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Old 11-17-2011
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Adjusting rake on a keel stepped mast

Hello everyone. I need to make a serious adjustment to the rake of my mast. I found the in the cabin where the mast sits, it has a two piece base. The first piece is a wide channel w/ about 10 holes in the sides for a through bolt to lock the mast in place. The other part sits inside the channel and is actually the piece the mast sits on. It appears to me that this piece should slide fore and aft to adjust the rake on the mast. I know I should have a pic. Forgot to take before I came home. If this sounds familiar to anyone please let me know. Don't wanna screw anything up. Otherwise, I have to cut new shims to go in between the mast base and the mast at the deck.
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Old 11-17-2011
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It's not unusual to have an adjustable mast butt like this. Adjusting it, though, pretty much requires slacking the rig off nearly completely depending on the arrangement. On ours I was able to pull a pin/bolt, then tap the bottom of the stick aft on the 'track' with a hammer and a block of wood, and then reinsert the pin at a new location.

The butt location fore and aft will be determined by the rake you want and the amount of prebend you'd like to induce. If it's essentially a straight stick, then moving the step forward will induce a fair bit of rake (remember the 'lever lengths' and consider the partners as a pivot. 6 feet inside the boat, probably 40 or more above deck.. so moving the butt one inch would move the masthead 6-7 inches in the opposite direction.)

On our boat, a fractional rig, I wanted a fair amount of prebend so I moved the butt aft a bit below; left to its own devices the mast had a slight forward lean at that point. Pulling the rig aft from there (swept spreaders) gave me both the rake and the prebend I wanted. It seems to have worked out OK.

btw on Sailboat Data I see an Elite 30 (Frac).. is that the rig you have?
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Last edited by Faster; 11-17-2011 at 08:59 PM.
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Old 11-17-2011
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Yes, you slack all the rigging a bit, then either bump the base of the mast or rig a line to haul it, pin it in the new position, and you may need to reposition the chocks or make new ones, depending on the clearance through the deck. Not unusual, and in some boats some owners adjust the rake for wind conditions from race to race. Depends on your rig and how fanatical you want to get about winning.
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Old 11-17-2011
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Awesome, thanks guys! This is exactly what I was hoping to hear, it's pretty easy. Yes Faster, that is the boat we have. I currently had achieved the prebend in proper amount, but have a tremendous amount of lee helm. Several people questioned the rake of the mast before prebend and it was just straight. Hoping this will bring my tiller to neutral or a tad bit of weather helm. Fighting to stay in the wind now. Having to do this all on my own as the marina had a complete MORON with no clue of what he was doing other than it's a boat and it floats.lol Changes come tomorrow evening when I can get back up there and get started. Luckily, the friends w/ the tension gauge will be there too. Thanks again!!!

Not racing yet, still learning. Racing next year!
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Our mast is small, only 13" in circumference. So I can only get about 4" max prebend anyway. That only leaves me 8" of travel on my backstay too. I think the rake can give the the control I need at the helm. It may look like my mast is way too far back when I am done as it tapers the top 8'down to about 6" around. I don't think I am going to need the entire 24.5" of rake being recommended which is 3ļ. We'll just have to see.
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Old 11-17-2011
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kindsail, remember that to some extent each boat is a custom rig that needs custom balancing. Even "genuine exact" sails all stretch, so if you have a 150 genoa, after two years it may stretch into a 152. Or the loft may have built it as a 146, so it wouldn't exceed 150 after a year or two of use. Same thing with the main, the dimensions change, and as they all change the sail balance will change.

And that's assuming nothing else was changed, big assumption. It may not just be the rake or bend, remember also the mast may need to be moved fore/aft a bit, if you can find out the original factory location, and assuming again they were all built very precisely, that may have been shifted "one hole" or two as well.

Of course once you take the time to go round and round and get the rig really tuned and balanced right, it will usually sail sweeter, point better, pay off your work in spades. If the builder is still around or if there is a class association, see if they have any info for you to start from. Sometimes you'll also pick up bits like "well we built them all with 24" spreaders but they point better if you take them down to 22.5" and you'd never know without asking around.
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Old 11-17-2011
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Seems to me.. aft = more weather helm and foward = less? A mast that has a channel would seem to offer all kinds of adjustment. I'd go for no bend for starters. but I'm far from any expert on this. I do (or used to) read allot.
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Old 11-18-2011
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Quote:
Originally Posted by deniseO30 View Post
Seems to me.. aft = more weather helm and foward = less? A mast that has a channel would seem to offer all kinds of adjustment. I'd go for no bend for starters. but I'm far from any expert on this. I do (or used to) read allot.
Essentially correct... after all that's how windsurfers 'steer'...

Denise.. bend in the mast can be required by the cut of the sail, ie the luff shape is intended to match a certain amount of ideal mast bend. Performance 'bendy' rigs often are set up with significant mast prebend.. the ability to adjust this bend underway allows more flexibility in flattening the main, or powering it up by managing the mast bend. (less bend to create a fuller camber, more bend to pull fabric forward and flatten the draft) In addition the prebend creates a more stable structure as the rig is somewhat stressed and less likely to pump.

Hunters B&R rig features a lighter section that is set up essentially as a truss with it's severely swept spreaders, inducing a curve in the mast at the proper tension. Sails for it would need to be cut to match.

Adjustable babystays are a rather brutal way to induce more mast bend in an attempt to flatten the sail.

Worst is an inverted bend, ie the mast bowing aft at the spreaders... this puts more cloth back into the sail creating a full draft that would not trim properly and would create a greater heeling force and early backwinding..

Boats like Cat 30s, 34s and other generally 'cruisier' boats seldom use significant mast bend. In the OP's case she's a bendy fractional rig that may well have been initially intended to have a fair amount of bend and has sails cut for that.

Overall rake is another matter and if he's suffering from lee helm then more rake will be a good start to the cure - but he likely needs to retain the bend that he has..
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Faster and Hellosailer, I have to keep my prebend for sure, and I have all that set up now from when I rigged the boat in late June at launch. Sure isn't any information around as far as the manufacturer goes. I belong to a yahoo group of Elite owners but no responses there yet. I don't think I need the recommended 24.5" of rake, even sounds extreme, and with prebend and the aft stay fully tensioned it might look like it's breaking.lol

I am going to talk to a couple of locals today and see if I can get some more info out of them before I do this, but I am confident that it's not going to be much different if any than what I did in June. I just wasn't aware of it then and went by the manufacturers instructions for the mast. Odd they didn't mention rake in their instructions. Thanks again for verifying my actions before I went and did something I shouldn't have!
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