VX-40's homemade!

Discussion in 'Multihulls' started by GuestR01312011, Nov 11, 2007.

  1. I love the Volvo Extreme 40's, the speed of them, I just think they're way expensive!
    If you could build one out of GFRP instead of Carbon and an Al rig etc they'de be much cheaper, and Cat's are 'easy' to build no?
    Im going to try!
     
  2. marshmat
    Joined: Apr 2005
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    marshmat Senior Member

    Interesting idea... they're certainly an exciting class.
    Building one out of fibreglass or wood/epoxy strip-plank could probably be done, and an aluminum rig designed for it. The result would be heavier and slightly less efficient than the expensive carbon ones, and so a bit slower, but likely also harder to push to the point where it goes airborne and flips over (as the VX40s tend to do on a disturbingly regular basis).
    Where would you be getting a design for such a craft?
     
  3. DGreenwood
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    DGreenwood Senior Member

  4. Im thinking of building one female mould and vacume bagging GFRP and a foam sandwich for each hull, will have to do a fair bit of research and calc.s regarding cross beaming etc...
     
  5. DGreenwood
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    DGreenwood Senior Member

    At that point the cost of higher tech materials represents a pretty small proportion of the costs..why not go with the good stuff?
     
  6. rapscallion
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    rapscallion Senior Member

    I bet a composite cylinder molded mast would be cheaper and lighter than your alum mast. Look into the cat2fold. seems like a really nice boat for the cash. It would be much cheaper and easier to campaign; which may be a consideration if you are looking to cut costs from T zero.
     
  7. Carbon is ridiculously expensive! Plus worldwide shortage
     
  8. rob denney
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    rob denney Senior Member

    G'day,

    Not quite true. I have just sold a tonne of carbon for $AUS45/kg. Glass is currently about 12. Of course, the carbon was in tow form, which requires some innovative thinking to use it, but for masts, beams and rudders it is far cheaper on a stiffness/weight basis than anything else. And the shortage is almost over, although new uses are being dreamt up all the time, so it will be a while before there is a glut.

    As for building a low tech Formula 40, this is a pretty easy thing to do. However, it will not perform anywhere near as well. You will still get plenty of thrills, but will regularly find out why high tech and detailed design are required for high speeds as things will always be breaking.

    If high speed sailing is your goal, then the most bang for your buck comes from a proa. Least material. least drag, fewest appendages, simplest rig means a fast, cheap boat that won't be always breaking. Have a look at http://www.harryproa.com/SoloTranspac/Solitarry1.htm for a short handed ocean racing version. A low tech 50' day sailor (F40 style) would weigh about half a ton. A video of a 3 tonne cruising version, with the same sail area is at http://www.youtube.com/watch?v=8chR6DAFjGA.

    regards,

    rob
     
  9. rapscallion
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    rapscallion Senior Member

    It would be interesting to see the bruce numbers to a low tech 40' cat to the racing proa.

    Number wise proas are the best way to go, and the telescoping mast is a really cool idea. I can't wait to check that out.

    The Kss method also is attractive. I'm going to have to build my boat in the back yard. It would be nice If I could build the pieces first in the basement over the winter and assemble it in the summer.
     

  10. rob denney
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    rob denney Senior Member

    G'day,

    Bruce number of the original Formula 40 was 1.97 (weight 1800 kgs/3960 lbs, sail area 90 sq m/967 sq'.

    Given that it took a long time before these boats were consistently down to weight, I think a low tech version would weigh at least 2,200 kgs/4840 lbs with the same sail area. Bruce number 1.84

    The low tech (foam or wood/glass hulls, carbon tow vac bagged beams and mast, laminate sails) solo proa with a day sailing ww hull would weigh about 500 kg/1100 lb and have 50 sqm/537 sq' of sail. Bruce number 2.25

    A high tech proa (nomex core, carbon skins, autoclaved spars, carbon sails, inflatable battens) might weigh as little as 350 kgs/770 lbs. Bruce number 2.5.

    The proa would have much less windage, less water drag (1 foil instead of 4), a much more forgiving and easily handled rig and the low tech one would cost about an arm and a leg less than the cat.

    regards,

    Rob
     
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