Keel-Stepped vs Deck-Stepped . . .

[sneuman]

I'm less agnostic on this than I used to be. This year I had to do some deck work on my boat that involved temporarily compromising the (keel-stepped) rig, which remained rock-solid even after shrouds and stays were (carefully) taken off. Of course, that wouldn't have been the case with the deck-stepped mast on my last boat. The strength of the rig is only one advantage of a keel-stepped mast, but it's the only one that really counts, IMHO.

[MC01]

Originally Posted by RTB

I just did the Harvest moon Regatta on a Pacific Seacraft 37 (deck stepped btw) and we had some near gale force winds heading down the coast. Here is a boat that had a problem with a keel stepped mast - Massive mast failure in Galveston to Port Aransas Race | North American Sailor

Not sure if it has been determined what the actual cause for the failure was, but it sure is ugly!

I can't comment on which is best, if one is or not, but your standing rigging is your friend. Oh, and the compression post if deck stepped.

Aren't most catamarans deck stepped?

Wow! This pic is worth a thousand words, thanks for posting it. The risk of shreading the interior with a keel step mast always comes up in these debates, but I've never actually seen a case of it.

[delmarrey]

I'm not sure being keel stepped had much to do with all the damage on this boat. It looks as though the mast fell on the deck splitting it open.
When I enlarged the picture below and the original the cabin looks like chopped glass, a very weak construction method.

When mast failed it sank into the boat, the rigid vang essentially going through the deck, then mast falling off to the water,

.

[RTB]

From the link I provided - "No standing rigging failure (stays), mast buckled to windward just above the base of the rigid boom vang above deck. Because the mast was keel stepped, the deck damage was large. When mast failed it sank into the boat, the rigid vang essentially going through the deck, then mast falling off to the water, perpendicular to the starboard side of the boat to leeward."

The same could happen on a deck stepped mast too. Just saying a mast can have it's weaknesses, and fail, even if it is keel stepped. A newb might tend to believe the rig is Bullet-Proof because it is keel stepped.

This is a video of our boat during the Harvest Moon Regatta. 150 miles, one tack, 27 hours. I have no worries with deck stepped, as long as the rigging is in good condition. The video was from early Friday morning, and the winds and waves picked up throughout the day before our arrival at 5 pm.

http://www.youtube.com/watch?v=4sKl0szVmdI

[osirissail]

If you look around at the new sailboat's masts these days you will find that they are made in two or more parts and then riveted together to make one mast. This is because it is no longer viable to manufacture and ship full length masts. So the new masts come in "shipping container" lengths and are "assembled" at the boat manufacturing site or commissioning site. Even upscale Selden masts are multi part.
- - So deck stepping the masts becomes a major economic plus for the boat manufacturer as they can use shorter mast tube lengths. Also the boat manufacturer can build the whole boat on schedule and then later step the mast on deck. Same thing with worldwide shipping of the new boats - they can be shipped on container ships intact and the masts shipped separately for assembly at the "commissioning" sales point. It's all about money and price-point.

[delmarrey]

Originally Posted by osirissail

If you look around at the new sailboat's masts these days you will find that they are made in two or more parts and then riveted together to make one mast. This is because it is no longer viable to manufacture and ship full length masts. So the new masts come in "shipping container" lengths and are "assembled" at the boat manufacturing site or commissioning site. Even upscale Selden masts are multi part.
- - So deck stepping the masts becomes a major economic plus for the boat manufacturer as they can use shorter mast tube lengths. Also the boat manufacturer can build the whole boat on schedule and then later step the mast on deck. Same thing with worldwide shipping of the new boats - they can be shipped on container ships intact and the masts shipped separately for assembly at the "commissioning" sales point. It's all about money and price-point.

Not sure if this is all true but I do know if my mast (keel stepped- 60' OAL) were to be replaced the shipping would cost more then the whole standing rig.

[Jim Cate]

Hmmm, that's really puzzling !

From the description, it sorta sounds like perhaps the step failed first... "mast sank into the boat". Once that happened, the tube wasn't supported by the shrouds any more and it buckled. I hope that a more detailed post mortem will be published.

Must have been pretty traumatic!

Cheers,

Jim

[MC01]

Originally Posted by RTB

From the link I provided - "No standing rigging failure (stays), mast buckled to windward just above the base of the rigid boom vang above deck. Because the mast was keel stepped, the deck damage was large. When mast failed it sank into the boat, the rigid vang essentially going through the deck, then mast falling off to the water, perpendicular to the starboard side of the boat to leeward."

The same could happen on a deck stepped mast too. Just saying a mast can have it's weaknesses, and fail, even if it is keel stepped. A newb might tend to believe the rig is Bullet-Proof because it is keel stepped.

This is a video of our boat during the Harvest Moon Regatta. 150 miles, one tack, 27 hours. I have no worries with deck stepped, as long as the rigging is in good condition. The video was from early Friday morning, and the winds and waves picked up throughout the day before our arrival at 5 pm.

Thanks for the clarification, and nice vid!

I've wondered about PSC now going with the more bendy Charleston Spar masts instead of the really robust LeFeil masts used when they were being built in CA. Presumably, one can order a sturdier mast from Charleston Spar also, but several of us noticed a "demo" PSC at Annapolis in 2009 had the mast raked back a fair amount. This situation leads me to think it may be a good thing to request the stronger (but less bendy) mast if ordering new, since PSCs are intended for offshore use. I'd have some misgivings about using multi-piece masts in the rough stuff. I know it's done - but it'll be interesting to hear if most of these implementations fair well over time with more widespread and varied use.

[beetle]

Originally Posted by MC01

Thanks for the clarification, and nice vid!

I've wondered about PSC now going with the more bendy Charleston Spar masts instead of the really robust LeFeil masts used when they were being built in CA. Presumably, one can order a sturdier mast from Charleston Spar also, but several of us noticed a "demo" PSC at Annapolis in 2009 had the mast raked back a fair amount. This situation leads me to think it may be a good thing to request the stronger (but less bendy) mast if ordering new, since PSCs are intended for offshore use. I'd have some misgivings about using multi-piece masts in the rough stuff. I know it's done - but it'll be interesting to hear if most of these implementations fair well over time with more widespread and varied use.

You may be confusing 'stiffness' with 'strength'.

A mast can be engineered to be strong and flexible in the same way it can be engineered to be strong and stiff - it depends upon which you prefer and what you're willing to pay for. A key feature was mentioned earlier in this thread: when engineering the spar a keel-stepped mast will achieve the same strength as a deck-stepped mast with a significant weight savings, as the support provided by the partners of a keel-stepped mast is significant to how the mast will handle bending loads.

For my part, I have a three spreader keel-stepped mast built for me by Ballenger Spars, and it's a ton of fun to sail with as the mast can be tuned while under way (runners/checkstays/backstay/babystay are all adjustable) which provides a lot of options for tuning the sail plan, particularly the mainsail. However, if I weren't interested in making those adjustments (and maintaining all the rigging that goes with them) then I would rather have a stiffer 'telephone pole' mast that has little-to-no fine-tuning while underway.

As regards splicing a spar together from pieces, the splice is engineered to be stronger than the local mast wall with vertical tapers top and bottom. I have no issue with a mast that is spliced, provided the splice is done well. Like all other components on the mast, a splice should be inspected periodically to verify the mechanism (machine screws, rivets, welds, etc.) remains in good condition.

As regards mast manufacturers, Selden spars seems to use a minimum mast wall thickness for the section, and these spars tend to be like big limp noodles; they also work as I see them in a lot of boats. LeFiell spars are simple telephone pole spars and work well too. Both are relatively inexpensive relative to a custom-built racing rig; the choice depends upon what you're interested in as regards mast performance.

[gettinthere]

our keel stepped mast is dry in 90% of the rains. Only heavily wind driven rain gets into the mast and down below. All of the halyard openings have a lip on them to deflect rain water. The mast boot is bone dry.

[roverhi]

The failed mast and interior damage were caused by lower shroud failure according to the post. The mast buckled in the middle which made a vicious club out of the below deck section. A deck stepped mast probably would just have gone overboard where it could still be a problem but not like the above destructive ram. Racing specs. call for pinning the base of a keel stepped mast to the step to try and prevent the above disastrous damage.

Any loaded spar will fail if it loses a cap shroud on the windward side. Doesn't matter whether it's keel stepped or deck stepped. Both will probably buckle at the next lower supported spreader. You will still have a stub mast section to jury rig a sail on in both instances. There is a slight chance that a keel stepped mast that loses lower shrouds will stay up but it's very slight especially if the mast section is lighter to take advantage of keel stepping. Once again, the above post is an example where keel stepping did not prevent the loss of the stick.

If you look at the extrusion specs, 45' is about the longest extrusion section that you can buy. Any mast over that length has to be spliced. Splicing has been common forever. It has little, if anything, to do with the manufacturer trying to cut corners. FWIU, there is a problem with quality control when you try and extrude very long spars. That is the reason that the available sections are the length they are. The spices are represented to be stronger than the unspliced mast section.

I don't know whether the Selden mast sections are any more or less bendy than LeFiell's. I would hope they are both engineered to withstand the expected loads with the rigging intact. I would opt for the lightest possible mast system, however. Weight aloft is the biggest negative for sailing ability followed by weight in the ends of the hull.

My keel stepped mast was not dry. It let considerable water into the boat everytime it rained and it rained a lot in Norfolk the winter I lived aboard. Not a pleasant experience to deal with.

[MC01]

Originally Posted by beetle

You may be confusing 'stiffness' with 'strength'.

Specifically, for any given boat, I'm wondering if it would be better to go with a thicker walled mast extrusion for offshore use. I.e., Is it better to give up mast bend and to tolerate additional weight aloft in order to obtain the increased strength the additional wall thickness would provide? I realize cross section shape, alloy, tempering, number of spreaders, manufacturing and quality practices, etc. all play a role as well. I'm sure the answer is, "it depends" - how risk adverse you are, what priority you place on performance vs. safety, design considerations with your specific boat, etc. etc..

I'm just "wondering out loud" since, in this situation, the initial indication is the spar itself failed just above the boom vang attachment. It'd be interesting to know how that attachment was made to the mast - perhaps that could have introduced a weakness? If so, would a thicker walled extrusion have been helpful? How concerned should we be with metal fatigue when using "bendy" masts - as they get older and have gone through many cycles of bending, are they more prone to fail? Or, is this case a rare failure and we shouldn't try to draw any specific lessons from it? Although the conditions were rough, they didn't seem THAT rough, and there was no knock-down mentioned. There must have been some other contributing factor at work.

[sneuman]

Originally Posted by roverhi

There is a slight chance that a keel stepped mast that loses lower shrouds will stay up but it's very slight

Do you have any evidence for this or is it just conjecture? I'm not trying to be pissy, just asking. My gut is that losing a lower shroud (which I would think is more common than multiple failures) has something closer to an even chance of survivability with a keel-stepped mast. But again, I have no direct evidence other than my own experience with my own keel-stepped mast at the dock.

My last boat was deck-stepped and I did suffer a dismasting at sea, but there's nothing about the circumstances that I can remember that would be informative in this debate.

[delmarrey]

Again I think the mast failure had little to do with the mast, whether being keel or deck stepped.
If you look at the boat itself it was a failure all on it's own. It's only a foot shorter then my light weight racer but 5000 # less in displacement. If the chain plates pulled out, that right there would destroy any mast. They stopped making these boats in 1989 and for a good reason, I'm sure. Chopped glass has no place in high performance boats. You couldn't give me one!

And yes you can buy sticks longer then 45'. LeFiell advertises a 58' & Sparcraft boasts about its 70' just as a start.

This boat is a bad example.

[MichaelC]

This is all very, very interesting, and I thank all posters here for the detailed information, as well as informed speculation. In fact, this reinforces my reliance on traditional building. Round [not oval] solid masts, gaff rig, no spreaders, keel stepped, parceled and served galvanized rigging wire with eyes of round seizings, dead eyes and lanyards. Robust mast step with large socket, heavy partners, simple mast boot. Wins no races except the one to the bank. It is dirt cheap to build, lasts forever with simple maintenance, and it isn't hard to look at, either.