mast sizing? - 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 > General Interest > General Discussion (sailing related)
 Not a Member? 


Reply
 
LinkBack Thread Tools
  #1  
Old 09-21-2010
Junior Member
 
Join Date: Sep 2010
Posts: 9
Thanks: 0
Thanked 0 Times in 0 Posts
Rep Power: 0
PlPhillips is on a distinguished road
Smile mast sizing?

hello
thanks to all who lookd at and helped with the triandle 20. now it is time to think about puting this thing togher. can any one tell me weather it is best to size the mast by boat lenght or displacement? and how ? she is 20' and displaces 2,300 lbs.
thanks
paul
Reply With Quote Share with Facebook
  #2  
Old 09-21-2010
SlowButSteady's Avatar
Senior Slacker
 
Join Date: Feb 2010
Location: SoCal
Posts: 4,223
Thanks: 0
Thanked 17 Times in 15 Posts
Rep Power: 5
SlowButSteady is on a distinguished road
The fancy answer is to calculate sail areas, lever arms, righting moments, etc., etc. But, as a general rule, boats of this size have masts a little longer (10-15%) than one boat length.
Reply With Quote Share with Facebook
  #3  
Old 09-21-2010
okawbow's Avatar
Senior Member
 
Join Date: Feb 2007
Location: Illinois
Posts: 220
Thanks: 0
Thanked 3 Times in 3 Posts
Rep Power: 8
okawbow is on a distinguished road
mast size

Quote:
Originally Posted by PlPhillips View Post
hello
thanks to all who lookd at and helped with the triandle 20. now it is time to think about puting this thing togher. can any one tell me weather it is best to size the mast by boat lenght or displacement? and how ? she is 20' and displaces 2,300 lbs.
thanks
paul
I have a bristol 19 that is 19'6" long, and displaces about 2700# with a 2'11" draft. The mast is 26' tall. It used a Kenyon "D" mast section. (same as a Cape Dory Typhoon.) I would think you could use that as a guide, depending on your keel depth and weight. It would also depend on where you sail. For inland lakes, a tall mast is good. For San fransisco bay, a shorter mast would be wise.
__________________


Chuck
Privateer 26 Schooner
Reply With Quote Share with Facebook
  #4  
Old 09-22-2010
SlowButSteady's Avatar
Senior Slacker
 
Join Date: Feb 2010
Location: SoCal
Posts: 4,223
Thanks: 0
Thanked 17 Times in 15 Posts
Rep Power: 5
SlowButSteady is on a distinguished road
Quote:
Originally Posted by okawbow View Post
I have a bristol 19 that is 19'6" long, and displaces about 2700# with a 2'11" draft. The mast is 26' tall. It used a Kenyon "D" mast section. (same as a Cape Dory Typhoon.) I would think you could use that as a guide, depending on your keel depth and weight. It would also depend on where you sail. For inland lakes, a tall mast is good. For San fransisco bay, a shorter mast would be wise.

At first 26' sounded really tall, until I realized that a Bristol 19 is a fractional rig. The rule of thumb I used in my earlier post was for masthead rigs. A fractional rig will probably be another 10-15% or so; in other words, the mast would be a boat length plus 20-30%. With that shallow a keel, I wouldn't use a mast too much more that a boat length, however. Also, keep in mind that a shorter mast will be easier to raise/lower and transport.
Reply With Quote Share with Facebook
  #5  
Old 09-22-2010
okawbow's Avatar
Senior Member
 
Join Date: Feb 2007
Location: Illinois
Posts: 220
Thanks: 0
Thanked 3 Times in 3 Posts
Rep Power: 8
okawbow is on a distinguished road
I looked up the triangle 20, and using their picture, it looks like they used about a 24 1/2' mast. Their rig is a fractional, with a small headsail. You can print out a picture and compare the known length of the hull with the mast, to get close to the right length.
TRIANGLE 20 Sailboat details on sailboatdata.com
__________________


Chuck
Privateer 26 Schooner
Reply With Quote Share with Facebook
  #6  
Old 09-22-2010
Jeff_H's Avatar
Moderator
 
Join Date: Feb 2000
Location: Annapolis, Md
Posts: 6,538
Thanks: 5
Thanked 85 Times in 65 Posts
Rep Power: 10
Jeff_H has a spectacular aura about Jeff_H has a spectacular aura about Jeff_H has a spectacular aura about
Assuming that the drawing that you linked to is drawn correctly to scale (which it appears to be), then the mast appears to be 27 feet 6 inches from the top of cabin to the top of mast. In terms of spar section and detailing, you really should not wing it, even on small boat (too heavy a spar section and the boat will be tender and will not spill off the wind in a gust, and too light a spar section and it will end up over the side).

Also if you have not built a spar before, especially a fractionally rigged spar with jumper struts, you should talk to someone who has. There are critical details involved in terms of how the shrouds attach to keep the mast from twisting or crushing.

In a general sense, fractional rigs are typically 1.3 to 1.4 times the length of the boat above the waterline. Mast head rigs are more like 1.25 to 1.3 above the waterline. But of course both vary widely with each specific design.

Jeff
__________________

To view links or images in signatures your post count must be 10 or greater. You currently have 0 posts.
Curmudgeon at Large- and rhinestone in the rough, sailing my Farr 11.6 on the Chesapeake Bay and part-time purveyor of marine supplies
Reply With Quote Share with Facebook
  #7  
Old 09-23-2010
Junior Member
 
Join Date: Sep 2010
Posts: 9
Thanks: 0
Thanked 0 Times in 0 Posts
Rep Power: 0
PlPhillips is on a distinguished road
it all sounds good.
would deck height off the water line play into the height and length of the mast? I think the same size mast on 2 boats will act diferntly given a difrence in deck/cabin hight.
Reply With Quote Share with Facebook
  #8  
Old 09-23-2010
Jeff_H's Avatar
Moderator
 
Join Date: Feb 2000
Location: Annapolis, Md
Posts: 6,538
Thanks: 5
Thanked 85 Times in 65 Posts
Rep Power: 10
Jeff_H has a spectacular aura about Jeff_H has a spectacular aura about Jeff_H has a spectacular aura about
When you are designing a boat, you use rules of thumb and your objectives for the boat to set sail area, mast height and sail plan proportions. When you are dealing with an existing design, you typically want to get close to the original unless you really know what you are doing.

It occurs to me that you must still have the mast step attached to the boat. In those days, most production boats either had Dwyer or Kenyon spar sections (a few had Proctor). You should be able to carefully measure the mast step, and then go to the Dwyer or Kenyon webpages and figure out what the spar section was. The rest is pretty easy.

Jeff
__________________

To view links or images in signatures your post count must be 10 or greater. You currently have 0 posts.
Curmudgeon at Large- and rhinestone in the rough, sailing my Farr 11.6 on the Chesapeake Bay and part-time purveyor of marine supplies
Reply With Quote Share with Facebook
Reply


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
sizing a new sail svobsession Gear & Maintenance 6 02-11-2010 12:04 AM
Sizing T-terminals Newport41 Gear & Maintenance 4 01-17-2010 09:16 PM
Mast Section sizing lastconch Sailboat Design and Construction 5 11-26-2007 12:27 PM
Prop sizing GBurton Gear & Maintenance 5 10-29-2007 11:00 AM
Windlass Sizing labatt Gear & Maintenance 16 11-18-2006 10:09 PM


All times are GMT -4. The time now is 12:19 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.