K24T versus Buccaneer 24

Discussion in 'Multihulls' started by gpb, May 22, 2009.

  1. caiman
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    caiman Junior Member

    Having difficulties loading pics.
     
  2. bruceb
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    bruceb Senior Member

    rudder design

    Caiman, is the rudder shaft angled or vertical? (in relation to the waterline) Bruce
     
  3. caiman
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    caiman Junior Member

    Yes,when sailing the rudder shaft is vertical in relation to the waterline.
     
  4. caiman
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    caiman Junior Member

    Third time lucky?If you zoom in,the rudder is laying on the deck in the cockpit.The red bit is the 'cassette',the black bit is the rudder blade.
     

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  5. caiman
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    caiman Junior Member

    The pics I have are mostly over 2MB.This is why I'm struggling with them.
    This is a line drawing from K.H.'s site
     

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  6. oldsailor7
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    oldsailor7 Senior Member

    Thats one great looking boat. :D

    Should be fast too --providing it's not too heavy.
     
  7. bruceb
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    bruceb Senior Member

    rudder

    caiman, If the shaft is vertical, then it does get back to balance. Tris and wide-transom flat bottom monohulls both seem to "skid" their turns and really load their rudders. I think the pressure build up on one side of the rudder is even higher on tris because the hull is so narrow that one side of the rudder stalls in the hull turbulence. Sort of like a tail stall on an airplane. About 15-20% of the rudder area in front of the shaft usually works, but every boat is different. Your cassette system looks well engineered and very practical so maybe a higher aspect (longer) rudder with less cord would help most. Bruce
     
  8. bruceb
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    bruceb Senior Member

    rig question

    Caiman, How much can you cant the mast with your set -up? It looks nice and simple:) Bruce
     
  9. caiman
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    caiman Junior Member

    I understand and agree with your theory about one side of the blade stalling.And yes,the boat has the feel of spinning about the dagger board.She is very responsive.I havn't been out to the boat recently,but I'try to measure how much either side of centre that the tiller travels and so be able to work out how many degrees the rudder is moving.I will also try and guesstimate how much area of the blade is forward of the stock.The rudder is not a parellel sided blade.Also,the leading edge of the blade is not parellel with the stock.I will hopefully be getting a new camera Monday so can post some pics.I agree,the cassette system is good.However,the rudder is either rigged or it isn't.Steering with the rudder is impossible unless it is fully down.I ran aground on a falling tide recently(just after having my best sail to date! Sods Law) and had to go over the side to sort it.The blade must be directly dead ahead to clear the bottom of the transom.The tiller removed,and then the whole assembly pivots around the top mount.I have steadily been removing the mast rake !!When I set the boat up this year,I followed the settings that the boat came with,The forestay was fully extended,the shrouds were at their shortest setting.Rigging tension was achieved by runners.The mast was at it's rearmost setting.When I initialy sailed the boat it had lee helm.It was impossible to let go off the tiller for an instant,the acceleration when the boat started to bear away was compounded by the tiller slamming over to full lock.My first thought was to rake the mast aft.There was no adjustment left on the forestay.I contemplated adding a shackle to increase the length.If I had of done,the rotating mast foot would have fouled the back edge of its socket which allready had a cut out on the back edge.I was then lucky enough to be given a photo of the boat underway.EUREKA !! From the pics it was immediatly obvious that the mast had been raked aft to an excessive extent.To rake the mast back further was not the answer.The only option left was to move the mast foot aft.This I have done.The lee helm has all but gone.I am reluctant to move the mast past the middle position of the tracks new location until I've been out in a bit of weather.The reason being that I would expect an increase in 'weather' helm as the draft of the sail moves back.I also want to resolve my rudder problem.Although the runners still tension the rig,at the moment I just set things up reasonably tight and leave it at that.The pics are at eight knots after moving the mast.The 'eureka' pic is too big to load.
     

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  10. caiman
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    caiman Junior Member

    Eureka?
     

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  11. oldsailor7
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    oldsailor7 Senior Member

    Caiman.
    She certainly is a pretty looking boat.

    In all your shots the set of the mainsail would give you horrible weather helm. You needed to move the traveller out and harden up the mainsheet to straighten out the leech of the sail. You should aim to get the angle of the sail to the apparant wind the same all the way up. The boom is sheeted far too far in and the top of the sail isn't doing much at all.

    My 2c worth. Paddy. :idea:
     
    Last edited: Jun 23, 2009
  12. caiman
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    caiman Junior Member

    Your comments are worth more than 2c old sailor but please explain.As you correctly noticed,I have been sailing with the traveller well up to windward with the boom more or less sheeted to the centre line of the boat.I agree that this puts twist into the main.I thought that this was desireable to take advantage of the change in wind direction caused by drag of the wind travelling across the water, combined with the coreolas(?) effect of the turning earth?Also to take advantage of the wind drawing aft in a gust?I have been experimenting with the sail trim underway(traveller,mast rotation,sheeting)and have been trimming to the tell tales.This seems to have been successfull ie more speed.In the beam on pics I was trying to go as fast as possible,and so would have adjusted everything to get the streamers streaming as best I could.Please note that in the shots from aft,I had slowed down so that the 'photographers' boat could catch up.What would be your tactics?Would it be better to ease the traveller to leeward,and sheet in harder if that meant the streamers were stalling?I am very new at this so all input is appreciated.I understand when you say that because the main isn't drawing fully,the 'torque' of the jib overwhelms the 'torque' of the main and therefore pivots the boat around it's centre of lateral resistance.It all seems quite ironic in that all the other boats I have sailed(not very many) the goal has been to reduce weather helm!Do you have any comments on the mast rake/position?Thanks for your kind words about Caiman.When I went to view Her,I knew within 30 seconds of seeing Her dismantled on the trailor that She was the one.She tows beautifully, and it was a struggle to keep below 70mph on the motorway with a 2.8 SWB Isuzu 4x4 towing Her Home.Setting Her up for the first time was simple apart from sliding the front beam into place which was very difficult.I will need to address that problem during the Winter.Here's another pic.I apologise for 'showing off' my boat !!
     

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  13. oldsailor7
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    oldsailor7 Senior Member

    Looking at pics 3. & 4. you can see what I mean.

    In sailors terms the sail looks like a "Donkeys Hind Leg".
    Having straightened out the leech, you just ease out the traveller until all the tell tales are flowing smoothly. The sail will then have a nice uniform shape from top to bottom.

    In boats of this size you don't have to worry about the coreolas effect or even the wind gradient.

    Cheers. Paddy. :D
     
  14. caiman
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    caiman Junior Member

    Excellent food for thought.I will definatly try your recomendations next time out.This is the kind of help and advice I'm looking for,thanks.What are your ideas on the pics of the rudder?
     

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  15. oldsailor7
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    oldsailor7 Senior Member

    Caiman.
    It's hard to tell from the pics, but I would suggest there is too much of the rudder forward of the pivot centre. This would account for the over centre "Snatch" when helming.
    The alternate spade rudder for the Buc 24 is about right with 25% of the rudder area ahead if the rudder post. :idea:
     
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