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30% bouyancy for a 49er is a ballpark guess for a type of hull at a froude number.

There is a figure in principles of naval architecture taken froma paper somewhere that gives proportion of displacement supported by lift and bouyancy at differing speeds, presumably based on rise of CoG on a heave potentometer in a tow tank. It is for a planing hull (which a 9er isnt, quite). For a semi displacement form, dynamic lift wont be made so quickly (more curvature in section specifically, more sucky sucky)

 

Re the tfoil - in the 14s it adds about a knot and a half to boatspeed once powered upwind.

Specific resistance of a semi displacement hullform (r/w) is about 0.11 at Fn 0.8 (10kts for an I14)

l/d of a 14:1 assymetric section aerofoil at about 8 deg AOA is 0.03

As such it is more efficient to support displacement, even partially, by foil than hull. Well, a hull of that slenderness and l/b ratio. Make it cat-skinny and its a different story.

The DCB N12 in the UK is showing that even on a slow boat, the tfoil can give a net reduction in drag (4kts upwind - ish)

 

Obviously you have to tolerate the pitching moment it creates.

Chris - Your wings are a bit stubby aren't they? That may be part of the problem.

I think that more of the problem is that you are moving one guy back nearly to the back of the boat in the canoe. Maybe not working the foil hard enough to earn its supper. My suspicion is that you are only dialling in a couple of degrees, so maybe not enough to overcome the wetted surface debt.

In the I14 you are moving 2 guys right to the back of the (admittedly shorter) boat.

At 10kts you'll be putting 700N ish upwards in the I14 from a 0.1m2ish foil, so about 6deg ish AOA.

Closer to 10deg AOA at say 8kts boatspeed.

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http://www.scribd.com/doc/50375823/Resistance-Characteristics-of-Semi-Displacement-Mega-Yacht-Hull-Forms-1-1

A good paper on semi planing / planing etc.

I think possibly doesn't capture the effect of l/b in semi planing regime enough - mainly because it is tough to compare apples with apples - change l/b (at const length and displacement in most sailboat cases), slenderness ratio changes, transom immersion changes etc. Esp in a monohull centric paper, where high l/b is beyond what is acceptabl for initial stability and interior volume

 

Re pointy transom canoes.- the canoe is a pretty quick sailboat - it is fairly constantly in the semi displacement regime, and nudges the planing regime a decent bit.

Minimising hull drag is a case of maximising l/b (done - rise of floor rule)

reducing buttck curvature (generally pretty straight - no real penalty for transom immersion at lower speeds unless cutoff is very agressive)

Whilst tapered, the transom is still a transom, so will run dry from 5 ts ish upwards, which is good.

 

At higher semi displacement speeds (so 8kts and upwards for your 17' canoe) then you almost can't have too much prismatic (fullnes in ends - kids the bow and stern waves into thinking the boat is longer)

And for minimal resistance your LCB needs to be well alft - up to 12% of length.

 

Both of the last two points can't really be done if you have a skinny stern.

 

To be truly planing in a canoe you need to be doing 15kts, which I reckon realistically happens for what, 5% of the time around a course over a range of windstrengths - as such isn't really a design case.

 

As such the modal design case for the IC has to be an overdriven semi displacement hull - straight buttocks, immersed transom, approx half of midship sectional area, high Cp, LCB way aft, small entry angle as possible within first constraints.

Design a pure planing craft or pure diplacement vessel, and you will be slower most of the time.

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Daniel - a good post summarized the relevant points well.

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5 HULL

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.

 

10 RUDDER

a) The rudder shall not project more than

1000mm from the underside of the hull when

fully lowered.

B) The rudder shall be attached so that it

cannot normally fall out of its housing and

when free of the hull and shall float.

c) The rudder shall be capable of being

raised or removed without the use of tools with the canoe floating upright so as not to project below the underside of the hull.

d) There are no restrictions on the design or

material of the rudder other than the

rules above.

 

 

So, as long as the T foil is 150mm below the bottom of the transom, and it meets the other criteria, game on.

SHC

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Hope this may help a bit: from a paper by Paul Bieker, the I-14 foil lifts 400N(89.9lb)@ a speed of 9knots(S/l ratio=2.4, FN=.72)

The larger file is too big for this forum but the page below illustrates the point:

1-14 good.doc

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I have not come across the theory that the cavity in the water behind the boat is equal the submerged volume of the boat. Could you give me a reference that explains the theoretical justification ( And the maths behind the idea).

 

I can't give you a reference because it's my idea (I did mention that it was an opinion and this is Sailing Anarchy).

 

By way of explanation, in the early 90's I was involved in some tank testing for high speed ferry hulls, which are typically semi displacement hulls. My job, as a draftsman, was to define the hull shapes. No-one was able to tell me what the optimum shape was for the given speed range was and I became interested in being able to predict the best transom area/midship area ratio for a required hull speed, as I had noticed from the tank tests that this seemed to be an important factor in the semi displacement range. I didn't acheive that goal directly, but through analysis of the tank test data and trial and error, I did end up devising a spreadsheet based resistance prediction method for ballparking a hulls resistance behavior. Although not very accurate, it does seem to cover a wide range of hull types unlike other methods based on statistical reduction. I'm not a mathematicion or a scientist, but I have developed a bit of an interest in maths through this process.

 

The cavity theory is an inference from my work on the resistance method, but there is no proof for either. It's all intuition and guesswork. The resistance method works by calculating the work done by the hull in parting the waters, so to speak, and the work done by the water on the hull as it flows back against the reducing sections (if any) at the aft end of the hull. The general idea is that as the hull moves it must constantly create a hole in the water for it to sit in. The water, on the other hand, wants to flow back into the hole created by the hull. My theory is that there is a particular speed for any given hull where the rate at which the water flows back in behind the hull will more or less match the shape of the hull. I think of this as the 'reasonant velocity' of the hull, but more commonly it's called the 'hull speed'. Below that speed we get 'pressure recovery' from the aft sections. Above that speed we get 'sucky time' and hence separation occurs.

 

A copy of the resistance spreadsheet is attached. It's also useful for doing rough hydrostatics calculations of generic hulls and provides section areas for mathematically faired volume distributions.

 

HullCalc5-120101.zip

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post-906-079586300 1326250091_thumb.jpgpost-906-066950200 1326250114_thumb.jpgpost-906-019815600 1326250140_thumb.jpgso, three hulls and some computer modelling.

 

#1

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Thanks ARE, Daniel and IC Nutter. This is all very interesting.

 

And this is a picture of my t-foil attempt. I think part of the problem was simply poor craftsmanship. The adjustment mechanism was very crude so it was difficult to accurately dial in the right aoa.

post-16686-007921200 1326251050_thumb.jpg

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Thanks ARE, Daniel and IC Nutter. This is all very interesting.

 

And this is a picture of my t-foil attempt. I think part of the problem was simply poor craftsmanship. The adjustment mechanism was very crude so it was difficult to accurately dial in the right aoa.

 

Part of the allure of the T-foil is that you could do potentially do away with the sliding carriage and save some weight. I just don't think it would be fast though.

 

When I was involved in the high speed ferry tank testing, which involved seakeeping tests, we tried a T-toil at the transom on a narrow monohull model. It reduced the pitching allright. Instead, the whole boat heaved up and down, diving through the waves like a porpoise. Unfortunately we abandoned the idea without further investigation. I would have liked to have tried it with a wave piercing hull.

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3 hullpost-906-088001200 1326257705_thumb.jpgpost-906-036610000 1326257722_thumb.jpgpost-906-040003600 1326257742_thumb.jpg

 

How much does the rule balance slipperyness vs lift? I know this (#3) isn't a canoe, but it is kind of close to the maas hull. Kind of. Didn't have a Maas hull inside the little grey cloud above my head. Thought I did.... but the wider the ass, the more the wave drag goes up towards forced ;and. at least in CFD land.

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Chris

How much of a ballache was it to build that swinging up rudder box? What bearings and shafts did you use? And did you take the control system up through the shaft?

Dan

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Trenace - just because most sailors do not know the way Navel architect use a term does not make it wrong. It makes the sailors wrong, or at least means they are talking about something different. Maybe you would like to share your definition of planing!

I didn't say the NA use is wrong.

 

My post was intended to mean that with sailboats sharp distinctions often don't occur at any particular round-ish number (such as 2.5 or 3.0 for SLR) and further the behavior may be different between different boats, for example between a skiff and a catamaran even at the same SLR.

 

I personally am not assuming that any NA who presents numbers like these is claiming any such thing either.

 

For communication I generally try to understand the intended point of what people are saying... it can be true that a "dictionary" definition can be helpful in many instances but it seems to me that with sailboats there will be more misunderstanding of what people mean by assuming that their use of "planing" matches up with these definitions, then there will be understanding. Unless choosing to specifically discuss with the person these definitions beforehand and agree on them.

 

I don't have a particular definition to offer. I do think it's an absolute that dynamic lift had better be a really major contributor before using the term "planing" and if it's only a minor contributor but the boat is above hull speed, then semi-displacement. But obviously, "really major" is vague. In practice it may be perception of having "come up on a plane," or coming past a bump in the curve and accelerating nicely from it. Imprecise stuff. But generally when listening to someone, he hasn't done a calculation to judge whether he was planing or not.

 

 

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then you almost can't have too much prismatic

I dunno, I've sent myself down some bad blind alleys chasing Cp... I went too high on my one off singlehander.

 

According to my sums the Cp on IC drawings I've looked at isn't that high, and the needle bows on the modern boats give them a lower Cp than,for example, the Nethercott, which comes out at as .554 in my model, against .543 for my model of Chris' design. Its also a hard number to chase on a wedge shaped dinghy in that it changes so very dramatically with trim. Rocker, too is a big influence on Cp. Compared to the numbers we had on Cherubs Cp on good IC designs always looks low, but that's very apples and oranges. You can easily get a much higher Cp by pushing buoyancy into the bows, but the emprirical evidence at the moment is that it isn't going to be fast. When you sail a fine bow boat, TT for instance, you can see the bow slicing through with almost no bow wave generation. On a Nethercott, with a much fuller bow, you can see and feel the mound of water its pushing in front of it. I presume that means a longer wave system, which is my understanding of the advantage of CP, but better not to kick up the wave system in the first place.

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Thanks ARE, Daniel and IC Nutter. This is all very interesting.

 

And this is a picture of my t-foil attempt. I think part of the problem was simply poor craftsmanship. The adjustment mechanism was very crude so it was difficult to accurately dial in the right aoa.

 

 

But I bet it is a good brake!

 

Dr Curry would be proud.

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Thanks ARE, Daniel and IC Nutter. This is all very interesting.

 

And this is a picture of my t-foil attempt. I think part of the problem was simply poor craftsmanship. The adjustment mechanism was very crude so it was difficult to accurately dial in the right aoa.

 

I was hoping this discussion might work its way around to something I understand a bit more! Foils? Poor craftsmanship? Count me in!

 

It's only a matter of time before someone sticks one on the daggerboard also. There are certainly enough old hulls around.

 

I still don't understand why the I14s put the foil so shallow unless there is an upward component to the flow there. Seems like that benefit would be less on a canoe.

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Chris

How much of a ballache was it to build that swinging up rudder box? What bearings and shafts did you use? And did you take the control system up through the shaft?

Dan

 

Ballache. I'd never heard that. Yes those swing up rudder boxes are a bit of one. The shaft is carbon with SS bearings bonded on and Delrin bearings in the box. Yes, the control cable - an old outboard throttle cable - runs up through the shaft to a jack screw connected to the tiller extension. I could hardly have built a system with more friction.

 

 

atg: I think you are right - Bieker reckons there is some upward flow out past the 14 transom and so plants the foil in it. I can see now that's probably not the case on the IC. Also it seems like there would be less junction drag with the foil at the bottom of the rudder.

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It seems that IC designers might want to look into Eugene Clements stepped planing hulls. Mainly because of the very small step and large drag reduction. I talked to Clement and he thought that such an application might be possible for a sailing dinghy. He is "approachable" and you can discuss it with him. The step could be easily retractable(easier than the one on Hydroptere.ch) and that's not the problem: the problem which needs research is the portion of the hull aft of the step. His system also uses a t-foil on the back end. See the booklet below....

Also, I'm posting a paper done to show how to build a rudder T-foil for the Skate class that may include some usefull material.

 

Unfortunately, the Eugene Clement booklet was too big for this form(geez!). If you want to take a look e-mail me and I'll send it to you. douglord AT cfl DOT rr DOT com

hydro-foilingrudder for Skate.pdf

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Bieker reckons there is some upward flow out past the 14 transom and so plants the foil in it. I can see now that's probably not the case on the IC.

 

I wonder... It would be a serious piece of work to monitor the water flow around the hull and its something I've never given enough thought to. I've been guilty of blithely talking about pressure recovery without thinking about where the energy is, how the water is flowing and so on. The water flow round a shallow fat boat must be different to that round a deep thin one. A thought experiement suggests that a thin boat will tend to push the water aside and a fat one tend to push it down, with Newton providing a corresponding push up on the hull. So far so good.

 

I think a bit about the waves generated as the hull moves along, because it seems to me at most sailing speeds they probably represent more drag than skin friction. I could easily be wrong of course.

 

My understanding of Bieker's orginal T foil theory was that there was energy kicking up a stern wave, and if you stuffed a foil in it you could get some back. That kinda matches with my theorising about wavemaking, and especially my thoughts above about bow wave generation. OTOH from what I can make out more recent thinking in the 14s is more on the lines of it being more efficient to push the boat out of the water (and reduce wavemaking) with a fully immersed foil with a 6:1 aspect ratio than it is to do so with a surface riding foil with 1:6 aspect ratio (the hull!).

 

I wonder where there's energy to be recovered behind a canoe hull, and how you'd need to orient the foils to get most out of it...

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FWIW, Bolger liked to encourage thought about where high and low pressure areas were along the hull as it moved through the water, as flow tends to go from high to low pressure. Which kind of begs the question about the Reynolds Number of flow across chines. I've wondered if this is one of the positive synergies surrounding a roundish hull with high chines.

 

Paul

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Another consideration on the 14 is that the foil reduces the stern wave due to the low pressure area above the foil literally flatening the free surface. I would immagine that a boat with as big transom as a 14 would normally create an appreciable amount of it drag from the stern wave so reducing it would make the boat really slippery. you add to the fact (as someone pointed out) that a 14 has a fairly ridiculous amount of sail and is pretty heavy for it's length so the pitch stabilising/control ehancement of the foil is also fast both in the sense that pitching boat is slow and the sense that a crashing boat is slow. OTOH a canoe is much more slender realtive light for it's length boat so the stern wave probably contributes a much lower fraction of the total drag so mashing it down doesn't reduce your drag as appreciably. In addition the canoe is way more sensibly rigged and naturally less prone to pitching so the pitch and crash reduction effect of the foil is also decreaed so it isn't surprising that the foil doesn't so obviously pay on a canoe.

 

Regarding what is planing the persn who pointed out that the Hobie doing 15 knots isn't planing while the 470 doing it is is completely correct. It isn't just about Froude numbers but the flow around the hull.

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Another consideration on the 14 is that the foil reduces the stern wave due to the low pressure area above the foil literally flatening the free surface. I would immagine that a boat with as big transom as a 14 would normally create an appreciable amount of it drag from the stern wave so reducing it would make the boat really slippery.

 

I'm not sure this is quite correct. The stern wave does not cause drag, it's just the part of evidence that drag is being created. In a sense, the bow wave is the thing the hull uses to get the water to flow around the hull and stern wave is the thing the hull uses to recover some of the energy lost creating the bow wave. The hull surfs the stern wave. I think the idea is that the foil also surfs in the stern wave to recover more energy. Yes, the effect may be that the stern wave gets a bit flatter as you extract energy from it, but it's not something you would set out to do because reducing the size of the stern wave would be counterproductive. If you could, you would want to have a bigger stern wave.

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This thread is awesome, but it does make me feel like a complete meathead. I sometimes enjoy it a bit more after some scotch. Then, I don't try to understand, I just let the visions flow around me (in a semi-displacement mode, I might add). But...if I'm reading this correctly...it's telling me not to bother to add a T-foil to the rudder on my new boat.... yet.... right?

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as a wannabe newbie - I'd say if you're sailing in SF and have boat control issues, it might be pretty handy, but they haven't figured out how to mate a rudder foil/hull combo. The 14 system is pretty well refined these days, and they mostly use swinging gantries, not sure how that'd work….

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I found this thread by searching on "planing hull shape sailing anarchy," I was hoping to find information for use in my planned design and build of an A-class cat. As I read through the posts from the beginning my thoughts evolved as follows:

 

1.
I might find something in this thread useful to my A-class cat design.

2.
IC's are very odd boats.

3.
I am disappointed not to find more discussion about planing hulls.

4.
I am amazed by how much the photos of pointy DC's resemble both skeeter ice boats and miniature speed record proas based on the full sized Crossbow I and Slingshot.

5.
These DC's are an interesting class.

6.
These DC sailors are an amazingly helpful and friendly bunch. (unusual on SA)

7.
DC's are amazingly fast for their size and sail area.

8.
DC's are much simpler to build than A-class cats.

9.
I might build a DC as practice for my upcoming A-class build.

10.
This thread has lots of great technical information.
11.
I start to design a DC.

12.
I print my design and build a paper model at 1/16
th
scale.

13.
I design 2 more DC's and build 2 more paper models.

14.
I am definitely going to build a DC.

15.
I might try to charter an IC to race this summer in at least one regatta.

16.
I'm spending way too much time reading DC posts and researching IC's.

17.
DC's are easier to store than A-class cats.

18.
DC's are easier to transport than A-class cats.

19.
DC's are cheaper to build than A-class cats.

20.
I've become addicted to reading DC posts.

21.
I don't think I'll build an A-class cat.

 

By now you can probably tell that I've had way too much IC Kool-Aid.

By the way, thank you all for your great posts!

 

 

Oh yes, back to reality. Where can I find the US IC regatta schedule for 2012 and how can I go about chartering a boat for one of them?

 

 

Just one more IC nut case, Teejay

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Some more belated answers:

Steve (post 2086): Good argument, we are back on the same wavelength. The trouble with narrow stern and foil rudder will again be handling, Just as Andy P found the aft deck was too narrow to tack from. Maybe the topsides could be flaired out, pin tail on the chines and wider on the deck.

 

General: Adjustable T foil rudders are now on all all moths and systems refined so canoe replication is not difficult. Rules require centre board and rudder to be retractable abover the keel, so rudder would need to be hung off stern not inserted up a trunk.

 

ARE (post 2087): Spring = rocker = banana = keel longitudinal curviture and in my perception to be especially minimised in aft half of boat.

CoB for an IC follows the crew about as he weighs close to double the rest of the boat.

 

Transition: or Hump. Known to most who sail heavy boats or boats with lots of spring (needed to float lots of weight). Not known to people who sail narrow, light boats with little spring (because they do not need it to carry excess weight). Its the sensation observed when the boat seems to climb over its bow wave and start to plane. A lot of boats stagger for a while and need an extra bit of wind to get going, hence the term "hump". Of the first generation of DC/ICs we had at McCrae, which many of us sailed after the event, only Chris' boat and mine showed no tendency to lift the bow and accellerated without any observable climbing over the boaw wave, just like a cat. These two boats had the narrowest bows and the least spring by my observation (not by measurement). This is not conventional displacement or planing and does not comply with old theories. I am sure that Steve and others have achieved the same result with subsequent designs.

 

Before foils an 11ft Moth hull would do a max of about 17kts before hitting the wall, thats without lifting up or planing, this is about 3 times the speed the displacement theory says is possible. The very lightest people could get them to plane but they never went any faster. ACats are longer and go to about 23kts (IIRC), again faster than the theories say they should. The IC is only slightly shorter than an A so should reach similar speeds without planing if the bow is pointy enough and the rest of the design is right. They have already proven light enough and narrow enough, but design progress is not fast as there are too few people working on it and there is only one real competitive regatta every 3 years. This does not give justice to the great class and the very clever people who are active it it.

 

So stop tapping your key boards and start building.

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My IC TT was a narrow pintail - influenced by lowrider moth trends.

Originally it had a fixed seat, using the T foil rudder to control trim angle - this was Ok in breeze, but there wasn't enough lift to support my weight at the back in light winds. The pintail was supposed to mean it didn't matter about the aft immersion - but it was a bit slow in the light stuff.

When modified to have fore/aft seat movement and a wider working deck it was much better, and had excellent speed - and as Jim says, slicing the water instead of pushing it out of the way.

The T foil wasn't really needed with the moving seat, and actually reduced top speed, and it was slower in general when using it.

The hull shape was low rocker, but also flat sideways - it would have been better with much more shape in the bottom for the highspeed displacement mode that it sailed in most of the time.

The unarig with camber-inducers was fast, but not practical for rigging and sometimes it was impossible to even launch in a strong wind.

 

The boat has been chopped again, losing 3 feet of the small pointy bit at the back, so is a more skiffy shape now, and using a larger T rudder which is very effective - more effective on the shorter boat - it lifts the back to keep the bow in upwind, let off it stops nosediving downwind. The rudder is on a canting gantry.

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The boat has been chopped again, losing 3 feet of the small pointy bit at the back, so is a more skiffy shape now, and using a larger T rudder which is very effective - more effective on the shorter boat - it lifts the back to keep the bow in upwind, let off it stops nosediving downwind. The rudder is on a canting gantry.

 

 

Hey Andy,

Can you see any performance change with the pointy stern gone and the T foil on? Speed changes that is.

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I found this thread by searching on "planing hull shape sailing anarchy," I was hoping to find information for use in my planned design and build of an A-class cat. As I read through the posts from the beginning my thoughts evolved as follows:

 

1.
I might find something in this thread useful to my A-class cat design.

2.
IC's are very odd boats.

3.
I am disappointed not to find more discussion about planing hulls.

4.
I am amazed by how much the photos of pointy DC's resemble both skeeter ice boats and miniature speed record proas based on the full sized Crossbow I and Slingshot.

5.
These DC's are an interesting class.

6.
These DC sailors are an amazingly helpful and friendly bunch. (unusual on SA)

7.
DC's are amazingly fast for their size and sail area.

8.
DC's are much simpler to build than A-class cats.

9.
I might build a DC as practice for my upcoming A-class build.

10.
This thread has lots of great technical information.
11.
I start to design a DC.

12.
I print my design and build a paper model at 1/16
th
scale.

13.
I design 2 more DC's and build 2 more paper models.

14.
I am definitely going to build a DC.

15.
I might try to charter an IC to race this summer in at least one regatta.

16.
I'm spending way too much time reading DC posts and researching IC's.

17.
DC's are easier to store than A-class cats.

18.
DC's are easier to transport than A-class cats.

19.
DC's are cheaper to build than A-class cats.

20.
I've become addicted to reading DC posts.

21.
I don't think I'll build an A-class cat.

 

By now you can probably tell that I've had way too much IC Kool-Aid.

By the way, thank you all for your great posts!

 

 

Oh yes, back to reality. Where can I find the US IC regatta schedule for 2012 and how can I go about chartering a boat for one of them?

 

 

Just one more IC nut case, Teejay

 

Umm, so who's going to tell him? See there's only three of us here posting under a bunch of different names. None of us actually sails, we just talk about it.

 

Really there aren't many IC's in the US and no real schedule. The East coast and West coast guys sail at some local regattas and every once in a while we get together and sail for some ancient hardware at the Canoe Association's island. There's some IC action starting in Texas too. They sound like a rowdy bunch, approach with caution. It's fairly freeform and much like herding cats for someone trying to organize this, er, eccentric group.

 

Your best bet is coming to Richmond next summer to try out a boat and sail with us. I hope to take a new boat down there to test at some point in the summer.

 

If you start building by the end of summer you might finish your boat and learn to sail it before the SF Bay worlds in 2014. This would be an exception to the norm of people finishing their boats on the way out to the first race and would give you a huge advantage.

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haha

 

I've been at RYC most sundays of the last couple months(kid in Jr program) - packing my wetsuit - but we literally have had 0 wind for 2 1/2 months.

 

One of these days I'll get a shot at capsizing one of these things.

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I found this thread by searching on "planing hull shape sailing anarchy," I was hoping to find information for use in my planned design and build of an A-class cat. As I read through the posts from the beginning my thoughts evolved as follows:

 

1.
I might find something in this thread useful to my A-class cat design.

2.
IC's are very odd boats.

3.
I am disappointed not to find more discussion about planing hulls.

4.
I am amazed by how much the photos of pointy DC's resemble both skeeter ice boats and miniature speed record proas based on the full sized Crossbow I and Slingshot.

5.
These DC's are an interesting class.

6.
These DC sailors are an amazingly helpful and friendly bunch. (unusual on SA)

7.
DC's are amazingly fast for their size and sail area.

8.
DC's are much simpler to build than A-class cats.

9.
I might build a DC as practice for my upcoming A-class build.

10.
This thread has lots of great technical information.
11.
I start to design a DC.

12.
I print my design and build a paper model at 1/16
th
scale.

13.
I design 2 more DC's and build 2 more paper models.

14.
I am definitely going to build a DC.

15.
I might try to charter an IC to race this summer in at least one regatta.

16.
I'm spending way too much time reading DC posts and researching IC's.

17.
DC's are easier to store than A-class cats.

18.
DC's are easier to transport than A-class cats.

19.
DC's are cheaper to build than A-class cats.

20.
I've become addicted to reading DC posts.

21.
I don't think I'll build an A-class cat.

 

By now you can probably tell that I've had way too much IC Kool-Aid.

By the way, thank you all for your great posts!

 

 

Oh yes, back to reality. Where can I find the US IC regatta schedule for 2012 and how can I go about chartering a boat for one of them?

 

 

Just one more IC nut case, Teejay

 

Umm, so who's going to tell him? See there's only three of us here posting under a bunch of different names. None of us actually sails, we just talk about it.

 

Really there aren't many IC's in the US and no real schedule. The East coast and West coast guys sail at some local regattas and every once in a while we get together and sail for some ancient hardware at the Canoe Association's island. There's some IC action starting in Texas too. They sound like a rowdy bunch, approach with caution. It's fairly freeform and much like herding cats for someone trying to organize this, er, eccentric group.

 

Your best bet is coming to Richmond next summer to try out a boat and sail with us. I hope to take a new boat down there to test at some point in the summer.

 

If you start building by the end of summer you might finish your boat and learn to sail it before the SF Bay worlds in 2014. This would be an exception to the norm of people finishing their boats on the way out to the first race and would give you a huge advantage.

 

 

:lol:

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Dat's some good stuff cmaas!

As one of those rowdy texas ICers, I applaud you!, and since mine came fron ryc, I feel like one of the bunch.

Seriously 'tho, would like to come out to try a new rules boat some day, maybe next summer?

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I was interested to see Steve Clarks new design. Looks good, as indeed one would expect from Steve. The pics show bow trimed down and stern trimmed down. I assume that the designed trim is somewhere between the two. They show well the design elements for good semi planing and planing performance. I would hazard a guess that there is maybe 2 inches of rocker, not much more? So that the speed Range over which the hydrodynamic lift is negative ( suction) will Kept to a minimum. Guess the stern will be Submerged 1 or 2 inches In 'normal' sailing trim. With bow trimmed down the prismatic coefficient will be low for good displacement sailing performance. When trimmed down at the stern the effective rocker is almost zero, and the underwater profile is almost exactly that which Savitsky shows as typical well designed planing boat. I would guess that in this trim the prismatic coefficient is upwards of 0.7. The important thing is that it is variable though moving the helms mans weight, and as somebody said recently on the thread, the C of G follows the helms weight as he will contribute the major part of the weight.Chris- I have to admit you might be right, well about me anyway. I haven't sailed a canoe for several years now, but am hoping to rectify that ASAP.

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I found this thread by searching on "planing hull shape sailing anarchy," I was hoping to find information for use in my planned design and build of an A-class cat. As I read through the posts from the beginning my thoughts evolved as follows:

 

1.
I might find something in this thread useful to my A-class cat design.

2.
IC's are very odd boats.

3.
I am disappointed not to find more discussion about planing hulls.

4.
I am amazed by how much the photos of pointy DC's resemble both skeeter ice boats and miniature speed record proas based on the full sized Crossbow I and Slingshot.

5.
These DC's are an interesting class.

6.
These DC sailors are an amazingly helpful and friendly bunch. (unusual on SA)

7.
DC's are amazingly fast for their size and sail area.

8.
DC's are much simpler to build than A-class cats.

9.
I might build a DC as practice for my upcoming A-class build.

10.
This thread has lots of great technical information.
11.
I start to design a DC.

12.
I print my design and build a paper model at 1/16
th
scale.

13.
I design 2 more DC's and build 2 more paper models.

14.
I am definitely going to build a DC.

15.
I might try to charter an IC to race this summer in at least one regatta.

16.
I'm spending way too much time reading DC posts and researching IC's.

17.
DC's are easier to store than A-class cats.

18.
DC's are easier to transport than A-class cats.

19.
DC's are cheaper to build than A-class cats.

20.
I've become addicted to reading DC posts.

21.
I don't think I'll build an A-class cat.

 

By now you can probably tell that I've had way too much IC Kool-Aid.

By the way, thank you all for your great posts!

 

 

Oh yes, back to reality. Where can I find the US IC regatta schedule for 2012 and how can I go about chartering a boat for one of them?

 

 

Just one more IC nut case, Teejay

 

Mountain Cat

 

There are four A Cats in Colorado, one of them I used to own. It was so hard to move it around and not bump it into things (all rocks, no grass or sand in Utah) so I decided to go with a Moth. An IC would be another good choice.

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So anybody want to spill the beans on the magic 1/2 entry angle for an IC bow that slices?

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Which fleet/ country does this Savitsky bloke sail with? I haven't seen his name in the results...

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Savitsky sailed against a bloke named Prandtl. Bar talk was intense.

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So anybody want to spill the beans on the magic 1/2 entry angle for an IC bow that slices?

 

Seven degrees.

 

 

Really? This is most excellent.

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So anybody want to spill the beans on the magic 1/2 entry angle for an IC bow that slices?

 

Seven degrees.

 

I thought optimal planing angle was four degrees for a flat surface? I guess more would make sense for a less planar surface.

 

I keep thinking a sharp corner at the knuckle is a mistake though, mostly because of what it does to the wetted surface when it touches the water at speed.

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Chris, is 7 degrees, in your practical experience, a bright line?

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So anybody want to spill the beans on the magic 1/2 entry angle for an IC bow that slices?

 

Seven degrees.

 

I thought optimal planing angle was four degrees for a flat surface? I guess more would make sense for a less planar surface.

 

I keep thinking a sharp corner at the knuckle is a mistake though, mostly because of what it does to the wetted surface when it touches the water at speed.

 

 

ATG, I was asking about planform, not profile. (7 degrees was for planform, wasn't it Chris?) 7 degrees agrees pretty closely with Navy tests of bow waves on destroyer bow 1/2 angles, iirr, the one I'm thinking of came up with 7.5 degrees, didn't know if a sailboat hull would be close to a motorboat hull or no. Destroyers have a lot of flatish surfaces.

 

Paul

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So anybody want to spill the beans on the magic 1/2 entry angle for an IC bow that slices?

 

Seven degrees.

 

I thought optimal planing angle was four degrees for a flat surface? I guess more would make sense for a less planar surface.

 

I keep thinking a sharp corner at the knuckle is a mistake though, mostly because of what it does to the wetted surface when it touches the water at speed.

 

 

I'm thinking Amati was asking for the waterline angle not the keel.

 

Interestingly, to me anyway, my keel is at about 2 degrees at the mast when trimmed bow up for what I thought until a couple of days ago was planing. This seems about right - trimmed for minimum drag rather than max lift in semi planing mode.

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Dat's some good stuff cmaas!

As one of those rowdy texas ICers, I applaud you!, and since mine came fron ryc, I feel like one of the bunch.

Seriously 'tho, would like to come out to try a new rules boat some day, maybe next summer?

 

 

Hey Ortega, & Mt. cat.

We'd Love to show you what all the talk is about.

We're around just about anytime you can make it .So send me a PM, fill up the tank or call Southwest airlines.

Chris, when next er ...ah.. this season are you expecting. Maybe we should try for a Clan Gathering.

Cheers

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New Moon concaves legal? 7 degree 1/2 entry (yes Chris you are correct sir) does typeform things a bit....

 

Paul

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Hey Ortega, & Mt. cat.

We'd Love to show you what all the talk is about.

We're around just about anytime you can make it .So send me a PM, fill up the tank or call Southwest airlines.

Chris, when next er ...ah.. this season are you expecting. Maybe we should try for a Clan Gathering.

Cheers

 

 

Del: I don't really know. I built myself a hull while the mold was in the shop for Simon's boat but I probably won't have time to finish it for a couple of months. So maybe mid Summer?

 

Paul: Your references are almost always too damn obscure for my meager education! So I'll ignore "New Moon" and say that concaves up to 100mm are legal except for a part of the rule I can't remember about concaves near the BMS. But, if your'e talking about concave waterlines in the bow, the water will love your concave at first but then hate it when it stops looking so streamlined. Is it a net wash? Maybe, especially if it minimizes the slowing effect of wave encounters.

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Dat's some good stuff cmaas!

As one of those rowdy texas ICers, I applaud you!, and since mine came fron ryc, I feel like one of the bunch.

Seriously 'tho, would like to come out to try a new rules boat some day, maybe next summer?

 

 

Hey Ortega, & Mt. cat.

We'd Love to show you what all the talk is about.

We're around just about anytime you can make it .So send me a PM, fill up the tank or call Southwest airlines.

Chris, when next er ...ah.. this season are you expecting. Maybe we should try for a Clan Gathering.

Cheers

 

Hey Del - I'll be there Sunday yet again tending the kids, wetsuit in the truck. Will this high pressure system move a bit?

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...what I thought until a couple of days ago was planing.

 

I don't doubt that even new wave ICs at speed have as much support from dynamic lift as more conventional dinghies, so by any sailor's definition they must be planing. But I think (FWIW) one of the features of our interesting design space and the way you clever folks have exploited it is the way the boats get there. If you take a traditional shape dinghy, maybe something like a Laser, it seems to pile up a bigger bow wave until it gets to a point where it can blast through that and into a dynamically supported mode. By contrast I reckon the modern canoes are making a much subtler and more elegant transition. Instead of they are slicing through what wave system they generate, with the dynamic lift steadily increasing with speed...

 

In the second Bethwaite book seems to be saying that he's found evidence that his designs have the peak in the drag curve, but with different trim it occurs at different speeds, so with optimum trim its avoided. It would be interesting, I think, to measure the dynamic lift created at the different trim angles and see how that relates. I don't see how you could do that outside avery throughly instrumented tow tank. But were you able to perform that exercise both with a 49er hull and a modern Canoe hull, I suspect you'd find that the detail of how lift, form drag and all the rest of it interact and vary with speed are quite different. But I'm only guessing here. It would be a fascinating research project (fascinate me anyway) but my oath it would be expensive... You'd probably spend tens of thousands just making the hardware that would be needed to be able to support and instrument real boats in the towtank...

 

Dear Mr Ellison, you've been there and done that with the America's Cup now... How do you fancy doing some fundamental research?

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Chris, after spending way too much time on the web looking for GOOD pics, I found the following:

 

http://www.tremolinotri.com/tgullspec.htm

 

The top of the brochure has a minimal body outline, but gives you the general idea.

 

Newick had been looking at some windsurfers (the Alpha Race, which had concave rails (and I actually owned one) among them, and developed the new moon outriggers based on the idea. Ocean Surfer also had them- Mark Rudiger liked them, but even though OS was succesful, I can't find any good pics or drawings that clearly show the ama shapes on the web. Anyhoo, the idea was dynamic lift at speed so you augmented daggerboard lift or you could retract your foil completely, like on a shy reach. The Alpha Race had 2 daggerboards as a result, one big for light air, and one little one was for above 10K or so and looked way too high AR, but with the rails, it worked. It was the end of the longboard era, though, so the idea wasn't refined.

 

Paul

 

Oh hell, it's a nice pic of OS, even if it doesn't show the shape of rge AMA, you do get an idea of the dynamics;

 

 

http://www.wingo.com/newick/oceansurfer1-l.jpg

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Jim,

Building a few 100% size canoe hulls and sailing them would be much more fun than building some 50% scale tank test models and paying for some boffins to tell you a whole lot of gobbledygook about how they might sail if you were to build them full size. You might save a considerable amount of money too as well as have some other boats to sail against.

(sorry the forum will not let me post a Flickr photo and I can not find another one. You can view it here: IMGP0987)

This is the best photo of Hollow Log I can find. I am out on the seat going upwind in a moderate wind. The boat is going reasonably fast as seen by the bow wave climbing up the topsides, but the bow has not lifted at all and hence my assertion that it is going through the water like a cat rather than lifting over it like a skiff. Its the same at any speed and in fact I only ever moved the seat back when I feared nosediving downwind in strong winds and waves, never to raise the bow into planing mode. It never seemed to go any slower if hard pressed and trimmed bow down. You can see that the seat does not move aft much anyway. Also backs my argument about less need to move aft on narrow sterned boats.

 

Amati,

Hollows under gunwales laser fashion are for construction ease and casue huge windage and wave drag. Hollows in the waterlines, as Chris says make the water angry. Hollows near measurement points are for rule cheating and Steve did his very best to prevent these when writing the IC rules. So forget about hollows in IC design with one exception, and that is to get the chainplates as wide as you can to support the mast, Common a most new ICs and something I tried to prevent with the unstayed mast, but which proved to be inadequate for upwind performance.

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building a few 100% size canoe hulls and sailing them would be much more fun than building some 50% scale tank test models

For sure. I was thinking about tank testing real operational boats:-)

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Dat's some good stuff cmaas!

As one of those rowdy texas ICers, I applaud you!, and since mine came fron ryc, I feel like one of the bunch.

Seriously 'tho, would like to come out to try a new rules boat some day, maybe next summer?

 

 

Hey Ortega, & Mt. cat.

We'd Love to show you what all the talk is about.

We're around just about anytime you can make it .So send me a PM, fill up the tank or call Southwest airlines.

Chris, when next er ...ah.. this season are you expecting. Maybe we should try for a Clan Gathering.

Cheers

 

Hey Del - I'll be there Sunday yet again tending the kids, wetsuit in the truck. Will this high pressure system move a bit?

 

Mitch

I'll be there around 10. looking out the window the HS CFJs are enjoying an nice 6-8kn , perfect for a 1st IC ride.it's supposed to be a bit colder on Sunday.

Cheers.

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Jim,

Building a few 100% size canoe hulls and sailing them would be much more fun than building some 50% scale tank test models and paying for some boffins to tell you a whole lot of gobbledygook about how they might sail if you were to build them full size. You might save a considerable amount of money too as well as have some other boats to sail against.

(sorry the forum will not let me post a Flickr photo and I can not find another one. You can view it here: IMGP0987)

This is the best photo of Hollow Log I can find. I am out on the seat going upwind in a moderate wind. The boat is going reasonably fast as seen by the bow wave climbing up the topsides, but the bow has not lifted at all and hence my assertion that it is going through the water like a cat rather than lifting over it like a skiff. Its the same at any speed and in fact I only ever moved the seat back when I feared nosediving downwind in strong winds and waves, never to raise the bow into planing mode. It never seemed to go any slower if hard pressed and trimmed bow down. You can see that the seat does not move aft much anyway. Also backs my argument about less need to move aft on narrow sterned boats.

 

Amati,

Hollows under gunwales laser fashion are for construction ease and casue huge windage and wave drag. Hollows in the waterlines, as Chris says make the water angry. Hollows near measurement points are for rule cheating and Steve did his very best to prevent these when writing the IC rules. So forget about hollows in IC design with one exception, and that is to get the chainplates as wide as you can to support the mast, Common a most new ICs and something I tried to prevent with the unstayed mast, but which proved to be inadequate for upwind performance.

 

 

Actually not looking for a rule cheat. With chines below the water, and flare starting above the water line more at the point of max beam, as long as you're not narrower than 30, narrower than 44" it's ok, I think. Aren't any combo of hollow etc allowed as part of the beam in cross section? Which is how I understand the rule. Could be wrong. At the bow and stern, there would be no flare, and the hollow would only be engaged when heeled or going through waves. Kind of a big bump. The board was about 8" thick at midpoint.

 

Always liked the way the Alpha went through waves upwind. The feel was good. And it was fast. Anyway it's beyond my non epoxy skills right now to do such a thing. Right now. I think there's a way to do it, but it would take a commitment with a healthy lead time. So getting feedback is part of the plan. If 2014 is a heavy air affair, perhaps different flow management might be cool? My D2 was almost pointless in the Bay back in the 80's. The Alpha Race rocked.

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http://www.scribd.co...-Hull-Forms-1-1

A good paper on semi planing / planing etc.

I think possibly doesn't capture the effect of l/b in semi planing regime enough - mainly because it is tough to compare apples with apples - change l/b (at const length and displacement in most sailboat cases), slenderness ratio changes, transom immersion changes etc. Esp in a monohull centric paper, where high l/b is beyond what is acceptabl for initial stability and interior volume

 

Re pointy transom canoes.- the canoe is a pretty quick sailboat - it is fairly constantly in the semi displacement regime, and nudges the planing regime a decent bit.

Minimising hull drag is a case of maximising l/b (done - rise of floor rule)

reducing buttck curvature (generally pretty straight - no real penalty for transom immersion at lower speeds unless cutoff is very agressive)

Whilst tapered, the transom is still a transom, so will run dry from 5 ts ish upwards, which is good.

 

At higher semi displacement speeds (so 8kts and upwards for your 17' canoe) then you almost can't have too much prismatic (fullnes in ends - kids the bow and stern waves into thinking the boat is longer)

And for minimal resistance your LCB needs to be well alft - up to 12% of length.

 

Both of the last two points can't really be done if you have a skinny stern.

 

To be truly planing in a canoe you need to be doing 15kts, which I reckon realistically happens for what, 5% of the time around a course over a range of windstrengths - as such isn't really a design case.

 

As such the modal design case for the IC has to be an overdriven semi displacement hull - straight buttocks, immersed transom, approx half of midship sectional area, high Cp, LCB way aft, small entry angle as possible within first constraints.

Design a pure planing craft or pure diplacement vessel, and you will be slower most of the time.

 

I am not convinced that an IC hull optimized for early planning would not be fast in most conditions. Yellow Pages/Macquarie Innovation and the Vestas Sailrocket both use planing hull shapes in their hull pods to achieve speeds over 47 knots; so the high speed potential of planing hulls is certainly there. Formula sailboards are similar in size, weight, sail area and typical expected sailing conditions to new rules ICs. Comparing the sail to weight ratio of a Formula Experience sailboard to a new rules IC with a 75kg helm we get:

 

FE Big Rig: 11.0 m2/ 75 + 15 kg = 0.122 m2/kg

FE Small Rig: 7.8 m2/ 75 + 15 kg = 0.087 m2/kg

New Rules IC: 10.0 m2/ 75 + 50 kg = 0.080 m2/kg

 

So the IC appears to be in a similar power to weight range at least in high winds when the FE uses the small rig. Another way to look at this data is to observe that the IC is underpowered in light winds and could use a larger light wind sail plan!

 

Of course the comparison above is apples to oranges. The Formula board is likely more efficient than an IC in the following number of ways:

 

  • Canted rig
  • Sleeved mast
  • Bottom of sail closed off with an effective end plate
  • Single foil with size and shape optimized for wind speed
  • The majority of weight is isolated from hull wave shock by the sailors legs

My questions are as follows: Are these Formula board advantages so great that their optimized hull shape has no application to a new rules IC design? Are there no hull shape ideas that can adopted from the optimized Formula board design to IC's? The fastest Formula boards have settled on an optimized design with a width of 1000 mm, a dead flat tail section out to hard chines, little to no tail rocker and sometimes with a cutaway step within 300 mm of the tail. IC's have one advantage over Formula boards in that they have no concern for rocker and rail shapes that facilitate sailor initiated turns by leaning.

 

 

 

 

Formula board bottom shape shown above.

 

Formula boards seem to have a very narrow semi-planing wind range. They go from displacement mode at about 6 knots wind speed to what seems to be a fully planing mode at about 9 knots wind speed. The velocity change through the transition is rather amazing as the board speed can go from about 4k up to as high as 16k with a wind increase from 6k to 9k. The speed transition to "planing speeds" is often assisted by the sailor pumping the sail. The large change in board speed over a relatively small change in wind speed seems to me to be evidence that the board is making a clear "break from one regime to another."

 

Has any one tried building an IC with a Formula sailboard type stern? That is: dead flat cross-sections out to the hard chine and a straight keel at the stern (no rocker). Of course such a design would have a much greater wetted surface and would be slow in low winds just as Formula boards are. Low wind speeds <7k might be accommodated in such an IC design by heeling the IC 30 degrees to leeward in light winds to reduce wetted surface in a similar fashion to how inland scows are sailed.

 

I don't see any reason why an IC optimized for early planing can't fully plane in 9k of wind with the right (bigger) light air rig.

 

My IC designs to date for my upcoming build all feature dead flat cross-sections out to hard chines at the stern, stern widths between 900 and 1000 mm and no rocker or keel curvature in the aft half. What do you think are the chances that such a design might be fast?

 

M-Cat

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Hey foils - Del finally got me out there today - day was cold, puffy, and so I was a bit apprehensive but we got her out - Del coached me through some maneuvers perched somehow on the back of the boat and we got it out and about. Was a bit too much in conditions for me to solo but how nice a ride. I really like these boats.

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Mcat,

Interesting post. Yep for sure, for "real" high speed planing is the only way. better than foiling if you ignore motions/accelerations.

Guess you could look at this in a couple of ways.

If you put a 10m2 sail on a formula board and added 50kg of ballast on it to bring it to canoe's min displacement, you'd be a 125kg guy trying to get a 10m sail planing. Ignoring the fact that you'd probably need to extrude the board upwards to fulfil freeboard rules, and all the drag that would entail, then I reckon you'd be looking at 12 kts before you're planing. Once planing, I expect that you'd be quick all round the course. Until that point, you'd be horrifically slow. Like doing 4 kts while everyone else was doing 9 or something.

Id love to see it done but it'd be risky and you'd only want to race in a good f4 +.

 

The thing is, if you look at the back third or so of say Chris maas' boats, you'll notice that there is little curvature in section or buttock, with a nice sharp chine, I.e not really so different to the formua but a little wider. And with a nice long boaty front on it.

 

If limited by sail area, and having to sail in any wind strength, then I am pretty sure that on balance an IMCO or modern equivalent would be quicker than a formula. Certainly better than rsx

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I feel like an IC built for full-on plane mode might be a way for a light guy to bet the house on a certian condition and do really well. But I'm only saying that because I think it'd be sweet for someone to try it. Personally...this fatass will count on leverege to generate speed in a blow.

 

Unfortunatly, a fast hull still entails being able to tack successfully. I'll keep working on it.

 

Mitch, congrats and welcome to the club!! If you want to compete against another scrub, I think I'll be up in the Bay area this week/end.

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If I remember correctly the IC Worlds regatta has a 20kt limit. My only experience was at McCrae and the only day it kicked we were sent home. Some were struggling, Steve seemed to be enjoying it. A few needed rescuing. Its probably a reasonable limit for such a big unweildy single hander in open water. So serious reduction in % of planing weather.

 

The Formula boards do not bother rigging in under 10kts and are dead slow until they plane, much slower than a foiling moth off its foils, which (although I differ) Steve once said was Opi fodder. I doubt a full on planing canoe would be a goer in the light stuff especially if its 1m wide when the rule allows it to be as narrow as 750mm.

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Sad. Ben Krothe (spelling? Can't remember) used to relish making the point that when there was too much wind for the Moths, the boys would bring out the IC's. Pre early eighties.

 

FWIW, the formula shapers have a rule of thumb of SA in sq meters = width of board in cm. But formula boards are beginning to have some v in the tail, rather than concave. Retro diamond tails anyone?

 

Paul

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CM :Perhaps not faster than a FB but fast enough?? Looks like you're about to push out and light the fires.

 

Mcat; do you have anything on paper or evlctronically that you can share yet? Most of us don't bite.

 

Mitch; good job. nice sailing with you , just wait til you solo. it goes to show that you can have 145kg on a new rules IC , Just much quicker with less.

Cheers

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Hey foils - Del finally got me out there today - day was cold, puffy, and so I was a bit apprehensive but we got her out - Del coached me through some maneuvers perched somehow on the back of the boat and we got it out and about. Was a bit too much in conditions for me to solo but how nice a ride. I really like these boats.

 

Mitch - Del took you out on Donkey? That's not really starting out on the bunny hill is it? You may be the first person in the world to learn to sail an IC on a new rules boat. Except for maybe Phil S and he raced low rider Moths back in the day so hardly qualifies as merely mortal.

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Referring to what JimC wrote earlier about changing to trim keep the resistance as low as possible, attached is a graph showing roughly what we could expect the resistance curves to look like for an IC in various states of stern down trim. The chart shows three resistance curves for the same hull. The level trim curve we might call the 'displacment trim' resistance, the 1 degree trim curve is the 'semi displacement (or semi planing) trim' resistance and the 2 degree trim curve is the 'planing trim' resistance. It should be obvious that to maintain the minimum resistance you need to progressively trim the hull down by the stern as speed increases. This is probably no great surprise to anyone. What I hope it does show is that if you optimise the hull for the planing regime, you compromises your performance at the lower end of the speed specrum (say sub 15 knots hull speed), which is a large chunk of your normal operating speed range. A hull optimised for planing will likely have higher wetted surface in displacement mode and some 'transom' drag even at level trim.

 

post-3095-016308100 1326679632_thumb.png

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Wow.

 

It's obvious with any planing dinghy that trim is important but I had no idea that differences were this huge over just a 2 degree range. Astonishing, and obviously vastly important.

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Hey foils - Del finally got me out there today - day was cold, puffy, and so I was a bit apprehensive but we got her out - Del coached me through some maneuvers perched somehow on the back of the boat and we got it out and about. Was a bit too much in conditions for me to solo but how nice a ride. I really like these boats.

 

Mitch - Del took you out on Donkey? That's not really starting out on the bunny hill is it? You may be the first person in the world to learn to sail an IC on a new rules boat. Except for maybe Phil S and he raced low rider Moths back in the day so hardly qualifies as merely mortal.

 

Actually - I found the boat to be fairly easy to drive, didn't make a tack work but, ok.

 

Of course, Del was hanging on the back like a turtle telling me what to do…..

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Wow.

 

It's obvious with any planing dinghy that trim is important but I had no idea that differences were this huge over just a 2 degree range. Astonishing, and obviously vastly important.

 

I produced these curves using my spreadsheet, so they could be complete crap. However, if you sit on the transom of your dinghy in two knots of wind dragging the stern, it's likely to be pretty slow, so it might be right.

 

Also, that's two degrees on a Canoe, which might equate to 3 or 4 degrees on a shorter, deeper boat.

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Another thought is that the old one design IC had a practical upper speed limit of around 18 knots. Looking at the photo of Chris Maas above, the newer boats are able to get the carriage much futher aft, allowing the transom to sink further. We may find that in higher winds the old upper speed limit may be geatly exceeded. The basic guide is that for full planing the largest immersed sectional area should be at the 'transom'. I know that on my Nethercott it seems pretty hard to get the bow to lift much downwind.

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Lots of intresting talk about planing or not, and fat or thin transoms,

post-20243-050711500 1326721662_thumb.jpg

this is Dragonfly's wl profile, so I suppose it has a Pin transom? or is it a planning transom? In any event it does seem to plane, and there is a transition stage, its in about a force 2, the bow lifts so that about 8 " of the boat is out of the water and speed increases, so most of the time it seems to be planing, it is quite diffcult to get the bow back down to the water, I have to move the carrage quite far forward and it still does not get back down.. The section is quite square

post-20243-051206300 1326721983_thumb.jpg

this is what it looks like under the mast. she has plenty of rocker, 100mm and its greatest at the mid piont, slightly flatter aft but not much. Working on a new design , not sure where to go at the moment but I think a bit more pointy, but transom really diffcult, it took a long time to design this one! She went quick enough in Germany sepecially in the light to moderate days, I was too wobbly to see how she went when it was windy.

Alistair

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Wow.

 

It's obvious with any planing dinghy that trim is important but I had no idea that differences were this huge over just a 2 degree range. Astonishing, and obviously vastly important.

 

I produced these curves using my spreadsheet, so they could be complete crap. However, if you sit on the transom of your dinghy in two knots of wind dragging the stern, it's likely to be pretty slow, so it might be right.

 

Also, that's two degrees on a Canoe, which might equate to 3 or 4 degrees on a shorter, deeper boat.

Makes sense. I know I can't convert feel to numbers, and in particular couldn't accurately guess how many degrees a trim change is. (I say this because when rotating an image in a photoediting program, I'm often surprised by how much change a very small number of degrees actually is.)

 

Still your point seems extremely important, though well above my present pay grade.

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http://wp.me/pEIzH-hC

 

 

Sent from my iPad

 

Adverts for an amazing number of longboards circa 1990 +-, back when everyone was grappling with boards that were living in displacement, forced and planing mode. The more I looked at the pics, the more the various strategies to deal with the forced mode became apparent. I suppose the most interest to me, as far as IC new rules are the pintails, and the experimentation with diamond tails as far as width of the tail.

Outlines tend to have max beam pretty forward compared to current IC practice.

 

And these boards were NOT light, so displacement/length is kind of in the ballpark for the longer boards.

 

A fun way to spend 1/2 an hour at least. Pretty hardcore. Fun to look at some boards I owned- like the Crits. And the Sailboards.

 

Paul

 

Edit- here's a site of D2 board adverts. At the bottom is a D2 board called the King. Double ended! Anyway, boards that were for lightish air.

 

http://pavdivision2.blogspot.com/p/les-publicites.html

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Lots of intresting talk about planing or not, and fat or thin transoms,

post-20243-050711500 1326721662_thumb.jpg

this is Dragonfly's wl profile, so I suppose it has a Pin transom? or is it a planning transom? In any event it does seem to plane, and there is a transition stage, its in about a force 2, the bow lifts so that about 8 " of the boat is out of the water and speed increases, so most of the time it seems to be planing, it is quite diffcult to get the bow back down to the water, I have to move the carrage quite far forward and it still does not get back down.. The section is quite square

post-20243-051206300 1326721983_thumb.jpg

this is what it looks like under the mast. she has plenty of rocker, 100mm and its greatest at the mid piont, slightly flatter aft but not much. Working on a new design , not sure where to go at the moment but I think a bit more pointy, but transom really diffcult, it took a long time to design this one! She went quick enough in Germany sepecially in the light to moderate days, I was too wobbly to see how she went when it was windy.

Alistair

 

 

For you non IC sailors: Alistair finished third at the last IC Worlds in this boat. He was consistently quick, upwind and down, in a wide range of conditions. This design is definitely worthy of study.

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As you probably know the National Physics Laboratory in the uk did test a full sized canoe, 'Wake'. As you, Phil, say it could be a costly process. However, I am with Jim and agree that it would give valuable information. It would help to separate good boats from good sailors. What we need is a tame Marine engineering Ph.D student looking for a project!

Canoes and sailboards will behave in a markedly different way, due to the way the lift from the sail is used. The sailboard will have it's sail canted to windward so producing a vertically upward force as well as a horizontal force, which will reduce the wetted area. Canoes cannot be sailed in this attitude and often heel to leeward, so the sails don't help to lift the boat in the same way. I don't think that a straight sail area weight comparison is really appropriate( post #2159). For the sailboard, much of the weight will be supported by the aerodynamic lift of the sail rather than the hydrodynamic lift of the hull. I have never sailed a board so don't know how much weight can be supported by the sail, but I think it could be quite a large proportion of the 90 kg, so could alter the ratios quoted quite markedly. With the sail canted at 30 degrees the vertical force could approach 70% of the horizontal driving force but this depends on the exact flow across the sail.

I would guess that in the pic of chris' canoe ( post #2165) the reduction in wetted area is still less than 20%, and probably still has a wetted surface of 21-24 sq ft, whereas a sailboard will probably halve this (just a guess).

The resistance curves (post #2169) look pretty much as I would expect, 2 degrees stern down trim will effectively eliminate the rocker (this, of course depends on the amount of rocker designed into the canoe) so should provide a good planing area with little or no curvature and get rid of most of the suction.

(post #2174) remember that the bow can be raised either by an upward force forward of the C of G or a downward force behind the C of G. With such a small amount of the boat out of the water, the reduction of the wetted area will be almost negligible, and if the trim is being altered by a suction at the stern, the wetted area could be increasing. With such a large amount of rocker I would expect both, and most probably more suction at the stern than lift at the bow. You will probably only be changing the trim by about half a degree to achieve effect that you are reporting if your design is for the bow to be touching the water and not submerged when the boat is in it's designed trim.

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Glue drying, staring at Alistair's design. Much better than staring at glue drying.

 

Hmmmmmmmm.....

 

So(!)I doodled a rough sketch of the rule in planform. I superimposed what I am calling the Maas 7% rule. I got the stations upside down, sorry. The bow is where the dotted lines (Maas rule) come together.

 

To my eye it seems to be a nice way of understanding design direction? Anyone else done this?

 

Parallel rails at max rule beam are mighty short. Pintails give the longest rails, but small diamond tails get close, and with more lift than a pintail, less skin friction than a more beamy stern would give you, but less lift at semi planing speeds? Which seems to be where Alistair was going with this? Where Steve was going with the le Dartre?

 

Tricky stuff.

 

Time to take clamps off. Yippee! Destruction testing! The power of limits.

 

Paulpost-906-079042600 1326747025_thumb.jpg

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As you probably know the National Physics Laboratory in the uk did test a full sized canoe, 'Wake'. As you, Phil, say it could be a costly process. However, I am with Jim and agree that it would give valuable information. It would help to separate good boats from good sailors. What we need is a tame Marine engineering Ph.D student looking for a project!

Canoes and sailboards will behave in a markedly different way, due to the way the lift from the sail is used. The sailboard will have it's sail canted to windward so producing a vertically upward force as well as a horizontal force, which will reduce the wetted area. Canoes cannot be sailed in this attitude and often heel to leeward, so the sails don't help to lift the boat in the same way. I don't think that a straight sail area weight comparison is really appropriate( post #2159). For the sailboard, much of the weight will be supported by the aerodynamic lift of the sail rather than the hydrodynamic lift of the hull. I have never sailed a board so don't know how much weight can be supported by the sail, but I think it could be quite a large proportion of the 90 kg, so could alter the ratios quoted quite markedly. With the sail canted at 30 degrees the vertical force could approach 70% of the horizontal driving force but this depends on the exact flow across the sail.

I would guess that in the pic of chris' canoe ( post #2165) the reduction in wetted area is still less than 20%, and probably still has a wetted surface of 21-24 sq ft, whereas a sailboard will probably halve this (just a guess).

The resistance curves (post #2169) look pretty much as I would expect, 2 degrees stern down trim will effectively eliminate the rocker (this, of course depends on the amount of rocker designed into the canoe) so should provide a good planing area with little or no curvature and get rid of most of the suction.

(post #2174) remember that the bow can be raised either by an upward force forward of the C of G or a downward force behind the C of G. With such a small amount of the boat out of the water, the reduction of the wetted area will be almost negligible, and if the trim is being altered by a suction at the stern, the wetted area could be increasing. With such a large amount of rocker I would expect both, and most probably more suction at the stern than lift at the bow. You will probably only be changing the trim by about half a degree to achieve effect that you are reporting if your design is for the bow to be touching the water and not submerged when the boat is in it's designed trim.

 

 

ARE, I did a quick and dirty experiment to see how much weight was taken off my feet when holding onto a windsurfing rig. I put a scale on the floor under my lat pulldown bar, and weighted the stack to balance my weight so I was holding on to the bar like I would be if I would be holding on to the wish boom, but my feet were on the scale. I looked at my weight on the scale when I was at what would have been around a 10, 25, and 45 degree incline of the rig towards the wind. To my surprise, the most weight I ever took off the scale was 20-25 pounds, and that was at 25 degrees and more. I weighed around 200 pounds at the time. And if you look at top flit windsurfers, you will notice that they are sailing much more upright, unless overpowered. It seems rake is more important. I didn't have a harness to try. It may be that holding on to a cable supported bar swung my weight towards my feet more than a mast supported boom, but didn't feel that different from windsurfing without a harness. I tried the experiment with the scale parallel to the ground and angled towards me. No difference. You do swing around your shoulders to some extent. A harness's weight pulls more straight down.

 

 

Paul

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Not to stray too far off topic but is there anyone present who has sailed something like this? It looks like great fun and a modern one should turn some heads. Do the nearest and farthest boats have retractable poles on deck?

 

Thanks in advance for any assistance.

 

Take care,

 

Brent

 

2PlankIC2.jpg

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Bill Beaver put 3 full size ICs in the big tank at the Naval Academy as part of his design process for "Bolt."

The results of those tests and the following 1/4 scale tows pretty much drove me down the current path. The results of the first tests were published in the Winter 2010 Canoesletter.

The problem with those tests was that we were unable to pull the boats from their center of effort, so they behaved pretty badly at high speed, trimming nose up by stupid amounts (5-6 degrees) thus rendering much of the higher speed data fairly meaningless.

For reference this is 3.7 degrees of trim.

post-738-052581100 1326755188_thumb.jpg

SHC

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Not to stray too far off topic but is there anyone present who has sailed something like this? It looks like great fun and a modern one should turn some heads. Do the nearest and farthest boats have retractable poles on deck?

 

Thanks in advance for any assistance.

 

Take care,

 

Brent

 

2PlankIC2.jpg

The immortal Payne Mortlock canoes!

I have never sailed one or even seen one in the flesh.

Over the years I have doodled a two person canoe (something in the 26-28' length range) that has been known as the "Two Cedar."

It would have something like an I 14 rig in it and murder almost everything that floats on one hull.

Never got around to it though.

SHC

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On my frequent 3-4 hr drives to and from sailing, I've often wondered how much fun it would be to sail a doublehanded canoe. With a monsterous asym, of course. Steve, if you build it, they will come.

 

 

The immortal Payne Mortlock canoes!

I have never sailed one or even seen one in the flesh.

Over the years I have doodled a two person canoe (something in the 26-28' length range) that has been known as the "Two Cedar."

It would have something like an I 14 rig in it and murder almost everything that floats on one hull.

Never got around to it though.

SHC

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Apologies if this has been asked before, but can anyone say what the waterline beam (as opposed to the chine beam) is for a DC? Are they actually narrow or do they just appear so because of their length?

 

P.S. I'm sure you know already but it was never stated explicitly, planing only occurs if there is a stagnation point and spray being thrown forward (relative to the ground). Talk of planing being defined by Froude number is physically wrong, although clearly the bow needs to out of the water for the stagnation point to occur.

 

Great thread by the way.

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If I understood your first paragraph, I might, or might not, agree. :blink:

 

762mm on deck. So, what, about 600 on the waterline? And a Laser is about 850mm I guess. Just interested in getting a feel for the canoe.

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