SLIT SEAMS Part B2 IOM Class Rule Change Proposals.
Posted: 10 Aug 2005, 15:16
COMMENTS ON PART B2 of 2005 IOM class RULE CHANGE PROPOSALS.
2 August 2005
I have no objection to the concept of shaping sails by the use of "slits". I can however see a number of issues resulting from these new rules as they presently stand.
1. Is there a maximum number of "slits" permitted?
2. Is the length of the "slits" regulated?
3. I assume the "slits" will be reinforced by a "cover" or "reinforcement" strip. Is this strip regulated by the existing rule for flutter patches or
would reinforcement within the seam width (15mm) be permitted?
In summary my first impression is that this rule, as it stands, would allow
one to make a sail with any number of seams (ie panels) with the only
restriction being that the luff should be continuous.
Far from this resulting in an easy way of making a "home made" sail, it
could result in complicated sails of many panels.
I think there should be a limit on the number and size of "slits" that can
be used on a single part sail. I suggest three slits on a main and two slits
on a headsail, no longer than (??) mm.
An alternative suggestion might be to change the wording of G.3.1(a)(2) and (3) to:
(2) The body of the sail shall consist of the same ply throughout comprising not more than four parts and not more than three seams.
(3) Seams and/or their extension shall not deviate more than 10mm from a straight line between luff and leech.
The definition of a seam does include a seam closing a "slit". A mainsail could therefore be of one part but with up to three "slit" type seams. Since the "slits" would be effectively replacing the more conventional overlap seams (and defined as seams) there would be no reason to limit their length or even define a "slit" type seam.
A "slit" seam will probably require reinforcement. This could be achieved by adding (if necessary) the item under secondary reinforcement and a modification to the Seam width item:
Secondary Reinforcement:
from nearest sail corner measurement point……………….125 mm
for flutter patches………………………………………………………….. 50 mm
at luff fittings, luff slides and/or luff openings………………. 20 mm
At a seam
Tabling width………………………………………………………………………..........……15 mm
Seam width including seam secondary reinforcement………………….. 15 mm
The Headsail rules would also be modified in a similar way.
The only effect these rule modifications would have on the existing sails is to allow a "standard" overlap seam to be reinforced. This would seem to be appropriate to retain parity between the overlap and slit methods of making seams.
In this way there is no need to define or even mention a "slit" seam, a term which is not covered in the ERS.
There could be an interpretation confirming that a slit seam is a seam if it was felt that it was necessary.
What do you think?
In the end it may not be worth the trouble!
Robert Hales
Technical Officer
Australian Radio Yachting Association Inc.
2 August 2005
I have no objection to the concept of shaping sails by the use of "slits". I can however see a number of issues resulting from these new rules as they presently stand.
1. Is there a maximum number of "slits" permitted?
2. Is the length of the "slits" regulated?
3. I assume the "slits" will be reinforced by a "cover" or "reinforcement" strip. Is this strip regulated by the existing rule for flutter patches or
would reinforcement within the seam width (15mm) be permitted?
In summary my first impression is that this rule, as it stands, would allow
one to make a sail with any number of seams (ie panels) with the only
restriction being that the luff should be continuous.
Far from this resulting in an easy way of making a "home made" sail, it
could result in complicated sails of many panels.
I think there should be a limit on the number and size of "slits" that can
be used on a single part sail. I suggest three slits on a main and two slits
on a headsail, no longer than (??) mm.
An alternative suggestion might be to change the wording of G.3.1(a)(2) and (3) to:
(2) The body of the sail shall consist of the same ply throughout comprising not more than four parts and not more than three seams.
(3) Seams and/or their extension shall not deviate more than 10mm from a straight line between luff and leech.
The definition of a seam does include a seam closing a "slit". A mainsail could therefore be of one part but with up to three "slit" type seams. Since the "slits" would be effectively replacing the more conventional overlap seams (and defined as seams) there would be no reason to limit their length or even define a "slit" type seam.
A "slit" seam will probably require reinforcement. This could be achieved by adding (if necessary) the item under secondary reinforcement and a modification to the Seam width item:
Secondary Reinforcement:
from nearest sail corner measurement point……………….125 mm
for flutter patches………………………………………………………….. 50 mm
at luff fittings, luff slides and/or luff openings………………. 20 mm
At a seam
Tabling width………………………………………………………………………..........……15 mm
Seam width including seam secondary reinforcement………………….. 15 mm
The Headsail rules would also be modified in a similar way.
The only effect these rule modifications would have on the existing sails is to allow a "standard" overlap seam to be reinforced. This would seem to be appropriate to retain parity between the overlap and slit methods of making seams.
In this way there is no need to define or even mention a "slit" seam, a term which is not covered in the ERS.
There could be an interpretation confirming that a slit seam is a seam if it was felt that it was necessary.
What do you think?
In the end it may not be worth the trouble!
Robert Hales
Technical Officer
Australian Radio Yachting Association Inc.