In response to your PS, here's a
general description off what I want to do.
It has gradually become obvious that the boat best suited to my needs is a small catamaran. I expect to be single handing more often than not, plan to live more or less permanently aboard while voyaging, exploring the world. I originally looked at trimarans, but to get the payload I'm looking for I would need almost 40', and it is my desire to stay down to around 30' for a number of reasons. Initial cost is less, less rig is required to drive a smaller boat, upkeep is lower. Above that length, costs tend to go up for everything fairly rapidly. Catamarans have close to double the payload of trimarans, provide better access to the stern, a roomier cockpit, and the cats that interest me have an integrated bridge deck cabin, on a level with the cockpit, and with a decent all around view for watch keeping in nasty weather. And of course they have a shallow draft which is one of my primary criteria.
As a single hander, fatigue is a big consideration, and being able to live primarily on the bridge deck where I can keep tabs on things is important. I expect to sleep on the bridge deck, either in the cabin or in the cockpit depending on weather, which is no real problem as I sleep in a recliner anyway, and a light weight "zero gravity" type recliner could serve that purpose, and be mounted either indoors or outdoors. When I say "mounted", I mean literally attached. The galley will be in one hull, as will the head and shower area. There will be a "direct deposit" head, consisting of nothing more than an opening through the bridge deck for use at sea, for safety. Most MOB situations are from pissing over the side ;-(
The rig will be a cambered split junk rig on a single central free standing mast, something I have yet to see on ANY cat. It will take some engineering to support a free standing mast on the bridge deck, but it presents no insurmountable difficulties.
The free standing mast eliminates ALL standing rigging, which eliminates dozens of components, the failure of any of which can send the mast over the side. Instead the engineering goes into the mast. Ultimately the initial cost will probably be comparable to a normal mast and all the rigging, and the total weight of mast and the junk rig will be somewhat more, but not much. Rigging is not light or cheap.
The junk rig offers huge advantages for a single hander. Blondie Hassler proved that when he came in second in the tiny folkboat, Jester in the first OSTAR back in 1960, sailing the Atlantic in bedroom slippers. He basically didn't leave the safety of the round hatch on the top of the coach roof of Jester.
The junk rig has come a long way since 1960, with the advent of the camber panel junk rig, and finally the camber panel split junk rig, where the fore sail and main sail are separated by a slot at the mast, both sails being on the same boom, yard, and battens. These split rigs acquit themselves well against Bermuda rigs .......... same size rig same boat, but require extremely little work to sail. They have only one sail. The advantages are numerous, the most important ones being instant reefing by simply letting go some halyard, and simplicity of tacking. Just put the tiller over and adjust the sheet after the boom swings across. There are no reefs to tie in, the sail drops into the lazy jacks like a Venetian blind, held by the battens. There are no winches needed, as there is no need to put tension on the sail to achieve shape, no vang, no traveler, no need for a preventer. The sheeting looks complex, but in reality, the modern sheeting schemes are extremely simple, a single line is all you deal with. Sheetlets are attached to the end of all but maybe the top battens, and a simple system is used to gather them and equalize them to a single sheet. The forces on the sheets are far less, due to the balance area forward of the mast. The loads on the sail cloth are a fraction of what they are on a Bermuda rig, and the battens isolate each panel, so a tear in a panel cannot propagate through the whole sail. If necessary, one can tie two battens together. Due to the low stresses, almost anything can be used for sail cloth in a pinch. There is no climbing onto the foredeck to wrestle a foresail up or down, and no antics to tack, trying to get the foresail between inner and outer forestays, no running backstays. No wet sail bags stowed below.
For a single hander who is not a glutton for punishment, it's the way to go IMHO.
The problem that keeps cropping up for me is payload...... I have a pretty good idea how quickly weight adds up, and this will be my home. I expect to do long passages that could take from a few weeks to a month, and need to be able to carry what I need. It's also important to me to be able to fix my boat and the systems in it. I've always done my own maintenance on everything..... the habit of a lifetime.
The two boats that come closest to meeting my criteria are Richard Wood's beautiful Sagitta catamaran, and Bernd Kohler's equally beautiful KD 860. Sagitta offers view, the KD 860 needs modification to meet this requirement. The KD 860 is only 28', and can use an additional couple of feet. A number of builders have done this, but in spite of it's shorter length, it offers a greater payload due to hull design. Sagitta is more desirable in many respects, but has a fairly considerably lighter payload, and is structurally less well suited to stepping a free standing mast. The KD 860 is well suited to the free standing mast, but the suitable location is too far aft, however the addition of 2 feet with the bridge deck beginning at the same distance aft of the bow, and an enlargement of the saloon puts things in the ballpark.
The construction of the KD 860 is far simpler, with no chines, and a flat bottom, and sides with an unbroken contour to about head level. This shape results in the higher displacement per inch of draft. It is by far the faster simpler boat to construct, and the structural engineering is very well thought out and ingenious.
My boat of choice would be Sagitta with the Kohler hulls..........
Of course I haven't touched on balance. Needless to say the junk rig shifts the center of effort well aft of normal unless the mast(s) are well forward. This is obviously not possible with a single mast on the bridge deck of a cat. The solution most people resort to is the biplane rig, where a mast is stepped into each hull, and it's a logical solution. I don't want a biplane rig. More masts, more sails, more rigging and hardware, more weight, and more complexity. It does however make a lot of sense, allowing the masts to be low and the rigs small.
The shift of the center of effort aft, means that the center of lateral resistance must also move aft to avoid big issues with helm balance. This among other things is one of the big reasons for building my own boat rather than doing a conversion. In Sagitta for example, the daggerboards would no longer be in the galley and chart room.
I'm not pioneering in this, there are many junk rigs out there now, and the methods of determining these locations are well established. In addition, well balanced airfoil shaped rudders will tame this a lot.... Needless to say I have a lot of ideas.
Weather I end up building from Richard Woods plans or Bernd Kohler's plans, it is likely that I will end up with about the same boat. I've been designing and building and modifying and inventing all my life, but it is always nice not to have to re-invent the wheel... Both of these superb designers have already invented that.
I was very resistant to going with foam sandwich initially........ I know steel, aluminum, and wood very well, foam and glass not so well, though I do have some small experience there. The potential reduce the empty weight by as much as 25%... which is probably a bit optimistic, adds up to another half a ton payload. To achieve that additional half a ton of payload in plywood, I would have to build a much larger and heavier boat, and need a larger rig to drive it. The initial construction cost in foam sandwich will undoubtedly be higher than for the exact boat in plywood, though using XPS judicially will alleviate this significantly it looks like. I have yet to locate and price the suitable XPS foams. However even with the cost of Divinicell, and extra glass and epoxy, it would be foolish not to take into account the value of weight reduction, and it is considerable if you start comparing to larger boats. That cost is not just initial cost, but ongoing higher costs.
From being extremely skeptical, I've become extremely interested, not just in weight reduction but in the labor reduction of Rob's intelligent infusion methodology.
I was reluctant to completely come out of the closet so to speak initially. My ideas may seem a bit crazy to some....... and that's OK. I have for example no desire to sell the junk rig to anybody, or to win converts to my way of thinking. All I want out of this is a catamaran capable of meeting my criteria well. A boat that will not beat me up or wear me down that I can sail the world's oceans in and visit far away places while I'm still young and healthy enough to enjoy them. To meet fellow sailors in those places, and to meet the locals, making friends along the way. A boat where I can stand on the floor, not the wall, and a boat where I don't need a lee cloth to sleep while under way or at anchor, where the stew stays in the pot, and where I can look out the window and really see where I am, and step out into the cockpit without climbing a ladder. A boat with a shallow draft that will take me into quiet places others cannot go A boat that I can sail single handed without wearing myself out. A traveling home, all be it a small one.
I've been an admirer of Rob's Harry Proa designs for a short time.......... since I first looked at photos of them, and realized how ingenious many of his approaches. The first comparisons to come to mind were Bucky Fuller and Phil Bolger, Jim Brown, and John Marples, Woody Brown, and a number of other innovators. I hope to incorporate some of Rob's ideas into my own project. A proa will not fulfill my criteria for the same reason a trimaran won't, but I hope a few years down the road to sail into Oz have a chance to meet designers and builders down there. Some like the late Ian farrier are no longer with us, but there seems to be an endless supply down under.
H.W.
On 05/24/2018 10:46 AM, '.' eruttan@yahoo.com [harryproa] wrote:
It has gradually become obvious that the boat best suited to my needs is a small catamaran. I expect to be single handing more often than not, plan to live more or less permanently aboard while voyaging, exploring the world. I originally looked at trimarans, but to get the payload I'm looking for I would need almost 40', and it is my desire to stay down to around 30' for a number of reasons. Initial cost is less, less rig is required to drive a smaller boat, upkeep is lower. Above that length, costs tend to go up for everything fairly rapidly. Catamarans have close to double the payload of trimarans, provide better access to the stern, a roomier cockpit, and the cats that interest me have an integrated bridge deck cabin, on a level with the cockpit, and with a decent all around view for watch keeping in nasty weather. And of course they have a shallow draft which is one of my primary criteria.
As a single hander, fatigue is a big consideration, and being able to live primarily on the bridge deck where I can keep tabs on things is important. I expect to sleep on the bridge deck, either in the cabin or in the cockpit depending on weather, which is no real problem as I sleep in a recliner anyway, and a light weight "zero gravity" type recliner could serve that purpose, and be mounted either indoors or outdoors. When I say "mounted", I mean literally attached. The galley will be in one hull, as will the head and shower area. There will be a "direct deposit" head, consisting of nothing more than an opening through the bridge deck for use at sea, for safety. Most MOB situations are from pissing over the side ;-(
The rig will be a cambered split junk rig on a single central free standing mast, something I have yet to see on ANY cat. It will take some engineering to support a free standing mast on the bridge deck, but it presents no insurmountable difficulties.
The free standing mast eliminates ALL standing rigging, which eliminates dozens of components, the failure of any of which can send the mast over the side. Instead the engineering goes into the mast. Ultimately the initial cost will probably be comparable to a normal mast and all the rigging, and the total weight of mast and the junk rig will be somewhat more, but not much. Rigging is not light or cheap.
The junk rig offers huge advantages for a single hander. Blondie Hassler proved that when he came in second in the tiny folkboat, Jester in the first OSTAR back in 1960, sailing the Atlantic in bedroom slippers. He basically didn't leave the safety of the round hatch on the top of the coach roof of Jester.
The junk rig has come a long way since 1960, with the advent of the camber panel junk rig, and finally the camber panel split junk rig, where the fore sail and main sail are separated by a slot at the mast, both sails being on the same boom, yard, and battens. These split rigs acquit themselves well against Bermuda rigs .......... same size rig same boat, but require extremely little work to sail. They have only one sail. The advantages are numerous, the most important ones being instant reefing by simply letting go some halyard, and simplicity of tacking. Just put the tiller over and adjust the sheet after the boom swings across. There are no reefs to tie in, the sail drops into the lazy jacks like a Venetian blind, held by the battens. There are no winches needed, as there is no need to put tension on the sail to achieve shape, no vang, no traveler, no need for a preventer. The sheeting looks complex, but in reality, the modern sheeting schemes are extremely simple, a single line is all you deal with. Sheetlets are attached to the end of all but maybe the top battens, and a simple system is used to gather them and equalize them to a single sheet. The forces on the sheets are far less, due to the balance area forward of the mast. The loads on the sail cloth are a fraction of what they are on a Bermuda rig, and the battens isolate each panel, so a tear in a panel cannot propagate through the whole sail. If necessary, one can tie two battens together. Due to the low stresses, almost anything can be used for sail cloth in a pinch. There is no climbing onto the foredeck to wrestle a foresail up or down, and no antics to tack, trying to get the foresail between inner and outer forestays, no running backstays. No wet sail bags stowed below.
For a single hander who is not a glutton for punishment, it's the way to go IMHO.
The problem that keeps cropping up for me is payload...... I have a pretty good idea how quickly weight adds up, and this will be my home. I expect to do long passages that could take from a few weeks to a month, and need to be able to carry what I need. It's also important to me to be able to fix my boat and the systems in it. I've always done my own maintenance on everything..... the habit of a lifetime.
The two boats that come closest to meeting my criteria are Richard Wood's beautiful Sagitta catamaran, and Bernd Kohler's equally beautiful KD 860. Sagitta offers view, the KD 860 needs modification to meet this requirement. The KD 860 is only 28', and can use an additional couple of feet. A number of builders have done this, but in spite of it's shorter length, it offers a greater payload due to hull design. Sagitta is more desirable in many respects, but has a fairly considerably lighter payload, and is structurally less well suited to stepping a free standing mast. The KD 860 is well suited to the free standing mast, but the suitable location is too far aft, however the addition of 2 feet with the bridge deck beginning at the same distance aft of the bow, and an enlargement of the saloon puts things in the ballpark.
The construction of the KD 860 is far simpler, with no chines, and a flat bottom, and sides with an unbroken contour to about head level. This shape results in the higher displacement per inch of draft. It is by far the faster simpler boat to construct, and the structural engineering is very well thought out and ingenious.
My boat of choice would be Sagitta with the Kohler hulls..........
Of course I haven't touched on balance. Needless to say the junk rig shifts the center of effort well aft of normal unless the mast(s) are well forward. This is obviously not possible with a single mast on the bridge deck of a cat. The solution most people resort to is the biplane rig, where a mast is stepped into each hull, and it's a logical solution. I don't want a biplane rig. More masts, more sails, more rigging and hardware, more weight, and more complexity. It does however make a lot of sense, allowing the masts to be low and the rigs small.
The shift of the center of effort aft, means that the center of lateral resistance must also move aft to avoid big issues with helm balance. This among other things is one of the big reasons for building my own boat rather than doing a conversion. In Sagitta for example, the daggerboards would no longer be in the galley and chart room.
I'm not pioneering in this, there are many junk rigs out there now, and the methods of determining these locations are well established. In addition, well balanced airfoil shaped rudders will tame this a lot.... Needless to say I have a lot of ideas.
Weather I end up building from Richard Woods plans or Bernd Kohler's plans, it is likely that I will end up with about the same boat. I've been designing and building and modifying and inventing all my life, but it is always nice not to have to re-invent the wheel... Both of these superb designers have already invented that.
I was very resistant to going with foam sandwich initially........ I know steel, aluminum, and wood very well, foam and glass not so well, though I do have some small experience there. The potential reduce the empty weight by as much as 25%... which is probably a bit optimistic, adds up to another half a ton payload. To achieve that additional half a ton of payload in plywood, I would have to build a much larger and heavier boat, and need a larger rig to drive it. The initial construction cost in foam sandwich will undoubtedly be higher than for the exact boat in plywood, though using XPS judicially will alleviate this significantly it looks like. I have yet to locate and price the suitable XPS foams. However even with the cost of Divinicell, and extra glass and epoxy, it would be foolish not to take into account the value of weight reduction, and it is considerable if you start comparing to larger boats. That cost is not just initial cost, but ongoing higher costs.
From being extremely skeptical, I've become extremely interested, not just in weight reduction but in the labor reduction of Rob's intelligent infusion methodology.
I was reluctant to completely come out of the closet so to speak initially. My ideas may seem a bit crazy to some....... and that's OK. I have for example no desire to sell the junk rig to anybody, or to win converts to my way of thinking. All I want out of this is a catamaran capable of meeting my criteria well. A boat that will not beat me up or wear me down that I can sail the world's oceans in and visit far away places while I'm still young and healthy enough to enjoy them. To meet fellow sailors in those places, and to meet the locals, making friends along the way. A boat where I can stand on the floor, not the wall, and a boat where I don't need a lee cloth to sleep while under way or at anchor, where the stew stays in the pot, and where I can look out the window and really see where I am, and step out into the cockpit without climbing a ladder. A boat with a shallow draft that will take me into quiet places others cannot go A boat that I can sail single handed without wearing myself out. A traveling home, all be it a small one.
I've been an admirer of Rob's Harry Proa designs for a short time.......... since I first looked at photos of them, and realized how ingenious many of his approaches. The first comparisons to come to mind were Bucky Fuller and Phil Bolger, Jim Brown, and John Marples, Woody Brown, and a number of other innovators. I hope to incorporate some of Rob's ideas into my own project. A proa will not fulfill my criteria for the same reason a trimaran won't, but I hope a few years down the road to sail into Oz have a chance to meet designers and builders down there. Some like the late Ian farrier are no longer with us, but there seems to be an endless supply down under.
H.W.
On 05/24/2018 10:46 AM, '.' eruttan@yahoo.com [harryproa] wrote:
| The next question is how to use high density XPS, Finnfoam or Dow, etc in "intelligent infusion".
As stated in prior messages and confirmed by Rob, one could manually carve the surface to make epoxy channels, and holes through to the lower fabric, and save distribution fabric. Or use distribution fabric.
If one has any sort of urban area nearby, look out for a 'maker space', to see if they may have a 'shopbot'. Ours does, and it is my plan to use it to cnc carve the surface and put through holes in it.
I was thinking to start with a pattern like '3d core' uses. Machined hexagons. Through holes at corners.
P.S.
Howard, you should post about your catamaran here.
__._,_.___
Posted by: StoneTool <owly@ttc-cmc.net>
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