Designing to Steve Clark's proposed new rules

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Phil Stevenson
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Post by Phil Stevenson » Wed Sep 20, 2006 10:24 pm

Colin,
That one snuck up on me. Missed it up till now. Could be interpretted a few ways though. Sort of depends on whether it is the rig or the hull which is "floating freely" and whether it is intended that the hull is upright at the time.

I suspect it would be possible for me to remove the sail from the capsized boat but to do so I would need to undo so many lines there would be serious danger of loosing the sail from sinking and the mast from floating away. It would probably be impossible to strip the sail this way at all if the rig had stays.

At present it would be easier to remove the mast from the hull than the "sail from the mast, but as a new luff pocket is coming soon a long Zip may be needed to satisfy at least some of the possible rule interpretations.

Regardless, is it needed?

After all there are 190,000 lasers and 1,000 moths out there who manage quite well without it. And unlike a laser rig, a carbon mast with the ends plugged floats very well. With haliard access to the inside it would sink.

I have been sailing moths for 8 years and in that tiime I have never tried to remove the pocket luff sail from the mast while in the water. I have on two occasions dropped the rig and been towed home with the sail/mast held horizontal above our heads, a very stable position. It would be a lot easier on the hugely more stable canoe hull.

So while the 5.3m long luff pocket Zip might be deemed as necessary I think it will only add cost and complication and will never in fact be used.

Phil S
Design perfection is achieved, not when there is nothing else to add but when there is nothing else which can be taken away.
http://philscanoes.blogspot.com/

Ben Fuller
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Post by Ben Fuller » Thu Sep 21, 2006 1:58 am

As Colin knows there have been more than one occasion when mains had to come down to rescue a canoe or sailor. I recall two situations in Rhode Island. If the class wants to do away with the rule it will need a vote. Perhaps a new thread would draw attention to the problem. The intention was to get the sail down when the boat is capsized without needing tools ( like a knife ). I recall that some of the sleeve sailed Swedish boats had a topmast sock and a zipper from hounds down.
Ben Fuller
Macavity
USA 172

Karl Wittnebel
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Post by Karl Wittnebel » Thu Sep 21, 2006 6:07 am

Others may disagree but particularly when learning to sail the IC in breeze it is handy to be able to take the main down. In event of tiller extension failure, for example, it becomes impossible to sail the boat with the main up in breeze, but it is perfectly possible to limp back under jib alone, even upwind. Of course on the DC there may be no jib, so things are a bit more binary.

If it comes down to being towed it is usually breezy and very hard to do with the main up also.

The Moth is a simpler boat and I would say there is less stuff to break. When the seat carriage comes unglued from the deck, for instance, a mainsail becomes rather superfluous. Or when the seat or carriage breaks. Such scenarios are more likely with incentives to lower weight - so far I count one seat and one carriage failure on new light parts here in the US.

Anyway I don't know if the requirement is absolutely necessary and I like pocket luff rigs, but my experience has been that it makes sense to be able to tuck the main away in the event of an unforseen adventure. It is interesting that Moths seem to get by without it.

Karl
Karl Wittnebel
NC USA 193 (Lust Puppet)

Mal Smith
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Post by Mal Smith » Thu Sep 21, 2006 6:49 am

<blockquote id="quote"><font size="2" face="Verdana, Arial, Helvetica" id="quote">quote:<hr height="1" noshade id="quote"><i>Originally posted by Ben Fuller</i>
<br />The intention was to get the sail down when the boat is capsized without needing tools ( like a knife ). I recall that some of the sleeve sailed Swedish boats had a topmast sock and a zipper from hounds down.
<hr height="1" noshade id="quote"></blockquote id="quote"></font id="quote">

So if a freestanding mast can be unplugged from the capsized boat without tools, and then the sail in turn can be removed from the mast without tools, does that count?

Mal.
AUS019

Paul Scott
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Post by Paul Scott » Thu Oct 19, 2006 1:27 am

DC Rules Appendix IV, #5, sub c:

"Beam shall be measured at a... BMS located between 1300mm and 2600mm forward of the stern. At BMS, nowhere between the heights of 100mm and 300mm above the keel shall the outside of the hull skin be less than 750mm in beam"

Is the BMS 1300mm in length? Or is it a point? It is implied that the BMS is a single thing by the phrase "at a BMS".

If this shows an ignorance of dinghy measurement rules, forgive me. (And there is an I14 with a measurement bump down at our local dinghy dock. It's a really sleek bump...)

Paul:?:
"Exuberance is better than good taste" -Flaubert

Mal Smith
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Post by Mal Smith » Thu Oct 19, 2006 1:42 am

Strictly speaking, the BMS is a transverse plane. My interpretation is that the BMS can be located anywhere from 1300mm to 2600mm from the stern. Quite possibly, for any one boat there will be a range of locations for the BMS where the minimum beam rules and the fore and aft curvature rule (measured from the BMS location)will be satisfied. It is not clear whether the owner can nominate the location of the BMS or whether it is up to the meassurer to find one by trial and error. I presume it would be ok for the owner to suggest a location to the measurer, which the measurer can then verify.

Mal.
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Paul Scott
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Post by Paul Scott » Thu Oct 19, 2006 3:19 am

Mal-

Or STEVE,

That's what I'm hoping.

Does Appendix IV/5/c (...at BMS, nowhere between the heights bwtween 100mm and 300mm above the keel shall the outside of the hull be less than 750mm in beam.) imply that the hull has to have a minimum freeboard of 300mm? Is there a minimum freeboard?

Paul :?:
"Exuberance is better than good taste" -Flaubert

Mal Smith
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Post by Mal Smith » Thu Oct 19, 2006 9:39 am

The rule states that there is a minimum hull depth at the BMS only, of 300mm (freeboard is measured from waterline, not the keel). The implication is that freeboard can be reduced forward or aft of the BMS.

Mal.
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jimc
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Post by jimc » Thu Oct 19, 2006 9:45 am

<blockquote id="quote"><font size="2" face="Verdana, Arial, Helvetica" id="quote">quote:<hr height="1" noshade id="quote"><i>Originally posted by Mal Smith</i>
<br />...the BMS can be located anywhere from 1300mm to 2600mm from the stern. Quite possibly, for any one boat there will be a range of locations for the BMS where the minimum beam rules and the fore and aft curvature rule (measured from the BMS location)will be satisfied. <hr height="1" noshade id="quote"></blockquote id="quote"></font id="quote">

Yep, there was a lot of discussion about this in the early days. The idea was to avoid problems experienced in various classes where the measurement point is specified and which result in a distorted hull shape purely to meet the rule. You can see it in 14s where the boat mets the beam requirement further aft but is bumped at the mid length measurement point. An example of distortion without bumps is on some recent Australian Cherubs where the chine line is virtually a straight line from bow to mid length measurement point, takes a pretty sharp radius and then is a straight line from there to the narrower transom.

So this rule is phrased so that the measurement point and thus the width in the hull can effectively float up and down the boat according to the wishes of the designer. In practice its likely to be pretty obvious where the measurement point should be taken. Should it ever become a problem I guess one could specify a coloured spot on the gunwhale or something.

Steve Clark
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Post by Steve Clark » Thu Oct 19, 2006 2:23 pm

The Canoe must satisfy the requirements of 5(c) at a single transverse section ( staition) located somewhere between 1300mm and 2600mm forward of the stern.
One thing that is not perfectly clear is that I did not intend that the canoe maintain a 300mm depth of hull for one meter on either side of the BMS. It is possible for sherer height to be reduced on either sider of the BMS.
For example, The sheer height of a Nethercott drops as it goes aft, if the two meter tape were applied strictly parallel to the waterline, it would run off into space aft of the BMS. This might lead to all sorts of confusion. What is intended is that the tape is run over the topsides as they exist to assure that the hull form is fair around the BMS and has not been deliberately distorted circumvent (cheat) the rule.
However, I will predict that if we see a sailboard with a pipe sticking out of it on each side and someone contending that this satisfies rule 5(c) we will be quite angry and that additional language would be created to prevent such foolishness.
I have a BIG supply of shark repellant.
SHC
Beatings will continue until morale improves

Paul Scott
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Post by Paul Scott » Thu Oct 19, 2006 4:55 pm

Steve-

"Prudence is but experience, which equal time equally bestows on all men, in those things they apply themselves equally unto."

Thomas Hobbes, LEVIATHAN, (1651), 1.13

It would be a beautifully sculpted piece of spruce and carbon, anyway. Pipe indeed......

Harrrrumph

Paul :twisted:
"Exuberance is better than good taste" -Flaubert

Andy P
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Post by Andy P » Thu Oct 19, 2006 5:15 pm

I measured my Nethercott K 176, and it is marginal at measuring to this rule. It measures at the mid length point ( 2600mm from the stern ), and is too shallow further aft. But only if the track supports are included as 'hull' for the purpose of 'outside of hull skin'.

Steve Clark
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Post by Steve Clark » Thu Oct 19, 2006 6:36 pm

Andy:
At 2300 the depth of hull is OK?
Or at 2300 the depth of hull is OK only if the seat rails are included in the depth of hull measurement?
SHC
Beatings will continue until morale improves

Andy P
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Post by Andy P » Thu Oct 19, 2006 8:03 pm

at 2300 from the stern, the height to the top of the gunwale is a bit less than 300mm. ( more than that fwds, less aft. )
The seat rail base ( timber strip ) takes the height to just over 300mm.


Image

So i guess that the outside of the hull ( meaning top surface of the deck) is less than 300mm from the underside at 750 beam.

I've sold the boat, so can't check it.

Andy P
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Post by Andy P » Thu Oct 19, 2006 8:21 pm

The offsets say at section 9, 2438mm from stern, height to deck = 278 - 4 = 274mm, so maybe the 300 is too high to allow nethercotts to measure!

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