Catamaran Thoughts

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  • 24 Sep 2019 00:30
    Reply # 7895293 on 7895199
    Anonymous wrote:

    Howard, being aware of the  drag problem caused by tail squat, trim is of course important, and the idea to modify the sterns of lets say a Wharram Pahi 31 would involve adding a step, outwards, at waterline level, to spread the topside planking and gain volume along with buoyancy and dynamic lift. Execution and Detail of such a change needs much care, that might not have been relayed in the few words penned so far on the subject.

    By the way and talking of horses -- i have just managed to read the book 'on the trail of Genghis Khan' by Tim Cope...... a wonderful adventure, revealing so much about man, migration and connection to horses.

    Sure, being tethered to a runaway horse or a multihull might be an equally bad thing and another reason why it could be beneficial to make changes to the stern end of a Wharram, and having a beam across the stern at safety rail height, with access down to a platform near water level would suit me better than a deck raised to max height.

    It's also the depth and efficeincy of high aspect rudders that can be lifted, that should work along with one other board, to make enough lateral area to augment the V'd bottoms in leeway resistance. 


    Jeremy:

          I suspect we are pretty much on the same page in many respects.   I would not change the hull side contours, just the bottom to bring the transom to WL, but I feel that adding foam and glass above WL on the hull to increase the displacement rapidly in a pitching situation could have real benefit...... what I envision is a streamlined structure faired to the  inboard side of the hulls, faired into the hull contour..... this could also widen the transom inward. It would all be above WL, and it could enhance the utility of the transom for boarding from the water.  I've seen a few cats that are designed to board from inboard as well as aft.  Of course if you go over the side, this is on the wrong side of the hull.  

         Structurally I saw the value in your suggested configuration immediately..but I design and build things all the time. 

         At the risk of sounding crude... a  large percentage of MOB situations result from "pissing over the side".......... I would strongly advocate a "one holer" (western term for an outhouse with one opening) right in the cockpit to discourage this..... Flip a cockpit seat up, and you have an opening for "direct deposit".   


         As for horses........ I developed a fondness for  horses....... but not a blind one, at a young age.  I can handle them well and have no real fear of them, but a healthy respect for the damage they can do.. often unintentional.  There have been  horses in my life I would trust with my life... they were smart, we were on the same page, and we were friends.   We took care of each other. Those are the minority, and trust will kill you.   I spent 2 years of  my life riding every day all day long, on the prairie and and in the mountains with nobody around.. seeing another person once a week to ten days.... a wonderful experience..........At night, I could see no lights, in the day no power lines, roads, etc. It was like being the first white man in this part of the west, and I half expected to see Crow or Blackfoot warriors come riding over the hill one day.    I will treasure that time all my life.   I rode horses that ranged from trusted friends, to "hammerheads", where you had to be on guard every second.......but I was always "master", and that is the key with any animal.  

          Ranging wildly off topic at times, this has developed into an interesting thread... to me at least.   I've tried to take this "private" but your Email is outdated.... but I suspect that others probably find it an interesting diversion also.

         I'll try to keep away from  microbiology, wild animal experiences, brewing and distilling,  cooking and food preservation, diesel engine rebuilding, agriculture, electronics, and other off topic stuff   ;-)


                                                                     H.W.

  • 23 Sep 2019 22:26
    Reply # 7895199 on 7869048

    Howard, being aware of the  drag problem caused by tail squat, trim is of course important, and the idea to modify the sterns of lets say a Wharram Pahi 31 would involve adding a step, outwards, at waterline level, to spread the topside planking and gain volume along with buoyancy and dynamic lift. Execution and Detail of such a change needs much care, that might not have been relayed in the few words penned so far on the subject.

    By the way and talking of horses -- i have just managed to read the book 'on the trail of Genghis Khan' by Tim Cope...... a wonderful adventure, revealing so much about man, migration and connection to horses.

    Sure, being tethered to a runaway horse or a multihull might be an equally bad thing and another reason why it could be beneficial to make changes to the stern end of a Wharram, and having a beam across the stern at safety rail height, with access down to a platform near water level would suit me better than a deck raised to max height.

    It's also the depth and efficeincy of high aspect rudders that can be lifted, that should work along with one other board, to make enough lateral area to augment the V'd bottoms in leeway resistance. 

  • 23 Sep 2019 11:06
    Reply # 7894043 on 7869048

    Howard, you seem to be getting the idea about using the forward inboard-jutting corner of the cabin structure as a good place to locate a Junk mainmast, but using my Pahi proa as an example for scaling, may be a mistake.... this craft is sized to be moved about by myself and loaded onto a little trailer( fitted with a lngthened draw bar), being helped by a friend or two, then towed for relocation by a small/4cyl sedan car. Comparison with a Wharram Pahi 31 would even make the 26 foot hull ( of my Pahi shown in pics here on this thread) look small.

    Weight wise, my Pahi is no doubt the lesser, which comes with the proa configuration and allows me to get away with a lower cost rig than the Junk type that we  are contemplating.

    Forgetting about shunters then -- increased size , including beam, offers more space and of course, hulls are equal sized, meaning payload needs to be distributed evenly between them.Stowage of chain, water, fuel and provisons could be accommodated in compartments built into a girder spanning the main connecting beam/bulkhead and the next beam aft of the cabin, rather than having only a bulkhead as this load bearer . Assuming we are not bound to taking care of rig loadings associated with a BR. Carrying of payload midship and mid-beam, is an advantage worth exploiting,As long as this weight is kept as low as deck level, if not underslung, then the resultant CG should not be problematic. Wharrams that I am familiar with have been trimmed by the stern, which is good and fine since they are double enders, but as a result are prone to hobby-horsing.

    Modifying/chopping the sterns (as I have suggested), is aimed at adding volume and buoyancy, to damped pitching as well as provide footing closer to water level.

    This sort of mod is obviously something radical in respect to the Wharram philosopphy, but since we are tacking (rather than shunting) and most catamarans manage just fine with transoms, a compromise should not necessarily be a bad thing...... then, as you imply, in a a MOB situation there could be something to be gained.

    Ideas being put forward here are based on changes that would be required to covert my Pahi to carry a battened lug rig with Junk sheeting system.... in the event I had the money  to do so and the need to reduce physical demands on sail handling.

    Last modified: 23 Sep 2019 11:18 | Anonymous member
  • 23 Sep 2019 02:37
    Reply # 7893696 on 7892748
    Standing or sitting at times for the last few days sanding and brush coating the galley area inside my SO Pahi, at the same time giving consideration to the the above thoughts has me convinced that converting a Wharram to gain similar living space makes for an entirely suitable habitat for long term cruising.This in the view that I cope just fine with only one area of a little over 1/2 square Metre that allows standing headroom, with cooking and watch-keeping able to be taken care of at the same time.Being able to immediately pop-up through the companionway; putting on or taking off wet gear right there is also important, besides having a dry berth off to the side of a through-way.

    This is all possible, as well as having a rigid structure for the mast step and stowage area (with access from inside the cabin) to carry stores right in the middle of the cat.

    Some flexibility between the hulls is allowable, but this depends on choice as how , exactly, to construct and attach the beams and connecting structure, which in turn depends on the rig...... I know how i could rig a split rig with a tabernacle for the mainmast, but which would have limited ability to square-off the main'sl when sailing off the wind.This amounts to a contestable configuration in terms of modern Junk rig, so i will not attempt to explain things along this line any more on this thread ( instead hope to explain with a diagram/drawing or two in a separate thread).

    Going without rigging and a taller una rig could be possible, this being stepped within a fabrication that connects the second hull, using bolt fastenings and has negligable flexibilty.

    At the same time as fabricating the connecting structure, a single swing-drop or kick-up board could be included in the mods; to avoid ever dropping daggerboards through the hulls.

    Since there will be cutting and modifying of  the standard Wharram hulls,I would be partial to removing the sternposts and building steps down to  mini transoms that have cassette held rudder blades, which can be lifted.

    These last few suggestions are based on the essentially un-Wharram (conventional plymaran  designer) idea, that flexibility is is crude and passe.

    Ironically, junk sails with bamboo and string, rigged in an apparently similar way to the plant fibre secured components and rigs of Oceanic canoes, have much in common....it comes down to personal choice and factors of technological limitations really.


    Jeremy:

         Possibilities are endless......... Your half cabin is interesting, but the cabin would be quite small. I like the structural aspect of having the forward bulkhead.... presumably on top of a beam, serving as a structural support for the mast tabernacle, and the longitudinal bulkhead on the port side of the cabin, also serving as structural support, carrying load to the beam at the aft end of the cabin, the roof locks things in as well, as does the deck (lets assume the hull married to it is the starboard hull just for convenience).    A corner is the strongest most rigid part of a structure.   The space in the cabin could be increased simply by angling the longitudinal bulkhead on it's port side, which would widen the aft end of the cabin as compared to the forward end.  The mast could of course be offset well beyond center, leaving just a walkway between the cabin wall and the port hull.  

            I think you'd better look a bit more at your transom idea..........  Simply sawing the hull off, eliminating the stern post, and installing a transom would result in "dragging" the transom, something designers go to great lengths to avoid.   If you chose to do that, the hull sides also should be cut on an upward slope from close to the first bulkhead forward of the sternpost, and a triangle piece of ply put between them... or two, filling that space with a flat or a slight V.      Steps are popular, but the Wharram ramp is really a lot nicer in many ways.... Of course in an MOB situation the ramp might not be down, but the steps are always down.  Of course a solo MOB with a safety harness, might not be survivable due to the faster speed than a mono...... Pulling yourself up against the flow is incredibly difficult......I've done it playing in rivers.    I also had to do it when dragging behind a horse by one leg, lug sole boots caught in the stirrup (he fell on a slick spot and I couldn't get clear as he got up)......I'm only alive today due to superhuman strength due to adrenalin, deep snow, and insulated coveralls, which I had to climb, twisting my hands in the fabric and pulling myself up as I bounced off rocks and sagebrush, until I was hanging from the stirrup strap by one hand, flipping it off my boot with the other..........The nearest human was about 5 miles away and wouldn't come looking for me for about a week, so it was up to me!!    A safety line that trails behind, and releases the halyard, and trips the wind vane could be a life saver..... if you can get to it.


        

                                                                H.W.
  • 22 Sep 2019 00:02
    Reply # 7892748 on 7885435
    Anonymous wrote:
    Anonymous wrote:

    Many thoughts on this subject, too many to try listing in one post, so will try to mainly cover the question of hull size  for a habitation unit and then include a thought or two about Junk rig and  adaptability to a Wharram type cat.

    Right now am working in the habitation unit of my Pahi, which compares in size to a Tiki 26, except in that cabin width has been expanded (width is 2.1 metres compared to 1.2 or so of a Wharram hull at deck level).There is a settee bench and double berth on the inboard side, a small galley, stowage lockers and a writing station(with flap down surface),  on the outboard side of the hull. Forward and aft of this basic living area are single tunnel berths, as per the usual Wharram way/style, with storage under.

    Living space for for 2 is acceptable in this hull, but two more could squeeze in for a drink or a feed (provided they are not obese and don't mind getting cozy with the other two.

    Being a proa ama in this /my case, this ama hull is about a metre shorter than the other or lee hull, which means that I lose roughly 1/2 metre of tunnel space beyond each single berth, by living in the shorter hull, and this is the  best use (for habitation) I think I can make of an 8M hull.

    Assuming I had built  the habitation unit on the 9M hull,  which is what the lee hull measures on my Pahi, then there would have been a fair amount of extra elbow room and locker space, plus more stowage space under seats and berths.

    Having two hulls, means that a wash compartment and heads is separate from the main habitation space, providing much aditional stowage space as welll in the second hull.

    Considering then,  conversion of a 30 ft Wharram, with 17ft beam -- an expanded living unit/cabin would measure over 8ft from the mast bearing girder midway between the hulls, to the outboard side beyond the galley..... thus providing considerably more habitation space than that in an 8M hull.

    Stealing/annexing half of what usually comprises excessive open deck space (on a standard Wharram), for cabin space to one side(of midway betweenhulls), overcomes the 'culvert/tunnel hull limitations and helps create facility to step a junk main mast.

    Talking of Junk rig and Wharram  -- James told me that he( along with Ruth) had started out with an attempt to Junk rig  a Lifeboat, then  went on to concentrated on double canoes. He did in fact dabble with a battened lug on Tehini, but early on it was found (apparently) that a smaller and more efficient rig suited the speed potential of a multihull better than greater sail area provided by junk rig.

    Here I wonder whether  going the route of using a single/una Junk sail of higher aspect ratio, will likewise be better than a shorter biplane set up.  


    There is more than a little merit in the idea of joining a half bridge deck cabin with one hull, at 50% beam.... or even more...... presumably a non standing space.  It would expand internal space, provide that dry all weather location to sit with all around view, allow good protected access forward, view over the top when helming, and access from the side and aft both, as well as a hard point where two intersecting walls could support the mast partner.  It would also provide good access to the foredeck.   An aft facing doorway / hatch would be infinitely preferable to a side access in many conditions...and you would have that.  

         It's an interesting thought, and compatible with the flexible hull beam joint.


                                                                 H.W.

    Standing or sitting at times for the last few days sanding and brush coating the galley area inside my SO Pahi, at the same time giving consideration to the the above thoughts has me convinced that converting a Wharram to gain similar living space makes for an entirely suitable habitat for long term cruising.This in the view that I cope just fine with only one area of a little over 1/2 square Metre that allows standing headroom, with cooking and watch-keeping able to be taken care of at the same time.Being able to immediately pop-up through the companionway; putting on or taking off wet gear right there is also important, besides having a dry berth off to the side of a through-way.

    This is all possible, as well as having a rigid structure for the mast step and stowage area (with access from inside the cabin) to carry stores right in the middle of the cat.

    Some flexibility between the hulls is allowable, but this depends on choice as how , exactly, to construct and attach the beams and connecting structure, which in turn depends on the rig...... I know how i could rig a split rig with a tabernacle for the mainmast, but which would have limited ability to square-off the main'sl when sailing off the wind.This amounts to a contestable configuration in terms of modern Junk rig, so i will not attempt to explain things along this line any more on this thread ( instead hope to explain with a diagram/drawing or two in a separate thread).

    Going without rigging and a taller una rig could be possible, this being stepped within a fabrication that connects the second hull, using bolt fastenings and has negligable flexibilty.

    At the same time as fabricating the connecting structure, a single swing-drop or kick-up board could be included in the mods; to avoid ever dropping daggerboards through the hulls.

    Since there will be cutting and modifying of  the standard Wharram hulls,I would be partial to removing the sternposts and building steps down to  mini transoms that have cassette held rudder blades, which can be lifted.

    These last few suggestions are based on the essentially un-Wharram (conventional plymaran  designer) idea, that flexibility is is crude and passe.

    Ironically, junk sails with bamboo and string, rigged in an apparently similar way to the plant fibre secured components and rigs of Oceanic canoes, have much in common....it comes down to personal choice and factors of technological limitations really.

    Last modified: 22 Sep 2019 00:06 | Anonymous member
  • 19 Sep 2019 04:40
    Reply # 7888520 on 7887134
    Howard wrote:

    Arne:

          Thanks for the link.......   I guess it's time I went through the details about sewing sails a bit more carefully......... sewing seems to be a mental block for me for some reason......It is outside my normal field of endeavor.  That usually doesn't stop me from taking on a project.   I have an excellent potential coach locally...... sewing is her passion, largely quilting, which is very popular here.


                                                                                   H.W.

    I had never imagined myself as a sewer, but having gone through a very rapid apprenticeship with David Tyler when making sails for our two boats I found I quite enjoyed sewing. I bought myself a semi industrial walking foot sewing machine a few years ago and have since made two sail covers and numerous other canvas projects for my boat, and so have certainly gotten back the investment in the sewing machine. If I want to know how to make a cover of some sort I look online for instructions, and also go and look at finished products on other boats.
  • 18 Sep 2019 14:34
    Reply # 7887134 on 7869048

    Arne:

          Thanks for the link.......   I guess it's time I went through the details about sewing sails a bit more carefully......... sewing seems to be a mental block for me for some reason......It is outside my normal field of endeavor.  That usually doesn't stop me from taking on a project.   I have an excellent potential coach locally...... sewing is her passion, largely quilting, which is very popular here.


                                                                                   H.W.

  • 18 Sep 2019 09:51
    Reply # 7886855 on 7869048
    Anonymous member (Administrator)

    Howard,

    You are not the first one to feel that sewing a sail would be a daunting undertaking. Over the years (in particular on the Yahoo JR Group), there were many clever suggestions on how to avoid sewing the panels together along the battens. Most solutions were in the nuts-and-bolts category. No matter how many times I repeated that the sail doesn’t have to be rolled up and pushed through the sewing machine, it didn’t sink in. Avoiding sewing seems to be a big issue to those who have little or no experience with a sewing machine.

    Roger Taylor has a sound enough argument for his method. On his long voyages, he must deal with any problems without any help. In case a panel rips (that doesn’t happen) or a batten breaks, it will be quite doable to lash together two ‘fresh’ battens and thus reef away a broken batten or a ripped panel.

    For my coastal sailing, there is less need for this. So far, the only acute structural problem I have had was in Johanna’s yard, when a weld broke. The rig was still usable and we returned to base under sail.

    In case Ingeborg’s sail decides to rip in a panel, I will most probably complete the trip without doing anything to it. The oversize boltrope will ensure the integrity of the sail.  However, if the trip is to last for several days, I guess I would tie the ends of the battens above and below the rip together. If the weather eased and allowed me to, I might ‘sew’ the battens together on 3-4 places to secure the slack panel (.. using needle and twine...).

    There are three bits in the rig (apart from the mast), which must be over-engineered and maintained, so that they never break: Halyard, topping lifts and mast lift. Ingeborg carries a spare halyard...

    Arne


    Last modified: 18 Sep 2019 09:51 | Anonymous member (Administrator)
  • 18 Sep 2019 02:39
    Reply # 7885982 on 7885465

    Why?

    How can you state that Roger Taylor’s sails, where the batten panels are joined with ‘hinges’, are easier to make at home than for instance my sails, assembled the way I do it (..barrel  cut panels, assembled using ‘Amateur Method B’...)?

    What needs floor space, is lofting each panel, so there is no difference between Roger’s and my need for it. A browse through this album showing the construction of Ingeborg’s sail, will confirm this.

    The sewing machine I use is a domestic one with a normal arm, and I have made six junk-sails (and a few others) with it, so far.

    Arne



    Having never attempted a sewing project of that magnitude, It appears to me that handling a lot less cloth would be easier...  Less to wrestle through the machine as less space required.    That said there are obviously more pieces to make and hem, more total work.   I haven't done any machine sewing in quite a few years, but as I recollect handling large items is a bit of  headache........     Sewing is not my forte.   I have to confess that I have not read through your descriptions of the process you use in detail, so I spoke in ignorance.....

                                                                  H.W.

  • 17 Sep 2019 21:33
    Reply # 7885465 on 7885416
    Anonymous member (Administrator)

    Howard  wrote:  
    .......   Even more so would be Roger Taylors "hinged panel" sail, so his builders could make a cambered sail at  home on an ordinary sewing machine easily.  

                                                                            H.W.

    Why?

    How can you state that Roger Taylor’s sails, where the batten panels are joined with ‘hinges’, are easier to make at home than for instance my sails, assembled the way I do it (..barrel  cut panels, assembled using ‘Amateur Method B’...)?

    What needs floor space, is lofting each panel, so there is no difference between Roger’s and my need for it. A browse through this album showing the construction of Ingeborg’s sail, will confirm this.

    The sewing machine I use is a domestic one with a normal arm, and I have made six junk-sails (and a few others) with it, so far.

    Arne


    Last modified: 17 Sep 2019 22:51 | Anonymous member (Administrator)
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