Interpretation of IOM CR - wind indicators & telltales

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Robert Grubisa
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Interpretation of IOM CR - wind indicators & telltales

Post by Robert Grubisa » 27 Dec 2013, 23:03

You may find on IOM ICA website request for interpretation of IOM Class Rules from USA NCA regarding clarification on the location of wind indicators and telltales.

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Robert Grubisa

jon ssimpson
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Re: Interpretation of IOM CR - wind indicators & telltales

Post by jon ssimpson » 27 Jan 2014, 21:46

IOM Interpretation on Tell Tails and Wind Indicators, IOMICA/IRSA Sub Comm

Robert,

This is posted per your email request for discussion of this interpretation to be public, and located on this thread. Perhaps interpretations generally should be carried out in this way to improve the transparency of the process – though readers should note that these were not drafted with a public forum in mind and are meant to be constructive exchanges of ideas & discussion aimed at reaching a reasonable conclusion, rather than error-free public position statements.

We all seem to agree on this except for the last part of question 2. Would you be able to help us understand your reasoning for the argument that Tell Tails trailing aft of the leech are permitted?

Ancillary comments below on the interaction between the term “spar” and “mast” in ERS can be ignored for this interpretation (so scroll on by if you like), but might be worth considering at some point as they are used more relevantly elsewhere in the IOM rule and could be clearer.

Regards
Jon

Question 1:
Under F.3 Mast a wind indicator and/or its fitting is optional under Fittings. No location restriction is given. Can a wind indicator be located anywhere on the mast, shrouds, backstay, or backstay crane?
Question 2:
Under G.3.1 Construction tell tales are optional. No location restriction is given. Can a tell tale be located anywhere on the mainsail, including trailing aft of the leech?
---------------------------------------------------

Robert G suggestions:

Answer on question 1:
Mast is ERS defined term:
F.1.4 Spar Types
(a) MAST
A spar on which the head or throat of a sail, or a yard, is set. Includes its standing rigging, running rigging, spreaders, fittings and any corrector weights, but not running rigging and fittings that are not essential to the function of the mast as part of the rig.
IOM Class Rule F.3.3 is related to the mast fittings so wind indicator may be located anywhere on the mast, shrouds, backstay, or backstay crane.

Answer on question 2:
A tell tale may be located anywhere on the mainsail, including trailing aft of the leech.


Discussion Notes Jon S & [Val Provoost in brackets]

Apologies in advance for length. Although I think the specific questions raised can be answered reasonably briefly, their consideration does raise a question of, at least clarity over, the ERS definition of MAST, so this is discussed.

1. Wind Indicator (and its fitting)

This is listed under F.3 MAST within F.3.3 FITTINGS (b) OPTIONAL.

It should be clear this is an item attached to the MAST.

This raises the question of what exactly is meant by MAST.

ERS:

Section F – Rig Definitions
F.1 GENERAL RIG TERMS

F.1.1 Rig
The spars, spreaders, rigging, fittings and any corrector weights.

F.1.3 Spar
The main structural part(s) of the rig, to, or from which sails are attached
and/or supported.

F.1.4 Spar Types
(a) MAST
A spar on which the head or throat of a sail, or a yard, is set. Includes its
standing rigging, running rigging, spreaders, fittings and any corrector
weights, but not running rigging and fittings that are not essential to the
function of the mast as part of the rig.

[VP: I imagine that the differentiation between one sort of running rigging and another relates to what is needed to hold the mast up (running backstays?) and what relates to the raising/lowering of the sails and their trimmimg]

_____________________________________________________________


Digression (scroll by if only strictly interested in the current RFI):


There are two different ways of interpreting this:

Mast Interp 1

Above, the term MAST appears to be defined as one particular type of “spar”. The definition then goes on to say it (this spar type) “includes” standing rigging, shrouds etc.

The use of the word “includes” tends to suggest that standing rigging, shrouds etc are to be regarded as part of this type of spar.

[VP: Remember that the mast spar is a defined part of the rig as a whole and so would include the rigging needed to hold the rig in the boat]


If the definition read:
(a) MAST SPAR
A spar on which the head or throat of a sail, or a yard, is set.

And seperately:
MAST:
A MAST SPAR plus its standing rigging, running rigging, spreaders, fittings and any corrector weights, but not running rigging and fittings that are not essential to the function of the mast as part of the rig.

…then we would have two distinct items “mast” and “mast spar”.

But it doesn’t.

This interpretation is inconvenient for the IOM CR, as for example:

F.3 MAST
F.3.1 MATERIALS
(a) The spar shall be aluminium alloy of 2024, 5754, 6005, 6060, 6061, 6063, 6082 or 7075 grade, or wood.

Would cause a conflict with fittings, spreaders, shrouds and other items which are regarded as part of the spar will not be made of the appropriate materials. (Shrouds & rigging are explicitly allowed elsewhere in the CR to be non- aluminium, but other items are not).


Mast Interp 2

The ERS definition, which defines MAST under “Spar Types”…

“F.1.4 Spar Types
(a) MAST
A spar on which the head or throat of a sail, or a yard, is set ..”

…..does not imply that a MAST is a spar., and

“ …Includes its standing rigging, running rigging, spreaders, fittings and any corrector weights…”

…does not not imply that these are to be regarded as part of a spar.


This interpretation is convenient for the IOM CR as F.3.1 MATERIALS refers to “the spar”

It is appealing and perhaps expedient to opt for Mast Interp 2 as Mast Interp 1 would cause inconvenience. However the way the ERS definition is worded it could be argued that Interp 1 is the more natural reading.

The IOM is not alone in having mast spar materials restrictions, so if I am reading this logically perhaps the definition of MAST could be made potentially less ambiguous in a future ERS re-draft?

There is further context in the following ERS definitions which support the case that Mast Interp 2 was at least the meaning assumed when the definition was drafted (eg. why would STANDING RIGGING be defined as “Rigging used to support a mast spar or hull spar.” …if it were already defined to be part of the mast spar?) viz:

F.1.5 Spreader
Equipment used to brace a spar, attached at one end to the spar and the other end to rigging and working in compression when in use.
F.1.6 Rigging
Any equipment attached at one or both ends to spars, sails or other rigging and capable of working in tension only. Includes associated fittings which are not permanently fixed to a hull, spar or spreader.

F.1.7 Rigging Types
(a) STANDING RIGGING
Rigging used to support a mast spar or hull spar. It may be adjustable.
Standing Rigging types:
(i) SHROUD
Rigging used to provide transverse support for a mast spar or hull
spar and which may also provide longitudinal support and is not
detached when racing.
(ii) STAY
Rigging mainly used to provide longitudinal support for a mast spar
or hull spar or a sail.
(iii) FORESTAY
Rigging used to provide forward support for a mast spar and is not
detached when racing.
(b) RUNNING RIGGING
Rigging primarily used to adjust a spar, a sail or a hull appendage.
Running Rigging types:
(i) HALYARD
Rigging used to hoist a sail, spar, flag or a combination thereof.
(ii) BACKSTAY
Rigging mainly used to provide aft support for a mast spar above the
upper limit mark.
(iii) RUNNING BACKSTAY
Rigging used to provide aft support for a mast spar at a point, or
points, between the upper limit mark and the forestay rigging point.
(iv) CHECKSTAY
Rigging used to provide aft support for a mast spar at a point, or
points, between the lower limit mark and the forestay rigging point.
(v) OUTHAUL
Rigging used to trim the clew of a sail along a boom spar.
(vi) SHEET
Rigging used to trim the clew of a sail, or a boom spar.
(vii) SPINNAKER GUY
Rigging used to trim the tack of a spinnaker.

(Digression ends)
_____________________________________________________________

Back to the current RFI

Suggested Conclusion:

As “wind indicator” is a fitting or device attached to the MAST rather than “the mast spar” or “the spar” it should be clear that whichever of Mast Interp 1 or Mast Interp 2 (see above) is chosen the MAST includes “standing rigging, running rigging, spreaders, fittings and any corrector weights” therefore the wind indicator may be attached to any of those, but not to “running rigging and fittings that are not essential to the function of the mast as part of the rig.”

Note: Wind indicator is singular.


2. Tell Tales

I am not aware of a definition of “Tell Tales” in ERS.

They appear in the IOM CR under

G.3 MAINSAIL
G.3.1 CONSTRUCTION
(b) OPTIONAL

ERS defines Sail as follows:

G.1 GENERAL SAIL TERMS
G.1.1 Sail
An item of equipment, used to propel the boat. It includes any of the following
added parts:
sail reinforcements
batten pockets
windows
stiffening
tabling
sail edge ropes and wires
attachments
other parts as permitted by class rules.


ERS has a list of attachments which does not include “Tell Tales”. If we were to interpret this list as exhaustive, then “Tell Tales” must be “ other parts as permitted by class rules”.

(Most) attachments are not measured.

Presumably therefore, “ other parts as permitted by class rules “ should be measured. If so then flying aft of the leech would not be allowed.

As 'they are listed as part of the sail and therefore could be argued to be: “used to propel the boat. […]”
(if only by assisting sail setting decisions), perhaps they should be limited to not beyond the sail edges.

If they were permitted beyond the leech would IOMICA not at some point have to define their allowed stiffness and / or size and number to prevent them being stiff enough to effectively function as additional, unmeasured, sail area?

The alternative way to deal with ‘Tell Tails’ would be to regard them as “Attachments” (which they intuitively are) and allow them to fly aft of the leech (where they might entangle with the backstay or other rigging), but it would seem this would require an addition to the IOMICA Class Rule defining them as “Attachments” which do not require measurement.

Therefore, their position is not restricted but they cannot extend aft of the leech.

JS

[VP:Keep it simple and restrict the placing of tell tales to within the perimeter of the sail(s)]


[VP: I have made entries above in the text. But having discussed the clunkiness of the definitions as set out in ERS with Bas Edmonds (ISAF), his take on it is that ERS sets out to define a section of the boat or equipment and then expands on the individual components. Hence Rig is followed by Spar followed by the individual types of spar (mast spar etc). However no-one at ISAF or RSD ever thought about the major difference between us and the rest. Our rigs are not factory made and supplied ready for use whereas we build ours up from components. The factory made item comes with a certificate of compliance to class rules but until recently our tubes, for masts carried no such advice of compliance. So a mast in our perception, is just the tube so the iom rules, with that statement about alloy types was intended to apply only to that whereas ERS reacts differently to it. One way out of the mess is to declare that ERS doesnt apply and to suggest IOMICA might consider whether to use less bold print in the section about spars. Quite legal and very simple to do, if they want.

Wind indicator.
In my opinion, a wind indicator acts to display the wind direction relative to the heading of the boat and telltales indicate the flow of air over the surface of the sail. Even if the telltales project aft of the sail they are not indicating the wind and, if they spend their time ‘motorboating’ like an unsupported leech will neither show the true wind or the flow. As stated above, by taking the ERS definition of the mast out of the Class rule, this would also resolve the windicator problem (if a wind indicator positioned on rigging etc were to be regarded as a problem) by using the term ‘mast tube’ or similar.]

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Re: Interpretation of IOM CR - wind indicators & telltales

Post by Lester » 01 Feb 2014, 14:11

I would agree that "other parts as permitted by class rules" should be measured, and so tell-tales flying aft of the leech would probably fail measurement. Not quite contrary to the proposed interpretation, since (strictly speaking), a tell-tale flying aft of the leech is permitted if it flies inside the leech stiffening zone (but not otherwise)...!

If a class rule change defined a tell-tale as an attachment, the change would also have to define a tell-tale, presumably as to stiffness and size, as Jon notes. Then, it could fly anywhere it likes.

If leech tell-tales are measured, why would they probably fail measurement? This started for me a while back, as I report here
http://www.onemetre.net/Race/Telltale/LeechFly.htm, and now I have an explanation of why a tell-tale (leech fly) would have trouble measuring on an IOM mainsail leech. Actually, it *would* measure, but only if it was no longer than around 5 mm and was inside the leech stiffening zone...!

Class Rule H.3.1 says that a “leach stiffening zone” is a zone which is the shape of the CR H.3.2 template. So within that zone, the leech can fall anywhere. But outside of that zone, the leech must not be aft of the relevant straight lines described in the remainder of CR G.3.1(a)(5). The leech is the aft edge of the sail. The sail includes tell tales as permitted parts but these are not excluded from measurement. So a tell tale flying aft of the leech could only do so within the leech stiffening zone, and would need to be no more than around 5 mm long to be able to be covered by the template (!).

Some further discussion:
jon ssimpson wrote:Robert, This is posted per your email request for discussion of this interpretation to be public, and located on this thread.
Just for background information, I'm guessing that this discussion is from the joint IRSA/IOMICA sub-committee whose task is to approve (or not) Class Rule interpretations from IOMICA. So I understand that the IOMICA interpretation is that a wind indicator may be located anywhere on the mast, shrouds, backstay, or backstay crane, and that a tell tale may be located anywhere on the mainsail, including trailing aft of the leech. And I understand that it is this IOMICA interpretation which is being discussed in the joint IRSA/IOMICA sub-committee, which consists of three persons, one IOMICA representative (Robert) and two IRSA representatives (Val and yourself).
Perhaps interpretations generally should be carried out in this way to improve the transparency of the process – though readers should note that these were not drafted with a public forum in mind and are meant to be constructive exchanges of ideas & discussion aimed at reaching a reasonable conclusion, rather than error-free public position statements.
I entirely agree, and (to make a political point, sorry!) it is part of the CEEFIE manifesto for the forthcoming IRSA Executive Committee elections that it is exactly this kind of discussion in IRSA committees that should be transparent.
F.1.4 Spar Types
(a) MAST
A spar on which the head or throat of a sail, or a yard, is set. Includes its standing rigging, running rigging, spreaders, fittings and any corrector weights, but not running rigging and fittings that are not essential to the function of the mast as part of the rig.

There are two different ways of interpreting this:

Mast Interp 1
Above, the term MAST appears to be defined as one particular type of “spar”. The definition then goes on to say it (this spar type) “includes” standing rigging, shrouds etc.
The use of the word “includes” tends to suggest that standing rigging, shrouds etc are to be regarded as part of this type of spar.

This interpretation is inconvenient for the IOM CR, as for example:

F.3 MAST
F.3.1 MATERIALS
(a) The spar shall be aluminium alloy of 2024, 5754, 6005, 6060, 6061, 6063, 6082 or 7075 grade, or wood.

Would cause a conflict with fittings, spreaders, shrouds and other items which are regarded as part of the spar will not be made of the appropriate materials.
I can sympathise with your suggestion that there may be a conflict, but I think the ERS does allow us to talk about the "mast" as distinct from the "mast spar". And in this case the IOM rule about the materials permitted for the "mast spar" does not conflict with the fact that the "mast" includes fittings etc which are not made of these permitted materials.
(Most) attachments are not measured.
A useful rule, ERS H.5.3, indeed tells us that *attachments* (ie as defined in ERS G.1.4(o)) at a sail edge shall be excluded:

H.5.3 Excluding Attachments
Attachments at a sail edge, other than a bolt rope and tabling, shall be excluded when measuring.
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Re: Interpretation of IOM CR - wind indicators & telltales

Post by Hiljoball » 01 Feb 2014, 22:58

There may be a simpler way to look at these questions and that is to focus on the word 'optional'.

While we think of optional as the presence or absence of . . .it could also relate to the location being optional - ie anywhere.

So for Q1, anywhere on the mast or masthead fitting or standing rigging.

and for Q2, anywhere on the sail, including the leach.

John
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Re: Interpretation of IOM CR - wind indicators & telltales

Post by jon ssimpson » 10 Feb 2014, 00:04

Lester,

Although it's incumbant upon the respective TCs to consider the possibility that skippers might use tell tails to effectively stick on a patch of sail material overlapping the leech which they claim is a tell tail, I think we have to remember that many would just want to use a long, thin very flexible strip secured at the forward end. I'm not sure measurers and event officials would welcome an interpretation which placed them in the position of having to decide whether each tell tail could be guaranteed to remain within the small stiffening zones while being blown about by the wind.

I might be wrong, but it seems the only way this could actually be guaranteed is if the tell tail was very short and stuck to the sail very close to the leech so that it could not blow around much. Although there is no definition of 'tell tail' these could be argued to be anything but tell tails, er, by definition, if you know what I mean.

I wonder whether, if they were allowed, there might be a fashion for such 'stickers' to be added to the largest sails to claim the tiny amount of extra sail area.

If this can be avoided it probably should be.

With regard to the process my understanding is at some point there has to be a vote of the three, but I'm not sure it is sensible to do so until we have the reasoning behing the decision tell tales can fly aft of the leech, as it could easily be more convincing than that above.

It would be easy for IOMICA to subsequently define tell tails as, say, less than 10mm wide and restrict their number per sail which would make this RFI academic.

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Re: Interpretation of IOM CR - wind indicators & telltales

Post by Lester » 10 Feb 2014, 09:45

Hi Jon

A couple of comments on process.
jon ssimpson wrote:It would be easy for IOMICA to subsequently define tell tails
Not so sure that this would be *easy*...! It would be a class rule change, and so the necessary words would need to be carefully drafted by the TC, published for comments and criticism, re-drafted if needed, communicated to all NCAs, voted on at an AGM or similar, and (if passed) go to IRSA for approval under Regulation 14 (see below).
jon ssimpson wrote:would make this RFI academic
Sure, that's the idea. The IRSA regulations on interpretations are intended to ensure they *are* made "academic" within a reasonable time frame (two years).
IRSA Regulations wrote:6.3.2(e) rule interpretations shall have the status of a class rule and [...] shall remain valid for a maximum period of 2 years or until superseded by a class rule change or modification carried out following the procedures of Regulation 6.5.
[Just to make a political point in advance of the IRSA elections, a large number of important interpretations with regard to the other classes are older than two years yet the relevant class rules have not been properly managed to either incorporate them or to clarify the rule so the need for the interpretation no longer applies. The CEEFIE manifesto makes it clear that some cleaning out of the Augean Stables is needed here...

And another political point, we see IRSA Regulation 6.3.2(e) refers to 6.5. Well, 6.5 does not exist. We must assume it intends to refer to Regulation 14. The CEEFIE manifesto tells us that the IRSA Constitution and Regulations are in serious need of attention here...]
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Re: Interpretation of IOM CR - wind indicators & telltales

Post by jon ssimpson » 13 Feb 2014, 20:05

Lester,

In suggesting it IOMICA could easily change the rule so that this interpretation becomes academic I was referring to the fact that, I think, it would be fairly straightforward and un-controversial to define what a 'tell tale' is - you might not even have to bother with stiffness for example.

You could start with maximum width (eg 10mm) & minimum length not adhering to body of sail, etc. If you restricted the number per sail then you don't have really have any potential attempt to gain sail area. That would mean that if this RFI were resolved by a allowing 'tell tails' to fly aft of the leech, any sail area gained would be completely trivial.

On defining them, you can choose whether to define them as un-measured.

I wasn't suggesting the rule change wouldn't have to go through the usual procedure.

On IRSA reg 6.3.2(e) I think the most sensible way of administering this should depend on the nature of the interpretation.

a) interprets meaning of existing wording in particular circumstance as it was not clear to a questioner
b) amounts to an effective extension of the rule, say, to a circumstance which the CR wording does not provide an answer.

Many interpretations fall into category a) and there may be no need for a CR change. If they fall into category b) then there should be. Interps from IOMICA on moulded sails from many years ago, and again in 2011 and also 'Winged' rudders for example haven't been followed by rule changes (so far as I know).

In category a) the interpretation doesn't really need to become 'academic' as such because it provides a precedent. Some would be very clear and others less so. The old precedent from the ruling against moulded sails was revisited and the newer interpretation seems to make more sense.

Where an interp is only reached with a very split decision, it seems to be difficult in practice to change class rules.

Not directly relevant to this thread, but as an example, during discussions on an interpretation of whether GB's unusual A class sails were 'basically triangular' and CR compliant TC noticed that since the re-draft by the Class Association in 1992 the CR seemed to allow more than one rig (via the MF) to be registered (not used at an event though). At that point nobody (as far as I know) had introduced this feature into the fleet so a rule change would not necessarily fracture the fleet, disadvantage any competitors or suppliers etc, and there was a UK-centric preference to interpret it as an error. Further discussion pointed up that doing so would not prevent an owner from possessing more than one rig provided he had convenient access to a helpful measurer who would issue new certs prior to rig swaps - thus handing an advantage to some competitors & no consensus could be reached. The ERS CR update cannot facilitate that ambiguity and needs this to be clarified and wide consultation (whether via a structure you advocate, or some other, or by contact with skippers etc, or using discussion boards) will need to take place.

On the other hand, there is a partial 10R re-draft prompted by the MYA which has proceeded smoothly and is most of the way there - there are currently no contentious items in it and wide consultation on it could be straightforward, maybe. There is an out of date 10R interp that has lapsed, is under review and which several members of the TC currently think is, in one aspect, unsatisfactory.

With regard to the IRSA regulations etc, I'm on record as saying these are a mess so you don't need to go all political on me. I also have nothing to do with the IRSA Executive Committee, nor am I better informed about it than you.

You might also note the pages on the IOMICA website describing the interaction with IRSA TC also still refer to RSD.

Before this interp can sensibly go to a vote, the reasoning behind the 'tell tales can fly aft of the leech' argument is needed.

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Re: Interpretation of IOM CR - wind indicators & telltales

Post by jon ssimpson » 26 Apr 2014, 21:23

Earlier in this thread I asked if people could suggest arguments that would allow this interpretation to be concluded in line with that originally suggested by IOMICA wrt the last part – tell tails flying aft of the leech. Although I doubt anyone has any particular interest in preventing this, as outlined above, it was not clear (to me at least) how this followed from the CR and ERS as written.

It would be very helpful if salient pro ‘aft of leech’ points on this could be outlined so a fully informed vote can go ahead. In case it assists, irsa TC had a go at pro ‘aft of leech’ arguments after this thread went dormant, and some of the points raised are summarised below.

1. Tell tales are listed as optional construction on the headsail and mainsail and can therefore be located anywhere on the respective sails. (Optional meaning not only ‘may or may not be used’ but also ‘unrestricted if used’).

2. Tell tails are unrestricted in size and their positioning is not restricted, therefore, by inference they may fly aft of the leech.

3. In considering the potential for that part of a tell tale which might overhang the leech to have sufficient stiffness that it could provide additional propulsive force, the discussion goes beyond the original request for interpretation of location and is unnecessary.

4. In considering the unrestricted width or number of tell tales and for that part of them which might overhang the leech to provide additional propulsive force, the discussion goes beyond the original request for interpretation of location and is unnecessary.

5. ERS does not define tell tales and Olympic ISAF classes such as the Finn have not restricted tell tales flying aft of the leech and this can be used as a precedent.

6. The lack of a definition of ‘tell tale’ either in the class rule or ERS does in the context of overhanging the leech does not create a difficulty for skippers, event officials or measurers as they can recognise a tell tale. (cf. Justice Potter Stewart's “I know it when I see it”).

Some follow-on points from that are:

1. It appears that we would need to interpret ‘tell tails’ as attachments (as per above, “which they intuitively are”) and to interpret the ERS list as non-exhaustive.

2. Without a definition of ‘tell tale’ “I know it when I see it” invites inconsistency in measuring. Many tell tales are strips of very thin tape, but in principle anything which has a flexible enough attachment point to the sail to react to a separation bubble in the flow on the leeward side of a sail could be argued to be a ‘tell tale’.

3. Additional effective sail area may or may not be so trivial that it can be ignored for IOMs, but it would be much more trivial for full size boats. Simplistically, consider a sail trimmed downwind. The windward tell tales (if relatively stiff) bend to leeward under air pressure. There will be, roughly speaking, a radius of curvature after which no propulsive force will arise. On a Finn sail this will be negligible but less so in comparison to the size of an IOM sail.

Are there any additional points?

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Re: Interpretation of IOM CR - wind indicators & telltales

Post by Robert Grubisa » 11 Aug 2014, 15:36

Please note that IOM Class Rules interpretations and emergency class changes are published under Class Rules sections of IOM ICA website.
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Re: Interpretation of IOM CR - wind indicators & telltales

Post by James Chrismas » 18 Aug 2014, 16:07

With all due respect to all involved in this discussion, it seems to me that the simplest way to get round this lawyers delight is to specifically include tell tails as an optional fitting. By all means restrict their size, weight of cloth and number, 'though I can't see a real need to do so as anything excessive would undoubtedly hinder the performance of the sails.

Best regards,

James
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Re: Interpretation of IOM CR - wind indicators & telltales

Post by James Chrismas » 02 Sep 2014, 11:54

jon ssimpson wrote:It would be very helpful if salient pro ‘aft of leech’ points on this could be outlined so a fully informed vote can go ahead.
I think the RYA's advice under "Boat Handling - Sail" explains the reason for having leach tell tales on the mainsail more than adequately.
Adjust the mainsheet so that the top batten is roughly parallel with the boom or the top telltale streams straight out from the leech.

Too much sheet tension and the top telltale will fall to leeward as the leech closes and twist is reduced.
The link for this quotation is:http://www.rya.org.uk/cruising/handling ... nsail.aspx
If you want more examples you only need Google "where should I put mainsail tell tales" or "where do sail makers put mainsail tell tales".
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Re: Interpretation of IOM CR - wind indicators & telltales

Post by jon ssimpson » 03 Sep 2014, 02:04

James I think we were aware of the reasons why tell tales in their various possible locations might be useful but this thread was about their compliance or otherwise with the class rule as written. The request for " salient pro ‘aft of leech’ points " was an attempt to ensure that all relevant arguments relating to compliance were known and fully discussed prior to voting.

Per Robert's post above this interpretation has now been published on the IOMICA site along with overriding class rule changes effected by IOMICA.

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