Mast Breaking Strength - Junk Rig Calculation Tools

  • 18 Apr 2018 19:08
    Reply # 6109416 on 6101804
    Deleted user

    Have you checked the weight on the Hurricane poles?

    Yes I looked at those too but with a wall thickness of .188 and .250 I ruled them out due to weight.  One of the 30ft x .250 tapered sticks weighed 361 lbs if I recall. Seemed like too much weight to be flailing around above the deck in a seaway.

    If you scan below you'll see Arne questioned the first pole I was looking at, 188 lbs, as out of line.

    As Oscar told me (beginning of this thread): breaking strength depends on thickness vs diameter.  Granted, the .250 wall thickness will drive up the breaking strength, but it  also drives up the weight too, considerably.

    The first 30ft x 6" flag pole I was looking at had a breaking strength of 1845 kpm  but weighted 188 lbs.

    The latest iteration is a 30ft x 7" light pole, same wall thickness, with a breaking strength of 2541 kpm and weighs 122 lbs. Stronger, lighter less expensive, with only slightly larger diameter.

    These poles are all 6063 T6. Not sure why the flag pole weights so much more than the light pole. This bothers me - more research.

     careful, that Hurricane pole might come in two pieces

    Last modified: 18 Apr 2018 19:10 | Deleted user
  • 18 Apr 2018 18:23
    Reply # 6109344 on 6108435
    Deleted user
    Dave Rieger wrote:
    David Dawes wrote:


    https://www.libertyflagpoles.com/collections/external-halyard-commercial-flagpoles

    http://www.americanflagpole.com/flagpoles/

    https://www.colonialflag.com

    https://www.lightmart.com/ These guys also make fiberglass poles and are the guys that ran when I mentioned using one as a mast

    https://lightpolesplus.com  !!! It pays to research !!! This is the one - Same spec as the one I mentioned below but 121 lbs as a Light pole, and these guys have an anodize option too! Turns out to be less expensive than the flagpole I was looking at. Arne's instincts are correct (again)


    Hi--

    I don't see:

    https://www.united-states-flag.com/hurricane-series-30ft-flagpole-external-halyard-ech30.html

    in your list. They have cone-tapered 6063-T6 AL poles. I've seen these poles on Ebay with free shipping.

    Last modified: 18 Apr 2018 18:24 | Deleted user
  • 18 Apr 2018 09:19
    Reply # 6108676 on 6101804
    Anonymous member (Administrator)

    Like David, I prefer the mast to have enough stiffness in it. However, the 150 x 5mm lower mast tube for my own 2150kg Ingeborg, appears to be plenty stiff enough.

    The mast cannot be too strong, but I always try to keep the weight and windage of it as low as possible without spending zillions on carbon.

    If the boat were mine, I would have opted for the slimmest alternative  -  that is, if those 1845kpm is yield strength and not breaking strength. I would not be so happy to return to harbour with a 10° bend in the mast...

    Arne

    PS: What is the specs for the aluminium material; 6063-T6, 6082-T6...?

     


    Last modified: 18 Apr 2018 09:21 | Anonymous member (Administrator)
  • 18 Apr 2018 08:08
    Reply # 6108621 on 6101804

    Dave, the "new pole" spec is the one that I would choose for a Cape Dory 25. Either spec would be strong enough, I think, but I always value the extra stiffness that comes with a greater diameter.

  • 18 Apr 2018 03:37
    Reply # 6108441 on 6101804
    Deleted user

    Actually looking a little closer. The spec on my new option is still 3.98mm wall thickness but the base diameter is 177.8 (7") rather than 152.4 (6") 

    previous pole:

    • Length -     10.05 m
    • Base dia -  152.4 mm
    • Top dia  -   88.9 mm
    • wall thick - 3.98 mm
    • mass -  39.6 kg
    • Breaking  - 1845 kpm

    New pole:

    • Length -     10.05 m
    • Base dia -  177.8 mm
    • Top dia  -    101.6 mm
    • wall thick - 3.98 mm
    • mass -       46 kg
    • Breaking  - 2541 kpm

    Can you have too much 'Breaking strength' ?


  • 18 Apr 2018 03:14
    Reply # 6108435 on 6108343
    Deleted user
    David Dawes wrote:

    Hi David, I am in Newport RI and considering a conversion of something in the 25-30 foot range so US sources of masts interest me.  Please share your findings especially price with us!


    Incidentally I contacted Dabbler Sails in the Chesapeake out of interest when I saw they made a cambered junk sail for a Compac 23..........price was US$3,560!!!!


    They are not taking anymore orders.....regardless at that price I think it is a winter basement project at home!


    Best of luck with your search!


    Yes I contacted him a week or two ago too. A cambered sail would seem to be a complicated project so I wasn't surprised at the price.  He also said that a 'standard' flat panel sail of that size would be 2/3 less IF you had detailed drawings for it but he was booked 6 mo in advance. As you might expect with a good loft. Then he suggested I could do it myself with a little practice on an old zigzag machine. Sewing is not a skill I currently have. Not sure if I want to spend the time to learn that one at this point.

    As far as aluminum masts I just googled Flag poles and Light poles. One of these is on the east coast. I forget which one. My new best option (below) is in the general neighborhood - Wisconsin) Save some money if I can figure a way to pick it up myself.

    https://www.libertyflagpoles.com/collections/external-halyard-commercial-flagpoles

    http://www.americanflagpole.com/flagpoles/

    https://www.colonialflag.com

    https://www.lightmart.com/ These guys also make fiberglass poles and are the guys that ran when I mentioned using one as a mast

    https://lightpolesplus.com  !!! It pays to research !!! This is the one - Same spec as the one I mentioned below but 121 lbs as a Light pole, and these guys have an anodize option too! Turns out to be less expensive than the flagpole I was looking at. Arne's instincts are correct (again)

    After my experience with Lightmart and the fiberglass pole, I think I'll have to be careful how I approach the next candidate. I wouldn't let them know what I'm doing until after I have the pole. Guessing they're afraid of getting sued.

    on edit:

    Forgot to mention - I contacted a carbon fiber mast manufacture several weeks ago and priced a carbon fiber mast with sail track (to use the original triangle on the CD25). He thought it was a great project! ...$20,000 for the complete mast, boom, spreaders.


    Last modified: 18 Apr 2018 03:43 | Deleted user
  • 18 Apr 2018 01:23
    Reply # 6108343 on 6101804
    Deleted user

    Hi David, I am in Newport RI and considering a conversion of something in the 25-30 foot range so US sources of masts interest me.  Please share your findings especially price with us!


    Incidentally I contacted Dabbler Sails in the Chesapeake out of interest when I saw they made a cambered junk sail for a Compac 23..........price was US$3,560!!!!


    They are not taking anymore orders.....regardless at that price I think it is a winter basement project at home!


    Best of luck with your search!

  • 18 Apr 2018 01:07
    Reply # 6108337 on 6101804
    Deleted user

    Interesting. Less weight would be better. still looking actually, haven't settled on this one. But that's the weight listed in the  brochure:

    http://www.americanflagpole.com/dwg-pdf/ESR30C61-02.pdf

    There are a few suppliers near by and I intend to visit them soon

    Last modified: 18 Apr 2018 01:08 | Deleted user
  • 17 Apr 2018 10:10
    Reply # 6102356 on 6102155
    Anonymous member (Administrator)
    Dave Rieger wrote:


    The thing weighs 188 lbs (85.275kg)



     That sounds heavy for that dimension, unless it is a very tall mast. Could it be that those 85kg is shipping weight instead of actual, installed weight? I would expect something around 50kg, +/- 10%.

    Arne


    Last modified: 17 Apr 2018 10:12 | Anonymous member (Administrator)
  • 17 Apr 2018 04:01
    Reply # 6102155 on 6101804
    Deleted user

    LOL! Well, THAT was quick.....and easy. Thanks!

    For some reason I can get aluminum flagpoles anodized, but Light poles only come powder coated or plain (quick search).  I think hard anodized would be better for this.

    That would make it an anodized 10m Flag pole 152.4 butt x 88.9mm top and 3.98 mm wall

    kpm = 1845

    The thing weighs 188 lbs (85.275kg)

    Thanks for getting me off to a quick start.

    (LOL quick start....I started to build a JR FC 35ft in the late 70's)

    More to follow I'm sure.

    Thanks again.



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