What is the Advantage of a Keel Stepped Mast?

[44'cruisingcat]

Bob this is what my question is about. It just seems to be an accepted "truth" that keel stepped is better. But what is better about it? At best there seem to be just as many pro's and con's to both. If anything there seem to be more real (rather than percieved) advantages to deck stepping a mast.

[yotphix]

Perhaps I could be so bold as to suggest that either is good if well designed and executed and neither if not. I'm not the one to define well designed and executed. Perhaps this question is a little like asking "what's better, mono or multi" in that there can be no definitive answer.

[ssullivan]

Wow... I'm surprised we aren't able to reach a conclusion on this one. I have only "heard" keel stepped was better as well. Probably got that idea the same way I "heard" Yanmar engines were better - walking around with a broker or something.

This is one of the first threads where we don't seem to even be able to arrive at close to a good answer. Very interesting.

What I have noticed (to add to the confusion) is just how *thin* masts are on some new boats. Their diameter seems to be reduced compared to some older boats.

[Sandero]

I think there are advantages to both types. Not relying on the rigging for the stick to stand is certainly one of them for keel stepped. But there are lots of tales of leaking with them... even with a deck ring seal... water can get inside though sheaves etc. and it ends up in the bilge.

I don't care the for aesthetics of a mast inside the cabin and our deck stepped has a compression post which is stout and nicely concealed within the bulkhead.

Structurally, if the stick is the proper cross section and properly stayed I see no difference as long as the compression post is done correctly.

But you do have a different set of forces at work with a keel and deck stepped mast. The deck stepped when the rig is tensioned will force the mast down at the mast step and lift the outboard sides of the deck ever so slightly. A keel stepped will allow the deck to slide up without depression/distortion of the deck.

Jef

[swagman]

Bill from GreatKetch has summed it up correctly. Any 'joint' in a mast - be it weaker or indeed stronger than the rest of the mast section - is a source of concern and will effect not only stiffness but also ones ability to tune the rig.
IMHO the minor issues of sealing any keel stepped mast where it enters the deck are nothing compared with the advatanges it provides.
Cheers
JOHN

[jzk]

What about the grounding of a deck stepped mast? What great manufacturers use keel stepped, and what great manufactures use deck?

[44'cruisingcat]

Originally Posted by swagman

IMHO the minor issues of sealing any keel stepped mast where it enters the deck are nothing compared with the advatanges it provides.
Cheers
JOHN

Yes of course. But could you elaborate on these "advantages"? So far I have heard none. In fact some of what has been said is patently incorrect. ie. that a smaller section can be used.

[delmarrey]

Which would you rather have?????

If it were to topple the mast, what would it leave you???

And how would you go about doing an at-sea repair.

IMHO A deck stepped mast would be more favorable! You could retreave it and re-step what ever's left, using your hacksaw and lines.

With a keel stepped (thru hull) mast you would have taken on more water then with the deck step'd and continue to if the waves were breaking over you. Then, any attempt to re-step that bent casting on a place with a gapping hole. would surely be a BIT more difficult!!!!!

I vote for deck stepped! (even though I have a keel stepped)............................._/)

[cat man do]

And the winner is......

delmarrey, I reckon that is the most compelling argument to date.

Good on ya

Dave

[Sandero]

The notion that a deck step is not a continuous column is not correct. The column length of a deck step is from the deck to the top of the mast... and there is nothing discontinuous about it.... no different from a flag pole column length. They're not columns anyway... more like cantilevered (stayed) beams... as most of the loading for sailing is lateral and not vertical! And consider that sailing with a stayed mast most of the force for sailing is transferred to the windward shrouds to the hull. In an unstayed mast all the forces are transferred to the hull from the mast and the mast section is usually much larger.

Rigs which have bendy masts, such as fractional ones are better suited to deck steps because the pivot point is as the deck step and not the keel step. When the mast is raked by backstay tension it will bow a bit forward in the lower section. The keel steeped mast will move a bit in its boot/seal and perhaps being to leak.

Or how about the situation where the headstay parts and the backstay pulls the mast aft and pivots it about the deck and destroys the cabin? A deck stepped would probably just topple aft like a felled tree .. Look out helmsman! ... and not tear up the interior.

No?

Jef

According to Tristan Jones, the convenience of being able to lower the mast to get under bridges far outweighs all other concerns. Don't really know myself. I have had both, and currently own both. Keel stepped seems stronger, but I sure hate the leaks. Since I have not had a mast failure, I can not really compare the two on that level.

[Joli]

Our racing boats have had both types of spars. The keel stepped masts were easier to tune because we could pre-bend the spar in the partners at deck level. Pull the butt aft and pin it. Then pull the section at deck level forward and shim behind it. Made it easy to depower and tough to invert.

I guess it's just what you are used to.

[Charlie]

I have to agree with Yotphix. In my opinion there is no correct answer to this question. Assuming that the install was done correctly there are advantages to each system:

Keel stepped advantages:
- easier to for racing.
-More solid base. (this one is questionable)
-Able to change rigging w/o a crane
-Stiffer


Keel stepped disadvantages:
-leaks
-bottom of mast prone to corrosion
-when dismasted may rip out part of deck



Deck Stepped Advantages:
-Able to lower/raise mast w/o a crane
-won't tear up cabin when dismasted
-cheaper (for builder)

Deck stepped Disadvantages:
-requires compression post
-may have problems is deck softens
-extra connection point to boat.

Please feel free to add advantages or disadvantages.

I think that each of the systems has good points and bad. I can see where a particuilar use of the boat might be more advantageous than another (i.e a race boat with a bendy rig is better able to tune the rig with a keel stepped mast or a local cruiser might want to have a tabernacle mast that they can use with an electric winch to go under bridges)

In my opinion it all comes down to a matter of personal preference.

[BobB]

Nice summary.

Calder's Cruising Handbook adds that, "for an equivalent sail-carrying capability, a keel-stepped mast can be somewhat lighter that a deck-stepped mast. The keel-stepped mast is also more capable of withstanding the failure of a piece of standing rigging."

[mike d.]

from what i have read on keel stepped vs. deck stepped is that if you were to roll over the deck stepped usually leaves a stub about up to the lower spreaders, because the deck partners support the mast in this area.
the down side is that you have a hole in the deck for water ingress, where-as with a deck stepped mast the hull-structure is more water tight. also i don't call reading anything as to the difference in standing rigging dimensions and mast extrusion dimensions for one vs. the other. smaller size mast extrusions were usually used for racing and round the bouy boats, because these mast are lighter aloft so the boat can be designed lighter to go faster. also the rigging itself is lighter to reduce weight and windage aloft.
mike