Mast, spreader, shroud design, help - SailNet Community

   Search Sailnet:

 forums  store  


Quick Menu
Forums           
Articles          
Galleries        
Boat Reviews  
Classifieds     
Search SailNet 
Boat Search (new)

Shop the
SailNet Store
Anchor Locker
Boatbuilding & Repair
Charts
Clothing
Electrical
Electronics
Engine
Hatches and Portlights
Interior And Galley
Maintenance
Marine Electronics
Navigation
Other Items
Plumbing and Pumps
Rigging
Safety
Sailing Hardware
Trailer & Watersports
Clearance Items

Advertise Here






Go Back   SailNet Community > On Board > Gear & Maintenance
 Not a Member? 
  #1  
Old 11-23-2008
Talisman66's Avatar
Member
 
Join Date: Jul 2007
Location: Racine on the lake
Posts: 58
Thanks: 0
Thanked 0 Times in 0 Posts
Rep Power: 8
Talisman66 is on a distinguished road
Mast, spreader, shroud design, help

Hello community, I have searched for information on this topic throughout sailnet. Read many great rigging articles.

Firsts my boat. August 2007 I bought a 1979 SJ built Morgan 45 masthead sloop rig. The standing rigging is not original to the boat. It was installed in 2003. I have unstepped the mast to inspect it and take some measurements. The "I" dimesion is 50'6". single spreader system.

Second, the situation. Looking up the shroud from the chainplate, the spreaders are pitched forward of the mast centerline thus making the shroud pitch forward to the spreader and then back to center at the masthead. I asked the surveyor about that and he had no answer as to why, or if it was engineered right or wrong. Swapping the spreaders side to side will not change the forward pitch unless I flip them over but the spreaders are asymetrical teardrop shaped extruded aluminum. If this rig is from another boat I can understand if the re-install wasn't thought out completely. The masthead and the chainplate are in the centerline of the mast. It just seems odd that the shoud has 2 conflicting angles to it. The mast currently had zero degrees of rake. The spreader is 45 inches long with 2 degrees of forward pitch. the steel rod shows the line from the mast center to the shroud center.

Third my question. Should spreaders ever pitch forward? Since the masthead and chainplate are in the mast centerline, should the spreader be at that same centerline giving the shroud a flat plane?

Forth, my plan. My plan is to cut the spreader mounting plate out of the spreader teardrop extrusion and correct the angle to zero pitch, then, set the correct bisecting shroud angle and reweld it. Results in the spreader and shroud in the centerline plane of the mast.

Any information or books on rigging desing do's and don'ts ?
Attached Thumbnails
Mast, spreader, shroud design, help-sailboatspreader.jpg   Mast, spreader, shroud design, help-sailboat-dwga.jpg  
Reply With Quote Quick reply to this message Share with Facebook
  #2  
Old 11-23-2008
sailingdog's Avatar
Telstar 28
 
Join Date: Mar 2006
Location: New England
Posts: 43,291
Thanks: 0
Thanked 11 Times in 11 Posts
Rep Power: 13
sailingdog is just really nice sailingdog is just really nice sailingdog is just really nice sailingdog is just really nice sailingdog is just really nice
You'll probably want to consult with a professional rigger or marine architect, but having the spreader tips out of a straight line between the chainplate and the mast tangs strikes me as being a bad idea. The tension on the spreader isn't just in compression then, it is also torsional, and most spreaders aren't going to tolerate that well. The shroud, ideally, should be a straight line when viewed from the outboard side looking in.

Is the mast original to the boat? If not, you might want to find out what the original mast and spreaders setup for your boat, as originally designed, looked like.

A good book on rigging is Brion Toss's The Complete Riggers Apprentice.
__________________
Sailingdog

To view links or images in signatures your post count must be 10 or greater. You currently have 0 posts.

Telstar 28
New England

You know what the first rule of sailing is? ...Love. You can learn all the math in the 'verse, but you take
a boat to the sea you don't love, she'll shake you off just as sure as the turning of the worlds. Love keeps
her going when she oughta fall down, tells you she's hurting 'fore she keens. Makes her a home.

—Cpt. Mal Reynolds, Serenity (edited)

If you're new to the Sailnet Forums... please read this
To view links or images in signatures your post count must be 10 or greater. You currently have 0 posts.
.

Still—DON'T READ THAT POST AGAIN.
Reply With Quote Quick reply to this message Share with Facebook
Reply

Quick Reply
Message:
Options

By choosing to post the reply above you agree to the rules you agreed to when joining Sailnet.
Click Here to view those rules.

Register Now

In order to be able to post messages on the SailNet Community forums, you must first register.
Please enter your desired user name, your email address and other required details in the form below.
Please note: After entering 3 characters a list of Usernames already in use will appear and the list will disappear once a valid Username is entered.
User Name:
Password
Please enter a password for your user account. Note that passwords are case-sensitive.
Password:
Confirm Password:
Email Address
Please enter a valid email address for yourself.
Email Address:

Log-in

Human Verification

In order to verify that you are a human and not a spam bot, please enter the answer into the following box below based on the instructions contained in the graphic.




Currently Active Users Viewing This Thread: 1 (0 members and 1 guests)
 
Thread Tools

 
Posting Rules
You may post new threads
You may post replies
You may post attachments
You may edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is On


Similar Threads
Thread Thread Starter Forum Replies Last Post
Updated Offshore Cruising Boat List - January 2008 sab30 Boat Review and Purchase Forum 182 09-23-2014 11:48 PM
THE Yacht Builder List T37Chef Boat Review and Purchase Forum 26 07-08-2011 06:51 AM
Mast types...? Through deck on deck...? marinesniper General Discussion (sailing related) 41 02-02-2007 10:15 AM
Small Boat Mast Stepping SailNet Gear and Maintenance Articles 0 06-12-2002 09:00 PM


All times are GMT -4. The time now is 05:06 AM.

Add to My Yahoo!         
Powered by vBulletin® Version 3.8.7
Copyright ©2000 - 2014, vBulletin Solutions, Inc.
SEO by vBSEO 3.6.1
(c) Marine.com LLC 2000-2012

The SailNet.com store is owned and operated by a company independent of the SailNet.com forum. You are now leaving the SailNet forum. Click OK to continue or Cancel to return to the SailNet forum.