Boom vang block selection - SailNet Community
 
LinkBack Thread Tools
post #1 of 7 Old 02-20-2008 Thread Starter
Sea Slacker
 
Join Date: Jan 2007
Posts: 1,789
Thanks: 0
Thanked 0 Times in 0 Posts
Rep Power: 11
 
Boom vang block selection

I am replacing some antique boom vang blocks and need to select the new ones. How would I estimate the working load for the vang on a 35' boat?

Schaefer series 5 is in stock at Defender and fits my selected line size (7/16" - just like my halyards) - but I have no idea if 1800lbs of working load is enough. Sure sounds like "a lot" but then Scahefer says these blocks are "for boats up to 28'" - then again, depends on application I suppose?
brak is offline  
Quote Quick Reply Share with Facebook
Sponsored Links
Advertisement
 
post #2 of 7 Old 02-20-2008
Telstar 28
 
sailingdog's Avatar
 
Join Date: Mar 2006
Location: New England
Posts: 43,290
Thanks: 0
Thanked 18 Times in 14 Posts
Rep Power: 16
         
Might want to contact Garhauer Marine. They make some really nice gear at very reasonable prices.

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.
sailingdog is offline  
Quote Quick Reply Share with Facebook
post #3 of 7 Old 02-20-2008
Senior Member
 
Join Date: Jun 2005
Location: New Orleans
Posts: 2,162
Thanks: 10
Thanked 49 Times in 46 Posts
Rep Power: 12
 
Wow.

I have absolutely no idea, though it's perfectly good question. I'd say offhand, as long as it looks as though it can take twice the load of your mainsheet, it's probably okay. Keep in mind that the vang probably takes as much load as any other piece of running rigging on your boat, and plan accordingly...
nolatom is offline  
Quote Quick Reply Share with Facebook
 
post #4 of 7 Old 02-20-2008 Thread Starter
Sea Slacker
 
Join Date: Jan 2007
Posts: 1,789
Thanks: 0
Thanked 0 Times in 0 Posts
Rep Power: 11
 
Hm, didn't think about that - somehow I thought vang is less loaded, because it has shorter arm of force operating against it - but then again, that may mean less leverage, so may be it is more.

My personal preference is for Ronstan blocks, but the appropriate series aren't in stock at Defender and I don't really have time to go looking around. It would be great to figure out at least a ballpark load for this application.
brak is offline  
Quote Quick Reply Share with Facebook
post #5 of 7 Old 02-20-2008
Barkeep - Sailor's Pub
 
craigtoo's Avatar
 
Join Date: Aug 2007
Location: Magothy River, MD
Posts: 1,946
Thanks: 0
Thanked 0 Times in 0 Posts
Rep Power: 11
   
Send a message via AIM to craigtoo Send a message via Yahoo to craigtoo Send a message via Skype™ to craigtoo
Quote:
Originally Posted by brak View Post
I am replacing some antique boom vang blocks and need to select the new ones. How would I estimate the working load for the vang on a 35' boat?

Schaefer series 5 is in stock at Defender and fits my selected line size (7/16" - just like my halyards) - but I have no idea if 1800lbs of working load is enough. Sure sounds like "a lot" but then Scahefer says these blocks are "for boats up to 28'" - then again, depends on application I suppose?
I asked the rigging guys at West this same question... I had to replace the vang on my boat as well....

They asked about the square footage of the mainsail, the length of the boom and where the attachment points were. He used that to determine which blocks / mechanical advantage system would work the best.

An 8:1 system can impart alot more force to the attachment points, so I had to take that into consideration as well and refit as necessary. I ended up with 7/16 system for a 34' boat.

I'm sorry I can't provide the "square-footage vs. force needed" stats.

Hope this helps,
Craig

-C2
1987 Sabre 34 "Saoirse"
Meet me at the
To view links or images in signatures your post count must be 10 or greater. You currently have 0 posts.



I love
To view links or images in signatures your post count must be 10 or greater. You currently have 0 posts.
craigtoo is offline  
Quote Quick Reply Share with Facebook
post #6 of 7 Old 02-20-2008
Once known as Hartley18
 
Classic30's Avatar
 
Join Date: Aug 2007
Location: Melbourne, Australia
Posts: 5,179
Thanks: 52
Thanked 85 Times in 85 Posts
Rep Power: 11
   
Dock
Quote:
Originally Posted by brak View Post
I am replacing some antique boom vang blocks and need to select the new ones. How would I estimate the working load for the vang on a 35' boat?
If you're replacing them, I'd suggest selecting blocks of about the same physical size and, given modern construction methods make blocks a bit stronger than they used to be, you'll be fine.

The important thing is to not go too small... an exploding vang block would not be a pretty sight. In fact you wouldn't want to be anywhere near it!

Have you considered one of the new-fangled ram setups?

-
A bad day on a boat beats a good day in the office
Classic30 is offline  
Quote Quick Reply Share with Facebook
post #7 of 7 Old 02-20-2008 Thread Starter
Sea Slacker
 
Join Date: Jan 2007
Posts: 1,789
Thanks: 0
Thanked 0 Times in 0 Posts
Rep Power: 11
 
I am trying not to change too much - rigid vang would be nice but I need to sail more before I figure what I want from the rig. I might replace the entire boom at some point anyway.

Original blocks are a bad guide in my case - one is well over 35 y/o - who knows how strong it is. Another is a Schaefer, looks like series 5. I like them, they look very shiplike, and feel solid - but their specs are marginal, 1800lbs SWL.

I just ordered a pre-made Garhauer vang set - it includes both blocks and a line, so its at least $100 less than me buying those things separately. Plus, their blocks have SWL of 2800lbs which sounds about right. They are "modern style" which to me means - ugly, and won't look right on my boat, but I guess I'd rather select function over form.

I found a sort of a guide somwhere on the net, that suggests assuming for wind of up to 20kts about 1.5lbs per sq. ft. of mainsail for fittings on the end of the boom, and 3lbs per sq. ft. for mid-boom fittings. Continuing this further a fitting 1/4 way from the mast, like a vang, would experience double the load at 6lbs / sq. ft. of main. My main is about 230-240 sq.ft. which makes the load in a ballpark of 1400-1500lbs. It goes up as a square of wind force (but then again, I'd be reefing by 20 kts, reducing the sail size). So, Schaefer is marginal and Garhauer is more than enough.

Other manufacturers (Harken, Lewmar) have blocks that look even more "modern" (can't look at those things without squinting) and more expensive.

So that's my research for the day.
brak is offline  
Quote Quick Reply 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:
OR

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
Show Printable Version Show Printable Version
Email this Page Email this Page



Similar Threads
Thread Thread Starter Forum Replies Last Post
Deadly Serious about Booms John Rousmaniere Seamanship Articles 0 10-12-2004 08:00 PM
Boom Vangs SailNet Racing Articles 0 10-04-2000 08:00 PM

Posting Rules  
You may post new threads
You may 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 On
Trackbacks are On
Pingbacks are On
Refbacks are On

 
For the best viewing experience please update your browser to Google Chrome