|Subject: [harryproa] Re: Mast raising|
|From: Mike Crawford |
|Date: 7/3/2006, 10:27 PM|
How would the boat float with the hull on its side like you describe?Cheers,Peter----- Original Message -----From: Mike CrawfordSent: Monday, July 03, 2006 1:27 PMSubject: [harryproa] Re: Mast raisingHey Robert,
How is the new job?
The support system you describe should work well if the lw hull is stored upright next to the ww hull on the trailer. For a Visionarry, though, that puts me about 20cm past the unescorted wide load limit, so one or both hulls would have to get a bit narrower.
The idea of storing the lw hull on its side, beneath the wing deck, makes supporting the ww hull more of a challenge, but kills two birds with one stone: neither hull has to change size, and the lw hull is already on its side ready for the mast. It does get away from my dream of collapsing the boat on the water and floating it onto a standard trailer, though.
Since the beams aren't parallel to each other and perpendicular to the hulls, I'm having a hard time imagining how an Farrier-type system would work. The same geometry would also make it difficult to use the Dragonfly system. The only one that's making sense to me at the moment is the cat2fold scissors system.
However, I'm sure there are other ways to accomplish the goal. My only doubt involves a tilting/folding system. Unless the trailer could take the boat out sideways, or I could remove the mast while on the water, that could make it very difficult to launch from anything other than a wide open ramp.
Is the dream worth it in terms of added weight, complexity, and chances for failure? I'm not so sure. Of course, my goal is to use the trailer only two to four times per year, so that makes the inconvenience of box beams and a funky trailer less of an issue.
Are there any photos, CAD images, or links that describe Jim Shanahan's system in more detail? I found a few references to it in early posts, but haven't seen anything that describes how it works. One message mentioned something about being lighter and stronger than conventional beams. If so, that would be impressive. The righting aspect is also intriguing.
Robert wrote:-G'day Mike
I was thinking on similar lines but don't se much problem holding up
the ww hull. There is not an enormous weight off centre and a
vertical bit of box section on the ww side triangulated at the base
should provide enough support for the hull with a couple of tie down
straps to hold it against. Either that and/or a support under the
junction of the wing deck and hull. This would have to be to the lw
side of the c of g.of the www hull on its own.
If the crossbeams had a temporary controlling system such as a
farrier wishbone with a sleeve to allow sliding of the crossbeam, or
even a complete folding system as designed by Jim Shanahan then the
only difficulty is moving the lw hulls off the trailer and onto a
trolley as everything else can be controlled with a couple of
winches. Jim's system makes a lot of sense and would even allow
righting from a complete overturning.
My personal preference is to launch a folded system where the boat
can then be brought side on to shore and the mast then inserted-
possibly with sail attached. The crossbeams get winched out with
water supporting the system and you're away.
I have tried to imagine taking the folded boat out onto the water
and inserting the mast from the water. It seems theoretically
possible but would probably be excessively difficult in practice.
On another issue, I was wondering if there was any wat to get round
the dependance on carbon for making a free standing mast without
excessive weight. The closest I could come up with was , while
looking through a website on making bamboo fly rods, the testing of
tensile and compressive strengths and Young's modulus of strips of
bamboo. Rough calculations give a mast made of quality bamboo strips
a weight of about 2.5 times that of carbon. The technology for
utilising bamboo has come some way to making this practical, but
organising supplies off stream from flooring manufacturers would be
-- In email@example.com, Mike Crawford <jmichael@g...>
> If you can keep that leeward hull in place as it rotates from
> horizontal to vertical, then there shouldn't be any problem with
> size of the mast. Given the length of the beams, a #14 winch at
> should be enough to bring the leeward hull into place with a 22m
> mast. Though I'm not familiar with the size of winches used on the
> Harry's, my guess is that you'll have at least a #14, which is the
> smallest self-tailing size offered by some vendors.
> If this is not enough, it would be simple to double the purchase
> a block. If you want even more than 32:1, then you could have a
> line going from the trailer to the first beam, back to the trailer,
> to the second beam, back to the trailer again, and then up to the
> winch. That might be even be enough to lift your tow vehicle if
> some muscle into it..
> For me the question then becomes how much help you're willing to
> require. If you can get a few people to lend a hand, then the
> setup described in the article should be fine. It's certainly the
> simplest and cheapest way to go, and there's a lot to be said for
> I'd probably choose to spend more on a trailer to help ease the
> process, though. This would be partially to save on boatyard
> partially to allow two people to launch in areas that don't
> have paid help.
> I think even a Visionarry could be kept to an 11' / 3.3m
> width if the leeward hull could be stored on its side on the
> beneath the cockpit. My first thoughts on this would be to:
> - Create a bunk that could hold the ww hull upright on its own,
> - Create a detachable moving bunk for the lw hull with its own
> wheels that could be lowered and used to move the hull out away
> - Add two long horizontal arms that could be used to hold the
> hull in place the proper distance away from the ww hull, as well as
> the trailer assembly together when launching and retrieving the
> - Give the lw hull bunk assembly the ability to pivot to
> without sliding towards the ww hull and trailer,
> - Add some sheet blocks to the trailer and akas through which
> winch line can be run,
> - Add two short vertical arms with soft rollers that could be
> inserted into the main trailer and used to catch the beams as they
> rotate down to horizontal,
> - Add some block attachment points to the lw hull so that it
> winched tightly towards the ww hull once the beams are in place.
> I'm not exactly sure how this would be done in a real world
> The bunk keeping the ww hull vertical would need to be pretty
> especially if it's going to hold everything in place while on the
> Perhaps it could be supported while by the lw hull bunk once it is
> place under the ww hull, and by a temporary support arm under the
> cockpit when the lw hull bunk is away from the main trailer.
> The lw bunk might need a roller bearing and expansion arm/track
> support it until it is moved far enough from center to get the
> wheels down (assuming the outboard wheels can be dropped while the
> trailer is still whole). The wheels would also need to pivot 90
> to make the transition from assembly to launch. Alternately, there
> could be two sets of wheels, but that seems a bit excessive.
> Ideas on how to improve this setup, especially on how to make
> hull bunk work, are welcome. I don't mind seeing my ideas trashed
> long as something better results. Rob could probably solve this in
> weekend if I were actually building a boat, but I've got five years
> of lurking in this group before I get to that stage.
> - Mike
> oceanplodder2003 wrote:
> > Saw that, my concern was at what mast length would it become an
> > considering that if I go for Rob's una rig I'm assuming the mast
> > be taller, and I think Harry's is longer than Harrigami to begin
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