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Go Back   SailNet Community > On Board > Gear & Maintenance
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  #51  
Old 09-24-2007
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I have a 28' boat, with a 6:1 mainsheet system, and we need every bit of it. How large is the main on your boat? Mine is about 250 sq. ft.

Quote:
Originally Posted by SEMIJim View Post
Pretty close. The sailplan calls for a 11.8' clew. I just called it 12'. The mainsheet attachment point is 4' from the end of the boom, which is about 13' long. (I did a rough measurement of the boom, w/o removing the sail cover, yesterday.)

Everything's relative. We both find the traveler to be easy to move, wherever we want, on any tack and, so far, regardless of wind strength. So maybe we ought to be relying more on that and less on the mainsheet.

We'll give a new 4:1 system a try. If it's still too much, I'll look to increasing it to a 5:1 or 6:1 system. My goodness, it's only a 30' boat. Had one experienced sailor yesterday tell me there's nothing wrong with the blocks we have, just file down the teeth in the cleat a bit, and change the angle a bit if we can.

Jim
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  #52  
Old 09-24-2007
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Quote:
Originally Posted by KeelHaulin View Post
You should be doing your calculation based on heavier wind conditions than 15kts IMHO.
Somewhere between 15 and 20 kts, we'll be putting a reef in.

Quote:
Originally Posted by KeelHaulin View Post
... and if you get into some gusting wind (gusts to 30 kts) it won't be easy to spill to reduce your heel.
If we get 30 kt gusts w/o a reef in, we've done something very wrong, IMHO. I'm not saying it couldn't happen, but it shouldn't happen.

Quote:
Originally Posted by KeelHaulin View Post
Ideally you'd want an 8:1 to cut these loads in half; but 6:1 would probably be manageable.
8:1?!?! You do realize we're talking about a 30' boat here, right?

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Originally Posted by KeelHaulin View Post
It looks like you have a windward sheeting car.
Don't know what that means, sorry.

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Originally Posted by KeelHaulin View Post
Chris is correct in stating that the traveler can be a more effective sail control than the mainsheet. Another thing to consider is sheeting the sail down flat with the mainsheet and then lowering the traveler to reduce heel. Doing this keeps the mainsail at minimum draft yet spilling power.
It seems experimentation is in order. Chris suggests not sheeting the main in quite so tight and bringing the traveler up, you suggest sheeting the main down tight and lowering the traveler.

Quote:
Originally Posted by KeelHaulin View Post
I would go to the higer range of the 30kt loads (SWL of 2500 or so).
I am never going to be trying to sail that boat in 30 kt winds with a full main. By 30 kts I should be on the 2nd reef point and have the #3 up, if anything.

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Originally Posted by KeelHaulin View Post
If you run through the compu-spec on the Pearson 30 mid-boom it kicks back...
But we don't really have mid-boom. We have 2/3 or 3/4 boom.

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Originally Posted by KeelHaulin View Post
what Giu suggested earlier.
But then he said, if he was doing it, he'd do either the 60mm or 80mm Lewmar system.

Had a chance to look at some Lewmar blocks over the weekend. I must say I'm impressed. They somehow seemed more... substantial (?), is the best way I can think to put it, than the approximate equivalent Harken parts. Also, it looks to me like Lewmar is getting higher safe working and peak loads than Harken in blocks with a smaller footprint.

Quote:
Originally Posted by KeelHaulin View Post
On our boat we recently upgraded the traveler; it was originally 3:1 and impossible to move/control in winds over 15kts.
We have absolutely no problem with the traveler on any tack, in any wind, so far.

Quote:
Originally Posted by KeelHaulin View Post
HTH...
I don't know if it did, or not. I certainly appreciate the comments, but you've got me second guessing decisions.

I've had Alex say the 60mm Lewmar fiddle blocks should be fine for our needs (SWL: 882 lbs, breaking: 1764 lbs.), but he'd go with the 80mm (SWL: 2204 lbs, breaking: 4409 lbs.) if it was his boat. Harken comes up with parts with much higher working and breaking loads than the 60mm Lewmars. You're coming up with much higher loads than the 80mm Lewmars. Meanwhile I've got local people telling me the 60mm Lewmar parts should be fine, and one sailer even telling me what we've already got is fine.

So I think I'm just going to give the 60mm Lewmar blocks a try, and go from there. That seems about mid-way between the two extremes of opinion . Besides: The Admiral won't let me spend over $400 on the 80mm Lewmar solution.

Jim
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Old 09-24-2007
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Quote:
Originally Posted by sailingdog View Post
I have a 28' boat, with a 6:1 mainsheet system, and we need every bit of it. How large is the main on your boat? Mine is about 250 sq. ft.
Going by the 1/2*luff*foot calculation: 198 sq. ft.

Jim
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Quote:
Originally Posted by SEMIJim View Post
Somewhere between 15 and 20 kts, we'll be putting a reef in.

If we get 30 kt gusts w/o a reef in, we've done something very wrong, IMHO. I'm not saying it couldn't happen, but it shouldn't happen.
I don't know the waters that you are sailing in Jim; but some days out here in SF Bay we get light/moderate winds in the more protected areas; all the way to heavy winds with gusts to 35-45 in "The Slot" (the central bay in front of the Golden Gate Bridge). In between the two are areas where wind goes from light to high wind gusts and the boat goes from drifting to heeling heavily while the boat picks up speed. The gusts are controllable with some spilling and/or rounding up and keeping the sails full helps to make headway between the gusts (often times we are also fighting the current).

Don't get me wrong; we are usually reefed down more heavily than other boats on the bay when the wind picks up. However; I would not have my running rigging set up for a potential failure if the wind decided to overpower us before we could get a reef set.

Quote:
8:1?!?! You do realize we're talking about a 30' boat here, right?
{windward sheeting}Don't know what that means, sorry.
It seems experimentation is in order. Chris suggests not sheeting the main in quite so tight and bringing the traveler up, you suggest sheeting the main down tight and lowering the traveler.
Yes; I do. I also realize that the boat is set up with a 2/3 boom sheet and the loads get much higher with that type of control setup. Again; you want your crew to have an easy time working the sheets so fatigue does not set in. That's what 2-speed winches and triple blocks are for. You already know that a 4:1 system is too much working load; why not fix it? Dump the extra line down onto the cabin sole when you are going upwind; so that it is not in the way of your feet and tiller. 6:1 would probably be a good compromise.

Windward Sheeting is a special traveler that Harken makes. It releases the leward cam cleat on each tack so that you only have one control line to release when you want to hike or lower the car. It's an interesting invention; but not really necessary unless you want your controls at the car instead of at the ends of the track. You probably have 4:1 purchase on your traveler and that should be fine for your purposes.

If you loosen the main and hike the traveler you -might- reduce heel; or you might increase draft (power) and become over powered. When we want to go fast in light wind we hike the traveler and ease the main. The small amount of twist at the top is not really an issue for performance; the curvature of the sail down low is what we are looking for. If you flatten the sail you are first going to reduce it's power and then you can lower the traveler car to control it. If you get wind that is too much for this then you can ease the sheet to luff the sail; or reef.

Quote:
I am never going to be trying to sail that boat in 30 kt winds with a full main. By 30 kts I should be on the 2nd reef point and have the #3 up, if anything.
It's not about what you plan; it's about planning for what might be an unplanned situation. That's where you consider "what's the max load that these components will EVER possibly see"? And then you usually double that figure for safety. I'm sure this type of safety factor has been put into your standing rigging; why should it be any less for the controls? Otherwise; it's the life of you and your crew that you are putting in the hands of the weather gods. But we are only talking about what you want for a conservative cruising setup so you can get away with a rated SWL for a gust at 40 kts (IE SWL of 4000 lbs). Harken's sailing-spec calculator recommends these components, the load calculator confirms it; and these calculators were developed by engineers who know what components are suitable for the loading described.


Quote:
Had a chance to look at some Lewmar blocks over the weekend. I must say I'm impressed. They somehow seemed more... substantial (?), is the best way I can think to put it, than the approximate equivalent Harken parts. Also, it looks to me like Lewmar is getting higher safe working and peak loads than Harken in blocks with a smaller footprint.
Does not matter what brand IMHO; so long as the SWL is in the correct range. Please, don't confuse "Breaking Load" with "Peak Load". You never want for the actual "peak" load to be close to the breaking load; because you are only asking for a failure of the component; or premature wear (damage to the bearings, fatigue of the metal, etc).


Quote:
I've had Alex say the 60mm Lewmar fiddle blocks should be fine for our needs (SWL: 882 lbs, breaking: 1764 lbs.)...

So I think I'm just going to give the 60mm Lewmar blocks a try, and go from there. That seems about mid-way between the two extremes of opinion . Besides: The Admiral won't let me spend over $400 on the 80mm Lewmar solution.
Hmm... I think you should be making the decision based on what the calculator tells you and erring on the side of safety. At 25 kts wind your mainsheet bail will see a load of 1500 lbs; so that is way too close to the breaking load of 1760 lbs. Certainly 25kts wind is within the normal cruising range for most boats; your apparent wind in 15 kts true is over 20kts. Personally I would want components that are failure-proof instead of failure-prone. Does The Admiral have a good life jacket? She should consider the mainsheet control just as important to her safety as a good PFD.

Last edited by KeelHaulin; 09-24-2007 at 02:22 PM.
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Old 09-24-2007
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Quote:
Originally Posted by SEMIJim View Post
Going by the 1/2*luff*foot calculation: 198 sq. ft.

Jim
Pretty close! the Pearson sail plan shows 197 sq. ft..
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Quote:
Originally Posted by KeelHaulin View Post
Hmm... I think you should be making the decision based on what the calculator tells you and erring on the side of safety.
I cannot argue with that. But I likewise cannot convince The Admiral of it when I've got local people arguing differently. Plus I've had at least two different people tell me the Harken calculators over-estimate. (Yes, of course at least one of them said that w/in earshot of The Admiral.)

Quote:
Originally Posted by KeelHaulin View Post
At 25 kts wind your mainsheet bail will see a load of 1500 lbs; so that is way too close to the breaking load of 1760 lbs.
At 25 kts I'll be reefed, unless it's a puff and the average wind speed is under 20kts.

Quote:
Originally Posted by KeelHaulin View Post
Does The Admiral have a good life jacket? She should consider the mainsheet control just as important to her safety as a good PFD.
She does. We both do.

Problem is: I have Alex telling me those Lewmar parts are sufficient to our needs. I have local people telling me everything from the same thing to "there's nothing wrong with your current blocks." In the end: It's her boat and her money.

Is there a chance the new Lewmar parts are not as strong as the current Shaffer parts?

Jim

Last edited by SEMIJim; 09-24-2007 at 03:44 PM.
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FWIW we use a 4:1 cascading to a 16:1 mainsheet on a 400 sq ft main and (touch wood) we have had good luck with this arrangement. 400 ft2 is pretty much the limit though even with prudent reefing.
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Jim-

I understand the position you are in. There are plenty of people walking the docks that can give advice; but the bottom line is you need to base your decisions on what you KNOW to be correct. Always keep that in mind; and keep in mind that riggers are very well paid because they KNOW what the correct applications are and the decisions they make are for the safety of more people than just the owners. I'm sure that Harken's calculator is on the conservative side; but they also need to be sure that their advice is not wrong in a large percentage of the inquiries.

Most people that own a boat; specifically a sailboat are aware that the safety of the crew and guests are ultimately the responsibility of the skipper; so when something that could have been prevented happens the liability rests with the skipper (owner) in your case; not the people who may have given their (wrong) advice. That's why it is important to choose the correct hardware for things like mainsheet controls; it could go way beyond your insurance liability limit if the boom fails and severely injures (or kills) someone. For the extra 2-300 bucks it IS cheap insurance for the long time you will own the boat. It is a small expense relative to the purchase and long-term mainenance and berthing costs; so it should be a no-brainer (IMHO).

Do some online searching for a good price on the hardware; you might find that the cost is not as high as seen on the Harken (MSRP) website should you choose to select items yourself. Garhauer has some pretty good online prices should you decide to go with them.

Call a rigging shop and ask them to spec the correct block setup for your boat. If you do; pay them for their time by purchasing the product through them. That way you can be sure you get the correct size parts; but it will probably cost a bit more than buying online.

I don't know what the load capacity of your old controls are; if you replace them with 4:1 and low load blocks it seems to me like it would be trading one bad apple for another. If those Schaefer blocks happen to be high load carrying you could be making matters worse.

My opinion is based on what the Harken calculator says for 35-45kts. My description of SWL vs. Breaking Load and what it should mean to you is based on my knowledge, experience and judgement as a Mechanical Engineer (FWIW). This is only my opinion; and I don't take any responsibility for your decisions (or anyone else who reads this thread).

Last edited by KeelHaulin; 09-24-2007 at 06:28 PM.
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I think there are a couple of points which are confusing. I take the normal design sail area as around 15 knots real - 17 or so apparent. The Harken calculator gives the force presumably for that sail area in whatever wind speed. Sure if you get gusts to 30 you will be well overpowered, like about 3 x. You would want to have reefed but if you haven't as may happen, various adjustments will occur ie heeling and spilling wind. I doubt the calculator adjusts for that because it is a function of the boat. The boat may also round up, spilling wind. However the basic point would be that you could have difficulty releasing the mainsheet because the loads would be greater.
My point about the traveller is a bit simplified. Setting aside light winds, having the traveller down and the mainsheet tight both flattens the sail, and by decreasing twist can make the leech tighten giving a loss of power in the upper sail by loss of laminar flow. That is fine in a reasonably steady wind. However the other approach is to let the upper part in effect luff, by letting the mainsheet out which is fairly instinctive in a gust. That also lets the boom out which may be temporarily helpful, except that the jib then makes turning upwind harder as the rig is unbalanced. Accordingly you can maintain some drive and balance by moving the traveller up and the mainsheet out, or simply moving the traveller down and the mainsheet in or out depending on whether the response is enough. They interact.
A difficulty in a gust is that the apparent wind moves aft increasing heeling, and maybe requiring you to head up. It may be that you are steering and have to use one hand or your wife has to handle the main. That said you are probably cruising, and want to be comfortable and secure rather than wanting to get into any complexity.
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Old 09-24-2007
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Here is something that you might want to consider:

http://www.harkenstore.com/uniface.u...?409Z56LC4Z4Q6

Looks like it's rated for 275 sq ft at mid-boom so it should work for your application. What's neat about it is that the fine-tune is fixed to the ends so when you adjust with it you don't run out of purchase. The best of both worlds for sure! Sailnet has a very attractive price on it (click the add to cart to see their retail price).

Was doing some checking on my boat's mainsheet; it appears (via Harken's calculator) that the double block that attaches to my traveler is not big enough either Rated at 2500 Lbs SWL; I'm sure we are exceeding that by a bit when we get out in the heavy wind. While not severely undersized; it will be upgraded sooner than later. My boat has 3/4 boom sheeting with 300 sq-ft main.

It's possible that the Harken page is calculating mainsheet load in the event of a round-down (IE if you are 90deg to the wind and generating lift). It would make sense that they give maximum possible load numbers to be sure the product you pick cannot fail under most circumstances.

Last edited by KeelHaulin; 09-24-2007 at 08:15 PM.
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