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Old 07-10-2005, 18:06   #1
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Rigging Question

Hey folks, I have a rigging question for you. I have a Cheoy Lee Offshore 41 Ketch. I am changing a few things around to accomodate a decent dodger setup and a nice Bimini. I have moved my main sheet travelor from the cockpit to the cabin top so I can have a good sized dodger. I am also raising my mizzen boom by 13" so it clears my head, I am 5' 10". I am also replacing all of the standing rigging. Now my first thought was to just raise the boom, recut the sail at the head and the foot to accomodate this change. Now my second thought (which I think is better) is to just raise the whole damn mast by 13" by just adding a section to the base of the mast and leave the sail area alone. I am not really all that concerned with how I might change the characteristics of the boat since I am not touching the main or the jib and let's face it, a mizzen is a mizzen and really is not a performance sail.

Thoughts??
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Old 07-10-2005, 21:48   #2
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Sounds scarey to me, but I suppose it would work. Might make the boat a bit tender, and also could potentially add some lee helm. As far as the rig design, many ketchs are rigged with tall mizzens. It will likely change the balance of the boat under sail by changing the combined sail shape.
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Old 08-10-2005, 00:13   #3
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could potentially add some lee helm.
I understand your concern but I am not moving the center of effort for or aft just up. As far as being "tender", this is one of those boats which has a history of being just the opposite - she is very stable with a deep draft. I really can't think of a reason not to do this but I am open to more suggestions.

Thanks for the input.
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Old 08-10-2005, 00:22   #4
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What I am thinking is that if the mizzen is moved higher, the aft area of your total sail area will be higher. Just a theory, but I did notice additional lee helm on my ketch when I went to a mizzen with more roach. I found that I had to ease the mizzen noticably more to balance the boat.
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Old 08-10-2005, 02:44   #5
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Have you considered the stresses involved with the main sheet traveller on the roof. I would certainly consider addidtional support , after all it would be a bit embarassing in the middle of a storm to suddenly lose your cabin top!
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Old 08-10-2005, 04:42   #6
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BI, raise the boom and recut the sail. Raising the mast incurs permanent changes (longer shrouds, a new mast base) and must be structurally beyond question. Raising the boom means making temporary changes that can later be reversed, if you wish. Perhaps a better compromise for you is to mount your mizzen gooseneck on a short length of genoa track which in turn mounts on the mast. Our 11T, 13M ketch, a Pearson 424, was delivered with this arrangement and offers flexibility.

Jack
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Old 08-10-2005, 05:17   #7
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Iím neither an engineer (By Invitation IS) nor a mathematician - but it seems to me that the centre of effort is a vector of the forces on the sails & hull etc.
In moving the mizzen up (lengthened mast), thereby moving itís centre of effort up, you might be moving the overall centre of effort in two planes (height & fore/aft).

Can one of our engineering/mathematical types calculate the vector (change)?
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Old 08-10-2005, 06:27   #8
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In moving the mizzen up (lengthened mast), thereby moving itís centre of effort up, you might be moving the overall centre of effort in two planes (height & fore/aft).
Good point Gordmay, this is why I posted this before I do anything. Keep the suggestions coming, I need to have some kind of reasonable solution to this "low" mizzen boom. If I don't move it up, I lose a bimini and will most likely loose my head one day when I get clocked by it. It's normal height is ear level.
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Old 08-10-2005, 06:36   #9
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Have you considered the stresses involved with the main sheet traveller on the roof. I would certainly consider addidtional support , after all it would be a bit embarassing in the middle of a storm to suddenly lose your cabin top!
Thanks Talbot for the concern but I have taken care of this quite substantially. My traveller is not going anywhere and neither is my cabin top. I have a couple of friends with the same boat who have paid a yard to make this change and my setup is much more substantial than their's. The Garhaur travellor is almost twice the size and the mounts are as well. By the end of next week I will have photo's and I will post them so you can see what I have done.

Harken makes mounts which look like a car roof rack for this same change. I didn't trust this setup and many boats have them. I fiberglassed blocks onto the cabin top which spread the load and use 4 bolts spread out across about 16" on each side through bolted to a backing plate. This thing ain't moving!
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Old 08-10-2005, 09:52   #10
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Folks, raising the CE of a mizzen by 13" on a CL Offshore 41 is going to have no meaningful effect on the boat. (Much counting of angels on the head of a pin...) If the influence on overall CE and sailing performance are concerns, let's start with the impact of adding a bimini and dodger (which rarely receives the consideration it deserves, ditto with weathercloths, solar panels, jug farms, dink on davits, et al.)

Jack
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Old 08-10-2005, 11:02   #11
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Hi Scott,

Go for it.

I posted my explanation on "the other side"
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Old 08-10-2005, 14:20   #12
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By Invitation

I also wish to raise the missen boom on my CT41 but by 18 inches, I've been looing at the missen all summer trying to find a solution that will not break the bank.

Euro cruisrs sugestion looks good, leave the mast as is then put the gooseneck on a short genoa track to raise the boom. This would then decrease the sail area and add lee helm. To compensate, would a new, larger roached sail with a full batten at the top offset the lost sail area ???? Will have to take my sail maker out to dinner and ply him with beer.

I am a bit concerned with increasing the deck to boom distance and the pumping effect of the boom in heavy seas or extream sailing conditions.

Any thoughts?
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Old 08-10-2005, 15:15   #13
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Ctrich,

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I am a bit concerned with increasing the deck to boom distance and the pumping effect of the boom in heavy seas or extream sailing conditions.
Never thought of this possibility - thanks. I wouldn't think that 13" would really make a big difference with the pumping problem. If it's going to pump, it's going to pump and I don't think it would be that much worse for such a short distance change.

I will try to look into this further.
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Old 08-10-2005, 15:18   #14
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Ctrich (and the group):

You're asking three different questions...but first, for your boat (CT 41) don't overlook the fact that the genoa track attachment needs to be at least as strong as the mizzen's gooseneck if indeed you are worried about 'extreme sailing conditions'. Typically, this means the gooseneck assembly needs to be welded substantially onto a car that rides on the track, which in turn is mounted to the spar. In my case, my mizzen is only 100 sq. ft., perhaps 65 sq. ft. when reefed. That can generate a lot of 'umph!' in a heavy blow but in reality it doesn't require a massive gooseneck nor track attachment. Your boat is I believe different, with more sail area in the mizzen...so look carefully at the track attachment issue if you really do anticipate heavy weather.

Re: your first Q, I'm assuming you will lose about 10 sq. ft. of sail area if raising the boom...and on a sail that you may not even use on certain points of sail. (I multiplied 13" x 10' of mizzen boom; if the boom is 12', it would be 12 sq. ft. - in truth, not much). Change in CE would be irrelevant. So...how significant is losing 10+ sq. ft. of a sail back aft, when the whole sail gives you zero drive to weather, little drive on a close reach, and where you should be looking to sail changes (adding a mizzen staysail) in light-medium winds from a beam reach on up? Can we not assume it matters little? Can we give up on the idea of a new $$$ main with a fuller roach? Given your boat's HUGE wetted surface, you are not going to miss 10 sq. ft. from that mizzen, IMO - save the dinner & beer for your sweetie, not the sailmaker.

Q2: Should you be concerned about increasing the distance between deck & boom. I sure would think so, as that CT 41 cockpit has you out there working without a net, dancing around in a blow while trying to tie in a reef. The last thing you want to do is impersonate a ballet dancer, on your tippy toes, while tying in a reef while a big swell is running. If you can't comfortably, securely reef the mizzen at the boom's new, higher height, then release tension on the halyard, pull the pin in the track on which the boom rides, and drop the boom so you can better reef the sail. You want to insure you have stout fixed stop at the bottom of the track (not one of those plastic track stops); in heavy conditions, this would be harder to do than to describe.

Q3: Added pumping in heavy seas? I doubt you'll find any meaningful changes from a *smaller* sail that you then raised 13" but otherwise made no changes to? It sounds like your expecting substantial change to result from a relatively miniscule change in sail plan.

Where is this heavy weather going to be found? Where are you and what are your sailing plans?

Jack
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Old 09-10-2005, 07:37   #15
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Jack,

Thanks for all the information - you have made some really good points here. I will take all of them into consideration before I decide which way I am going to go.
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