Hobie Cat Forums

It is currently Thu Nov 27, 2014 12:09 am

All times are UTC - 8 hours [ DST ]




Post new topic Reply to topic  [ 4 posts ] 
Author Message
 Post subject: Spreader bar rake
PostPosted: Sat May 15, 2010 6:31 pm 
Offline
Site Rank - Captain

Joined: Sat Nov 04, 2006 12:03 pm
Posts: 52
Location: Tucson, Arizona
Out of curiosity I decided to measured the rake of the spreader bars on the mast and it's 1"5/8". The assembly manual recommends 3".

I've never adjusted the spreader bar rake since buying the boat and I've had it 6yrs. Hopefully this hasn't hurt the mast.

My inclination is to leave the rake as is.

For what it's worth, I set the tension in the diamond wire to 520lb and leave it at that for a season.

Should I set the rake to 3" as the assembly manual recommends? Thanks,

Abraham


Top
 Profile  
 
 Post subject: Re: Spreader bar rake
PostPosted: Mon May 17, 2010 5:09 pm 
Offline
Site Admin

Joined: Tue May 27, 2003 12:44 pm
Posts: 9226
Location: Oceanside, California
You refering to the Bob Curry tuning info at the back?

http://static.hobiecat.com/2010_archive/support/pdfs/H20Manual.pdf

_________________
Matt Miller
Director of Parts and Accessory Sales
Hobie Cat USA


Top
 Profile  
 
 Post subject: Re: Spreader bar rake
PostPosted: Tue May 18, 2010 8:52 am 
Offline
Site Rank - Old Salt

Joined: Sat Jul 02, 2005 9:47 pm
Posts: 589
Location: San Diego
I seem to recall someone sailing with the spreaders raked forward on a Hobie 18 at a national's qualifier event. Is this why you refered him to another source for the information? :wink:

I wonder who the boneheads were that assembled that boat? :roll:

I think we should blame it on Floyde.


Top
 Profile  
 
 Post subject: Re: Spreader bar rake
PostPosted: Tue May 18, 2010 3:47 pm 
Offline
Site Rank - Captain

Joined: Thu Aug 24, 2006 11:24 am
Posts: 81
In the Hobie 20 Assembly Manual page 5: 3" Recommended Spreader Rake, & 1" Mast Pre Bend

In the Bob Curry Hobie Cat 20 Tuning Guide (at the end of the Hobie 20 Assembly Manual)
Spreader Sweep 1" to 2 1/2" , Diamond Tension: 600 to 950 (max power to max de-power)

At Havasu last November, most were running about 4" with loose tension for very light winds ~ 1 3/8" prebend
(I surveyed most of division 3 sailors including Tim Parsons, Mark Zimmer, George Pedrick, Rafi Yalholm and had Tim check my rig)

For heavy winds and seas in Santa Cruz kick off this year after talking with Tim, I set it to be about 1 1/2 to 1 5/8 rake with heavy tension to get about 1 3/8" prebend.
I don't have a gauge to determine the tension yet and I am trying to learn which setting is best.
Tim even adjusts his diamond wire tension on the water depending upon wind conditions. I know he and Mark Lewis did a series of 2 boat tune ups to play with rake and tension.

Here is what I found on the internet:

Spreader rake
Spreader rake is a method of tuning the fore-aft stiffness of a mast below the hound fitting. Crew weight affects the required amount of spreader rake as it has a significant effect on the amount power developed by the rig.To answer how much is sufficient rake can only be determined by sailing the boat and knowing what to look for.
If you have excellent height up wind, but lack boat speed and the boat won’t accelerate in the wind gusts,
then you need more rake. This helps the mast bend fore and aft which allows the sail to flatten and the
leech to open in the wind gusts. (Also see notes on diamond tension.)

If you are lacking height and "grunt" in light to medium weather, then you have too much spreader rake.

The spreader rake is measured by placing a straight edge or string-line between the diamond wires at the
spreaders and measure the distance to the back of the mast.

Settings depend heavily on the weight of the crew, with heavier crews generally carrying less rake than lighter crews.

Diamond tension
The tension on the diamond wires primarily controls the side bends of your mast. Upwind loose diamonds allow the middle of the mast to bend to leeward and the top of the mast to hook to windward. This tends to cause the boat to heel very easily in wind gusts. Generally speaking, diamond tension is a way of powering or depowering your rig. Wind the tension on to depower and wind them off to power up.

_________________
Dwight Manning
Hobie 20 #916 San Jose CA 2000 Alter Cup boat
Hobie 18 #916 Santa Cruz CA 1989 Worlds Boat
Hobie 16 #16 San Jose CA (Jordan) 2005 Custom Main
Hobie 16 #54466 Calling Lake Alta Tequila sunrise


Top
 Profile  
 
Display posts from previous:  Sort by  
Post new topic Reply to topic  [ 4 posts ] 

All times are UTC - 8 hours [ DST ]


Who is online

Users browsing this forum: No registered users and 1 guest


You cannot post new topics in this forum
You cannot reply to topics in this forum
You cannot edit your posts in this forum
You cannot delete your posts in this forum

Search for:
Jump to:  
cron
Powered by phpBB® Forum Software © phpBB Group