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How to measure a jib boom?

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If a spar plan says 35' outside the cap for the jibboom, is that measured horizontally or parallel to the centerline of the boom? I'm assuming it's parallel, but the distance to the cap was 28' from the FP, which is horizontal, so I thought I'd just check.

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Hi rtwpsom2;


All masts and yards were measured parallel to their centreline.  They were made on land,  and the craftsmen making them needed to know how long to make them.


All the best,


Mark P


Previously built models (long ago, aged 18-25ish) POB construction. 32 gun frigate, scratch-built sailing model, Underhill plans.

2 masted topsail schooner, Underhill plans.


Started at around that time, but unfinished: 74 gun ship 'Bellona' NMM plans. POB 


On the drawing board: POF model of Royal Caroline 1749, part-planked with interior details. My own plans, based on Admiralty draughts and archival research.


Always on the go: Research into Royal Navy sailing warship design, construction and use, from Tudor times to 1790. 


Member of NRG, SNR, NRS, SMS

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6 hours ago, rtwpsom2 said:

Thanks Mark, so when it says the bowspirit is 28' outside the inner stem, that is a straight line length and not horizontal (e.g. parallel to the keel)?

That is correct - the actual length of the spar.  The angle from horizontal could be changed to a certain degree, which would change that horizontal measurement.  The physical length of the spar, however, remained the same.




Neither should a ship rely on one small anchor, nor should life rest on a single hope.

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