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Similar lengths. The 50's transom and bow knuckle are just kissing the water at load displacement.

The 49er, despite being about 30kg lighter, has a significant amount ( inch or two) of transom immersion at rest.

This means a lot less convex buttock curvature, so much less sinkage/squat (or sucky sucky) at level trim, which is the main cause for baulking in the hump zone at around 7kts.

 

For the 49er this comes at the expense of dragging the transom a bit even with aggress e bow down trim, in the light air, meaning that it's a bit sticky at sub 4 kts boatspeed. But the 49er spends about 2% of it's racing time at sub 4kts so it's an easy Tradeoff to take.

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Similar lengths. The 50's transom and bow knuckle are just kissing the water at load displacement.

The 49er, despite being about 30kg lighter, has a significant amount ( inch or two) of transom immersion at rest.

This means a lot less convex buttock curvature, so much less sinkage/squat (or sucky sucky) at level trim, which is the main cause for baulking in the hump zone at around 7kts.

 

For the 49er this comes at the expense of dragging the transom a bit even with aggress e bow down trim, in the light air, meaning that it's a bit sticky at sub 4 kts boatspeed. But the 49er spends about 2% of it's racing time at sub 4kts so it's an easy Tradeoff to take.

This makes much more sense than all the numbers and theories.

Its back to what we were discussing before. Less weight allows less spring and that makes faster boats with less speed hump.

The new ICs are longer, lighter and narrower than any other dinghy class and if the stern is narrow and pointy enough it does not suffer from the transom immersion problem like the 49er, even in very light airs, and/or downwind (without extra) when the canoe might be going slower.

Hence my preference for flat spring, pointy stern, but with sharp chines aft for transom like separation at high speeds.

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The new ICs are longer, lighter and narrower than any other dinghy class and if the stern is narrow and pointy enough it does not suffer from the transom immersion problem like the 49er, even in very light airs, and/or downwind (without extra) when the canoe might be going slower.

Hence my preference for flat spring, pointy stern, but with sharp chines aft for transom like separation at high speeds.

 

You are right in that the IC presents a unique opportunity to get a really straight keel line with minimal transom drag effect and low wetted surface. I tend to be in favour of the more pointy stern appoach for this reason. The sharp chined 'planing canoe' stern is a relatively unexplored area of hull design, which makes it interesting.

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Similar lengths. The 50's transom and bow knuckle are just kissing the water at load displacement.

The 49er, despite being about 30kg lighter, has a significant amount ( inch or two) of transom immersion at rest.

This means a lot less convex buttock curvature, so much less sinkage/squat (or sucky sucky) at level trim, which is the main cause for baulking in the hump zone at around 7kts.

 

For the 49er this comes at the expense of dragging the transom a bit even with aggress e bow down trim, in the light air, meaning that it's a bit sticky at sub 4 kts boatspeed. But the 49er spends about 2% of it's racing time at sub 4kts so it's an easy Tradeoff to take.

This makes much more sense than all the numbers and theories.

Its back to what we were discussing before. Less weight allows less spring and that makes faster boats with less speed hump.

 

I don't see how less spring follows from less weight. Optis have very little spring, and the hulls of cats have very little spring, regardless of the amount of weight they have.

Buttock curvature isn't really "spring" because its well aft of the midpoint.

 

The new ICs are longer, lighter and narrower than any other dinghy class and if the stern is narrow and pointy enough it does not suffer from the transom immersion problem like the 49er, even in very light airs, and/or downwind (without extra) when the canoe might be going slower.

Again, that doesn't quite make sense. Consider a narrow waterski like windsurfer or kiteboard. its pointy tail has plenty of "transom immersion" problems until "planing speed" is reached since it lacks enough floatation.

Hence my preference for flat spring, pointy stern, but with sharp chines aft for transom like separation at high speeds.

how are Hard chines aft that are immersed at slow speeds different in drag than an immersed stern?

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I don't see how less spring follows from less weight. Optis have very little spring, and the hulls of cats have very little spring, regardless of the amount of weight they have.

Buttock curvature isn't really "spring" because its well aft of the midpoint.

 

For boats of the same length, assuming you want to keep the immersion of the transom and the stem the same, lighter boats can have less spring because they displace less water.

 

 

how are Hard chines aft that are immersed at slow speeds different in drag than an immersed stern?

 

With a squared off transom, separation (including turbulent separation as opposed to total separation) occurs at very low speeds. The separation volume is large from the outset. With a curved chine line, the separation is progressive, almost zero at very low speeds, then starting at the more steeply curved areas at the tail at lowish speeds and moving forward along the chine as speed increases (depending on the actual planform shape).

 

With a canoe stern, the volume distribution can be more or less symmetrical about midships, which is good for low speed resistance, despite the immersed chine. With flow separation from the chine, the canoe stern is able to emulate an immersed transom at higher speeds without needing large changes in trim. An immersed transom hull has a truncated volume distribution curve, which is good for higher speeds but not good at low speeds. That's why with a transom hull you need to move your weight forward in light winds, to get the transom out of the water.

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To some extent it boils down to flow across the chine? Or has NASA's idea of flow management been superceeded?

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I just want me one of those fat-bottom girls. Well, as fat as a canoe gets….

 

Damn Del got me hooked dry.gif

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Similar lengths. The 50's transom and bow knuckle are just kissing the water at load displacement.

The 49er, despite being about 30kg lighter, has a significant amount ( inch or two) of transom immersion at rest.

This means a lot less convex buttock curvature, so much less sinkage/squat (or sucky sucky) at level trim, which is the main cause for baulking in the hump zone at around 7kts.

 

For the 49er this comes at the expense of dragging the transom a bit even with aggress e bow down trim, in the light air, meaning that it's a bit sticky at sub 4 kts boatspeed. But the 49er spends about 2% of it's racing time at sub 4kts so it's an easy Tradeoff to take.

This makes much more sense than all the numbers and theories.

Its back to what we were discussing before. Less weight allows less spring and that makes faster boats with less speed hump.

 

I don't see how less spring follows from less weight. Optis have very little spring, and the hulls of cats have very little spring, regardless of the amount of weight they have.

Buttock curvature isn't really "spring" because its well aft of the midpoint.

 

The new ICs are longer, lighter and narrower than any other dinghy class and if the stern is narrow and pointy enough it does not suffer from the transom immersion problem like the 49er, even in very light airs, and/or downwind (without extra) when the canoe might be going slower.

Again, that doesn't quite make sense. Consider a narrow waterski like windsurfer or kiteboard. its pointy tail has plenty of "transom immersion" problems until "planing speed" is reached since it lacks enough floatation.

Hence my preference for flat spring, pointy stern, but with sharp chines aft for transom like separation at high speeds.

how are Hard chines aft that are immersed at slow speeds different in drag than an immersed stern?

 

Nothing wrong with Mal's answers but I'll add some of my own.

Flat spring does not make a boat light but a light boat allows you to have flat spring with minimal immersion of either end. It also helps to have U shaped sections rather than V shaped sections because it means for any given diplacement the U shaped boat will float shallower than a V shaped boat as the volume is lower down. An extension of this is that the buttock lines near the centre (keel line) are very similar in shape and hence my use of flat spring also means flat buttocks. Buttocks are parallel to the centre so I do not see how you think that they vary aft of amidship differently to the keel spring, only I think on some old type double ended paddling canoes. Certainly not on any modern planing boat, (and by my earlier argument even similar light boats which by being narrow enough maybe do not even need to plane).

 

Canoe sterns of th etype I am talking about just have a turn up in the buttocks where they cut the chine lines, same as a transom boat but progressively more forward with beam. Forward of the chine turn up (to at least midships) these buttocks should be straight and parallel, thats one planing theory I agree on.

 

Most cats have much more spring than similar displ planing dinghies, especially aft of midshipe. If they do not have it they are difficult to tack and gybe. I do not consider an Opi as even being in the book on dinghy design.

 

Narrow speed type sail boards are so low on volume that the stern will sink deeply when not planing. Again not in the book on dinghy design.

 

An IC is long enough and light enough to have adequate volume with minimal spring so that the stern immersion is very shallow. Shallow enough that the hydrostatic pressure of the water passing under the boat does not fight with the shallower water passing around the side of boat, when they meet at the chine. Having a topsides which curve into a canoe stern allows the water all come together at the stern at low speed but at progressivly faster speeds the side water leaves the boat further forward, leaving the bottom water to part the chine much like it does from a transom. How far forward depends on how fast and how far aft the crew happens to be. So at slow speed the flow around the sides fills the void due to stern immersion cleanly and without turbulance, at high speeds the chines leave a clean wake like a transom with some topsides dry, all with considerably less wetted surface than a transom design. And the transition between the two is progressive, without needing crew movement and without and "humps".

 

The wake is in fact very clean, thats not just theory, I have built it and seen it. What was noticable was that it did not seem to make much differrence to speed whether I moved the seat back or not, up to the practical limit of nose dive prevention that is. On that subject I do not remember ever nose diving the Hollow Log, although I know Oliver did at least once.

 

The difference between immersed transom and immersed chines has nothing to do with planing, but as I said a few weeks ago, I believe its more about having the hull volume and hull planing surface more forward than on a transom type canoe (like Chris has made fashionalble by going so fast). Its about minimising the need to move crew weight for and aft in different conditions, (because its such a hassle to do once you are out hiking.) If the part of the boat supporting itself is further forward, and can remain there under differnt conditions, slicing or planing, then any aft movement of the crew will be less needed and more effective when its really necessary, because the moment arm between crew weight and CoB (or C of Planing area) can be greater.

 

The other more obvious advantage of canoe stern over transom stern is that in light weather when some heal is needed to set the sails, the canoe stern does not drag the lee corner of the transom deep into the water.

 

The IC is rather unique because its so long, narrow and light, comparisons to smaller, heavier or wider hulls are not often relevant.

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The IC does occupy a unique design space. Somewhere in between multihulls and skiff/ dinghies, taking some from each but also being neither. That's what makes it an interesting design challenge.

And to emphasize Chris Maas' point you don't need to be a rocket scientist to design, sail or build one of these things any more than you have to be a computer expert to use the internet or work on your car. We maintain all the necessary theoretical rabbit holes as a service to our members who may be bored with the poi of Manufactured One Designs.

 

The biggest difference between ICs and other mono hulls is their very low Displacement Length Ratio. This "more or less" defines the amplitude of the displacement wave, and as many of you will remember from your physics classes the amplitude of a wave defines the amount of energy it contains. Thinking backwards, to reduce wave making drag, you need to minimize the height of the waves you generate. ICs have a D/L of 28. This is a lot closer to an A Class Catamaran (D/L 25) than an I14 (D/L~125). Stated another way, The IC makes a shallower hole in the water to climb out of and as such almost any IC will have a relatively hump-less drag curve.

For example:

Mayhem StringTheory quarter scale.ppt

Credit: Bill Beaver.

Note that there is no appreciable change in the slope of the drag curves in between 5 and 6 knots (the theoretical hull speed of a 17' long boat.) This is no magic of shaping, it is the magic of a D/L of 28.

Mayhem is a very nice conventional canoe shape similar in most ways to the Morrison 1.

In this case "String Theory" was this 1/4 scale model I built loosely trying to build a boat like String theory using Phil's tortured ply techniques. These tests convinced me that I better build "Smoke" and "Witzelsucht" instead of continuing down the Josie path.

SHC

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Incidentally if you know what displacement (full scale) those models were towed at, I can share some semi - illuminating resistance info that I've put together.

I've assumed for now that they were run at about 290lbs in that there imperial speak.

Dan

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How about this to open another cam of worms. As my teacher used to say "Please comment, elaborate and expand"...

 

http://www.newscientist.com/blogs/nstv/2012/01/physics-in-a-minute-how-wings-really-create-lift.html

Yes, most aerodymaic theories of flight rely on the air being compressed or expanded and hence changing density and pressure, so that the bottom pressure is greater than the upper pressure, causing lift. All believable until you put a foil into incompressible fluids like water. So according to most theories hydrofoil sailing is impossible. Another reason why I do not like most sailing theories. QED.

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Lift comes down to f=ma.

 

Populist explanations such as "curved surfaces" are just that. The cause of lift is not molecules judging whether a surface is curved or not, or whether a shape is symmetrical or not.

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Lift comes down to f=ma.

 

Populist explanations such as "curved surfaces" are just that. The cause of lift is not molecules judging whether a surface is curved or not, or whether a shape is symmetrical or not.

So then why does a flat plate generate "lift"? Because in snipes it does (I know the answer, I'm just pointing out that this isn't quite accurate)

 

Note also that Bernoulli's equations about "pressure" around a curved surface don't actually rely on "compressibility" A better way to think about it is that on the side the molecules are streaming past faster, fewer of them are engaged in browninan motion collissions with the surface in question. Thus they transfer less net horizontal vector energy to that surface compared to the molecules on the slower flow surface. And this net difference is the lift force.

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theory aside, come and try a Canoe at the RYC Sail a Small Boat day. 1st Sat of March I believe.

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Lift comes down to f=ma.

 

Populist explanations such as "curved surfaces" are just that. The cause of lift is not molecules judging whether a surface is curved or not, or whether a shape is symmetrical or not.

So then why does a flat plate generate "lift"? Because in snipes it does (I know the answer, I'm just pointing out that this isn't quite accurate)

 

Note also that Bernoulli's equations about "pressure" around a curved surface don't actually rely on "compressibility" A better way to think about it is that on the side the molecules are streaming past faster, fewer of them are engaged in browninan motion collissions with the surface in question. Thus they transfer less net horizontal vector energy to that surface compared to the molecules on the slower flow surface. And this net difference is the lift force.

 

I think that's pretty much what he means by f=ma. The molecules hit the bottom, bounce off, and impart some kind of reactive force to the bottom of the wing that the top never sees. Sure feels like that when I put my hand out the car window anyway. I don't know if invoking Brownian motion adds anything to the concept; plain old vanilla motion would seem to do just fine as long as there is some flow.

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Pilots like to say about wings at any rate, bottom Newton, top Bernoulli. It's probably properly angular momentum? But planing would seem to be Newton.

 

I dropped an apple today! The puppy got it......

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Yes, most aerodymaic theories of flight rely on the air being compressed or expanded and hence changing density and pressure, so that the bottom pressure is greater than the upper pressure, causing lift. All believable until you put a foil into incompressible fluids like water. So according to most theories hydrofoil sailing is impossible. Another reason why I do not like most sailing theories. QED.

 

That has not been my understanding. For subsonic airflow, air is usually treated as incompressible, which is completely relevant to hydrofoils. Bernoulli based explanations usually cite changes in velocity as the cause of the pressure difference, not compression or expansion of the air. If you compressed the volume in inverse proportion to the velocity increase, the pressure would remain constant. For subsonic airflow, it's the constant volume and changes in velocity that cause the pressure changes.

 

Regarding Bernoulli vs Newton, Bernoulli's principle is derived from newtons second law. Although the use of Bernoulli's principle to explain lift produced by a wing has been called into question in recent years, the principle is not actually wrong. Yes it does all come down to F=mA, basically a mass of air is accelerated downwards. Bernoulli's principle, as it has been used, may not explain that. If used correctly however, it may explain the mechanism used by the wing to accelerate and redirect the airflow.

 

In all of this, theories about fundamental physics will not tell you how to design a faster canoe. But if you have an idea for building a faster canoe, you can check it against theory and possibly save yourself some time and money. Furthermore, thinking about or learning the theory will generate new ideas along the way. For this reason it is worth discussion.

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Yes, most aerodymaic theories of flight rely on the air being compressed or expanded and hence changing density and pressure, so that the bottom pressure is greater than the upper pressure, causing lift. All believable until you put a foil into incompressible fluids like water. So according to most theories hydrofoil sailing is impossible. Another reason why I do not like most sailing theories. QED.

 

That has not been my understanding. For subsonic airflow, air is usually treated as incompressible, which is completely relevant to hydrofoils. Bernoulli based explanations usually cite changes in velocity as the cause of the pressure difference, not compression or expansion of the air. If you compressed the volume in inverse proportion to the velocity increase, the pressure would remain constant. For subsonic airflow, it's the constant volume and changes in velocity that cause the pressure changes.

 

Spot on (and about why theory matters as well) about the incompressibility. In essence PV =nRT has no time dimension. If we add the time dimension we get

 

dP
/
dt
dV
/
dt
= mRT

 

and in essence the "curved shape" puts the same molecules (nRT) into a larger spatial volume (one dimension - length - has increased due to curvature) so WRT the edge of the volume (the curved surface) dP/dt is negative because dV/dt is positinve.

 

But the air itself is not being compressed or decompressed

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I have found a point on which ICNutter, BalticBandit and I agree on. Discussing theory can help generate ideas about design, but does require the effort to learn and understand the concepts, which is not everybody's idea of fun, and let's face it, it's fun we are all after.

One point, the derivative of PV = nRT is VdP/dt + PdV/dt = 0, not the expression given by BalticBandit.

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All very well getting into the aero theory folks, but the reason why the boat stuff is so complicated and interesting is that we are operating at the boundary of the two media. And that means nearly everything changes in detail.

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I have found a point on which ICNutter, BalticBandit and I agree on. Discussing theory can help generate ideas about design, but does require the effort to learn and understand the concepts, which is not everybody's idea of fun, and let's face it, it's fun we are all after.

One point, the derivative of PV = nRT is VdP/dt + PdV/dt = 0, not the expression given by BalticBandit.

My bad... sloppy calculus on my part.

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Alright, since the topic shifted to fun, I sure like see build photos over the heavy theory.

Especially when the photos go all the way to a sailing boat and there is a narrative about the process.

That was something the US Canoe site had when it was up that I miss.

 

...I know, there are probably a ton of people who wouldn't think that is fun either.

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Great info - will be interesting to see how that compares to the sixties full scale canoe test data.

Cheers

For unknown reasons, I don't seem to be able to post Bill's test report.

PM your email and I will send it to you.

SHC

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Actually Mr 7776

 

After the discussion on wing theory has started to die down I was thinking of introducing Cold Fusion to the discussion. I won't be building my boat for a while and thought we needed another topic to keep it on the front page. :lol:

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Ive started playing with a IC hull in delftship, but im a bit lost as to where in the box evryone is. Below, is the basic dims of my design, could you guys tell me if im in the ballpark?

 

Lenth 5200mm

Bmax 750mm

Waterline beam

390mm

 

Also, just how hard are these boats to sail?

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Waterline beam could be an issue. Is that Half beam?

 

BTW piece of piss to sail. Anyone that says different is a big girls blouse. (bit of Australian for Australia Day)

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It depends on how hard you sail. To sail an IC around for fun with no pressure when to tack or gybe isn't that hard tricky to tack at first but not impossible. To race an IC and at the pointy end of the fleet as any other class is far more challenging... But the difference is I have found the IC rewards effort more than any other boat I've sailed.

 

I have no idea what my waterline beam is doubt its that low but then that depends which end of the bus Im at all the way forward I might get towards that number (doubt it) all the way back I would be no where close...

 

ICU2

Ive started playing with a IC hull in delftship, but im a bit lost as to where in the box evryone is. Below, is the basic dims of my design, could you guys tell me if im in the ballpark?

 

Lenth 5200mm

Bmax 750mm

Waterline beam

390mm

 

Also, just how hard are these boats to sail?

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Theory is not everybody's idea of fun, but it is for some of us. Those who just get on the water and sail may (probably) get better results thro' more practice. I, and probably most of you, have seen race where the time difference between the first and last boat has been upwards of 30%, for the one design IC. The good sailors have a combination of natural talent and practice. As an average sailor, I and fully aware that I will never be able to design a canoe that is, say, 15% faster than the average and take me from 'average' to first place. Even if I could design a canoe which was 5% faster than any other i would probably still be in the middle of the fleet and no-one would be able to detect the superior design. People will look at the best sailors and follow what they do design wise. Quite a rational thing to do, but does it guarantee that the boats are the 'best' they could be. If you can sail 15% faster than average then you don't need the best boat, you need a good reliable boat. I know I have taken an extreme case, and the average spread of times over all races is less than 30%, but the same argument still applies even if the spread is only 10%.

I notice that the RS 700 and the Musto skiff both have Portsmouth yardstick below the IC, giving them an average fleet speed round the course of about 2.5% greater than the IC. These new breeds of boat have upped the anti, and can the canoe respond?

Personally, My aim in thinking theory is to improve my own performance and for the fun I get out of it, I also believe that it will give me confidence in the boat which i eventually build and this will ultimately allow me to sail better.

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but the same argument still applies even if the spread is only 10%.

10% would be an astonishingly narrow spread, its wider than that at the Olympics in Lasers. 25% is typical in most classes in the UK.

 

The general point is well made: I for one don't know how to find out whether the Champion is the Champion because of his/her boat or in spite of it.

 

I don't know that there is any need to "respond" to the RS700 and Musto Skiff being a bit faster round the track. We all know how to make a line honours boat: it needs to be as long as possible and have as much rag as possible. The AC demonstrates that if you put a lot of extra rag on downhill the boat goes a little bit faster, but if you want to play top speed with big rags then the two and three handed skiff types do it far far better(1). However I've done that to my satisfaction, and at the moment I find the subtleties of the Canoe design space a more interesting place to be.

 

(1) and a big multi will go even faster than they do.

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On a slightly different theoretical topic, I have always thought it would be really cool for a development class to make a part of it's class rules that a design be made available/published to the class.

I think in classes where the builders do the designing it would not be so great, but in classes where the sailors are doing a good chunk of the development, I think it would be great.

I have also thought it would be cool if such class got behind a cad package that at least had a cheap or free community version so people could easily share these theoretical ideas in a more concrete way.

 

delftship comes to mind as one that could come close to supporting that.

With 3d milling getting faster and cheaper, I think we are not far from from it being feasible to having a plug or a mold milled for small runs.

A consistent modeling package is a key enabler for something like that.

 

I think there would be a big savings if people could share cad models even eventually convey complete rigging ideas within a cad model.

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it would be really cool for a development class to make a part of it's class rules that a design be made available/published to the class.

 

I think that happens to a reasonable extent anyway. But its really not very hard to take the lines off a dinghy sized boat (well, not if you're in the same country anyway). Two people armed with rules and a few long straight bits of wood can do it in an hour or three. When I wanted a good view of a 49er bow as an input to my one off singlehander I went round to the nearest club where there was one and grabbed the numbers while these bemused guys were rigging their boat! It might even be less work than interpreting one of [redacted]'s tables of offsets [grin].

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The box is pretty easy.

Take a piece of paper and mark the maxes and minimums.

 

a) The overall length shall be not be greater than 5200mm or less than 4900mm. This measurement shall include any protective strip and shall exclude rudder and rudder fittings. However if the athwartships width of the rudder or hardware exceeds 50mm within 150mm of the bottom of the hull at the stern, the length shall be measured to the aftermost point of the rudder.

B) The projection on to a horizontal plane of the

line of greatest beam shall be a continuous curve,

and at bow and stern shall lie inside lines which are

at 45º to the center-line and which pass through the

center line not more than 25mm beyond the extremities.

The line of greatest beam may be a combination of convex, concave and straight lines.

No concave curve shall have a radius of less than 100mm.

No convex curve shall have a radius of less than 60 mm except within 50mm of the stem and stern.

There shall be not more than one concavity per side in the line of greatest beam.

c) A 1000mm straight edge set to span such a concavity fore and aft, with 0mm at the outboard tangent, shall nowhere be more than 100mm from the hull skin (measured perpendicular to the straight edge.)

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.

f) Nowhere shall the outside skin of the hull exceed 1100mm in beam.

g) The hull surface shall be a continuous structure fore and aft and athwartships. It shall not be breached by any through structure or holes except by no more than one centerboard trunk and one rudder trunk.

h) The hull and all equipment required for

racing, except for sails, battens, clothing, food and

drink, shall be weighed together and dry and shall

have a total mass of not less than 50kg. The mass

of correctors shall not exceed 10kg. Correctors shall

be fastened permanently either to the seat carriage

or the outside of the deck adjacent to the seat carriage and

shall be clearly visible.

The number, weight and placement of correctors shall be noted on the measurement certificate.

Correctors shall be marked by the measurer.

i) The hull shall not be ballasted.

j) There are no restrictions on the material or

method of construction of the hull.

 

"In general" we have gravitated to the skinny end, with the Beam Measurement Station further aft half length.

ICs are outright tippy. You cannot just sit on one and sail around like you can on a catamaran or beamier dinghy. This makes sailing a more active and interesting pastime.

ICs get harder to sail he harder it blows, the square of the velocity and all that, so you may find it pretty easy in 8-10 but completely overwhelming in 18-20. I think the challenge is a good thing.

I used to be very good in big breeze, because I have gotten old and out of shape and haven't sailed as much as I should have, I am now less confident in heavier air. The boat can kick my ass now when it couldn't 15 years ago.

I also like to think about what I am doing when I am doing it, so having an understanding of the dynamics makes observing the interplay of theory and practice part of the fun as well. As many suggest, time in the boat is vital to competitive success, so I reason that a boat that is most entertaining to sail is the boat you will be most successful in. For me that means a boat that challenges my ability and which encourages experimentation. Go sailing, change something, go sailing, change it again go sailing, try something that didn't work last time again, go sailing, think you have it all sorted, go sailing go sailing go sailing, decide that isn't good enough, go sailing, "Figuring it out" is the fun part.

SHC

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It might even be less work than interpreting one of [redacted]'s tables of offsets [grin].

 

But it's worth the effort - the battens have just gone onto the mould, and just touch every frame! ( apart from the kinked bit at the back that's 'off the page' so to speak.

post-2679-010247100 1327702447_thumb.jpg

post-2679-021880400 1327702468_thumb.jpg

post-2679-028534600 1327702478_thumb.jpg

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Ive started playing with a IC hull in delftship, but im a bit lost as to where in the box evryone is. Below, is the basic dims of my design, could you guys tell me if im in the ballpark?

 

Lenth 5200mm

Bmax 750mm

Waterline beam

390mm

 

Also, just how hard are these boats to sail?

 

The narrowest waterline beam I've managed to design so far is about 570mm and I'm not sure I'd want to try to sail it!

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Andy

Great to see another boat taking shape! Is this for Jim or are others in the picture as well?

As to water line width I think Dragonfly is 735 ish. Playing around with shapes the less rocker you have the fuller then ends tend to be (or more immersed) and the narrower the max beam is. Dragonfly and Monkey have I think the most rocker of the newer boats with 100mm. I kept this in as I thought that more rocker would not make that much difference speed wize but would help to keep the bow out without having to move the seat back (particularly relevant when going around top mark, real op for over taking) and also would help tacking. I have found this to some extent correct, Dragonfly goes about well, the main sail shape has not helped and it puts me in , have had it recut and more flexable batterns put in and I think its better. The boat still responds to moving he seat back but does not need it moved back much and is OK if not moved at all (on a reach, up wind in all weather seat forward, just slightly less in strong wind)

The way to make these boats go fast is to practice!!!!! but you still need a boat that has ok speed to do well but you can make this, or loose it , in the rig or foils, hull is only a part of the picture, all be it avery interesting one!

I would recommend anyone intrested to build some thing that you like the look of, keep to a standard rig untill you have proved your hull ideas and not worry that it may not conform to theory, its better to get out in some thing than nothing. Monkey was the first boat I designed, it was not the fastest or best but in Oz it stayed together, I was there, It had a proven rig and foils, and over the years I have sailed canoes enough to have a fair amount of practice, so I was competitive. Have a go its great fun!

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gallery_8603_259_94233.jpg

 

USA-245 "Hellcat" a few weeks ago; measuring things out on the rig. It's been a long time coming, but she'll be on the water in Richmond this Feburary. Spent this morning rigging bungee takeups underneath the seat carriage. I was astonished that my setup required no fewer than 15 sheaves under the carriage (with at least a half-dozen more inside the seat) to get things working smoothly, but the end result seems pretty nice! Splash this winter, test, then do final corrections and paint in the spring. Let the arms race for Worlds '14 begin! Though, to be honest, I started the build with North Americans '10 as my goal....sigh.

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Looking at the seat as a type 1 lever, is the windward rail the fulcrum? Is there any difference qualitatively between the seat ending at the centerline of the hull vs the lee rail? Or is the whole setup a type 2?

 

Seems if the seat ends at the centerline, the balance of the forces is trying to lift the hull out of the water? Seems to me this is addressed by the rule?

 

If this has been answered already, please steer me that direction...... :D

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Looking at the seat as a type 1 lever, is the windward rail the fulcrum? Is there any difference qualitatively between the seat ending at the centerline of the hull vs the lee rail? Or is the whole setup a type 2?

 

Seems if the seat ends at the centerline, the balance of the forces is trying to lift the hull out of the water? Seems to me this is addressed by the rule?

 

If this has been answered already, please steer me that direction...... :D

There are alternative arguments for the seat to go to the lee gunwale or only to the centre line.

 

For the centre line design the bearing loads between the seat and carriage at the windward gunwale are double that of seats supported at the leeward gunwale, as are the downward forces needed at the leeward end of the seat. Consequently the carriage has to be stronger to take the higher loads and also the centre of the carriage has to resist that load not just the parts over the carriage slides. For the full width option there centre of the carriage carries no seat loads at all so can be minimal.

 

The benefit of the centre line design is that the seat is shorter by 375mm (half beam) and so might be lighter, provided the extra strength needed does not balance out the gains in being shorter. Also when sailing in light winds and when the seat is centred, it extends out less each side, so will hit less waves with any roll or chop.

 

As far as applying righting moment to the boat it makes no difference what so ever. What matters is where the crew weight is applied to the seat. There is no difference to the loads on the hull.

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Looking at the seat as a type 1 lever, is the windward rail the fulcrum? Is there any difference qualitatively between the seat ending at the centerline of the hull vs the lee rail? Or is the whole setup a type 2?

 

Seems if the seat ends at the centerline, the balance of the forces is trying to lift the hull out of the water? Seems to me this is addressed by the rule?

 

If this has been answered already, please steer me that direction...... :D

 

The seat is a cantilevered beam. The loads at the support points are equal and opposite, that is, the downward force at the windward support point is equal to the upward force at the leeward support point. The loads cancel out so it neither lifts nor sinks the hull. If the leeward support point is at the hull centerline, both forces will be twice the magintude that they would be if the leeward support point was at the leeward gunwhale.

 

On my Nethercott, I built a carriage that has the support points over either gunwhale. This meant that I could build a lighter carriage because the loads are lower than with the conventional centre support carriage (it also eliminates the carriage bending moment). The trade off is that the seat has to be longer (adding weight), but this is also partially offset by the fact that as the loads in the seat are also lower, the seat can be built a little lighter.

 

EDIT: I see Phil beat me to it!

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Looking at the seat as a type 1 lever, is the windward rail the fulcrum? Is there any difference qualitatively between the seat ending at the centerline of the hull vs the lee rail? Or is the whole setup a type 2?

 

Seems if the seat ends at the centerline, the balance of the forces is trying to lift the hull out of the water? Seems to me this is addressed by the rule?

 

If this has been answered already, please steer me that direction...... :D

 

The seat is a cantilevered beam. The loads at the support points are equal and opposite, that is, the downward force at the windward support point is equal to the upward force at the leeward support point. The loads cancel out so it neither lifts nor sinks the hull. If the leeward support point is at the hull centerline, both forces will be twice the magintude that they would be if the leeward support point was at the leeward gunwhale.

 

On my Nethercott, I built a carriage that has the support points over either gunwhale. This meant that I could build a lighter carriage because the loads are lower than with the conventional centre support carriage (it also eliminates the carriage bending moment). The trade off is that the seat has to be longer (adding weight), but this is also partially offset by the fact that as the loads in the seat are also lower, the seat can be built a little lighter.

 

EDIT: I see Phil beat me to it!

 

:)

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This is also known as a "couple" and yes longer the seat less loads etc...

Looking at the seat as a type 1 lever, is the windward rail the fulcrum? Is there any difference qualitatively between the seat ending at the centerline of the hull vs the lee rail? Or is the whole setup a type 2?

 

Seems if the seat ends at the centerline, the balance of the forces is trying to lift the hull out of the water? Seems to me this is addressed by the rule?

 

If this has been answered already, please steer me that direction...... :D

 

The seat is a cantilevered beam. The loads at the support points are equal and opposite, that is, the downward force at the windward support point is equal to the upward force at the leeward support point. The loads cancel out so it neither lifts nor sinks the hull. If the leeward support point is at the hull centerline, both forces will be twice the magintude that they would be if the leeward support point was at the leeward gunwhale.

 

On my Nethercott, I built a carriage that has the support points over either gunwhale. This meant that I could build a lighter carriage because the loads are lower than with the conventional centre support carriage (it also eliminates the carriage bending moment). The trade off is that the seat has to be longer (adding weight), but this is also partially offset by the fact that as the loads in the seat are also lower, the seat can be built a little lighter.

 

EDIT: I see Phil beat me to it!

 

:)

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It has always surprised me that there are not more seat breakages. It is a highly stressed part of the canoe.

As correctly stated the compression loads at the contact points between the seat and the carriage are reduced by using a seat which extends across the whole beam of the canoe. These are not, however, the only things which should be taken into account.

For a seat kept captive at the centreline of the boat there are four loads on the carriage which are

R(1) at the windward gunwale due to the seat, = 2W(L+B/2)/B down

R(2)also at the windwrd gunwale from the deck track = W(L+B)/B. Up

R(3) at the centreline constraint = 2WL/B up

R(4) at the lee gunwale from the deck track = WL/B down

Here W is the helms mans weight, L the seat extension, and B the seat carriage width.

Putting reasonable figures in for these parameters will give the loadings. Comparing them with the values of compression strength for timbers will give the necessary contact area between the seat and the carriage at these contact points.

For a seat which is captive at either end of the carriage then the formulae change to-R(1)=W(L+B)/B =R(2) And. R(3)=WL/B = -R(4). Negative implies downward, positive upward forces. As has been said the load at the lee and windward ends of the seat is just about halved.

Personally, I have never seen a seat fail by crushing at the contact points, perhaps other could comment on their experience.

As IC Nutter says the over length seat generates no bending moments on the carriage. However, the maximum bending stresses in the seat itself will however remain the same for both setups, with the maximum stress in the top face occurring at the point where the seat is over the end of the carriage. Rough calculations suggest that for a seat with 4mm ply top facing the stresses in the top face are near or maybe above those which can be supported by the ply. This suggests to me that substantial loads are being carried by the framework inside the seat. I have done no calcs to confirm this. I have seen seat failures due to tension crack propagation at this point. The maximum bending loads in the carriage for a centre captive seat work out to be about half of those in the seat.

Back to the question over long or normal seat. My answer would be to go for the normal seat. The extra weight for an added 370/400 mm of seat would probably be over a kilogram which would be difficult to remove from the carriage. I would suggest reinforcing the carriage with unidirectional carbon tape (appropriately). From my recollection a 2.5 cm wide tape will carry about 10 kilonewtons, thus supporting the entire static loading which is applied, all at a weight of a few grams. Similarly tape under the top face of the seat will allow a great reduction in the amount of wood used in the seat, again reducing weight.

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I have had several seats pack up from crushing at the exit point (at the windward bearing point.)

I attribute this to getting older and fatter and to he fact that the minimum weight rule came off the seat.

The seats I broke all weighed well less than the old 9kg minimum.

I've been having kind of a run of it because I'm trying to get the weight down under 6.5 kg.

Although the seat is "shifting ballast," it seems to make little sense to make it any heavier than it as to be. It just gets harder to move when you get pooped or are trying to unscrew yourself. And if you weigh as much as I do, you aren't concerned about righting moment.

Care must be taken to assure that the loads are well distributed at the exit points On wood seats, I often put an inlay of G10 at the exit points to prevent the wood from crushing across the grain. On composite seats, the laminate should be built up 3-4 times in the crush zone and you should also consider a high density core replacement.

The fit of the seat within the carriage at this point is also important to assure that the thing doesn't point load unnecessarily.

This is a bit tricky, because point loading is what prevents you from sliding under the boom every time the boat heels more than 10 degrees. The seat has to be kind of sloppy in the carriage in order to jam properly when you sit on it.

Seats also become unzipped when the helmsman crashes down onto it in a tack or gybe. This is often a pretty violent body slam that either de-bonds or sheers the core. I also used to have to replace the bottom skin ( 1/8" plywood) fairly frequently because when I'm sailing well, the top is coming of every 4th wave or so. The new carbon bottomed seats don't suffer as much from this, but I have blown one of those up too.

SHC

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Couple of tangential happenings.

 

The stern of the skiff board is intriguing......

 

http://www.lbwindsur...fing+Journal%29

Do you know if this design was ever built, or is it a computer file only?

 

As the Freeship file is provided, I'd be tempted to build it if it's actually proven, as the Exocet is nearly $3000. Not that that's unreasonable for what you appear to get.

 

 

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Hard to figure whether he's done it or not. You could email him?

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Thanks; I see the article does have his e-mail address. Ordinarily I'd rather find out another way whether a design has been sailed, as it could come off as critical of the designer or a sore spot to ask, but on the other hand in this case there can be the polite aspect of writing to make sure of having his permission to build.

 

(Not technically necessary to do as he posted it, but polite anyway.)

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I think the Skiffy and the Exocet give the thumbs up to Mr. Maas's design approach.

The Skiff's transom even starts to approach the big butt canoe stern, like some of the formula boards have, and since they arent required by rule to do it, maybe there's something to it! :lol:

 

edit:

 

post-906-059537100 1329026078_thumb.jpgpost-906-016906000 1329026112_thumb.jpgpost-906-076148700 1329026138_thumb.jpgpost-906-042942900 1329026194_thumb.jpg

 

another edit: talk about a non existent rocker on the Exocet rs D2!

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Perhaps if being flexible with definition, it does have rocker when trimmed for displacement mode, though certainly it's as flat as can be in the trim shown.

 

If so then the deepest point is unusually far forward. But the board is really not optimized for displacement mode I would think.

 

I'm totally guessing on the amount of immersion but as a mockup:

 

Exocetwith15degreetrimandguessedwaterline.jpg

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The implication, at least by the manufacturer, is that displacement sailing - or gliding- is one of the goals of the design. It looks to me like Phil's rocker practice pushed a bit more to the extreme. But like Phil said, it works, even though by the classical norms of dinghy design it shouldn't.

 

The skiffy is based on 18 design trends, at any rate.

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Yes, one of the goals agreed and definitely, but I was meaning to say that the design wasn't optimized to be the best a board could be in that mode and is probably a fair bit from that, for the sake of planing performance.

 

How much of a hit it is taking, I don't know. Apparently not too severe though, at least where there's enough breeze for people to be windsurfing at all.

 

I do think it's very interesting how windsurfing designs are dealing with the combined needs of planing and displacement performance! Obviously a lot's been done lately.

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which got me thinking (old school, no? :) ) about this 1/3 model- I guess you could argue direction either way, depending on whether you're looking for elongated streamlined planing area, and/or the position of the planing (edit-stagnation point) area, which would be pretty much under the widest area (the big black athwartships line) of the hull if the short end was the bow. The rocker is straight at both ends 1/4 the way in from the pointy parts.

 

post-906-070864400 1329086807_thumb.jpg

post-906-067735600 1329086840_thumb.jpg

post-906-014609900 1329086876_thumb.jpg

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Hi Andy

Is that pattern work for a female mould , or a male mould? Quite a collection of differant shapes you have now made for the canoe!! This one looks like it will be fairly stable, quite flat across the transom, but then looking at the front/ mast area quite round so perhaps not? Any chance that one will be at the Euros in the summer? if I am down your way any chance I can take a look?

Alistair

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Hi Andy

Is that pattern work for a female mould , or a male mould? Quite a collection of differant shapes you have now made for the canoe!! This one looks like it will be fairly stable, quite flat across the transom, but then looking at the front/ mast area quite round so perhaps not? Any chance that one will be at the Euros in the summer? if I am down your way any chance I can take a look?

Alistair

 

It's a male mould, it's hard getting enough orders to justify a female mould.

This will be design no 4 that I've built.

It's deep and roundy at the mast, going flatter as it goes back.

post-2679-062423200 1329316782_thumb.jpg

( projected aft another foot or two it would go concave! )

I maybe should have strip-planked the front bit, but did diagonal ply planks instead.

Or maybe I should have done a CNC cut mould... next time.

You're welcome to come and have a look when you're here.

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The rule states that the pointy parts of the hull have to fit inside an angle of 45 degrees from the centerline.

 

Does this mean

 

22.5 degree half angle (22.5+22.5 degree half angles= 45 degree full allowed angle)

 

or

 

45 degree half angle (45 +45 degree half angles = 90 degree full allowed angle)

 

?

 

Paul

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+/- 45 degrees from center line.

Or stated another way, he included angle from the port side to the starboard side has to be less than 90 degrees.

SHC

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Depends which site you're looking at. The one below has links to most info

 

Oh heck, don't publicise my devboats page Jethrow, that's just my dev/test area for intcanoe.org.

 

I'm likely to have some spare time over the next week as I'm laid up, so if I get some inspiration I shall try and do some work on that, esp the History stuff because I ran out of maerial about WW2.

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speaking of America, I am trying to complete my IC and have a pile of technical questions

 

1) could use some help with positioning jib leads. the sails are stock Kinder's. what is the sheeting angle?

 

2) for the gybing centerboard, will clamping the top and top only provide enough stability so the board won't randomly gybe downwing?

 

3) what diameter bolt should is appropriate at the hounds?

 

4) what diameter bolt is appropriate for the spreader pivots?

 

4a) is 11" in the ballpark for the spreader length, or should i start longer?

 

5) what is done to connect the mast stump to the mast? a socket where the stump and mast bear directly upon each other? or will that cause bearing stress problems with the mast?

 

6) does the base of the mast stump need to be adjustable? i don't think so but every other part of this boat has a nuance

 

7) are 1 gallon milk jugs ok for flotation, or do i rob one of my optis for a blow up bag and if i do, do i worry about reinflating it?

 

8) does anyone cartop their IC? my wagon is rated for 200# on the roofrack. is this sane?

 

9) how many layers of carbon are needed to hold the chainplates in. the hull is a maas type and the chainplates are l-shaped and hook under the lip in the hull. concern is that the outer carbon layers affect the profile and can look like rule beater bumps which they arent

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speaking of America, I am trying to complete my IC and have a pile of technical questions

 

SHC and CM will give you better info, but FWIW here's what this rather less advanced cano builder can remember.

 

> what is the sheeting angle?

You will badly want lateral adjustment between different wind conditions, so its really not too critical. Just figure the region from photos and err on too much adjustment.

 

> what diameter bolt should is appropriate at the hounds?

Not sure what you mean. I have T terminals for the shrouds and a decent block for the jib halyard: no bolt involved

 

> 4) what diameter bolt is appropriate for the spreader pivots?

Mine are locked in place with two 4mm stainless bolts each side, but I think what they go through is more important.

 

 

> 5) what is done to connect the mast stump to the mast? a socket where the stump and mast bear directly upon each other? or will that cause bearing stress problems with the mast?

> 6) does the base of the mast stump need to be adjustable? i don't think so but every other part of this boat has a nuance

Need to see what you are doing.

 

> 8) does anyone cartop their IC? my wagon is rated for 200# on the roofrack. is this sane?

I've done it, but getting the mast up there as well is a bunch of hassle. On the whole a trailer is less stressful, esp when packing up tired after a hard event.

 

> 9) how many layers of carbon are needed to hold the chainplates in.

I usually figure, as a rule of thumb for the unscientific, that the carbon, well consolidated, should be as thick as a stainless steel piece would be.

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speaking of America, I am trying to complete my IC and have a pile of technical questions

 

1) could use some help with positioning jib leads. the sails are stock Kinder's. what is the sheeting angle?

 

I start by making a mark half way up the jib luff. The jib lead would be in line with that mark and the clew.

 

2) for the gybing centerboard, will clamping the top and top only provide enough stability so the board won't randomly gybe downwing

 

Yes. I make the cassette stiff enough so that there isn't a lot of torsional load on the board when the gyber is locked off. Not sure how important that is.

 

3) what diameter bolt should is appropriate at the hounds?

 

If you are hanging your shrouds off that bolt 1/4" does the job. I thread a piece of rod and make sure the threads aren't bearing on the carbon. You do need to thread far enough that the shrouds are held in snug to the mast. I add an .090" carbon doubler there.

 

4) what diameter bolt is appropriate for the spreader pivots?

 

I use 1/4"

 

4a) is 11" in the ballpark for the spreader length, or should i start longer?

 

Mine are 10 1/2" from mast to shroud.

 

5) what is done to connect the mast stump to the mast? a socket where the stump and mast bear directly upon each other? or will that cause bearing stress problems with the mast?

 

There is a lot of torsion load from the spreaders to the mast step. I use a 1/4" bolt through the mast with a 3/8" s.s. spacer tube that slots into an s.s. pipe 1" tall or so that is welded to a s.s. plate which is bolted to the mast stump with 4- 1/4" bolts. I wrap some carbon around the mast base and round the bottom a little so the back corner of the mast isn't bearing all the load.

 

6) does the base of the mast stump need to be adjustable? i don't think so but every other part of this boat has a nuance

 

I don't move mine.

 

7) are 1 gallon milk jugs ok for flotation, or do i rob one of my optis for a blow up bag and if i do, do i worry about reinflating it?

 

I'm using box wine bladders. You need to make sure they are not going to get punctured by anything inside the boat.

 

8) does anyone cartop their IC? my wagon is rated for 200# on the roofrack. is this sane?

 

Almost sane. Probably a good idea to tie the boat to the bumpers too. If you can find anything to tie to down there.

 

9) how many layers of carbon are needed to hold the chainplates in. the hull is a maas type and the chainplates are l-shaped and hook under the lip in the hull. concern is that the outer carbon layers affect the profile and can look like rule beater bumps which they arent

 

The indent on your boat will take chainplates that are made from 12 layers of 200gsm uni and 2 layers of 200gsm cloth. I wrap the uni around a 1/4" rod then clamp it into an L shaped mold made of wood. That's not as easy as it sounds.

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1 I've found the starting point is + - 55" . Tall narrow Jibs have the sheet lead angle quite steep may need to be even higher than mid luff. For fine tuning, adjust the angle by moving the jib up( or down) on the forestay with the Halyard& jib cunningham.

2 yes, will still move a bit but easily managed.

3 Its all about contact area ,1/4 works but adding additional carbon around the hole is a MUST DO.

4 If you have a carbon bracket #10 is minimal, CM and others use a #10 with a "wellNut" which gives better than a1/4" dia contact area. And NO thread contact with the fiber or you've just created a rat tail file.

4a Depends on the height of the spreader bkt , type & stiffness of your mast ,your weight and what kind of conditions you sail in.With the mast in and plumb as you can make it run a string line from the hounds to the chainplate. Measure from the bracket pivot to the line add 1" and you have a starting point.

5 Contact area is king , thats why the tennon/socket works so well. If you use a bolt to resist the torque, most run it athwartships so the mast rocks on ithe bolt when the mast is raked .

6 Not really, DB casette can be moved fore & aft for fine tuning rig & balance

7 Just fine , seal the stoppers and leave them slightly deflated for changes in density altitude No need to have thm pop when you cross the Rockies Mts.

8 Yea but it's a wrestling match and I usually only do it for long trips or when I know I have help.

9 CM has that one.

 

speaking of America, I am trying to complete my IC and have a pile of technical questions

 

1) could use some help with positioning jib leads. the sails are stock Kinder's. what is the sheeting angle?

 

2) for the gybing centerboard, will clamping the top and top only provide enough stability so the board won't randomly gybe downwing?

 

3) what diameter bolt should is appropriate at the hounds?

 

4) what diameter bolt is appropriate for the spreader pivots?

 

4a) is 11" in the ballpark for the spreader length, or should i start longer?

 

5) what is done to connect the mast stump to the mast? a socket where the stump and mast bear directly upon each other? or will that cause bearing stress problems with the mast?

 

6) does the base of the mast stump need to be adjustable? i don't think so but every other part of this boat has a nuance

 

7) are 1 gallon milk jugs ok for flotation, or do i rob one of my optis for a blow up bag and if i do, do i worry about reinflating it?

 

8) does anyone cartop their IC? my wagon is rated for 200# on the roofrack. is this sane?

 

9) how many layers of carbon are needed to hold the chainplates in. the hull is a maas type and the chainplates are l-shaped and hook under the lip in the hull. concern is that the outer carbon layers affect the profile and can look like rule beater bumps which they arent

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thanks for all the answers. i'm still unclear about attaching the chainplates. they are made - the attachment is me holding one in place. the L shape takes the primary load, but how many layers of carbon are used to attach it?

post-32376-077570500 1329784504_thumb.jpg

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another view of the chainplate. the wine bags are a great idea. the money saved by switching Mrs Crap from bottle wine to bag wine can go towards rigging.

post-32376-075836900 1329784784_thumb.jpg

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CM can correct me if I'm wrong but they are simply epoxied in place. If you have access to some super duper aircraft grade bonding adhesive , use that, if not, what ya got.

One comment; the pair I installed were not as tall as those in the pix. The knuckle below the pin hole being just above the sheerline/ foredeck.

The taller the chainplates above the sheerline the greater the bending moment exerted on them by the shroud adjusters pulling toward the mast base or centerline.

Cheers,

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thanks for all the answers. i'm still unclear about attaching the chainplates. they are made - the attachment is me holding one in place. the L shape takes the primary load, but how many layers of carbon are used to attach it?

 

I have used West 105 but prefer Gougeon 276/176. I don't think you need any carbon.

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Number 8.

Buy a trailer when you get the second boat. Have Cartopped mine since 1992. No issues ever. If you can't lift the new rules boat on a wagon you have other issues.My pig AC loves the roof and whens the last time you had a wheel bearing freeze up on you car.

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No.8 continued - Since the weight was reduced I have always car topped my IC. Aside from saving on the cost of a trailer, bearing failure etc, other advantages include a much softer ride for your prized possesion, away from the muck and grime of the road and you don't have to restrict your speed -I have travelled thousands of miles at 80mph (130kph) without incident. A top tip is to get an aluminium trolley which is much lighter. I put my boat on top of an estate car, with the bow about 2 feet away from the front of the car, with the front of trolley tied down to the front emergency tow hook. This means the boat overhangs the back of the car by about 5 feet, so best to hang something bright at the aft end. I put a rope from the trolley axle down to the tow hook on the rear bumper, so the whole shooting match doesn't slide forward if you have to brake very hard. The mast is tied down to the roofrack on the offside, and even with the spreaders is within the width of the car. Sliding seat, foils and sails can be put in the boat, but best to put a top cover on so they dont fly out. The other advantage is its much easier to park. En route for the Worlds last year I stopped off for a couple of days in Hamburg and could park in the centre of the city in a normal parking bay, albeit with the stern of the boat overhanging the car behind me.:)

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No.8 continued - Since the weight was reduced I have always car topped my IC.

 

Well I stuck this into the other thread, but it seems more appropriate here:

 

post-40347-092246900 1330302382_thumb.jpg

 

This may be the single best argument behind dropping the minimum weight.

 

I have done a fair bit of solo cartopping with the 84-100+ kg boats and accessories.

 

Raingutters are the bees knees, but probably not quite so important for the new lighter boats.

 

One good trick I read somewhere (and used a lot) is the foam roller thing for singlehanded cartopping. I am surprised not to have seen anyone else doing it, though there are lots of those expensive Yakima roller things about.

 

Find PVC pipe that will fit over the bars. Get some nice, dense latex foam - 1" will work. And a can of fast tack upholstery adhesive. Do this outside somewhere. Cut foam the same width as the pipe is long. Spray the pipe and the foam with adhesive and wait a few seconds for it to tack up. Put the pipe on the edge of the foam and start wrapping. Spray both surfaces as you go. Rasp off the butt end you started with to scarf it onto the wrap around end, tack the free end to the scarf, let it set up, then rasp off the remaining corner until it's perfectly round. Now find some sunbrella and tack that onto the foam. You will need to use your knees and put the pipe on the ground to make the foam bend.

 

Now you can put the stern on the trolley, lift the bow, walk up next to the car, slide the roller over to your side, transfer the bow to the roller, then lift the stern and roll the boat forward onto the front rack.

 

I have never tied the boat to anything other than the rack, as long as it is firmly attached to the rain gutters and tied down tight, nothing else is required for panic stops etc. especially with the new, light hulls. Tie the mast on next to it like Phil described.

 

Be sure to copy the rig dimensions/hound height/spreader length slavishly from someone who is fast.

 

K

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I really like Karl's foam roller idea.

 

Having built many rowing shells over many years I have seen a number of them come back to the shop after flying off the roof of a car. Almost always they were still attached to the roof racks when they sailed away. Moral: tie your boat to the front of the car or make sure that, like Karl, you have rock solid rack attachment to your vehicle. Don't trust factory luggage racks.

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Good stuff:-)

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Sexy... Should be awesome to watch it being put through its paces if it's anywhere near as fast as it looks...

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Camie 313 was the best hi-tack spray adhesive, but I think it is illegal now. 3m has similar stuff though. Hi-tack only-permanent. Art supply stores tend to have it.

 

My rule of thumb is to grab the roof rack and push and pull vigorously with all my strength. If I cannot rock the entire car on its springs back and forth without the rack flexing then it is not strong enough to trust a boat to.

 

In general, you need a very solid factory rail or hard bolt points in a structural channel. The only cars with this sort of factory rack tend to be German or Volvos (which are now Chinese apparently). Most japanese and American car racks are more for looks. Similarly, the type of Yakima that mounts with clips under the door weatherstripping is not solid enough. Finally, strap everything down with good line. Having a bit of stretch in the line is actually desirable. Wedge it until the rack deflects. Lighter laminate boats need a cradle.

 

K

 

I really like Karl's foam roller idea.

 

Having built many rowing shells over many years I have seen a number of them come back to the shop after flying off the roof of a car. Almost always they were still attached to the roof racks when they sailed away. Moral: tie your boat to the front of the car or make sure that, like Karl, you have rock solid rack attachment to your vehicle. Don't trust factory luggage racks.

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Thule System racks on stock GM suburban racks have never failed in 19 years. Two padded windsurfer straps across the boat at the end of the foredeck and across the seat carriage are all that is needed. Have never tied the bow down. Made with pride in Detroit on the door. Make a dolly that fits the rack and turns into a dolly when you get there and you are set. Who's making the colorful sails. I need some grey ones cut right.

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Who's making the colorful sails. I need some grey ones cut right.

 

Those looks like Taylor sails. Eric said he was getting to use some retro windsurfing fabric!

 

Contact:

taylorsails@olympicwi-fi.com 360.775.0307 LOCATED IN PORT ANGELES WASHINGTON USA

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Looks like the tops of the sails are drawing nicely- how hard are you pushing down on the seat anyway?

 

 

:)

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