Arm winch and separate sheets

[Chairman]

As Anders notes in the "Arm winch" topic, the recent "IOM Interpretation 2003-4" has, amongst many other fascinating matters, made it clear (in my unofficial opinion!) that

• The mainsheet, and the jibsheet, can be attached to separate points on the arm, but
• only one control line is allowed.

Now a "control line" is not defined, but I think we can assume that a control line is any cord or elastic that attaches to a mainsheet or a jibsheet. And at this point, those of us who would like to attach the two sheets at different places on the arm have a difficulty -- two sheets allowed, but only one control line... Hmmm...

[ralph kelley]

Lester:

Depending on the geometry of the setup, there might be some advantages to having the two sheets attached to a swing arm winch at different radii. (That is the arrangement I used a few decades ago in the Marbleheads I built.)

Those of us using drum winches usually have one line leading from the winch to a common point, at which the two sheets are attached.

I would would prefer to think that the term "one control line" refers to having only one sheet actually leading to each sail's boom, thereby allowing both arrangements.

[Arvin S.]

Hey Ralf and Lester,

You are right Ralf about geometry of the arm having potential advantage.

We are talking probably of just 1 arm here. How about a double arm system like the ones used in Soling 1 meters. It is actually just a single piece of arm but the jib sheet is attached to one end of the arm, and the main is attached to the other and the servo pivot is at the center of the arm, sort of a T. I wonder if this is also allowed by the Rules.

If the rules only talk about one servo to control sails and just one "control line" then we can consider a double arm system as a "direct sheet attachement" and we can consider this legal right

Now gentlemen please clarify only, the rule states only 1 control line right, it does not specify where the Sheets should be attached on this control line right? So is it safe to say also that we can actually attach the Jib sheet on the control line, separate from the Main sheet?

As of now my main and jib are attached to the control arm through a plastic ring. I thought that I cannot say attach my jib sheet forward of where I attached my main sheet? If this is allowed, then we will have the same advantage as if you attach the jib and the main on different parts of servo arm right This way if you attach the jib sheet ahead of the main, the jib will open up first before the main.

The question is of course are all these legal?

TTFN
Arvin

[ralph kelley]

Arvin:

I am not the proper person to give you definative answers on your questions. I have no responsibility or authority in this area.

But is a boat is brought to me for measurement, and it has only one sail servo, I expect this boat would be legal. It it had two servos, one for the basic control and one to tweak the jib slot while underway, I would reject this craft.

Until advised otherwise, I will not look for anything related to the geometry of the sheeting of the two sails. There are all sorts of geometric combinations of arms, drums, jib and main boom geometries, deck lead positions and so forth that will all be acceptable with the provision that only one servo controls both sails and that no "underway" adjustments can be made. (Obviously, shoreside adjustments are legal)

I think this is the spirit and text of the Rules. Section C9.1(a) is clear that only one servo can be used for sail control and Section F.2.4 allows feedom for fitting the rig to the boat.

Let's not make this more complicated than necessary. One servo is the key issue.


Ralph

[Arvin S.]

Ralf,

Yes I tend to agree with you. I can't find anything in the class rules that does not permit the different arragements we can use with sail servos and Sail winches.

I am attaching a file I made, drawing some of the more popular arrangements I know. I hope that people who can confirm the legality of these configurations inform us.

I am not out to say that we should not deviate from the accepted or commonly used configurations. My main concern is that the IOM rule is very strict and I read somewhere in the forum, that if you have a new idea that, that one should "assume it is not permitted until proven that it is in fact permitted". Hmmm, I guess with all these rule talk I am becoming paranoid. But better safe than be found to be breaking a rule right?



Drawings 1 and 4
are already being used and thus are surely acceptable.
Drawing 2 is the idea we discussed about separate sheets being attached in different points of the sail arm
Drawing 3 is the double arm system which is typically used by Soling One meter boats.
Drawing 5 is the Drum winch version of Drawing 2, I think. It is curious that no one actually uses a separate attachment point for the jib sheet and the main sheet. So giving us the impression that it is not allowed. But then the class rules does not say anthing against it!

I really would like confirmation about all these configuration's legality. I do not want to start using a configuration that might prove to be illegal in the future or if my boat was measured.

Though if it was all up to me I agree with Ralf, this should not be controlled at all to make the rules more simple.

TTFN
Arvin

[Chairman]

Let's not make this more complicated than necessary.

Hi Ralph

Indeed. But equally, let's not simplify this so much that we end up with something that is not permitted. Simplifying it to just the number of servos involved disregards the rule dealing with a sheet control line:

C.7.7 RUNNING RIGGING
(a) The mainsail sheet and the headsail sheet may be worked by a sheet control line attached to the sheet control unit

[Chairman]

Drawing 2 is the idea we discussed about separate sheets being attached in different points of the sail arm
Drawing 3 is the double arm system which is typically used by Soling One meter boats.

Hi Arvin

Nice drawing. (A technical tip: line drawings render much better as a GIF file rather than a JPG.)

In a realistic installation in an IOM, each of the sheets shown in drawing 2 and drawing 3 need to be tensioned, presumably with an elastic line. The problem I see is that each elastic line is a "control line", and so you end up with two control lines per installation. I'm not sure two separate control lines are permitted.

Drawing 5 is the Drum winch version of Drawing 2, I think. It is curious that no one actually uses a separate attachment point for the jib sheet and the main sheet. So giving us the impression that it is not allowed. But then the class rules does not say anything against it!

Not an impression I've had. In my (unofficial!) opinion, the arrangement of drawing 5 is permitted.

[soeren_andresen]

The chairman wrote:

In a realistic installation in an IOM, each of the sheets shown in drawing 2 and drawing 3 need to be tensioned, presumably with an elastic line. The problem I see is that each elastic line is a "control line", and so you end up with two control lines per installation. I'm not sure two separate control lines are permitted.

I see your point, so how about this:



Here there are only one elastic attached to both main and jib sheet, and therefore only one control line.

[Chairman]

Here there are only one elastic attached to both main and jb sheet, and therefore only one control line.

Hi Soeren

Yes, this "work around" looks fine, IMHUO. It is a pity that such a "work around" seems necessary, and I wonder what the intention was originally to restrict the rigging to one control line. For example, in your diagram, what if you replace the (possibly expensive) turning block with, say, an (inexpensive) eyebolt, and tie the middle of the elastic (without cutting the elastic in two) to this eyebolt? Do we now have two control lines? Well, I'd guess we have two "effective" control lines... And so on...

This looks like something for the Technical Sub-Committee to consider

[ralph kelley]

Lester makes a good point that we do not want to go overboard on any simplification of our Rules. But the converse is also true.

But in this subject thread, we have to note that the text of C.7.7(a) uses the permissive word "may". So this Rule section allows, but does not require, a specific sheeting configuration.

Interestingly, Rule F.6.2 (Running Rigging) lists both mandatory and optional rigging, and the only place that the term "control line" is used in this section does not include sheeting systems, but on how the sails are attached to the spars.

Finally, I have never considered an elastic member of the sheeting system anything other than an element in a sheeting system. Arvin's sketch # 1 shows one well accepted use of two elements of a contol line, one elastic and the other (comparatively) non-elastic string. Arvin;s sketch # 4 shows a common loop system, which almost always has some elastic in the loop (although this sketch does not show the elastic element). So it is accepted that any elastic tensioning part of the sheeting system is acceptable.

Let's hope that this boils down to the use of a single servo for sail control.

I expect that the recent request for clarification of a belt drive for sail contol will reinforce this understanding. The text of the Interpetation Decision could clarify this issue once and for all.

Ralph

[Chairman]

... this "work around" looks fine ...

I think I've got this wrong. I've re-read the rule: "... a sheet control line attached to the sheet control unit ...", but in Soeren's diagram, the elastic nowhere attaches to the sheet control unit. Oops.

[cfwahl]

Here's some food for thought: in a plain-vanilla drum-winch installation that you can see at any sailing venue, there are actually two separate physical lengths of line, each connected the drum on one end, and to each other at a ring or other fitting where the sheets attach to the "circuit." The line that has the elastic function does not, in fact, "work" the sheets; it only pulls the other one (that "works" the sheets by transmitting their tension to the winch) taut enough to avoid tangles at the drum. So where do the rules permit the separate "tautening" line, neither contiguous with the sheet control line, nor performing the function permitted? Ah, the beauty of the closed class rule.

I particularly like the part of the interpretation 2003-4 that admonishes us about the importance of distinguishing the sheets from the sheet control line (and from each other), without offering any interpretation or definition that would help a builder or measurer draw that distinction. And the presumption that the sheet control line must be singular, when the syntax of C.7.7(a) is, grammatically speaking, clearly ambiguous.

The fact is that lots of competitors seem to be straining mightily to find a way of improving the crappy sail coordination inherent in the traditional setup described above. Wouldn't it make sense, instead, to develop a consensus, and simply liberalize the rule to permit just about any arrangement of lines and geometry, so long as a single servo is used to operate both sails? Enough bondage and discipline.

Sidebar on topic: If you want a single sheet control line that tautens two sheets connected directly attached to drum or arm, think of a single length of elastic, at one end attached to the winch, and at the other connected to the middle of a "bar" pivot fitting whose ends are attached to the sheets by bowsies (sheet continuous through each one). That's a single control line, with a fitting. The sheets can play out with some measure of independence, due to the pivot, while each is kept taut. This would be simpler and more direct if an intervening line were used, but that would be two sheet control lines rearing their ugly heads. On the humorous side (this is not essential, perhaps even perverse, but someone might make use of it), the rule says that the sheet control line is attached to the sheet control unit, it doesn't say that it has to be attached to a _moving_ part of the unit!

[Chairman]

... in a plain-vanilla drum-winch installation that you can see at any sailing venue, there are actually two separate physical lengths of line, each connected the drum on one end, and to each other at a ring or other fitting where the sheets attach to the "circuit." The line that has the elastic function does not, in fact, "work" the sheets; it only pulls the other one (that "works" the sheets by transmitting their tension to the winch) taut enough to avoid tangles at the drum. So where do the rules permit the separate "tautening" line, neither contiguous with the sheet control line, nor performing the function permitted?

Hi Charles

Nicely put. Most of the sailors I've spoken to think that a "control line" can be made up of a number of parts -- length of cord, ring, piece of elastic, another length of cord, and so on. As long as all these bits tie together into one, er, "line", the thinking is that this must be fine. But perhaps this needs to be tested by a request for an interpretation.

Ah, the beauty of the closed class rule.

Tell me about it! But what are the alternatives, if one wants a "one-design" yet home-designed and home-built class that nevertheless offers some freedoms in hull and appendages?

I particularly like the part of the interpretation 2003-4 that admonishes us about the importance of distinguishing the sheets from the sheet control line (and from each other)

Worth drawing our attention to both interpretation 2003-IOM-3 and 2003-IOM-4, thanks. Personally, I wasn't offended by the admonition since the cap clearly fitted me .

And the presumption that the sheet control line must be singular, when the syntax of C.7.7(a) is, grammatically speaking, clearly ambiguous.

Possibly, but the interpretation is unambiguous -- only one control line.

The fact is that lots of competitors seem to be straining mightily to find a way of improving the crappy sail coordination inherent in the traditional setup described above. Wouldn't it make sense, instead, to develop a consensus

Yup, that's what IOMICA is here for, get your NCA to propose a rule change.

On the humorous side (this is not essential, perhaps even perverse, but someone might make use of it), the rule says that the sheet control line is attached to the sheet control unit, it doesn't say that it has to be attached to a _moving_ part of the unit!

Absolutely. In Soeren's diagram, take the elastic around two further turning blocks, one on the jib sheet side and the other on the main sheet side, and then attach the original turning block to the sheet control unit -- job done .

[Arvin S.]

Replying here to different posts at the same time, hope you guys don't mind

Arvin;s sketch # 4 shows a common loop system, which almost always has some elastic in the loop (although this sketch does not show the elastic element). So it is accepted that any elastic tensioning part of the sheeting system is acceptable.

Actually Sketch 4 and 5 were drawn with a "closed loop" system, which is the first and only system I know and have accepted for Sail winches. This is because my first IOM has this system and books I had showed this system. More importantly I don't trust elastics, probably because I have never tried them out, I fear that they might snap or break during an important part of a race, etc. So for me personally I have tried to steer clear away from elastics. Though Ralf is right the same diagram can also show an elastic anyway.

In a realistic installation in an IOM, each of the sheets shown in drawing 2 and drawing 3 need to be tensioned, presumably with an elastic line. The problem I see is that each elastic line is a "control line", and so you end up with two control lines per installation. I'm not sure two separate control lines are permitted.

Lester, and the rest. Forgive my ignorance, but please explain to me the reason for system 2 and 3 to ahve a tensioner like an elastic? I am serious I might not really be missing a key issue here. The reason is that my experience with RC sail control is mostly with Double arm servo which is System #3 which I said is mainly used for Soling One meters. (anyone out there also have a soling one meter to confirm?) And from my experience and from what I think I know this system does not need an elastic to tension the ends. I take it that the tensioner is necessary for light winds?

So if we assume that I chose to not use a tensioner for System #3? The double arm system can be acceptable with IOM class rules? Any unofficial comments? But would rather have an official ruling in the future

The fact is that lots of competitors seem to be straining mightily to find a way of improving the crappy sail coordination inherent in the traditional setup described above. Wouldn't it make sense, instead, to develop a consensus, and simply liberalize the rule to permit just about any arrangement of lines and geometry, so long as a single servo is used to operate both sails? Enough bondage and discipline

I totally agree. We all know that using a 3rd servo to Twitch the jib or improve slot is already illegal. It is illegal because of different rules such as only 2 channels, only 2 servos, etc. etc.

If possible we should at least simplify or liberalize the rules to permit known arrangements. As we know, it is difficult to figure out what was the main purpose of the specific rules about control lines, etc. Can we still contact the original rule makers? Then again it is unecessary coz as Lester said we do have the NCAs to decide by themselves already.

One thing to consider, as Ralf mentioned, the rules said "May" for control line. So may we assume also that the control line is an option? So that direct attachment to sail control arm or winch was the norm before?

Lester thanks for your comment about using GIF, i'll make sure i'll use it next time. Also thanks for unofficial info that System no. 5 is acceptable, it is just weird that i have not yes seen an IOM with this type of system. If No. 5 is okay, then Number 2 should also be okay (if we don't use elastic).

Lastly hey ralf what is this about using a Belt drive for sail control? Please elaborate

TTFN
Arvin

[Chairman]

In a realistic installation in an IOM, each of the sheets shown in drawing 2 and drawing 3 need to be tensioned

please explain to me the reason for system 2 and 3 to ahve a tensioner like an elastic? [...] from what I think I know this system does not need an elastic to tension the ends. [...] if we assume that I chose to not use a tensioner for System #3 The double arm system can be acceptable with IOM class rules?

Hi Arvin

If there is nothing attached to the arm but the sheets, and nothing attached to the sheets but the booms, then #2 and #3 are (IMHUO) fine.

The reason for elastic in a "realistic" installation is to keep the sheets from fouling or hooking up on the end of the arm or anywhere else, both light and heavy airs. But if you like living dangerously, no problem...

[cfwahl]

Lester wrote:

Ah, the beauty of the closed class rule.

Tell me about it! But what are the alternatives, if one wants a "one-design" yet home-designed and home-built class that nevertheless offers some freedoms in hull and appendages?

Well here's a radical idea, but consider it: the rules are pretty reliably restrictive as they stand. Would it be such a difference if the IOMICA decided that the class is henceforth an open, rather than a closed, class? On the face of it, I think very little of substance would change, respecting the goals of the class, and it would make administration and enforcement simpler, I should think.

[edmorales]

is it possible to just publish a set of arm winch set up illustrations or diagrams of what is allowed and not allowed, just to make it simpler
ed

[ralph kelley]

The simple solution to all this potential hassle is to simply state that only one sail control servo is allowed and delete all the rest about sheeting. Clearly this was the intent of the class rule developers when the class was started. The recent conversion to a format for our Rules that matches all International Classes (a format that is targeted to include all boats, from dinghy to large yachts) has just made things more difficult.

Ralph

[RoyL]

I agree with Ralph 100%. Simpler is better.