SC31 Mast Rake & Bend Specs Available?

[lavery]

Sailors,
Can anyone point me toward manufacturers specifications for mast rake and bend for the Southern Cross 31?

Also, how about what works for you?

My mast appears to have negative rake (i.e. it leans forward). The forestay appears to be not long enough to let the mast settle back.

Regarding bend, I'd like to know if mast bend is a common practice on this boat, and if so, how much.

Thank you all,

Jim Lavery
SC31 Hoku Kea

[Brian Duff]

The mast was not designed raking forward, but rather aft. The bend is 100% a function of the mainsail cut, not any design consideration (at least on 95%+ of the designs out there, the masts were not designed with bend it seems)

So, the real question is, how does your boat sail? How is the shape of the main? If you have balance problems when only minimally heeled, or if your main is a deep bag with the max depth in the middle, you might need to make changes.

[lavery]

Brian,
Thanks for your adjustment guidelines. I will try them out when I get the mast back on. Yes I agree this mast is probably not designed for bend.

At the moment, I have cut into the cabin-top because of dishing under the mast. The original plywood core is soft and wet, so repairs are underway. Also, my rigger says the mast pedestal is not original so this may explain too-short forward stay. Original specs would be great to have.

Much to do before adjusting and testing rake.

Thanks,

Jim Lavery
Hoku Ke'a
Southern Cross 31

[Brion Toss]

Hi,
As you'll see at http://www.southerncross-boats.org/images/sc39-plan.gif, the original sailplan has a fair amount of rake. Print it out to get a ruler on it.
Too short a stay can mean trouble at the mast step; be careful.
Fair leads,
Brion Toss

[lavery]

Brion,
Thank you for finding this graphic and bringing my attention back to the forestay.

Under my mast was a block of wood about 1" to 1-1/2" thick, nicely faired and finished but weathered and cracked, that I assumed was original. The guy helping me with the repair says not so. If this was added it may account for the short forestay.

I do not see a raised step under the mast on the graphic.

Please confirm if raising the mast by this 1” to 1-1/2" can result in the kind of problem I am seeing at the forestay. If so I need a reference dimension to be able to determine mast step height.

In your opinion, can I get enough resolution off the sailplan printed on 8-1/2 x 11, to determine the required height of the mast step within 1”?

Thanks,


Jim Lavery
s/v Hoku Ke'a
Southern Cross 31

[Clyde Jenkins]

The posted sailplan was for the SC39. Try this link
http://www.southerncross-boats.org/i...31-profile.gif

You'll have to print it out to get some idea of the mast rake. I can't tell how much there is from my computer screen.

Clyde

[lavery]

Clyde,
Thanks for the SC31 graphic. I think that once I get my mast step repaired and solve the question of a too-short forestay, I will be able to set in a rake as a starting point that is reasonably close to the graphic, probably somewhere in the 1 to 2 degree range.

Thanks,

Jim Lavery
s/v Hoku Ke'a
Southern Cross 31