Free standing masts. Some thoughts on the state of the art.

  • 09 Jan 2021 23:04
    Reply # 9793371 on 9442600

    Hi, I own a home built nine meter coastal cruising catamaran.  Years ago, after I launched Cobwebs, I built a wing mast using a central cedar core, 4mm ply for the sides and foam for the front curve.  I was going to 'glass it with 200 gram cloth and a 50mm carbon tow either side as per the designer, however I ended up using 350mm wide carbon cloth which 'glassed the whole mast.  I didn't vacuum bag it (I didn't know how) and just used a few layers of epoxy.  All up the 9.8 metre mast, complete with home made stainless fittings weighed about 80 kg. After 15 years it's now time to replace the standing rigging and I am seriously leaning toward an aero-rig.  The cost of replacing the rigging is about $2000 Australian.  I think I can build the aero-rig for about the same price.  Because 'Cobs is a full bridgedeck cat I have approx. 1.5 meters of 'bury' where the mast sits.  Using that I am thinking of extending the mast with 150mm diameter aluminium and set this extrusion in a 200mm tube with nylon bearings to enable the mast to rotate.  I can use my fully battened mainsail and the roller furler set up with a jib to fit to the mast and boom. This exercise is very much low tech (read cheap because I will use available bits) and I intend to contacted Rob Denny regarding this idea ( the designer passed away some years back so that option is no longer available).  Any ideas from the forum members will be most appreciated, regards Ross C.

  • 02 Jan 2021 20:51
    Reply # 9599212 on 9593017
    Anonymous wrote:

    Howard, 

    of course I assume vacuum bagging, much easier as each piece is smaller, perhaps you could use a polythene tube.

    yes a long mould, but narrow and not heavy.

    perhaps pulltruded glass is strong enough, and more readily available at a reasonable cost.

    i have seen a photo of pultruded carbon strip in a roll, used on the proa project that predates the Jzzerro two oceans attempt.  I guess expensive, hence using tow, which can be made into a taper.

    ....all dreams, much easier to get a stock aluminium tube and stick a bit of wood in the end.


    Mark:

         
    Talk is cheap as they say.... and dreams are free.    Carbon tow is I believe the most economical form, which is why people like Rob Denny use it extensively.    JRA members are hardly breaking down the doors to get carbon fiber masts because they involve lots of cost or unfamiliar and possibly expensive construction, and the weight savings are simply not important to the  majority of members who sail monohulls. 

        My interest is in  multihulls for a  number of good reasons based on the kind of sailing I I would like to do "eventually", which is long term voyaging to distant parts of the world.  It's time to go to the places I've read and dreamed of.  Most of my sailing has been solo... It's my nature to do things mostly solo.  That makes about a 30' catamaran the optimal choice for me. It means having a bridge deck cabin or pod (non-standing) where I can take shelter out of the weather when necessary, an still have a good watch keeping position.  A safe dry place to nap where I can have full view virtually instantly from my usual reclined sleeping position, and be only a step or two away from the cockpit with no ladder to climb.  It means far less fatigue because I won't be spending days or weeks living "on my ear".  Less potential of an MOB situation, being able to cook good hot meals easily and less potential of injury or scalding, etc.  

           Multihullers operate under a different set of rules than monohullers.  You can't simply pile whatever weight you want aboard.  They are inherently lower displacement, and usually less displacement per inch of submersion, and as you lose freeboard, you also lose bridge deck clearance.   Bridge deck clearance is critical to both comfort and safety, as well as structural integrity.  

            It is necessary to have a backpacker's mentality on a small multihull sailboat.    As a backpacker myself for over 50 years, I still think in terms of sawing the handle off toothbrushes.... as an extreme, and leaving everything behind that I can.  If you are living aboard / voyaging on a small multihull, the problems are exaggerated.   It is important to keep the boat as small as reasonably possible to keep costs and upkeep down, and to have a manageable boat....... I'm not interested in a proverbial "white elephant".   That means eliminating weight wherever possible... while trying to keep costs down.  The more money I throw at the boat, the less I have for voyaging, but being penny wise and pound foolish will bite one in the ass.  Looking at the feasibility of carbon fiber masts for weight reduction makes sense ONLY if it is cost effective, and that means being able to build my own from economical materials, or perhaps finding salvage Freedom mast(s), etc.  Hybrid might also be an option, as well as building only the lower mast portion and buying a carbon fiber windsurfer mast for the top portion, etc.   Hybrid might mean carbon combined with wood or aluminum, etc.     The weight savings  may well not justify the cost of carbon, and the better option might be to focus on weight reduction in things like battens and sailcloth.  Of course it also means stripping out all the "junk".  Excessive galley stuff, head converted to composting, using a home built watermaker and greatly reducing tankage (non negotiable IMHO), with the water situation in some parts of the world.   It means looking at what kind of propulsion, and how much fuel tankage.  It means looking at energy storage & generation.... LIPO and solar, and using energy as it is produced where possible, such as cooking and making ice and water while  the sun shines.   It means doing dehydration of foods, and avoiding buying foods in heavy cans and jars where possible.    It means making compromises on things like the dinghy to keep weight down, and making difficult choices on ground tackle.... You have to have chain, but how much?   Losing a boat from making a poor compromise here is not an option.   It means making difficult choices on what spares, cordage, tools, etc.... What can serve multiple functions, what is redundant, what can I not live without?

         Here are some numbers from the boat that best fits my criteria.... except payload. 9.14M LOA.   5.95M Beam, .5M draft, 46.5 sq M sail area, Displacement empty:  1800KG, Displacment WL:  2700KG    Payload 900 KG or about one US ton.     Out of 900 KG comes the crew, and everything to support the crew, food, water, clothing, safety gear, Head, galley equipment, cooking fuel, dinghy, electronics, water plumbing and pumping systems, lighting, heating cleaning and laundry, etc.   Also out of it comes motor fuel, ground tackle, tools and spares, batteries and wiring, switches and breakers, self steering systems, drogue(s) and sea anchors, and associated cordage, and on and on.  

         This being an epoxy ply design or strip plank hulls, owner built design, owner "enhancements" and "improvements" are all weight.  That water heater and shower, clothes washer, and electric pumping system all get left ashore.  Identifying the unnecessary "toothbrush handles", and pitching them overboard are top priority as far as I'm concerned.    Assessing weather a single mast stepped on the bridge deck makes sense, or weather a pair of keel stepped masts is a better option will be interesting.  a single mast looks possible, but location would be further than desirable aft.  Do you correct for that with a head sail?  Or by underwater mods?    This design is built either with daggers or LAR keels.... Use a split junk rig, to minimize the issue, look at rudder balance and trim tab, add to the aft end of the LAR keel and remove from the forward end?  Add a  small fixed keel aft of the dagger if it had daggers?   LAR keels inherently add displacement.... eliminate the daggers and install LARs?  

         As you can see I've looked at many things.... Including larger boats, and monohulls, and I keep coming back to the same place.  The best option... If I was willing to go there would be to build to order.  The same boat could be built with slightly longer and significantly larger displacement hulls (per the designer).  Performance is where most designers focus, and that is low on my list of priorities.   I'm following my own "drummer".


                                                  H.W.

     

    Last modified: 05 Jan 2021 15:53 | Anonymous member
  • 02 Jan 2021 16:37
    Reply # 9593017 on 9442600

    Howard, 

    of course I assume vacuum bagging, much easier as each piece is smaller, perhaps you could use a polythene tube.

    yes a long mould, but narrow and not heavy.

    perhaps pulltruded glass is strong enough, and more readily available at a reasonable cost.

    i have seen a photo of pultruded carbon strip in a roll, used on the proa project that predates the Jzzerro two oceans attempt.  I guess expensive, hence using tow, which can be made into a taper.

    ....all dreams, much easier to get a stock aluminium tube and stick a bit of wood in the end.

  • 31 Dec 2020 16:40
    Reply # 9540119 on 9538872
    Anonymous wrote:

    Howard,

    yes a well made DIY carbon mast is desirable, I certainly would like one....when I finally get my dream catamaran.  I have not costed one, but assume the price of carbon is a lot less than it was.  

    With your method, why melt the foam discs.  They give some support against deformation.  The melted material would still be within the mast.

    I have  seen two such masts, both in Norway. Ketil Greve has one, he had it designed and made for him.  I recall the surface finish was a bit lacking in polish, so assume it was semi professional.  I think it cost him about €5000 say 10 years ago.  We had a good day sail, it was very stiff, in fact his designer said it could have been lighter, but Ketil preferred it stiff.  Jonny Jorgensen made his own for a large two masted yacht he had built, it was in sail away stage but far from complete, we did go for a short sail. He built his masts from staves with a foam core, I think he used mainly glass tow, not carbon.

    My thoughts are to make a carbon stave mast.  A mould would be made, say from PVC gutter, and say 12 or 16 staves made. Assembled with discs at intervals and glassed over.  The advantage being that each stave is much easier to make, and should there be an error it would be less costly.  



    Mark:

          The barrel stave method is one I've thought a lot about myself... just like a hollow wood mast.    They would need to be vacuum bagged IMHO to remove surplus resin, and making a 30-45 foot mold (likely range) that was true might be a challenge.  The staves would need to be tapered both in thickness and width, and once assembled a filler of epoxy cabosil or something of the sort would need to be applied so there was something to round off rather than grinding away carbon fiber I would think, then helical wraps of carbon fiber followed by glass.

         A permanent high density foam core might have some use structurally, but a hollow mast is useful.   The foam I was talking about; XPS, is low density and when dissolved with solvent will wash out entirely.  It is the same material as the EPS used in foam cups, but manufactured far differently and it's far stronger....  It will however dissolve much the same way.  Try pouring some gasoline into a foam cup ;-)   I made a hot toddy one day when I had a bad cold, and on a whim added some eucalyptus oil, and poured the works down my leg right through the bottom of a foam cup as if it wasn't there.   You've never seen a pair of pants come off that fast!!   I ended up with a bad cold AND second degree burns on my leg to distract me from my cold ;-)

            Another option might be to use pultruded rod, adding unidirectional carbon in the gaps left by the taper, and by the round rods themselves, and topping it with wraps of glass to protect it.  I have some left over pultruded 1" fiberglass I bought for aircraft landing gear.  I've used it in a number of projects and it is easy to work with and very rigid.  I believe you can get pultruded carbon fiber, but I suspect it is not cheap.  Again laying it up on a foam mandrel on a cable stretched between two hard points...(tree trunks?) would probably be useful for assembly.   I suspect that the logistics of getting carbon fiber pultrusions in the desired length would make this impractical if not impossible, and then there would be the waste or inefficiency of construction.


                                    H.W.

  • 31 Dec 2020 15:40
    Reply # 9538872 on 9442600

    Howard,

    yes a well made DIY carbon mast is desirable, I certainly would like one....when I finally get my dream catamaran.  I have not costed one, but assume the price of carbon is a lot less than it was.  

    With your method, why melt the foam discs.  They give some support against deformation.  The melted material would still be within the mast.

    I have  seen two such masts, both in Norway. Ketil Greve has one, he had it designed and made for him.  I recall the surface finish was a bit lacking in polish, so assume it was semi professional.  I think it cost him about €5000 say 10 years ago.  We had a good day sail, it was very stiff, in fact his designer said it could have been lighter, but Ketil preferred it stiff.  Jonny Jorgensen made his own for a large two masted yacht he had built, it was in sail away stage but far from complete, we did go for a short sail. He built his masts from staves with a foam core, I think he used mainly glass tow, not carbon.

    My thoughts are to make a carbon stave mast.  A mould would be made, say from PVC gutter, and say 12 or 16 staves made. Assembled with discs at intervals and glassed over.  The advantage being that each stave is much easier to make, and should there be an error it would be less costly.  


  • 30 Dec 2020 08:44
    Reply # 9506715 on 9489914
    Anonymous wrote:

    The conventional wisdom which includes the "facts" that the Bermuda rig is superior, and that a stayed mast is superior, and other questionable bits of "wisdom", is that building carbon fiber masts is something only professionals should attempt, and that the arrangement of the fiber in the mast is critical and highly individual to the individual application, and far too complex for ordinary mortals to work out... among numerous other questionable bit of "wisdom" mixed liberally in with good sound wisdom.    The challenge has always been to sort the proverbial "wheat" from the "chaff" to use a popular local idiom.  

          Unlike a Bermuda rig where tension in the rig plays a huge role in shaping the sail, and you have separate head and main sails hanging from the mast, the junk rig has a single sail for all intents and purposes, with the foresail balancing the main to some extent, and the forces on the mast should be pretty basic and simple to calculate.   We have numerous members who have stepped masts of their own design of wood or aluminum often using the most basic and primitive in many cases methods of determining what ought to work, and been quite successful it would seem. 

         Autoclaves, prepreg materials and filiment winding machines are impressive, but  none of those things should be required to build a strong reliable carbon fiber mast.  We have members here perfectly capable of doing the structural calculations.   After all the masts people are using are generally a uniform taper.      As to construction, vacuum bagging and infusion are well documented methods capable of achieving a good laminate without excessive resin, tightly compressed.   I would suggest that a foam core made of disks of XPS, which can be dissolved out with most solvents, could be assembled by sliding onto a tightly stretched cable between two anchor points.  A suitable bearing at either end would allow the works to rotate, and the tension of the cable would keep things straight... probably thousands of KG.    The separate disks, each with a hole to match the cable would be glued together, and then shaped to the final contour of the interior of the mast.  The rotation of the assembly would facilitate this.      Layup might begin with a winding process forming a double helix like hone marks in an engine cylinder, followed by laying on unidirectional fiber to carry the main bending loads.  The helical core ply would be infused or saturated and vacuum bagged first.    The longitudinal plies would be laid down using an epoxy compatible spray adhesive... just very lightly stuck down, and a helical layer could be wound over it, followed by infusing or saturating and vacuum bagging the works.    A layer of glass fiber to protect the carbon within would be incorporated into the final winding.  

         Perhaps just fantasy???   But it seems to me that it could be doable.   Commercial production is one thing, building your own another, and both are doable.    At least one designer I know of.... and have corresponded with in his builder's group has builders producing their own carbon fiber masts for a Ballestron rig, some of which are on very large boats.   His methods are of course secretive..."buy my plans"....  He would be foolish to throw his technology out into the public domain.   I see really no reason why an "open source" methodology for carbon fiber mast construction is not possible, just as is the case for junk rig design.


                                                                  H.W.

    Hi.   HW

    Without trying to retract from your ideas, to me personally sound a little complicated and very little reliable, prone to twisting and deformation.

    I believe that a just much way and probably cheaper exist.   

    Get either an aluminium galvanized steel or other material not suitable for mast construction

    Covering with either a lightsemiinflatable membrane, or arnativelyely a remoulding agent

    Laminate on it either rotating or not

    Deflate the membrane or slightly pressurize de remoulding agent with compressed air or

    Brute force and.     Voila!....carbon fiber mast

    I've seen it done in South Africa many years ago and it works!!!!


  • 29 Dec 2020 16:34
    Reply # 9489914 on 9442600

    The conventional wisdom which includes the "facts" that the Bermuda rig is superior, and that a stayed mast is superior, and other questionable bits of "wisdom", is that building carbon fiber masts is something only professionals should attempt, and that the arrangement of the fiber in the mast is critical and highly individual to the individual application, and far too complex for ordinary mortals to work out... among numerous other questionable bit of "wisdom" mixed liberally in with good sound wisdom.    The challenge has always been to sort the proverbial "wheat" from the "chaff" to use a popular local idiom.  

          Unlike a Bermuda rig where tension in the rig plays a huge role in shaping the sail, and you have separate head and main sails hanging from the mast, the junk rig has a single sail for all intents and purposes, with the foresail balancing the main to some extent, and the forces on the mast should be pretty basic and simple to calculate.   We have numerous members who have stepped masts of their own design of wood or aluminum often using the most basic and primitive in many cases methods of determining what ought to work, and been quite successful it would seem. 

         Autoclaves, prepreg materials and filiment winding machines are impressive, but  none of those things should be required to build a strong reliable carbon fiber mast.  We have members here perfectly capable of doing the structural calculations.   After all the masts people are using are generally a uniform taper.      As to construction, vacuum bagging and infusion are well documented methods capable of achieving a good laminate without excessive resin, tightly compressed.   I would suggest that a foam core made of disks of XPS, which can be dissolved out with most solvents, could be assembled by sliding onto a tightly stretched cable between two anchor points.  A suitable bearing at either end would allow the works to rotate, and the tension of the cable would keep things straight... probably thousands of KG.    The separate disks, each with a hole to match the cable would be glued together, and then shaped to the final contour of the interior of the mast.  The rotation of the assembly would facilitate this.      Layup might begin with a winding process forming a double helix like hone marks in an engine cylinder, followed by laying on unidirectional fiber to carry the main bending loads.  The helical core ply would be infused or saturated and vacuum bagged first.    The longitudinal plies would be laid down using an epoxy compatible spray adhesive... just very lightly stuck down, and a helical layer could be wound over it, followed by infusing or saturating and vacuum bagging the works.    A layer of glass fiber to protect the carbon within would be incorporated into the final winding.  

         Perhaps just fantasy???   But it seems to me that it could be doable.   Commercial production is one thing, building your own another, and both are doable.    At least one designer I know of.... and have corresponded with in his builder's group has builders producing their own carbon fiber masts for a Ballestron rig, some of which are on very large boats.   His methods are of course secretive..."buy my plans"....  He would be foolish to throw his technology out into the public domain.   I see really no reason why an "open source" methodology for carbon fiber mast construction is not possible, just as is the case for junk rig design.


                                                                  H.W.

  • 20 Dec 2020 19:10
    Message # 9442600

    Safety, simplicity, efficiency. - Eric W. Sponberg Naval Architect

    His website is no longer live but thanks to The Wayback Machine you can read his thoughts and opinions Here


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