What "..shall pass through a 20mm, ring gauge." BOOM F.4.5

Discuss the IOM class rules and interpretations

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James Chrismas
Posts: 32
Joined: 16 Feb 2010, 17:36
Sail number: GBR2612
Club: Swear Deep Sailors
Design: Triple Crown

What "..shall pass through a 20mm, ring gauge." BOOM F.4.5

Post by James Chrismas » 07 Nov 2014, 14:43

Hi Guys,
I wish to use a kicker lever on my boat and to that end have designed a fitting as follows:

[img]
Kicker---Fittings-11mm.jpg
Kicker---Fittings-11mm.jpg (6.78 KiB) Viewed 13344 times
[/img]


“A” and “B” are straps that can slide along the boom such that the kicker fitting can be easily removed. (As there is space I have incorporated the mainsheet adjustment line.)

Our Class Rules 2014-2016 Rule F.4
F.4.3 MAINSAIL BOOM FITTINGS
(a) MANDATORY
(1) Mainsail clew fitting(s).
(2) Mainsail boom sheet fitting(s).
(3) Kicking strap fitting.
and
BOOM F.4.5 DIMENSIONS states:
Spar, ignoring features permitted by F.4.2, between
points 10 mm from each end:
the boom spar shall pass through a 20 mm, ring
gauge
The ISAF Equipment Rules (ERS) define a spar as:
F.1.3 Spar
The main structural part(s) of the rig, to, or from which sails are attached
and/or supported.
and
F.1.4 (b) BOOM
A spar attached at one end to a mast spar or a hull and on which the clew
of a sail is set and on which the tack and/or foot of the sail may be set.
Includes its rigging, fittings and any corrector weights, but not running
rigging, running rigging blocks and/or any kicking strap/strut
arrangement.
Question: Is this arrangement required to fit through the “…20mm, ring gauge.”

Thanks very much,
James Chrismas
GBR 2612

James Chrismas
Posts: 32
Joined: 16 Feb 2010, 17:36
Sail number: GBR2612
Club: Swear Deep Sailors
Design: Triple Crown

Re: What "..shall pass through a 20mm, ring gauge." BOOM F.

Post by James Chrismas » 08 Nov 2014, 08:41

Further to my opening post. I believe that the kicker and its fittings do not constitute part of the boom and are therefore not required to pass through the 20mm ring gauge.
James Chrismas
GBR 2612

Barry Chisam
Posts: 33
Joined: 20 May 2004, 22:10

Re: What "..shall pass through a 20mm, ring gauge." BOOM F.

Post by Barry Chisam » 09 Nov 2014, 15:23

Seems to me all you need to know is in your original post.
The boom consists of the spar together with all its fittings, rigging and corrector weights.
The spar, the peice that has to fit through the 20mm hole is the main structure that supports the sail which would exclude all the fittings and rigging.

James Chrismas
Posts: 32
Joined: 16 Feb 2010, 17:36
Sail number: GBR2612
Club: Swear Deep Sailors
Design: Triple Crown

Re: What "..shall pass through a 20mm, ring gauge." BOOM F.

Post by James Chrismas » 09 Nov 2014, 17:11

Thanks Barry. I'm glad I'm not the only one who thinks this way.

I would still like to hear what Barry Fox or Robert Grubisa have to say as I have had my interpretation queried locally.
James Chrismas
GBR 2612

James Chrismas
Posts: 32
Joined: 16 Feb 2010, 17:36
Sail number: GBR2612
Club: Swear Deep Sailors
Design: Triple Crown

Re: What "..shall pass through a 20mm, ring gauge." BOOM F.

Post by James Chrismas » 11 Nov 2014, 10:27

Further to the above:

I would like to take this design one stage further and incorporate a screw and rod link to the mainsail clew fitting. The kicker/panel can be removed in exactly the same way as before. Once removed the boom with its fittings would easily fit through a 20mm ring gauge. See attached drawing.

Is there any reason that this arrangement would fall outside of the class rules?
Attachments
Booms---Fittings-11mm.jpg
Booms---Fittings-11mm.jpg (7.04 KiB) Viewed 13240 times
James Chrismas
GBR 2612

Dick Carver
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Location: USA 22

Re: What "..shall pass through a 20mm, ring gauge." BOOM F.

Post by Dick Carver » 11 Nov 2014, 19:38

Hi James.
Is there any reason that this arrangement would fall outside of the class rules?
Maybe... does any of it work in compression ?
Dick Carver

James Chrismas
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Sail number: GBR2612
Club: Swear Deep Sailors
Design: Triple Crown

Re: What "..shall pass through a 20mm, ring gauge." BOOM F.

Post by James Chrismas » 11 Nov 2014, 20:28

Hi Dick,

The kicker and all control lines/running rigging are in tension as is the connection from the clew to the clew fitting. The control line panel is under both tension and compression and the link from the clew fitting to the adjustment screw on the control panel is in compression.

My understanding of the rules is that the kicker, fixed and running rigging shall operate in tension, which they do.

I don't think I'm missing anything...
James Chrismas
GBR 2612

James Chrismas
Posts: 32
Joined: 16 Feb 2010, 17:36
Sail number: GBR2612
Club: Swear Deep Sailors
Design: Triple Crown

Re: What "..shall pass through a 20mm, ring gauge." BOOM F.

Post by James Chrismas » 11 Nov 2014, 20:36

P.S.
C.8 SAILS
C.8.4 USE
(b) MAINSAIL
(1) The tack point shall not be set more than 25 mm forward of the forward end of the boom spar and the clew point shall not be set more than 25 mm aft of the aft end of the boom spar.
By definition both the fitting at the tack and the fitting at the clew must be under compression so I don't see any problem with the clew adjustment fitting being under compression - it would have to be for the clew point to be beyond the end of the boom.
James Chrismas
GBR 2612

James Chrismas
Posts: 32
Joined: 16 Feb 2010, 17:36
Sail number: GBR2612
Club: Swear Deep Sailors
Design: Triple Crown

Re: What "..shall pass through a 20mm, ring gauge." BOOM F.

Post by James Chrismas » 12 Nov 2014, 12:15

P.P.S.

The compression element of this kicker arrangement is entirely contained within the fitting. The only link to the mast is via the gooseneck fitting and that operates - upper in compression, lower in tension. This is true of all kicking strap arrangements that are combined with the gooseneck fitting. The undefined kicking strap fittings on the boom all operate in tension. In terms of the "kicking strap/strut arrangement" as a whole, it can only operate in tension.

I could remove the internal compression element by adding a line from the outer end of the kicker fitting to the end of the boom and take the kicker control lines via the mast or gooseneck to the panel. I could also modify the clew fitting so that the action is pull rather than push, but I question the necessity of doing that as I have already pointed out the fact that class rule C.8.4 (b)(1) permits the fitting to be in compression.
James Chrismas
GBR 2612

Barry Chisam
Posts: 33
Joined: 20 May 2004, 22:10

Re: What "..shall pass through a 20mm, ring gauge." BOOM F.

Post by Barry Chisam » 13 Nov 2014, 16:46

First question, is what you call a control line panel a permitted fitting???
If it constitutes part of the kicker then it must work only in tension which it appears not to.
It cannot be considered part of the boom as the boom must be a constant section and fit through our 20mm hole.
If you fitted a wire or similar to transfer the loading to the boom end to take away the compression loading would the wire (standing rigging ??) be a permitted fitting or be part of the kicker.

James Chrismas
Posts: 32
Joined: 16 Feb 2010, 17:36
Sail number: GBR2612
Club: Swear Deep Sailors
Design: Triple Crown

Re: What "..shall pass through a 20mm, ring gauge." BOOM F.

Post by James Chrismas » 14 Nov 2014, 10:26

Hi Barry,

Many thanks for your continued interest. It definitely helps focus my mind.
It is an integral part of the kicker and is a convenient place to lead its adjustment/control line. It has always been that way and I have called it a control line panel to differentiate it from the kicker lever or any other part of the kicker fitting. Nothing more sinister than that. The subsequent combining of the kicker with the termination of the main sheet allows me to introduce multiple purchase to the main sheet to give finer control - something I'm trying to introduce wherever possible. Combining fittings is permitted:
FF.2.4 CONSTRUCTION
(a) Fittings and/or control lines may be combined provided their function is not extended beyond what is permitted.
(b) The position of parts, and the length and tension of rigging, may be adjustable unless otherwise restricted.
I'm glad that you concur that it is not part of the boom. This post was started because one of the group I sail with reckoned it was required to fit through the 20mm ring gauge.

Since my last post I have been thinking about the wire to the end of the boom, which in my opinion would be part of the kicker just as the wires between the panel the lever and the gooseneck fitting are part of the kicker. I don't like it as it is untidy and would reintroduce different metals in touch with each other in a marine environment and those corrosion problems. I have now come up with an altogether neater idea. A simple lug/tongue/what ever you want to call it could be incorporated into the panel design such that it would stick upwards from the outer end of the kicker panel into a hole in the boom. More holes, which I didn't want, but problem solved.

Corrosion problems on my old mast set me thinking about how to remove as many causes of corrosion as possible. See viewtopic.php?f=7&t=1822.

Thanks again,
James
James Chrismas
GBR 2612

Barry Chisam
Posts: 33
Joined: 20 May 2004, 22:10

Re: What "..shall pass through a 20mm, ring gauge." BOOM F.

Post by Barry Chisam » 15 Nov 2014, 20:06

Hi James, I made an error in the wording of my preveous post.
Your fitting, whatever you call it is part of the boom but not the boom spar, and it is the spar that has to fit in the 20mm.
I do think you may have trouble with regard to permitted fittings.

F.4.3 MAINSAIL BOOM FITTINGS
(a) MANDATORY
(1) Mainsail clew fitting(s).
(2) Mainsail boom sheet fitting(s).
(3) Kicking strap fitting.
(b) OPTIONAL
(1) Mainsail tack fitting(s).
(2) Gooseneck fitting.
(3) Opening(s) for mainsail boom sheet fitting.

Also.

F.2.3 LIMITATIONS
The function of items shall be limited to what is normally provided by items of their type.

James Chrismas
Posts: 32
Joined: 16 Feb 2010, 17:36
Sail number: GBR2612
Club: Swear Deep Sailors
Design: Triple Crown

Re: What "..shall pass through a 20mm, ring gauge." BOOM F.

Post by James Chrismas » 15 Nov 2014, 21:21

Hi Barry,

Thanks for your continued interest.

As far as I can see my design fulfils all the requirements of
F.4.3 MAINSAIL BOOM FITTINGS
(a) MANDATORY
(1) Mainsail clew fitting(s).
(2) Mainsail boom sheet fitting(s).
(3) Kicking strap fitting.
(b) OPTIONAL
(1) Mainsail tack fitting(s).
(2) Gooseneck fitting.
and
F.2.3 LIMITATIONS
The function of items shall be limited to what is normally provided by items of their type.
and
F.2.4 CONSTRUCTION
(a) Fittings and/or control lines may be combined provided their function is not extended beyond what is permitted.
(b) The position of parts, and the length and tension of rigging, may be adjustable unless otherwise restricted.
(c) Ball and/or roller bearings may be used for: kicking strap fitting; gooseneck; mainsail boom sheet blocks; headsail boom sheet blocks;
and
C.8 SAILS
C.8.4 USE
(b) MAINSAIL
(1) The tack point shall not be set more than 25 mm forward of the forward end of the boom spar and the clew point shall not be set more than 25 mm aft of the aft end of the boom spar.
As I see it I have all the "MANDATORY" fittings, I have not extended their "...function...". Yes I have "...combined fittings..." but "...their function is not extended beyond what is permitted." The clew fitting must be able to operate under compression as it is permitted to be up to "...25mm aft of the aft end of the boom spar." The independent adjustment of any fitting has absolutely no effect on any other - and you have agreed that they don't need to fit through a 20mm ring gauge. I can therefore see no grounds for opposing my design.

I am genuinely interested in learning if I have got this wrong.

Thanks again

James
James Chrismas
GBR 2612

Hiljoball
Posts: 270
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Design: V8
Location: CAN

Re: What "..shall pass through a 20mm, ring gauge." BOOM F.

Post by Hiljoball » 15 Nov 2014, 22:36

I think the issue is the structure to which these fitting attach. I would call it a sub-assembly. As such is probably falls outside the rules.

You should be able to eliminate it by attaching the fittings directly to and/or inside the boom.

John
John Ball
CRYA #895
IOM CAN 307 V8
In my private capacity

James Chrismas
Posts: 32
Joined: 16 Feb 2010, 17:36
Sail number: GBR2612
Club: Swear Deep Sailors
Design: Triple Crown

Re: What "..shall pass through a 20mm, ring gauge." BOOM F.

Post by James Chrismas » 16 Nov 2014, 12:30

Hi John,

Many thanks for your response to this post.

What you are calling "...a sub-assembly." is no more "...a sub-assembly." than the panel linking a gooseneck fitting to a kicking strap fitting. Control lines can be terminated on that "...sub-assembly." and it could then be described as a "control panel". Does any of that mean it is prohibited under the class rules?

Incidentally, the common panels one sees linking the kicker to the gooseneck have the additional function of stiffening the mast, but are permitted. My panel, which you are describing as "...a sub-assembly.", doesn't contribute to the stiffness of the boom as it is loose fitted.

Thanks again.

All the best,

James
James Chrismas
GBR 2612

Hiljoball
Posts: 270
Joined: 06 Jan 2006, 00:47
Sail number: CAN 307
Design: V8
Location: CAN

Re: What "..shall pass through a 20mm, ring gauge." BOOM F.

Post by Hiljoball » 16 Nov 2014, 20:50

HI James,

Where in the rules does it specifically allow "the panel linking a gooseneck fitting to a kicking strap fitting"?

You want to keep arguing that what you propose is legal - but this is not the place to do that. The class rule is 'closed', so anything not specifically permitted, is prohibited.

So if you want to do something 'slightly different or new', then you have to start with the assumption that it is not class legal. Then go to your local measurer who it turn will contact your NCA (the MYA in your case) and ask for an opinion. If they are not sure, then on your behalf, they will submit a question to the IOMICA Technical Committee for a finding.

John
John Ball
CRYA #895
IOM CAN 307 V8
In my private capacity

James Chrismas
Posts: 32
Joined: 16 Feb 2010, 17:36
Sail number: GBR2612
Club: Swear Deep Sailors
Design: Triple Crown

Re: What "..shall pass through a 20mm, ring gauge." BOOM F.

Post by James Chrismas » 16 Nov 2014, 23:38

Hi John,

I would like to start by making it quite clear that I have already asked our NCA and Robert Grubisa as moderator to take a look at this post and let me know his/their thoughts. Last time I had a query viewtopic.php?f=7&t=1535 Robert Grubisa kindly stepped in on my behalf and although my design was different it was permitted http://www.iomclass.org/doc-files/Techn ... -IOM-2.pdf.
Where in the rules does it specifically allow "the panel linking a gooseneck fitting to a kicking strap fitting"?
Good question, but you look at the vast majority of those fittings that are in common use and they are joined either by an aluminium panel/fitting/what ever you wish to call it or one made of carbon fibre. On a "big" boat, the gooseneck and kicker are attached to the mast quite separately, which could be done on an IOM, but I haven't seen it.

I repeat - I am not introducing any fittings that aren't permitted and there is no restriction on the design of those fittings subject to the rules below.
D.2.3 FITTINGS
Fittings are unrestricted except that:
(a) Fittings that can contribute to the stiffness and/or strength and/or watertight integrity of the hull shall be of materials permitted by D.2.1.
(b) Ball and/or roller bearings may only be used for: sheet control line blocks, mainsail boom sheet blocks and headsail boom sheet blocks.
(c) Fittings shall not project outboard of the hull shell or deck.
F.2.3 LIMITATIONS
The function of items shall be limited to what is normally provided by items of their type.

F.2.4 CONSTRUCTION
(a) Fittings and/or control lines may be combined provided their function is not extended beyond what is permitted.
These are the same rules that permit the gooseneck fitting to be combined with the kicker fitting and/or the downhaul fitting and the myriad variations of the design of these fittings including designs that enable adjustment of the angle of the gooseneck/kicker in relation to the mast so that leech tension can be automatically adjusted as the sails are let out and that adjustment to be varied for different conditions. One has only to look at Interpretation 2012- IOM – 1
http://www.iomclass.org/doc-files/Techn ... -IOM-1.pdf to see a whole variety of designs and combinations that are permitted.

I hope this clarifies my position and answers your question.

All the best,
James
James Chrismas
GBR 2612

David L Alston
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Re: What "..shall pass through a 20mm, ring gauge." BOOM F.

Post by David L Alston » 19 Nov 2014, 01:20

Forgive me, if you know all this what is your question.

Innovation is a good thing but I see nothing particularly innovative in what you propose.

The kick strap adjustment is super critical - 1/4 turn is a bout 0.3 mm on my adjuster and a quarter turn is the difference between going well or plonking about.

But I must return to what is for me the burning question ...What is your question ... we all know the rules and have seen the interpretation given to the Kick Strap - a strap in tension only - two points of attachment only- Boom and where ever you like below the Boom.

What else is there to debate here

When do we see you racing with this arrangement

Dave

James Chrismas
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Re: What "..shall pass through a 20mm, ring gauge." BOOM F.

Post by James Chrismas » 19 Nov 2014, 15:28

Thanks for your interest Dave.

Whilst I am convinced in my mind that there is no problem, others don't agree. What started out merely as a query, regarding what had to go through the 20mm ring gauge, has developed in various directions principally as to whether I am extending the function of anything. My local measurer has now referred this to the technical team for a decision. I will post the outcome as soon as I have their decision together with a picture of my design in action if it is OK'd.

Thanks for your continued interest.

James
James Chrismas
GBR 2612

Barry Fox CAN262
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Re: What "..shall pass through a 20mm, ring gauge." BOOM F.

Post by Barry Fox CAN262 » 26 Nov 2014, 00:56

An interesting design exercise and Robert is certainly the right guy to address it in the end. As John Ball has told you below, and you indicate you are doing, the only official declaration comes from asking for an interpretation. Seems like you have started on that path.

Personally, I would question the intent of the structure that constitute the panel to carry all this. I would say that it easily can (meant to or not) contravene the intent of the 20 mm ring rule which, from my understanding, is meant to limit the structure below the actual sail so that it doesn't/can't represent increased area facing the wind and potentially provide a performance increase.

If the pivot points (fittings) that support all the pieces of this mechanism were limited to the extent that they provide only that function (mounting points) then the next question that would need to be confirmed is if the kicking strap/vang is capable of being operated in compression. Even if you don't intend to use it in compression it should not be able to be adjusted to the extent that it could operate in compression. ERS (which is always used for definitions) uses the phrase "capable of working in tension only" to describe how things are attached and how they can function.

Similar lever action systems have been used but if there is even a remote chance they can actually lift the boom (intentionally or not) then they are out.

So I don't like the size of your bracket/panel but the linkage system could be OK if it cannot, under any condition, lift the boom.

My opinion, not the official position.
Barry Fox
CAN 46
Vancouver Island, BC, Canada

James Chrismas
Posts: 32
Joined: 16 Feb 2010, 17:36
Sail number: GBR2612
Club: Swear Deep Sailors
Design: Triple Crown

Re: What "..shall pass through a 20mm, ring gauge." BOOM F.

Post by James Chrismas » 26 Nov 2014, 10:49

Thank you very much for your input Barry.

The intent of the structure is to put screw adjustment on as many controls as possible as I want the precise, fine and repeatable adjustment this gives. The kicker lever gives 7.5:1 ratio doubled with a 2:1 control line giving 15:1. I have no desire to extend the panel beyond the natural line of the kicker as this is unnecessary weight. Also, if extended to the end of the boom, the structure would dig into the water earlier on reaches and runs - something I definitely don't want.

It is not possible for the kicking strap to act in compression. I intend to use 0.8mm wire for the linkage. The gooseneck fitting is designed such that it can rotate in any direction except bellow horizontal. There have been several decisions that clearly permit this:
Interpretation 2012- IOM – 1
IOM Class Rule F.2.4(b) permits fittings to be adjusted and there are no restrictions as to the directions.
The depth of the structure - 15mm - is designed such that my fingers can comfortably reach the adjustment screw and cleats. (the adjustment screw should be half way up the structure, not as shown - my error). My other error is that the aft strap would be loose both on the boom and structure so that the structure can be dropped clear of the boom in order to give better access to the slot in the boom. I may also put a screw adjustment on the mainsail jackstay, 'though I haven't yet decided on the best way to do so.

I am constantly looking for improvements in the design.
The drawing I have submitted to the technical committee via my area measurer is bellow. In the accompanying information I have said that I would like to be able to extend the clew fitting forward inside the boom and link it to the screw adjustment with a pin.

Thanks again for your input.
James
Attachments
Gooseneck_Kicker_Outhaul_Mainsheet-Fittings-11mm.jpg
Gooseneck_Kicker_Outhaul_Mainsheet-Fittings-11mm.jpg (38.45 KiB) Viewed 12811 times
James Chrismas
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Robert Grubisa
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Re: What "..shall pass through a 20mm, ring gauge." BOOM F.

Post by Robert Grubisa » 11 Jan 2015, 16:46

Note that GBR NCA asked for interpretation on the IOM Class Rules regading fitting under the main boom.
See: http://www.iomclass.org/wp-content/uplo ... n-boom.pdf
Robert Grubisa

James Chrismas
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Club: Swear Deep Sailors
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Re: What "..shall pass through a 20mm, ring gauge." BOOM F.

Post by James Chrismas » 17 Jan 2015, 14:17

I look forward to your decisions with interest.

Thanks.

James
James Chrismas
GBR 2612

Robert Grubisa
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Re: What "..shall pass through a 20mm, ring gauge." BOOM F.

Post by Robert Grubisa » 11 Mar 2015, 14:58

Please be informed that the Interpretation 2015-IOM-1 has been published on Technical part of the IOM ICA website.

Best regards
Robert Grubisa

James Chrismas
Posts: 32
Joined: 16 Feb 2010, 17:36
Sail number: GBR2612
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Re: What "..shall pass through a 20mm, ring gauge." BOOM F.

Post by James Chrismas » 12 Mar 2015, 09:24

James Chrismas
GBR 2612

James Chrismas
Posts: 32
Joined: 16 Feb 2010, 17:36
Sail number: GBR2612
Club: Swear Deep Sailors
Design: Triple Crown

Re: What "..shall pass through a 20mm, ring gauge." BOOM F.

Post by James Chrismas » 12 Mar 2015, 10:30

I ran out of time to edit the above so here is the edited version:

Dear Robert,

Many thanks for your and your team's time and help.

I have to admit I am surprised by your ruling on the combined gooseneck/kicker/Cunningham/jackstay fitting:
C.8.4 USE
(b) MAINSAIL
(1) The tack point shall not be set more than 25 mm forward of the forward end of
the boom spar and the clew point shall not be set more than 25 mm aft of the
aft end of the boom spar.
Firstly, the gooseneck element of the fitting - the roller bearing provides horizontal rotation of the gooseneck and the vertical link between the gooseneck and kicker elements of the combined fitting provide vertical rotation of the gooseneck and kicker. The tack point of the mainsail is 17mm forward of the forward end of the boom so the combined fitting does not compromise this rule.
Secondly, all combined gooseneck and kicker fittings that I have seen have some form of solid connection between them. The solid link between the roller bearing of the gooseneck and the roller bearing of the kicker in my fitting is provided by extending the vertical element of the gooseneck to the kicker bearing in the same way as in these fittings:

http://www.radiosailingshop.com.au/inde ... cts_id=686

http://www.ullmansails.co.uk/store/prod ... roduct=188

http://www.onemetre.net/Reports/RankEas ... East06.htm

http://www.isobaryachts.com/hardware/7DPgooseneck.htm

http://stores.rcsailboatparts.com/carbo ... -mm-masts/

There are other examples around....

If I were to cut way all the non essential parts of this fitting as for example in the Ullmansails fitting - would it be permitted?

All the very best,

James
James Chrismas
GBR 2612

David L Alston
Posts: 72
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Re: What "..shall pass through a 20mm, ring gauge." BOOM F.

Post by David L Alston » 14 Mar 2015, 02:30

I see you are still having fun with this.

Perhaps you are not aware that these Class Rule interpretations are not coming from IOMIC or IOMUK or what ever it is. They originate from the IRSA Technical committee, the Radio Sailing arm of ISAF.

So do shoot the messengers ! - they were only working for you.

But still one has to ask:-

What advantage is there in your overtly complex if not novel design - And - When will we see a prototype sailing


If you are so certain/ convinced that the design complies with the Class Rule why not simply make it.

Like thousand of IOM enthusiasts over the world I look forward to seeing this in the flesh

Regards
Dave

David L Alston
Posts: 72
Joined: 24 Jul 2012, 17:38
Sail number: 3011
Club: Leicestershire RYC UK
Design: Fatboy

Re: What "..shall pass through a 20mm, ring gauge." BOOM F.

Post by David L Alston » 14 Mar 2015, 11:54

Following on from above. Reference the messengers:-

Perhaps you did not read the justification in ruling against your design.

Fundamentally it seems that they deem the plate/ fitting as adding strength / reinforcing the boom.

It matters not if this offers any or no advantage , simply put - structurally it does and this cannot be disputed. This is why the Class Rules are clear that the mast and boom SHAL be of uniform section throughout.

And secondly that fittings SHALL not provide stiffening to the spar hull etc.

The examples of commercially available Kickstraps you so kindly posted above do not provide any reinforcement of the boom. Yes - in the localised area of the mast attachment they do indeed add some degree of reinforcement but the key is that it is localised and the reinforcement does not EXTEND BEYOUND the useful/intended function/attachment of the fitting.





It is my belief that a second and probably more important point was actually missed in this ruling :- The Kickstrap itself -

The Kickstrap in you design effectively has three connection / termination points to the boat / fittings etc. And....

If you are absolutely intent upon using an over-centre leaver arrangement there are better ways of achieving this and whilst remain Class Compliant. I attach a sketch.

But it is an annoying arrangement - how do I know -

I sailed with it for half a season years ago while I was saving up for a nice shiny one that worked



Anyway - whilst you are in the IOM Site , read the other interpretations on Kickstrap, about four up from yours . Graham requested a ruling/ interpretation on virtually every conceivable arrangement ..



Regards
Dave
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Kick.pdf
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James Chrismas
Posts: 32
Joined: 16 Feb 2010, 17:36
Sail number: GBR2612
Club: Swear Deep Sailors
Design: Triple Crown

Re: What "..shall pass through a 20mm, ring gauge." BOOM F.

Post by James Chrismas » 16 Mar 2015, 09:53

Dear David,

Thank you for your comments. I have put together and submitted a detailed response to the Technical Committee of the IRSA's interpretation, which I shall not go into hear at the moment.
It matters not if this offers any or no advantage , simply put - structurally it does and this cannot be disputed.
I happen to disagree with you on this point. How can a fitting hanging freely below the boom
stiffen the boom in a selective way.
- their actual words. If you take a look at this boom http://sailsetc.com/magento/index.php/p ... -1176.html The G section of this boom must be stiffer than a simple round section and all those slides must
stiffen the boom in a selective way.
On top of this the
difference between the smallest and largest value along the spar of any external dimension
maximum of .5mm is exceeded - Rule F.4.5 DIMENSIONS. Also it could be argued that the G section automatically breaches the wall thickness requirement. I've had a look at your drawing, which as you say is very simple. I'm guessing that the adjustment is done by a slide on the boom? If so, this slide gives localised stiffening.... :)
What is good for the goose is good for the gander.

Regarding Graham's request, I referred to it in my post on 16 Nov 2014.

My intent all along has been to get as many adjustments as possible on screw fittings as I find them easier to use and more precise. As I have health problems I often have to ask someone on the pontoon to make adjustments and it is easier to say one turn on... than ask them to adjust a fiddly bowsy on a multiple purchase.

Below is a picture of the prototype that my local group are allowing me to use until the final decision of the Technical Committee. It is in need of extensive modification as I have learnt a lot from the trials. For one thing the final version will not have the kicker on a lever but a screw. We live and learn...

All the very best... and happy sailing!
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IMGP1018-small.jpg
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James Chrismas
GBR 2612

David L Alston
Posts: 72
Joined: 24 Jul 2012, 17:38
Sail number: 3011
Club: Leicestershire RYC UK
Design: Fatboy

Re: What "..shall pass through a 20mm, ring gauge." BOOM F.

Post by David L Alston » 18 Mar 2015, 01:04

Sorry like it or not

Have a look at the force diagram attached ...It is late so I may have made a mistake hear and there.

But
The actual kick strap pull down and an angle.
These forces resolve into two components:- Vertical ( Down) Fa(y) and Horizontal ( towards the mast ) Fa(x)

This X component places compression stress on the Plate and not on the boom - this compressive stress is now isolated and therefore not taken up by the boom.


Next

The Fa(y) is transferred to the boom at a point beyond the Kickstrap attachment point. by the ratio of L1/L2 and pulls down on the boom so the bending moment at the fitting attachment point is less than the bending moment that would have been imposed if the bracket were not actually there

So the Adjudication from IRSA was actually valid - they might not have actually calculated it but notwithstand how they might have arrived at the decision, the adjudication and justification was correct.


However if the plate was the length of the boom, the ruling would have been that the fitting was a part of the boom and would similar be ruled as noncompliant since it is fabricated from noncompliant materials.
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Force.pdf
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