easy, fast to build multihull with simple rig

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

  1. sailor305
    Joined: May 2012
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    sailor305 future cat builder

    Hello and many thanks to all. Your comments are helpful and appreciated.

    Sure a distressed sale could be a solution and I've seen some like the Corinthian tri already.
    I like trimarans but usually they are offering less interior space which makes long term cruising not so pleasant.
    However, stepping aboard for viewing has been enormous disappointment . Pics intend to show everything better than the reality. Most of these boat are aged and due the lack of funds not in good shape at all. That means additional expenses and replacement needs will come up sooner or later.

    A new boat is new and beside that you can do it the way you like it within your budget of course .
    Richard Woods comments are in encouraging and additional stuff can be added little by little as an ongoing process. That way you are going to purchase really what you are in need of and not all the nice to have stuff which is mostly rarely used.
    The KISS principle seems to me mostly forgotten nowadays.

    A used mast is a good idea but hard to get in the designed building area and shipping costs of masts are obsolete. I guess it would be less to build one based on local material (wood)there.

    Although not my real problem but the discussion about thinner and easier to bend ply is interesting too. What about using two layers of thinner instead of a thick one?

    Due nobody comment the rig issue it seems to me best to go traditional although I'd like to try something simple like the Wharram wing sail rig. The junk rig is going also in that direction but as far as I learned so far it seems to be a low speed one and a multihull isn't for that.
    May be somebody can add some comments on cheap but efficient rigs?

    Thanks again,
     
  2. ImaginaryNumber
    Joined: May 2009
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    ImaginaryNumber Imaginary Member

    Pete Hill, of Voyaging On A Small Income fame, is building a Bernd Kohler extended KD860, and putting bi-plane free-standing masts on it fitted with split junk rig sails.

    Brief discussion here and following:
    http://groups.yahoo.com/group/k-designs/message/2862

    Construction photos here:
    http://groups.yahoo.com/group/k-designs/photos/album/264449533/pic/list

    You have to be a member of the group to view them.

    Also in the photo group is a single pic of his earlier China Moon catamaran, also with bi-plane masts, but with flat junk rig sails with jointed battens.
     
  3. Richard Woods
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    Richard Woods Woods Designs

    You would use two sheets of thin ply on a double diagonal boat. But you would only do that for round bilge hulls. Plywood is great for flat panels, no need to make your own from two layers when you can simply buy a thicker sheet

    As I said before, the basic spar is cheap enough, its the fittings that cost money. And every sail will cost you. As with engines one big one is much cheaper than two small ones and it's usually more efficient and easier to handle as well.

    See my FAQs page on my website where I talk about alternative rigs

    Its is always better to build a good small boat than run out of money and finish a bigger one with cheap old worn-out gear

    Richard Woods of Woods Designs

    www.sailingcatamarans.com
     
  4. masalai
    Joined: Oct 2007
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    masalai masalai

    Here is one concept at 30ft purportedly built for around 21k in Townsville - - http://www.thecoastalpassage.com/cheapcat.html - - The design was drawn on the back of a "beer carton" but the pictures should be enough for most builders... Leon apparently built several... Sufficient for coastal passage making in good weather... Almost ideal for inter-island hopping with the occasional longer passage with care and caution... I reckon arriving at most villages a ready team of volunteers could be found to drag it over the sandbar and into quieter waters...

    The rig may be simpler with a "hitch-hiker" type rig, add for pointing higher into the wind, a blade sail. - - The rig is basic with the mast set a bit further aft, no mainsail, and 2 flat cut genoas to each bow...
     

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

    Thank you

    Gooday Richard. As in 'heading' - THANK YOU Your honesty & genuine answers are so appreciated. I'm an older semi-retired yacht builder/repairer & you make us all very proud - due to the manner in which you conduct yourself & the valuable information that you pass on. Thanks mate !!!!

    Now - as to why anyone would use 2 thinner sheets of ply (or any other flat panelling) as a choice over 1 thicker piece. Well let's try this & see what you think. Please
    Take a thin sheet of ply - then bend it in - to shape - it's now under tension - now apply glue or a resined fiber cloth (of any kind) - then apply the second - thin layer of ply & bend in to match the first - plastic staple them together - - wait until fully cured - - then bend the whole laminate in another 5% or so. - - Reason for this method - sheets are much lighter & easier to handle - the resulting thickness is 100's of times stiffer for the same weight as would be a single thicker piece of ply & it's already partly water-proof. Yes/no ????

    Now to spars; 1 is always better value than 2. A conservative - limited wing mast - can be - very cost effective; reasonably easy to build (once you get your head around just how simple it really is to do) - reduces the cost of sails - - rigging is much cheaper because there is much less of it - KISS is always the winner - if we - the 'nuts' on the helm - don't mess with the KISS principles to much. If I could afford the right programs & had the abitlty to draw pictures in here I would show you how simple it really is - we did it many time - several years ago - - so far - nothing has broken & I'm sure we could do much better - these days.

    I've learned a different value to yours about engines, which alas is - healthy for us & the industry.

    THANKS again - you input & knowledge is very well recieved. Caio, james
     
  6. Silver Raven
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    Silver Raven Senior Member

    Gooday Mike. Your choices of multihull & rig are endless. There are many 1000's of yachts for sale in your neck of the woods.

    Look hard - be critical - nit-pic - bargin hard - pay cash - get a receipt & all paper work in top order before parting with your hard earned cash. Spen at least 3 months looking - all over that vast area your in. Keep positive - enjoy the journey of looking - have the greatest time sailing THEN - remember to keep us all informed - as we will learn much from your searching for the 'right' vessel.

    Ciao, james - aka - 'jj-geri-hat-trick'
     
  7. Richard Woods
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    Richard Woods Woods Designs

    Thank you for your thank you!

    But surely that means you have a round bilge hull, just as I said?

    Years ago I had some independent structural analysis done on slightly curved panels. Those tests proved what I suspected, that there is no benefit in slightly curving a panel. You don't make it significantly stiffer. As a catamaran hull is only slightly curved fore/aft it is no stiffer than a flat sheet. You only gain stiffness around the round hull

    Again, from the tone of the OP's first post I don't think he wants a rotating wing mast, however efficient. And I don't think many cruisers want them either. I prefer to have a masthead tricolour light and wind direction indicators. A mast is quite a useful place to fit a radar as well. It is hard to stop a rotating mast from flexing when deeply reefed, so wingmasts are often heavier than fixed ones as they cannot be stayed as effectively. Weight aloft adds to pitching so slows the boat.

    And, yes I have had rotating masts on boats. Not just on my current boat, but also on earlier racing designs, while I also fitted one on my first liveaboard cruiser back in the late 1970's.

    Richard Woods of Woods Designs

    www.sailingcatamarans.com
     
  8. Gary Baigent
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    Gary Baigent Senior Member

    The point is, Richard, Sailor305 is asking for suggestions and aiming for a basic boat that is not expensive ... and Silver Raven and I are suggesting just that. And although many think these are sophisticated and complicated solutions: round bilge, thinner ply, glass reinforcing and wing masts, in reality, they are not, they're just basic, nor difficult to build, control or maintain. Plus the results are a more aesthetic design. Slab sided hulls and straights constructed out of heavier materials, to my eye, look clumsy and unattractive. If you're going to the expense and considerable time involved in creating a boat, a boxymaran is not what you want. Just imo of course.
    You are completely wrong with your curved panel conclusions (I'll say no more, just refer again to the Gougeons) also your wing mast criticisms seem to be based on mythology and not practical experience; this regarding difficulty to build, weight, top heaviness, flexing when reefed? wind indicators, difficult to control and other mistakes. My point is: if you're going to build a mast, why not make one that takes little or no more time or expense to build, weighs the same (or less) than a secondhand alloy rig, plus is many times more efficient in gaining sailing performance. Even a cruising boat crew enjoy speed without effort.
     
  9. Silver Raven
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    Silver Raven Senior Member

    Gooday Richard. With all respect & expressed gratitude - I'm looking for your guidance.

    I can't seem to equate your "independant structural analysis" as to flat, thick single sheet stiffness compared to multiple sheets - of the same total thickness when bent as little as 5% to 15% & each pre-stressed before adding the next sheet - being no stiffer than the single sheet for the same given weight - when in-situ.

    No I was not "surely that means you have a round bilge hull" saying that at all. In fact I didn't mention that at all & NO you are not correct in that assumption.

    Your personal preference as to "tri-color lights", radar, etc has nothing to do with the effeciency of either - rotating nor 'wing-mast' - not one bit what so ever. Your assumption that they must automatically weigh more or need more thus heavy rigging is completely wrong & can not be substantiated.

    With all due respect, instead of - telling - me what I said - why not try & read what I wrote & try to understand - that I was only respectfully asking a question - not in any way trying to tell you anything or challenge your knowledge.

    I'm would like to think that - there is room enough for all of us in these discussions & opinions - as - in yacht design - there are no absolute facts.

    With respect - I'm looking forward to your opinions on these topics & to Gary's comments as well.

    It is my only desire that with a thorough open discussion - that '305's' (Mike) questions might be both answered &due to that he'll gain more knowledge to allow him to make a better evaluated decission with his future choices of a yacht to sail safely in & I do hope you'll contribute with your knowledge - at this level. Ciao, james
     
  10. gypsy28
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    gypsy28 Senior Member

    In regards to a 2nd hand mast versus a homebuilt rotating wing mast, I'm sure I could build the thing pretty cheaply, but I haven't got a clue on how to design one, so in reality is it easier/faster/simpler to design/build a wing mast than buy a second hand aluminium stick?

    How much would it cost to have someone design/engineer a wing mast for say, a 35 ft cat?

    Now if I had the design knowledge on wing masts that Mr. Baigent or Mr. Silver Raven had then it might be a different story and I'd design myself, but if I've gotta pay big money (presumably) for a design and then build the bloody thing, I'll agree with Mr. Woods and buy a cheap used Aluminium stick

    But who cares what I think? (awkward silence......) anyone?:cool:

    DAVE
     
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  11. Silver Raven
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    Silver Raven Senior Member

    Gooday David. WE all care - or should do - what everyone has to say & think. I know - I sure am interested in you in-put. The original question put - by '06' was about a cost effective multihull to be built in the PHilippines or somewhere in SE Asia. They are building rather sofisticated yachts & mast up there & have been doing so for a number of years.

    There are many many people around much smarter than I'll ever be & I'm sure someone would step up to the plate - with a design for a simply built mast - regardless of wing-mast or just an ordinary mast - & a person - could build one for a very good price. The technology has been around for many years & it's not all that expensive to buy the materials. Kelsall & Denny spring to mind as experts in their field.

    I'm not for one moment disagreeing with what you said. You have made your point very well. It might seem a daunting task. but it is really not - once you get your head around it. Neither Gary nor I nor Doug Lord nor Steve Clark & many others are - super stars - we've just been - 'playing-around-with-boats' for a long time & managed to fudge our way through. Easy - peasy - just ask & everyone will 'gather round' & try to assist.

    Thanks for your contribution. Valid comments. I respect them. Ciao, james
     
  12. Gary Baigent
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    Gary Baigent Senior Member

    Gypsy, think of a wing mast as just being a long skinny hull, but simpler. If you can build a hull, or a beam, then by comparison, wing mast construction is no problem. For a start it is the same section in chord and thickness up to as far as the hounds, then it tapers, usually from the leading edge, much the same but far less complex than the bow or stern sections of a hull. There is a lot of mystique and aerodynamic BS surrounding wing masts, ignore it.
    Here is a basic wing mast, this one designed by David Knaggs but they all follow pretty much this design, some thicker, this one is quite fine; you lay up an I beam, (the small circle is the bearing at base) cut out the frames, rip leading and trailing edge and epoxy it all together. When cured, glue and bend the skins on, then reinforce as shown in the drawing.
    If you hunt around this web site you'll find more detailed construction directions. Okay here's the bones of a beam, (this one with a box in place of an I) but exactly the same approach.
    Okay here's another old wing mast but this one with a catenary trailing edge above the hounds; usually it tapers at front. Some wing masts have no taper at all, just the same section from base to peak (but looks a bit crude to me, also more weight up high.)
     

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  13. masalai
    Joined: Oct 2007
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    masalai masalai

    Find a friendly hobbyist aircraft engineer - he/she may do it for the exercise... You may have to advise them of the load from the sails on the mast-step - My mast step is designed to carry 6500kg in compressive load from up to 2 x genoa in breezes of less than 20 knots over the deck - most of that load is passed from the top of the mast as there IS NO MAIN and NO JIB... it is called a Hitch-Hiker rig after the designer/developer My John Hitch - His boats include "Wired" and "X-IT" He was still cruising when he was 75 - images of "X-IT" in my gallery...

    See above...

    Wing masts are difficult to "turn off" and your boat may want to sail ALL THE TIME even when at anchor or tied to a marina pen... "Oops there goes another marina berth"... :D :D :D
     
  14. cavalier mk2
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    cavalier mk2 Senior Member

    Darn Gary, I want to build one now...
    Sailor305 If you are looking for a simple sheet ply Trimaran design check into John Marples Seaclipper range, the 34, 38 and 41 all fit your description though one of Richard's boats would probably go as fast and carry more. I agree with Gary and James about round hulls not being "harder" to build. However a sheet boat does lend itself to a sort of therapeutic, just drive nails, build approach.
     

  15. farjoe
    Joined: Oct 2003
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    farjoe Senior Member

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