crowther 10 modifications

Discussion in 'Multihulls' started by lincpike, Sep 6, 2004.

  1. lincpike
    Joined: Sep 2004
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    Location: Mackay Queensland Australia

    lincpike New Member

    Hi

    does anyone have info, plans, moulds, anything which would me with modifications to my Crowther 10 length, cabin height, anything.

    Linc
     
  2. tonysuncat
    Joined: Jul 2012
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    tonysuncat Junior Member

    Sorry LLinc I just got your message

    I oiwn a cother 10 spoerts by beach marine and it has just conme out of survey so i have lots of info for you.Mine has 1,7 mtr transome extensions by Schioning and they transformed the boat
     
  3. catsketcher
    Joined: Mar 2006
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    Location: Australia

    catsketcher Senior Member

    C10

    Gday Linc

    My mum had a C10 built by beach marine in 1983. It was one of the second generation models. The first ones out of the moulds were thin hulled versions but a few - Rush and Duet had more semi circular rather than elliptical hull shapes.

    Like Suncat my mum's cat (Duet) was transformed with the addition of a transom extension. The boats are pretty short for their width and weight so an extension is a good thing to do. There are a couple of different ways of building them.

    Most C10s had boards but Duet had minikeels. If I had gotten Duet instead of building my own cat I would have done a few things.

    Extra extensions - about 5 ft in total
    A raised centre section of the bridegeck. Nowadays you could cut the centre section of the deck off between the jib tracks and raise this so you get standing headroom in just this short section. Continue this aft over the cockpit to help the looks and give you a sun shelter. A friend did this on a Windspeed and it worked well.
    Maybe change the backstays. I would like a square top fully battened main so would consider moving the chainplates forward and getting rid of the backstays. Then again the Easys have this type of rig for a reason but I do love an elliptical planform in a main.

    cheers

    Phil
     
  4. tonysuncat
    Joined: Jul 2012
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    Location: townsville

    tonysuncat Junior Member

    crowther sports beach marine

    Hey Phil
    You know what you talking about.Maybe you can give me some info on my boat

    I bought it off a guy who had the boat made to survey MSB stamped and Lock Crowther signed off on the plans I think in 1985.I bought it 1997 and the guy finished it near the Army Barracks as he was in the Army.He was colour blind and never put it in survey.
    The boats name is Nullegai and has Suncat Sailing written on side to hide that ugly hull/deck join
    The dimensions are 10mtr by 6.98mtr and weighs 4.6t and was an open bridgedeck with a sucken cockpit and terrible minikeels and a ducati diesel with volvo hydraulic drives

    My mast is sparcraft 13 mtr <10mtr boom to top>which I am searching for mast section top add as much to as possible

    I am out of survey so i can modify as much as I want to, or can afford
    I want to put a daggerboard in centre nacelle and cut off the mini keels to give some windward preformanceand try to get some better preformance The keels look like a farmer designed them<is my boat solid glass from the water line down.
    The steering is Hydrive hydraulic and the boat never tracks straight so this is a prioity to fix

    Any suggestions to make her more efficient would be welcomed

    I am on Magnetic Island <for 14 years>and love the boat as she serve me well as a bus for 32 passengers and paid for herself in income earned
    I will get Geoff Schioning to advice me because it is money well spent
     
  5. catsketcher
    Joined: Mar 2006
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    catsketcher Senior Member

    Gday Tony

    I don't know your boat - I did know two Sports cruisers back in the day.

    I agree that the keels are terrible. If they are the same as Duet's (and as they were both beach marine boats they should be) they are a terrible section with the max thickness at the back of the section and the section is made from three flat sides. They couldn't even be bothered to bend the ply in the mould!

    Cutting them off could be fine but hanging a board off the nacelle could be an issue. There will be a huge torque on the nacelle. You can work it out.

    If the nacelle touches the water and the top is about 500mm above the water that gives us 500mm there plus about 1000mm to the centre of pressure of your centre board if it is 2000mm under the water. So all up torque is 1500mm.

    The force from the centrboard will be equal and opposite to the force from the rig.

    http://www.wb-sails.fi/news/SailPowerCalc/SailPowerCalc.htm

    From this web page on my estimation of your boat (and with the apparent at 100 degrees to get maximum load) I get 427kg force from the rig. This needs to be equalled by the foil so it will also exert 427kg in the opposite direction. (I know I shouldn't use kg for force but it may be easier to understand than Newtons)

    So the board will exert a torque of 427kg multiplied by 1.5 metres = 640 kg metres. The nacelle is around 800mm wide so the torque on the nacelle top will be 640/0.8 = 800kgm. This is the torque at the top of the nacelle - now that is only just enough to cater for the load - you should at least increase this by double and then some. The beam was never designed for this load and niether was the nacelle.

    So what does this mean - that little nacelle will not handle the load unless it is substantially beefed up and the loads distributed to the hulls - not the beams. The best way would be to put ONE board and case in whichever hull you find easier to access -a la Oram. Nice big board and no worries. I have a one board cat and never found and issues in helm.

    Cut the heavy keels off, put a roachy main on, put a square case at the side of the hulls and use lots of uni and double bias glass to glass the case in and you will have a great boat. I would make the case square shaped and a little longer than the boards chord. This will let you move the board back and forth and angle it slightly to get the helm you want. If there were sisterships you would check their balance out but as you want to make changes it is better to use a square case and move and angle the board to get it right. When happy you can put in filler pieces to smooth water water flow and keep the board where you want.

    cheers

    Phil
     
  6. waikikin
    Joined: Jan 2006
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    Location: Australia

    waikikin Senior Member

    http://www.boatpoint.com.au/boats-for-sale/boatdetails.aspx?R=12080118

    The link is to a modified Beach Marine/Crowther "Sports Cruiser" 10M, originally conceived as a simple beam & hull boat but with "wide body" hulls to enhance livability. I've seen another with a center cockpit arrangement also. They /this one carries a lot of aft trim & as the underwing follows the hull deck join this limits the clearance aft, also the nacell for diesel & "Sonic" drive drags about 4-5 inches I think & also has keels, performance was good as a motor sailer/off the wind. Some where I've got an old Beach Marine brochure that displays about 20? different models but really variants on about 5 different vessels with options, Bob used to claim about 30 plus options I think. I reckon that with boards & the Keels off & twin outboards to neatly installed nacelles/champher or to wells the standard model might be prettty good. All the best from Jeff.
     
  7. tonysuncat
    Joined: Jul 2012
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    Location: townsville

    tonysuncat Junior Member

    centre board casing

    Thanks Phil
    Had a feeling the nacelle wuold not be strong enough ,but was hoping I could strengthen the inside so as to not go up on the hardstand and I hate to cut holes in my hull.
    I am just waiting for the plans to be retured from the surveyor
    They want a realise from Crowther to return my plans
     
  8. oldsailor7
    Joined: May 2008
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    oldsailor7 Senior Member

    "They want a realise from Crowther to return my plans"

    Good luck.
     
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  9. catsketcher
    Joined: Mar 2006
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    catsketcher Senior Member

    Plans?

    This may sound like sacrilege but I wouldn't worry too much about the plans. IIRC correctly Lock was not that involved in the Sports Cruiser. IIRC Bob Hotchkiss got the C10 moulds and made them wider to make the sports cruiser. You won't need plans to make the boat much better. We have come a long way sonce she was designed.

    Don't be worried about cutting holes in the hull. Considering the keels are going to come off it you have to slip the boat anyway. Make the case and board beforehand. Then you cut the slots top and bottom and then glue the case in with generous coves. The case then gets so much glass put into it that it can't leak - it will be the strongest part of the boat. Its really easy as your boat is solid glass below waterline - usually we have to work around the core.

    You may want to leave just small stub keels on the hulls. I have 100mm deep keels on Kankama and they are great for jacking or resting the boat on when on the hard. It would be easier to leave stubs on your hulls rather than somehow grinding the whole thing off.

    But don't worry about a case in the hull - it really is not that hard at all. The trickiest bit is making a nice board and that is not hard either. I would use epoxy to get a good secondary bond but I don't ever use polyester as I have wooden composite boats.

    Ask around a Bob Oram boat like a Mango and base your build on that board.

    cheers

    Phil
     
  10. Silver Raven
    Joined: Oct 2011
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    Location: Far North Queensland, Australia

    Silver Raven Senior Member

    Gooday there 'tony' - - Do you want my lawyer or 'hit-man' & NO I'm not kidding. The 'saying' is a 'metaphore & at law - nothing else ! ! ! ! Demand the plans be returned - IMMEDIATELY & FURTHERMORE - FORTHWITH. If they are close enough - then walk in - put a $40.00 [Dick Smith] tape-recorder on the counter & ask for you plans back - do not leave without them - if necessary call the Police & charge them with theft of your property. OH - do remember to take your mobile phone & take a few pics - especially of the faces of the people that argue with you & also so you can call the Poilce. Then the Police will have to get them to surrender the plans back to you - immediately. Take the returned plans to the best 'plan-printer' in Townsville & see if they can find-out - if they have been copied - then lodge a case - costs about $50 bucks to lodge a case in the 'small claims' court to recover your - out-of-pocket expences of - say $4,987.53 - anything under $5000.00 - will get the case into the 'small debts' court - & there they can't bring any legal council of any kind - it is against Australian lay - been there done that worked on the water-front in OZ for 40 years & never lost a case.

    If you wish PM me or send an e-mail to jamesaviculture@hotmail.com - then I phone you when it's convenient to you - I'm just up in Cairns. & only semi-retired yacht builder/repairer. Oh - chaps - save the cautions about the above words - my lawyer is reading all this over my shoulder. Ciao bloke & good luck, james

    PS - the other comments - about changing the 'keels' - c/b's - etc etc. Yes - C-S is right - just go ahead & do it. I personally would not be asking anyone here in OZ to design a set of c/b's or rudders - I'd try Martyn Fischer to draw some up - but that'd be after we finish our somewhat 'heated - long-winded' discussion about - - size, shape - foil section both top & bottom - etc, etc, however you'll do - - "what a man's gotta do" & that's the way it should be. jj
     
  11. waikikin
    Joined: Jan 2006
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    waikikin Senior Member

    Beach Marine

    Here's some from the past...........
     

    Attached Files:

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  12. gypsy28
    Joined: Mar 2010
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    Location: NSW Australia

    gypsy28 Senior Member

    Ahhh Middle Percy, what a beautiful spot, but then again who wants to be out cruising when you can be working a day job instead :rolleyes: I'll get back there one day soon...

    DAVE
     
  13. tonysuncat
    Joined: Jul 2012
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    tonysuncat Junior Member

    progress on working over my cat

    Sorry about the slow responce but everything goes slowly in Nth Queensland to my fraustration.No luck still getting my plans off GA Glanville in Cairns
    So far I have removed my Nanni 37 hp from the nacelle and will try to get my Sd40 to rotate 90 degrees by getting a collar machined up around the two bell housings like the system on John Gross Fastback to remove drag
    I fitted a Perry hardtop 6mtr by 5.5 mtrs built to survey in H60 foam and have found a 12.2 mtr by 3.8 wing mast off an 8 mtr tri with Gary Martin Spectra sail.Problem is I need to put in a compression post from beam with dophin striker to the hardtop/awning which is 2 mtrs high.
    I try to get my modifications premade so I can work from Magnetic Island as I cant spare the time to go on the hardstand as i work everyday for myself renting Scooters to backpackers
    Tony Grainger wrote an article years ago comparing dagger boards to mini keels so maybe I can buy the latest technology in mini keels and remove mine and glass some premade ones on.
    I will try to attach some photos
    Many Thanks Tony View attachment 4 pictures on dock.zip
     

    Attached Files:

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  14. catsketcher
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    catsketcher Senior Member

    Gday Tony

    Can't see the Perry hard top in the photos - Is it on the stainless struts?

    As for the keels - it sounds awfully hard. You want the thinnest NACA 00 foil you can. A 0005 would about 150mm wide at it widest. The problem is getting a premade keel to fit your hulls. Your keel line and hull round will make this almost impossible to premake. I reckon I could fit a premade daggercase in three days flat out. Two keels would take about 4 times as long with the huge amount of gluing and fairing required. Grainding down your old keels would take days too. Cutting them off at about 100mm off the bottom would take much less time.

    As for the mast - DON"T! The tri would have a righting moment less than one third of your cat. Mast designers design masts to righting moment so this mast will fall down and the spectra main will delaminate and fail before you even get close to reefing. Get a nice main sewn up and that should help a lot without a new rig.

    cheers

    Phil
     

  15. tonysuncat
    Joined: Jul 2012
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    Location: townsville

    tonysuncat Junior Member

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