Welcome anonymous guest

Please Support
TheBeachcats.com

New bridle on Nacra 5.5  Bottom

Go to page [-1] 1 - 2:

  • deleted



    Edited by revintage on Jun 12, 2018 - 06:05 AM.

    --
    Brgds
    Lars

    Frankencat 5.5/F18
    Soon Frankencat 5.8/F20
    49er
    --
  • Quotea=34 BT=FT*.9 for each wire, H=838mm, Tornado


    At last I found some info about Nacra bridles, they use the same angle as Tornado. Calculated 5.0 and 5.8(not NA) and they both are 34 degrees.

    My previous figures for Nacra 5.5 where way off. With Frankencat bridle height of should be min. 85cm, not 107cm.

    If you go down to 46cm, load is 2.9 which means the rear going will have to take 1.1 of the forestay tension.

    If you go down to 33cm, load is 3.9 which means the rear going will have to take 2.1 of the forestay tension.

    A static tension of 100kg would be no problem.

    Still wonder how many times higher the dynamic load upwind will be? icon_mad

    If we tie the rear going wire(5mm Dux) to the center of the rear beam we will get severe deflection with a dynamic load of maybe 4-500kg.

    If we instead split the wire in two, to another bridle behind the striker rod, with each end tied to the inside beam ends(tube walls 5mm at the ends), things look a little better. It should be made of a single loop turning back at the rear end of the turnbuckle.

    The striker rod is made up of M16 threaded stainless rod, with a 20x2mm alu tube covering it. It is used to prebend the main beam with a 40x3mm stainless striker band. As the rear wires only will go through an eye at the bottom no for/aft forces will be present.

    Cleaned up the GC32 to show my idea. You will have to imagine the forestay bridle and bowsprit is lifted 34cm. The rear bridle tension is a guesstimate.

    Using the same 5mm Hampidjan Dynice Dux as in the forestay, makes this a light construction, although the rope is $7.50/m in Sweden.

    http://racerdirekt.com/pelican.png



    Edited by revintage on Jun 12, 2018 - 06:12 AM.

    --
    Brgds
    Lars

    Frankencat 5.5/F18
    Soon Frankencat 5.8/F20
    49er
    --
  • You'll have to be careful with those wires when righting the boat..
  • Hi Andinista,

    Will take care!

    Made a spreadsheet for the COS/SIN part to find out the forces and tensions involved. Formulas below.

    Have done something wrong and then gone blind as neither signs(T3 should be negative) nor values add upp. A little ashamed as this is basic math/physics. Do you mind taking a look?

    http://racerdirekt.com/pelican.xls



    Edited by revintage on Jun 14, 2018 - 06:50 AM.

    --
    Brgds
    Lars

    Frankencat 5.5/F18
    Soon Frankencat 5.8/F20
    49er
    --
  • Sorry, found some errors and measured some more on the boat. Looks as we will have ca 3x compression force to the rear at the front beam and ca 2.7x at the pelican striker. Looks reasonable to the earlier, no math, ballpark figure of 2.2.

    http://racerdirekt.com/pelican.xls



    Edited by revintage on Jun 14, 2018 - 07:34 PM.

    --
    Brgds
    Lars

    Frankencat 5.5/F18
    Soon Frankencat 5.8/F20
    49er
    --
  • deleted



    Edited by revintage on Jun 14, 2018 - 05:12 PM.

    --
    Brgds
    Lars

    Frankencat 5.5/F18
    Soon Frankencat 5.8/F20
    49er
    --
  • Sorry.. been working a lot a now preparing to go skiing.. i’ll check when I find some time



    Edited by Andinista on Jun 15, 2018 - 10:20 PM.
  • No need to help, solved it myself.

    1kN fore stay tension; Compression force and pelican striker tension are close to the same at 2.5kN each when keeping the intitial a=34 degree bridle tension. Used 35cm bridle height and 30cm from c/c beam to end striker rod.

    Still, question is what happens to the main beam with the spin pole force of 2.5kN pressing against the front side.



    Edited by revintage on Jun 16, 2018 - 04:33 PM.

    --
    Brgds
    Lars

    Frankencat 5.5/F18
    Soon Frankencat 5.8/F20
    49er
    --
  • By adding a small "dolphin striker"(DS), you can possibly get around the problem with the main beam deflecting to the rear.

    In total this will anyway be lighter than a Nacra style bridle foil.

    Due to the angles involved the original dolphin striker and the mast will contradict the force from the bowsprit.

    http://racerdirekt.com/pelican2.png



    Edited by revintage on Jul 01, 2018 - 10:48 AM.

    --
    Brgds
    Lars

    Frankencat 5.5/F18
    Soon Frankencat 5.8/F20
    49er
    --
  • I store my righting pole under the tramp, after a while the tramp started to show signs of wear, I suggest to add some protection, like a cordura or vynil patch. Maybe add some color above, around the area, to identify it easily, stepping on the cable or rod can be painful, particularly when stepping the mast.
  • Hi Andinista,
    Thanks for the advice. My idea was a max 20cm strut for the DS. Will use 5.5mm(when stretched) Dyneema for the strap, thinner might hurt more. Hopefully the DS not in the way, but beware of traps on the trampoline icon_wink ! Will publish an image when it is done, but will first test deflection without the rearward DS.

    --
    Brgds
    Lars

    Frankencat 5.5/F18
    Soon Frankencat 5.8/F20
    49er
    --
  • it appears that you are experts on Nacra 5.5 SL. Just purchased one and mast came down in a storm, cat moored in 5 feet of water so my initial reaction was to save mast as quickly as i could and dove in and disconnected all ropes etc without paying attention to detail, mast and stays ok But i have no idea where everything is supposed to go once mast is raised! all u tube and other instructions on catsailor & this site not specific as to 5.5 show 5.2 which i previously owned and know the details, only sailed this 1994 Nacra 5.5 once- for example there is a stainless square ish apparatus that attaches to mast and pulleys at base of mast dont remember correct configuration! are photos available? WOULD APPRECIATE ANY HELP, PS FOIL FOR JIB OK BUT PROPER REATTACHMENT ON THAT WOULD BE APPRECIATED AS WELL
  • Hi Nofear.....
    This might help you:https://www.nacrasailing.…tage-assembly-manual.pdf

    --
    Brgds
    Lars

    Frankencat 5.5/F18
    Soon Frankencat 5.8/F20
    49er
    --
  • thanx, but doesnt show tiangular chrome/ stainless apparatus/1/4 to1/8 inch in diameter bar, or pulley systems hook up
  • nofearofflyingthanx, but doesnt show tiangular chrome/ stainless apparatus/1/4 to1/8 inch in diameter bar, or pulley systems hook up


    Are you asking about the mast rotation control arm?
    https://www.thebeachcats.…ms/viewtopic/topic/16211

    --
    Ron
    Nacra F18
    Reservoir Sailing Assn.
    Brandon, Mississippi
    --
  • Personally I would do like Arch in the linked thread, with the rotator pointing to the rear and adding an eyelet in the trampoline for the trim line.

    --
    Brgds
    Lars

    Frankencat 5.5/F18
    Soon Frankencat 5.8/F20
    49er
    --
  • revintagePersonally I would do like Arch in the linked thread, with the rotator pointing to the rear and adding an eyelet in the trampoline for the trim line.

    On a boomless cat you want to induce rotation more often than to limit it, don’t you?
    That’s my case at least, I even miss sometimes the wide rotator that allows over rotating. But for me the real deal is to be able to firmly lock the mast centered when not sailing, especially after a shroud failed at night on a buoy. The configuration pointing fowrward works perfectly, the other one doesn’t seem so. Still much better than not locking at all, though.



    Edited by Andinista on Jul 11, 2018 - 08:06 AM.

Go to page [-1] 1 - 2:

This list is based on users active over the last 60 minutes.

  • October 20, 2018
  • No events scheduled.

Upcoming Beachcats Events

VIEW FULL CALENDAR