Cruisers Forum
 


Join CruisersForum Today

Reply
 
Thread Tools Rate Thread Display Modes
Old 10-11-2012, 05:22   #16
Senior Cruiser
 
skipmac's Avatar

Cruisers Forum Supporter

Join Date: Oct 2007
Location: 29 49.16 N 82 25.82 W
Boat: Pearson 422
Posts: 12,374
Re: Thru-mast Or Mounted On The Coachroof?

Quote:
Originally Posted by Rakuflames View Post
I have a question for you -- purely academic as my rigging is in good condition (not my opinion -- it's been checked).

I have a Hunter with swept-back spreaders, so I have a lot of rigging (it does have a split backstay). I get how easily the mast could come down if the forestay or back stay snapped, but there are three shrouds on each side. I do have line on board to replace one if it pops, but ... with three shrouds (assuming I'm not in adverse conditions at the time) ... would the mast be at risk of coming down immediately if one of those six shrouds gave? I hope I never find out from real experience but ... such discusions make us newer sailors curios, to say the least ...
Fortunately don't have personal experience of this but from reading every incident of rig loss I see I can offer an opinion based on that information.

First, will depend on which shroud and the point of sail. I'm assuming your three shrouds per side are fore and aft lowers, one upper?

The most severe result will depend on whether you lose a windward or leeward shroud. More common is the loss of a windward shroud since those will be under the most stress. If you lose a windward upper shroud you will most likely lose at least part of the mast. Loss of a lower is less common and if you do lose a lower you have a much greater chance of saving the mast.

I have read of situations where a boat lost a windward upper shroud, tacked instantly and saved the mast. I think this is rare as usually the mast goes immediately with the shroud.

While not stressed the loss of a windward shroud does happen, usually due to something coming loose from the movement of the shroud rather than breaking. Unless it goes unnoticed and the boat is tacked it would be rare to lose the mast in this case.

These scenarios are based on a reach. Running downwind you can have stress on the shrouds on both sides but otherwise similar situation.
__________________

__________________
The water is always bluer on the other side of the ocean.
skipmac is online now   Reply With Quote
Old 10-11-2012, 06:27   #17
Senior Cruiser
 
osirissail's Avatar

Cruisers Forum Supporter

Join Date: Feb 2009
Location: A real life Zombie from FL
Boat: Gulfstar 53 - Osiris
Posts: 5,416
Images: 2
Re: Thru-mast Or Mounted On The Coachroof?

Quote:
Originally Posted by rebel heart View Post
. . . My vote would be for spare cable clamps, knowing how to use them, and some amsteel. Tie a quick trucker's hitch and you can fashion a temporary stay pretty quick. . .
I would add to that - that inspecting your standing rigging, especially before and during a circumnavigation will go a long way to preventing any catastrophic failures. Most failures occur where the wire enters the terminal fittings or just inside. Water wicking its way inside combined with lack of oxygen leads to stainless steel intragranular corrosion and failure of the wire. Brown/black/redish stains are the telltale that you might be getting a problem.

But in my "spare parts kit" for rigging I keep a couple Sta-Lok Long Stud Terminals that are great for repairing such a problem. Also if you use Sta-Loks terminals be sure to put some silicon caulk inside the fitting during final assembly to insure that water cannot seep inside.

Sta-Lok Long Stud Terminals
Attached Thumbnails
Click image for larger version

Name:	long_stud_terminal.jpg
Views:	52
Size:	3.1 KB
ID:	49503  
__________________

__________________
osirissail is offline   Reply With Quote
Old 10-11-2012, 11:45   #18
Senior Cruiser
 
Sailmonkey's Avatar

Cruisers Forum Supporter

Join Date: Sep 2009
Location: Houston
Boat: '76 Allied Seawind II, 32'
Posts: 5,773
Quote:
Originally Posted by osirissail

Also if you use Sta-Loks terminals be sure to put some silicon caulk inside the fitting during final assembly to insure that water cannot seep inside.

Sta-Lok Long Stud Terminals
I thought they specifically said to not use silicone as the ammonia was bad for everything involved. From memory, I thought they wanted a poly sulfide used.
__________________
Sailmonkey is offline   Reply With Quote
Old 10-11-2012, 12:29   #19
Senior Cruiser
 
Jim Cate's Avatar

Cruisers Forum Supporter

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: 11,450
Re: Thru-mast Or Mounted On The Coachroof?

Quote:
Originally Posted by Sailmonkey View Post
I thought they specifically said to not use silicone as the ammonia was bad for everything involved. From memory, I thought they wanted a poly sulfide used.
No, they specifically DO say to use silicone sealant. There is no ammonia in the silicone, but there is acetic acid, but this is harmless (white vinegar) to the 316 s/s terminal.

Cheers,

Jim
__________________
Jim and Ann s/v Insatiable II , lying Port Cygnet, Tasmania once again
Jim Cate is online now   Reply With Quote
Old 10-11-2012, 16:35   #20
Senior Cruiser
 
osirissail's Avatar

Cruisers Forum Supporter

Join Date: Feb 2009
Location: A real life Zombie from FL
Boat: Gulfstar 53 - Osiris
Posts: 5,416
Images: 2
Re: Thru-mast Or Mounted On The Coachroof?

Boatlife Caulk is specifically recommended by Sta-Lok - see: Sailing Services - Sta-Lok Assembly Instructions
__________________
osirissail is offline   Reply With Quote
Old 10-11-2012, 17:14   #21
Senior Cruiser
 
Sailmonkey's Avatar

Cruisers Forum Supporter

Join Date: Sep 2009
Location: Houston
Boat: '76 Allied Seawind II, 32'
Posts: 5,773
That's what I thought. Boatlife life-caulk is specifically polysulfide. Not silicone
__________________
Sailmonkey is offline   Reply With Quote
Old 10-11-2012, 18:48   #22
Senior Cruiser

Cruisers Forum Supporter

Join Date: Aug 2009
Location: between the devil and the deep blue sea
Boat: a sailing boat
Posts: 17,314
Re: Thru-mast Or Mounted On The Coachroof?

Quote:
Originally Posted by carstenb View Post
(...) Other opinions? For coastal cruising, I feel rooftop masts are fine. Different story when blue water.

I believe there are IMOCAs, VORs and Minis with deck stepped masts. Also plenty of out-and-out bluewater cruising boats. In my eye, both solutions work fine if they are designed and executed fine. Both give trouble when not.

b.
__________________
barnakiel is offline   Reply With Quote
Old 10-11-2012, 19:54   #23
Senior Cruiser
 
Jim Cate's Avatar

Cruisers Forum Supporter

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: 11,450
Re: Thru-mast Or Mounted On The Coachroof?

Quote:
Originally Posted by Sailmonkey View Post
That's what I thought. Boatlife life-caulk is specifically polysulfide. Not silicone
OK guys, this is very interesting. This morning I googled sta-lok assembly instructions, and the first one that came up looked exactly like the sheet that came with the last batch of sta-loks that I bought some years ago. It really did say to use silicone sealant.

So, after reading your posts, I went back and couldn't find the one I had this morning. Did find the official Sta-Lok site, and they make NO mention of using sealant of any sort.

Hmmm... then I found a Sailnet forum thread that had some references, and one chap had actually queried Sta-Lok on the subject. They said that it was up to the user whether to use sealant or not, but (despite their earlier advice) said not to use acid cure silicones, for the acetic acid would attack the s/s. Interestingly they no longer mention using Lock-tite on the threads, either. Wonder what gives there?

Hmmm again... so I looked up the tables of chemical resistance for metals (see http://www.pexuniverse.com/docs/pdf/...tance-data.pdf) where it says quite clearly that even highly concentrated acetic acid had NO EFFECT on 316 s/s. This is in agreement with my memories from laboratory applications years ago.

So, I'm somewhat confused! However, I have used acid cure silicone in both Sta-Lok and Norseman terminals in teh past with no issues. I certainly think that some sort of sealant should be used, and there is certainly no reason not to use a polysulphide based one if the silicone worries you.

I still think that they are great terminals!

Cheers,

Jim
__________________
Jim and Ann s/v Insatiable II , lying Port Cygnet, Tasmania once again
Jim Cate is online now   Reply With Quote
Old 10-11-2012, 23:48   #24
Registered User
 
stillbuilding's Avatar

Join Date: Jan 2008
Location: Hong Kong
Boat: Custom Freya 20m
Posts: 961
Quote:
Originally Posted by osirissail
One thing that is probably driving the use of deck stepped masts versus keel-stepped is the ability to route the running rigging from the mast to the cockpit. It is quite easy and economical to do with deck stepped masts. However. with keel stepped masts, there needs to be serious modifications made to the cabin top/mast interface to allow the running rigging to be routed to the cockpit.
Can you elaborate on this cos I do not understand. Do you mean using a tie to prevent deck distortion?
__________________
stillbuilding is offline   Reply With Quote
Old 11-11-2012, 00:21   #25
Senior Cruiser
 
osirissail's Avatar

Cruisers Forum Supporter

Join Date: Feb 2009
Location: A real life Zombie from FL
Boat: Gulfstar 53 - Osiris
Posts: 5,416
Images: 2
Re: Thru-mast Or Mounted On The Coachroof?

Quote:
Originally Posted by stillbuilding View Post
Can you elaborate on this cos I do not understand. Do you mean using a tie to prevent deck distortion?
Yes, most cabin top are designed to resist downward direction forces but looks what happens when you have running rigging that is led back to the cockpit from the mast.

Take a halyard for instance. The line is attached to the headboard of the sail and the bottom of the sail is attached to the boom which is attached to the mast tube. The halyard is then run up to the mast head where it goes around a sheave (pulley) and back down the mast tube. Then the halyard is attached to another sheave attached to the cabin top usually at a mast ring which is bolted to the cabin top then the halyard is redirected aft to the cockpit.

Since the keel stepped mast is sitting on top of the keel, tightening the halyard "pulls" up on the sheave attached to the mast ring or cabin top. This exerts a force pulling the cabin top upwards distorting it. Anti-pumping rods are commonly used to redirect this force to the keel. This is a thin stainless steel rod that runs inside the cabin from the cabin top down to the keel just behind the mast tube itself.

With deck/cabin top stepped masts the sheave is attached to the mast shoe sitting on top of the cabin top so the forces are contained within the mast tube system and the only possible force is aftwards - the mast base being pulled towards the cockpit. But this is a direction that the cabin top can easily resist.

So with a keel-stepped mast a clamping system needs to be attached to the mast tube at the cabin top level to transfer the vertical forces off the cabin top and back onto the mast tube system or an anti-pumping rod added. Basically this is one or more parts that need to be manufactured and properly installed and maintained which can be avoided with deck-stepped mast systems.

When I converted my running rigging from being situated at/on the mast tube to being run back inside my pilothouse, I designed and had the clamping collar built as part of the deck ring that covers/seals the hole through the cabin top where the mast passes on its way to the keel.

Additionally, these days, shipping mast tubes which are 60+ feet (18m) long from manufacturing plant to boat assembly plant is rather expensive. Deck stepped masts are about 7 ft +/- (2.2m) shorter and subsequently easier to ship. And if you look now at the really new boats you will see a joint about halfway up the mast that allows the boat manufacturer to get masts that are - obviously - only half as long when shipped to them and then assemble the mast system to full length at the boat.
__________________
osirissail is offline   Reply With Quote
Old 11-11-2012, 00:34   #26
Senior Cruiser
 
osirissail's Avatar

Cruisers Forum Supporter

Join Date: Feb 2009
Location: A real life Zombie from FL
Boat: Gulfstar 53 - Osiris
Posts: 5,416
Images: 2
Re: Thru-mast Or Mounted On The Coachroof?

As to using Sta-Lok versus swaged fittings - during the last rigging job I did a few years ago I found that the number of "shops" has have the huge 50-ton or heavier rolling swagging machine had drastically decreased. So having new stays and shrouds made now cost nearly the same as the cost of the wire and a Sta-Lok type fitting. Adding in the feature of Sta-Lok type fittings of being able to be "re-used", purchasing wire with swagged terminals was not competitive anymore.

But be careful, the different manufacturers of reusable compression terminals like Sta-Lok, Norseman, etc. have to make their system slightly different to avoid Patent infringement. Sta-Lok is unique in that they use a little circular dished "cup" (called a "former") under the "cone" that allows during assembly and tightening the strands of wire passing around the cone to maintain their alignment and not be "dragged" by friction with the base body of the fitting. I prefer this system so use Sta-Lok exclusively.

See: Sta-Lok Formers
Attached Thumbnails
Click image for larger version

Name:	f0332-01.png
Views:	66
Size:	24.6 KB
ID:	49566  
Attached Images
 
__________________
osirissail is offline   Reply With Quote
Old 11-11-2012, 03:11   #27
Moderator
 
Seaworthy Lass's Avatar

Cruisers Forum Supporter

Join Date: Oct 2008
Boat: Aluminium cutter rigged sloop
Posts: 12,815
Re: Thru-mast Or Mounted On The Coachroof?

Quote:
Originally Posted by carstenb View Post
So here is a question for the experienced blue water cruisers. What are your opinions on coachroof mounted masts, as they are in most production boats today. Versus a thru-roof mast that is stepped in the keel?

My boat has a thru-mast. I will be circumnavigating so I feel this is a necessity.

Other opinions? For coastal cruising, I feel rooftop masts are fine. Different story when blue water.

Our super strongly built aluminium boat was designed with a deck stepped mast. We were not looking at mast stepping as a big factor in boat selection. Both are fine for blue water cruising if well designed and fitted. It is not the keel but the shrouds that hold the mast up.

A few advantages with deck stepping in my opinion:
Absolutely no water ingress (our bilge is always bone dry and is used for storage)
No damage to the deck in a dismasting
More room down below
__________________
"The cure for anything is salt water: sweat, tears or the sea." Isak Dinesen
"To me the simple act of tying a knot is an adventure in unlimited space." Clifford Ashley
Seaworthy Lass is offline   Reply With Quote
Old 11-11-2012, 03:22   #28
Registered User

Join Date: Dec 2009
Posts: 3,016
Images: 4
Re: Thru-mast Or Mounted On The Coachroof?

Quote:
Originally Posted by osirissail View Post
... So with a keel-stepped mast a clamping system needs to be attached to the mast tube at the cabin top level to transfer the vertical forces off the cabin top and back onto the mast tube system or an anti-pumping rod added. Basically this is one or more parts that need to be manufactured and properly installed and maintained which can be avoided with deck-stepped mast systems.
Keel stepped masts should have a system that retains the foot in the shoe. Otherwise if the rig fails the remaining portion has been known to flail around inside the cabin until it destroys something important ... like the hull.

In my opinion either keel or deck stepped is fine so long as it has been properly designed for the task.
__________________

__________________
daddle is offline   Reply With Quote
Reply

Thread Tools
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




Copyright 2002- Social Knowledge, LLC All Rights Reserved.

All times are GMT -7. The time now is 01:43.


Google+
Powered by vBulletin® Version 3.8.8 Beta 1
Copyright ©2000 - 2017, vBulletin Solutions, Inc.
Social Knowledge Networks
Powered by vBulletin® Version 3.8.8 Beta 1
Copyright ©2000 - 2017, vBulletin Solutions, Inc.

ShowCase vBulletin Plugins by Drive Thru Online, Inc.