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Understanding Top Down Furling  Bottom

  • I have a spin coming for my N5.2 and I am back and forth between furling and a SNU type mid-pole bag. I drafted a design to make a top down furler using my spare H18 furler and swivel, but I feel that I must be missing something because it seems too easy.
    If one had a monohull with a furling headsail, you would have an AL track up the luff. If you put the spin head on a track car and hoisted it with the clew on a deck cleat it would seem that you would have top down furling. The AL track would be the torque rope.
    My plan was to use 3/4" PVC electrical conduit as the torque rope/forestay (headstay?) and convert my H18 furler to a endless line drive. I can pickup the conduit for $10 and I have all the other parts. I have other concerns regarding the additional luff length on my beast RS800 spin. Would this work?
    If not, I'll start hunting for a tennis racket to make my snuffer.

    --
    Robert
    81' NACRA 5.2 "Chris's Flyer"
    Previously owned H18, Trac 14, G-Cat 5.0, H14T, H16, N5.0
    BYC, Mobile, AL
    --
  • Quoteit with the clew on a deck

    I mean tack to the deck.

    --
    Robert
    81' NACRA 5.2 "Chris's Flyer"
    Previously owned H18, Trac 14, G-Cat 5.0, H14T, H16, N5.0
    BYC, Mobile, AL
    --
  • rch701I have a spin coming for my N5.2 and I am back and forth between furling and a SNU type mid-pole bag. I drafted a design to make a top down furler using my spare H18 furler and swivel, but I feel that I must be missing something because it seems too easy.


    Yes, it is too easy.

    After struggling for many years to make top down, bottom up and SNU style snuffers work smoothly and consistently I tried a top down furler when I ordered a Code 0 last year. I ordered it with a Selden CX-10 Continuous Line Furling Unit. I will never go back to a snuffer. It really is that easy.

    QuoteIf one had a monohull with a furling headsail, you would have an AL track up the luff. If you put the spin head on a track car and hoisted it with the clew on a deck cleat it would seem that you would have top down furling. The AL track would be the torque rope.


    Not how it works with modern monohulls. All the performance monohulls I can think of for many years now are now using Anti-Torsion line with Asymmetric Spins. I am even seeing this technology bleed over into the cruising monohull market so cruisers can get rid of spinnaker poles and more easily sail short handed.

    One of the benefits of using an Anti Torsion line in the luff is I can drop the headsail easily and stow it on the deck to reduce wind resistance on screaming reaches and also swap quickly between different headsails.

    I am not sure a PVC conduit will hold up well with torsional (twisting) force on it. I suspect it will give up at the tack or head. The torsional forces to furl the sail are suprisingly strong. Just look at the drum diameter (mechanical advantage) of top down roller furling systems. They are bigger than jib drums for a reason. Also, the luff on most Asymmetric spins is not straight. So unless your RS800 spin luff is almost perfectly straight using conduit in place of AT line will have very bad impact on sail shape.

    The good news is AT line is a lot less expensive than it used to be and it is not a big deal for your local sailmaker to add it.

    Please let us know how it works out.

    Brad in Jacksonville, FL
    currently 2x Stiletto 27's (one for sale after the Mug Race)
    First cat was a H-16 with rum runner sails new in 1983 and I still miss it.



    Edited by bradinjax on Feb 15, 2021 - 11:57 AM.
  • I ran a calc on the PVC pipe. 27ft of 3/4" with 12.5ftlb of torque on the shaft would induce a twist of 80 degrees. When the sail was furled it would unfurl a 1/4 rotation. This may be a worst case scenario because with a 6" furler wheel that would be 50lbs on the furling line. The sail came in today. I'll rig something up next weekend.

    --
    Robert
    81' NACRA 5.2 "Chris's Flyer"
    Previously owned H18, Trac 14, G-Cat 5.0, H14T, H16, N5.0
    BYC, Mobile, AL
    --
  • you plan to sail around with 27' of pvc with a spin furled around it ?
  • Quoteou plan to sail around with 27' of pvc with a spin furled around it ?

    What!? MN3, You saying you're too cool to hang with me? With my bright yellow spin it will look like a ray of sunshine!

    --
    Robert
    81' NACRA 5.2 "Chris's Flyer"
    Previously owned H18, Trac 14, G-Cat 5.0, H14T, H16, N5.0
    BYC, Mobile, AL
    --
  • icon_cool icon_cool icon_cool icon_cool icon_cool

    I have seen many ghetto spin setups - that could be a top 10 :)
    we had a supercat 19 with a homemade pvc end snuffer - looked just like a toilet bowl
    also seen the 5 gal bucket snuffer end

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