Oval Foredeck holes

Olivier Cohen · Post by **Olivier Cohen** » 18 Oct 2005, 16:10

I've read this article by P. Stollery : http://www.intersail.co.uk/news/?article=19235

and I have a question about this part :

"In particular, Michael's approach to IOM design has certainly opened a few eyes to what is possible with these competitive boats and it was no surprise to see that his oval foredeck holes, which allow the jib pivot to drop down to leeward when hard pressed, had appeared on the new generation of Cockatoos."

May somebody explain how it works, how it is made, and maybe its interest?

awallin · Post by **awallin** » 18 Oct 2005, 23:26

Here's a picture of the foredeck on Michaels boat:

The new cockatoos had more moderately oval holes and only for the no1 rig if I remember correctly.

A couple of years ago there was some discussion about this way of attaching the jib - related to what is now Class Rule C.7.6

C.7.6 STANDING RIGGING USE
The headsail boom swivel shall be attached to the hull approximately on the hull centreplane. The alignment of the swivel between the hull and the headsail boom shall be controlled only by the rigging tension.

I guess owners of these boats will claim that the headsail boom swivel is located close to the bottom of the boat and therefore stays on the centerplane even though the jib boom is free to move laterally.

personaly I don't see it as a good thing for the class if the jib attachment becomes overly complicated to build.

Anders

Lester · Post by **Lester** » 19 Oct 2005, 18:52

VCinfocomms wrote:I guess owners of these boats will claim that the headsail boom swivel is located close to the bottom of the boat and therefore stays on the centerplane even though the jib boom is free to move laterally.

Hi Anders

Great photo, thanks! Yup, I'd guess that it meets the "approximately attached to centreline" part. But, I don't know about meeting the "alignment controlled only by tension" part. I think the last time this was looked at, opinion was divided as to whether the SAILSetc method (small round hole in foredeck) met this requirement when wind pressure pushes the swivel cord to rest on the edge of the hole.

If the hole is in fact a slot, then a little simple engineering could have the slot more of an arrow-head shape pointing aft (or an oval shape would work similarly). In this case, swivel tension would be increased as wind pressure tries to push it off centre... Now, is this affecting the alignment of the swivel? And, if it *is* affecting the alignment, is this alignment being *controlled* by anything other than swivel tension? Hmmm...! Nice one.

kure · Post by **kure** » 20 Oct 2005, 10:47

Hello,
I find the whole thing strange. Isn't this a discussion about boats that where accepted in the Worlds? As I understand, the Cockatoo is sporting this feature in production already ?
I should think that producers and designers should check their "inventions" leagality before putting them to use.....

Is this a new "texalium" problem araising?

Lester · Post by **Lester** » 20 Oct 2005, 12:46

kure wrote:I should think that producers and designers should check their "inventions" leagality before putting them to use..... Is this a new "texalium" problem araising?

Hi Kure

As a result of the "Texalium problem", IOMICA has official advice on the class rules and new ideas.

http://iomclass.org/technical.htm wrote:If you are a commercial supplier to the IOM class:
Treat new ideas as if they are probably illegal.

Convince yourself that it is not so before marketing the equipment.

Consider asking the IOMICA Technical Sub-Committee for an interpretation.

Perhaps someone has a photo of the Cockatoo foredeck they could post.

ole_peder · Post by **ole_peder** » 20 Oct 2005, 14:25

One of the main ideas behind the IOM is simplicity and low cost.
The introduction to the rules also state that :

"The rules in Part II and III are closed class rules which means that anything not specifically permitted is prohibited."

I can not find that oval holes in the deck is permitted.

The problem is that the rules uses hull and not deck for the attachment point.

This feature is a typical example of what complicates the building of an IOM and also raises the cost, and I am not sure that most of us wants this.

I am in favour of craetivity, but not on these issues. Creativity to create simpler and cheaper designs gains the class, not the opposite.

The MArblehead is an great class for all the creative people that want to make all sorts of gadgets.

It is still possible to design and homebuild an IOM that is competetive, let us keep it that way.

So please stop reading the rules to find loopholes, there are plenty of them not discovered yet. Let us go out there sailing and have fun.

awallin · Post by **awallin** » 20 Oct 2005, 20:41

Lester wrote: Perhaps someone has a photo of the Cockatoo foredeck they could post.

hmm this one is the best I can find... and it's not very good.

with a little imagination you can make out a nearly square hole for the no1 jib (I think theres a no2 jib in the pic) - I would estimate it's about half as wide as the foredeck holes on Micahels boat.

I only saw this on 2-3 new cockatoos.

Anders

cfwahl · Post by **cfwahl** » 21 Oct 2005, 02:51

Besides being of dubious, imaginary or trifling utility, this "swivel down the hole" stuff is, as Ole Peder pointed out, an egregious example of playing the loopholes. I, for one, would favor a change in the rules that explicitly requires the moving parts of jib swivel/attachment to be entirely above a straight line (like a rod) placed athwartships on the deck surface.

David Turton · Post by **David Turton** » 21 Oct 2005, 03:18

Putting the rule interpretations aside for a minute.
Has any one else established if there is an advantage in doing this or the pros and cons. What's being gained, what's being lost? lets work it out.

Has anyone worked out the process of retrofitting a tube and how expensive/inexpensive/simple/complex it is?

Lets establish some of the outcomes first.

RoyL · Post by **RoyL** » 21 Oct 2005, 06:06

Very good points David. I would love to hear an analysis of the claimed benefits of this jib attachement system.

I also think it would be appropriate to invite disucssion among the class members about this system and then vote on whether it should be permitted.

It would seem to me that if this system is banned, a boat already using it could be put back into compliance by simply taping acetate across the oval jib slot.

On the other hand, retrofitting existing boats that now use a deck mounted swivel would seem to involve some major surgery on the foredeck.

Finally, like Charile Wahl I have never been comfortable with the "intrepretation" that allowed the attachment of the jib via a line to a point at the bottom of the hull. I think it is an appropriate question to be revisited. While I would favor a rule that mandated the jib be attached via a centerline swivel to the deck, I would not want to see any existing boats banned.

Andy Stevenson · Post by **Andy Stevenson** » 21 Oct 2005, 11:23

DT wrote:Has any one else established if there is an advantage in doing this or the pros and cons. What's being gained, what's being lost? lets work it out.

Good question, I've been thinking about this too...

Lester points out a little further down in the thread that the jib pivot tension will increase, as will jibstay & topping lift I would assume. This could be either good or bad depending on the static tension it was set up with in the first place, but with such a small amount of movement I can't see it being much of a good or bad thing either way.

A larger change will happen at the other end of the boom I think. As wind speed increases the jib pivot moves over & the slot increases proportionally without changing the angle of attack. More wind - bigger slot. The effect will become proportionally less as we sheet out from close hauled up to a point when the forces are acting mostly forward & having no effect at all, but we don't need a slot all the way out there

Exactly how this is going to effect the boat I'm still thinking about, but "stronger wind - bigger slot" seems like a good thing.

Feel free to shoot this down in flames, I'm no expert. Just fancied getting the ball rolling.

Lester · Post by **Lester** » 21 Oct 2005, 11:50

Three areas for debate, perhaps.

One is whether, and how, this arrangement might work.
Two is, regardless of any performance or other implications, *is* it legal?
Three, and regardless of whether it is currently permitted or not, *should* it be legal?

We can (and will!) enjoy ourselves figuring out if it works. Contrary to Charles, my opinion is anything that helps tension the forestay in a gust, and opens the slot in a controlled way, is welcome and will make a difference.

Whether it *is* legal or not can only be answered by an official interpretation. Not really an issue that we can adequately debate, though I'm sure we all have opinions on how to read the relevant rule, and we could air them as well. Perhaps the manufacturer of the Cockatoo would ask for an interpretation, now that there is some doubt.

Whether it *should be* permitted is an excellent topic for debate and, in due course, perhaps a vote of the World Council if there is enough enthusiasm.

There is also a fourth topic, of course: following an interpretation, there will be the question of what to do about existing boats. The class does need a principled debate around the general question of what to do about existing boats if any interpretation (bent wire at mast head, piece of wire on sail luff, Texalium in the hull, ...) finds them out of class. The class really must address the issue of manufacturers driving class development rather than the owners.

Andy Stevenson · Post by **Andy Stevenson** » 21 Oct 2005, 12:23

As far as the legality of the arrangement goes; The swivel attachment is legal I think.

The headsail boom swivel shall be attached to the hull approximately on the hull centreplane.

No mention of it needing to be anywhere specific vertically.

Itâ€™s legal from an alignment point of view I think, until it hits the limit of the hole. Up to that point the alignment is controlled by tension only, once it hits the side of the hole the alignment is controlled by tension in the rigging & the position of the hole edge.

So long as the hole is big enough that the pivot wonâ€™t come up against it Iâ€™m confident itâ€™s within class regs. Iâ€™m also confident this isnâ€™t the case with the two pictures Iâ€™ve seen so far.

Perhaps we should do away with the deck?

Roy Thompson · Post by **Roy Thompson** » 21 Oct 2005, 12:26

The class really must address the issue of manufacturers driving class development rather than the owners.

IOMICA has official advice on the class rules and new ideas.

http://iomclass.org/technical.htm wrote:
If you are a commercial supplier to the IOM class:

Treat new ideas as if they are probably illegal.

Convince yourself that it is not so before marketing the equipment.

Consider asking the IOMICA Technical Sub-Committee for an interpretation.

Whilst you could argue that Michael is an owner and manufactures only for 'himself', it seems that other the Cockatoo manufacturers haven't read or have chosen to ignor the IOMICA official advice - or maybe they have skipped the first piece of advice and convinced themselves that it is legal.
Maybe they could tell us what has been their thought process regarding the legality of this 'invention'...................

kure · Post by **kure** » 21 Oct 2005, 12:57

As I mentioned earlier this is becoming a new Texaluim issue.

Again some owners think that boats already built shall get a "get out of jail" card. I don't think so, what is the point of rules then ?
The first ten owners to break them can continue, the rest must stick to the rules ?

The rules is known to all owners and builders, so I don't see any need to let some boats be allowed to sail, when they do not comlpy to the rules.

The right people must decide on this issue, and if it gets banned, then the ones that are interested must try to get the rules changed - before - these boats gets certfied.

That's what I think.

Andy Stevenson · Post by **Andy Stevenson** » 21 Oct 2005, 13:42

Lester wrote:The class really must address the issue of manufacturers driving class development rather than the owners.

Do manufacturers market boats as class legal? Iâ€™ve not bought a new boat, so havenâ€™t really looked into it too much, but isnâ€™t the onus on the skipper to buy something appropriate for his use.

If someone buys a Cockatoo with no intention of having it measured or doing any serious racing, then s/he doesnâ€™t much mind if the jib swivel (or anything else for that matter) is class legal or not.

If, however, that same someone has every intention of serious competition within the class then I would suggest itâ€™s their responsibility to ensure the boatâ€™s legal before they part with their hard earned. Iâ€™m not suggesting that the manufacturer has no responsibility, far from it. But ultimately itâ€™s down to us, as owners/skippers to ensure the boat we compete with is legal.

If youâ€™re sailing a boat thatâ€™s been measured & registered then your ok, arenâ€™t you?

A.13.1 A boat ceases to comply with the class rules upon:

(d) a change of class rules that causes equipment in use to cease to be permitted, except where the equipment may comply with the class rules in force at the time of its initial fundamental measurement.

Surely the fact that it passed measurement at the time means it complied with the class rules in force? This would suggest to me that those boats that no longer comply due to a subsequent change in the class rules will continue to be legal until such time as re-registration is required for whatever reason.

Once a boat no longer complies I would imagine manufactures would be reasonably quick to modify their boats if they wish to continue to sell to the competitive majority of their customers.

Lester · Post by **Lester** » 21 Oct 2005, 14:34

andy111 wrote:If youâ€™re sailing a boat thatâ€™s been measured & registered then you're ok, arenâ€™t you?

If only! Measurers are human as well. An otherwise perfectly valid measurement certificate is no guarantee that your boat is in fact class legal.

isnâ€™t the onus on the skipper to buy something appropriate for his use

Certainly. And an owner is entitled to rely upon the representations of a reputable manufacturer that the hull meets the class rules.

David Turton · Post by **David Turton** » 21 Oct 2005, 15:20

Have retrofitted a system with a fully enclosed deck, not hard and didn't take long. A deck with easier access would make the glue job at the bottom of the boat neater.

Now having used the system there is a couple of observations which i'm not sure are fast.
1. the jib forestay now pumps and it is much harder to hold tension, with a couple of refinements this can and has been improved but not fixed completeley.
2. sailing at any angle when the pivot moves it changes your jib sheeting angle.
ie when sailing upwind the pivot moves to leeward effectively decreasing the sheeting angle. when running the pivot moves around a fair bit.

i have used pivot slots from 5mm to 70mm across the boat and from 3mm to 10mm fore & aft wide(they arn't hard to make just like anything a little time consuming), my observation was the wider they were the more difficult to consistantly control your jib trim. for me the jury is still out wether it works.

Boats have now sailied in Euro's 2004 and Worlds 2005 with many people present and there use well documented. I understand they have been around in various forms for a lot longer. Boats using this system at the last worlds results spread from top ten too all the way down to the 70's. I can't see boats without this system being suddenly obsoleted or slow in comparison. (may be quite the contrary)

In my mind as the rule reads they measure so any change would require a rule rewrite. I'll leave the process of this to the experts. As i see it the key word is Hull,

Lester · Post by **Lester** » 21 Oct 2005, 16:15

DT wrote:As i see it the key word is Hull

Hi David

I think you have hit the nail squarely on the head.

Andy Stevenson · Post by **Andy Stevenson** » 21 Oct 2005, 16:19

Lester wrote:If only! Measurers are human as well. An otherwise perfectly valid measurement certificate is no guarantee that your boat is in fact class legal.

Having never attended an event that included event measurement I may well be getting out of my depth here, howeverâ€¦ I can see that there may well be a difference between your measured & certified class registered boat & mine, due to different measurers, the accuracy of their measurements & their interpretation of the rules. But doesnâ€™t a valid certificate fulfil the requirements of fundamental measurement, regardless of the accuracy of that measurement?

Or would it be the case that I may well turn up to my first international event & in the process of event measurement the measurer notices a fundamental measurement s/he feels doesnâ€™t comply, no amount of certificate waving will prevent me having to fix the "problem" before I can compete?

Certainly. And an owner is entitled to rely upon the representations of a reputable manufacturer that the hull meets the class rules.

I agree. If the manufacturer is actually representing the hull as class legal, then a buyer should be able to be confident that it is. My feeling is that this isnâ€™t the case & Iâ€™d certainly not rely on it. Given the obviously still evolving nature of the class rules this would be a difficult thing to achieve.

ole_peder · Post by **ole_peder** » 21 Oct 2005, 16:33

If this system gives an perfomance advance or not is not the question.

We are moving away from the basic idea, "keep it simple, as simple as possible, but no simpler " as Albert Einsein once said.

We must be very careful on how this comes out. If we are going to vote on every issue like this, we will lose control of where the class moves.

As I have pointe out before, the rules are closed, dont forget this basic principle. Based on this we can handle a lot of issues without requesting interpretations, just point out where in the rules it is permitted. In this case nowhere.

If we discover parts of the rules where the wording should have been different as in this case, where hull maybe should have been deck, well let us change it.

We have the oportunity to make a major revision to the rules after what happened in Mololooba. On major task must be adopt al the interpretations into the rules and also adjust the basis of the rules so we hopefully can avoid all this creativity to find loopholes.

Lester · Post by **Lester** » 21 Oct 2005, 18:08

andy111 wrote:no amount of certificate waving will prevent me having to fix the "problem" before I can compete?

Hi Andy

Indeed.

If the manufacturer is actually representing the hull as class legal, then a buyer should be able to be confident that it is. My feeling is that this isnâ€™t the case

Er, where does your feeling come from? Jeff Byerley, Cockatoo manufacturer, is widely regarded as reputable. I don't think there is much question that, if you purchased his Cockatoo, you'd expect to receive a boat that Jeff thought was class-legal.

http://members.optusnet.com.au/~jeffreybyerley/index.htm wrote:COCKATOO - A brand new IOM design, produced with the aid of a very complex CAD software program, MaxSurf. This boat is showing itself to be a â€œuser friendlyâ€

Andy Stevenson · Post by **Andy Stevenson** » 21 Oct 2005, 18:23

Lester wrote:Er, where does your feeling come from? Jeff Byerley, Cockatoo manufacturer, is widely regarded as reputable. I don't think there is much question that, if you purchased his Cockatoo, you'd expect to receive a boat that Jeff thought was class-legal.

Crikey no! Maybe I didnâ€™t word that too well. Iâ€™m in no way suggesting any of these guys are less that reputable. What I meant was I wouldnâ€™t be confident that the boat would be class legal, given the, umm, continuing conversation surrounding interpretation of the rules with every new idea.

Having said that, I canâ€™t see any producer of a hull, whoever they may be, being totally confident that their latest offering will always pass measurement. But I have no doubt at all that they feel itâ€™s class legal.

Roy Thompson · Post by **Roy Thompson** » 21 Oct 2005, 18:36

Having said that, I canâ€™t see any producer of a hull, whoever they may be, being totally confident that their latest offering will always pass measurement. But I have no doubt at all that they feel itâ€™s class legal

I think it might be the other way around Andy, they might be quite confident that it would pass certification even though they may have certain doubts that the novelty is or isn't class legal.
It goes back to what Lester said, the measurers are only human and can not make interpretations of the rules every 5 minutes (it's not their job to anyway). Anything which looks remotely different or suspicious could and maybe should more often be grounds for a measurer asking his NCA to ask for an official interpretation before issuing a certificate.

Lester · Post by **Lester** » 21 Oct 2005, 18:45

ole_peder wrote:the rules are closed ... we can handle a lot of issues without requesting interpretations, just point out where in the rules it is permitted. In this case nowhere

Hi Ole Peder

We might have had this conversation before, if so, please forgive me repeating myself.

There is a fundamental, logical, problem with "if it isn't explicitly permitted it is prohibited". The problem is that it is not possible to exhaustively list everything that is permitted (the list is infinite). There will always be matters which are, and must remain, implicit and understood. For example (this is a simple example, and does not stand up to very close examination, but it will do to make the point) "tell tales" as such are permitted, but there is nothing which explicitly permits them to be attached to a sail. Now this is, of course, understood -- there is no point permitting tell tales if somehow the rules prevent them actually being attached. And, there is nothing which permits metallised plastic tell tales as opposed to, say, dacron tell tales or even wool tell tales... Yet we all attach a wide variety of tell tales and regard them as permitted.

This does not mean that closed class rules are a bad idea. It just means that it is not possible to say "the rules do not permit oval deck holes" because they are not explicitly permitted. Neither are circular holes or a very large (infinite!) number of other implicitly understood things...

A little history might help: the difficulty here is with the definition, or lack of it, of what is a "deck". The rules refer to a swivel attachment to the hull, because it was not thought possible to require the swivel attachment to the deck. The problem was, just what, exactly, is "the deck"? How could it be defined so that everyone (erm, measurers and builders, really!) would be able to know what was "deck" and what was "not deck"? It turns out that all the possible definitions of "deck" were abandoned, the problem was left as insoluble, and attachment was to the "hull" instead. You will notice that there is no definition of "deck" in the ERS...

Roy Thompson · Post by **Roy Thompson** » 21 Oct 2005, 18:49

You will notice that there is no definition of "deck" in the ERS...

For those of you who don't want to look up the ERS, D1.1 states that the hull includes the deck but 'deck' isn't defined. I guess that means that the definition would be as we might find it in a (nautical) dictionary.

Andy Stevenson · Post by **Andy Stevenson** » 21 Oct 2005, 22:13

VCmeasurement wrote:I think it might be the other way around Andy, they might be quite confident that it would pass certification even though they may have certain doubts that the novelty is or isn't class legal.

Iâ€™m afraid I donâ€™t follow this. Iâ€™m quite prepared to accept that itâ€™s a lack of understanding on my part, but if one has doubts about the class legality of ones latest novelty, how can one be confident that itâ€™ll pass certification?

Especially given this on the measurement form:

If the official measurer has any doubt concerning the application of, or compliance of any part of the boat with the class rules he shall report it on the measurement form(s) before sending them to the certification authority and not sign measurement form(s) or sails.

What I was trying to get across was that a builder/designer/manufacturer may well have convinced themselves that their latest whizz bang doohickey is perfectly legal, but canâ€™t be 100% confident that a) All measurers will interpret the class rules as s/he has done & b) An interested 3rd party wonâ€™t come among & say "hang on a minute chaps, are we sure this is right?" with the ensuing discussions, possibly culminating in an official interpretation that renders said doohickey illegal.

The only safety net I can see is a request for an interpretation before production, obviously a move that would prove lengthy, costly & ultimately detrimental to the class I would have thought.

ralph kelley · Post by **ralph kelley** » 21 Oct 2005, 23:25

Since the official defination of the "hull" includes the deck, and there is no specific IOM requirement to attach the jib to the deck, but does require it to be attached to the hull on the centerline, it seems to me that both the Bantock approach (with a tube to the hull bottom) and the larger hole in the deck approach are legal. Seems like those doing the measurement at the Worlds did so too. Since the boats are a bit more difficult to build that way (with possibly some slight increase in manufacturing costs, which would be passed on the to the buyer), the manufacturers, and their customers, must think there could be a small advantage.

As long as it's legal, where is the problem?

We certainly have other features of the boat that are getting more refined, and somewaht more costly, over time too. Ball bearing goosenecks & ultra thin CF fins come to mind, as examples.

Now if the class wants to change the rule to mounting the swivel on the deck, and on centerline, that is OK as long as one grandfathers the existing craft as of the time that the new rule is implimented.

Ralph

Andy Stevenson · Post by **Andy Stevenson** » 21 Oct 2005, 23:43

ralph kelley wrote:Since the official defination of the "hull" includes the deck, and there is no specific IOM requirement to attach the jib to the deck, but does require it to be attached to the hull on the centerline, it seems to me that both the Bantock approach (with a tube to the hull bottom) and the larger hole in the deck approach are legal.

From an attachment point of view yes. However the rule also states:

The alignment of the swivel between the hull and the headsail boom shall be controlled only by the rigging tension.

Once the swivel (string down the hole) touches the outer limit of the hole, the alignment is no longer only controlled by the rigging tension, but also by the deck preventing further sideways movement.

RoyL · Post by **RoyL** » 21 Oct 2005, 23:50

Here we go again...

Actually, I think this issue is a great opportunity for the class to approach things in a better way.

I think this issue should not be decided by the technical committee "interpreting" the rules, but by the class members.

An open discussion should be first held here on the IOMICA forum and then the class members should vote if oval or other shaped holes in the deck as part of the jib attachment system should be legal.

The rules should then be written to reflect the outcome of the vote.

I would even go so far as to also suggest that the class conisder whether or not the rules should be returned to their original form and require the jib swivel to be attached to the deck. I have always thought the claim that no one can define a "deck" is silly. Show me 100 current IOMs and 100 current IOM owners and I bet everyone could identify the deck. One thing I always knew for sure was that the bottom of the hull wasn't the "deck".

In all cases however, unless there is a quick and easy fix to put boats that are rendered "illegal" by a rule change back into compliance, all such boats should be grandfathered for all purposes.

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