Deck-stepped vs. keel-stepped mast...

With Ericsons having both deck-stepped and keel-stepped masts, depending on the model/size of boat, can anyone enlighten me on advantages and disadvantages of each?

My guess is as follows:

1) deck stepped is easier to rig/de-rig for annual haul-out
2) deck stepped is easier to cut away in a de-masting crisis
3) deck stepped may cause deck compression
4) keel stepped may leave some broken off mast for jury-rigging in a de-masting crisis
5) keel-stepped may be more prone to leaks
6) keel-stepped may spread the load more evenly through the sole/hull
7) keel-stepped may be less likely to fall if any shrouds/stays break
8) deck-stepped is lighter/shorter; less weight equals more speed
9) deck-stepped may be easier to adjust for mast rake
10) keel-stepped mast may be an obstruction in the cabin

I don't know if the above is accurate--just my thoughts. Anyone disagree or have some more to add, especially if some of you have design/engineering or similar backgrounds, and can add some technical perspectives.

Thanks,
Frank.

>3) deck stepped may cause deck compression
Well, I've seen cabin top compression. We walked on a deal because of a failing deck step. It was a cabin top beam support. If you think about it the cabin top could be fine and the surrounding lower deck sink. It seems more complicated IMHO.

>4) keel stepped may leave some broken off mast for jury-rigging in a de-masting crisis
>5) keel-stepped may be more prone to leaks
The outside of the mast can be well sealed for a keel stepped. The latest is probably the Spar-tite product now used by many production manufacturers. Once the mast comes inside the cabin it seems that some water will be coming down the inside as long as the halyards are internal. The Ericson mast base wet sole plates are fed by the mast. On the other hand in the keel stepped dismasting scenario the cabin top can be cracked leaving you in storm with a large whole in the roof too. This I have read about. One fellow even converted a keel stepped boat to a deck stepped for his offshore sailing for just that reason.

I've even seen offshore sailors recommending putting all halyards external and hermetically sealing the mast for knockdown buoyancy. No kidding. So they would recommend the same buoyancy argument for a deck or keel stepped mast.

>6) keel-stepped may spread the load more evenly through the sole/hull
Good point. I'd sure like to hear from an architect/rigger on that one.

>8) deck-stepped is lighter/shorter; less weight equals more speed
I'm skeptical of that one. You can't just step onto a cabin top. The cabin needs to be reinforced to carry the load and it seems to me that means more weight. You may not really lose much weight in the end if any. Maybe I'm wrong. At the very least I'll bet that the cabin and/or deck engineering will be much more complex to carry the load. Then that extra cabin integrity will need to be maintained and inspected or watch your head !

>9) deck-stepped may be easier to adjust for mast rake
Do we really want to adjust rake or just bend ?

>10) keel-stepped mast may be an obstruction in the cabin
I've seen the deck step done with just a large lateral beam projecting down into the cabin. Other times there is another spar or two underneath the mast, or it is over a reinforced bulkhead so putting the mast there wouldn't have mattered spacewise anyway.

Neal, thanks for your reply. It will be interesting to get comments from others as well. Re: #9 mast rake/bend, I was thinking that it would be easier with a deck-stepped mast to do the initial tune with mast rake (ie. angled back), because a keel-stepped mast would tend to stay straight from the keel through the deck opening and on up. From there, a backstay adjuster would be able to introduce mast bend on either a keel or deck stepped mast, I think. Let's see what the wise men tell us....
Frank.

the rake

Frank Langer said:

Neal, thanks for your reply. It will be interesting to get comments from others as well. Re: #9 mast rake/bend, I was thinking that it would be easier with a deck-stepped mast to do the initial tune with mast rake (ie. angled back), because a keel-stepped mast would tend to stay straight from the keel through the deck opening and on up. From there, a backstay adjuster would be able to introduce mast bend on either a keel or deck stepped mast, I think. Let's see what the wise men tell us....
Frank.

Click to expand...

Sure I just figure that the rake adjustment on a keel step is factored in already. With the deck step there are more free variables but that isn't necessarily good. What I have always heard for the keel stepping is that you just center the mast in the cabin top hole with the partners, as if the rake is pre-set, and only then do you tune the rig upstairs. I've got a Spar-tite kit that I want to use but I will work with a rigger on that so I'll be getting some on site data anyway.

As you say, when the tuning heads check in we'll know a lot more. Meanwhile, stay "tuned".

Frank,

Here on the Gulf coast we think a lot about lightning. I think a keel stepped mast makes it easier to rig a good lightning protection, especially when mated to an external keel.


Ray Rhode
S/V Journey
E35-III, #189

Ray, good point about the keel-stepped mast and lightening protection, though I know that lightening protection is a whole other somewhat controversial topic! Best solution is to move to Vancouver Island, BC where the sailing is great and the lightening much less frequent!
Thanks for your contribution.
Frank.

it's too quiet

Well Frank, it looks like the big guns haven't checked in on this issue yet so we may have to make some stuff up to settle it for you .

Big gun???

Don't know about that-but as has been noted, only 8 & 9 are not accurate.

Keel stepped masts generally have an adjustable step (a range of 2-6" usually), which is enough to help set up an aft or forward rake condition. The reasons why you might want to change rake might be very heavy (go fwd) or very light (go aft) conditions, or to counter negative trim effects from long range stores being stowed on board for a passage. If you have placed lots of weight aft (hence moving the CG aft of design location), you will end up with lee helm unless you rake the rig aft to compensate, and vice-versa. So...rake can be done fairly easily either way.

As for the lighter/shorter comment, it is true that you are carrying slightly less aluminum around, but all of it is higher up, so I doubt you can gain any stability. Also, the deck will need to be beefier to support the mast compared to a keel stepped mast-which will more than offset any weight savings anyway.

The truth is the lightest construction (in terms of weight savings) would come with a keel stepped mast, and also the best load distribution from an engineering point of view.

All things being equal (of course they never are!), the keel stepped mast is the preferable and the overwhelming choice of offshore racing and cruising sailors.

For day sailing and coastal cruising, it is really not the overriding issue; if you like the performance and features of the boat, and it is well built, you are fine either way. And even for serious offshore work, athough they are certainly in the minority, deck stepped masts can and have worked fine if properly engineered.

The bottom line is that in general, this is not a reason to approve or dissapprove of a specfic boat. Provided it is a quality boat with sound engineering, either set up is acceptable, and this alone should not determine a boats' suitability (although, again, for serious ocean sailing, deck steeped mast are rare).

Hope this helps...
S:nerd:

Thanks, Seth. As always, your knowledge and experience provided the requested answer. Keep 'em coming....
Frank.