Hi Dennis,
I am actually living in Oz. I am living in Canberra but trying to get back down to living at Eden on Twofold Bay.
The sliding system I am working on is based on low friction surfaces and winches, but was intrigued by the possibility of treating the beam as a piston and pushing it in and out by air pressure and also the idea of a rack and pinion.
The main set positions can be graphite epoxy and the sliding positions just needs to be low friction. The design uses a slight wedge shape lashed into a matching wedge.This gives a bit of clearance when not lashed

--- In harryproa@yahoogroups.com.au, Dennis Cox <dec720@...> wrote:
>
> Robert,
> Where are you located?  UK email address?  I was lead to believe that your
> highway restrictions were far stricter than US restrictions.   They appear to be
> about the same.  Although with our litigation rich society, keeping under the
> 8.5’ width seemed “safer” to me.  I would like to “land sail” to both sides of
> the continent.  Fastest Proa ever… 85 mph through Kansas! 
>
> It sounds like you have worked the kinks out of the sliding thing.  I tried to
> come to grips with it, for I’d like to narrow for a slip, lock or motoring
> occasionally.  Either lots of friction or lots of rollers that are rarely used. 
> If metal, you have rust, if any “plastic”, you have long term, high load creep. 
>
> That’s the beautiful thing about these Proas… Decoupled Here I’m wood stripping
> a hull and I haven’t even decided on mast number and position.  Couldn’t have
> begun to do that with a catamaran and certainly not a monohull.
>
> Dennis
>
>
>
>
> ________________________________
> From: robert <cateran1949@...>
> To: harryproa@yahoogroups.com.au
> Sent: Tue, July 27, 2010 11:04:40 PM
> Subject: [harryproa] Re: 60' Trailerable Proa
>
>  
> I can trailer it at the 4.2m width but would require permits etc. The 4.2m
> telescoping is to reduce width in launching, marinas and narrow waterways. For
> extended towing, it can be separated and towed at 3m wide and 15m long,
> requiring wide and long load signs but no special permits but there are time
> restrictions. The ww hull is to be 3m wide and the lw hull 1.2m. This gives
> about 700mm bury in the w hull when expanded. I played with a few designs for
> folding but wanted to be able to leave the mast stepped when collapsed. A very
> rough concept diagram is in the files under Robert's Harry.
>
> --- In harryproa@yahoogroups.com.au, Dennis Cox <dec720@> wrote:
> >
> > Robert,
> >
> > Does that mean you trailer it at the 4.2m width?  That should make it far
> >easier
> >
> > to rig.  I'm looking at a half day rig time at best.  That sounds like same
> > dimensions (except width) of a Visionarry.  Did you start from Rob's plans? 
> >Are
> >
> > you sliding for the extra width or doing some kind of Ferrier jointed
> > articulation?  Do you have pictures posted?
> >
> > Dennis
> >
> >
> >
> >
> > ________________________________
> > From: robert <cateran1949@>
> > To: harryproa@yahoogroups.com.au
> > Sent: Tue, July 27, 2010 8:09:21 AM
> > Subject: [harryproa] Re: 60' Trailerable Proa
> >
> >  
> > Thanks Dennis,
> > I can't give any definitive argument either way. I designed a small schooner
> > Atlantic proa and it made sense. I am going for the Harry configuration for my
>
> > 15/10 Harry as the boats work and the stresses seem to have been worked out.
> > I have designed mine to be able to sail gently at 4.2m wide and stretch to 6.5m
> >
> > wide and be easily trailable with a long load sign and wide load sign.
> > regards,
> > robert.
> > PS I am Robert and Harryproa Rob is Rob.
> >
> > --- In harryproa@yahoogroups.com.au, Dennis Cox <dec720@> wrote:
> > >
> > > Hey Mike, et al.
> > >
> > > I have the greatest respect for Robert's HarryProa.  I am certainly not
> > >implying
> > >
> > > any superiority of the Atlantic design.  In fact, most of the reasons are
> >not
> >
> >
> > > performance related.  Also, its interrelated with the steering leeway
> > >resistance
> > >
> > > issue.  I am hoping someone here might take pitty on my fence riding
> > >and give me
> > >
> > > something definitive that tips the scale either way for good... but hear me
> > >out,
> > >
> > > because these are the things that am pushing me toward the Atlantic.
> > >
> > > Non Performance Reasons
> > > These are reasons that have to do with the trailerable aspect or for me
> > > personally.  They have nothing to do with one design being superior to
> >the
> >
> > > other.
> > > * When on the trailer, the first thing, I'd step the masts on the windward
> > > hull.  As you suggested, I was thinking of a relatively small "crane"
> >based on
> >
> > >
> > > the cheap car engine hoists.  Once up, these can be used in conjunction
> >with
> >
> > >the
> > >
> > > boats winches to lift the windward hull up and over and down. 
> > >
> > > * I've been watching a lot of Rick Willoughby's comments.  If I keep the
> > > leeward hull simple (without) mast and leeway prevention structure, I can
> >make
> >
> > >
> > > it quite cheap.  The one I'm making now should come in complete for less
> >than
> >
> >
> > > $2000 and somewhere around 800 pounds if I don't get sloppy.  The point
> >being,
> >
> > >I
> > >
> > > could very easily make a second one using the squared off sheet hulls that
> > > Rick's research suggests may have a superior performance edge.  It may go
> >for
> >
> >
> > > less than a $1000.  IOWs, I can play Mr. Potato Man. 
> > >
> > > * The lee hull is lighter - for getting off the trailer and moving it
> > around. 
> > > Structural
> > > IMO and for a schooner rig, one design has no significant advantage
> >over the
> >
> > >
> > > other.   
> > > * In a HarryProa or an Atlantic Sloop the mast loads have to be
> >transferred
> >
> > > from the mast base to the cross beams by torquing the hull.  In an
> >Atlantic
> >
> > >this
> > >
> > > would make things far more difficult.  It fully justifies Robert's
> >statment
> >
> > > about being able to make the unstressed HarryProa windward hull far lighter
> > >than
> > >
> > > the Atlantic.  It would be clearly lighter.  However, in
> >a HarryProa or
> >
> > > Atlantic Schooner there is no torque in the hulls.  If the masts are
> >mated to
> >
> > >
> > > the cross beams all moments from the masts can be directly transferred into
> > > cross beams.  My contention is that both hulls could be made lighter in a
>
> > > schooner rig and frankly there would be no advantage of one over the other
> > >(that
> > >
> > > I can imagine yet). 
> > >
> > > * The largest moment in the beams of a HarryProa (and thus largest cross
> > > section of the beam) is at the base of the leeward hull.  In an
> >Atlantic, the
> >
> > >
> > > largest moment in the beams is at the base of the windward hull.  It is
> >helped
> >
> > >
> > > out by a significant structure... the bridge deck.  The beam (in an
> >Atlantic)
> >
> > >as
> > >
> > > it goes into the lee hulls has nearly no moment... just shear.  It can be
> >much
> >
> > >
> > > smaller and thus offer less resistance to waves and submerging.
> > > * I hear what has been said about leaning the mast out and keep the
> >boat from
> >
> > >
> > > going past 70 degrees.  I can easily see that in Robert's smaller
> >designs. 
> >
> > >I'm
> > >
> > > having a little trouble with it for a 10,000 lb boat.  Mast tend to come
> >away
> >
> > >in
> > >
> > > roll overs.  It is said any mast that doesn't... is way over built and way
> >too
> >
> > >
> > > heavy.  In my minds eye, a boat traveling 20+ knots and has flipped at a
> >rate
> >
> >
> > > that the helm couldn't save must have significant angular velocity.  When
> >the
> >
> >
> > > mast and sail slaps the water, IT will come to a dead stop while the linear
> >and
> >
> > >
> > > angular inertia of the rest of the boat (27 feet up in the air) is
> >certainly
> >
> > > going to continue... result (I believe) is a snapped mast and flipping of the
> >
> > > hulls.  Arguably, the HarryProa having a little chance is better than
> >no
> >
> > >chance
> > >
> > > at all with an Atlantic. 
> > >
> > > * This may be a cardinal sin, but, I'm debating about putting the rudders on
>
> > > the windward hull also... see
> >>http://au.groups.yahoo.com/group/harryproa/photos/album/1001384692/pic/461401281/view?picmode=&mode=tn&order=ordinal&start=1&count=20&dir=asc 
> > 
> > > 
> > > Structurally, I can tie all the major force producers into one
> >structure. 
> >
> > >See
> > >
> > > more in fluid dynamics section.
> > > Fluid Dyanmics
> > > Out of my comfort zone, but...
> > > * I guess the heeling moment does get larger with an Atlantic when flying,
> >but
> >
> >
> > > only as a result of exposing the bottom of the hull in addition to the sail
> > > forces, while a HarryProa windward hull shields the sail somewhat.  But in
> >
> > >this
> > >
> > > size of a boat, I don't really thing exposing my bottom is really
> >in the game
> >
> > >
> > > plan... unless I've unloaded all the soft personnel and am racing.  And
> >even
> >
> >
> > > then, I wouldn't be flying... just kissing.
> > > * The main one that drove me toward a Harry Proa is the significant decrease
> >in
> >
> > >
> > > COE by lowering the base of the masts to the lee hull.  At first this was
>
> > >clear
> > >
> > > cut.  HOWEVER, strangely enough, if I go to wings or oversize wing masts
> > >(still
> > >
> > > debating that one also) the heeling moment is far less than a sail.  My
> > > calculations show I can not get the lard-ass, windward hull up so I can
> >get to
> >
> > >
> > > the 25+ knots Michlet says the lee hull could do if unburdened.  So in
> >this
> >
> > > strange case, its better to put the masts up on the windward hulls to
> >actually
> >
> >
> > > encourage heeling.  Yes, I know, I could put larger wings/sails on the
> >leeward
> >
> > >
> > > hull, but that adds to the trailering issues. 
> > >
> > > * If I put the rudders under the mast bases (on the windward hull) all that
> > > splashing and spray as seen on the all the videos, is under the bridgedeck
> >and
> >
> >
> > > we have a cleaner view from the bridgedeck overlooking the lee hull.
> > > * With the rudders on the windward side, flying the hull reduces leeway
> > > prevention and thus lets it slide.
> > > I think that's all, but I'll bring up more, when they hit me.  HELP! 
> >Stop
> >
> > >the
> > >
> > > voices.
> > >  
> > > Dennis
> > >  
> > >  
> > >
> > > ________________________________
> > > From: Mike Crawford <jmichael@>
> > > To: harryproa@yahoogroups.com.au
> > > Sent: Mon, July 26, 2010 5:07:09 PM
> > > Subject: [harryproa] Re: 60' atlantic proa
> > >
> > >  
> > > Dennis,
> > >
> > >   That is extremely cool.  Thanks for pointing out the video link. 
> >You
> >
> > >could
> > >
> > > probably do this with a purpose-built trailer and a stub mast in a separate
> > > socket (1/3 full mast height, used to lift the primary mast at its center of
>
> > > gravity) , no crane required. 
> > >
> > >
> > >   Now I *really* want to see you build it.  I've said many times that i
> >want
> >
> > >the
> > >
> > > largest trailerable boat I can get, and this would certainly qualify. 
> > >Actually,
> > >
> > > I'd be willing to put up with a 12' width, but fitting into 8.5' is even more
> >
> > > impressive.
> > >
> > >   I had actually brought up atlantic vs. harryrproa in a post right before
> >the
> >
> > >
> > > one you responded to, but for some reason the post didn't make it.  (thus
> >my
> >
> > > comment about ignoring my question about how the boat goes on the trailer).
> > >
> > >   I'm partial to the harryproa design for the following reasons:  a)
> >more
> >
> > >space
> > >
> > > in the windward hull,  b) heeling moment decreases, or remains the same,
> >as
> >
> > >you
> > >
> > > fly a hull, while heeling moment increases with the atlantic design,  c)
> > > stresses are in line with the hull, while the atlantic has to translate rig
> > > stress through the beams to that long leeward hull, and  d) the
> >possibility of
> >
> > >
> > > popping back up after a knockdown.
> > >
> > >   As far as handling the sails, a leeward design might offer more safety
> >in a
> >
> >
> > > schooner configuration (from the tramp), while a single mast would probably
> > > offer safer sail handling with the atlantic (from the cockpit).
> > >
> > >   But I'm sure you're familiar with all that.  Your design has more
> >than
> >
> > >enough
> > >
> > > space to deal with masts in the windward hull, and the taller leeward hull
> > > needed for a rig there might get in the way of your trailering setup.  As
> >long
> >
> > >
> > > as you don't sail on the very edge, there shouldn't be any issues.
> > >
> > >   I wouldn't put on a pod for safety as cavalier suggests.  If you're
> >sailing
> >
> > >an
> > >
> > > atlantic proa hard enough to fly a hull, in anything other than flat water,
> > > there's a good chance you'll be going fast enough to trip over any pod small
>
> > > enough to justify its own weight penalty.
> > >
> > >   What are you planning for steering and leeway resistance?
> > >
> > >         - Mike
> > >
> > >  
> > > On 7/26/2010 2:43 PM, Dennis Cox wrote:
> > >  
> > > >Hey Mike,
> > > >
> > > >Did you see the video... on post #9.  It might clear things up. 
> >Unless
> >
> > >you've
> > >
> > > >already seen it... :)
> > > >
> > > >Also, I'm still bouncing between Atlantic and HarryProa placement of the
> >sails
> >
> > >
> > > >(windward, leeward hulls).  I've got pros and cons on both sides and the
>
> > >tally
> > >
> > > >list is still balanced.  Fortunately, the hulls and internal
> >configurations
> >
> > > >don't have to be changed either way.  So... I've got PLENTY of time to
> > >decide. 
> > >
> > > >
> > > >
> > > >Dennis
> > >
> >
>

• New Members 2
• New Photos 23
• New Files 1