Return to Hobie.com
Hobie Forums
It is currently Tue Oct 27, 2020 10:20 pm

All times are UTC - 8 hours [ DST ]




Post new topic Reply to topic  [ 5 posts ] 
Author Message
 Post subject: aussie mast rake specs
PostPosted: Wed Oct 14, 2020 6:31 pm 
Offline
Site Rank - Captain

Joined: Fri Jan 23, 2009 9:12 am
Posts: 27
Several weeks ago one of our forum members mentioned that the aussies are using much more mast rake on their H18s and that it improves performance somewhat. I am familiar with mast rake measures from mast to tang (max 107") suggested in the hobie 18 performance manual(Berman) but, have any of you come upon specific measurements used by the aussies? Wishing to experiment>>>>Deejay Thanks


Top
 Profile  
 
PostPosted: Thu Oct 15, 2020 6:14 am 
Offline
Site Rank - Old Salt

Joined: Mon May 09, 2005 10:25 am
Posts: 3915
Location: Jersey Shore
Do you have low profile main blocks? If not, you probably won’t be able to rake back that far.

sm


Top
 Profile  
 
PostPosted: Sat Oct 17, 2020 3:22 am 
Offline
Site Rank - Captain

Joined: Sat Aug 18, 2018 4:06 pm
Posts: 113
Location: Sydney, Australia
Hi guys. I am the Aussie with the mast rake. You do not need low profile blocks. In fact I have a strop on my mainsheet system.

The way we measure the mast rake is with using the trapeze wire extended forward to the bridle tang and aft along the gunwale.

I have posted numerous photos on my boats Facebook page of how to measure this and where my mast rake measurement is. It has a dedicated photo album on my boats Facebook page. Remember to “See All” so you can see the various photo albums. See link in my footer below. I’m willing to share everything so let me know if you need any more information after you have viewed the photos (or if you don’t have Facebook. My page is public).

Please see Facebook photos before reading on.

- rig tension on
- mast rotation to be fore-aft
- no sails hoisted
- Boat on flat level ground
- add 1’ length of rope to trapeze ring dogbone
- measure and mark the length where the rope extension touches the bridle clevis pin
- walk the trap wire aft along the boat until it touches the gunwale. It will generally touch the gunwale around the rear beam area. In strong wind it will generally touch the gunwale aft of the rear beam.
- however, with my boat, I have it raked so far aft that it reaches aft of the rear end of the gunwale and we then measure it touching about 1-2” down the transom.
- to achieve this you will need a longer forestay. The convenient way to add length is to simply make a longer top forestay from the hound shackle to the swivel fitting.
- the more you rake the mast back, the more you must slide forward the jib cleat cars in the track.
- be mindful that with maximum rake you may also need a new jib spreader patch higher up to protect the jib.
- the more you rake the mast back, the more you need to tuck your rudders under to balance the helm.

Enjoy.

_________________
John Forbes
Hobie 18 Reimagined
Sail # 490
Boat name: [email protected]
http://www.hobie18.fun
https://www.facebook.com/Hobie18catamaran/


Top
 Profile  
 
PostPosted: Mon Oct 19, 2020 7:35 pm 
Offline
Site Rank - Captain

Joined: Sun Feb 22, 2015 8:27 pm
Posts: 125
Location: FL
An H18 already has too much weather helm when sheeted hard and raking the rudders doesn't change the drag from the excessive angle of attack needed to keep the boat on target. It just makes it easier on your arm by moving more of the rudder surface in front of the axle line where the water flow eases the force needed to hold the rudders off center.

I always run my rake as far forward as possible until probably 15+ knots when the bows digging at full speed downwind becomes an issue and then I take it the mast back a few holes on the plate.

Maybe if these old mainsails didnt stretch so much it would be possible to effectively flatten them and move the sail balance forward more to kill the helm. The ability to change the sail shape is pretty limited. On shore yea I can do some stuff but once there is pressure in the sail it's back to having too much camber.

I think having a reef point might be good in moving the sail balance where I'd want it in heavier air.

I'd have to see some very controlled experiments to believe that heavy rake makes an overall improvement in all conditions. It wouldn't on my boat and how I sail. Differences in helm style and consistency, weight balance, sail age, sheeting tension, etc could make enough of a difference to create a false result here.

_________________
'82 NACRA 18 Square "Bangarang"
'85 Hobie 18 "Honey Badger Don't Care"
'86 Hobie 18 "The Rippin & The Tearin"
'07 Bimare XJ A-Class


Top
 Profile  
 
PostPosted: Tue Oct 20, 2020 9:28 am 
Offline
Site Rank - Captain

Joined: Fri Jan 23, 2009 9:12 am
Posts: 27
John Forbes and TAMUmpower Thanks for both your replys, very interesting thoughts on mast rake......DJ


Top
 Profile  
 
Display posts from previous:  Sort by  
Post new topic Reply to topic  [ 5 posts ] 

All times are UTC - 8 hours [ DST ]


Who is online

Users browsing this forum: No registered users and 2 guests


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:  
© Hobie Cat Company. All rights reserved.
Powered by phpBB® Forum Software © phpBB Group