Sub Carbon Surfer Masts on Cat or Dinghy?

Discussion in 'Sailboats' started by BobBill, Feb 28, 2014.

  1. BobBill
    Joined: Oct 2009
    Posts: 718
    Likes: 12, Points: 18, Legacy Rep: 157
    Location: Minnesotan wakes up daily, in SE MN, a good start,

    BobBill Senior Member

    Substituting/Converting Carbon Surfer Masts on Cat or Dinghy?

    Not sure where to post.

    I am about to combine a couple surfer carbon masts into a spar for my boat and wondered if anyone had done it and had some advice?

    I did it for a Kite dinghy and it worked fine, but all I did was sleeve it with carbon sock to stiffen and add one stock spacer at base so it fit the metal base...

    This will be a bit different as the spar needed must be 26 feet long, and it seems I will have to join two or three masts to make one flexy yard or spar.
     
  2. Baltic Bandit

    Baltic Bandit Previous Member

    Windsurfer masts are designed to be preloaded in tension and to not have a lot of lateral loading on them. So don't be too surprised if they don't show much durability and/or a lot of lateral flexing tha screws with your sailshape
     
  3. BobBill
    Joined: Oct 2009
    Posts: 718
    Likes: 12, Points: 18, Legacy Rep: 157
    Location: Minnesotan wakes up daily, in SE MN, a good start,

    BobBill Senior Member

    I kinds figured that would happen. Thanks Bandit. The Malibu Outrigger yard was or is designed to flex in gust to take the load off. Too, I will be putting a sleeve over the entire spar to stiffen a bit...maybe two, if I get too much deflection. Looking for two inches.

    Sound ok?
     
  4. messabout
    Joined: Jan 2006
    Posts: 2,985
    Likes: 191, Points: 63, Legacy Rep: 1279
    Location: Lakeland Fl USA

    messabout Senior Member

    At 26 feet long the windsurfer masts will be very willowy. No way you will hold a decent sail shape with a wet noodle like mast.

    Adding carbon might help a little but not nearly enough for a mast of that length. Stiffness is massively influenced by diameter and much less so by the strength (modulous of elasticity) of the wall fibers. The general idea is that stiffness is a function of the cube of the diameter whereas elastic modulous is only a linear function.

    It is clear that you want a lightweight mast. Think, maybe, of a wooden birdsmouth type that can be made in a suitable diameter and will still remain reasonably light. These are almost,..... but not quite, fun to make. They can be tapered and the work will keep you safely away from bar rooms while you do the necessary planeing and finishing.
     
  5. gggGuest
    Joined: Feb 2005
    Posts: 808
    Likes: 17, Points: 18, Legacy Rep: 76
    Location: UK

    gggGuest ...

    That will only weigh about double what a carbon one would...

    Are you talking about a free standing mast or a stayed one?

    For a free standing mast then I submit, forget it. It had better be built for the job. You just aren't going to get a realistic taper.

    For a stayed mast, hmm, well, you may be able to get away with part of a board mast as a top mast, but you probably ought to have a parallel tube below the hounds. You might find that's reasonably cost effective if you can find a source of appropriate tube.
    Sleeving with ordinary woven carbon sock won't do a lot because its fibre orientation is all wrong. Most of the fibre in a carbon mast is unidirectional and lengthways, and that does all the real work. There are just hoop or 45/45 fibres as an outer and inner skin to keep the unis pointing in the right direction.
    You could use various pieces of board mast principally as a inner skin, and vac bag on carbon unis and then your 45/45 outer skin, but any saving in time or money over just building a complete new mast from scratch starts being rather small and not worth possibly compromising a whole heap of useful materials...
    Trouble is, I think that masts are kinda critical on bend. Too stiff is as bad as too soft. So there's a real risk of spending a lot of time and materials and getting something that isn't clever if you try a frankenstein job on something that big.
     
  6. Baltic Bandit

    Baltic Bandit Previous Member

    Since when is wood not composed of carbon fibers :)

    Ok I'll get my hat
     
  7. BobBill
    Joined: Oct 2009
    Posts: 718
    Likes: 12, Points: 18, Legacy Rep: 157
    Location: Minnesotan wakes up daily, in SE MN, a good start,

    BobBill Senior Member

    First, much thanks. I am new at all this and maybe forging a path.

    A couple things I should have added: the 26 foot "mast" for this rig is really a yard, supported by a stubby mast, that will, hopefully act as original Sitka spar on the Malibu Outrigger.

    Also, I got the idea from when I constructed a similar rig for my Kite dinghy to sub for the original Sitka mast (like old Finn) to use more modern sail and materials and keep the orig more or less preserved.

    It is a 20 foot mast made from Force 5 aluminum base 10'x2.5"x.125 wall thickness, plus one 2-section 100% carbon spar that had damaged base (removed) and was sleeved with 9 oz carbon sock. See schematic pic below.

    Yard is intended to flex and depower rig in gusts and the sail is more of a semi crab-claw (of which I know squat) and all of this is a common sense approach to this version of the original Malibu Plans...that mast, incidentally, is a noodle also...

    With the Kite rig, I punted and was lucky; its mast was but 5 lbs lighter and nearly duplicated the original Sitka mast under sail and on blocks (deflection after the fact). The carbon mast and AL Force 5 boom work just fine in 15 knot breeze...and might even be considered a bit too stiff in lighter pressure. Still, very satisfactory, at least to this swab who knows very little about such things.

    So, I extrapolated, and acquired three used carbon spars...one for long yard, a second another for boom, and a 3rd intended later for bow-sprit for small jib sail. Not original Malibu Outrigger, but thinking more or less improved version...

    I understand the idea the wood version, and have the original plans that call for a Sitka yard, but I concluded that using Sitka was impractical, considering the many carbon surfer sails around that might be recycled and/or using aluminum 6061-T6 tubing to construct similar rig...

    Obviously, the carbon seems best choice and makes for wonderful and not severely expensive experiment.

    If I employ an aluminum base with the surfer mast to form the yard, with sleeve, an considering the semi-crab claw intent this may be decent alternative.

    I mean, it worked with Kite...and I did consider added weight of the hulls (300 # all up target) and the rig.

    I know you gents have lots of experience and why I wanted to touch hands to see what you thought.

    The below are original Malibu Outrigger schematics to help visualize the rig...
     

    Attached Files:

  8. BobBill
    Joined: Oct 2009
    Posts: 718
    Likes: 12, Points: 18, Legacy Rep: 157
    Location: Minnesotan wakes up daily, in SE MN, a good start,

    BobBill Senior Member

    I must add that it amazed me how much stiffer the carbon made the surfer mast I made for the Kite...if I can locate, pic of Kite mast included.
     

    Attached Files:

  9. garydierking
    Joined: Sep 2004
    Posts: 136
    Likes: 17, Points: 18, Legacy Rep: 174
    Location: New Zealand

    garydierking Senior Member

    I used two windsurf masts butt to butt for the 28 ft luff spar on my proa. The upper half was carbon and the lower one was fiberglass. I found it to be plenty stiff with a 250 sq ft sail. They were joined at the middle with a windsurf base extension (hardened aluminium tube), but no glass wrapping at the joint. The two masts were held together by the sail itself.

    [​IMG]
     
  10. BobBill
    Joined: Oct 2009
    Posts: 718
    Likes: 12, Points: 18, Legacy Rep: 157
    Location: Minnesotan wakes up daily, in SE MN, a good start,

    BobBill Senior Member

    Gary, Much appreciated. I had thought of doing exactly so - end to end and am comparing to a combo with 6061-T6 tube in low end of the yard, say the bottom 2 sects (one 4', one 8").

    Fun, this project.
     
  11. BobBill
    Joined: Oct 2009
    Posts: 718
    Likes: 12, Points: 18, Legacy Rep: 157
    Location: Minnesotan wakes up daily, in SE MN, a good start,

    BobBill Senior Member

    Gary, I have two questions:

    Did you sleeve the sections or join two different spar sections somehow?

    What do you think of using hook-and-loop (Velcro) to attach sail to yard? (I had thought to use with grommets, in case.)

    Thanks.
     
  12. garydierking
    Joined: Sep 2004
    Posts: 136
    Likes: 17, Points: 18, Legacy Rep: 174
    Location: New Zealand

    garydierking Senior Member

    They weren't actually joined. They just had a 2 ft aluminum tube inside the joint so they could be taken apart. If you look at the massive forces applied to the base of modern windsurf masts, you'll realize that this application has much less strain.
    I've never tried Velcro for that. I either lace it through grommets or sew a sock on the luff of the sail.

    Gary
     
  13. BobBill
    Joined: Oct 2009
    Posts: 718
    Likes: 12, Points: 18, Legacy Rep: 157
    Location: Minnesotan wakes up daily, in SE MN, a good start,

    BobBill Senior Member

    Thanks Gary,

    So the surfer spars were used "as found," one glass and one carbon...not sleeved...makes sense...I will give that a consideration, never occurred to me to go butt-to-butt, so to speak.

    I got the idea for the hook and loop stuff from this site... http://www.chuckpaine.com/boats/paine-14-trailerable-sailboat/ while looking for parrel beads...

    Figure if its good enough for Mr. Paine... but I also figured to anchor the strips to the mainsail with 3/8ths grommets just in case and lace if fails.

    Weather is slowly warming, so won't be long...thanks again.
     
  14. Petros
    Joined: Oct 2007
    Posts: 2,936
    Likes: 139, Points: 63, Legacy Rep: 1593
    Location: Arlington, WA-USA

    Petros Senior Member

    cleaver design, I would second the opinion that using the sailboard mast on the upper half would be sucsessful. putting them but end to butt end might work but strikes me as unlikely, there is a lot of stress on the spar at the bottom end and it will at best make it difficult to maintain the desired sail shape, as worst make it difficult to control and possibly fail. If you can use a standard tube section for the lower half that I would suspect give you better control over the sail shape.

    I personally do not care for Velcro hook and loop fasteners on critical connections; it does wear out and not hold very well eventually, they tend to ice up and not work at all in cold weather, not easy to make field repairs. It might work well for you and not give you any issues, but I would rather use a plain sewn sleeve if the design of the rig allows it, simple and no moving parts, and has lots of redundancy. A lace-on sail is not as convenient, but is simple, durable and easy to field repair if necessary.
     

  15. BobBill
    Joined: Oct 2009
    Posts: 718
    Likes: 12, Points: 18, Legacy Rep: 157
    Location: Minnesotan wakes up daily, in SE MN, a good start,

    BobBill Senior Member

    Petros, I was not so convinced re Velcro either, but seems to be commercially viable, so will try and am anchoring with grommets for lacing just in case. I am doing to not have to deal with holes in carbon spars, adding luff grooves, etc and still want to douse sail fast if need be...and set up rig easy too.

    The butt-to-butt makes sense using the sail shown by Gary above (the really nifty Gibbon style) as it tilts when shunted...in my case, if I ever get the sizes right, I plan to go with AL T6 from gooseneck to the carbon tip set...or roughly 12 feet, in either one tube or two of differing OD/wall sizes to support etc. Yes, your take on gooseneck stresses is correct, and Gary's "gooseneck" is where the spars meet in the center, I would say. My rig sets more like conventional sail...

    Looks to be standard tube as you suggest...likely 2.25OD with .125wall and wood inserts at joint, unless I decide to nest with AL piece with glass covering to fit...am trying to stay away from one long 25-26 foot spar to mess with on the hard.

    Again, Thanks for help...geniuses think alike in different places together. :}
     
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.