Mast measurements

Discuss measuring an IOM and being a measurer

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PhilWatkins
Posts: 4
Joined: 08 Jan 2006, 20:09
Sail number: GBR2351
Club: Bournville, UK
Design: Widget
Location: GBR 2351

Mast measurements

Post by PhilWatkins » 28 Dec 2012, 00:33

Hi,

Been away for a while and am in the process of building a new mast and I have some questions regarding the measurements for a number 2 rig.

I have tried referencing Google but with no success so my questions are:
  • I am using the mast head fitting as the top limit band and am taking the measurements from the top of the mast; so I measure the fore stay limit @ 160mm and place a tape marker, should the mark be referenced to the top or the bottom of the tape marker or does it not matter?
    Same question for the bottom limit mark 8)
    How should the goose-neck/kicker be positioned in respect to the lower limit band?
    There is no measurement for the shroud attachment to the mast does that mean it's a free location between the limit bands, what would be the suggested distance for the three rig sizes?
Many thanks in advance.

Phil Watkins
GBR2351
Phil Watkins

Hiljoball
Posts: 266
Joined: 06 Jan 2006, 01:47
Sail number: CAN 307
Design: V8
Location: CAN

Re: Mast measurements

Post by Hiljoball » 28 Dec 2012, 02:19

The measure is to the bottom of the upper bands, and to the top of the lower band.

There is no specific measurement for the placement of the gooseneck. The issue is that the main tack cannot come below the top of the lower band. So it would not make sense to mount the gooseneck above the band as you would not be able to tighten the main luff.

Shroud height is like religion - some place them high, others go low. High holds the mast straighter, lower lets the top bend off in gusts. Some say it depends on the stiffness of the boat and the mast tube. A recent ruling allows a choker sliding adjuster on the shrouds to vary the effective shroud height.

Same with spreader length - longer pushes the centre of the mast to leeward and pulls the top to weather - shorter spreader reduces the effect. See Lester Gilbert's site.
http://www.onemetre.net/

I like the TS2 building guides. They give dimensions for low shrouds set up (which is my religion)

http://rcyachts.net/TS2/Guides%20for%20TS-2.pdf

John
John Ball
CRYA #895
IOM CAN 307 V8

PhilWatkins
Posts: 4
Joined: 08 Jan 2006, 20:09
Sail number: GBR2351
Club: Bournville, UK
Design: Widget
Location: GBR 2351

Re: Mast measurements

Post by PhilWatkins » 28 Dec 2012, 20:07

John,

Thanks for the swift reply, should have thought of the main tack <doh!>

I'll check on Lester site re shrouds.

Thanks again and a Happy New Year

Phil
Phil Watkins

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