Aftmast rigs???

Discussion in 'Sailboats' started by jdardozzi, May 28, 2002.

  1. RHough
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    RHough Retro Dude

    This does not address the question. The question is dynamic gust response, not static headstay tension. A good sail shape can be cut to fit any given headstay sag.

    In a gust a stayed sail induces more sag, and thus more camber in the sail. Added camber increases the power and healing moment. If the boat needed more power before the gust, the sails would have been trimmed that way. Gusts in this context overpower the boat. Stayed sails increase power in gusts, just when less power is needed.

    An unstayed rig or the unstayed portion of a mast above the hounds can be designed to fall off to leeward and ease the leech. Reducing heal and reducing power in response to a gust. This is an automatic proper gust response.

    This correct gust response cannot be designed into a stayed sail. No matter what the static tension might be. This is one of the reasons that in area controlled development classes the sail plan evolves to either a fractional sloop or a single sail or wing. Overlapping sail plans and stayed masthead sails do do not evolve for performance unless other factors are in play.

    Personally I find conventional mains to be quite docile. The sail is controlled well. I'd much rather deal with slab reefing a conventional main that have to dodge a flogging jib clew on my way to clear a fouled roller furling line. In mast or in boom roller reefing mains are every bit as easy to deal with as roller reefing headsails. I don't see a sail handling advantage to the aft mast design.

    This leaves the question of sailing efficiency. No one has shown number that indicate that the aft mast configuration is better when the total rig is considered. In fact aerodynamic professionals doubt it.

    This citation:
    This is a built in error unless the documented drag reduction of a sail behind a bare mast is factored in. You cannot compare an aft mast rig with a conventional rig by ignoring the mast sail interaction.

    I've read every post and followed this thread for years now. Still no hard number proof of any advantage to the aft mast configuration. Still no response to the dynamic gust response question.

    All that remains is the ease of sail handling claim, which I don't see at all.

    R

    PS the 49'er claim about similar AWA is wrong.
    J24's sail with full Genoas and flat mains to reduce weather helm, tight head stays on J24's are not an issue. If they were allowed to move the keel the headstay sag might become an issue, but the OD Class rules do not allow it.
    Code Zeros are flown when the sailing angle and wind speed do not allow the boat to be fully powered with a Genoa. They were developed for a class that did not allow masthead Genoas. Code zeros have backward gust response too.
     
  2. Dave Gudeman
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    Dave Gudeman Senior Member

    With all due respect, I don't think that you are a good person to judge this. You are obviously a very experienced sailor. I'm sure that you react properly and almost without thought to conditions that would have casual sailors stressed out and scrambling.

    To casual sailors, that boom seems like a disaster waiting to happen. We are always worried about accidental jibes going downwind, even when it is not really a danger, because we aren't confident of our own judgment of when it's not a danger and we aren't good-enough helmsmen to be sure we can keep out of the danger area.

    In a family outing there are often kids or dumb teenagers running around and you are always worried that they are going to be in the way when the boom has to swing over. You still wouldn't want them in the way when a boomless sail swings over, but that is less dangerous if it does happen.

    When I have to get up on top of the cabin to flake the main, there is usually someone even less experienced than me at the helm and I'm worried about the helms(wo)man keeping it into the wind. Occasionally I haven't been paying attention and wind conditions are already too high. In-mast or in-boom furling makes things easier, but the mechanism is more complicated than stay sail furling and more likely to jam (or so it seems to me --I've never actually had a jam).

    Intellectually, I know that all of this is really pretty safe and that I'm not sailing anywhere near the limits of the craft and that the boat is small enough that I really can keep an eye on the kids, but it still creates a lot of stress and that limits my enjoyment of sailing. Getting rid of the boom seems like a great idea to me, even if I lost some performance. I don't have any desire to race. (I actually looked at a boat that had a boomless main, but it was a motor sailor without a cockpit --you had to sail from inside the pilothouse, and that didn't seem like real sailing to me).

    Of course I really don't like the idea that power would increase in a gust. If that turns out to be a real problem then it might doom the astmast rig as the preferred rig for casual sailors but there are usually solutions to problems like that.
     
  3. Fanie
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    Fanie Fanie

    RHough,

    You have to experience sailing with an aft mast. Although my rig was small, I could still experience a much different feel from my friend's 'normal' sail with a boom.

    In a gust his boat would dip down and burrough the lee ama, while mine had a much lesser heeling effect. You could see the mast take force, and I could feel it in the line, but there was not that deffenate pushing it as if to try and capsize it. My leeward ama got hardly pushed down.

    We don't have a lot to live by on the moment, but in a while there will be something. Like I said, you have to experience it. There just is something to it.

    I would very much like to make one with a bit more racing in mind, but the funds... Huge potential there.
     
  4. RHough
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    RHough Retro Dude

    Thank you. I worked in a rig shop for a few years. I am indeed familiar with the solutions that make sail handling less stressful. Modern roller reefing booms a pretty darn nice. You get to keep a long lived full batten main and no longer have to stand on the cabin flaking a sail whilst your drunken cousin from Idaho tries to steer. :D For smaller boats a well thought out lazy jack system takes the terror out of reefing and allows the sail to be flakes properly after the anchor is down or back at the dock.

    Most casual sailors don't sail with their boats fully powered up so proper gust response is not so much an issue. Fully powered up is more heel than most casual sailors find comfortable. They sail at 15 deg heel not the 20-25 deg that a fully powered boat would sail at. Gusts just heel the boat more than they should. After a few 25 deg gusts, the skipper reefs to keep the mate happy and dinner on the stove. This ends up with the casual sailor motoring more and sailing less because they are not comfortable sailing the boat at more than 70% of her speed potential. Wouldn't it be nice if the gusts that used to knock you from 15 deg to 25 deg only knocked you to 20 deg? After you have some sea time and are comfortable sailing harder, wouldn't it be nice if the boat made it easier and did not demand much more attention than it did when you were sailing at 15 deg of heel?

    Cruising multi's are mostly under canvassed to begin with. One of the things we have done is gone sailing with cruising multi owners and offered advice on rig tune and sail trim. The usual result is they sail more and motor less. That big roach main can be trimmed so the leach opens and depowers in gusts, not so a masthead Genoa.

    One of the posts here shows a rig with the same area and a lower mast. This cannot be more efficient than the same area on a taller mast. Basic aerodynamic theory here.

    Three sails on centre cannot sail as high as two. Two cannot sail as high as one. Again, basic aero theory. This is as important to the casual cruising sailor as the racing sailor. Rig efficiency and the ability to sail to weather is a high priority when a squall hits and your anchor drags.

    None of this even considers the weight distribution of placing the mast and rigging closer to the ends of the boat. Getting weight out of the ends is a holy grail for sailing in comfort.

    I'd like to be convinced, but nothing seems to add up for me.

    R
     
  5. brian eiland
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    brian eiland Senior Member

    Boomless Rigs & Stiletto Cats

    Getting rid of the boom was one of my objectives when I originally thought of getting rid of the traditional mainsail all together.

    I became good friends with Peter Wormwood who became primary designer for the Stiletto catamarans (BTW a tremendously good sailor). A partner and myself became Stiletto's biggest dealer ever...we outsold all the other dealers combined, and we sponsored the first ever Stiletto Nationals here on the Chesapeake Bay (even Gary Jobson and Randy Smyth joined in).

    Stiletto cats at that time were the largest pre-preg/nomex cored pieces ever made outside of the aircraft industry. Peter first developed the STILETTO 30 from the original 27 by spreading the 27 hulls further apart, adding some length at the sterns, and balloning the cockpits over into the center area. Then he put a BOOMLESS mainsail onboard. What a great concept. We had plently of room to sheet this sail rearward, and we could almost make it a deck sweeper (didn't really) with out knocking everyone off the boat.

    Next came a smaller boat, and a totally new design, the STILETTO 23. It was also BOOMLESS as the idea had gone over so well on the 30. It also had a very pretty custom mast section design.

    I did a fair amount of sailing in both of these designs. And the 30 to me is just a great weekend boat. Add a center cockpit tent and you are ready for just about anything cruising around the Chesapeake Bay. BUT because its BOOMLESS you have a little more trouble rigging that tent structure. Of course that no reason to include a boom :rolleyes:

    Later on it became neccessary for me to redesign a 25' foot trimaran I was attempting to import, the original Dragonfly 25. I had learned some things from my Stiletto days, and one of them was GET RID OF THE BOOM. I found the perfect spot for a circular traveler (Stiletto did not have this luxury) at the rear of the cockpit, thus eliminating the boom AND the traveler track that split up the cockpit...WOW, everyone loved it. Not only that but I also employed that beautiful mast section Peter had drawn up. Our boat became the FIREFLY 26. Very regrettably this project took me into bankrupcy due to some partnership problems and just not quite enought cash to do the whole project on my own. But what a great sailing boat, and no worries in that cockpit about radical manuvers.

    NOTE: I made a mistake, the original 30 had a boom as seen in the bottom photo HERE. It was the second boat Mirage, a custom racer that then went boomless. We raced that boat for the first time here on the Chesapeake Bay in what was known at the time as the Governor's Cup, one of the largest races on the East Coast at that time (something over 300 boats, and some fast monohulls). Multihulls at the time were only reluctantly allowed to race, and they put them all in a single start at the very end of the pack...16th if I remember correctly. You race down the bay overnight from Annapolis, Md, turn up the Potomac river, and tread your way up a winding river to the school at St Marys. We like to brag that we started last and ended up first boat to finish, but we never received even a single word of acknowledgement at the awards ceremony. :!:
     

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  6. brian eiland
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    brian eiland Senior Member

    Kids and family sailing were uppermost in my mind with the Firefly Tri as you can see from this illustration.
     

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  7. brian eiland
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    brian eiland Senior Member

    Shorter Rigs, Lower Aspect Ratios

    A lot of your posting is directed at the 'gust response', and I will agree with you that in an upwind or beam reaching situation the genoa type sail can not be 'bled off' like the top prortion of a traditional mainsail. (However off the wind you might find the genoa sail's response quite productive :eek:).

    In big gusty conditions going upwind and reaching both the racer and the cruiser can play the steering-up/falling-off routine to limit heel. And they both can play the mainsheet so as to spill wind from the top portion of the mainsail. However in those same conditions I don't believe you will find the pleasure sailor, nor the cruising sailor playing that in and out of the mainsail. Rather I think you would find that sailor reefing down that tall sail so as to not get overpowered by the conditions.

    But wait a minute, isn't my rig already 'reefed down'?? My mast aft rig on the 65 foot cat is approx 15 feet shorter than the comparible fractional sloop rig of the same sail area on this other 65' foot cat. And the rig on that 65' trimaran is approx 15 feet shorter as well...same sail areas. I would call this quite a reef. :!:

    Too often in the past the cruising sailor has been asked to bow before this altar of 'hi-aspect-ration-is-the-best' theme that permeates the racing crowds concerned with upwind performance...as though this is some sort of ultimate configuration. I think the cruising sailor will be much happier with the lower aspect ratios that Marchaji found VERY effective for all other points of sailing. My rig seeks to use those lower aspect ratios.
     

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  8. brian eiland
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    brian eiland Senior Member

    Stiletto Experiment, Lightning Experiment

    I was just informed today that a potential client has acquired two Stiletto 23's that he wants utilize to perform some experimental testing of a number of alternative rigs, including one on the aft mast configuration. He'll use one boat as the 'control boat' I believe and make mods to the other.

    This should be interesting....and VERY challenging for my rig as this vessel would NOT be high on my list to place my rig on....total lack of deceit boat structure locations.

    Personally I have a great interest in putting this rig on a Lightning class boat. I think this would make a fairly easy adaptation as a base structure, and there are lots of 'control boats' out there to sail-off against. Anyone have a good source of a Lightning at a real good price??
     

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  9. RHough
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    RHough Retro Dude

    Do not confuse an IOR high aspect rig with a modern high aspect fractional rig. Not concerned with upwind performance? Not too many years ago the cruising fleet anchored off Cabo San Lucas was hit with a late season hurricane. As the boats started to drag onto the beach, they ran their engines to ease the load on the ground tackle. They still dragged. Many boats tried to sail off the beach and failed. Several boats tried to motor off and the rough conditions stirred up the crap in the tanks and killed their engines. Many boats ended up on the beach. The boats that were able to sail to windward made it out. How can a rig designed for a casual sailor NOT make windward ability a priority? Ask any sailor if they would give up 5-10 degrees of windward ability for perceived easier sail handling. Then ask them again after they have sailed from Cabo San Lucas to San Diego. Not placing sailing ability first in rig design is why most cruisers have a VDS (Vertical Dacron Stabilized) motor boat and are looking for fuel bladders. These are the non-racing "casual sailors" that might consider alternate rigs. Reducing their ability to sail to weather when their life's dream and maybe their life is at stake is a high price to pay for no boom.

    I do not see the logic in trading sailing ability for ease of use. Lower aspect ratio on a cruising cat makes no sense to me unless you are up against a air draft limit for the ICW. Given the RM available for production cruising cats, the sail plan can go from stem to stern and up to ICW height with very little danger of the boat being over canvassed. If the boat is very light and the crew is spartan, a tall fractional rig with a masthead screecher and A-Sail retains windward ability for safety and allows all the added area you could want for reaching in the trades.

    I just don't get it. I'm sorry to rain on your thread Brian, I'll try to avoid it in future.

    R
     
  10. brian eiland
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    brian eiland Senior Member

    I remember seeing pics of that...real shame.

    Here in lies one of our differences of opinion. I don't think I'm going to give up all that much windward capability. In fact I think this design will surprise a lot of folks with its windward capabilty. At its worst it shouldn't be much poorer that a traditional ketch. And by the way the extra drag of my ONE single bare mast (emphasis on ONE rather than two for a ketch) is not all that difficult to solve, particularly if I'm utilizing a std alum spar with an existing mainsail track.

    I'm 68 years old now, and I couldn't hoist that full battened mainsail on that 65' sloop cat without expending a great deal of energy. I'm still in good shape, but I just don't have the muscle tone for that job anymore. And I wouldn't relish reefing it up and down as the weather went up and down. But I would still like to be able to take that 65' of my design out for a daysail without a moments hesitation. I need ease of use.

    And I find a lot of other sailors who are tried of wrestling with their mainsails.

    There is another way to look at this, and I learned it racing multihulls. On the downwind legs there were many times we would hustle our asses off in multiple gybing manuvers downwind only to arrive there at the same time that the other crew did sailing a straight line course at a leisurely manner on one gybe. There is something to be said for average consistancy as opposed to the up and downs. I actually think that this rig might be sailed at a higher average speed than one that might be accelerated and decelerated with every whim. The less threatening stability of the lower aspect ratio may allow for carrying a bigger sail area for longer periods of a passage.



    No problem Randy. I appreciate your comments...keeps me on my toes :p
     
  11. CT 249
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    CT 249 Senior Member

    Better tell that to the J/24 guys*, the Farr 40 guys, the 470 guys, the Tasar guys, the J/105 guys, the 420 guys, the Lightning guys, the Etchell guys, the Flying 15 guys, yada yada yada!:D All of those classes regularly induce extra forestay sag in light winds, because it's sometimes (literally, not figuratively) sloppy but it's also fast.

    Even 10 years ago, some of the top Farr 40 guys readjusted their rig tension (D1s, D2s, etc) for increments of as little as 2 knots windspeed, to ensure that the forestay sagged enough in light winds. Such attention of detail is hardly a "sloppy" approach.

    * and girls in each case, of course.
     
  12. RHough
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    RHough Retro Dude

    I hear you and I've spent hours taking to customers about this.

    The answer for me is to use a powered winch for the main halyard and use a roller furling boom. Run the lines to the winch and you have a near zero effort system. Andersen makes a line of compact electric winches that are deck mounted.

    I really like this option compared to in-mast systems. The sail shape is better (you can have a roach with full battens), almost as good as a standard main.

    The only hassle that remains is the gybing terror. With a boom brake the violence is gone. Granted gybing a loose footed sail is next to no drama, a brake on the boom makes a standard rig pretty docile. We're cruising after all, use a second powered winch on the main sheet to grind it in, turn the boat and ease. The unintentional gybe is the scary one. The loose footed sail will fill on the wrong side and will stay backed until the sheets are eased. The boomed sail with brake will just come across and set on the new gybe with very little commotion, on mono's people rig preventers that make planned gybes more work than they should be just to avoid the accidental gybe. The preventer can actually become a liability if it holds the main backed and pins the boat.

    When we think about reefing we should also consider weight aloft. A sail that roller reefs on it's luff keeps the weight at full hoist. Now that you've shared your age, I know you remember reefable hanked headsails. In mast mainsail reefing is a tripple whammy. The mast is heavier, the sail has no roach, and when reefed the sail's weight is still aloft. Slab reefing or in boom reefing keeps the mast light and the weight of the reefed sail is on or in the boom, reducing weight aloft and easing the motion of the boat.

    Add to this the fact that a roller reefing boom is a great water catcher. Install a spigot and run a hose to the water tank ... how cool is that. This idea came from a few experiences with roller booms that had many gallons of water inside giving the crew a dousing ... we hadn't thought where the water that used to run off the main was going ... :(

    If these newish solutions were not seaworthy, reliable options I can see much more value in having multiple sails on luff furlers. Now I see the rig as an answer to a problem that has been solved and can be easily retrofitted to almost any boat.

    The last point in favour of a boomed main is the DDW situation. I've given up trying to get people to stop sailing DDW (its slow and leads to the dreaded unplanned gybe). How does a Genoa set when sailing deep angles unless you stroll forward to set a wisker pole? How does a standard main set? If you want or need to sail deep angles having the equivalent of two Genoas means you have poor sail shape or you have to wrestle with settting poles. This just abouts negates any easy sail handling. Even if you sail broad reaches, loose footed sails set poorly. Ease the main, hoist a downwind sail (on a continuous line furler) unroll the sail, trim, cleat, drink ... easy peasy. Sailing very deep the main is still fine (the boom is projecting the area), roll up the reaching sail, hoist the runner (in a sock), trim, cleat, drink.

    I don't see it being any easier than this with the possible exception of an unstayed cat ketch like the Wylie 65-66. There you have wishbone booms that are high enough to not bang heads and nets to control the sail when reefed or doused.

    R
     
  13. brian eiland
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    brian eiland Senior Member

    Mainsail subject ......again

    Looking back thru some older postings on this subject thread I ran across this one #46


     
  14. RHough
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    RHough Retro Dude

    Where do I start?

    Want to bet they never practiced a MOB drill either? This post screams "I'm a novice sailor and I scared myself." How is that the fault of the rig?
     

  15. pbmaise
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    pbmaise Senior Member

    Update on Phil's Aft-Mast Sea Trials

    Just a quick update on the sea trials of my aft-mast 65ft trimaran. This Saturday I'm scheduled to head into the South China Sea for a quick sail to Brunei. Winds look like they will be light. Based upon my tests into the wind I will then decide route to Palau. I may cut through the Philippines and head dead East and into the wind, or go north of the Philippines where I can come down again.

    I'm getting some interest from people here in Singapore that want to buy my rig for charters. The like the big open 40ft beam and fact the boat now sails with no reefing lines, no sheets, and only one sail. They really liked fact my boat tacks without turning on the engine or moving a single line.

    Phil Maise
     

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