easy, fast to build multihull with simple rig

Discussion in 'Multihulls' started by sailor305, May 15, 2012.

  1. Silver Raven
    Joined: Oct 2011
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    Silver Raven Senior Member

    Absolutely no sarcasism intended

    Goodevening David. See my heading please. A bit of dry humour but not intended to be in any way to be sarcastic. I personally regret that you took it that way.

    The "somewhat sarcastic question" was in fact not intended either. I may have very easily made some or many weight calculations in error & I'm far to old to be fragile about making mistakes & always hope someone will find my errors & bring them to my attention.

    In my 'weights estimates' - I do go for bigger o/b motor or motors due to the much larger charging factor & also the much greater hp - all of that extra safety factor only adds 12 kgs & in fact the bigger motor doesn't use any more fuel than the little one. So there were/are many fudge-factors - in my 'weights' - all open to review by everyone.

    My comments were said very much - tongue-in-cheek - & I like you have done quite some long weekends camping on a smaller cat - but in my case it was a 'shearwater' catamaran & take my word for it - that was a long time ago. Sydney to 'the 'gong' - Sydney to N'castle & on up to Taree, etc etc.

    Also my 'questimations' of the very complex area of - anchors, chains, rodes - are subject to much disagreement however having been on-board through over a dozen cyclones - I tend to error on the safe side. I'm still alive but.

    Thanks for your reply - regret you took my comments the way you did. Ciao, for now - from the tropical rainforest - where it is - & in 'wheelie-bins'. james
     
  2. gypsy28
    Joined: Mar 2010
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    gypsy28 Senior Member

    Thats cool, no probs James, internet communication can be lost in translation sometimes;) oh and its pissing down here too:( supposed to fine up a bit next week tho:D

    DAVE
     
  3. rob denney
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    rob denney Senior Member

    Shunting is dead easy, and unlike tacking/gubing remains so regardless of wind strength and wave size.

    Extra load goes in the lee hull, which does not load up the beams or rig. You can therefore safely add a lot more than you can to a cat or tri. Max for Visionarry would presumably be several tons, with associated low speed.

    Seaworthiness is a huge subject. Tired, stressed crew are the usual weak point. Keeping them off the foredeck (no sails out there), sheltered (but still able to sail the boat), fed (galley close to the hatch, amidships) with easy sail changes (one jib, flexible mast, completely stop the boat to reef) does a lot to prevent this. Worst case, pull up the rudders (no daggerboards or fixed keels needed), drop the sails and you have an 8m x 15m raft drawing less than 300mm with minimal windage which would be very difficult to flip.

    A harryproa has more righting moment than an equivalent weight catamaran as the (always to) windward hull is heavier then the lee one. The harry will be lighter than an equivalent length/space cat so has a smaller rig. Unstayed masts flex automatically in gusts. This removes sail area from the top of the rig, raising the capsize wind strength significantly.

    Hull speed is not really an issue with hulls more than 10 times as long as they are wide.

    Vis has 1.9m/6'4" max headroom, adding more is very simple. One of the advantages of an "accommodation only" hull is that it can be laid out with a lot more options than a hull that also has to cope with mast, rudders, boards etc and their attendant loads.

    Correct. Latest boats have been schooners (no headsails at all) so the space between the beams on the lee hull can be utilised.

    it is not my rig, the ballestron has been around for decades. Amazes me that they are not standard for cruisers. To quote Richard: "The sails are always working correctly, whatever point of sail. ..the rig works to 95% efficiency all the time. A conventional rig may work to 100% if you're an expert, but only 70% if you're not. A conventional rig needs extra downwind sails, ie spinnakers. The Aerorig doesn't. There are only light loads on the mainsheet, and once unrolled there is never a need to adjust the jib sheet"

    The 15m in the video has a normal #40 winch on the mast for halyards and reefing, and a 44 for the 2:1 mainsheet. This is overkill, but it was also intended to be used as an anchor winch.

    rob
     
  4. rob denney
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    rob denney Senior Member

    To optimise carbon's properties, you need high pressure compaction and high temperature for the resin. But the stuff is so much stiffer for it's weight than wood, glass, steel and alloy that even used with slightly less than optimum processes (vac bagging, moderate post cure), it is far superior. Stiffness is the important parameter for masts, beams, rudder shafts etc. Any of these components that are stiff enough will be strong enough, which is a huge safety feature. And you don't need to use epoxy. Vinylester has excellent properties at 1/3rd the price, though I prefer epoxy for secondary bonding. Unfortunately, Ve stinks and doesn't have the ultra long cure times that epoxy does.

    Not sure, but suspect status quo, fear of something new and vested interests would all be part of it.

    The minor (and usually irrelevant) side issues are often amusing. "Don't use a safer, easier, cheaper rig because you can't use a tricolour " for example. There are plenty of others.

    There was an alloy wing mast extrusion (Zapspars) back in the 80's, but as with all extruded masts, it had uniform wall thickness. With a carbon mast you only put material where you need it, which saves a lot of weight.

    Not sure, but status quo, fear of something new and vested interests would all be part of it.

    1.7 tonnes seems about right for weight conscious couples who occasionally spend 2-3 weeks crossing an ocean (and can overload if required) and are near facilities the rest of the time.

    How big a harryproa do you need to get 3 tonnes payload and room (not just bunks) for 6 adults? Probably 18m/60' if you still want to sail at wind speed between 6 and 16 knots.

    Cats and dogs here (Gold Coast) too. Gotta love this country!

    Richard,
    I was not comparing anything to Flica, just looking for a strip planked cat with similar usage (performance cruiser) empty weight (2.5T), and construction (strip plank) to Visionarry. Scylla was the first design I found that fit the bill. Very much "oranges to oranges" in this discussion.

    My 25 odd years experience with shipping stuff to the Philippines and similar places is that "construction materials" (resin, reinforcement, core) that fit in a container are pretty easy, whereas importers of "luxury goods" (eg pleasure boat masts) are seen as easy pickings. Biggest problem with a second hand mast is you will still have all the stays to get in the way, worry about and replace every 5 years.

    I have not seen Kurt's comments on infusion, please post them.

    No idea how your friend built his CM boat, but the 3 hulls I built using it were a dream. Very quick (a day per half hull), lighter, cheaper and stiffer than same thickness ply and far easier to assemble as there were no strongback, frames, stringers, keelson or stem to set up and accurately plane to shape, no scarphing, no wet joins to be clamped/screwed together and we did not have to fill all those screw holes. And very nice, fair shapes as well. It is (was, the door skins are no longer available) a great system.

    It is indeed a big step from bamboo and gaff to unstayed carbon. It is extremely refreshing, and moderately unusual, to see someone on these forums who is big enough to change their point of view based on the information posted here.

    Love your sailing stories. To what do you attribute Romany's success over Sunburst? Shorter waterline? Smaller rig? Higher windage? Less efficient water foils? Lack of a screecher? Non rotating mast?
    Don't you think that all these were more important than one being built from very bent ply bonded with epoxy and one from slightly bent ply bonded with phenolic?
    Or maybe it was nothing to do with the build method and simply that Romany was sailed by a very experienced racing sailor (your good self) and Sunburst wasn't?

    rob
     
  5. Richard Woods
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    Richard Woods Woods Designs

    Rob

    Why mention the Flica at all then?? A better boat to compare your to would be something like Afterburner. Similar length and weight, also strip planked

    We had only owned our Romany a couple of months when we raced it. It was our first race. My wife hates racing and only came with me because I promised to buy her a new dishwasher for our house if she crewed for me

    I think Sunburst's owner was an experienced sailor. The owners of the Whylie 40 that we also beat to the windward mark were certainly experienced racers

    You can see Kurt's comments on his blog. Catbuilder can probably make some useful CM comments

    Richard Woods of Woods Designs

    www.sailingcatamarans.com
     
  6. warwick
    Joined: Jan 2012
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    warwick Senior Member

    Thanks Rob for your frank and honest answers to the questions and showing us you are just as interested build techniques/advances.
     
  7. rob denney
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    rob denney Senior Member

    I used Scylla to compare build methods of similar weight and hence cost boats. The Flica video shows the speed and motion of similar weight catamarans to Visionarry, demonstrating that length was advantageous. Sorry if this confused you. If you have any videos of Scylla sailing, we can use them instead.

    Afterburner (Californian racing catamaran) is indeed strip planked and similar weight, but about 10' longer overall and unlike the Visionarry, does not have a single and 2 queen size berths, a sheltered cockpit, saloon with table for 6, toilet/shower, full galley with fridge/freezer or a rig that can be easily handled by one person. Unlike Scylla and Visionarry (performance cruisers), it is a very twitchy, overcanvassed racer with almost nothing inside. If AB was the boat in the Visionarry video, it would be flying a hull, with crew holding the jib and main sheets and the helmsman concentrating hard. If it was also sailing under main and working jib, it would be going maybe 3-4 knots faster.

    Length is a poor parameter to reduce to save money. A Visionarry with a 12m hull would save a couple of hundred dollars and maybe 50 kgs, but would be slower (except in very light air and flat water), less comfortable, less seaworthy, deeper draft with less overload capacity. Would cost more in a marina, and take a little longer to paint and scrub off, but these are "side issues" in the overall scheme of things.

    Goodo. So you are seriously suggesting that the shorter boat with less sail area, extra windage and water drag was faster because the hulls were built from slightly bent ply rather than very bent ply?

    I looked on Kurt's blog (he is doing some really interesting stuff, well worth a read for anyone looking for a boat) but could not see anything about infusion apart from a successful carbon daggerboard. Kurt is a visionary and was one of the first designers to show how easy vac bagging is for amateur builders. He is also a big fan of unstayed ballestron rigs. I find it hard to believe he has problems with infusion. Please post a reference or a quote if you are going to use other designers comments to support your claims.

    Kurt's blog does show (September 12th, 2011) a photo of a cracked shroud fitting, with the comment "These boats need someone inspecting the rigging every month."

    He also says (March 25th, 2011) about ballestron rigs "I’m sure the safety of these masts will make them the future of USCG certified sailing cats".

    rob
     
  8. sailor305
    Joined: May 2012
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    sailor305 future cat builder

    update

    I'd like to thank you all guys for your comments and suggestions.

    My requirements can be updated as follows

    a. 40' + light weight multi hull, oceangoing, safe, fast and easy to build
    (no dagger or center boards), shallow draft (max 2')
    b. payload 2.500 kg+
    c. free standing rig (bi plane, ketch or schooner) max 2 winches
    d. two small auxiliary outboard motors
    e. open but covered wing deck (for sun/rain protection and rainwater harvesting)
    f. accommodation for 6 to 8
    g. full overall standing headroom 6'5"+ (live aboard)

    Further comments and suggestions appreciated
     
  9. dialdan
    Joined: Jul 2008
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    dialdan Junior Member

    Voyager

    Bernd Kohler' s Voyager would probably suit
     
  10. sailor305
    Joined: May 2012
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    sailor305 future cat builder

    Voyager

    thanks for this.
    I've seen this new design and I like it.
    However, payload is a bit low for long term cruising and live aboard.
    I'm going to ask Bernd if there is a way to encrease
     
  11. guzzis3
    Joined: Nov 2009
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    guzzis3 Senior Member

    I realise you may be referring to other posts but it's also likely I have not made myself clear.

    If you choose a design mith an awful hull shape, rig, bad plans and no backup, lousy build method not thought out properly you'll find yourself in a very deep and expensive hole.

    If you choose a design from what I referred to as an A grade designer earlier you'll get a good seaworthy boat with well thought out accomodations, satisfying sailing and good safety.

    If your prepared to look at a proa Mr Denny's boats are a good choice.

    Probably your biggest problem is your spoiled for choice. Even eliminating what I regard as second rate options there are still quite a few good designers with broad portfolios.

    You posts at the start of this thread indicated cost was a big driving factor. What I was trying to make clear is that splitting hairs between worthy designes or getting distracted by rigs and hull skins is missing the point. If you want to keep total cost of build down you need to think hard about what YOUR labor is worth, what you can buy it for, how many hours the build will consume and do a properly detailed spreadsheet on ALL the little costs associated with the build.

    Let me offer a hypothetical:

    You choose design A because it can be built from X number of ply sheets, but then you discover you and your paid labor are spending dozens of hours fiddling with details, then you find it needs expensive, possibly custom, items, maybe the windows have to be a certain shape or proportion, or hatches, I don't know, but these parts end up being more expensive. That $1000 you saved on hull skins is long gone and the hole is so deep the sun is no longer visible.

    Scenerio 2, you buy plans from Mr Denny or Mr Woods, they have built the boat previously and are familiar with every step, every problem, they have incorporated cost effective solutions. You spend a little more on a hull skin but you save on the details, and when you go sailing the boat performs as expected.

    You will find it matters very little. Again any worthy design will sail well and offer good safety, just steer clear of unknown options. Mr Woods survived tremendous seas a few years back, losing his eclipse in the process. A horstman was capsized in a terrible hurricane many years ago, the same one Thomas Firth Jones discusses in his book. The only casualty was a diabetic gentleman who lost his medication. No trivial matter but the circumstances were dreadful and other boats suffered terribly in the storm. These people know how awful the ocean can be and they design with that in mind.

    Remember good crews have sailed bad boats sucessfully, and good boats have been often wrecked by careless crew and captain.
     
    1 person likes this.
  12. guzzis3
    Joined: Nov 2009
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    guzzis3 Senior Member

    a. 40' + light weight multi hull, oceangoing, safe, fast and easy to build
    (no dagger or center boards), shallow draft (max 2')

    Why ? Don't get me wrong I'm a huge fan of the lar keel but there is a good argument that retractables are safer in bad water. Probably I'd be more inclined to look at the boat overall and decide if it ticks my boxes.

    c. free standing rig (bi plane, ketch or schooner) max 2 winches

    ? Again if the rig works I wouldn't rule it out out of hand. Nothing wrong with shrouds.

    d. two small auxiliary outboard motors

    I am fond of outboards, but I hardly motor anywhere so...again I wouldn't rule out a boat because it didn't tick this box.

    e. open but covered wing deck (for sun/rain protection and rainwater harvesting)

    I would have thought that applied to cats but not really proas and tris ?

    Also it's not that hard to build a desalinator or a solar still. Plenty of sun where your planning to sail :) You might even consider harvesting condensation.

    Be aware too that anything other than foam sandwich has minimal resale nowdays. I know your not thinking of this now, but the time may come.
     
  13. Silver Raven
    Joined: Oct 2011
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    Silver Raven Senior Member

    Gooday 'guzz' 25 out of 10 for both posts.

    Excellently written & a great analysis of some of the important concerns facing 'sailor305' &/or anyone in his position. Very well presented & I'm sure as well as I hope that 'sailor305' & others print you posts out & use them as a reference paper for most of their future decisions. Thanks for posting - great positive advice. Ciao, james
     
  14. sailor305
    Joined: May 2012
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    sailor305 future cat builder

    analysis

    Thanks Guzzis3 for your comments, really appreciated.Originally Posted by guzzis3
    a. 40' + light weight multi hull, oceangoing, safe, fast and easy to build
    (no dagger or center boards), shallow draft (max 2')

    Why ? Don't get me wrong I'm a huge fan of the lar keel but there is a good argument that retractables are safer in bad water. Probably I'd be more inclined to look at the boat overall and decide if it ticks my boxes.

    c. free standing rig (bi plane, ketch or schooner) max 2 winches

    ? Again if the rig works I wouldn't rule it out out of hand. Nothing wrong with shrouds.

    d. two small auxiliary outboard motors

    I am fond of outboards, but I hardly motor anywhere so...again I wouldn't rule out a boat because it didn't tick this box.

    e. open but covered wing deck (for sun/rain protection and rainwater harvesting)

    I would have thought that applied to cats but not really proas and tris ?

    Also it's not that hard to build a desalinator or a solar still. Plenty of sun where your planning to sail You might even consider harvesting condensation.

    Be aware too that anything other than foam sandwich has minimal resale nowdays. I know your not thinking of this now, but the time may come.

    Thanks Guzzis3 for your comments, really appreciated

    I like dagger and centerboards, however they are expensive (much time to build) and remember I'm on a budget and have to cut costs.
    The system of the Harryproa is a different story because its multipurpose and doesn't require a trunk.
    Sure, there is nothing wrong with shrouds but again costs, weight and maintenance.
    A tri is off discussion, to build three hulls are more efforts than two.
    A water desalinator needs plenty of power, or?
    How does condensation harvwesting works?

    I'm checking already foam availability and pricing in the designated building country.

    Thanks again
     

  15. guzzis3
    Joined: Nov 2009
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    guzzis3 Senior Member

    Thank you for the kind comments.

    I'm no guru I've just seen a lot of people make the same mistakes. It seems particularly difficult on people trying to save money. They go after some designers claim or some specification that turns out to either be wrong or conciels other bigger issues.

    I knew a bloke years ago who chose a certain designers cat because the materials list called for about half what similar cats needed. He thought he was saving money. Too late he realised his mistake. I knew another bloke who bought plans and built a tri, and connecting the beam to float required cutting things up and resealing afterwards. It was just impossible otherwise.

    Any of the gentlemen I've mentioned previously and a few more besides can give you a boat that will build and sail well. Price will be roughly proportional to weight.

    I like dagger and centerboards, however they are expensive (much time to build) and remember I'm on a budget and have to cut costs.

    Making and fitting a daggerboard case is trivial, in fact I'd venture making the board and case isn't much harder than making and fitting a lar keel. What you get with a lar keel is nil handling, virtually nil maintenance and a much harder structure to break when you clobber that sunfish. Centerboards can be a tad more work but they do swing back...sometimes :)

    Sure, there is nothing wrong with shrouds but again costs, weight and maintenance.

    There is a discussion of rigs above. As I've said before if one system was ultimately superior eveyone would adopt it, that's why small multihulls aren't built in steel or aluminium, that's why no one builds in double diagonal anymore. The stuff with little to recomend it falls by the way. Same with designs. Good designers sell plans and boats get built. Seond rate designers find few customers and even fewer completed boats.

    It is entirely possible you could be happy with a douglas fir mast junk rig galvanised wire shrouds and timber blocks. Or then again you might not. :)

    A tri is off discussion, to build three hulls are more efforts than two.

    Again your not building 3 hulls. Your building 1 hull with accomodation and 2 floats which are (relatively) trivial. Depends on the design. Kurt Hughes has some rapid construction boats that could be built mighty quick and potentially cheaply.

    http://www.multihulldesigns.com/designs_stock/40dtri.html

    Not luxurious but 40' should be comfy fast etc...

    http://www.multihulldesigns.com/designs_stock/43tri.html

    and

    http://www.multihulldesigns.com/designs_stock/42cat.html

    A water desalinator needs plenty of power, or?

    Well to desalinate as much water as you'd harvest off a bridgedeck won't require too much power unless it's raining all the time :).

    How does condensation harvwesting works?

    If you have a refridgerator or air conditioner you put a catch tray under any cold walls. The humid air will condense on the walls and you catch the water running down. You need to keep the area clean and chemical free but the bonus is you get a cold area to sleep or keep food. You also get some at night as the air colls naturally.

    I'm checking already foam availability and pricing in the designated building country.

    Cores and epoxy are expensive but you can save something using vynlester or poly. Glass is a relatively small component. Price up a square meter of the foam poly glass and a sqm of ply with glass outside. make sure the ply is decent quality or your boat won't last long.

    Good luck!
     
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