But hey, it's free!

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One question that's a bit off topic, but given the brains on this thread it's a good place to ask; does anyone know where there are any plans or building guides for a fairly quick and dirty sliding seat/plank? The boat is basically a museum piece so a complicated lightweight one is not necessary nor possible with the facilities and skill I have.

 

I suppose the other option to get the boat back on the water is a trap, but that has issues and then it's no longer an IC.

Chris,

 

I've got an old plank and carriage you can have if you want. It's heavy, but solid and servicable. Needs hiking staps and i imagine the carriage may ned to be modified to suit your boat. But hey, it's free!

 

Outstanding offer!

 

Many thanks - I'm doing Lasers for the next fortnight (the Masters nats are on soon) but can pick it up soon after. The boat needs a full strip back and some minor work but not having to build a plank will make a huge difference to getting it back on the water.

 

Sounds like we may have to get the Canoes in the ACT and southern NSW together next year. I imagine that the Nethercotts will be pretty competitive against the modern boats in the fluky stuff we sail in.

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Chris,

 

Great to hear that you are getting your IC back together. Just let me know when you want to pick up the plank.

 

Not so sure about your last statement. I've been soundly trounced by the Log in light stuff!

 

Mal.

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Hi Chris

 

We had 4 IC's there for the ACT champs two years ago and with Stefan there now and your boat un-retireing, we might have to organize it again. I seem to remember there was a clash of some sort this year?

 

Geoff

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I am also a bit surprised by the sliding tape. Reading the rules I can not find a passage mentioning the longitudinal tape sliding sideways. For me BMS is a single point on the keel line.

d)
The canoe must have a minimum beam of 750mm.
Beam shall be measured at a Beam Measurement
Station (BMS) located between 1300mm and 2600mm
forward of the stern. At BMS, nowhere between the
heights of 100mm and 275 mm above the keel shall the
outside of the hull skin be less than 750mm in beam.
e)
A 2000 mm tape centered on BMS and pulled tight
fore and aft against the outside skin of the hull, shall
bridge no hollow in excess of 1mm in depth. A 1000 mm
tape centered on the keel at BMS and pulled tight
transversely against the outside skin of the hull, shall
bridge no hollow in excess of 1mm in depth.
 

So that is a point that may need to see some revision in the rules.

 

I expect the boats from my mould to fit in the rules, but I did not take that way of measurement into account when designing the boat.

 

Arne

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I am also a bit surprised by the sliding tape

Me too. I think its a red herring. The lengthways 2m tape establishes a zone each side of Bms where the surface must be without hollows, but the 1m tape is just at the one point. I am bemused and yes a bit frustrated by the way this thread has been going because we seem to have pushed enormous complication into what I thought was a simple and straightforward rule.

I still think the rule is basically fine, but we may need a little clarification on how the lengthways tape should be oriented when on the topsides and the skin is broadly vertical. Possibly best taken off line.

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For me BMS is a single point on the keel line.

 

Arne,

 

My interpretation: the BMS is just a transverse plane. "Centred on the BMS" simply means that the midpoint of the tape sits somewhere on the BMS plane. Because the tape also has to lie on the hull surface to check for hollows, by inference, the midpoint of the tape is constrained to the BMS/hull surface intersection line. In order to constrain the tape to a point, the rules would have to stipulate a third plane or surface to form that intersection point, but they don't, so the tape can be slid sideways to measure for hollows anywhere across the hull as far as the sheerline.

 

Mal.

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Anglo Steve, What do you mean by a lightweight Nethercot? Same hull shape but just lighter? Or hull depths reduced to reduce the displacement?

It was a standard Nethercott AC but built deliberately underweight as an experiment and with a dispensation from the committee. GBR316 Jet now owned by James Coxon was 75Kg with full AC kit. Never really had much of a chance to do any proper testing with her to see what she was like in a controlled set of conditions but she certainly isn't slow. The weight saving was only 20% but at least gave an indication of the effect on displacement. The conclusion is that it would probably make a difference to the small guys in the light stuff but for the +80Kg helms the difference would be negligible. The difference between other Nethercotts wasn't noticeable in racing for the limited time I used her in anger.

 

However when I then built the first M2, jumping between them demonstrated Jim's theory of the bulbous shape under the mid-ships area mast creating a lot of drag and it became very noticeable. You can hear the difference with the water being pushed aside which you just don't get with the slim designs. It is also apparent that this rounded shape of the Nethercott is also what gives the boat stability and is the trade off you get when going to the narrower more easily driven hull form. This is the main reason the new boats accelerate more quickly in my view.

 

Steve

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I am also a bit surprised by the sliding tape. Reading the rules I can not find a passage mentioning the longitudinal tape sliding sideways. For me BMS is a single point on the keel line.

 

 

I expect the boats from my mould to fit in the rules, but I did not take that way of measurement into account when designing the boat.

 

Arne

Arne

 

Quite - we are discussing this with UK Measurer to make sure there are no nasty surprises at the worlds. I did check the M2 and as it happens this doesn't cause a problem but we need to produce a definitive measurement procedure in light of this and look again at the wording of the rules.

 

Steve

 

 

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Steve (USA) thanks for the diagram, I liked Chris Maas interpretation. and seems a very reasonable way to proceed, even though its different to the two methods I put forward. I entirely agree that the simpler the rules the better, but part company with you about the "limit to attempting to apply a simple and fairly self explanatory rule to every conceivable permutation of shape". Firstly it is self evident from the number of contributions to this thread that what to you is "self explanatory" is far from that to others. Your short description of the aim ie " This is all intended to make sure people build boats that are REALLY 750 wide and not 600 wide with 75mm bumps on each side to make them measure in " makes so much more sense than the rule itself. A problem, I see, is that unless one is in the class it may opaque as to what the rule is trying to outlaw. Bumps are one obvious thing but what about wings as on Tin Teardrop. See Pic below Obviously, I, know that TT was legal but that may not be the case for other prospective designers who may never have seen the Tin Teardrop.

Your comment about designs, "Many of which seem to have been thought up just to see if he can frustrate the rule, even if they are silly, complicated, impossible to sail, slow and ugly." seems unnecessary. As the canoe is a development class we can expect variation. I think you really mean frustrate the rule MAKERS, not the rule. Anyway does it matter if someone creates a slow ugly boat? If its slow it will be so far behind you in the races that you will not see it and so its ugliness will not matter. If it is impossible to sail then it will not even be on the water. I have seen some ugly canoes which I would not sail, but as they say beauty is in the eye of the beholder, so with ugliness. I would never tell someone their canoe was ugly, it is simply rude. The only criterion is does it fit the rules?

 

cqy6.jpg

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Thanks Anglo Steve for the post. It is all good information, but perhaps only to be expected. reduction in wetted area of a underweight Nethercot should improve light weather performance. where as the wave drag will be less affected as it depends on the hull shape which is not changed. I would agree that the extra drag is probably due to what I would describe as the rocker which will be greater in the nethercot and less fine bow waterline. Acceleration is proportional to net force and inversely to mass. Reduction in mass will result in probably 25% more acceleration, assuming DC displacement is about 0.8 times Nethercot displacement. Added to that the reduction in drag to give better accn.

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My intent when writing the rule was to prevent the type of mishigas that plagues all of section rules in the box classes.

There is a tale of someone sailed a 14 with a nail sticking out of the side to satisfy a measurement point. Look at the distortion of this otherwise attractive NS14 hull in order to meet a measurement point, and you see what I mean.
2008-01-17_112949_tequila99.jpg

So the idea was: By insisting that the hull be at least 750 wide from 100-285 above the keel, there could be no scooped out topsides to cheat the rule by having a boat that was wide enough at two heights but no where else. A 1 meter wide tape laid across the hull would identify any hollows in the section shape between the keel and the 100mm waterline. If this were somehow a bump for measurement purposes, there would be hollows fore and aft of it, and the 2 meter tape would catch those. I intended the 2 meter tape to be a test of the hull surface only, and not to be applied around the gunwales. I envisioned it being applied about like a long board when fairing a hull, that is to say more or less aligned with the fore and aft shape and not at some oddball angle to try to catch people out. The tape would more or less follow any taper in the topsides and ignore any rubbing strips or gunwale features because it was a test of hull fairness.

 

I did not intend that the hull had to have a minimum 1 meter wide surface 1 meter either side of the Beam Measurement Station, But I also didn't mean that there couldn't be any flare or spray rails.

 

A tape was chosen because it relieved us of the necessity of specifying the stiffness of a spline or batten. A batten would not make a sharp turn around a chine, so it seemed like a good choice. But it leaves the option of 180 degree turn as Amanti envisions.

 

 

It seems this intent is not conveyed adequately. At present, I don't know of any design that has it wrong. The spray rails on the Morrison 2 are ( I believe) above the limits of the 1 meter tape, and Tin Teardrop's sponsons were also above the critical height. Neither boat was or is unattractive, or seems to be taking advantage of a loophole to measure something that doesn't fit the intent of he rule. Amanti's vision is more extreme and a bigger challenge to the rule. It is a permutation I never though of, and so didn't put specifics in place to deal with it one way or the other. I don't think it is going to work very well, but I guess that doesn't relieve he class of the responsibility of determining if it conforms to the rule.

SHC

SHC

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Thanks Steve. We all know that you are trying to do the best for the class as you have for many years, and we are all very grateful for that. I do think that your last few posts have been so useful and clarifying that it might be helpful to have them included in the rules. Maybe as a Frequently Answer Questions section as an addendum. Would then free us all from having to revisit these question again (and again). I take your point about using a nail being used to satisfy the rules, and yes the boat in the photo is not the prettiest, but that is only a personal view. (Even though we both agree on it).

 

I think your choice of tape rather than batten/spline was very sensible. It would otherwise be difficult to produce a chined boat. Incidentally Amati's tape fixed at the keel on the BMS and rotated would pick up all hollows within the span of the tape.

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and yes the boat in the photo is not the prettiest, but that is only a personal view. (Even though we both agree on it).

 

To me there is no point in having a rule that can be evaded. The trouble is that there are very often folk who relish the challenge of beating the rule writers rather than beating the other boat designers within the rules. The trouble with that as a competition is that whilst the rule evaders might be enjoying their side of the competition, rule writing is rather difficult and not IME very much fun, so that sort of competition isn't much appreciated by the rule writers. Its also rather hard on the rest of the class who want to have a sailing and design competition, not a rule phrasing one.

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Jim C, you say "To me there is no point in having a rule that can be evaded. "

 

Entirely agree. That is why rules should be clear. It may not sound it, but I do appreciate the work Steve has and indeed does put in, AND I would like to ensure that there is a point to the rules, so that his work is not wasted. Having said that I think it a little disingenuous to suggest that people try and beat the rule writers for the sake of beating the rule writers. I believe they have ideas which they think will make their boat faster and try to see how those ideas can be developed WITHIN the rules. There is no point in building a boat if it doesn't comply with the rule, neither is there any point if it ends up slower than other boats in the fleet. At least I cannot see how beating the rule makers but producing a slower boat would be any pleasure. If however the design ideas prove faster then it may benefit the fleet to have the ideas tested. It can always be outlawed later anyway.

 

The canoe fleet, in the UK at least has a long history of dispensations and rule changes to outlaw unpopular practices. Sliding seat was outlawed in the UK rules sometime just after the start of the twentieth century, reading between the lines of history this was largely because Baden Powell didn't like them, and was looking for a more substantial boat because of his age. Linton Hope's Tritonelle with the first chined stern, so successful it gave up racing, but also the cause of the minimum radius rules being introduced (B Class). Uffa Fox's Mederka, Rannoch and their sister boat didn't measure and had to have bumps added. I think I remember dispensations occurring in the 1980 as well but I could be wrong. Of these Tritonelle was trying new ideas that took 35 years to become incorporates into the rules. Mederka/Rannoch were I think built without much regard for the rules, or certainly with insufficient care in checking the boats fitted within the rules. Uffa Fox's Valiant and East Anglian designed to two rules so pushed the envelope in many ways, achieved a unified Anglo-American rule, demonstrating the pushing the envelope can achieve beneficial results.

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a little disingenuous to suggest that people try and beat the rule writers for the sake of beating the rule writers.

Well, to attempt to make it a bit clearer what I mean, lets look again at the NS hull above with the bumps. That boat does not have the rise of floor and static stability that the rule was intended to mandate. No doubt that boat is faster than a boat that met the measurements without the lumps and bumps, but it is partly so because it evades those rules, not because its a superior intrinsic shape. Whilst I am prepared to admire the design skill that means that a boat with that many lumps and bumps still works, I'd be much happier if the rules could have been framed to prohibit them. Its a question of level playing field for designers, and to my mind whilst its always admirable to produce a faster boat, its less admirable to do so by outsmarting the rule writers rather than outsmarting your fellow designers.

 

Of course its all to easy to make a little error when building a boat and find out it doesn't measure, and I don't know whether the Mederka/Storm Petrel/Rannoch trio had measurement problems because Uffa was being careless or because he was pushing the rules too hard... Careless is surprisingly easy: my rebuilt Nethercott doesn't meet the one design rules in one respect (foredeck 2mm too high) and was right on the limit with another (gunwhale rubbing strip *by complete coincidence* right on the maximum), because I had foolishly never studied the one design rules properly, only the new development rules, and it hadn't occurred to me that those things might be restricted... If the gunwhale rubbing strip hadn't had that last pass through the thicknesser...

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So in my painful swelling brain, this what I think I understand-

 

the BMS 1 m tape will be set (and frozen I guess)on the outside of the hull surface

 

The 30" by 11" (or 7"?) athwartship rectangle is established at that point

 

Then the 2 meter tape, centered on the 1 m BMS tape, will slide away from the centerline, staying on the 1 m BMS tape on the surface of the bottom of the hull?

 

When the 2 m tape reaches the end of the 1 m BMS tape, it stops sliding?

 

Does the 2 m tape stay parallel to anything- like the centerline? Or the gunwale? Or the waterline? (Maybe this can be nominated?)

 

Where the hull stops relative to the 2m tape in whatever plane (don't know what else to call it ) it is, what happens then? Maybe the 1 m tape is a tape, and the 2m tape is a stiff batten?

 

Maybe a rotating tape is in principle a good idea- But how long would it be? (2 ways to take that!) It could be used as a quick way to establish whether there are any hollows, and then the more formal method (above) used to investigate formally. (Measurers will be required to wear formal evening wear.) (now that would add to the legend of the class :) )

 

Anyway, just some (probably not perfect) ideas. I just spent 2 hours banging away at this and went through a ton of stuff I poked holes through....

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.

amati when did you sail an IC last

 

was there any breeze?

Yes

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So if the hull is flared at the BMS above the 1m tape end point, does the flared section have to remain above the 1m tape girth point for the extent of the 2m tape? If the flare was to start almost exactly at the end of the end of the 1m tape at the BMS, it would be easy to contravene this as shown in AndrewE's sketch in post no #3043. And perhaps it doesn't matter if the flare or spray chine drops down away from the BMS, but it is definitely not clear in the rule.

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Well in summary, the test being what it is may well be flawed and may need better definition but is down to the National measurers to act as the conduit for any interpretation which may be necessary. The fundamental point is that the boat should be designed to be within the spirit of the rules and that is that the hull should be fair and should not have bumps within 1m of the BMS. Pretty simple really which is clearly what Steve and now the national classes have intended. If anyone designs a hull which attempts to push the boundaries of the rules they should first speak to their national measurer and seek advice as to whether or not their proposed design is likely to create a problem within the interpretation of the rules. If they then proceed against current thinking and advice and the resulting design shows a clear advantage on the water in results, they will then need to demonstrate to the class that the spirit of the rules have been met and it's in the interest of the class globally to allow such an interpretation. If not the class reserves the right to not allow it to race as an IC.

 

I'm happy from our point of view that the current views expressed here do not create any issues with boats built so far but the national measurers should have a private discussion I feel through the national associations to agree on the precise method of measurement that will be used at the worlds this year and distribute this in advance as a housekeeping exercise. Further developments is a different issue, we just need to tie down what is acceptable so designers have a more precise set of instructions beyond current interpretations.

 

The main message we want to put out to anyone looking at this forum who may be wishing to buy a boat is that this is not a problem just an administration exercise which needs to be sorted out now that numbers are growing very quickly. We are just putting controls in place to ensure that future IC designs and the development progresses in a balanced way to ensure we are the fastest and most exciting boat of its type but maintaining the values and core features which makes canoe sailing so damn good....

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JimC you say "Well, to attempt to make it a bit clearer what I mean, lets look again at the NS hull above with the bumps. That boat does not have the rise of floor and static stability that the rule was intended to mandate. No doubt that boat is faster than a boat that met the measurements without the lumps and bumps, but it is partly so because it evades those rules, not because its a superior intrinsic shape."

 

Perhaps I an being very stupid, but if the rule maker wanted to mandate stability and rise of floor, then why did he mandate something totally different? Seems to me the solution was very simple. It was clearly the fault of the rule writer for specifying something he didn't want in place of something he did want!

 

Evasion usually implies breaking the rules, but if it didn't break any rules and measured OK when tested against the rules then it evaded nothing.

 

As for "superior intrinsic shape". What does that mean? If it is faster then it must be of intrinsically superior shape. I am assuming that going around a course faster is what we think of a superior. If not why do we give Cups to the winners? I thought it was because we considered them as superior sailors!

 

 

Anglo Steve you say "The fundamental point is that the boat should be designed to be within the spirit of the rules and that is that the hull should be fair and should not have bumps within 1m of the BMS".

 

It seemed to me that the rule could be used to outlaw things other than bumps and hollows, which was my starting point. Personally I do not like the "Spirit of the Rules" clause. Even though I have been it the class a long time and think I know what it means. It is most unhelpful to newcomers to the fleet, unless of course they have the Psychic power to know what is in the mind of the rule writers.

 

It is apparent that in many instances what is written as rules is measurement method. In the case of the NS dinghy if the rule had been written in terms of stability and rise of floor and the measurement method to ensure this given as a separate clause then the supposed "evasion" could not have taken place. Even if the measurement method was satisfied the rule would not have been and the hull could have been rejected on those grounds. Wording such as "normally measured by... " would allow variations in the event of doubt.

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Andrew:
A skinnier hull is almost always faster than a fat hull.

I assume that's what Jim means by " intrinsically faster" and what has been seen over the years that narrow hulls that have been selectively bumped or distorted to meet the minimum dimensions at a single point have proven faster than hulls that are fair through that point. Most of the anti bump rules simply provide the box rule for the bump, and don't enforce the fundamental intent of assuring that the boat has a certain limited minimum beam.

My apparently flawed attempt to avoid this mishigas was to require that the minimum beam not be measured solely at two heights ( which is typical of the I14 and other development rules, but was over a vertical distance of 100-275mm. This eliminates the hollowing of the hull beyond minimum beam in the topsides.

The 1 meter tape test was to assure that the section shape was not hollowed in between the 0-100 mm heights, This prevents tunnel hulls (to your point and intentionally so) , and also prevents one from narrowing the waterline below the 100mm height to gain a skinnier water plane. This is almost enough, but it is still possible to distort a narrower than legal hull form into compliance if there can be concavities fore and aft of the measurement station. So we applied the 2 meter tape rule to regulate this.

Crafting verbage that defines exactly how the tape is laid on the hull is extraordinarily difficult because every specificity invites an exemption.

 

For example,

You establish two section +/- 1 meter from BMS. You divide the girth of these sections by 10 and measure between those points. You have just opened a can of worms, because Juan will identify where those lines are and will construct the hull such that the surface will satisfy the tape at those points but no where else if he can get a skinnier and thus faster result.

 

So a bit of vagueness in service of a broad intent is appropriate. One tries to encourage experimentation while engaging in a certain amount of type forming. These are supposed to be sailing canoes consistent with the long tradition of sailing canoes, one doesn't foresee every permutation, and one cannot fairly incorporate all theories worth experimenting with in a single class.

SHC

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Rule writing is extraordinarily difficult, far more so than one would believe, and there are a number of factors that need to be considered. Amongst the prime ones are repeatability and practicality: it needs to be possible to do reliable rule checks in an ordinary dinghy park with a minimal amount of equipment, and it needs to be possible for the average boat builder to guarantee that the boat he/she builds will meet the rule. Traditionally rise of floor type rules have been used to ensure there is a certain amount of structure in the boat low down, with, as I've always understood it, with a view to providing a minimum of stability and buoyancy. Maybe there's a better way of doing that, in which case it would be interesting to hear ideas that meet all the other criteria. Like the design of the boat itself, the design of the rules is always a compromise between conflicting requirements. For interest, I had a shot at writing a rise of floor rule when I did my one off singlehander some years before the new IC rule, and this is the text I came up with:

 

Rise of floor shall be measured with an inverted U shaped gauge. The two legs shall be 900mm apart and 100mm long. A line shall be marked exactly between the two legs of the U. This establishes a rise of floor of 100mm at a point 450mm each side of the centreline. The gauge shall be run along the boat from the bow until a point is reached where both legs are in contact with the hull of the boat and the centre mark is in contact with the centreline of the keel. This point shall be marked as point A. The gauge shall then be run along the hull until the centre mark is no longer touching the hull or the end of the hull is reached. This point shall be marked as point B. The distance between point A and point B shall be at least 1.2m. If bumps or distortions exist that in the measurer's opinion exist solely or primarily to affect these measurements then the measurer should estimate where the measurement points would have come without those distortions and mark points A and B appropriately.

 

I think the Canoe rule is better in almost all respects, most particularly because its much more precise about lumps and bumps. I thought at the time, and still think, that the 1m and 2m tape thing was a pretty clever solution. Anyway the key thing about both is that, unlike older rise of floor rules, neither nominates a fixed position for the measurement, they both let the designer position the maximum fullness of the hull where they like. Older rise of floor rules were almost always taken at mid length, which really promoted distortion since the measurement point is not where the max beam is wanted.

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Steve, Thanks for your clarification. I was fully aware of what Jim C was driving at. I was saying that there are alternative descriptions. To clarify

 

Jim's description - " hull, narrower than allowed, with bumps added"

alternative description - " boat, wide enough to be allowed, with hollows scooped out"

For Jims description starting with a narrow hull implies cheating, but the alternative does not necessarily imply it, and as both descriptions produce the same result, which one is used is irrelevant if the hull fits the rule.

I don't think that I can add more to what I have already said.

 

To recap my position: I felt the rule was unclear in one particular aspect, that of measurement of flairs on the hull. It has always been clear to me that it achieves your objectives to outlaw hollows and bumps, and indeed need no additional verbage. I agree with Jim that it is a nice simple to applied method which is likely to work well, even in a dinghy park, for the purpose intended.

 

On reading the rule initially, 2009? or thereabouts, I was unsure about what was being outlawed because I could see hollows and bumps on boats which had been measured as in class, and remember that we had this same discussion around that time. I probably made the same points as I have made in this discussion.

 

I was reluctant to re-join the discussion this time but it seemed to me that others were also experiencing difficulty with the rule and so the problem was not with me but the problem was with the rule, and felt that I should help draw this to the attention of the rule writers. Many of the problems mentioned in this recent discussion were things other than I expected or saw as problems and, I think, not discussed last time, which demonstrates the range of interpretations available, for this reason I also agree with Jim that writing rules is a difficult business. Clarifying the rule, especially as to intent and exceptions requiring one sentence at most, could well avoid having this discussion again at some future time.

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By my count there have been at least fifteen different designs built to the new rule. None of them are even remotely distorted below the gunwale. My first boat, String Theory, and Andy's Tin Teardrop are the most radical as far as wing type flairs go and on S T they were slow.

 

The new rule has been remarkably successful at encouraging fast, sailable shapes. It would be a good idea to add to the rules a little clarity about the method of measurement though.

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A few months ago for my own amusement I tried to develop a Velocity Prediction Programme. When Jim C posted his speed round the course data a few days ago I added it to the Polar plot, which is shown below for your entertainment. The calculations used drag data from the Added Mass theory, Which I have mentioned previously. Values assumed for aerodynamic lift and drag, are from Larsson ( Principles of Yacht Design ) and by Fossati ( Aero-Hydrodynamics and the performance of sailing yachts ). I also assumed that the canoe was sailed flat Robin Wood style, and there was a maximum heeling moment which could be balanced. If the aerodynamics gave a higher value for the heeling moment than the max possible then the maximum, determined by the crew weight and lever arm, was used. This limited the drive force, which is why the upwind speed curves all merge. No heeling was considered, even though most of us sail upwind with some. Jims data is shown in red, The Predictions for the Nethercot as dashed lines, for the four wind speeds indicated, and the solid line for String Theory, again at the speeds indicated. Any feedback would be much appreciated.

 

4cgv.jpg

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A few months ago for my own amusement I tried to develop a Velocity Prediction Programme. When Jim C posted his speed round the course data a few days ago I added it to the Polar plot, which is shown below for your entertainment. The calculations used drag data from the Added Mass theory, Which I have mentioned previously. Values assumed for aerodynamic lift and drag, are from Larsson ( Principles of Yacht Design ) and by Fossati ( Aero-Hydrodynamics and the performance of sailing yachts ). I also assumed that the canoe was sailed flat Robin Wood style, and there was a maximum heeling moment which could be balanced. If the aerodynamics gave a higher value for the heeling moment than the max possible then the maximum, determined by the crew weight and lever arm, was used. This limited the drive force, which is why the upwind speed curves all merge. No heeling was considered, even though most of us sail upwind with some. Jims data is shown in red, The Predictions for the Nethercot as dashed lines, for the four wind speeds indicated, and the solid line for String Theory, again at the speeds indicated. Any feedback would be much appreciated.

 

4cgv.jpg

My experience is that the speed envelope generates more of an asymmetric type lobe along and below the 45 degree downwind angle when over 11/12 knots where you can generate much more apparent wind and VMG improves by sailing hotter angles and then bearing away similar to an AC. In the really windy stuff you can actually sail similar angles to an AC and keep up unless the wind drops below the 12 knot mark where the spinnaker boats pull away.

 

Steve

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Steve. Thanks for the comments. They were very much what I had thought, but I couldn't identify how a different result could come about from the drive data I had. It was also a very simplified attempt at a VPP, with lots of approximations. Having said that the drive data which the references gave seems to be lower that I expected for the downwind part of the plot. It may, of course, be that I applied their data incorrectly. More data such as that from Jim C would help things along! Are comments on the comparative performance of String Theory and the Nethercot would also be good.

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post-7672-0-21204600-1393346607_thumb.jpg

first canoe to sail out of Santa Cruz in over 10 years.

 

 

with a little over 6 months to go, sounds like there is to much talk of this and that, its time to go sailing.

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Looks good, but can you unwrap that vang strop from around the boom? You've got no leverage and I fear you'll crush the boom under load.

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All we need now is the wind speed and direction to be recorded at the same time. That would give a lot of information.

 

I am interested to know how you identify the added resistance with "noise under the mast", as opposed to some other region of the hull.

 

Wind speed and direction logging: wouldn't that be nice:-) Its technically very achievable, but the trouble is putting an expensive and probably delicate bit of hardware at the top of the mast where its so vulnerable to getting trashed.

 

go out in steady (direction) breeze. Then you've got boat direction logged on the GPS and can calculate an approximate TWA.

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6 months out from the Worlds my awesome wife tells me "you need to go the the Worlds" who am I to argue. Now to get this boat of mine ready...

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Midwinters at Buccaneer YC in Mobile AL on the weekend of march 29th by the way. Should be brilliant. Come one come all.

DRC

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Didn't happen.

3 guys from Rhode Island were the only people committed to attending. So we passed on the opportunity to drive 2500 miles to sail with ourselves. Other complications added to the inertia, like term papers due on Friday before the regatta, work schedules etcetera.

Hope to hit the water soon in RI and check out the new rags.

SHC

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Just ordered my new sails, going for an Ullmans fibre-path Main and Dacron jib.

 

Do we have any updates for the worlds? NOR or entry fees would be useful

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Del is busy getting it sorted as well as getting interrupted by my mass of emails while I'm trying to work out how to get my boat there and back...and organising a charter boat for another one of the Aussies... I'm sure it wont be long before the NOR etc is posted.

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Does anyone have a Delft ship file with the hard points the would be generous enough to share

 

Tink

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The word is the NOR and other info is being checked over by all concerned and will be posted very soon....

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nice onboard footage!

i like the first one where on the tight reach you steam past all the rest! and a catamaran too! what was that, a dart?

great boat!

the contender and the rocket were also gone quite quickly

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Photos? or it didn't happen ;)

 

 

 

North.

They look pretty cool.

SHC

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Well ladies and gentlemen its happening, the NOR and on line registration for the XIX International Canoe World Championship is now up and running.

Go to richmondyc .org and click on the link on the front page.

A couple of cleaver types have already found it and signed up!

The dates are Sept 6-14 2014 with the National Team races for the New York Challenge Cup on the 15th.

 

Del Olsen

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Errr, excuse the signature line, a failed attempt to add the event graphic and logo.

After an hour trying to delete the damn thing , I went sailing.

DWO

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All good Del!, dat's what I would've done! See all my heroes soon, 4 months only!

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After a sunny hour's boat bimbling this eve managed to shoot the following before the rain came in:

 

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Beauty!, now can you shoot one of Hell's Bell's, and with kite up!

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A sailor's gotta eat right? Use that to spear flying fish for lunch!

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