Multihull manuverability

Discussion in 'Multihulls' started by rapscallion, Dec 28, 2011.

  1. Expandacraft
    Joined: Dec 2011
    Posts: 12
    Likes: 0, Points: 0, Legacy Rep: 10
    Location: Ruskin

    Expandacraft Expandacraft

    coming about

    So I didn't see anyone mention the relationship of the Center of lateral resistance and the center of effort as an important part of tacking a catamaran. Balance is the key. However, you need to take in account the shape of the hull, LOA, rudder effectiveness and a host of other factors.
     
  2. rapscallion
    Joined: Oct 2006
    Posts: 504
    Likes: 15, Points: 18, Legacy Rep: 132
    Location: Wisconsin

    rapscallion Senior Member

    Our wed night beer can multi fleet will most likely consist of a catry 27, an F24II, and a G32. My hope is that if we get some good multi racing on wed nights, the fleet will grow.
     
  3. Boston

    Boston Previous Member

    how would rocker effect maneuverability, for instance a Bolger style hull with a really hard chine VS a multiple chine hull form with some bend to it ?
     
  4. caiman
    Joined: Dec 2008
    Posts: 72
    Likes: 2, Points: 8, Legacy Rep: 57
    Location: Wales

    caiman Junior Member

    Rapscallion-The raceing in my Yacht Club is 'parochial' to say the least ,with a 'full grid' meaning 6 boats on a good day.All monos except my Tri.Can you,(or anyone else for that matter)please give any pointers as to how 'Portsmouth Yardstick' or any other method of mono/multi 'handicapping is fairly achieved?
    I've tried getting info from the designer of my boat to no avail.
    Richard Woods-let go of the tiller and the 'mono' immediatly tacked.Is this illustrative of Monos(generally excessive) weather helm, versus the 'light' helm of a Multi?Or is it something else?
    I have come to the conclusion,rightly or wrongly,that a Multi is a straight line 'Greyhound of the Sea' versus a Mono being a 'Jack Russel'.(I know,catsvdogs:D etc)
    Cheers
     
  5. caiman
    Joined: Dec 2008
    Posts: 72
    Likes: 2, Points: 8, Legacy Rep: 57
    Location: Wales

    caiman Junior Member

    Expandacraft-my Tri initially sailed with a great deal of lee helm(take your hand off the tiller to 'pick up a cup',scratch your bum etc and She would bear away and accelerate).I have reduced the rudder size(which makes the dagger proportionatly bigger).This has improved my boat considerably,and also made Her a bit quicker going through the wind.My current project is to increase the dagger area which I'm confident will increase the boats present (slight) weather helm,If/when that happens I will move the mast forward to it's original position,to balance that out to a situation of 'slight weather helm' once again.
    So yes,in my opinion,boat balance,as you say,will effect how the boat acts going through the wind.
    Anyone reading this,please correct/advise/give you opinion.
    Cheers,and a HNY to you all.:)
     
  6. caiman
    Joined: Dec 2008
    Posts: 72
    Likes: 2, Points: 8, Legacy Rep: 57
    Location: Wales

    caiman Junior Member

    Expandacraft-my Tri initially sailed with a great deal of lee helm(take your hand off the tiller to 'pick up a cup',scratch your bum etc and She would bear away and accelerate).I have reduced the rudder size(which makes the dagger proportionatly bigger).This has improved my boat considerably,and also made Her a bit quicker going through the wind.My current project is to increase the dagger area which I'm confident will increase the boats present (slight) weather helm,If/when that happens I will move the mast forward to it's original position,to balance that out to a situation of 'slight weather helm' once again.
    So yes,in my opinion,boat balance,as you say,will effect how the boat acts going through the wind.
    Anyone reading this,please correct/advise/give you opinion.
    Cheers,and a HNY to you all.:)

    Oops,sorry about the duplication-too much 'Sherry' in the trifle!!
     
    Last edited: Dec 30, 2011
  7. upchurchmr
    Joined: Feb 2011
    Posts: 3,269
    Likes: 249, Points: 63, Legacy Rep: 579
    Location: Ft. Worth, Tx, USA

    upchurchmr Senior Member

    Does anyone have experience with Richard Newick's tris and cats? They generally have quite a lot of rocker, particularly the tri amas. It would be good to know if they are generally good at tacking.

    The Buckaneer 24 was supposed to be very quick and positive in tacking, peoples comments generally centered around the long taperering depth of the bow as one feature (essentially rocker?). It doesn't seem that anyone will give the secret away.

    Marc
     
  8. Richard Woods
    Joined: Jun 2006
    Posts: 2,209
    Likes: 171, Points: 63, Legacy Rep: 1244
    Location: Back full time in the UK

    Richard Woods Woods Designs

    I don't think the OP wants to race on handicap against monohulls, rather just to race. I don't think you can ever have fair handicap racing between monos and multis. Remember only one person is ever happy with his rating.

    My brother's monohull is a Ed Dubois 24fter (Trapper 240) Typical of its type, it sails very nicely and has a balanced helm (once the right rudder rake was determined). So my Merlin/Strider catamaran are the multihull equivalent small trailable cruiser racers.

    But I found it more "twitchy" than a racing dinghy

    As I, and others, have said before, a hull is a 3D shape so you have to be careful when looking at just one view of a hull. Dick Newick's hulls are usually Veed rather than round bilge and so have more rocker.

    One of the biggest factors affecting trimaran tacking speed is the height of the outriggers above the water. Clearly a boat like a heavy Piver with all three hulls well immersed will not tack as fast as a boat with high outriggers (like the Buccaneer 24 or a Newick) even though they are also Veed and have lots of rocker

    Richard Woods of Woods Designs

    www.sailingcatamarans.com
     
  9. bruceb
    Joined: Nov 2008
    Posts: 1,251
    Likes: 44, Points: 48, Legacy Rep: 214
    Location: atlanta,ga

    bruceb Senior Member

    Monos vers multis

    I have a modified Buc 24, I race in a mixed fleet of well sailed sport boats as well as several multis- Corsairs and a Reynolds 33, and yes, there are conflicts, but not due to "lack of tacking ability". I can win a tacking duel with a Melges 24- but we will both lose out to boats that didn't try to. I have had bad experiences with monos that did not anticipate how fast a multi can accelerate- and I had to repair my float bow from just such an encounter- not good. Space does matter, and starting lines need to be adjusted longer for even one multi, and the general starting area HAS to be kept clear of boats not in the current start.
    I think that since we as multi sailors are usually in the minority, we need to be extra careful to be "good citizens" and try to be as "nice" to other racers as possible. Sometimes, to be invited back is more important than shutting out a couple of monos at the start. I like to be first at least as well as anybody else, but "usually" try to curb the most aggresive tactics.
    I haven't seen that one type of multi has any real advantage over another- crew work, sailing ability and boat prep makes most all the difference. B
     
  10. messabout
    Joined: Jan 2006
    Posts: 3,217
    Likes: 367, Points: 83, Legacy Rep: 1279
    Location: Lakeland Fl USA

    messabout Senior Member

    Back in the day I had an Australis. It was scary fast in a striaght line but it was a ***** to tack. Try as I might I never quite mastered that boat. With a Tornado I had very little trouble tacking. I would like to think that the design of the boat had a lot to do with the difference. Australis was pointy at both ends while Tornado has a transom of sorts and rocker. But then it could have been the inadequacy of the skipper....me.
     
  11. harrygee
    Joined: Feb 2010
    Posts: 23
    Likes: 2, Points: 0, Legacy Rep: 25
    Location: Tasmania Australia

    harrygee Junior Member

    I have a tri which started life as a soling, a 27' mono. I raced it for a season as a mono, then as a tri, using the same rig and sails, against the same fleet.
    The tri tacks as quickly as the mono in all conditions that I've experienced and turns quicker in close manuevring. It is faster in all conditions. It does lose momentum when headed, being several hundred pounds lighter - the 560 kg keel that I removed was heavier than the multi bits. The floats have moderate rocker and they barely kiss the surface as she comes through the wind in flat water.
    So the tacking ability of a multi versus mono depends on several factors but the fact of it being a multi isn't one of them.
    In mixed racing, you're likely to find that lack of momentum will cause scarey moments - we stop suddenly in a lull, heavy monos don't.
    Good luck with it.
    Harry
     
  12. upchurchmr
    Joined: Feb 2011
    Posts: 3,269
    Likes: 249, Points: 63, Legacy Rep: 579
    Location: Ft. Worth, Tx, USA

    upchurchmr Senior Member

    Harrygee,

    Any pictures of your Soling-Tri? Have you shown it in a thread?

    Very interested in any information.

    Marc
     
  13. upchurchmr
    Joined: Feb 2011
    Posts: 3,269
    Likes: 249, Points: 63, Legacy Rep: 579
    Location: Ft. Worth, Tx, USA

    upchurchmr Senior Member

    Richard,

    I would appreciate some help. What is the correlation between Veed hulls and more rocker? Should I expect better tacking with Veed, more rocker, just out of the water amas or round bilge, less rocker, just out of the water amas? Are there no Veed, minimal rocker designed boats?

    I note that Kayaks converted to Trimaran sailing typically talk about poor tacking. These would be typically round bilged in the center, Veed in the ends, with little rocker. Whats the connection? I do assume that some of the issue is improperly placed centerboards and small rudders.

    Quote - As I, and others, have said before, a hull is a 3D shape so you have to be careful when looking at just one view of a hull. Dick Newick's hulls are usually Veed rather than round bilge and so have more rocker.

    One of the biggest factors affecting trimaran tacking speed is the height of the outriggers above the water. Clearly a boat like a heavy Piver with all three hulls well immersed will not tack as fast as a boat with high outriggers (like the Buccaneer 24 or a Newick) even though they are also Veed and have lots of rocker

    Richard Woods of Woods Designs

    www.sailingcatamarans.com[/QUOTE]
     
  14. Richard Woods
    Joined: Jun 2006
    Posts: 2,209
    Likes: 171, Points: 63, Legacy Rep: 1244
    Location: Back full time in the UK

    Richard Woods Woods Designs

    In haste as its new years eve

    Its not really possible to have a Veed hull and no rocker. Try drawing one and you'll see what I mean. A boat needs displacement, and usually comes to a point at the bow. If you have a Vee in the middle you cannot carry that Vee to the bow without also generating some rocker

    Your second comment just shows that one cannot convert successfully one thing into another. I imagine one other problem is the low outriggers

    Richard Woods of Woods Designs

    www.sailingcatamarans.com
     

  15. cavalier mk2
    Joined: Mar 2010
    Posts: 2,132
    Likes: 56, Points: 48, Legacy Rep: 214
    Location: Pacific NW North America

    cavalier mk2 Senior Member

    Newick amas used to be a rounded v shape with lots of sheer forward with high bows to prevent tripping. The rocker kept light air wetted surface down and worked with the main hull shapes that were almost double ended at the waterline. These boats went over the waves rather than through them. He gradually has shifted to a more rounded ama with less sheer and rocker with a fuller main hull stern on his performance designs, I imagine these tend to slice through more of the wave tops while the older ones tend to pitch more. Interestingly the old Nicol Vagabond MK2 had sharper rounded v amas with a high bow curve but much less rocker for a flatter run. These worked well with the wider transom stern and were used to help maintain the main hull attitude at speed giving more bearing aft when needed for "semi-planing" yet keep things from being too wide for light air performance. I haven't heard anyone complain about either Newick design tacking though I think the older ones might be faster to come about in a sea. The Nicol works well sailed like most tris- keep the speed up etc...ease the main if you don't get the jib in fast enough etc....
     
Loading...
Forum posts represent the experience, opinion, and view of individual users. Boat Design Net does not necessarily endorse nor share the view of each individual post.
When making potentially dangerous or financial decisions, always employ and consult appropriate professionals. Your circumstances or experience may be different.