IOM mast rule question - RC Groups
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Jun 07, 2010, 12:31 PM
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A.B.'s Avatar

IOM mast rule question

So I screwed up and made my mast tube to fit my 10.9mm mast tight and keel mounted, now if I wanted to use a larger diameter mast could I use a smaller insert in the bottom of a larger mast, or do i need to covert to a deck mounted mast?
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Jun 07, 2010, 10:34 PM
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I am not sure about the rules, but Anders Wallin posted his plans for a finbox/mast box that uses a small opening for a 5mm mast foot. If it is not illegal, your 10.8mm one won't be!! It could be argued that his 5mm extension is smaller than the allowed minimum mast diameter, but it really is just a way to transfer the load from deck level to the bottom of the hull. No different than a compression post under a deck mounted mast, to me, anyway!
Jun 08, 2010, 09:10 AM
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I think you'll find that the rules talk about the height of the mast above the deck, with no detail about whether the mast is deck stepped, keel stepped or something in between.
Jun 08, 2010, 09:53 AM
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8387mike's Avatar
Ok this is interesting

(a) A mast stub arrangement is permitted and, if used, shall be taken to be part
of the mast.
(b) Between the lower point and the upper point the spar section shall be:
(1) of circular outer shape,
(2) constant
within the variations permitted by F.3.4 except for the following permitted
So a mast must be constant, what does that mean?
1) Constant size i.e. tapered lengths or different size mast widths
2) Constant lenght i.e. no joins

So how to get around this would be to insert a narrow shaft into the mast box and have a step on top of it, because unless you built the deck extremly strong it might colapse. So would this get around the above rules? would this be classified as a Step?
Jun 08, 2010, 03:16 PM
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mast stub

Hi all after reading 8387 mike's entry it kinda takes the fun out of sailing especially if you have to be a lawyer to interpet the rules have fun Casy
Jun 08, 2010, 06:40 PM
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A.B.'s Avatar
Could someone who has access to the IOM forum, please post question in the rule area? I have tried to get an account but did not work.

Thank you

Jun 08, 2010, 09:57 PM
Registered User
constant diameter... no taper. You can have two piece masts, with a joiner. The joiner can not be longer than 100 mm I think, but it makes carrying an A rig much easier!

The "Lower point" referred to above, is the point where the bottom of the sail cannot exceed (go below it), at the gooseneck. It would be hard to put any limitations on the section of the mast below the "Lower Limit Mark" because of the different vang arrangements.

I think you are good with your plans, although I made the move to a skinnier mast and would not go back to a larger mast!

Your question was posted and the thread is here ==>
Last edited by hew565; Jun 08, 2010 at 10:11 PM.

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