Look Ma, No Rocker

Discussion in 'Multihulls' started by ImaginaryNumber, Apr 9, 2012.

  1. rapscallion
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    rapscallion Senior Member

    The rig reminds me of Norwood's pyramid rig somewhat. My cat has very little rocker, and seems to turn ok. It doesn't tack as quickly a monohull, but it tacks.
     
  2. ImaginaryNumber
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    ImaginaryNumber Imaginary Member

    Triroo, thank for posting more photos of Hitch's X-IT. To my eye it looks like this is a small amount of rocker, but not much. It also looks to me that the draft is considerably less than .9 meters. Perhaps it's not necessary to have much rocker when you don't have much draft.

    Masalai, I appreciate hearing from someone who's sailed on X-IT. It still surprises me that it tacks well, but I have to accept the word of someone who has sailed it. I once had a kayak with a deep forefoot. That forefoot sort of acted like a forward daggerboard. In some conditions it actually helped you turn by acting as a pivot point for the stern to swing around. But it was death in a following sea, as it tended to broach very easily.

    Here's a sketch of a Hitchiker 33 MKIII. Again, it looks like John went out of his way to make deep forefeet and minimal rocker.
     

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  3. masalai
    Joined: Oct 2007
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    masalai masalai

    Those images are available in 'my gallery' (along with a few other things. The forefoot is not as deep as it seems to be the knuckle is at or near the waterline - a similar arrangement that may be better seen on mine - in the early construction stages. - see "my little piece of peace" thread.

    A deeper forefoot ensures a long waterline length in local sea states and better passage performance. There is almost no inclination on my boat to broach in most points with a following sea - so confident am I now, that I may well let the autopilot steer when surfing on my next trip north, to better go and watch (photograph) the performance..

    When comparing draft by looking in profile, remember that the boat "X-IT" is some 53 feet in length. I do not know John very well, but somewhere I got the impression that John was significantly, a very innovative yacht-rigger. - - See if you can find stuff on his "WIRED" before the present owner reverted to conventional bridge-deck - bloody sacrilege to my mind...

    I also feel that John Glennie was more the "hulls & builder" in the early days and everybody was sharing ideas - none of this "patents crap" that stifles development of new and fresh ideas. To keep costs down and building simple, the Wharram Tiki series, can clearly be seen as part of the inspirational process, and what better way to assess performance by using hulls that have known traits and performance information. (A control set that will not blow the budget).
     
  4. masalai
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    masalai masalai

    If you seek to critique John Hitches legacy, look at the rig, Twin flat cut genoas on fast and easily driven hulls make for an excellent passage maker that is easy to handle single handed.

    - - Remember that most cruising is timed for downwind comfort or broad reaches in lighter seas.
    - - On the suggestion of John, I will select sails light enough to pick the early morning gentle wafts, and to cease sailing before the wind over the deck exceeds 20knots (more likely around 15knots over the deck).
    - - Never set the sails wing and wing - dead wrong thing to do.
    - - Set sails always on the same tack... TACK DOWNWIND - VMG is far better and there is the opportunity to go downwind faster than the wind.
    - - There is no need for spinnakers as tacking downwind is far quicker.
    - - What when the wind over the deck exceeds 15/20knots? anchor up or motor, It is a cruise, (not a race), and comfort is the essence, set the autopilot and enjoy a good lunch, glass or two of fine wine and a pleasant social chat about what you will do ashore.
    - - John has a small "blade" sail midships for stronger winds and to assist when sailing more into the wind. I am content to use the motors when needed.

    There are many more "tweaks" to set up for a hitch-hiker rig. all sails go to the masthead.
    - - Both sails have 2 sheets which go as far aft as possible (so build that chainplate into the hulls whilst in the construction phase).
    - - The sails may have a fairly long foot.
    - - Tacking is easier on the 'to-become-windward-sail' if the blade sail stay is lowered.
    - - When tacking set the new leeward sail FIRST.
    - - I have 4 stays all robustly made and attached to major bulkheads (the beam at the bows is supported by 2 major bulkheads and the chainplate is taped in place all the way down to the bottom of the hull.
    - - John on "X-IT" set the aft sheet blocks later further aft on welded aluminium tubular brackets to get the blocks as far aft as possible.
    - - I may end up doing something similar when I fit sails - so the main sheet blocks will sit aft and outboard of the rudder posts...
     
  5. groper
    Joined: Jun 2011
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    groper Senior Member

    Yeah not too bad, but i think an A-frame rig would be better suited to this application of twin furling genoas... like this one @ www.damsl.com - plenty of info on it here too.
    [​IMG]

    Reason being you have better sail balance rather than all the sail up the front, and 2 smaller sail options when it really gets blowing...
     
  6. ImaginaryNumber
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    ImaginaryNumber Imaginary Member

    masalai, in your post you mention planning your sailing schedule to take advantage of easier sailing conditions along coasts. But if you were to make an ocean passage in X-IT, how would you expect its skinny hulls to handle heavy weather, in all points of sail?
     
  7. masalai
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    masalai masalai

    Hi ImaginaryNumber.
    Not well, as it is designed for Australian tropical waters cruising... It could do it, as it is fairly fast, has huge under bridge-deck clearance and requires no foredeck work... But going around the capes and in the southern oceans would not be wise... A different type of sea with 40+knot winds and breaking swell - - "Not I said the fly"... I do not like the colder regions of the planet. With careful planning, the whole Pacific islands region awaits as well as the interesting parts of the Indian Ocean... To play in the Med and Atlantic and Caribbean, use the Panama Canal... Most reasonably well found boats could make those regions with care, weather-window-timing, and a good weather watch...

    Hi groper,
    That would demand re-engineering the hulls to take the load where those masts would sit. - - Right at the aft berth access. - - Also the additional wind-age, (bare sticks), would add significant load to anchoring. - not to mention complexity and cost of more aluminium section and welding of same...

    KISS rules... I will have 2 sails and less than 90 square meters in potential sail area which is too much for me... and more than the normal sail-plan for the boat... Damsl looks like the foresails are JIBS as they do not pass aft of the mast.

    My mast is set to be about 8 ft aft of "normal" and will slope a little aft too, and the genoa reach well aft of the mast to balance the CE position... Inferring that the sails will be nicely balanced...
     
  8. groper
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    groper Senior Member

    yes i realize that, but things become unbalanced as you reef them in (or partially furl them in this case) - you said your happy to motor in this instance when the wind picks up which is what youve designed for i guess. but personally i wouldnt be happy with that, if you have wind and lots of it, not being able to use it is poor sailboat design IMHO...

    Thats where the furling main and center jib would be great with the a-frame rig, you can partially furl these and still maintain perfect sail balance. All of the sails are still furling and there is still no boom...

    As for windage complexity and cost, the a frame rig sections are thinner, cheaper, lighter - the difference between either way is negligible so they say...

    As for rocker, i notice most of the very fast boats have the least rocker in the hulls. From the modelling ive done with Michlet, it seems that less rocker gives less drag at higher speeds whereas more rocker and zero transom immersion do better at lower speeds when comparing typical types of multihull (slender) hulls... as for tacking, ive read that shallow rocker makes it harder to tack also, but most of the racing multis with little rocker dont seem to have any trouble - so maybe its some kind of old wives tale this rocker thing - i do know that its much harder to tack without a headsail in my experience, regardless of the hull type...
     
  9. Leo Lazauskas
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    Leo Lazauskas Senior Member

    It is, but to maintain the same beam, draft and displaced weight, the length
    of the hull would have to increase.
     
  10. masalai
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    masalai masalai

    Balance may be only partially changed, as for roller furling, as the forward section is reducing as the foot moves upward... Not really a factor as by 15 to 20 over the deck I would have the sail totally down - It is light weight material to catch light airs early morning. . . . . The other option is to douse one and then the other as 17 knots of wind over the deck was approaching...
    and therefore will be totally doused and engine powered then... The tropical island regions to the north of Australia are either dead or squally and occasionally transitioning and somewhere in between. That is another reason for an easily driven light weight boat that accelerates nicely, even surfing when conditions are 'right'...

    Check somewhere in this forum where discussion raged for a while - I am talking of bare poles and 2 is significantly more than one and at present I have but a sixth for the radar.

    The rocker thing is a matter of looking at the whole picture and do not compare Monos against Multis as they do different things best in different ways. That is why some of the "cruising multi's" beat the racing mono's in the recent Brisbane to Gladstone... Mono's and Multie's do different things better and in different ways... On other conditions the story has been different. That is why one should pick a boat based on the region to cruise, the anticipated wind and waves - strength and direction... The nature of the use, the intentions of the owner.

    A live-aboard boat fully set up for permanent cruising can cost significantly more than a similarly appointed land based home and car package . . . but then other costs of land-living are avoided if one selects wisely and carefully... (avoiding the romantic issues that lead to an unused tax-write-off if you have a very good accountant & lawyer) . . . :D
     
  11. groper
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    groper Senior Member

    Im willing to bet, that once you can afford your "sails" and put them on, you will change your mind when it comes to motoring... ie, you will never want to motor unless its utterly unavoidable dauldrums type weather...

    Why? you gripe that you cant afford your sails, once you have them you will gripe about the cost of diesel and so your engines will hardly ever get used to save money/fuel...

    My father and I have cruised the entire east coast and coral sea regions for many years aboard his 43ft sailing cat... weve been thru all this so we know the issues at hand...

    You also realize that once you have your sails, the increased weight and windage will make you boat considerably less efficient to motor?
    You will also realize that having the sails up significantly dampens the rolling motion of the boat compared to motoring - so with comfort in mind, sailing is actually more comfortable than motoring.

    In winter when the climate is less hot and humid , between circa Townsville and the Torres straight, the average wind your likely to encounter will be between 15 and 25kts with most days over +20kts... your "its too windy" threshold means you will be motoring nearly everywhere unless you way up near the equator... i just dont think you will want to motor as often as you think is all im saying... id seriously consider a means or method of deploying a small sail so you can increase the windspeed you can safely manage to sail in... 15kts isnt much...
     
  12. masalai
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    masalai masalai

    hehehe, Why do you think the boat is named "CNO"? it will run on CocoNut Oil :D :D and anyway the burn rate at 3000rpm (continuous mode a touch over 80%) is about 3 litres/hour a mere trickle... I am getting old enough to be happy griping about "no-sails" and to continue to motor... 6 or 10 knots is quite comfortable... in my trials up to South Percy and back I could do 8.1 or 5knots (still & calm)...

    Remember I said OVER THE DECK wind speed and the boat is very easy to accelerate, and I have been surfing in CNO in a following sea, and got regularly to 19 knots but with the smaller 2 blade folding propellers could not quite hold a wave as then I only had enough blade to go 8.1knots in no wind still water conditions... (can go another half to 1 inch bigger pitch, as I still can rev out beyond max allowed engine rpm on the larger 3 blade fixed propellers)...

    It is planned as a "doldrums run" early summer season or when the monsoon trough is less active after march 2013 for the Samarai run from Cairns of some 480 miles, but until I go I will continue grizzling and bemoaning the cost of this and that and a desire for some extra piece of 'necessary' equipment... Seems to be a thing that most old people succumb to eventually... fearing death may intercede...

    15 knots over the deck is enough if I can keep near 10 knots vmg away from the wind (that would be a 25knot breeze) :eek: :eek: but that is in the realms of plans and dreams at the present time as I am now 67 - So will have to settle on diesels... Unless.....lotto.......?......benefactor.......... :D :eek:
     
  13. Triroo
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    Triroo Junior Member

    Scan one, wired.jpg (349.2 KB)
     

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  14. Triroo
    Joined: Feb 2008
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    Triroo Junior Member

    Wired four.jpg (292.6 KB Wired doing 11 knots.
     

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  15. Triroo
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    Triroo Junior Member

    008.jpg (261.9 KB) Johns New River Boat
     

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