Multiple headsail, "mainless" sailplan

Discussion in 'Sailboats' started by massandspace, Dec 5, 2017.

  1. massandspace
    Joined: Sep 2017
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    massandspace Junior Member

    Designing and building a custom sailing catamaran...thinking....

    My question (and I think this applies to any sailboat, really)...

    Why have a main? Why not set the mast way back on the boat and just use multiple (say 3 in my case) roller furling headsails? Cheaper (yes, agreed, 3 drums and 3 headsails but no boom, no mainsail, no main halyard winch, no lazyjacks, no traveler, no sail cover, no mainsheet blocks, etc.....and (very key to me) much much quicker to set sails (just unroll one or two or three as opposed to uncover, halyardize, unsailtie, unlazyjack, raise, trim, set, reef, tweak traveler, etc. the main).

    If the boat had 3 jibs say...a larger genny, a mid-sized jib and a smaller high wind jib....that could all be set alone or in combination very quickly using rope clutches and only 2 winches....would that not allow me to set 6 different combinations for different wind speeds?

    For example, in super light winds all three could be set? (my main question....would setting 3 jibs "triple" (or add, really) the power of all 3 sails? If yes, then the jibs could be much smaller (add the first and third, for example, to match the windspeed.)

    The boat is being built at present and the planned sliding centerboard could be designed to be located at the "average" CLR of the "average" sail set. So, yes, depending on the set, there may be some adverse weather or lee helm, but the sliding board will also be raisable, so that could potentially be used to adjust the CLR, no???

    And this is just a cruiser for the local area....if it ends up with a bit of weather helm at certain set....then so be it!

    Three sets of backstays would run from the three jib termination points on the top area of the mast and of course diamond stays to stabilize the entire column....why not?

    Again...I am brainstorming....but would fully enjoy NOT raising a main on the boat ever again....just unroll a jib (or 2, or 3) and be on my merry way.

    I have uploaded a screenshot of the unfinished design....just shows two jibs and they are not sized right and the backstays and diamond stays not drawn yet....working on the drawing and will update when dialed in..tis what it is...
     

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    Last edited: Dec 6, 2017
  2. CT249
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    CT249 Senior Member

    I'd much rather raise a mainsail once than have to ease a genoa sheet at every tack, make sure it gets past the inner forestay, wind it in, cleat off, walk forward, get it over the guardrails, walk back, wind it in further, then cleat it off until the next tack.

    Secondly, with the right setup a mainsail will automatically depower with mast bend as the wind increases. A genoa gets fuller as the wind increases due to forestay sag.

    With a mainsail and jib you need to adjust two sheets. With three jibs, you need to adjust three sheets. Why is that easier?

    Your costs seem a bit odd. You talk of the cost reduction in not having a main, but not of the cost increase of having a second and third jib. You talk of the cost reduction of not having a traveller (which you don't need) but not of the cost increase of having the winches to handle one or two extra jibs. You note the cost of a boom, but not the cost of the extra backstays. Perhaps most significantly, you do not mention the cost of one or two extra furlers. And you don't need an extra winch for a mainsail halyard if you just have a clutch.

    By the way, on my 36 footer reefing the main takes less than a minute singlehanded, from leaving the wheel to getting back to it. I plan to improve systems further. And that gives me a sail that can still have its shape easily altered (by merely pulling a 6mm line or an 8mm line) so that it can be deep and powerful in the head or almost dead flat, and that adjusts itself to depower in gusts, and needs no tending through tacks.
     
  3. upchurchmr
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    upchurchmr Senior Member

    Sounds like a very extensive thread here previously.
    You might want to search here or on woodenboat.com
     
  4. rwatson
    Joined: Aug 2007
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    rwatson Senior Member

    Or you could use the "all foresail" design of Russell McNab and his "Caravelle"

    Caravelle.jpg
     
  5. gggGuest
    Joined: Feb 2005
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    gggGuest ...

    You may wish to look at the interminable aftmast thread...

    Aftmast rigs??? https://www.boatdesign.net/threads/aftmast-rigs.623/

    The short answer is that this is an idea that has been tried a good number of times before, and the general conclusion is that the disadvantages outweigh the advantages for the vast majority of circumstances. For a given person in a given situation it may well produce a result they are happy with.

    The only other thing to note is that there are some who draw selectively from over simplified and out of date aerodynamic theory to claim that the headsail only or mast aft rig is more efficient, and such claims are simply nonsensical.

    But there's no reason why such a rig shouldn't produce a boat with usable performance, even if it is a bit expensive to build and run.

    Three headsails close to each other off the same mast, though, will produce a lot less performance than the sum of their parts. Its the old biplane/triplane problem.
     
  6. PAR
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    PAR Yacht Designer/Builder

    As your design stands now, the rig will collapse pretty quickly. You obviously need a fair bit of study in the engineering involved, not to mention aerodynamics, as your assumptions, just can't be validated.

    Aft mast rigs have been successfully done, though none have been particularly practical or stellar performers. Maybe looking into Brian Eiland's effort and thoughts on this subject might be helpful, as would Hoyt's.
     
  7. massandspace
    Joined: Sep 2017
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    massandspace Junior Member

    Thanks for the replies and links to other discussions on this topic...

    The pic I uploaded on the first post was not complete....I have uploaded a better one now on this post....with backstays and jumpers.

    I totally disagree with the idea that the main is not a big deal to set. I can roll and/or unroll a jib in a few seconds. If the wind increases, it takes me about 10 seconds to reef the jib a bit....all from the comfort of the cockpit. Yes, to tack with such a system I propose would probably entail rolling the jib each time....but again, I can do this very quickly and I am not racing the boat....

    Reef the main? Struggle to get to the mast base area, ease the boom vang, set topping lift, go back to cockpit to unlock the clutch holding main halyard, go back to mast to wrestle the main down a bit, cleat the reef grommet to the downhaul line, use outhaul to stretch out foot, go around and sail tie the loose foot up, go back to cockpit to add tension to the luff, add downhaul tension, adjust traveler, sheet in....probably forgot a few steps as well, and the coffee has either spilled or gotten cold so go below to make more. I think if this description were false people would not spend tens of thousands of dollars adding new-style boom rolling systems for the main...and I see more and more of them out there.

    Costs: I can use the same winches for all 3 jibs, so no extra cost there (a few blocks). Furling drums are not super expensive. Rigging likewise. I don't think the system I propose would be cheap, but would not be much more, if any more, than buying a mainsail, boom, winches for both the mast (halyard) and the mainsheet, sail cover, blocks, traveler, mainsheet, etc.

    OK, I will continue to think about this...one of my main questions is if you unroll two jibs (regardless of thing a main) that are set behind one another, and the first jib is 100 square feet and the second is 200, would that be the same (or at least very similar to) having a single 300 square foot jib? Cab you just "add" the sail area together? What is the "biplane" problem as mentioned above.....does one wing affect the other?
     

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  8. PAR
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    PAR Yacht Designer/Builder

    Of course one "wing" affects the other. Up wind it rides in the shadow of the lead sail. This is why you don't see racers with multiple headsails. Again, there's a good bit of information you'll need to absorb, before you can think about tackling this set of problems. Do yourself a favor and pick up one of Marchaj's books on the subject.
     
  9. CT249
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    CT249 Senior Member

    If that's the way you reef I can understand if you dislike it. You can easily set up a system where you don't have to leave the cockpit. All you do is reach forward, dump the clutch, lower the halyard, pull in the luff reef, ease the sheet, pull in the leach reef, and pull the mainsheet back on. The main falls into the lazyjacks and bag automatically. There's no need to adjust the vang (although I sometimes do, it's a matter of a second or two), adjust traveller, use the outhaul to stretch the foot or to add downhaul - those come on automatically as you wind the reefing lines down. As I noted, less than a minute for my 47' luff. Note of course that one doesn't have to reef too often because a good fractional rig uses mast bend to carry sail to well into the 20 knot range, with the main flattening out nicely through backstay and rig tension.

    Yes, some people are adding complex systems. However, if the fact that a system is popular means that it's good - which seems to be your point when you raise the popularity of complex reefing booms - then by that measure an all-headsail rig must be very poor, since they are so rare.

    One could also say that reefing a jib so that it retains an efficient shape similar to that of a reefed main involves the sail flogging around and then lurching along the lee deck being whipped in the face by the flogging sheet as you move the sheet lead forward on the track to retain some semblance of a decent fore-and-aft lead angle.

    One can also point out that the sail then has none of the trimming aids that you mentioned with the mainsail, such as outhaul (or leach reefing line, which becomes the outhaul). Instead, one has a sail that effectively has no luff tension and has the depth and efficiency problems that are inherent with a sail where the effective luff moves back and forth, and that becomes deeper as the wind increases rather than flatter. Finally, you mention that the mainsail has a traveller so you can adjust twist and sheeting angle independently - but your jib has no such system. Therefore it seems that you are comparing a complex mainsail system to a simplified (and therefore less efficient) jib system. If you want to compare equals then a mainsail with a traveller and boom for sheeting angle control should be compared to a jib with athwartship tracks or barber hauler for sheeting angle control.

    Using the same winches for three jibs means that either you have to dump highly-loaded clutches and hope the sheet doesn't cause trouble as it speeds away, or you have to first load one sheet, dump the clutch, ease the sheet, then load another sheet and repeat the whole process. And once all two or three jibs are flogging in the breeze, how well is the boat going to tack?

    Once you're on to the new tack, one or two jibs will still be flogging themselves and snapping sheets around while you wind the first one or two in, clutch it off, unload the winch, put another sheet on the winch, wind it in, etc. Why do that for every tack?

    The fact that you say you can can use one winch for three sheets but that one mainsail halyard requires a dedicated winch, and that you need a mainsheet winch, seems to indicate that you are searching for ways to justify the system.
     
  10. Dolfiman
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    Dolfiman Senior Member

  11. CT249
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    CT249 Senior Member

    I had a look at the Vitali design and it seems to have obvious issues when tacking. Check the comparison of the two sailplans. In the conventional rig, the jib is easily flipped across - in our 36 footer we often don't need to winch the jib in at all on the new tack. With Vitali's boat there is a vast overlap on the headsail and it has to be dragged around the forestay.

    It's amusing that in the illustration there is a woman lying just where the flapping jib sheet would probably fly around with great force. It also looks as if the requirements to move the jib lead forward has been ignored.

    It's also amusing to see the people who have commented and claimed this is a new idea. It's an old one, dating back to the Hoyt rig of the '80s. Hoyt had success with a main-only rig but his jib-only rig seems to have flopped.

    In many ways this is like an early 1970s IOR rig. There's good reason we dropped those.
     
  12. Dolfiman
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    Dolfiman Senior Member

    I suppose the J1 is furl /unfurl at each tack change or each jibe, as it is done usually when fore stays are close together. And that the J2 is self tacking ( I think the cross beam for this self tacking is positioned too high in Vitali design).
    The main question is the efficiency of this sail plan, more exactly what efficiency loss is conceded in exchange for this simplification. Too, more weight is concentrated backward, hull design should take that into account, could have a negative effect on the pitch dynamic.
     
  13. gggGuest
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    gggGuest ...

    You won't ever get decimal place measurements, because there are so many variables, but the efficiency loss is considerable. The triangular jib, close hauled, is the least efficient sail in the fore and aft rig. Two jibs overlapping at close quarters takes another big chunk out. As soon as you get off the wind then the efficiency is far worse, because a jib twists off so much.

    If you're happy with "OK, for me and for what I want to do, I like the perceived advantages of this rig so much I don't care about efficiency" then that's a reasonable call. It wouldn't be mine, but its reasonable. I think before I spent loads of my own money on a boat that will effectively be mine for life, as almost unsellable for more than scrap value, I would want to find a boat rigged like this somewhere in the world and go and have a sail on it to see how it matches up in practice to my expectations. I think, as it seems probable you haven't had an opportunity to do so already, you should also find a boat that is really well set up for singlehanded sailing from the cockpit with a sloop rig, and find out how well that works out for you in practice. There is, after all, nothing like learning from other people's experience, even if it does cost you a load in air fares.
     
  14. gonzo
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    gonzo Senior Member

    On a catamaran a boom is unnecessary. The main can also be furled so that is not a difference with a jib.
     

  15. sharpii2
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    sharpii2 Senior Member

    A few thoughts:

    1.) As shown, this rig is not strong enough. the reason is that the back shrouds do not have enough angle. To get enough of this angle, you will probably have to resort to at least one aft facing spreader, maybe two.
    2.) You would probably do better with just two jibs. It will be a lot easier to adjust them in relation to each other than it would be with three. The mast, its shrouds and its spreaders will produce a lot of drag aft, which will make the boat want to point up wind. When sailing down wind in windy conditions the inner jib could be struck and the outer one could be roller reefed as much as necessary. When sailing upwind in such conditions, the outer jib could be struck and the inner one be used. Reaching in such conditions both sails could be roller reefed to get nearly the precise balance needed.
    3.) I agree with the others that this is not very efficient rig, because the two jibs will almost never be ideally set. There is also the issue of a lot of staying and spars per given amount of sail area. These shrouds and spars must be set up under great tension to get the best out of this rig. But, this being said, it may turn out to be a very good cruising rig, as the boat will ride at anchor much better than one with a more forward stepped mast would. With all the sails in front of the mast and the mast stepped perhaps three quarters of the deck length aft, the halyards will be very easy to get to. With really high quality roller furling gear, handling the sails will be quite easy to manage, except during short tacks. Even with less than ideal shroud tensions and sheeting angles, it will work reasonable well, but would likely be roundly shown up by a boat with a more conventional fractional rig of the same sail area.
    4.) Another disadvantage of this type of rig is that it would be much more difficult than usual to add large light air sails, as there is not much room for the clew to go aft past the mast. To get the added area, such light air sail would have to be cut with a relatively large shoulder and maybe set from a sprit in front of the jib stay.
     
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