Aftmast rigs???

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

  1. brian eiland
    Joined: Jun 2002
    Posts: 4,788
    Likes: 157, Points: 73, Legacy Rep: 1903
    Location: St Augustine Fl, Thailand

    brian eiland Senior Member

    Storm Sail Configurations

    What brought this to mind was the recent de-masting of the new Gunboat 55 in storm conditions off the mid-Atlantic coast a few weeks ago. And any possible misconceptions that I would suggest using the rolled up foresails on my rig as storm sails.

    So while searching around the internet for articles on very modern-day sail materials to be utilized with roller-furling applications I came across this article that I would submit as the proper manner to address handling a storm sail configuration with my 'staysail-cutter-ketch' rig.

    http://www.sailmagazine.com/boatworks/storm-sails
     
  2. brian eiland
    Joined: Jun 2002
    Posts: 4,788
    Likes: 157, Points: 73, Legacy Rep: 1903
    Location: St Augustine Fl, Thailand

    brian eiland Senior Member

    Another Furler Technology

    http://www.sailmagazine.com/boatworks/furl-it

     
  3. brian eiland
    Joined: Jun 2002
    Posts: 4,788
    Likes: 157, Points: 73, Legacy Rep: 1903
    Location: St Augustine Fl, Thailand

    brian eiland Senior Member

  4. pbmaise
    Joined: Jul 2010
    Posts: 115
    Likes: 5, Points: 18, Legacy Rep: 80
    Location: Cebu the Philippines

    pbmaise Senior Member

    Work on my roller furler was never tested. Laying on the deck when the strain insulators shattered cutting the Dyneema was a rotating spar. I had just completed it, however not raised it into position.

    This 62 foot long spar was constructed using three parralel aluminum pipes. They were arranged in a triangle interconnected every 2 feet. It very much looked like a radio tower. To prevent corrosion issues, and compromising shape integrity, I fabricated it using zero welding, or bolts. Pipes were staggard with reinforced hose connecting.

    I found this great material used for heavy machine belts that was 8 inches wide. My machine shop pressed out circular disks with three holes for the pipes in one step. I used epoxy and fiberglass to create terminations top and bottom that had thrust bearings incorporated.

    Instead of using a sleeve in the sail, I utilized straps sewn into the sail every 2 feet. These straps went around the three pipes equally spreading load to each. Well around is not correct. The straps went over one pipe and below the other two. This required assembly one strap and one disk at a time. Sewing on straps took about one hour each especially when factoring moving the sail. A diamond drill bit was used to get through the 3/16th inches of fabric.


    Overall this was a major change to solve how to fly and handle a very large crab claw style sail.

    Round one and the demasting in a South China Sea squall had utilized a spar in the foot and reefing was accomplished using a spilling line that lifted the spar up.

    This was problematic for several reasons
    1. The spar in the foot was solid instead of open. It both weighed and flexed too much.
    2. When reefing, the weight and load on the foot transferred up to the attachment point of the spilling line. This transferred all sail forces of the top of the mast.
    3. Further the force by the spilling line caused the 30 ft spar to bend.

    Solving problems and studying them carefully takes me a lot of time. In Thailand my time was divided solving many problems at the same time. That helped lead to basic mistakes on a very large rig like believing in thimbles, and not using 2 to 1 blocks at the top of the mast.

    It was disappointing to me not being able to test out this new spar as I believe I was near solving the key problem of compression.

    The open frame spar enable reefing by rolling the sail around a new upper spar. Instead of added compression caused by a partially raised spar in the foot and spilling line, compression load would decrease the more the sail was rolled.

    Further, an upper rolling spar was going to solve my stowage problem. Previously, I was lowering the entire sail to deck level and was attempting to roll the sail around the spar in the foot. I even built a cradle with rollers to assist in this effort. However, that wasn't good since the wind wanted to push the sail out and no lazy jack system was helping. The process took too long and still required too many hands.

    Some day I will write a book detailing further and publish the test results of actual measured compression force. I see on another thread sailors upset at paying good money to buy a rigging book that utilized no wind and sail forces.

    G forces for a trimaran versus other sailboats is now a new interest.

    The school of hard knock downs.

    For now I am working on putting my crab claw sail behind the mast paraw style. This enables me to have two spars in the sail and reef by lowering one spar to the other. Also see Wharram's Tiki.

    So except for questions, I am finished aft mast for a while.
     
  5. CT249
    Joined: May 2003
    Posts: 1,228
    Likes: 65, Points: 48, Legacy Rep: 215
    Location: Sydney Australia

    CT249 Senior Member

    But how do we know it is "nicely working"? The video is not raw footage, so it could be that they've just cut out chunks when the boat is not perfoming. It is also in very good conditions, with medium breeze and flat water, when just about any boat will sail OK.

    Secondly, the thinking behind the concept (chines just above the water, effectively concave sections under the chines, V hull, etc) are not new. They have been tried in development dinghy classes and other classes, and they have failed to show general superiority over other concepts. For example, the problem with having low chines just above the sailing waterline is that in a chop or swell, the boat gets pounded by the waves and ends up with a huge wetted surface and great beam, even in light winds. Similarly, the Vee hull sections work well in some situations but create excess wetted surface and reduced planing lift most of the time.

    When I google the boat I came to some claims that were simply wrong, and some that appeared to be very far fetched. For example, in a 2010 article the designer claim that there was "relative stasis in monohull design during the last two decades". But in 1990, the IOR boats like Stienlager II and Vibes still dominated grand prix mainstream ocean racing. Boats like the Mumm 30 and Melges 24 still hadn't been conceived. Water ballast was a novelty - canting keels almost unknown.

    Over that "last two decades" the speed of "grand prix" monos increased by about 20%. Some indications indicate that that's about the same speed increase that we saw in between the 1930s and the 1980s.......in other words, to claim that there was "relative stasis" in a time that saw a change from IOR to canters is completely over the top.

    It's an example of something that claims to be new because it uses concepts that have been tried and discarded before.
     
  6. Richard Woods
    Joined: Jun 2006
    Posts: 2,179
    Likes: 145, Points: 63, Legacy Rep: 1244
    Location: UK, USA and Canada

    Richard Woods Woods Designs

    Agreed "all boats are fast by themselves"

    His tandem keel was not a success but he did have a good publicity machine behind him

    RW
     
  7. sharpii2
    Joined: May 2004
    Posts: 1,867
    Likes: 86, Points: 48, Legacy Rep: 611
    Location: Michigan, USA

    sharpii2 Senior Member

    Attached is a scaled sketch of my first sailboat. It was a mast aft design.

    It probably was designed that way to keep the lee corner of the square bow from digging in.

    Absolutely nothing fancy went into her construction, just ordinary hardware store cable, lumber store lumber, 4 mil polyethylene, duck tape, and some quite crude craftsmanship on my part.

    Once I worked her bugs out, she sailed quite well.

    Throughout this very long thread, I have often wondered if optimum performance is being discussed rather than adequate performance. DELIGHLA, the boat pictured, certainly had the latter. She probably wouldn't win any upwind races with any production boats her size, but she could get me to where I wanted to go, and back.

    Even when we talk about optimum performance, are we mainly talking about such, sailing up wind?

    The production sailboat I once owned, a Siren 17, had a fractional rig. The jib had what was called a 'spool furling' system. It die not hank on to the fore stay at all. It had a wire luff, with a spool on one end, and a bearing on the other, which the halyard attached to.

    It sagged noticeably, even with the jib rolled up.

    The boat definitely pointed higher when the jib was furled, but went to windward faster, once it was deployed. Though there was quite a bit of head stay sag, it wasn't fatal to the boat's performance, though it probably would have been, in a race with a similar boat with a tighter head stay.

    Are we really arguing over the last 5-10% of performance potential?
     

    Attached Files:

  8. CT249
    Joined: May 2003
    Posts: 1,228
    Likes: 65, Points: 48, Legacy Rep: 215
    Location: Sydney Australia

    CT249 Senior Member

    Well, 5-10% of performance potential can be pretty significant. It's roughly the equivalent of having the performance of a 5-10% longer boat, in monos at least. A boat that loses that much performance would be inadequate to quite a few people.

    But the discussion here isn't just about whether a loss of performance of 5-10% (or whatever) is significant or not - it's whether the specific claims made for the rig are true.

    Unusual rigs and boats are wonderful things to have around IMHO, not just because they suit some people but because they add a lot of interest to the sport. Some of us are fascinated by boats like Pen Duick III, Cascade, Stienlager II.... there's even a wishbone ketch Int. 6 Metre actively racing. But it's one thing to love unusual rigs, and another to make far fetched claims for them that denigrate 'standard' sailplans and those who choose them.
     
  9. WindRaf
    Joined: Oct 2014
    Posts: 343
    Likes: 5, Points: 0
    Location: Italy

    WindRaf Senior Member

  10. DennisRB
    Joined: Sep 2004
    Posts: 1,265
    Likes: 24, Points: 38, Legacy Rep: 228
    Location: Brisbane

    DennisRB Senior Member

    I think the aft mast has its place. Like everything. But the notion that cruisers only sail downwind is only partially true depending on the cruising they do. From my experience its all about how much time you have to go cruising and where you do your cruising.

    A couple of years ago I had a year off to go full time cruising and purchased a mono in California and sailed it to Australia. This is a trade wind trip and we had time. We pretty much never had to sail upwind and went 1/3 around the globe. So in this case the notion that cruisers hardly sail up wind is true.

    But what about once we got back to AU and before we left? Well all cruising we have done here requires good upwind performance. We don't have a year to wait for the wind to change. We are sailing back to where we started. We WILL need to sail upwind.

    These two scenarios are pretty realistic. I would say the second one is far more common that the first though. So when I purchased my cat I got one which promised windward ability.

    Also its the "texas sharp shooter" fallacy to get data on windward miles sailed from people who's boats can not sail to windward. Of course you wont get many recorded miles to windward if the boats simply cant do it!

    BTW Brian. I know Sean at Monties marina, who has rigged his steel 45' to something close to your specs. I am sure you know all about it. I look forward to the results. This rig makes good sense on a boat like his where the windward performance is limited by hull design anyway.
     
  11. sharpii2
    Joined: May 2004
    Posts: 1,867
    Likes: 86, Points: 48, Legacy Rep: 611
    Location: Michigan, USA

    sharpii2 Senior Member

    What's pictured here is a Japanese boat built in a time when the powers that be deliberately limited the sea going abilities of their country's boats, as a way of staying isolated from the rest of the world. Japan, for a time, was quite insular, like North Korea is today.

    This boat is really a 'motor sailor'. The galleries are for sculling oars to stick out the bottom.

    Interesting to note there are no bow lines on this square sail. Such would make it easier to sail upwind. The rig really resembles that of a Roman Corbita.
     
  12. sharpii2
    Joined: May 2004
    Posts: 1,867
    Likes: 86, Points: 48, Legacy Rep: 611
    Location: Michigan, USA

    sharpii2 Senior Member

    I certainly wouldn't want a boat that could not sail upwind. By my definition such is not a real sailboat. A real sailboat can get to where ever it needs to go under wind power alone, given sufficient wind.

    But even sailboats that are quite mediocre from that standpoint have made windward voyages. A case in point is Fred Rebell's ELAINE which sailed from Sydney to Los Angeles.

    ELAINE was a 18 ft gaff rigged sloop, which had a gaff which was nearly as long as the luff of its main. This gaff was held at an angle of about 45 deg. from horizontal, and was nearly as long as the boom. It was hardly what anyone today would consider a good windward boat.

    I would think that a mast aft rig, even with only head sails, would be better than ELAINE in windward performance. And ELAINE was good enough to get the job done.

    It may not be as effective as a contemporary racing sloop, which is really intended to sail mostly up wind and down wind, but I suspect it would be more than up to the task, if properly designed.

    What I mean by properly designed is to have these four characteristics:

    1.) sufficient sail area for the displacement that the boat will actually end up with, and be able to stand up to such sail area,
    2.) sufficient lateral area for the hull and rig, at its aerodynamic dirtiest state (surfboards and bicycles lashed on the shrouds, dodgers and awnings),
    3.) proper alignment of such lateral area with the sail area, and
    4.) sails that have a straight enough luff to point into the the wind, without bagging.

    I contend that any sailboat that meets these four characteristics will sail up wind, even if its a square rigger. A jib only, mast aft rig, which meets them, should be able to do so quite well.

    The implication by some on this thread is that it would not.

    I think such implications are just as much exaggerations, as some of the claims of this rig's performance superiority over the fractional sloop.
     
  13. WindRaf
    Joined: Oct 2014
    Posts: 343
    Likes: 5, Points: 0
    Location: Italy

    WindRaf Senior Member

    Yes, true.
    But Roman was different: bottom round, more keel, sailing center not behind the center of buoyancy.
    The traditional Japanese boat was so because he had to have little draft and be much weather helm for great maneuverability in narrow water between the islands.
     
  14. DennisRB
    Joined: Sep 2004
    Posts: 1,265
    Likes: 24, Points: 38, Legacy Rep: 228
    Location: Brisbane

    DennisRB Senior Member

    My post was mainly directed at the notion cruisers dont sail to windward. This is false in many cases. Just because you might eventually make in to a windward destination in a boat with dismal performance is not a good selling point. Sailing is almost irrational as a transport choice besides the fact its enjoyable. And this sort of trip is not enjoyable to most, but sailing a good performing boat to windward can be enjoyable.

    I am sure it could be a good idea like on the shallow long keel steel boat that I know of a guy fitting the rig too. Now most cruising catamarans are known for crap windward performance anyway. So the rig should be fine on such boats for the same reasons (IE lagoons etc). Now for a cat with its already terrible windage, the addition of daggers, light weight design and an efficient rig, it can now sail to windward quite well. Now if you kept the light weight, daggers etc and used a aft mast rig. I bet it would still smash a lagoon to windward with its regular "racing" rig. But my bet is the people who chose those other factors also want a rig that improves windward performance too.

    But windage is always the major downfall to windward performance by the nature of a cruising cat. This only gets worse as the wind picks up and you need to reef, suddenly the hull windage has gone way up compared to the driving force. The aft mast rig is only going to multiply this effect. But many people dont care! Look at lagoon sales etc. Probably a valid choice for boats like this.

    So I am not knocking the rig in general. Just knocking the suggestion that if it is worse to windward "cruisers" should not care as they "dont sail to windward". Of course Lagoon owners don't sail to windward much, they CANT! For the data to be valid you need to ask people who own boats which sail well to windward how often they do it.
     

  15. CT249
    Joined: May 2003
    Posts: 1,228
    Likes: 65, Points: 48, Legacy Rep: 215
    Location: Sydney Australia

    CT249 Senior Member

    I'm not sure Elaine was a real slouch to windward. There are old articles describing how in one of the most popular and refined gaff racing classes, the 12 Sq M Sharpie, some sailors dropped the gaff from its normal fairly upright position to about 45 degrees in order to gain extra sail area.
     
Loading...
Forum posts represent the experience, opinion, and view of individual users. Boat Design Net does not necessarily endorse nor share the view of each individual post.
When making potentially dangerous or financial decisions, always employ and consult appropriate professionals. Your circumstances or experience may be different.