Subject: Not sent: Folding mechanisms, rudders, and plywood
From: Mike Crawford
Date: 1/20/2013, 3:21 PM
To: harryproa@yahoogroups.com.au


  Additional comments on current conversation threads


FOLDING MECHANISM

  I know I'm in the minority, but my favorite folding mechanism by far is the scissors beam system created by Raphael Francke for his Cat2fold catamaran.

    http://www.cat2fold.com/images/albums/5/5_6.jpg

  You can also see it in operation on the actual boat at:

    On-water unfolding:
    http://www.youtube.com/watch?v=n8eL2a_xqkc&t=99s

    Interesting mast raising system with "stub mast / tabernacle":
    http://www.youtube.com/watch?v=n8eL2a_xqkc&t=30s

   Reasoning:

    - It's proven and in use.

    - There's no worry about how much bury to have in a telescoping mechanism -- the entire beam is "buried" when you secure both ends.

    - It will allow for smooth folding and unfolding by one or two people, on the water, without worrying about one side jamming.

    - There are no worries about how to secure the expanded system in terms of allowing it to be tight without stressing the connection.

    - The whole beam will be quite resistant to wracking loads due to its height and connections.

    - No worries about how much free play to have in the mechanism.

    - Uses a standard winch handle to fasten two heavy-duty connectors per beam (the connectors taking primarily shear loads).

  Some will argue that this could add 50 kg to the boat versus telescoping beams.  Maybe more.  I won't argue against that.  Plus, there's a fee to Raphael of probably about $1,200.  For me, though, the benefits far outweigh the costs.  Just seeing him expand that boat on his own at the launch ramp has me completely sold. 

  If I ever wanted to transport the boat, I'd want a similar three-axle trailer (see the video from the start), and would definitely want a fixed trailer with the boat expanding and contracting on the water.  I have an expanding trailer for my current multi, and it's just a grand pain. 

  Likewise, if I were to pull into a monohull slip, I'd want to do the folding on the water as well.  Both ways I'd want to do it either alone, or with my wife's help.  There aren't many systems that could claim to allow this to happen.


FOILS

  I'm also not sure there's an problem with the newest version of the beam-mounted kick-up foils, *if* the boat design works with them.  BD has special draft requirements, as does Gardiner's plan to sail in the Chesepeake, and both could be nonoptimal with low-draft beam-mounted rudders.

  With another 1' to 2' in rudder draft (4' to 5' total), a schooner rig that allows different sail balance, and Rick's hard-chined flat-bottomed leeward hull form, leeway, tracking, and steering should become the same non-issues that Rob had with Elementarry.  Particularly if I go with wingsails that create more drive and less force to leeward.  This might even work at 3' draft with the rudders partially raised, but that remains to be seen.

  [many, many thanks,at this point, to go Rob, Mark, Bain, Nol, Arttu, and Johnny for all the real-world experience to date]

  There's no denying that foils in drums, exiting the hull bottom, would be more efficient.  But I just can't imagine spending the money it will take to build a 48' boat and then going with foils that don't kick up. 

  In fact, I don't even want to spend the money on a used Corsair for that reason.  I know of a boatyard that has repaired the same boat F32 three times due to encounters with rocks.  You could say that's due to bad choices, but sometimes groundings happen due to events outside of the boat owner's control.

  On a more personal note, I've had a friend run my own catamaran's central daggerboard into rocks at 2 knots, and that just required a few hundred dollars of repairs.  If it had been at ten knots, I'd have needed a new centerboard, centerboard bracket, and cockpit deck.  And if it had been in a trimaran instead of a cat, we might have filled the main cabin with water.  And if it had been at sea...

  Most folks will put up with well-established risks, such as daggerboards in trunks, multihulls that can't be righted if they capsize, or complex masts with 50+ points of failure in terms of standing rigging and connections.  But if we're going to go non-standard with a proa in the first place, why not go all-in and eliminate all of the risks and shortcomings we can?

  If I were to get a trimaran, it would be a Dragonfly.  Period.  Because their centerboards and rudders will both kick up if run aground, turning a high-speed grounding from a potential sinking experience into merely an inconvenience.  There's just no way to put a price on that, particularly if you're out of sight of land. 

  But since the Dragonflys' diamond-stayed rotating masts have many dozens of points of failure, and they don't even stand a chance of righting after a capssize, a schooner Harryproa with sealed unstayed masts currently occupies the top slot in my short list.

  In any case, when the time comes, I'm going to risk the beam mounted rudders; risk in the sense that I could end up replacing them with a different system. 

  Just as important, rudders on the beam would permit simple tiller extensions all the way to the cockpit, which is something I'd definitely like to try.  It's a simple system that wouldn't care one way or the other if the boat were folded or unfolded, won't stretch out of shape, and will be more fun than using a wheel.  At least for me -- I much prefer tillers.

 
PLYWOOD

  Plywood gets a bad rap.  I know it's heavy, more prone to rot than a good foam core, and more labor-intensive than a KSS build, but it's an amazingly strong material. 

  I'm currently doing some destructive testing on glass/kevlar/epoxy plywood panels, and I'm astounded at the abuse it can take when compared to a normal foam-cored hull. (I'll get around to posting photos and videos someday, hopefully by the end of the year).

  This doesn't mean I'd go with plywood, but if you're building what's likely to be a one-off design, and you're not planning on a showroom mirror finish, there's a lot to be said about this material.  Still relatively light, and yet tough as nails.  There's not much else I'd want under me when getting bounced off a granite shoal. 

  Plus, if you have someone CNC rout the panels, including step-scarfs, you save on a serious amount of labor.

  The end result wouldn't compete with an Formula 40, but it might compete with a Corsair, and it would be a heck of a lot tougher than both.  If done with the right lines, it would even look good.  Plus, as the Wharram folks like to point out, repair materials for plywood boats can be found worldwide without much time or effort.

        - Mike


nk wrote:
 
Two thoughts on the survey results.
 
Number one if there really are folks still thinking plywood I would strongly urge them to have a much better look at the KSS site and really spend some time reading.  I just can’t see any reason to build in wood unless you want a very quick build that you plan to destroy within a year.  For all other reasons KSS method has got to be superior.
 
Second when Rob has time I will be happy to have him share the plans he is working on for me.  I am unlikely to have the time or money to build my boat for another few years so I would be more than happy for you all to exam and give feedback on my and Rob’s ideas. I believe it could be the answer to relatively easy trailering.
 
Nick