Rain water coming in through the inside of the mast? - SailNet Community
 
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post #1 of 8 Old 04-18-2003 Thread Starter
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Rain water coming in through the inside of the mast?

This is not really a big deal since my vessel is all glass with a foam core. But, I''m trying to keep a dry boat. My mast is a Z-Spar stepped on the keel with internal lines and whenever it rains I get water in the bilges. Over the years it has rotted out the wooden floor joists and I''ve replaced them with syntheic materials so this will not happen again. This is a fin keeled vessel with about 3" of bilge space.


Does anyone have this same problem and what did you do about it. Or, am I just going to have to live with that little bit of water always collecting under my deck.


DelmarRey in Seattle
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post #2 of 8 Old 04-19-2003
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Rain water coming in through the inside of the mast?

First of all, when you say ''floor joists'' I assume that you mean the transverse frames that are typically glassed to the hull. While these may coincidentally hold up the deck their real purpose is to distribut keel and rig loads into the hull. Plastic tends to bond poorly and be more flexible so that the choice of using plastic for floor frames is a pretty poor one and one that can cause fatigue due to increased flexure where the hull turns down into the bilge. I would suggest that you use the plastic frames as mold and throughly glass (mat, then roving set in epoxy)completely over them in order to properly create a set of transverse frames.

As to rain water getting into the bilge. This is something that I too am wrestling with. I really hate keel stepped masts and that is one of the primary reasons. My current thinking is that if I ever go offshore I will have my mast cut off at the deck line and have a rigid base plate made at the deck line, close the deck partners and reinforce the deck at the mast base, and then have rigid top plates added to the top of the mast stub in the cabin. When complete the mast baseplate would be through bolted through the deck into the stub mast. The result a stronger mast (rigid end connection vs semi rigid), a mast that won''t leak into the bilge, and a mast that will stay aboard just like a keel stepped mast but a mast that can be jetissoned at sea if necesary.

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post #3 of 8 Old 04-19-2003
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Rain water coming in through the inside of the mast?

DelmarRey:
Yes, all keel stepped masts (especially /w internal halyards) allow water in.
One of the many reasons I hate shallow bilges w/out deep sump.
BTW: You likely suffer from siome mildew on the under side of your sole (floorboards); which can be treated /w chlorine bleach & scrubbing - then soak the underside of the boards /w ethylene-glycol type anti-freeze.
Jeff:
Interesting idea; converting keel stepped to deck stepped. I like the idea of being able to separate the mast (jettison at sea) from the hull.
Supspect, tho'', that the deck reinforcement at mast base could be problematic. Would''nt the lower mast stub only provide a compression post?
How about merely "sealing" the interior of the mast at the deck partner (or anywhere beneath the lowest mast opening), and drilling a weeping hole immediately above the seal?
I never bothered, as my diaphram bilge pump kept the deep sump pretty dry.
I''d like to hear more ...
Gord
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post #4 of 8 Old 04-19-2003
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Rain water coming in through the inside of the mast?

I don''t know how much engineering that you are familiar with but here is how I am looking at this. I did discuss this with a couple folks that work at Farr (which are the folks who designed my boat.) While nothing was conclusive, they were in basic agreement with the logic on this.

To begin with, if, in its original keel stepped setup, the setion of the mast that is below the deck is considered as being an extra ''panel'' of the mast, which they usually are for design purposes, and which is why keel stepped masts are sometimes touted as being stronger, then the deck structure has to be designed to take thrust from the mast in all horizontal directions. Some decks are designed to take horizontal loading and some aren''t. Where the deck is not reinforced to take horizontal thrust then a keel stepped mast is actually significantly weaker than a deck stepped mast, but that is another story.

At least in the case of my boat, it would appear that the deck is intended to take horizontal loads as there are glassed in fore and aft and athwarthips bulkheads at the mast. So glassing in the hole in order to take horizontal loads is really pretty easy.

The next element of the design problem is the portion of the mast below the deck. No, it is not simplu acting in compression. If the top plate of the post below the deck (kingpost) is welded and gusseted to the kingpost, and the base of the mast is similarly weleded and gusseted so that a moment connection can be made on both sides, and then the plates are thru-bolted to each other through the deck, then a moment connection is made through the deck and the post below the deck will recieve some moment loadings. The base of the mast will then be a fixed end connection and so will in effect have the extra panel implied in a keel stepped mast.

So that''s the idea.

Jeff
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post #5 of 8 Old 04-20-2003
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Rain water coming in through the inside of the mast?

Jeff:
As always, I am impressed /w your post(s).
Of course, the deck (of a keel-stepped rig) must (have been) designed to support the Horizontal loading - and your (upper & lower) Gussets/Plates should take care of the Moment.
I was making a mountain out of a molehill.
Thanks!!!
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post #6 of 8 Old 04-21-2003
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Rain water coming in through the inside of the mast?

Further to converting from Keel to Deck Stepped Mast:
I''n not a Structural Eng (nor Architect); but I know enough to get myself into real trouble!

1. I don''t understand your reference to "another Panel". What is a "panel" in this context?

2. The "Moment Connections" between mast & king post will have to be at least equal to the Mast Base Moment Capacity (from section modulus).
If the gusseted plates are separated by the deck (newly sealed mast aperture), then deck compression becomes an added factor in the calculation.
Perhaps it might be better to carry the king post thru'' the opening, sealing around it (spec''d to accept horizontal loading), and make the moment connection immediately above the house deck.
If you''re not tired of the subject, your further thoughts will be appreciated.
Regards, and thanx for the GREAT input,,
Gord
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post #7 of 8 Old 04-22-2003 Thread Starter
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Rain water coming in through the inside of the mast?

Well, it looks like I''ll have to live with a wet bilge. As for the floor supports, they are not part of the structure. They are an add-in after the completion of the hull which has it''s own molded in hollow stringers through out the vessel.

Jeff, you make a good point about the stepped mast for off shore. I''ll keep that in mind for my final vessel (retirement). And thanks to you both for the input

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post #8 of 8 Old 04-23-2003
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Rain water coming in through the inside of the mast?

Much easier to just seal the inside of the mast. Convert to a deck-stepped mast?! And I thought I was paranoid!

Having said that I still have not sealed mine. My bilge is deep, the pump works, and there are too many other projects.
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