stinky

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Hi Paul

No idea if it measures or not, but very intresting, the steering sounds like the same concept as simon had on "bootiful", a speed sailing craft of a few years back, never quite got going as it should have done but it did work, there were winches that worked on peadle power that moved the rig up and down the hulls, with just a fixed skeg at the back. Simon taught me to sail a long time ago and I helped him on this project and a few other bits and peices.

post-20243-0-38276400-1352814527_thumb.jpg

 

Bootiful is always on my mind. I have enough track to do a similar support /steering setup (with spars) but the stumbling block for me is raking the rig on the fly, given the balance challenge the seat provides. Maybe I'm too preoccupied with that. With the sliding LB, the foil can either be a centerboard or a skeg, depending on placement.

 

Did you sail on Bootiful?

 

Paul

Hi Paul

No, never had a chance, help launch her a few times, it all worked but was a bit fragile, took a lot of getting in the water and the conditions were not right for too much of the time (tide/ wind direction/ wind strength) and so the funding faded away. However nice place to sit and wait for that window (Brancaster Beach)!

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I'm reading the rules ... every other lines, and I don't see a ban on trapeze. Did I miss something?

Could one use a trap wire as an assistance for hiking? Hell, could one trap out of the end of the plank?

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Anders tried that; I think he donated the boat to charity though.

 

What? Trapping + plank?

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I'm reading the rules ... every other lines, and I don't see a ban on trapeze.

RRS bans trapezes - unless specifically permitted - so there's no need for class rules to do so.

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I guess there's nothing about trapezes, nothing that I could see with my quick read through, other than the width of the plank rule. I guess you could have a fixed sideways plank and trapeze off the 500mm wide tip but I'd think that's harder than just using the plank as designed.

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I'm reading the rules ... every other lines, and I don't see a ban on trapeze.

RRS bans trapezes - unless specifically permitted - so there's no need for class rules to do so.

 

Arf, I see. Thanks.

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Hi Jim, we just posted at the same time.

 

Are we bound by the RRS, as we fall under the umbrella if the ICA not ISAF?

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I'm reading the rules ... every other lines, and I don't see a ban on trapeze.

RRS bans trapezes - unless specifically permitted - so there's no need for class rules to do so.

 

What rule would that be? Can't find it on the rrs ...

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Probably best to not ask the question about RRS, but the short answer is there is nothing in the class requiring anyone to use it. The ICA does its own thing when push comes to shove.

 

Steve made some racks that ran in the carriage rails on Anders' boat. I have no idea how much Anders sailed it. But the seat is one of the best things about the ride on an IC I think.

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Probably best to not ask the question about RRS, but the short answer is there is nothing in the class requiring anyone to use it. The ICA does its own thing when push comes to shove.

 

Steve made some racks that ran in the carriage rails on Anders' boat. I have no idea how much Anders sailed it. But the seat is one of the best things about the ride on an IC I think.

 

Forget about racks. When I was still sailing canoes, I always thought it'd be nice to be hiking out of the end of the plank, and still have a trapeze to facilitate hiking. I'm just wondering how legal that would be. It's not in the DC rules and it doesn't appear to be in the rrs, unless I missed something, which is very possible.

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Well, if you like racks, max length seat permanently set perpendicular (not sliding) to longitudinal and max fatness, rolling fore and aft on tracks on the chine would get close. Hike bitches! (to coin a phrase....) some nice Da Kine footstraps, some sort of control over the rig rake....

 

Paul

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What rule would that be? Can't find it on the rrs ...

49.1

 

Canoe rule 1 covers the use of RRS for International competition, and the vast majority of other events will be run by organisations that come under ISAF anyway.

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Ah, yes. The sneaky placement of the RRS reference in the bit that no one reads (well, me anyway), just found it. ^_^

 

Thanks Jim

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I'm reading the rules ... every other lines, and I don't see a ban on trapeze.

RRS bans trapezes - unless specifically permitted - so there's no need for class rules to do so.

 

In fact RRS bans traps & sliding seats equally by not referring to them specifically,

but under the heading of 'Hiking Devices' . Trap classes amend 49.1,

 

so from the preliminary signal of a race run under (unamended) RRS,

seats are as illegal as traps

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I am sure I posted a reply earlier but does not seem to be here, must be going mad, but I think traps are banned under rule 13 part e, crew and equipment because the trap provides additional support, only the seat is allowed to support the sailor beyond the sheer line.

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so from the preliminary signal of a race run under (unamended) RRS,

seats are as illegal as traps

Because 49.1 is one of the RRS rules that may be changed by Class Rules, no change is needed in SIs and no amendment is required to RRS if the class rules permit planks or wires.

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Gui has a bad back and is trying to figure out how to sail and IC without having to sleep on a block of ice every night.

I would be lenient and allow an "adaptive" seating arrangement as long as it did not enhance his performance.

But that's just me being agreeable and trying to get another great guy back into the class.

SHC

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so from the preliminary signal of a race run under (unamended) RRS,

seats are as illegal as traps

Because 49.1 is one of the RRS rules that may be changed by Class Rules, no change is needed in SIs and no amendment is required to RRS if the class rules permit planks or wires.

but the class rules don't specifically ban traps

 

you can't have it both ways.

 

You are right only IF the class rules change 49.1, which they do not.

 

I'll show ya - http://www.rfev.es/a...es-2011-470.pdf

 

 

Section C – Conditions for Racing

C.1 GENERAL

C.1.1 RULES

(a) The following RRS 2009-2012 rules shall apply as amended below:

(1) If the average wind speed is above 8 knots, measured at deck level,

the race committee may permit pumping, rocking and ooching after the

starting signal. (change of RRS 42.2(a), RRS 42.2( B), RRS 42.2©)._ The

signals will be made according to RRS P5._

 

(2) A trapeze system may be used (change of RRS 49.1).

 

as i said traps & planks are banned equally under 49.1

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What rule would that be? Can't find it on the rrs ...

49.1

 

Canoe rule 1 covers the use of RRS for International competition, and the vast majority of other events will be run by organisations that come under ISAF anyway.

 

Thanks.

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I am sure I posted a reply earlier but does not seem to be here, must be going mad, but I think traps are banned under rule 13 part e, crew and equipment because the trap provides additional support, only the seat is allowed to support the sailor beyond the sheer line.

 

The problem is the rules don't state "this changes/alters RRS 49.1", this leaves us open for a potential shit fight in a mixed fleet situation, class racing and in particular International Competition isnt a problem... its a loop hole we may need to think about...

 

I guess the hassle is if ISAF change the rules then we are stuck having to alter our class rules for no good reason, however at the moment those who do sail in mixed fleets are open for protest :( as to which way a jury may sway is the question.... I sort of think its a loop hole fixed fairly easily via an amendment... and re amended in the future if required.

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Willy,

 

Out of curiosity, what year was the New York Cup created? I had heard the Quincy Challenge Cup that the 210 class contends for was the second oldest trophy in sailing to the America's Cup so it was interesting to see your comment about the New York Cup. I'll have to check on the Quincy Challenge Cup year.

 

Geoff

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At least 3 new ones in the UK - I've just finished one, started the next, and the third , will err... have to wait a bit . :)

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Willy,

 

Out of curiosity, what year was the New York Cup created? I had heard the Quincy Challenge Cup that the 210 class contends for was the second oldest trophy in sailing to the America's Cup so it was interesting to see your comment about the New York Cup. I'll have to check on the Quincy Challenge Cup year.

 

Geoff

 

The New York Cup dates back to 1884 which makes it the third oldest sailing trophy in the World but oldest dinghy trophy, there is an older trophy then the Americas cup called the "Ladies Cup" 1821 raced for in Sligo Ireland. The Americas cup 1851 is the longest held sporting trophy in the world and also one of the older sporting trophies. I googled the Quincy Challenge Cup 1898 it was established make it the fourth oldest sailing trophy regardless sounds like it has some great history and would be pretty cool to get your name as part of its history...

 

ICU2

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Thanks ICU2...I'm cool with fourth oldest, that's an honor (I've won it once or twice). When I googled it I could only find it being sailed in 1906.

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The winter of 1899/1900 saw the presentation of a Challenge Cup for cruisers by Roger de Quincey, who was Bertram’s father. This Cup immediately became known as the Quincey Cup. the Challenge Cup was presented in 1875, the original intent was for a cross channel (English) race, but in the event was for a race within the solent. More info on the history can be got from the history which I wrote some time ago. If you want more info on the history of the class in Britain then I can let you have a PDF copy of the history.

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Rule 11e sets the limit a sail can be raised measured from the bottom of the hull.

 

Is this point the bottom of the hull under the mast step, the lowest point of the hull when floating level on her lines, or the bottom of the hull at the designated measurement point?

 

BTW, Andrews history is good reading.

 

Paul

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In simple terms this is how we have measured at the worlds. The mast is to raked sothe tip is at the highest possible position, then measure from directly under the hull along the line of the mast... I have a picture somewhere which explains this clearly I'll try and find it and post it...

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I think that pretty much answers my question, but I will really appreciate the pics.

 

Thanks!

 

Paul

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Definitely not! It's ugly :lol: . Seriously, I think it might depend on where the measurement station is as it would have to satisfy 2 metre longitudinal tape test, so it would need to be more than a metre forward of the measurement station ( if I recall the rule wording correctly).

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would a strut be legal?

For what little my opinion is worth I think that 5g (The hull surface shall be a continuous structure fore and aft and athwartships. It shall not be breached by any through structure or holes) would prohibit the strut, since its effectively a large hole/discontinuous structure.

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would a strut be legal?

For what little my opinion is worth I think that 5g (The hull surface shall be a continuous structure fore and aft and athwartships. It shall not be breached by any through structure or holes) would prohibit the strut, since its effectively a large hole/discontinuous structure.

Yes I think you are right, I was thinking about holes from above being out but it does not say that, just any through holes are not allowed

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post-20243-0-80523800-1355835921_thumb.pngpost-20243-0-25003100-1355835936_thumb.png

would a strut be legal? ( I have only modeled one side)

 

The strut really isn't needed. A carbon chainplate that is bonded into the hull could safely transfer the shroud load to enough of the hull surface to do the job. The strut adds unecessary drag.

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would a strut be legal?

For what little my opinion is worth I think that 5g (The hull surface shall be a continuous structure fore and aft and athwartships. It shall not be breached by any through structure or holes) would prohibit the strut, since its effectively a large hole/discontinuous structure.

Yes I think you are right, I was thinking about holes from above being out but it does not say that, just any through holes are not allowed

 

A strut bridge is not a continuous structure? A Pratt truss (for example) is not a continous structure?

 

This is about aesthetics.

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This is about aesthetics.

For sure. There are quite a few things in the Canoe rules which are about aesthetics/controlling form. And why not.

 

If the rules were completely free I would have big hollows in some parts of the topsides to manage the transition between a straight sided dance floor from near stern to shrouds and much more curved hull underneath in order to have a sharper chine/transom release aft and a wider shroud base forward, but according to my reading that's not permissable, so one has to go back and think more cerefully about solutions. To my mind supporting a wide shroud base/dealing with the consequences of a narrow one is one of the more significant challenges in the rule set to keep a designer entertained.

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So what rules apply to the deck? Seems to me you can do hollows in the deck- as long as the 4" rule(s) is/are met.

 

Would an external sheer clamp count as the one concave per side at the measurement point?

__

_____|_|

|

|

 

Was the first String Theory illegal?

 

Were the steps on the deck sheer line on 1stCL legal?

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I don't think any rules apply specifically to the deck. The beam profile of the entire canoe looking down from above has to meet the concave and convex requirements for number and radius. The shear clamp would likely be the beam.

 

Seems like you are applying the rule to parts other than the beam.

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That is what I'd like my reading to be- the 'I don't think any rules apply specifically to the deck' part....

 

But let's say (let's say ;)) I used a tripod for an unstayed mast, and the tripod rested or was attached only to/on the deck, didn't extend past the shear line etc.. Then what?

 

And would the lengthwise corners of the struts (if legal) be exposed to the convex radius rule?

 

If the resulting strut triangles were covered by plywood to meet the the no through holes rule, would the joints where each sheet of plywood met be exposed to the convex radius rule, or would a 'folded crease' be acceptable?

 

 

 

 

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If it all stays inside the beam you are good. I don't think you need plywood covers to be legal. The struts are part of the rigging, not the hull.

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My boat to the early draft rules (Tin Teardrop ) had the shrouds out on platforms, with hollows and holes in the plan view each side of the shrouds.

post-2679-0-84862500-1356038983_thumb.jpg

This 'wasn't quite what we had in mind... ' so the draft rule was firmed up for the latest / current version of the rules, only allowing the one hollow and no holes. I altered the boat at the same time, so no problem - in fact it was much better with more width on deck with a flare/wing behind the shrouds. Both however had tripod mast support, and no-one seemed to mind about that - the intention was to stop the rule-beating hollow bridging and holes.

post-2679-0-07023100-1356039166_thumb.jpg

post-2679-0-75669000-1356039186_thumb.jpg

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My understanding then is that only the flares (or concave, I guess) under the wings are considered part of the one allowed hull concave at the beam measurement spot. The concave dish of the dance floor is considered part of the deck, and doesn't count as a second concave.

 

The 4" rule(s) does not pertain to the seat carriage because it is a deck object?

 

Were you tempted to fair the tripod? (A Bieker Rocket Science moment :)/>)

 

Also, diggin' your fence in juxtaposition with the row cottages behind it in the bottom pic.

 

Ah, life near the beach....

 

Thanks Andy.

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My understanding then is that only the flares (or concave, I guess) under the wings are considered part of the one allowed hull concave at the beam measurement spot. The concave dish of the dance floor is considered part of the deck, and doesn't count as a second concave.

 

The 4" rule(s) does not pertain to the seat carriage because it is a deck object?

 

Were you tempted to fair the tripod? (A Bieker Rocket Science moment :)/>)

 

Also, diggin' your fence in juxtaposition with the row cottages behind it in the bottom pic.

 

Ah, life near the beach....

 

Thanks Andy.

 

No... the hollow/concave only refers to the plan view - the 2nd boat has max hollow in front of the shrouds, ( with the required radii ), and is curvy convex all the way the the 'transom'. The measurement at BMS with the tape etc, allows flares/wings above the 500mm from centreline measured round the outer skin. ( and not narrower than 750mm total beam for 275mm from the bottom of the hull )

It's all in the rules <_<

 

Hull and seat are separate objects, with their own measurement rules.

Less aero/wave drag for struts, but a strong stump would do the same.

 

Near the beach = just minutes from deciding to gosailing to being on the water - 8mins for a Pico :) - more like 30mins for the moth :unsure:

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So Andy has me reading the rules (again :)/>) and the part about measuring a concave (4c) has me stumped. I had read it as using the 1000 mm straight edge across the concave, but the rule says longitudinally ( fore and aft is the wording- I think that means longitudinally). Like parallel to the keel? How does that measure the depth of a concave? For example if the the concave is straight longitudinally, like half a straight pipe, it could be infinitely deep and still measure as zero Or is an angle to longitudinal involved?

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You are getting me confused now...

 

Look down from above, use a straight edge 1000mm long bridging any hollow, and considering the projection/shadow/view from above, the outline can't be more than 100mm from the straightedge.

post-2679-0-91383700-1356298194_thumb.jpg

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Rule 5:

 

a: length and stuff

 

b: smooth curve from above rule, 45 degree pointy ends, and THEN "the line of greatest beam may be combination of convex, concave or straight lines", then a definition of the radii that define tightness of radii- 60mm & 100mm, number of concaves per side (1 in line of greatest beam (?)). Which I think is a body projection/view...

 

Then we get to the crux, I think,

 

c:" a 1000mm straight edge set to span such a concavity (such a concavity has to be the 1 concavity allowed in the line of greatest beam, ie the greatest beam in body view? Or is it in plan view?) FORE AND AFT (wtf?) with 0mm at the outboard tangent shall be no more than 100mm from the hull skin measured perpendicular to the straight edge". (and if the straight edge is a ruler, which direction is perpendicular? The plane of the ruler? The edge of the ruler?)

 

I guess for me the crux is the definition of "such a concavity". For me it's like a pronoun, which refers to the last noun or proper noun.

The last reference would seenm to be to the number of concaves allowed in the line of greatest beam.. Because if it isn't, only one concavity is allowed in plan view, which would be inconvenient.....

 

Good Yule, y'all.

 

Paul

 

 

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To be more clear, I'm posting about a concave, like a body projection of a 505 (I'll describe a body projection or view as a view of the hull seen from the front or back, and can be a slice of the hull (in 2 dimensions) athwartships at the measurement point). The sides (as they flare out) of a 505 create a concave shape in body view, which is also a longitudinal hollow running down the side of the hull.

 

Another way of visualizing this would be like the tunnels (longitudinal hull concaves) of some long race boards, however subtle or pronounced. Canoe specific, if you look at Andy's canoe flares from the front or back, rather than the top, they form a concave (or hollow) that runs down the side of the hull.

 

Are these measured in any way?

 

Or is the body plan not measured aside from minimum and maximum width?

 

Is the line of greatest beam being a combination of straight, curved, convex and concave lines a rule for the body (or front) view and the plan (or top) view, or only the plan view. Or profile view, for that matter...

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To be more clear, I'm posting about a concave, like a body projection of a 505 (I'll describe a body projection or view as a view of the hull seen from the front or back, and can be a slice of the hull (in 2 dimensions) athwartships at the measurement point). The sides (as they flare out) of a 505 create a concave shape in body view, which is also a longitudinal hollow running down the side of the hull.

 

Another way of visualizing this would be like the tunnels (longitudinal hull concaves) of some long race boards, however subtle or pronounced. Canoe specific, if you look at Andy's canoe flares from the front or back, rather than the top, they form a concave (or hollow) that runs down the side of the hull.

 

Are these measured in any way?

 

Or is the body plan not measured aside from minimum and maximum width?

 

Is the line of greatest beam being a combination of straight, curved, convex and concave lines a rule for the body (or front) view and the plan (or top) view, or only the plan view. Or profile view, for that matter...

 

The plan view / overhead projection rule limits the shape of the outermost 'shadow' of the max width of the hull - curves and starights etc, one hollow per side, max 100mm deep over 1000mm as my pic earler.

 

The 'tight tape' rule prohibits any hollows over the outer skin of the hull within 1000mm for and aft of BMS, and 500mm either side of BMS. ( ie looking from in front/behind projection)

So... you draw a line on the hull at BMS from gunwale to gunwale, mark 500mm from the centreline. With a piece of string 2m long, the middle of the string on the BMS line, move the string parallel to the fore/aft axis - holding each end if you've got long enough arms ;-) and within the 500mm measured around the hull skin at BMS - no hollows in the length of the string.

 

and/or... a 1000mm piece of string, middle on the centreline, stretched over the skin can't have gaps under it. Start at 1000mm in front of BMS, move the string back to 1000mm behind BMS - no gaps between these positions.

On my boat, the flares start at more than ~550mm from the centreline at BMS ( measured around the skin ) so that's OK. The string ( up to 1000mm in front of and behind BMS ) never gets onto the flares with the string parallel to the centreline at the furthest out position ( nor at 500mm from c/l around the skin )

 

So tunnels, flares, concaves, shapes like 5o5 are all OK, providing these hollows are outside the rectangle 2000mm x 1000mm wrapped around the skin.

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Thanks Andy-

 

So the 1000mm lengthwise string is in effect a movable buttock line?

 

And the 1000mm side to side string only measures at the bms?

 

And can a concaves beyond the Box consist of acute angles, like the opposite of a hard chine?

 

Are the tunnels, flares concaves etc. outside of the 2000mm box constrained by the 100mm measurement rule?

 

I owe you a beer. Or a single malt.

 

Paul.

 

 

 

 

 

 

 

 

 

 

 

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Thanks Andy-

 

So the 1000mm lengthwise string is in effect a movable buttock line?

 

Um yes I think so ( being self-taught so not exactly sure of the terminology )

 

And the 1000mm side to side string only measures at the bms?

 

No! at BMS but also for 1000mm in front and behind BMS.

 

And can a concaves beyond the Box consist of acute angles, like the opposite of a hard chine?

 

Yes :)

 

Are the tunnels, flares concaves etc. outside of the 2000mm box constrained by the 100mm measurement rule?

 

Outside the 2000mm x 1000mm 'surface' box - no constraints :)

 

I owe you a beer. Or a single malt.

 

Cheers!! :) hic :unsure::P

Paul.

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This is excellent-

 

If you, or a surrogate you trust, will be at the San Fransisco 2014's, above payment (sic, hic) can be arranged. Otherwise let me know...

 

Off to mess with wood and glue. Amongst Moose and Squirrel.

 

Paul

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I'm starting some models in foam to get an idea what kind of hull shape I'd like to build. I have some questions about the relationship between a hard chine, the line of the keel and the static waterline.

 

1) If I'm going to go with a straight keel from the halfway point of the hull to the stern should the chine be parallel to the keel, the static waterline, both, neither?

 

2) Is it acceptable for the any part of the chine to be submerged when the hull is not moving or should it be positioned high enough to avoid this?

 

Would it be possible to build a skeleton strong enough to support all the key parts of the canoe, ie rudder, daggerboard well, seat carriage, mast, jib tack and have it still be light enough to use for testing hulls? The idea would be to build blue or pink foam shells and insert the skeleton. It would be a quick way to test a variety of hull shapes. The bare foam would like ly be strong enough for testing as most of the stresses would be carried by the skeleton. Modifying the hull would be a very quick and easy proposition. Thanks in advance for any thoughts.

 

Take care,

 

Brent

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You might check out Swaylocks XPS thread- it's a surfboard forum, but they cover a lot of construction approaches, as well as shapes, chines, outlines, water flow etc. There are also some good opinions on some of the longboard sites about immersed chines, foil, rails etc. Right now, some SUP shapers are using a subtle v to get the chines closer to the surface, and minimizing rocker for forced mode sub planing regimes with good results. There are some posts in this thread millions of pages ago on the subject.

 

XPS doesn't stick to much as far a glueing, out gasses like crazy, is farcking wonderful to shape. I'd at least paint it with an industrial sealant or paint- look at some of the building insulation sites for product. Even if you get up to some of the stuff made for use under heavy concrete, which is pretty dense, the bow is probably going to snap off without some sort of sheathing. Thin okume, like 2-3 mm ply will work with epoxy, just make sure you rough up the foam a lot before you glue. If you use a skeleton, probably better to enclose the foam with the structure, then you don't need to worry about glue so much. A central stringer is a good idea.

 

I want to believe in XPS, but I can't use epoxy (built too many longboards with it) which limits it's usefulness for me. But if you can use epoxy, it's way fun. Check out the Swaylocks site. Personally I'm exploring the exoskeleton thing for protos, but I think a leeboard works better with the concept.

 

If nothing else, shaping blue foam gives you a great feel for the hull. Edges tend to crumble in the water though, and quickly.

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There are no hard and fast rules about chines.

Almost everything has been tried.

I prefer to keep them fairly low and somewhat splitting the difference between the keel line and the waterline.

There is always a problem fairing the shape at the bow where the topsides and chine intersect the waterline.

Lots of pretty good solutions as well.

In reality, the deck of an IC is pretty much the space frame you describe.

There needs a hull under it to provide the rest of the torsion structure, but it turns out that this is fairly easy to accomplish.

So if you were intent on playing the shape game, you could be pretty improvisational under a relatively normal looking deck that moved from boat to boat.

I tend to think that it is better to move the experiments along to interested bystanders and start fresh. A boat that works has much more value than the pieces.

SHC

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Steve,

 

First if I haven't thanked you I want to for keeping such a cool boat on the radar so I could "discover" them about a year ago. My life would have been the less for it had I never sailed a canoe. Thanks also for your comments on this, your suggestion of complete boats definitely provides a better shortcut to building a local fleet.

 

I do like the idea of a reusable deck module as opposed to an internal skeleton. Anybody care to sketch something that would likely stand up to the loads the rig, seat, daggerboard and rudder impose? If done correctly hull blanks could be mostly flat topped, maybe stepped near the mast location with slots to accept any necessary vertical elements, i.e. trusses, foil wells etc. It would be great if I could just bolt the module onto some inserts in the hull blank. Any thoughts on what the deck module would best be constructed from?

 

My thinking was that if I could do relatively quick and dirty hull testing I'd be willing to try more ideas rather than becoming married to a less than stellar shape because I already had significant time and materials invested. I envision, though perhaps unrealistically, that you could quickly add or remove volume and modify the shape of the blank. Materials for a new blank should be under $300.

 

I took a wild guess that a canoe hull has about 25 cubic feet of volume, someone please correct me if that is way off. If so even a solid blank would weigh about 25kg if you used Foamular 600 or HiLoad 60. It could weigh as little as 18kg if you could work with Foamular 250 or Square Edge. If a deck module formed the the dance floor and the top deck the foam weight would be less and the lower compression strength foam might work. Stop me now if this seems like a really horrible idea. Otherwise thanks for any suggestions.

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I have glued bits of styrofoam onto the side of a canoe to see what the difference between a full 45 degree stern and a standard Nethercott stern was. My gut feeling is that the work involved in gluing on a new skin, filling and fairing the lot and producing a reasonable surface is such a high percentage of the total labour effort of building a whole new shell that to has to be questionable whether the gain would be worth the pain and the amount of throwaway.

 

I suspect dent resistance would be the killer for a sold foam boat, but I also wonder, without doing the sums, that achieving the same engineering properties and weight with single skin/solid core against hollow/double skin might be tricky.

 

I do recall someone trying the deck/skeleton/glue on styrofoam approach with a Moth many years ago but I don't recall whether it really came to anything. If my memory of who it was is correct then these days he's building boats with a conventional layup/construction type, but spending a lot of effort on digtal control of cutters to speed up the build process, so maybe it didn't work as well as you'd think it ought to.

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The two Magnum 10 moths built were from solid foam and glass/carbonskinned - heavy, denty, and break in halfy :wacko:

My latest IC shell, mostly ±45° carbon on 5mm foam, painted weighed 22.5kg, so 25kg just for the foam = heavy.

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protos here made solid did not behave like hollow boats, noticeable difference in molded products even when weight is similar, probably the ends. however screwing or taping chines or rails on for testing has worked.

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Brent:

If you are really hell bent on the idea, the thing to do is build a single chine shape on the underside of the deck that is smaller than any shape you are likely to try out.

If you envision using 2" pink foam, them make your inside shape 2" small.

This can be built out of 1/8" plywood and doesn't have to be stiff at all because the foam will do all of that for you.

This way you eliminate all the foam that isn't doing anything except holding the foam you want to shape in place.

It can do all the structural work of the daggerboard and rudder slots and resolve the torsion between the shrouds and seat carriage.

 

I did this with a bunch of models when I was a kid when I was a kid.

You will want to be fairly careful to make the foam as small as possible because of weight.

And no matter what you cover the foam with, it is going to get trashed pretty quickly.

SHC

 

SHC

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Thanks for all the replies. Hell bent? Could be. But while I don't lack ego nor feel the need to follow any crowd I do have enough sense to avail myself to the vast store of knowledge here in hopes of getting a feel for whether it's an idea worth pursuing.

 

Making a slightly smaller hull box is a great suggestion. I wouldn't need to be concerned with fairness. The first picture that popped into my head was a long skinny Optimist hull, not what you had in mind I'm sure.

 

I do want to make clear the intention was never to have a "keeper" made from foam. The foam hull would only be for testing. Once you arrived at a shape you liked you could use it as a male plug to do a proper boat from. My goal was to have a shape that could be quickly and cheaply modified and not have to put so much time and money into a theoretical design that might not pan out in practice.

 

Once done I could hotwire the foam off and try a light air only hull shape or pass the box hull onto the next guy with a crazy idea of what a 21st century canoe should be shaped like.

 

It seems to me to take biggest advantage of any development class you have to be able to try out multiple solutions. Spending months of my free time and thousands building a hull would have a tendency to slow the development process for me if not others. I can spend $2-3000 in materials to build a hull just not very many times in a row. I also think once I do it I'm going to be more attached to that hull than is wise from a development standpoint even if it doesn't work as I had hoped. Has that ever happened in the DC/IC world?

 

I really do appreciate all your input, thanks for sharing the knowledge. It bodes well for keeping the class alive.

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Not far off the long Opti hull, but I would do a few things like have an extension that went all the way out to the bow and stern and maybe some provision for putting spines where you wanted to maintain a shape (like the keel or chines.) I find it much faster and easier to shape foam when I have some reference points to keep me in the ball park. Of course the more you restrict your are of experimentation, the easier it gets to execute. If you, for example, decided that you were only going to mes around with the shape below the chine, everything above the chine could be built in the standard way.

SHC

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Might check on this site, as they can cut foam accurately.

 

I've shaped a lot of foam and while fun is time consuming. I'd suggest if you're using blue board, use the outside straight edges of each blank for a 3 or 4 mm stringer down the middle that extends up into the exo skeleton: you could try bolting them together?

 

Easier to go 16' on you proto, less glue lines to cut/sand through. 4 pound xps will bend enough for nice rocker. Use 60 grit when glueing to get a good bond. Xps out gasses when cutting or sanding- do it outside, bad shit. Wear a dust mask or better. Japanese pull saws work nicely for gross cuts/curves, sureforms (fine cut) for second, then 100 grit. 200 grit is amazing.

 

 

 

 

 

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Sorry about the quality from my phone camera. Here are some pictures of the crude 10th scale model I carved this afternoon. Obviously no effort to fair it yet. Hull planform results from a max beam of 30" from the "transom" to an intersection with straight lines from a 7% half entry (thank you Mr Maas). Max beam begins about 60% back from the stem. No rocker from midpoint aft.

 

It will weigh just under 20gr once the deck is raised to where it probably should be. This should translate to 20kg for a full size solid model from the same material. It floats on its lines at 150gr so full size displacement would be 150kg. Please correct me if I'm wrong about these factors.

 

It floats slightly bow up with 130gr weight placed as shown. In my previous model experience this was desirable for static balance as the high aspect rig generally pushed the bow down as soon as there was some breeze. Should I move the center of bouyancy aft or will this also be a good thing full scale? On a related topic how far back is too far back for the rig?

 

Once I get some feedback I'll carve a 5th scale version and see if it comes out at 160gr with 1.2kg displacement.

 

As SHC sensibly suggests it may end up being a below the chine only foam boat. I might keep my options slightly more open in the stern in case I couldn't resist testing a pintail. I do love a double ender.

 

Bow_zpscdacf960.jpg

 

Side_zpsb982db38.jpg

 

Waterline_zps7e8bb106.jpg

 

Deck_zps4fcf9070.jpg

 

Stern_zpsa0e90d3b.jpg

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Andy, you did lots of experimentation with Tin Teardrop. You reported on them elsewhere but the photos which went with the report are no longer showing ( on my browser, at least). Your impressions of manoeuvrability versus rocker would be interesting, as would your impressions of the change in boatspeed brought about by shortening the boat. I am unsure how rocker is defined and it seems that there may be several different ideas of what it is. I am thinking of it as the difference between the max draft (of the hull) and the average of the draft at the bow ( ignoring any rounding off of the hull in the first few inches) and the stern when floating as designed.

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Rocker = foil? The distribution of volume ( or flow) along the length of the hull?

 

 

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no, in surfing foil generally refers to volume distribution for boards and camber for fins, rocker is keel rise above a horizontal, can be a bit tricky but usually measured off the midpoint so nose rocker and tail rocker, not to mention flip, which is the extra rise in some boards noses.

http://www.surfscience.com/topics/surfboard-anatomy/foil/what-foil-means-to-you

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Wetted surface displacement curve?

 

Anyway, messing around with the 500 mm string, I started fooling around with wider hulls, and it made me wonder- is the end of the string the end of the outside skin of the hull?

 

For example, if I wanted to go max beam, and still obey rule 5d - "at bms, nowhere between the heights of 100mm and 275mm above the keel shall the SKIN of the outside hull be less that 750mm in beam.". Couple this with 5b saying that "the line of greatest beam may be a combination of convex concave and straight lines." So you could wind up with something like this in cross section at the bms?

__________________

|. |

____|. |____

|_________________________|

Kind of th_______________ e opposite of this:

|. |

____.___|. |______

|_______________________|

 

Since the 500mm tape wouldn't even stretch to the chine (at even a 41" beam hull) Would it be ok to put a 1" board up at bms across the deck and have it count as hull? Or would you need sides that connected with the deck, and how long longitudinally would they need to be?

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Or is this the intent of the rule with a 44" beam? At least with a 90 degree chine...

 

|. |

|. |

|___________________________|

 

I think I remember Steve (and I paraphrase here) saying something about 'God Damned surfboard shaped IC's'. :)

 

 

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The ' no hollows ' bit in sections applies to the 500mm tight tape, outside this there is also the 750mm min beam to 275mm high - you can do any shape you like within this part, and it only has to measure at BMS, so gunwale bumps in the side elevation are OK to meet the rule ( but of course normally there are seat tracks that need to be straight... )

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The 1" board at BMS needs to qualify as hull too, whatever the criteria for being hull is. Being made out of wood (as opposed to sponge or repurposed squeegee material) may be enough to be considered hull.

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I think I'm starting to catch on.

 

Thanks guys.

 

Now criteria for being a hull...

 

Zen koan time?

 

Shaping time!

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My tiller extension got broken on the weekend and top half was lost in the drink, so I can't measure it up for a new one. To save me working it out, does anyone know the length of tiller extension they use?

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I usually use 1.8m landing net handles, but they're too short if you really hike off the end of the plank, so 2m is probably what you want.

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I usually use 1.8m landing net handles, but they're too short if you really hike off the end of the plank, so 2m is probably what you want.

 

Thanks Jim. My old one was a Ronstan, so it was probably the 2030mm version.

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I'm using orange (fast) PVC tube for the new tiller extension. I think I might just make it 2.5m and cut it down later if it's too long!

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Crappie pole from ebay!, as long as you want,light, strong as heck, and cheap! Mine is 7'5", and I have an extra one in the boom if I crash and land on it!I

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Does anyone know what week Sugar Island is this year? I know its early, but I need to pick slots for kids sailing camps.

The Encampnemt is July 21 to Aug. 3. , racing is usually the first week. But best to querry John K. or Willy.

It's on the West Coast Schedule, anybody in ? it's only a 2900 miles drive and well worth the effort.

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