Upper and lower points

Discuss the IOM class rules and interpretations

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Don Case
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Joined: 16 Sep 2008, 05:09

Upper and lower points

Post by Don Case » 24 Oct 2008, 19:04

Just to double check, the 1600 mm measurement is taken from the bottom of the upper limit mark to the top of the lower limit mark, right?
Thanks
Don
Don Case
Can 271
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Bruce Andersen
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Post by Bruce Andersen » 24 Oct 2008, 19:30

that is correct

Don Case
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Post by Don Case » 24 Oct 2008, 19:31

Thanks Bruce
Don Case
Can 271
Vancouver Island B.C.

Barry Fox CAN262
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Design: V8
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Post by Barry Fox CAN262 » 25 Oct 2008, 03:59

This might seem to be to picky and you likely have it right but the bottom of upper band is actually the top of the mast tube itself. The other band you actually apply to the mast is the "middle band" although it is near the top.
Barry Fox
CAN 46
Vancouver Island, BC, Canada

Bruce Andersen
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Post by Bruce Andersen » 25 Oct 2008, 05:30

actually, you need an upper band - it can be at the top of the mast, but needs to be a contrasting stripe with its lower edge no more than 1600mm above the upper edge of the lower band. The lower edge of the middle band denotes the line above which a line extended up from the leading edge of the jib cannot go above.

Don Case
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Post by Don Case » 25 Oct 2008, 16:45

Can we talk about the middle band for a sec. C.8.4 c 1 (however you write that) says a line from the tack to the head point------- . Can the attachment point be above the middle band? Because of the boom offset the jibstay makes a slight bend at the upper swivel. This causes the jibstay to contact the mast above the C.8.4.c.1 line. I believe that I could put the attachment point on or slightly above the C.8.4.c.1 line and still be within the rules. I realize it wouldn't buy me much but I am curious.
Thanks
Don
Don Case
Can 271
Vancouver Island B.C.

Bruce Andersen
USA NCA Officer
Posts: 760
Joined: 25 Nov 2003, 00:06
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Club: Famous Potatoes Sailin Club
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Post by Bruce Andersen » 25 Oct 2008, 17:03

No. The line that describes the leading edge of the jib (and thus the forestay) cannot intersect the leading edge of the mast above the lower edge of the middle band. I can't imagine how you could attach the jibstay to the mast above the midband and still comply with this measurement rule. Most folks put the hole in the mast into which the jibstay attaches a few mm below the bottom of the middle band.

JThompson
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Post by JThompson » 30 Oct 2008, 13:44

I can describe it as my old rig was set up this way. The previous owner put a small pad eye attached to the mast just below the middle band. The head stay passed through the hole in the pad eye and then was attached a couple inches above the middle band. The line intersected the rig below the middle band, but the headstay way attached to the rig above the middle band.

Its only a practice rig so I dont know if it would be legal or not.

Regards,
Jim
Jim Thompson
IOM - USA 370 - Ericca

Bruce Andersen
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Post by Bruce Andersen » 03 Nov 2008, 20:51

Interesting question. I built a few rigs that way also, and is a nice way to make large forstay adjustments. From my (un-official) interpretation of the rule, it's legal, because the measurement is taken from the tack and head points of the sail, not including any rigging attachemnts.

(c) HEADSAIL
(1) A line taken through the tack point and the head point shall cut the
forward face of the mast spar lower than the lower edge of the
headsail stay limit mark at the fore side of the spar when the boom
spar is on the centreplane of the hull.

I suppose if the line goes up the spar, someone might make an argument that tensioning the line stiffens the upper portion of the spar and might be illegal. That's why I ran the line through an eye, then down the spar to terminate below the middle band.

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