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Old 25-09-2011, 08:36   #1
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Deck- vs Keel-Stepped Mast

Hi all,
In my research yesterday I visited a Hunter 50AC and liked what I saw except for the deck stepped mast. I'm going to buy within a year or so. I've never considered this type of rigging because it looks like trouble in heavy weather. Granted, I don't intend to have much sq footage up in a gale but regardless it looks like the trade off is cabin space for mast integrity.

So here is my question: Since Hunter has been producing good quality boats for many years, I can't see the architects making intentional comprimises that would jeapordize the boats integrity.

So I put it to you, the tried and true, to help educate me in rigging. Am I right or wrong. Would you feel absolutely confortable crossing the Atlantic/Pacific in a boat of this design?

Thanks,
Jon
Maybe its a stupid question? I just don't know.
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Old 25-09-2011, 08:46   #2
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Re: Deck vs Keel Stepped Mast

i dont personally believe there is anything inherently less seaworthy about a deck stepped mast and long is there is the support for it (compression post or full structural bulkhead with beams...)

now with a keel stepped mast one of 2 things will happen if you are rolled over real hard:

1. the mast will break at or slightly above deck level leaving you with a good short spar to put on deck for a jury rig or...

2. the mast will rip out massive portions of the cabin top in its effort to break leaving you completely and utterly f-ed with a huge hole in the top of your boat... there is plenty of pictorial evidence of this happening on the internets..
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Old 25-09-2011, 09:18   #3
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Re: Deck vs Keel Stepped Mast

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Originally Posted by pressuredrop View Post
......
now with a keel stepped mast one of 2 things will happen if you are rolled over real hard:

1. the mast will break at or slightly above deck level leaving you with a good short spar to put on deck for a jury rig or...

2. the mast will rip out massive portions of the cabin top in its effort to break leaving you completely and utterly f-ed with a huge hole in the top of your boat... there is plenty of pictorial evidence of this happening on the internets..
Or even number 3, the mast will come out of the mast base and pound a whole through the bottom of the boat.

There's no evidence that keel stepped vs deck stepped is significantly safer on a modern rigged boat. Emotionally a keel stepped mast may feel stronger.
(said by a man with a keel stepped mast)
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Old 25-09-2011, 09:31   #4
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Re: Deck vs Keel Stepped Mast

Thanks, guys. I was hoping that sort of answer would come out of this. (It was a Catalina, not a Hunter, btw.)

I don't intend to be out on the water in seasons when serious weather is about. And I'll keep just enough sail out to manuver safely. I"m pretty conservative.
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Old 25-09-2011, 10:15   #5
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Re: Deck- vs Keel-Stepped Mast

There are arguments in favor of both mast designs, but IMO, choosing a boat based on the results of a rollover is like choosing an automobile based on its the chances of its surviving being hit by a locomotive.

Far more masts are lost due to rigging failure than rollovers, and in that case the keel step has a better chance of survival. Both designs when well designed and maintained will provide competent service.

Cheers,

Jim
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Old 25-09-2011, 10:53   #6
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Re: Deck- vs Keel-Stepped Mast

When we bought our Hartley 35 I noticed that the masts didn't intrude into the cabin space and realised (a touch belatedly) that they were deck stepped. Since the whole structure (decks, hull and superstructure) are all ferro and the (aluminium) masts are well shrouded and stayed, I can't see it being a huge problem in all but the most extreme conditions. The boat's thirty seven years old, if it was going to be an issue, I think it would have been one by now.

I concur, that in a modern rig, assuming the standing rig and the mast and step are in good order and condition, neither is particularly likely to give trouble. That said, the point that a damaged mast pulled out of the keel step can then proceed to knock itself a new one in the bottom of the hull is well taken, I've certainly heard of things like that happening.

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Old 25-09-2011, 10:57   #7
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Quote:
Originally Posted by AussieGeoff
When we bought our Hartley 35 I noticed that the masts didn't intrude into the cabin space and realised (a touch belatedly) that they were deck stepped. Since the whole structure (decks, hull and superstructure) are all ferro and the (aluminium) masts are well shrouded and stayed, I can't see it being a huge problem in all but the most extreme conditions. The boat's thirty seven years old, if it was going to be an issue, I think it would have been one by now.

I concur, that in a modern rig, assuming the standing rig and the mast and step are in good order and condition, neither is particularly likely to give trouble. That said, the point that a damaged mast pulled out of the keel step can then proceed to knock itself a new one in the bottom of the hull is well taken, I've certainly heard of things like that happening.

AussieGeoff

Thanks AussieGeoff! Notes taken.
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Old 25-09-2011, 11:09   #8
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Re: Deck- vs Keel-Stepped Mast

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Originally Posted by AussieGeoff View Post
That said, the point that a damaged mast pulled out of the keel step can then proceed to knock itself a new one in the bottom of the hull is well taken, I've certainly heard of things like that happening.

AussieGeoff
Yes, and a deck stepped mast can jump out of its step and knock a big hole in the deck or house and then go overboard. "I've certainly heard of things like that happening".

Come on, guys... one can imagine failure modes for any setup. There are countless sailboats with both mast designs that have sailed safely for their entire service lives. The design, execution and maintenance of the whole rig is more of a factor in choosing a used boat than which stepping system is used.

Cheers,

Jim
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Old 25-09-2011, 11:18   #9
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Re: Deck- vs Keel-Stepped Mast

I have never understood the need for a keel stepped mast. Engineering wise I guess I'm missing the point. A mast is essentially a column in compression, and even worse, it may have dynamic side loads. The slenderness ratio determines how easy it will buckle and fail, and the longer it is, the worse it is. When straight it will take tons of load, but as soon as it starts to bend a little.... everything changes. If I remember right , Young's Modulus is the predictor of failure. So my vote is to NOT have a keel stepped mast. Of course you want a compression post below deck.
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Old 25-09-2011, 11:32   #10
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Re: Deck- vs Keel-Stepped Mast

i have 2 keel stepped masts and keel stepped sampson posts. my mnasts are shorter than many as is a ketch and short also because is not meant to race.
the mast on my ericson is longer than is my main mast on my formosa. ericson is deck stepped and formosa is keel stepped.
there is much to consider with each kind, and different problems for repairs.
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Old 25-09-2011, 12:00   #11
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Re: Deck- vs Keel-Stepped Mast

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Originally Posted by Jim Cate View Post
Yes, and a deck stepped mast can jump out of its step and knock a big hole in the deck or house and then go overboard. "I've certainly heard of things like that happening".
Oh absolutely. I'm not suggesting either is necessarily better or worse, just different.

Quote:
Originally Posted by Jim Cate View Post
Come on, guys... one can imagine failure modes for any setup. There are countless sailboats with both mast designs that have sailed safely for their entire service lives. The design, execution and maintenance of the whole rig is more of a factor in choosing a used boat than which stepping system is used.
Absolutely concur. Anything can fail, and either of the consequences could be equally catastrophic.

Cheers

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Old 25-09-2011, 12:10   #12
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Re: Deck- vs Keel-Stepped Mast

The main difference for the ordinary buyer is what to look for when buying.

Deck stepped : check very carefully for deformation of the deck, poor fit of doors inside the cabin (or even doors that won't open!)

Keel stepped : Check the mast base very carefully for rot, especially on Catalinas.
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Old 25-09-2011, 12:11   #13
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Re: Deck- vs Keel-Stepped Mast

You can get by with a slightly lighter extrusion and/or slightly narrower shroud chain plate location with a keel stepped mast. Because the lower part of the mast is supported at the partners and keel, it adds some rigidity to the very lower portion of the mast. Something racers are dieing to have but they are nuts to begin with. It's unimportant to the rest of us as it's easily compensated for.

To me. keel stepped masts are a real negative. First is the problem with water running down inside the stick constantly adding water to the bilge. Sealing at the mast partners at the deck is another issue. That seems to be a fixable issue with the two part, pour in place goo to replace the wedges that used to be a constant issue. Then there was the huge pole in the cabin. You still have to support the mast when it's deck stepped but you can do it with a much smaller post.

The big advantage claimed for a deck stepped mast is that if you lose a wire, you'll still have a stump for a jury rig is largely bogus in my opinion. If you lose a cap shroud, fore, or aft stay, you'll probably still have the mast to the lower shrouds whether it's deck or keel stepped. Lose a lower shroud and the mast will almost always fail at the deck leaving you with nothing for a jury rig. In addition, with a keel stepped mast you'll probably have to hack saw off the mast where it bent. That's no easy feat in a seaway wth the stick dragging in the water.

I've done 10s of thousands of miles of offshore sailing, all on boats with deck stepped masts. Never a problem.
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Old 25-09-2011, 12:13   #14
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Re: Deck- vs Keel-Stepped Mast

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Originally Posted by Cheechako View Post
I have never understood the need for a keel stepped mast. Engineering wise I guess I'm missing the point. A mast is essentially a column in compression, and even worse, it may have dynamic side loads. The slenderness ratio determines how easy it will buckle and fail, and the longer it is, the worse it is. When straight it will take tons of load, but as soon as it starts to bend a little.... everything changes. If I remember right , Young's Modulus is the predictor of failure. So my vote is to NOT have a keel stepped mast. Of course you want a compression post below deck.
You make an interesting point about a compression post. From the term, I suspect it is a supporting post below the mast step that transfers the load down (presumably to the keel).

As near as I can see, my boat has nothing like that. It too is a ketch and therefore the loads (particularly on the mizzen) are not as great as a typical masthead sloop. I wondered about this and I'm betting that the designer thought of it, so I'm assuming something in the structure of the cabin (the whole structure, deck, cabin and hull is ferro) possibly a frame or something like it, is there to carry the load.

I've attached a couple of pics, one looking forward from the cockpit into the saloon, the other looking forward along the cabin top from roughly the same spot.

I don't have the plans for the boat, so I can't look it up. If anyone else has/had a Hartley Queenslander and knows how it is/was done, or if they just know how it was done, I'd be pleased to hear from them.

AussieGeoff
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Old 25-09-2011, 12:23   #15
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Re: Deck- vs Keel-Stepped Mast

There is a box like piece of furniture at the forward end of the table. I'll bet that is your mast post or is hiding the mast support post. Your mast probably sits on top of that bulkhead/box. There are a few boats that use a truss system to support the mast. That allows them to get by without a center post. The load still has to be transfered to the keel but it's done by posts/bulkheads off the centerline. The Santa Cruz 27 and the old Columbia 22 come to mind.

Your boat is very nicely finished out. If more cement boats had been built like yours, they be more respected.
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