<< I am certainly not implying any superiority of the Atlantic design>>

  Hey, no worries even if you are.  They are both impressive ways to have one's cake and eat it too.

  Please note that none of this is an argument for Rob's Harryproa design.  I'm just a fan of being as safe, simple, inexpensive, and fast as possible, and most of Rob's design elements work for what I'd like to do.

  At this point, arguing atlantic-vs- harryrpoa is almost like splitting hairs.  But that's what forums are for!

  Perhaps your ideas will infect my brain, and I'll end up pining for an atlantic rig.  Actually, most atlantic proas don't appeal to me, so it's not the rig that would sway my building plans.  I'm sold on the leeward rig.

  What would cause me to consider an atlantic rig is the fact that you've solved one issue that is close to being a showstopper for me: how to have a trailerable multihull with an enclosed saloon, where my wife and daughter can stay warm while I'm out enjoying a nice fall or spring sail.

  Rig now the family debate is between an Etap 32 monohull (the next boat *must* be unsinkable) and a Harryproa.  On July days when it's 80 degrees, my wife and I are both for the proa.  But as soon as the temperature dips down to 70, which means it will be cooler on the water, My wife is set on the boat with a heated saloon.

  Since I'm not willing to spend $350k on a Dragonfly, and wouldn't want to deal with a stayed rig even if I did have the extra cash, that puts us at an impasse.  There's no real argument going on, but we're also not making any decisions either.

---

  My current ideal boat would be your design with a leeward rig, even if that means going to a 10' or 12' trailering width.  I'd trail the boat so little, mostly just once in the spring and once in the fall, that I wouldn't mind getting the wide load permit.

  I would probably go with scissors beams like cat2fold, which would keep the boat together and vertical while expanding or contracting on the water.  Rafe Francke quoted me $2,500 for a license to his patent to build a boat, and that's something I'd be willing to pay in this case.  With the scissors beams and a wider collapsed width, the leeward hull can stay upright and "structural" .  In this case, putting the rig into the leeward hull versus the windward hull probably wouldn't make much difference in terms of setting it up or breaking it down.  It would also be nice to be able to collapse the boat on the water to fit into a slip, if needed.

  Most people seem to be planning on telescoping beams, saying they'll cost less, and that they will be more than stiff enough.  I can't imagine them being as stiff as the scissors beams (though they will be lighter), while also being easy to expand and collapse, but I'm not going to argue with anyone.  I'm sure they'll both work, and I'd always welcome the chance to be proven wrong by Robert's upcoming build.

  The 8.5' design limit would probably preclude leaving the leeward hull attached, though.  You could still use the scissors beams, but you'd have to demount the leeward hull to trail the boat.

  In any case, it's a beautiful boat.  I must confess that the low, skinny leeward hull is particularly appealing.
 
        - Mike



On 7/26/2010 7:17 PM, Dennis Cox 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@gwi. net>
To: harryproa@yahoogrou ps.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