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Mast Database

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  • 20 Jul 2013 04:35
    Quote
    Reply # 1347631 on 1343924
    Anonymous member
    Arne Kverneland wrote:BTW Annie, you have given all the data needed to find the breaking (or yield) strength:

    First, from the web I find that the 6261-T6 alloy has a yield strength of 255MPa (=255Newton/sqmm =26.0kp/sqmm). With the outer diameter of 152mm and wall thickness of 5mm, the breaking strength should come out at 2136kpm (1kp= 1kg force) if I have typed in the numbers correctly. That should be at least 1.5 times the righting moment of your boat. Good for you that David Tyler helped you with this.

    Um, well, yes Arne.  Clear as mud - I am so pleased that you concluded by telling me that it is at least 1.5 times the righting moment of my boat 'cos I have to tell you that 2136kpm means absolutely nothing to me!  I, too, was happy to have David advise me, but I seem to recall going up in size from his recommendations when I came to buy the alloy tubing.

    My point with wanting a place to put the breaking strength in the mast database is that unless we take these calculations a bit more seriously, the masts will continue to tumble down, even in not-extreme conditions.


    I'm sure we all agree with this, but we have to hasten slowly.  At least we have a database of boats with masts that haven't yet fallen down, or if they do fall down, I trust we will get some feedback on it.

    This is really Mark's project, but I'm sure if he gets enough breaking strength data, he will add it to the spread sheet.  As ever, many thanks for your input, Arne - the JRA would be much less of an association without you.
  • 19 Jul 2013 08:07
    Quote
    Reply # 1343924 on 1174238
    Anonymous member (Administrator)

                                                                         Stavanger, Friday

    In Newsletter/Magazine 48 from 2007 I wrote about calculating breaking strength in wooden masts and how to relate it to the boat’s stability. The article was slightly corrupted in print so I have uploaded it to "my" folder. Or just check this link. Not all of it may be relevant today and a new article covering aluminium masts should be written. Maybe later, I am a bit busy now.

    BTW Annie, you have given all the data needed to find the breaking (or yield) strength:

    First, from the web I find that the 6261-T6 alloy has a yield strength of 255MPa (=255Newton/sqmm =26.0kp/sqmm). With the outer diameter of 152mm and wall thickness of 5mm, the breaking strength should come out at 2136kpm (1kp= 1kg force) if I have typed in the numbers correctly. That should be at least 1.5 times the righting moment of your boat. Good for you that David Tyler helped you with this.

    My point with wanting a place to put the breaking strength in the mast database is that unless we take these calculations a bit more seriously, the masts will continue to tumble down, even in not-extreme conditions.

    Cheers, Arne

    PS: The rain has stopped, must go and do some painting on Frøken Sørensen

    Last modified: 23 Jun 2017 22:47 | Anonymous member (Administrator)
  • 19 Jul 2013 01:29
    Quote
    Reply # 1343796 on 1343227
    Anonymous member
    Arne Kverneland wrote:

    I had a look at the mast spreadsheet, but could not find "calculated breaking strength". Is there a reason for that? Is breaking strength irrelevant? I think not...

    Arne


    I wouldn't even know how to calculate that Arne.
  • 18 Jul 2013 23:41
    Quote
    Reply # 1343742 on 1343227
    Anonymous member
    Arne Kverneland wrote:

    I had a look at the mast spreadsheet, but could not find "calculated breaking strength". Is there a reason for that? Is breaking strength irrelevant? I think not...

    Arne

    Yes, Arne, it's entirely relevant, but I think it's fair to say that the vast majority of people who have taken the trouble to enter any data they have for their rigs into their profile, have only the haziest idea of what the calculated breaking strength of the mast is.  They have made their choices from following tried and tested formulae. Certainly I have no idea how much load my mast could take. If you (or anyone else) could asses this information, we could add the appropriate column.
    Last modified: 18 Jul 2013 23:42 | Anonymous member
  • 18 Jul 2013 13:22
    Quote
    Reply # 1343227 on 1174238
    Anonymous member (Administrator)

    I had a look at the mast spreadsheet, but could not find "calculated breaking strength". Is there a reason for that? Is breaking strength irrelevant? I think not...

    Arne

    Last modified: 18 Jul 2013 14:06 | Anonymous member (Administrator)
  • 18 Jul 2013 11:58
    Quote
    Reply # 1343191 on 1174238
    Anonymous member
    I've added my wall thickness of 40mm (4cm) to my profile details.
  • 15 Jul 2013 00:37
    Quote
    Reply # 1340233 on 1174238
    Deleted user
    Thanks Graham. I think we'll leave as is for a few weeks and then update again re any comments here. The team much appreciate your thanks!
  • 15 Jul 2013 00:11
    Quote
    Reply # 1340217 on 1174238
    Anonymous member
    Had a look at the mast database.  A nice resource for people engaged in rig projects.  I noticed a couple of things about my entry.  The mast diameter at the partners is 200mm (listed as 190) and the sail area is 35sq m (listed as 24).  Also I had not recorded wall thickness which is 5mm.  Not sure where you'd put it, but the construction is spun-tapered alloy, which is hard to find and expensive.  A hybrid mast like Annie's, with a straight alloy extrusion at the bottom and a tapered timber top is a much cheaper option for those on a tight budget.  Well done, team!
  • 14 Jul 2013 23:57
    Quote
    Reply # 1340204 on 1174238
    Deleted user
    Can any members help with any of this information?

    There's no Irena in Directories > Members' Boats, and the Excel database shows Irena as being owned by Asmet Kahn, but the boat list shows he owns Branwen. Has anyone ever heard of Irena?

    What's the data for Lexia's new mast, please, Jonathan?

    Windsong is on the mast database, row 14, but not in the site's list of members' boats. We believe Paul Calvert owned her, but he's no longer a member. Is anyone able to contact him? Please don't publish his contact details here, as this is a public forum. Instead please email them to sailsec@junkrigassociation.org

    Finally if anyone would help to take the database a stage further by updating it as new data is added to members' profiles, please email webmaster@junkrigassociation.org
    Last modified: 14 Jul 2013 23:59 | Deleted user
  • 14 Jul 2013 23:41
    Quote
    Reply # 1340200 on 1174238
    Deleted user
    For the last few months Annie Hill, Daniel Collins and Mark Thomasson have been working hard between boat projects and Life to extract mast information from members' profiles (currently 400+) to create a database which we hope will be of interest and help to members. Although there are a few queries which I'll list below in the hope that YOU can help, this is now published here as an Excel file. Unfortunately it only details mast information for 80 boats; we'd like to thank those 80 members for taking the time to fill out their profile so well.

    The database can also be accessed fro Junk Information > Useful links > Sails, Masts and Gear.

    Of course any database is only as good as the data that goes into it, so the above members and the JRA can't guarantee 100% accuracy - we did our best. Can you help with the queries below?


    Last modified: 15 Jul 2013 00:09 | Deleted user
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