Cruisers Forum
 


Reply
  This discussion is proudly sponsored by:
Please support our sponsors and let them know you heard about their products on Cruisers Forums. Advertise Here
 
Thread Tools Search this Thread Rate Thread Display Modes
Old 07-07-2018, 15:17   #1
Registered User

Join Date: May 2018
Location: Niagara Falls
Boat: Oops -jumped the gun
Posts: 62
Dismasting: Deck or keel stepped outcomes?

I have a few questions.

What boat is likely to be dismasted easier? Keel or deck stepped?

I'm looking at lots of boats and think it would be mighty hard for a keel stepped mast to get yanked out of the step and further yanked out of the hull. Aren't mostly lateral forces at play during a dismasting?

On a recent boat I was on, deck stepped, the mast foot and deck step were both sturdy chunks of 1/2" think material, a foot square. The actual bolts to do the attachment weren't any bigger that 3/8 or so. They appeared to be a really weak link in the system.

Another boat, keel stepped, looked like it had a collar a few inches high the mast base dropped into and was attached to.

It appears to me, regardless of how well the deck stepped attachment is engineered, a keel stepped mast is more likely to stay in place during a knockdown or rollover.
__________________
What have I done?
wallythacker is offline   Reply With Quote
Old 07-07-2018, 16:19   #2
Registered User

Join Date: Nov 2015
Location: Fl
Boat: Wauquiez Hood 38
Posts: 1,187
Re: Dismasting: Deck or keel stepped outcomes?

Dismasting occurs when you lose a shroud or stay. If engineered correctly both deck and keel stepped masts are reliable till you lose a shroud or stay.
__________________
Keth

Boat Vinyl Lettering and Graphics
Bleemus is offline   Reply With Quote
Old 07-07-2018, 16:26   #3
Moderator Emeritus
 
a64pilot's Avatar

Cruisers Forum Supporter

Join Date: Oct 2013
Location: Jacksonville/ out cruising
Boat: Island Packet 38
Posts: 31,351
Dismasting: Deck or keel stepped outcomes?

I believe the mast itself will fail on a keel stepped boat, likely close to where it goes thru the cabin roof, so that it will be very close to the same as a deck stepped mast, if you lose a stay or chainplate.
Either if properly Engineered is fine, neither if not is.
A keel stepped mast is nearly impossible to have a bone dry bilge as water will come down the mast, so I donít try. Other than that Iím not sure there is much real difference
a64pilot is offline   Reply With Quote
Old 07-07-2018, 16:46   #4
Registered User

Join Date: Oct 2017
Location: No home port, full time liveaboard
Boat: Beneteau Oceanis 50 (aka 49)
Posts: 292
Re: Dismasting: Deck or keel stepped outcomes?

A keel stepped mast may cause damage to the cabin top when dismasted. I prefer deck stepped for that reason and mostly because they don’t systematically leak as a64pilot said. Dismasting is unlikely, leaking is near certain. A desk stepped mast can pop out of the foot in some worst case scenarios though, without loosing shrouds. This requires a really bendy boat. But that too is very unlikely.
2big2small is offline   Reply With Quote
Old 07-07-2018, 16:54   #5
Registered User

Join Date: Oct 2015
Posts: 2,007
Re: Dismasting: Deck or keel stepped outcomes?

Far more important than deck stepped or keel stepped is proper rig tuning. Many, maybe even most, boats sail with rigging too slack.

If the wires are sloppy, it doesnít matter where the bottom of the mast is
billknny is offline   Reply With Quote
Old 07-07-2018, 22:03   #6
Moderator
 
Jim Cate's Avatar

Join Date: May 2008
Location: cruising SW Pacific
Boat: Jon Sayer 1-off 46 ft fract rig sloop strip plank in W Red Cedar
Posts: 21,356
Re: Dismasting: Deck or keel stepped outcomes?

Quote:
Originally Posted by billknny View Post
Far more important than deck stepped or keel stepped is proper rig tuning. Many, maybe even most, boats sail with rigging too slack.

If the wires are sloppy, it doesnít matter where the bottom of the mast is
Seems to me that it matters quite a lot! Slack rigging in a keel stepped mast will let it bend more than optimum, but that in itself won't cause failure. But in a deck stepped mast, as was posted above, it can jump out of the step, and that is near certain to cause failure of the tube, and damage deck or house in the process.

The two common failures in keel stepped masts are loss of the upper panel when a cap shroud fails, or folding in the lower panel with subsequent snapping off above the partners when a lower fails. The latter is what happened to us in our previous yacht... a clean break about 200 mm above the deck, folded mast over the side to leeward. No deck damage, minor hull damage from the end of the tube before we got it cut away.

No personal experience with shroud failures in deck stepped rigs, but had two spreader failures in our Catalina 22. Top of the mast bent over to leeward, nothing else broke, and one case we finished the race (failure occurred only a few hundred meters from the finish. Boat didn't go to windward all that well with the mast bent ~ 30 degrees, but we struggled on. Went from leading the race to DFL, everyone else gone home, but didn't want a DNF on our record!).
Since the lowers were still set and the rig still erect, we were not really dismasted, but not a pretty sight and in need of a new tube!

Jim
__________________
Jim and Ann s/v Insatiable II, lying Port Cygnet Tasmania once again.
Jim Cate is offline   Reply With Quote
Old 08-07-2018, 09:18   #7
MJH
Registered User
 
MJH's Avatar

Join Date: Feb 2007
Location: Gig Harbor, WA
Boat: Tayana Vancouver 42ac
Posts: 1,216
Re: Dismasting: Deck or keel stepped outcomes?

I think the question is phrased incorrectly.

If comparable boats (one keel stepped, one deck stepped) are stepped correctly and tuned to their individually designed optimum, then their likelihood to dismasting to the same conditions should be the same.

However, how these boats perform under the same wind/water conditions will be somewhat different with the keel stepped mast having a lower center of force (forward movement) than the deck stepped mast. We must remember that the primary reason that sailboat manufacturers have gone to the deck step mast was economics and marketing (providing more space in the cabin) not performance...the proverbial trade-off.

A national sailing magazine favors a keel stepped mast over a deck stepped mast for offshore use as the safety benefits outweigh the convenience benefits.

~ ~ _/) ~ ~ MJH
MJH is offline   Reply With Quote
Old 08-07-2018, 09:56   #8
Moderator
 
noelex 77's Avatar

Cruisers Forum Supporter

Join Date: Jul 2007
Boat: Bestevaer.
Posts: 14,825
Re: Dismasting: Deck or keel stepped outcomes?

A mast section that is a couple of metres longer will be cheaper than engineering the deck to to accommodate the mast loads, but I agree this does give the boatbuilder some interior options that otherwise would not be possible.

I think a completely dry bilge is the main advantage of a deck stepped mast. This is particularly important on a metal boat, but helps all boats with the early identification of potential problems, as well as the reduction in condensation and mould.
noelex 77 is offline   Reply With Quote
Old 08-07-2018, 10:15   #9
Moderator

Join Date: Jun 2015
Posts: 6,335
Re: Dismasting: Deck or keel stepped outcomes?

Why, Wallythacker, do you ask the question? You are "looking at lots of boats", you say, and I read into that, that you are new to sailing. Are you asking because you have concerns that you may find yourself in circumstances where you might lose your mast?

That is most unlikely to happen to any "factory built" boat that a sailing novice is likely to acquire and to sail in any conditions of wind and wave that could cause a dismasting.

What CAN happen - and has happened to me skippering a "fleet boat" that had not been properly maintained - is that a shroud or a stay will break. That can certainly be an unsettling experience for a novice, but it is not one that causes the immediate loss of the mast. The first thing a sailor does if one of the several wires of the standing rigging breaks is to take the load of the rigging. What he does after that depends on the particular circumstances.

So if the standing rigging of any given boat has been properly maintained and is properly "tuned", there is really nothing to worry about regardless of whether the mast is deck-stepped or keel-stepped. As a selection criterion that, in itself, is not really worth worrying about as you go shopping.

If you scull around on YouTube you'll find a number of clips of sailboats being "knocked down". You will see that they come back up again with the mast intact. Note also that it is never the wind that knocks down a boat - it is the waves.

There is no need to get into that canaworms now if your concern is merely whether keel-stepped or deck-stepped is safer for a novice. A novice has many much more immediate things to worry about :-)!

However, if you are interested in the engineering and tuning of rigs there are many people on this forum who will be glad to give you a quick intro. It is a vast and rather slippery subject, conceptually, so perhaps, if you are a novice, you want to "sneak up on it" as you go. It is best tackled after you have some actual sailing experience :-)

All the best

TrentePIeds
TrentePieds is offline   Reply With Quote
Old 08-07-2018, 16:25   #10
Registered User

Join Date: Sep 2007
Location: Queensland, Australia
Boat: None at present--between vessels. Ex Piver Loadstar 12.5 metres
Posts: 1,475
Re: Dismasting: Deck or keel stepped outcomes?

If you intend being dismasted at some stage, a keel-stepped mast is going to rip a big hole in your deck as like as not--whereas the deck-stepped model is going over the side and trailing along on its stays while it bashes your hull to bits from the outside--just as the keel-stepped portion of the mast will also be doing.

Personally I do not like either. I like ease of use and zero worries, so I like a bipod rig or several bipod rigs depending on size of vessel, especially for multihulls. All sails can be furler rigged and no mast at the leading edge of the sail, all sails can be wishbone boomed completely and self-tacking, balanced exactly, the bipod masts are cheaper, and rigging and deck stresses much lessened. Both the top and bottom of a bipod mast can be moved without trouble, to optimise performance, if the mounting flanges are made adjustable. Just before a blow a bipod mast can be lowered and lashed. You can not do this with any other rig. If you like crab-claw sails with most of their spread in the clean air well above deck on your multihull, a bipod rig, or two or more bipod rigs, is your best and simplest option.

The ancient Egyptians knew what they were doing three or four thousand years ago. Somewhere along the way we forgot.
Mike Banks is offline   Reply With Quote
Old 08-07-2018, 17:44   #11
Registered User

Join Date: Feb 2013
Posts: 16
Re: Dismasting: Deck or keel stepped outcomes?

None of the replies suggest the authors have actually had a dismasting. I have. The cabin top mast went over the side owing to compression failure of the mast and by itself did little damage. The real challenge was to undo the complex of rigging amidst heavy ocean swells. Subsequently we upgraded the rig and bought the very largest cable cutter we could find !

From an engineering point of you either mast set up can be made satisfactory. As to making water tight mast boots we didn’t find that a challenge during 100,000 plus miles of blue water sailing. Bilges always have some water from condensation, etc.

If the questioner is really interested about keeping the rig aloft the number one advise is replacing the rig based on usage/sailing conditions. And using Staylocks rather than swaging which will ultimately fail in the tropics. Just give it time. Staylocks, heavy chain and multiple anchors all indicate the serious blue water sailor. Any blue water sailor ought be prepared for a rig failure, update the rig and carry repair equipment. Decades of experience have shown the real dangers are being run down by commercial ships. Not loosing ones rig.
piberman is offline   Reply With Quote
Old 08-07-2018, 17:49   #12
Registered User

Join Date: May 2012
Location: Tweed Heads,N.S.W. Australia
Boat: Dinghies to Admirals Cup contender,the lot.
Posts: 141
Re: Dismasting: Deck or keel stepped outcomes?

We lost our 70 foot stick returning from a Sydney Hobart.....keel mounted.....rod rigging cap shroud....in 15 knots.....mast broke 12" above deck....only paint and lifeline damage.


Have seen about 6 other vessels Ö.each a race yacht.....after dismasting...mix of deck and keel mount.....nil deck damage......other than on lifelines and sides Ö.. due to shrouds 'sawing' until released.
grahamb is offline   Reply With Quote
Old 08-07-2018, 18:14   #13
Moderator
 
hpeer's Avatar

Cruisers Forum Supporter

Join Date: Dec 2008
Location: Between Caribbean and Canada
Boat: Murray 33-Chouette & Pape Steelmaid-44-Safara-both steel cutters
Posts: 8,718
Re: Dismasting: Deck or keel stepped outcomes?

What is “dismasting”?

We were in Nanny Cay, BVI a few months ago. My rough guess is there were 100 boats in the yard, on stands. Maybe 60 had broken masts. Just my wild guess. But the point is a ton of boats were “dismasted” on the hard. I’ll bet there were more boats dismasted in that single yard than in the rest of the world for 2017.

WHY were they dismasted”? Well obviously hurricane winds working on rigid structures. Boats, monks especially, are meant to heal when pressed and that dumps the lateral load. If the boat is rigidly held in stands then it can’t dump the load and something breaks.

Masts are held up by their stays. New boats, in general, have fewer stays than older boats. Some have as few as 3 stays. Many have only 4. On those rigs if any one stay goes it’s game over. Also all the load is coming down on just 3 or 4 stays. So there is a lot of stress in them.

Our old school boats are different. Our 44’er has 14 stays including runners. It went through Irma with the back stays disconnected, but the runners were cinched tight and held. (Yard didn’t perform promised work #%*+). 80 knots wind. Our small boat has 11 stays, the runners are permanent.

So that’s my take on it. If the boat rolls all bets are off, way too many variables and hugely bigger forces involved.
hpeer is offline   Reply With Quote
Old 08-07-2018, 18:16   #14
Moderator

Join Date: Jun 2015
Posts: 6,335
Re: Dismasting: Deck or keel stepped outcomes?

Perhaps we should let WallyThacker come back to us and tell us something about his sailing/cruising plans, his sailing experience and the particular boat he may be contemplating, before we get into the exotica of personal experiences. The name of the game is to give USEFUL council to novices and even to the merely curious rather than scare the bejapers out of them ;-)

Cheers

Tp
TrentePieds is offline   Reply With Quote
Old 08-07-2018, 18:31   #15
Moderator and Certifiable Refitter
 
Wotname's Avatar

Join Date: Jan 2008
Location: South of 43 S, Australia
Boat: C.L.O.D.
Posts: 21,071
Re: Dismasting: Deck or keel stepped outcomes?

Quote:
Originally Posted by MJH View Post
...........

However, how these boats perform under the same wind/water conditions will be somewhat different with the keel stepped mast having a lower center of force (forward movement) than the deck stepped mast. ........

~ ~ _/) ~ ~ MJH
Could explain / expand on this as I can't see any reason why the centre of force should be different?
__________________
All men dream: but not equally. Those who dream by night in the dusty recesses of their minds wake in the day to find it was vanity: but the dreamers of the day are dangereous men, for they may act their dreams with open eyes, to make it possible. T.E. Lawrence
Wotname is offline   Reply With Quote
Reply

Tags
deck, dismasting, keel, mast

Thread Tools Search this Thread
Search this Thread:

Advanced Search
Display Modes Rate This Thread
Rate This Thread:

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Similar Threads
Thread Thread Starter Forum Replies Last Post
Keel stepped, deck stepped, tabernacle? Bluefuss Monohull Sailboats 16 18-01-2013 11:58
Keel-stepped or Deck-stepped Mast? heronspeak Deck hardware: Rigging, Sails & Hoisting 15 08-09-2012 22:04
Keel-Stepped vs Deck-Stepped . . . jdeatsch Deck hardware: Rigging, Sails & Hoisting 54 19-11-2010 16:20
Converting Keel-Stepped to Deck-Stepped Mast Ben M-P Monohull Sailboats 8 19-11-2010 06:57
Aluminum Keel-Stepped Mast to Iron Keel - Grounded ? endoftheroad Construction, Maintenance & Refit 11 30-09-2010 14:47

Advertise Here


All times are GMT -7. The time now is 03:14.


Google+
Powered by vBulletin® Version 3.8.8 Beta 1
Copyright ©2000 - 2024, vBulletin Solutions, Inc.
Social Knowledge Networks
Powered by vBulletin® Version 3.8.8 Beta 1
Copyright ©2000 - 2024, vBulletin Solutions, Inc.

ShowCase vBulletin Plugins by Drive Thru Online, Inc.