Composite tube

Discussion in 'Fiberglass and Composite Boat Building' started by YoungGrumpy, Apr 25, 2014.

  1. YoungGrumpy
    Joined: May 2012
    Posts: 60
    Likes: 4, Points: 8, Legacy Rep: 34
    Location: New Jersey

    YoungGrumpy Junior Member

    Last year I did it wrong!
    I want to replace the tiller bar on my Cat. (Seawind 24). What I've got from PO is an aluminum pipe (about 1.5"), cut roughly to the size, plain ugly.
    I've tried to make a new one, cedar core, bi-axial tape at about 45 angle, epoxy. The resulting pole is light ok, but not stiff enough. It is bending under its own weight, which is obviously, not good for intended use.
    Any advice is greatly appreciated.
     
  2. PAR
    Joined: Nov 2003
    Posts: 19,133
    Likes: 476, Points: 93, Legacy Rep: 3967
    Location: Eustis, FL

    PAR Yacht Designer/Builder

    Hardwoods are typical for a tiller. I use oak and mahogany, though there are several common combinations. Laminate orientation can also stiffen up the tiller bar, so consider a horizontal laminate if working with less dense species. Aluminum is fairly flexible, which isn't what you want, but if sized properly, can get the job do with minimum wight. To improve stiffness, increase diameter and wall thickness if hollow.
     
  3. YoungGrumpy
    Joined: May 2012
    Posts: 60
    Likes: 4, Points: 8, Legacy Rep: 34
    Location: New Jersey

    YoungGrumpy Junior Member

    We are talking about the connecting tube 16 ft, between two tillers of a catamaran, right? Mahogany-Oak laminate would be nice, but, out of place on this boat and too heavy (the strength required is, literally, not to bend under its own weight plus two tiller extension sticks) I am afraid?
    I want it reasonably light, and functional, no need for a yachty looks.
     
  4. waikikin
    Joined: Jan 2006
    Posts: 2,338
    Likes: 115, Points: 73, Legacy Rep: 871
    Location: Australia

    waikikin Senior Member

    YG,
    I'd go back to the alloy & if you want it neater make some rebated end plugs from wood & snaz them with a bit of varnish. I dont think there's much need for tiller extensions on a SW24, maybe you can make bar overlength past the pivots.

    Jeff.
     
  5. upchurchmr
    Joined: Feb 2011
    Posts: 3,053
    Likes: 150, Points: 63, Legacy Rep: 579
    Location: Ft. Worth, Tx, USA

    upchurchmr Senior Member

    http://dragonplate.com/default.asp?gclid=CNHglq6X_70CFaNj7AodagkAdQ

    These guys have lots of tube.

    What size was your cedar core, did you use glass? Bending stiffness increases dramatically with the diameter of your tube. Or, you could add unidirectional carbon top and bottom to get the best stiffness with what you have.

    You can make a hollow cedar pole using a birdsmouth technique (make it bigger diameter) and wrap with glass or carbon.
    What you want is the uncut fibers running from end to end not at a 45 degree angle to the pole. I'm not quite sure what you ended up with from the description. 45 degrees would work well on a driveshaft or something that has twist in it.

    You could also use steel tube - probably stainless. Steel has 3x the stiffness of aluminum. Might be expensive.
     
  6. Ilan Voyager
    Joined: May 2004
    Posts: 1,242
    Likes: 159, Points: 63, Legacy Rep: 758
    Location: Cancun Mexico

    Ilan Voyager Senior Member

    Why to spend hours of work when a simple anodized aluminum 6061T5 or T6 tube will do the job? As Par said increase the diameter, it's just a problem of mechanical inertia. Alu tubes are rather cheap, are easily found until 20 feet long, easy to glue, screw, rivet, are fairly resistant to corrosion, and impervious to UV so no need of paint...
     
  7. rwatson
    Joined: Aug 2007
    Posts: 5,852
    Likes: 290, Points: 83, Legacy Rep: 1749
    Location: Tasmania,Australia

    rwatson Senior Member

    Nowhere do you say that the original aluminium bar is not doing the job, just thats its ugly.

    If its working OK, just polish it up, and add neater connections as previously suggested
     
  8. YoungGrumpy
    Joined: May 2012
    Posts: 60
    Likes: 4, Points: 8, Legacy Rep: 34
    Location: New Jersey

    YoungGrumpy Junior Member

    All sound advise,
    "Nowhere do you say that the original aluminium bar is not doing the job, just thats its ugly."
    I think I will concentrate on improving the original setup.
    Thanks
     

  9. PAR
    Joined: Nov 2003
    Posts: 19,133
    Likes: 476, Points: 93, Legacy Rep: 3967
    Location: Eustis, FL

    PAR Yacht Designer/Builder

    There's a huge difference between aluminum pipe and aluminum tubing. Of course, the aesthetic thing is up to you, maybe a faux carbon fiber paint job, but you'll want tubing, for it's strength and stiffness per pound, compared to pipe.
     
Loading...
Similar Threads
  1. Maciej
    Replies:
    10
    Views:
    2,027
  2. nieuwhout83
    Replies:
    10
    Views:
    3,374
  3. Scott M..
    Replies:
    58
    Views:
    708
  4. Smokeyr67
    Replies:
    16
    Views:
    496
  5. Michael Hyder
    Replies:
    5
    Views:
    349
  6. Chotu
    Replies:
    3
    Views:
    306
  7. denmic
    Replies:
    6
    Views:
    419
  8. Mattskii89
    Replies:
    23
    Views:
    1,402
  9. fallguy
    Replies:
    17
    Views:
    1,025
  10. Steve W
    Replies:
    17
    Views:
    1,268
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.