I'm still having a hard time seeing how Farrier-type system would work on the water without adding a lot of structure and complexity, and/or dumping hull sides into the water.  Telescoping beams are also a challenge. 

  To me, it's almost a choice between one-piece tapered beams (lightest, simplest, cheapest, strongest, fewest failure points) and a scissors system. 

  I'll admit that I'm biased towards a scissors system, but that's because it looks to be the simplest and most reliable way do everything I'd like, particularly folding singlehanded while on the water, perhaps with some chop and wind action.

  If there's a simpler, lighter, or less expensive solution that still makes that possible, I'm happy to dump the scissors in favor of something else. 

---

SCISSORS BEAMS

  First, here are examples of a working scissors beam system on a catamaran:

    https://youtu.be/eQwoq5AlPcg  -  folding test of bare hulls.
    https://youtu.be/n8eL2a_xqkc?t=316  -  final boat, launch
    https://youtu.be/n8eL2a_xqkc?t=339  -  final boat, expanding
    https://youtu.be/n8eL2a_xqkc?t=455  -  final boat, installing the locking pin
    https://youtu.be/n8eL2a_xqkc  -  final boat, full video

  The system used by Dragonfly on its trimarans is the closest thing to this in terms of folding a large multi, on the water, with one or two people, and then being able to leave it on the water with vertical hulls.

  But even then, I trust the scissors beams more because the mechanism for keeping the boat square (massive pins in the beams) is so strong.  You'd have to lose both pins on a single beam for it to start to collapse.

  So, this scissors is my gold standard for the sake of comparison. 

  If something were to be lighter or cheaper, I'd consider it, but only if it offers all the pros -- I personally wouldn't be willing to give up any of the strong points in order to save weight or money.


  PROS:

    - Proven.  A working example exists and has been in use for years.

    - Singlehanding.  One person can collapse or expand the boat, on the water, without issues.  It might take a few minutes, but there's no drama.

    - Smooth.  No issues with beams jamming because the hulls aren't parallel.

    - Vertical hulls.  The hulls stay upright during the entire process, and can stay that way while folded in a marina.

    - Length and height.  The boat doesn't get appreciably longer or higher, allowing trailering and marina storage.

    - Standard trailer.  No need for an expandable/collapsible trailer.

    - Structure.  No additional structure required to handle the folding system.

    - Strength.  Four big hinges, two big pivot pins, four big locking pins, no small parts that are going to fail either collapse the boat or prevent folding.  No small metal parts that will go due to fatigue, stress fractures, crevice corrosion, or casting voids.  No exposed struts to be caught by logs or other debris.
   
    - Resistance to working loose.  Once the locking pins are in place, the beams become one solid piece.  There's no line to hold under tension to keep the boat in shape.

    - Failure modes.  It's going to be tough to induce a failure where the boat collapses unintentionally.  The locking pins are huge, gravity will hold the pins in place if they work themselves loose, and one pin on each beam could fail without the boat collapsing.

  CONS:

    - Weight.  The scissors beams are probably going to weigh twice the tapered beams.  Though as a percentage of boat weight that's not too bad.

    - Cost.  The beams are more complex than tapered beams, plus there's a $1,200 fee if you want this exact system.


SIMPLEST - TAPERED BEAMS

  If the only goal is trailering, there's a lot to be said about a flatbed trailer, two trolleys for launching/retrieving, and one-piece tapered beams.

  This is the lightest and simplest you're going to get, perhaps the strongest as well, and definitely the cheapest.  There's nothing to fail while on the water, the hulls stay upright, there's no additional structure required, and there are no worries about collapsing the boat in a non-parallel fashion and jamming the beams.

  That said, I'm too lazy to do the trolley thing twice a year, particularly since the boat ramps near me don't have enough space for it.  Maine has very few beaches with gradual slopes near the water.


TELESCOPING BEAMS

  This would come in second in terms of cost and complexity.  If you're really careful, or come up with some system that keeps the hulls parallel, you could collapse the boat on the water.  I don't know how easy it would be to do single-handed, but it would be an option.

  That would also let you use a standard fixed boat trailer, albeit one designed for a longer leeward hull.

  Or, you could use a collapsing trailer the way the Stiletto and Reynolds catamarans do.

  PROS:

    - Cost.  The second cheapest option.

    - Weight.  The second lightest option.

    - Simplicity.  The second simplest option.  No hinges anywhere.

  CONS:

    - Collapsible trailers.  I have a Stiletto with a collapsible trailer, and it's so difficult to use that I pay a boatyard for storage each year.  Getting everything to collapse, keeping the hulls parallel, and maintaining the trailer is a serious pain.  The only time I want to do that again is when I sell the boat to build a proa.  Or, hopefully not even then.

    - Jamming.   It would be pretty easy to jam the beams if you're trying to collapse the boat on the water and there's a bit of chop.

    - Singlehanding.  I'd like to collapse the boat on the water single-handed, either for a marina, or more likely, for launching and hauling it with a standard trailer.  Where I live that could save me $5,000 per year in yard storage fees for a 14 meter proa/cat.



PARALLELOGRAM HINGED BEAMS

  Beams hinged on each end that allow the hulls to move together, the way the amas collapse on a Dragonfly trimaran, could work.

  PROS:

    - Relatively simple.  Only four hinges, all of which can be beefy.

    - Strong.  One-piece beams.

  CONS:

    - Length.  The boat gets long when collapsed.  Probably too long for trailering or marina storage.

    - Resistance to working loose.  The diagonal struts/lines that hold the boat in shape may lose tension over time.

    - Failure modes.  If the lines that hold the boat in rectangular shape go, it's a bad day.  I suppose you could have multiple struts and lines, but sailing forces are going to want to collapse the boat.  You could add diagonal struts to aid the lines, but now that's additional weight.


 
DRAGONFLY SYSTEM

  We could always build a central structure to allow each hull to fold against a center hull without the boat getting as long.  That works quite well for the Dragonfly's.

  But now we have eight hinges and a third hull/cabin/box/pod.  That's a lot of extra weight and structure.  Why not build a tri?

  PROS:

    - Proven.  It works, on the water, with big boats.

    - Smooth.  No drama.

    - Vertical hulls.  The hulls stay upright and dry.

  CONS:

    - Complexity.  Eight hinges and a third hull/box/cabin to which to attach the beams.

    - Width.  The central structure will take up space when collapsed.

    - Weight.  That's a lot more structure than scissors beams, particularly when you consider how strong the central structure and hinges will have to be to handle flying the windward hull with an unstayed mast to leeward.

    - Failure modes.  As with the Dragonfly system, sailing forces will want to collapse the boat, and there's not a whole lot of redundancy there.



FARRIER SYSTEM

  I'm having a hard time seeing how this could work on the water if it's built as on the Farriers and Catri.

  PROS:

    - Proven.  Many, many examples.

    - Weight.  Pretty simple.

    - Failure modes.  If the akas come unpinned, the boat will still want to hold its shape while sailing.

  CONS:

    - Non-vertical hulls.  Folding puts one of the hulls on its side in the water, and I don't want to put either the mast or the cabin on its side. 

    - Non-vertical hulls.  Since the hullsides are in the water, we need to make sure there's nothing to leak (no windows underwater, decks that can act as sealed hullsides when sideways).  The ulls will also need antifouling paint, and will look sloppy when expanded even with the paint.

    - Non-vertical hulls.  That boat is going to have a hard time balancing on the water because there's no centra vaka to stabilize it.

    - Complexity.  Each aka also has aluminum struts, pins, and hinges.

    - Failure modes.  Those small metal parts could go.  Or the tiny struts could get hit by a log.


PANTOGRAPH FARRIER SYSTEM

  It technically would be possible to create a Farrier system, with a central hull/cabin/box/pod with arms to each hull, that would then keep those hulls vertical.  But that's a very complex endeavor. 

  Eight beams (or four complex beams), sixteen hinges, metal parts, a central pod that can handle sailing forces while flying a hull... 

  It's got most of the cons of the Dragonfly system and the Farrier system combined.  Plus the boat gets taller when folded, and will likely not be withing trailer height limits.

---

  Options increase a lot if you don't care about folding on the water, but if that's a requirement, it's going to be hard to top the scissors.

        - Mike

 

Before your guys find out there is a better way to FFS a HP.

Reversing the folding beams seems to be much easier. Hulls stay right up. Only need strong pivots in the central "toybox". Picture of so butchered catri-24 is worth ten tweets.