IOM Bow Bumper & Chainplate

Measurement Guides – BUMPER MEASUREMENT

The following diagram provide some guidance on measuring an IOM bumper. The class rules state that the forward 10 mm of the hull shall comprise elastomeric material — that is, be a bumper. The Equipment Rules of Sailing say that this measurement shall be taken with respect to the waterline. So the bumper in diagram “A” is NOT legal, because part of the forward 10 mm of the hull is not elastomeric. The bumpers of “B” and “C” are permitted, since all of the forward 10 mm of the hull is a bumper, even though in “B” this bumper thins out to 0 before it reaches the waterline.


http://www.iomclass.org/doc-files/Technical/IOM%20CR%20Interpretations/Interpretation%202004-IOM-3.pdf

Interpretation requested by the German NCA as follows:
1. Is the bow bumper of a boat which meets the required 10 mm only at deck level and thinning towards the water line in accordance with IOM Class Rules?

Discussion
Class Rule D.2.2(c) is dealing with “the forward 10 mm of the hull”. Relevant ERS rules are H.2.1 and H.2.4. According to them, longitudinal measurements such as “forward 10 mm of the hull” shall be taken parallel to the horizontal hull axis. Therefore the hull forward of a vertical plane 10 mm aft of the foremost point of the hull and at 90 degrees to the hull centreplane has to comply with class rule D.2.2(c).
Decision
A hull which consists only of elastomeric material forward of a vertical plane 10 mm aft
of the foremost point of the hull and at 90° to the hull centreplane complies with class
rule D.2.2(c).


CHAINPLATES

http://iomclass.org/doc-files/Technical/IOM%20CR%20Interpretations/Interpretation-2013-IOM-1.pdf

Relevant IOM Class Rules: 

D.2.3(c) Fittings shall not project outboard of the hull shell or deck.

Relevant ERS rules:
D.1.1 Hull – The shell including any transom, the deck including any superstructure, the internal structure including any cockpit, the fittings associated with these parts and any corrector weights.
H.3.1 – For a boat, unless otherwise specified, words such as “fore”, “aft”, “above”, “below”, “height”, “depth”, “length”, “beam”, “freeboard”, “inboard” and “outboard” shall be taken to refer to the boat in measurement trim. All measurements denoted by these, or similar words, shall be taken parallel to one of the three major axes.
Conclusion:
Shrouds attachment points (chainplate eyes) as shown on sketch and marked with A, C, D, E and F and
shown on photo are not projecting outboard of the hull shell and they are permitted by the IOM Class Rules.
Shrouds attachment points (chainplate eyes) as shown on sketch and marked with B are projecting outboard outboard of the hull shell and therefore not permitted by the IOM

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