Frankenboat/Wishbone

Discussion in 'Sailboats' started by revintage, Apr 23, 2019.

  1. revintage
    Joined: Nov 2016
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    revintage Senior Member

    Played around with some items I found in the backyard this Eastern. BIC 410 hull(free), Flipperjolle rotating round mast tube($50), Blaze prototype sail($100), boom from an old Windglider windsurfer(free), 1m alu tube to extend the boom($15), Nacra 5.5 rudder blade(free) and a roll of Dyneema(on sale at $0,2/m).

    Got as far that I could hoist the main and realize the mast and the extensions for the boom where to short. Will add the 8" extension to the mast top and if that isn´t enough I also have an extender for the lower mast end. About the boom it should probably be long enough just by sliding it down its track under the spreaders as it seems be angled to much upwards. I can also pull out the extensions almost 2". The sail will of course look better with all of its battens in place.

    Next step is adding the same type of lightweight racks I am using on the Frankencat, seen to the left leaning against the shed.

    As I have never play with wishbone rigs before, are there any rules of thumb to make it work acceptable?

    No comments about how worthless this type of rig is, please;).

    IMG_3517.jpeg
     

    Attached Files:

    Last edited: Apr 23, 2019
  2. tlouth7
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    tlouth7 Junior Member

    Can you adjust the wishbone angle and tension independently while on the water? That would give you a really nice outhaul and kicker (vang) functionality because angle adjusts the foot:leach tension ratio. It looks like the wishbone would crash into the forward lower shroud though.

    Are you happy with the position of centre of effort? If you could rake the mast forward it would increase space under the foot without extending the mast.
     
  3. Doug Halsey
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    Doug Halsey Senior Member

    The rule of thumb I've heard for the wishbone angle is that it should bisect the angle at the clew. That's only a very rough starting point though.

    tlouth7 has the right idea about making it adjustable, but I was never happy with my clumsy attempts to do that on Broomstick.
     
  4. Doug Halsey
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    Doug Halsey Senior Member

  5. revintage
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    revintage Senior Member

    The original rig of the BIC 410 is probably one of the ugliest ever seen. Have only found this on the internet.

    bic410tech.jpg



    tlouth7, there is an option to move the boom up and down as I used a 10" jib sheet track and traveller on the front of the mast just below the spreaders. Instead of using the clickstops it could easily be made continuously variable.

    Studied outhaul and sheeting of Waszp and will use the same system. Nice 3D pdf to download from here: WASZP 3D PDF http://www.waszp.com/waszp-3d

    About lowers there aren´t any, as the mast is rotating and has beachcat style diamond configuration for the spreaders. The spreaders will be made 3" longer to give even better clearance. The third forward pointing spreader is adjustable to limit mast bend, if needed. Actually the diamond system is the original from the mast that I have extended as the spreaders where extremely short.

    About CoE it seems to be in the ballpark and can be adjusted, as the daggerboard slot is much longer(will make an adjustable adapter), than the chord of the Windknife FF27 daggerboard section I will use. It might be necessary to move the mast base more forward, though.

    Doug, checked my image and the boom seems to bisect the clew. My initial feel was that it is a little to high as foot tension was very low and leach tension the opposite. Was actually a little inspired by your smaller Broomstick rig and also found a thread you started about wishbone, but the answers didn´t make me any wiser. Thanks for the SA links, will study them.

    All in all, trial-n-error will surely be the best way to go. Learning-by-doing still rules.
     
    Last edited: Apr 25, 2019
  6. messabout
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    messabout Senior Member

    The picture suggests that the boat will have a bitchin' lot of weather helm.......depending on the location of the board. I suspect that the mast might need to be moved forward for some distance.

    That is a gorgeous and sinfully originally expensive sail. I wish that I could find one in that condition for the price you mentioned.
     
  7. revintage
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    revintage Senior Member

    messabout, not so sure about that, but will draw it up graphically with the help of the line drawing from the leaflet above, before water test. Discussed that earlier, as tlouth7 suspected the same.

    Anyway the daggerboard slot is very long wrt to my Windknife 27cm chord daggerboard section. Images shows most farward, most rearward position and opening in hull.

    If not enough, I will bolt slab of 12mm or 20mm HDPE from my stash, to the ABS bottom to spread the load. The mastfoot has a 10mm pin at the end. Will then drill a row of holes in the slab to find the correct mast position.

    The sail is a nice find from eBay UK. Actually a prototype that never went into production. Blaze sails are 10,5sqm with only one full batten, while this is 8,5sqm.

    forward.jpg rearward_resultat.png hull.jpg
     
  8. revintage
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    revintage Senior Member

    Did a very corse drawing indicating the rig might be moved ca 20cm forward if the original daggerboard was used. Maybe sail CoE is also a little more forward?
    BICCOE3.png
     
  9. messabout
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    messabout Senior Member

    I suspect that you are well aware of the "lead" concept. The fore/aft distance between the CE of the sail and CLR of the boat and board, by some amount that is determined by the SWAG (scientific wild *** guess) method.

    Your Frankenboat is a credit to your creativity. Good luck with the project.
     
  10. revintage
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    revintage Senior Member

    Thanks. SWAG method is good. My scientific/empirical approach to that one, will be by both finding the daggerboard angle and moving the mast foot to the hole that gives just a tiny weather helm;).

    Actually did this to evaluate if a wishbone rig can be used on my Windknife foiler, Windknife trifoiler build https://www.boatdesign.net/threads/windknife-trifoiler-build.61518/. Doug Halsey tried it on his Broomstick but didn´t like it, anyway think it is worth a try.
     
  11. tlouth7
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    tlouth7 Junior Member

    Looks like you need to get it on the water asap and see whether the balance is good as-is. If not I would still suggest losing the mast rake before moving the mast foot. You will have to adjust the shrouds either way but changing the rake doesn't require any additional hardware.
     
  12. revintage
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    revintage Senior Member

    The 195mm extension on top of the mast, together with the added extension of the boom seems to be just perfect . Made a new mast base from HDPE(nice material to work with), forward of the previous and used the original for fitting for the exclusive Swiss Oxen ratchet main sheet block. Mast in its most forward position and wishbone in its lowest position on the mast.

    Lots of soft shackles needed to make everything work and also being easy to detach. Every trim is extremely dependant of each other. Anyway it looks promising and worthwhile testing on water.

    Used the Waszp concept and will now refine everything. Downhaul will be led to camcleats each side just forward of the forward beam tube.

    The GRP battens that where delivered with the sail, are non tapered, will have to grind them down at the front.

    Time to rebuild the 80-90cm wings and add rudder and daggerboard!
     

    Attached Files:

    Last edited: May 7, 2019
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  13. revintage
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    revintage Senior Member

    Finished the Waszp style sheet arrangement, outhaul and downhaul(decided to go 8:1 instead of 6:1). Will adjust wishbone height position when on water. Also began building the racks. Two weeks left to first sailing test. Love that sail!

    IMG_3633.jpg IMG_3133.JPG IMG_3132.JPG
     
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  14. tlouth7
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    tlouth7 Junior Member

    I love it! That leach is a thing of beauty. The racks look slightly terrifying though
     

  15. revintage
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    revintage Senior Member

    Haha, no worries;)! The racks will completed with an inner tube with a net between the inner and outer.

    This is my 1ft 4" widened Nacra 5.5 with completed racks. The leeward rack is automatically lifted when you sit on the windward. The forward end is hung in the trapezewire, that also carries the lifting mechanism.

    I use 50x2mm alu tubing together with high pressure PVC fittings.


    racks.jpg
     
    Doug Halsey likes this.
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