Are keel-stepped masts a thing of the past?

[dlochner]

Even though deck stepped masts typically have a structural column under them, I've always found keel stepped masts to somehow be more 'intrusive' in the living space. I'm not sure why, perhaps they need more space around them to facilitate pulling the mast when needed.

Designers can disguise the compression post with bulkheads and furniture making it less intrusive.

Keel stepped masts always leak. Rain will come in through the many holes in the mast and run down inside. Sealing the mast at the partners can be challenging. Mine always leaks a little in heavy rain.

The design advantage to a keel stepped mast is the ability to use a lighter more flexible mast which has some advantages with reduced weight aloft and ability to bend the mast to shape the sails.

 

[Scott T-Bird]

I'll conclude that keel-stepped masts are incorporated in modern design. But I still find it curious that it doesn't seem to be important from a marketing standpoint. For instance, I looked at the current Tartan website and I could not find one reference in any of the models whether or not the masts are keel stepped. They did advertise carbon masts and a few photographs and a few layout sketches show a keel-stepped mast. But there was no mention anywhere of this design feature ... not even in the specifications that were presented for one model. It simply may not even be important enough to mention ... or it's just assumed that shoppers would know somehow?

 

[Scott T-Bird]

I like my deck stepped mast. I always found it impossible to keep keel stepped masts from having some water infiltration - I really like a dry boat.

Even though deck stepped masts typically have a structural column under them, I've always found keel stepped masts to somehow be more 'intrusive' in the living space. I'm not sure why, perhaps they need more space around them to facilitate pulling the mast when needed.

I agree. My compression post is basically a 4" diameter lally column and is nowhere near the cross-sectional size of the mast. From a structural standpoint, it is doing exactly the same thing as a keel-stepped mast but with less cross-sectional area.

Actually, I was a bit surprised that the carbon masts on Tartans could be keel-stepped. Carbon poles are great for unidirectional loads, but I thought they fold easily around a bending moment such as at the deck partner. But, I'm sure they have that figured out.

 

[JamesG161]

My Compression Post is on the main structural Beam which is good Design by Hunter.

Jim...

 

[FastOlson]

It got me to thinking about modern yacht design and if keel-stepped masts are even designed for modern boats. It seems to me that deck-stepped is the norm, even for the upper-echelon of modern blue water designs. True or not?

This question comes up regularly on various forums. I do wish you had not introduced it via the "when did you stop beating your wife?" approach...
As another poster pointed out there are real performance advantages to a keel-stepped spar. Also some small further advantage to a tapered spar. Also to having a narrow shroud base, and double spreaders.
All of these features will increase potential performance, but at a higher build cost. When our boat was built, there was a robust market for dual purpose sailboats that could perform well in continuous offshore service, and also have comfortable interior amenities. Our design has all of those performance enhancers.

Sadly, this part of the sailing market has been declining for 20 years.

Most customers nowadays seem to want a sail boat that sails well on nice days, in a limited performance envelope of approx. 7 up to 14 knots of true wind, and waves under two feet (or lower).

There is no profit in building boats for a larger Performance Envelope. Boats are built to make money, not to educate the unknowing.

As for deck stepped spars, offshore boats like the race-winning Cascade 36 have been gathering trophies and circumnavigations (equally) since the 70's. Of course that owes much to naval architect Robert Smith, and no-compromise scantlings from the former Yacht Constructors yard in Portland. Mast specs depends on meeting the stresses of sailing and then designing the mast and rig adequately.

For strength, either system can meet sea going requirements, but the deck-stepped spar system will (mostly) always have a bit more weight up high and sacrifice some performance.

Given that the sea and wind are pretty much a constant, it's Marketing that continues to change sail boat design.
And always... YMMV !

 

[dLj]

Actually, I was a bit surprised that the carbon masts on Tartans could be keel-stepped. Carbon poles are great for unidirectional loads, but I thought they fold easily around a bending moment such as at the deck partner. But, I'm sure they have that figured out.

Carbon fiber is very complex. It can be designed for specific loadings in various directions. You can customize the carbon fiber cloth to be capable of loadings from different directions. If you are working with a cloth manufacturer and making custom cloth that is outside the standard range available, might take a year or two to get the cloth actually made. At lease that was the case a few years ago. But they do make various cloth designs that handle different directional loadings and you can use that cloth and alter the way you lay it up to further customize for what you are building. Just a FYI....

dj

 

[Kings Gambit]

I have noticed that on several keel-stepped boats, the mast below is basically in the way of salon use. Very awkward working around them; whereas not so much compression posts. With negligible safety or performance differences, a mast stepped yacht would be preferred, IMO.