Question Question about ICLA Class Rule 20 (Inspection Ports)


Rule 20 reads:

Inspection ports not exceeding 153 mm internal diameter may be installed on the deck or in the cockpit to provide access to the hull cavity, provided that any inspection port is fitted with watertight threaded covers (any bayonet mounted parts are deemed to be not threaded). Storage receptacles are permitted underneath hatch covers

What is your interpretation of "internal diameter"? I assume that is referring to the internal diameter of the port, not the actual hole cut into the deck. 6 inch/152mm inspection ports typically require a cutout of about 161mm. I assume this rule is designed so that the maximum inspection port size is 6 inches.

Now to the real meat of my question: How would you measure the "internal diameter" of the this port? Highlighted in red in one of the attached renders, you can see that the smallest part of the port is actually the backing plate. If this backing plate wasn't in place, the port diameter would be 7 inches, but with the backing plate, it is reduced to 6 inches.

Would this pass inspection?


  • inspection port spacer v2 - 4.png
    inspection port spacer v2 - 4.png
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  • inspection port spacer v2 -3 .png
    inspection port spacer v2 -3 .png
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  • inspection port spacer v2 - 2.png
    inspection port spacer v2 - 2.png
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How would you measure the "internal diameter" of this port?
152+/-1 mm is a standard port size. Whether the legal maximum was originally intended to refer to the size of the actual opening or of the piece of deck to be removed, is not clear. My earliest edition of the class rules is from 1975, and this part of the rule is identical to the current one. Who knows what they thought.

Would this pass inspection?
If I were a measurer, I would pass it.
(In fact it’s a rather smart workaround for a mistake :) )