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Old 31-01-2007, 20:45   #1
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Staysails

From the "Spray and Suhaili" thread:

I have been thinking of openning another thread on this topic because I have been wondering about proper sail trim for a saysail on different points of sail.


Quote:
It should be noted that the most efficient setup, for a given sail area, is a sloop with a large mainsail and a non-overlapping jib.
By this do you mean a non-masthead sloop or do you just mean not using a genoa is more efficient? What do you mean by efficient? Are you saying it is the most convenient sailplan or does it actually do something to the center of effort that makes it scientifically more effficient?

Quote:
"The most obvious advantage of the stays'l, whether it is on a schooner, ketch or cutter, is to make each individual headsail smaller and easier to handle."

I have heard of a staysail "powering up" the other sails in the rig. Does this mean that you are just adding more sail area to the overall rig or is there some way that a staysail redirects air flow to the other sails. Isn't there a time, like on a broad reach or run, when a staysail will put the genoa in a wind shadow and stall it?
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Old 31-01-2007, 22:02   #2
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Probably the best (and probably the ONLY) aerodynamic explanation of a staysail was by the famous aerodynamicist/sailor Arvel Gentry in the 1974 article: http://www.arvelgentry.com/magaz/The...e_Head_Rig.pdf

Obviously on all other points of sail than beating/pointing the staysail 'fills-in' the foretriangle with more sail area thus adds overall sail efficiency; but, the real question (in that article) was how does it apply when beating and the staysail is overlapped by a genoa ... read the article for the answer.
When beating I find (by recording of the data points of increased speed, etc.) that the staysail 'can' be of benefit if trimmed correctly to aero principles (but such trimming is NOT by intuitive methods .... ie.: staysail 'drawing', etc.).

Arvel Gentry was the aerodynamicist who set the sailing community on its collective ear back in the 1970s by his explanations of 'how sails really work', debunked the 'slot effect' and other sail/wing *myths* that are still taught in todays highschools and are still offered in 'how to sail books', etc. Even the Wright Brothers knew 'different'. For these Gentry articles go to ArvelGentry.com -----> "magazine articles"; caution- these articles are highly technical and need to be read and re-read if you dont have a fluids or 'aero' background.

For your 'powering up' question ... the answer is a positive YES as the staysail 'bootstraps' (an aero term) the genoa .... just as the mainsail 'bootstraps' the genoa making both more efficient. Obviously if a sail is in a windshadow of another the efficiency falls off considerably.

Beware of using the term 'center of effort' as this is only a 'static concept' used by boat designers as the 'center of effort' is a combination of the 'dynamic' (not simply geometric) factors that are generating lift .... an example of one of those 'myths'. The geometric Center of effort is only valid if you are sailing with the sails perpendicularly ACROSS the wind. ;-)
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Old 01-02-2007, 06:17   #3
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Staysails have different uses depending on how you sail.

Racing we generally used it to re-attach flow to the main when flying reaching sails. Kites, jib tops, code 0's,,,

Cruising it is more often used to break up large sail plans or allow you to move a sail plan down and in as the breeze builds.

Racing and cruising sail management philosophy's are worlds apart.
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Old 01-02-2007, 17:27   #4
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I generally like to use a staysail with a second reefed main. It balances out the boat without loosing sail area vs just using the first reef. Or with a full main in lighter air, say 15-20 kt. steady............................_/)
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Old 01-02-2007, 20:35   #5
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My head hurts, Rich. I read Mr. Gentry's website in its entirety. I really didn't want to think that much while winding down after a long work day. At least I'll sleep well tonight. And I think I'll add a couple of tattletales next time I sail.

Brett
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Old 01-02-2007, 20:55   #6
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Stays'l, a modern practical concept

Long has it been recognized that a sloop-rigged small sailing vessel is a very efficient rig for most points of sail, especially hard on the wind.

Modern cruising boats have roller-furling (as opposed to reefing, which often is not truly mechanically supported by the roller mechanics under load) headsails that, if useful at low wind velocities, are relatively large in area. As a result, many headsails overpower the boat with relative wind velocities at or above 20-25 kts. What to do at 27 kts? Roll up the headsail and deploy a stays'l (if one rigs for that with a solent stay, for example).

I have "converted" my last two cruising boats to solent stays'l "slutter" rigs and enjoyed the results of being able to sail with proper footing with winds between 3 and 50 knots relative with the two headsail combinations and reefed (or not)main without having to deploy special "storm" sails.

Contrary to what I have heard, a stays'l can be used on reaches and off the wind, especially with a pole if one plans for that. Regardless, a good stays'l will pull waay better hard on the wind in heavy winds than a roller headsail set up will in winds appropriate to that sail's area, assuming good sheeting leads. This means to you that if one has to claw off of a lee shore in heavy wind and sea conditons the stays'l will do the job whereas another arrangement will not. Add to that the safety of being able to work with the stays'l at the inner stay under heavy sea and high wind conditions as compared to the pucker power of having to work a headsail on the headstay under the same conditions close to the very pointy end of the pitching boat.
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Old 02-02-2007, 12:10   #7
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I too read that article and my brain hurt. I hope to never have to think like that while enjoying a nice leisurely sail.

Rick, are you talking about rigging a hanked on jib on an additional forestay in addition to a forestay with a roller furler? I think my origional question was about using a staysail along with a jib or genoa like in a cutter rig, but this adds more questions in my mind. Can you rig a staysail in addition to a roller furling genoa without an additional forstay?
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Old 02-02-2007, 13:18   #8
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Stay or no stay

I've rigged a stays'l both with and without a built-in stay. On my previous cruisng boat (also built as a sloop but converted to a cutter) I first had a stays'l with the stay built into the luff of the sail. It worked O.K. but had two problems: In heavy air one had to put more luff tension on the halyard than what would have been necessary with a built-in stay; When raising or dropping the sail in heavy winds it was dicy due to the wind trying to carry the sail away when the luff is not tensioned.

Because I felt that it was unsafe that way I installed a removeable stay, which I rarely moved, and used a hanked-on stays'l that I could stow on the stay in a bag. I also had a roller furling headsail and DID often use both sails as a cutter even off of the wind. I did use the stays'l alone downwind in heavy air and both headsail and stays'l downwind at times wing and wing when I had the main double reefed and sheeted in tight just to stop the rolling in big seas. You have to pole both of those sails out to do that or else when the boat rolls from a sidewave the sail tends to collapse without the pole. I used a homemade wood pole for the stays'l and a Forespar aluminum pole on a mast track for the larger heads'l.

If I do not remove the inner stay, with the quick-release lever, I would sometimes just roll up the heads'l and unroll it when making a tack, it is so easy to do thatway sometimes without having to hand it around the inner stay. I also hate a stays'l on a boom, what a pain for the whole deck layout.

My latest stays'l (only a few months old) was made by Schattauer Sails (one of the few true skilled cruising-sail sailmakers) I had made to hoist on a solent rig. They made it with a roach and battens (not full) that will still allow the sail to be bagged and left on the stay without taking up too much length. The luff has high modulus line built in instead of cable which aids in the bagging. I love this sail becuase with inboard sheeting the boat will point very close to the wind (closer than I can with the roller heads'l) without much leeway. The sail will pull from 8 kts of apparent wind and really pulls like a bull with 25-35 kts of apparent wind. So, with 8 kts or more of apparent wind but less than 25 kts I can use both headsails to good effect. At or above 25 kts I roll up the heads'l and the boat foots well with that stays'l.

The idea of a solent stay is that one does not need running backs if one uses stout attachments just below the masthead. With the stay attached on deck as close to the headstay as is practical so as to obtain the most possible sail area for the stays'l one then realizes that the whole inner area cannot be utilized with a sail becuase the head angle would be too narrow to make a strong sail attachment, therefore, the head of the stays'l will be lower to give a better geometry. That is why I had a roach built in. The stays are removable and allow the sail to be trimmed to be full or flat for an easier accommodation of a wide range of windspeed and let the boat foot well.
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Old 02-02-2007, 13:35   #9
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Very interesting Rick. Sounds like you've got a good system worked out. How does the boat balance when booming out the headsails? Isn't the furling headsail bigger than the staysail? Wouldn't that make the boat pull to one side or the other threatening a broach, or do you furl the fore headsail and trim the two like that?
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Old 02-02-2007, 14:22   #10
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Staysail and headsail size?

So what might be the optimum size and arrangement for staysails and headsails?
I'm currently thinking it might be nice to have them both small and high cut (for visibility) and to see if it works without roller reefing.
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Old 02-02-2007, 23:12   #11
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stays'l size

Yes, I've always had a pendant on the tack and a high cut for clearing a deck stowed dinghy as well as for visibility. Because the cruising stays'l is primarily to use in higher (and high) winds than a 120 to 150 sized roller heads'l one doesn't want it to be able to flog and hit the mast, in my opinion. Put all that together and the stays'l area just will not be very big no matter how you try to make it and still be strong.

On a reach or off the wind I find that it is the main mostly that I have to be careful for adjusting the helm. Keep in mind here that a "slutter" (a boat designed as a sloop with added inner stay to add a stays'l) is not the same as a true cutter. A boat designed to be a cutter generally has the mast further back than a sloop allowing for larger stays'l areas without an overlap.

Cruising at sea in ligher winds one just cannot resist raising the stays'l even though it might result in only a knot of increased speed. That just doesn't upset the helm compared to the main and jib fullness and trim. Beside, it really looks neat with three sails up! Cool factor is not just for beer.

So, if one wants to address an "optimum" stays'l size it probably will be just about as big as you can make it without overlapping the mast and still be strong without killing visibility. I have seen some stays'ls with a very narrow apex at the head made in an attempt to "fill" the triangle and you know that it would rip out in a storm. The optimum in this case is a size that will at least pull the boat well for higher winds when the heads'l cannot be employed and even perhaps have a set of reef points built in for above 40-45 knots or so. It will probably, therefore, have something like 7 oz cloth or more and built strong. If it pulls adequately at low winds by trimming it to be full then that is just gravy for the cruiser. If you can't have adequate stay tension and trim it flat then you are screwed at higher wind velicities thereby losing a wide dynamic range of wind speeds that it can be effectively carried.
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Old 03-02-2007, 00:49   #12
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Matching headsail or jib...

Thanks Rick.
Now how would I match the headsail or jib with a staysail , given that I don't want roller furling unless it becomes compulsory?
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Old 03-02-2007, 07:22   #13
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If you look at the designs of the prominent 'blue water" (hate that term) designers especially those who are reknown for true cutter designs, you'll note that their area of the staysails seems to be geometrically (sail area X distance of the geometric 'centroid' of area from the mast) matched with area of their mainsails at the first (or second) reef. This will allow for good static CE location of this combination; thus, allowing good helm balance for upwind as well as down. So when adding a staysail, you really have to view/calculate the geometric center of area (centroid) for each sail and recalculate the combination of 'centroids' then compare the combination of all centroids versus ..... the 'center of lateral resistance'. Without satisfying such a rudimentary calculations you may wind up with a "very cranky boat'. One of the reasons that a true cutter (mast at approx 50% of length) works so well is that the average/combined CE is usually located somewhere IN the staysail and in front of the mast --- thus allowing just about ANY size staysail that you want.

The 'problem' with a staysail ... is the stay tension and how it interacts with the headstay. There is a needed 'balancing act' of stay tensions necessary so that each of the forward stays have the proper tension with respect to *luff sag* of their respective sails; a 'fine point' especiallly when going upwind. If you have such a boat set up tension-wise for main + headsail and 'simply add' a forestay for a staysail, you will note that the forestay reacts tension-wise with the headstay .... the headstay automatically loosens in reaction to the increased tension of the forestay .... not a problem for downwind but for upwind you'll now find that both stays are saging off to leeward and that sag no longer 'matches' the luff curve of the sails that sail maker cut .... and the result is a boat that heels more and slows down more than it should for anything above beam reaching. A backstay tensioner of some sort is almost mandatory for proper fore/headstay tension for just about any 'double headed rig' ... AND its all dependent on the 'ratio' of sail area (and windloading) of the staysail and jib/genoa. Some designers add 'intermediate' stays in an attempt to control this stay tension 'anomaly' ... but intermediate stays are 'mathematically poor' in controlling this. The addition of a solent stay yields the same problem.

Some 'things' to consider if you're keen on 'adding' a staysail.
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Old 03-02-2007, 14:00   #14
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Richh put it well.

Because I relied upon the expertise of my sailmaker (who spent almost two hours measuring everything on my boat before making the sail...I already had installed the inner stay) all that I had to do was retune the rig when setting it up. He had to figure all that CE stuff that Richhh outlined. Like Richh mentioned, I had to iteratively tension both headstays and the backstay until everything came together in heavy air just fine.

Now I've always desired to have an adjustable backstay tensioner yet so far not installed one, too many other things ahead on the "list". Regardless, both my previous "slutter" and my present one work great with the added inner stay using the normal methods of adjusting the flatness of fullness of each sail appropriate to the wind conditions before reefing or changing up or down to a different sail combination as the relative wind velocities change sufficiently so as to require it.

The main point here is that for cruising sailors that use roller headsails an inner stay with a stays'l offers a great solution for working a sail on deck in heavy wind and seas without having to suffer the larger motion and spray that working at the headstay only two to three feet further forward makes so miserable and unsafe by comparison.
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Old 08-06-2013, 00:07   #15
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Re: Staysails

i have read there is a distinction between somethign called a genoa sail and a jib sail...that being that a genoa sail extends beyond the mast???

if this is true, is there any advantage in tacking maneuvers to using a jib over a genoa???

or has technology of some sort overcome any alleged (so i have read) disadvantage of genoa sails???
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