Masts and keels

[BOWDONMAN]

A short while ago I posted a question about te merits of Ferro-cement construction. Many thanks for all replies both constructive and amusing. I conclude that the main drawbacks of this method are 1) Poor resale value, ( good news as I will probably purchase something about 20 years old), and reduced stability - No problem as all I want is a leisurely circumnavigation.
I would now ask the experts among you to discuss the merits of keel stepped masts as opposed to deck ( or tabernacle ) stepped; and long keels as opposed to semi-long or fin. As I am looking at 40ft. plus and upwards of 25 tons I think bilge keels and lifting keels are out of the equation. I will almost certainly be singlehanding for most of the way so please be gentle.

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[extravert]

Keel stepped masts compared to deck stepped...

Advantages

- Stronger.
- You are not putting load on the deck. Some boats have had problems here.
- Your electric cables going up the mast can have joins inside the boat, rather than outside in the elements.

Disadvantages

- Longer mast, slightly more expensive to replace
- Slightly more difficult to step and unstep, but good riggers/crane drivers should not have a problem.
- Whatever you do it seems to be impossible to stop some water getting inside the boat at the mast, either running down the outside or the inside of the mast. Mine leaked from inside the mast from the first to the last day.
- You deck will need support from upwards force if you have halyard turning blocks attached to the deck at the mast, but a keel-stepped-mast boat should have this designed in.

I would have thought it unlikely that a boat of your proposed size and suitability for purpose would have a tabernacle stepped mast. The advantage of this method is ease of raising and lowering, but no mast on a 25 ton 40'+ boat is going to be easy to get up and down, tabernacle mounted or not.

<hr width=100% size=1>Adventures of the VAT unpaid <A target="_blank" HREF=http://www.xrayted.fsnet.co.uk>Teddy Bear Boat</A>

 

[kingfisher]

Keel steppes: more logical from a construction point of view, as the compression forces are applied directly to the keel, and not via the roof. A sagging roof is a frequent occurrence with older GRP boats. I don't know whether this applies to ferro-cement.
I would think them easier to lift, as most keel stepped masts can stand unsupported. Lifting my deck step mast is a much trickier operation: you need to make sure the crane is carying the weight when you remove the final shrouds.
Negative point for keel stepped masts: if the mast should ever fail, you could have severe damage to your deck. At least your stuck with a hole the size of your mast chord through your deck. Not nice if you have green water coming over it.

Long keels/short keel ? Well, do a search on the forum an decide for yourself. The issue has been well talked about [not opening that can of worms again]

Three words: skeg hung rudder.

<hr width=100% size=1>Group of people on the pontoon: skipper is the one with the toolbox.
http://sirocco31.tripod.com

 

[Evadne]

Long keel: slowest, doesn't like reversing, best protection for prop and rudder from both ropes and grounding. Good directional stability. My favourite.
Fin and spade: fastest, most vulnerable to damage. Saves on antifouling. Wouldn't consider it.
Fin and skeg: a good compromise but there are so many that I wouldn't generalise: some are spades with a bit of support and some are long-keels with a bit taken out of the deadwood.

Look at the underwater profile and imagine running over a semi-submerged log or a rope at 5 knots: What would get damaged and where would things get fouled? To a long-keeler, a P-bracket and a propeller forward of the skeg always looks horribly fragile and exposed, IMHO.


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