Cruisers Forum
 


Join CruisersForum Today

Reply
 
Thread Tools Rate Thread Display Modes
Old 09-12-2014, 16:30   #1
Registered User

Join Date: Mar 2014
Posts: 6
Telescopic masts?

Can somebody bring me up to speed as to why Extendable Telescopic masts are not used in sailboats? I understand it's not the most convenient solution as it gets more complex, but I can imagine the pro's of such a design.

You could lower it in a storm , lowering the center of gravity and also it's no longer a lightning attractor.
Another benefit would be its ability to be lowered to cross bridges.

whats the verdict?
__________________

__________________
Defyant is offline   Reply With Quote
Old 09-12-2014, 16:33   #2
Registered User

Join Date: Sep 2009
Location: Mackay,QLD, Australia
Boat: planning a approx 45ft cat
Posts: 3,651
Images: 3
Re: Telescopic masts?

I would suspect the weight and complex nature of the engineering for starters.
__________________

__________________
downunder is offline   Reply With Quote
Old 09-12-2014, 16:59   #3
Senior Cruiser
 
Vasco's Avatar

Cruisers Forum Supporter

Join Date: Apr 2004
Location: Toronto
Boat: CS36Merlin, "La Belle Aurore" Ben393 "Breathless"
Posts: 7,133
Re: Telescopic masts?

If there were a need perhaps someone would manufacture one but there is absolutely no need. Lowering in a storm would only make rolling more violent, there is no need to lower the cog in a storm by lowering a mast.. Lightning is unpredictable and there is no guarantee that a shorter mast would be less likely to be struck. As for bridges this is a minor issue. In many cases draft and water depths is a greater issue than the height of a mast.
__________________
Rick I
Toronto in summer, Bahamas in winter.
http://groups.yahoo.com/group/beneteau393/
Vasco is offline   Reply With Quote
Old 09-12-2014, 17:01   #4
Senior Cruiser
 
s/v Beth's Avatar

Cruisers Forum Supporter

Join Date: Oct 2008
Location: Coos Bay, Oregon
Boat: Valiant 40 (1975)
Posts: 4,066
Re: Telescopic masts?

I am afraid that I brought this up. This is where I got the idea. From big tankers using sails:
"Each five-segment collapsible sail, estimated to cost about US$2.5 million, will be hollow and constructed of durable, lightweight aluminum and fiber-reinforced plastic. Similar in shape to an aircraft wing in cross section, the sails can be positioned independently of one another to maximize thrust and, while at anchor or in bad weather, can telescope down in what is known as "vertical reefing."
ww.gizmag.com/next-gen-ships-sails-lower-fuel-use/22289/
Now I am not sure that this technology will be incorporated into the next generation of cruisers, but it certainly could be. I think the advantages of a lightweight solid sail that could be reefed directly downward sound good to me.
As noted above, though, I could see how this might make the roll greater. What affect does a sea anchor have on rolling during a storm?
__________________
s/v Beth is offline   Reply With Quote
Old 09-12-2014, 17:03   #5
Bailing as fast as I can.
 
GILow's Avatar

Join Date: Sep 2008
Location: Adelaide, South Australia
Boat: Swanson 42
Posts: 3,585
Re: Telescopic masts?

Well, given that most conventional masts are supported by stays that exert a large downward force in an effort to extract the small sideways support vector available from the angle of the stay to the mast, I would say that a telescoping mast would be a nightmare to engineer. The compression force on the mast would be pretty great just sitting at anchor, and once the sail is drawing nicely, the increase in compression force as the stays on the upwind side are loaded up would be huge.

Stayless masts would not have this problem, but then the weight of the mast would problematic (because of the neccesary double-up of the layers of mast to support the joins) and again, sail luff tension would excert significant compression forces in some situations.

Lowering a mast to get under bridges is not that hard if you design for it beforehand, I actually watched a Beneteau do it recently, and they didn't even stop the boat. They had a crew of about six on board a 40ish footer, and they were re-rigged and hoisting sails within a mile of the bridge. Clearly they had some kind of specialised setup, but the point was the rig looked pretty normal to me.

As for storms, well, reefing a sail seems a lot easier than reefing a mast. Even if you lower the mast, you still have to gather up the excess sail somehow and keep it under control.


No doubt someone has done it, but I bet they found it was not worth the effort. So I guess my take is, sure it should be possible, but the engineering challenges, the weight, the consequences of failure, all outweigh the possible benefits.

Matt
__________________
Very funny Scotty, now beam down my clothes.
http://www.swansonsailor.id.au
GILow is offline   Reply With Quote
Old 09-12-2014, 17:34   #6
Senior Cruiser

Cruisers Forum Supporter

Join Date: Nov 2012
Location: Long Beach, CA
Boat: Tayana Vancouver 42
Posts: 1,853
Re: Telescopic masts?

Fully rigged ships would extend the height of their masts by sending up additional spar sections. The idea isn't new and the advantages are obvious if the mechanics could be worked out.


Sent from my iPhone using Tapatalk
__________________
Tayana42 is online now   Reply With Quote
Old 09-12-2014, 18:07   #7
Registered User
 
Delancey's Avatar

Join Date: Oct 2011
Location: Miami, FL
Boat: sunk by irma
Posts: 3,462
Re: Telescopic masts?

Not uncommon on a gaff rig to have a topsail on a separate sprit. Been around for years and years.
Attached Thumbnails
Click image for larger version

Name:	image.jpg
Views:	167
Size:	34.4 KB
ID:	93297  
__________________
Delancey is offline   Reply With Quote
Old 09-12-2014, 18:39   #8
Registered User

Join Date: Nov 2014
Location: Alameda
Boat: Bluewater 40, Cal 20, Bayliner Avanti
Posts: 275
Re: Telescopic masts?

..I remember saw a german sailboat with a telescopic antenna as a mastil...
..yes. for real!!! During the sweet '80 on Hamburg...
Yes, I laugh a lot....
__________________
En medio de la noche, sigo siendo luz...
garrobito is offline   Reply With Quote
Old 09-12-2014, 20:10   #9
Senior Cruiser

Cruisers Forum Supporter

Join Date: Dec 2006
Location: Seattle
Boat: Cal 40
Posts: 2,401
Images: 7
Re: Telescopic masts?

I don't think comparing old time ships with heavy solid timber masts against today's lightweight aluminum and carbon fiber masts doesn't work well.

As someone else pointed out the mast is important for damping. In Seaworthiness the Forgotten Factor it states that more than 50% of the moment arm can be due to the mast and rigging. In Fastnet 79 many of the boats capsized only after losing their masts.
__________________
cal40john is offline   Reply With Quote
Old 09-12-2014, 20:21   #10
Senior Cruiser
 
s/v Beth's Avatar

Cruisers Forum Supporter

Join Date: Oct 2008
Location: Coos Bay, Oregon
Boat: Valiant 40 (1975)
Posts: 4,066
Re: Telescopic masts?

Quote:
Originally Posted by cal40john View Post
As someone else pointed out the mast is important for damping. In Seaworthiness the Forgotten Factor it states that more than 50% of the moment arm can be due to the mast and rigging. In Fastnet 79 many of the boats capsized only after losing their masts.
I am not doubting you for a minute Cal40, but do you have a quote for that? I have always wondered how the motion of my Valiant is much better than some much larger ships in heavy seas. Could this be a factor? BTW, that motion damping would not be the same with a Catamaran because they dampen from the large beam right? So they would benefit from a reducible mast?
__________________
s/v Beth is offline   Reply With Quote
Old 09-12-2014, 20:59   #11
Senior Cruiser

Cruisers Forum Supporter

Join Date: Dec 2006
Location: Seattle
Boat: Cal 40
Posts: 2,401
Images: 7
Re: Telescopic masts?

Quote:
Originally Posted by s/v Beth View Post
I am not doubting you for a minute Cal40, but do you have a quote for that? I have always wondered how the motion of my Valiant is much better than some much larger ships in heavy seas. Could this be a factor? BTW, that motion damping would not be the same with a Catamaran because they dampen from the large beam right? So they would benefit from a reducible mast?
The moment arm discussion is part of an entire chapter on design effects on seaworthiness. There are graphs, tables, equations, some of the data coming from tank testing of scale yachts with and without masts in breaking waves. The chapter also has a lot to say about hull shape, and weight influences.
__________________

__________________
cal40john is offline   Reply With Quote
Reply

Tags
mast

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


Similar Threads
Thread Thread Starter Forum Replies Last Post
For Sale: Telescopic Whisker Pole riggear Classifieds Archive 4 12-11-2013 19:04
Want To Buy: WTB - Tiller Extension - Telescopic Spinlock 1980240D Classifieds Archive 2 24-09-2012 11:07
Want To Buy: WTB - Tiller Extension - Telescopic 1980240D Classifieds Archive 0 07-09-2012 08:52
Unstayed masts or stayed masts? Joli Deck hardware: Rigging, Sails & Hoisting 29 22-07-2008 03:56
Masts and booms cheap! Trecksail Construction, Maintenance & Refit 1 07-02-2005 17:17



Copyright 2002- Social Knowledge, LLC All Rights Reserved.

All times are GMT -7. The time now is 20:13.


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.