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Junk Rig Calculator

  • 07 Nov 2013 10:12
    Quote
    Reply # 1429610 on 1420814
    Anonymous member
    Sorry for those who've tried the calculator with touch screen devices. It just occurred to me that the input fields brought up the normal keyboard instead of the numpad. I've change the input fields from type="text" to type="number" and now most mobile browsers should bring up a numpad for inputting numbers. So far tested and confirmed on Android 4.3 (default browser and Chrome) and iOS 7 (Safari).

    Arne, do you have any comments regarding my calculator, especially the Johanna sail part? Would it be okay to add an Aspect Ratio field which simply scales the mast length and battens or is there anything specific (like batten stagger) that needs to be taken into consideration? Maybe a min/max AR?
    Last modified: 07 Nov 2013 10:13 | Anonymous member
  • 06 Nov 2013 21:54
    Quote
    Reply # 1429328 on 1428885
    Anonymous member (Administrator)
    Ash Woods wrote:

    Hi Oscar David and Arne,

     

    Yesterday I downloaded the Generic Fantail Sail Planform and have used it to obtain dimensions for a 30m2 sail. Very useful. Thanks.

    Question is - can I download something similar for the Johanna type rig by Arne?

    I don't have the computer or the brain to follow your above tecky debate and am sure it would be a waste of your time if you tried to explain, but if you could point me towards something I could use similar for Arne's designs that would be great.

    Cheers

    Ash


    I have forgotten what aspect ratio you need for your sail.

    Could you use Johanna's sail plan as you can find here (link below)? That would require half an hour's work with a calculator and a sheet  of paper to scale it to your needed size. I also have a few plans of different AR, so just let me know what you need.

     http://www.junkrigassociation.org/arne

    Arne

     

     
  • 06 Nov 2013 21:30
    Quote
    Reply # 1429315 on 1420814
    Deleted user
    Hi Ash. Sounds as if your brain is like mine - more of the 'suck it and see' kind. David is having some wifi problems at the moment, so give him time. Arne logs on pretty often and as he's the best man to deal with your query re his designs, I'll leave that to him.
  • 06 Nov 2013 21:28
    Quote
    Reply # 1429307 on 1420814
    Anonymous member
    Ash: it sounds like the sail you are planning is almost identical to the one I have on Fantail.  I made a photo essay for the JRA, which can be accessed through Box.  Go to Member's Area/Your Files/Photos/Annie Hill's.  It will give you an idea of what's involved in building that particular sail.  I'm very happy with it.
  • 06 Nov 2013 13:50
    Quote
    Reply # 1428885 on 1420814
    Deleted user

    Hi Oscar David and Arne,

     

    Yesterday I downloaded the Generic Fantail Sail Planform and have used it to obtain dimensions for a 30m2 sail. Very useful. Thanks.

    Question is - can I download something similar for the Johanna type rig by Arne?

    I don't have the computer or the brain to follow your above tecky debate and am sure it would be a waste of your time if you tried to explain, but if you could point me towards something I could use similar for Arne's designs that would be great.

    Cheers

    Ash
  • 06 Nov 2013 00:34
    Quote
    Reply # 1428584 on 1420814
    Anonymous member
    Hehe! I just lowered the Fantail mast length ratio from 1.562 to 1.497 which results in an 11.50 meter mast for a 59 sq m sail.

    I also added a whole new calculation, angle/rake! I put up an illustration to show what the fields represent and added two examples, hopefully it will be sufficient to understand what's going on. The calc might come in handy when making drawings/models of masts/battens/panels.

    Edit: And now that my initial excitement about the new feature has worn off I realize that most people using pen and paper to make drawings probably prefer to use a ruler and a protractor instead of an online calculator. And those making 3D models probably have the calcs implemented in their software already. Oh well. :)
    Last modified: 06 Nov 2013 00:53 | Anonymous member
  • 04 Nov 2013 18:11
    Quote
    Reply # 1427578 on 1427401
    Anonymous member
    Oscar Fröberg wrote:

    Oh wait. Now I'm even more confused. I just checked to see what length (LAP) it would give for David's current 59 sqm sail:

    Fantail: 12 m
    Johanna: 10.68 m

    Looks like there's something weird with the Fantail calcs. David's mast is supposedly 10.5 m LAP, which according to these calcs (sqrt(sa)*1.562) is way too short..? And if 12 m is the recommended minimum, what are the downsides to having a 12.5% (10.5 m) shorter mast? 

    OK, I admit it! I tried too hard to squeeze on as much area as possible. I should have settled for a smaller sail. Yet I only really need another half a meter to be comfortable, though another meter would be more generous. So 11m - 11.5m is all I need. 12m would be too much.
  • 04 Nov 2013 13:11
    Quote
    Reply # 1427401 on 1420814
    Anonymous member
    Don't really know if this question will get enough exposure for an answer here, but I just remade the calculation for Arne's Johanna-type sail (and added it to the calc, based on Johanna's sail plan, sheets 1-9.pdf) and realized that the mast is remarkably shorter than a Fantail one with the same sail area. I would've guessed it to be the other way around, given that the fanned sail is a more low aspect sail than the HM based one. How come?

    For example, recommended mast LAP for a 40 m2 sail:
    Fantail: 9.88 m
    Johanna: 8.8 m

    Oh wait. Now I'm even more confused. I just checked to see what length (LAP) it would give for David's current 59 sqm sail:

    Fantail: 12 m
    Johanna: 10.68 m

    Looks like there's something weird with the Fantail calcs. David's mast is supposedly 10.5 m LAP, which according to these calcs (sqrt(sa)*1.562) is way too short..? And if 12 m is the recommended minimum, what are the downsides to having a 12.5% (10.5 m) shorter mast? 

  • 04 Nov 2013 11:58
    Quote
    Reply # 1427366 on 1420814
    Anonymous member
    Brian thanks, I hadn't noticed the "All the fora" page. It's just feels a bit weird to have a few selected forums in the top level of the navigation menu and then a list with all forums in a submenu. But on the other hand it makes very much sense to have forums like "Swap, sell or buy" in the top level menu.

    As I said I'm fine with moving this to the Projects forum so please go ahead.

    I like the different boxes with new posts from different categories, it makes for a good landing page. And it also makes the old "Recent posts" box less cluttered.

    As for the JR calculator:
    - the input fields are now fixed width, which is a lot easier on the eye
    - removed the Johanna sail calc for now, until I fix the issue with the mast length
    - realized I hadn't notified about browser compatibility so I added a notice with recommended browsers*

    *) Technical rant: I use Linux and test the calculator with Chrome and Firefox, it should also work on Safari which uses (or used, up until a few months ago when Chrome started using Blink, its own WebKit fork) the same rendering engine as Chrome. Opera also uses Blink so it should work fine. Newer Internet Explorer browsers might also work fine but I wouldn't count on older (IE6-8) ones. And I'm not going to waste my time making the calculator compatible with people not wanting to waste theirs with upgrading their browsers. There are just so many small cool things you can do (as a developer) with modern browsers. The most common (reasonable) argument for using an old IE browser is that it's the only browser they have at their workplace and they're not allowed to install anything else. In which case I feel very sorry for you but you should probably do your JR calcs on your free time instead. ;)

  • 31 Oct 2013 20:25
    Quote
    Reply # 1425687 on 1420814
    Deleted user
    OK wrong place for this chat, Oscar, but thanks for and re your suggestion for a link to all the fora, try the Members' Area button on the left then > All the fora - it's been there forever. Maybe bookmark it.

    If we leave this project here it will just get lost like most fora threads do in the end. Lesley and I are trying to gather members' projects in a single place. Each change we make some like and some don't. How do you like the separate projects and other fora updates on the members' area page?


    Last modified: 31 Oct 2013 22:31 | Deleted user
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