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Nacra 5.7 Bridle Foil  Bottom

  • We have been searching unsuccessfully and were unable to locate one of these units so we fabricated our own. If anyone is interested in more information please send me an email at: ggrose@pst.hrcoxmail.com and I will send you pictures.

    The foil works perfect! We have sailed with it in 20 knot winds. The boat seems faster and more stable.

    I posted here to see if there is enough interest for me to fabricate additional units for sale. The assembly is constructed of a welded aluminum extrusion with stainless steel hardware. Custom lengths can be fabricated depending on boat specifications.



    Edited by turtleman on Oct 04, 2013 - 07:51 AM.
  • I have seen this foil and the workmanship is top notch. For those that are interested you will not be disappointed.

    --
    Kevin
    Wantanacra
    VA Beach, VA

    Nacra 5.0
    Nacra 5.2
    --
  • Are you still manufacturing these foils? I'm interested in seeing pictures and cost.
  • I made a foil from parts of a h16 I took apart.I used a side rail and the dolphin striker,I will get photos today

    --
    Carl

    Dart 18

    50% 1967 B-LION for sale
    1985 Hobie 18
    Windrider Rave
    --
  • The jib will be lower, which is the whole purpose to my understandig. You also have to put the jib blocks further forward.
  • I'm not sure I understand the reasoning for this mod.
    I get that a foil changes the bridal loads to a "better" angle.
    So far, these 30+ year old boats are staying together.
    I really don't think they can be made to go any faster, or point any higher, at least not to any degree in real world sailing. The fact is, a skeg hull has reached it's potential, & we will always be beaten to booms & boards, given equal nuts behind the wheel.
    What is the point of lowering the jib any further?
    The jib mainly acts to accelerate air over the lee of the main. If the 5.7 is properly setup, the jib foot is level with the mains foot, giving the most help it can. Dropping it below the main gives some of that up.

    --
    Hobie 18 Magnum
    Dart 15
    Mystere 6.0XL Sold Was a handful solo
    Nacra 5.7
    Nacra 5.0
    Bombardier Invitation (Now officially DEAD)
    Various other Dock cluttering WaterCrap
    --
  • Boats that have bow foil by design can fit a bigger jib, not
    Just lower. I agree that the modification doesn’t seem to be worth it.



    Edited by Andinista on Jan 08, 2018 - 05:37 AM.
  • lowering the bridal improves performance and stability and sometimes sheeting angles
    but at the risk of adding forces to the hulls

    adding a bridal foil is a cheap, easy and light way to reinforce your hull strength and increase hull rigidity - which is a very beneficial thing to do, and for the cost... the insurance to your boat seems very worth it to me


    "So far, these 30+ year old boats are staying together."
    how many 5.7, 5.8. p19MX with bigger jibs and no foil have you seen survive?

    I've heard of boats failing without a foil
    nothing like hitting a big puff and a bow ripping off your boat a dozen miles offshore in the atlantic (happened to a friend of mine)


    If you look at all the modern, cp designed sailplans - the jib is lower than the boom

    https://vrsport.tv/wp-content/uploads/2017/10/A1378-1024x576.jpg

    Edchris177I'm not sure I understand the reasoning for this mod.
    I get that a foil changes the bridal loads to a "better" angle.
    So far, these 30+ year old boats are staying together.
    I really don't think they can be made to go any faster, or point any higher, at least not to any degree in real world sailing. The fact is, a skeg hull has reached it's potential, & we will always be beaten to booms & boards, given equal nuts behind the wheel.
    What is the point of lowering the jib any further?
    The jib mainly acts to accelerate air over the lee of the main. If the 5.7 is properly setup, the jib foot is level with the mains foot, giving the most help it can. Dropping it below the main gives some of that up.




    Edited by MN3 on Jan 08, 2018 - 10:07 AM.
  • MN3lowering the bridal improves performance and stability and sometimes sheeting angles
    but at the risk of adding forces to the hull

    I think tension at the bridle is only reduced, the effect of a bigger jib doesnt seem to add a lot, as opposed to the angle improvement



    Edited by Andinista on Jan 08, 2018 - 05:20 PM.
  • Quote"So far, these 30+ year old boats are staying together."
    how many 5.7, 5.8. p19MX with bigger jibs and no foil have you seen survive?

    Speaking only for myself, I don't see any upside in adding a larger jib to my 5.7. A few sq feet more dacron is not going to register much. Let's face it, when a team in a recent America Cup race cut their ENTIRE jib loose, (literally), their speed dropped by only a few mph. It wasn't like the jib gave them even a quarter of their speed.
    I get it that the cutting edge racers want,(need) even the tiniest bit extra. The pictured boat is also carrying a big kite, & that is another reason the jib is low, it attaches to the spin pole, & even then it's only a teensy bit lower.
    Sure there are broken bows, but look at the age & hard life many of these boat led. I'm not convinced a foil would have saved them, & there are plenty of instances of broken boats that use foils.
    I think a proper load analysis would show they are "better", but I doubt very much many conversions will be done.

    --
    Hobie 18 Magnum
    Dart 15
    Mystere 6.0XL Sold Was a handful solo
    Nacra 5.7
    Nacra 5.0
    Bombardier Invitation (Now officially DEAD)
    Various other Dock cluttering WaterCrap
    --
  • MN3
    "So far, these 30+ year old boats are staying together."
    how many 5.7, 5.8. p19MX with bigger jibs and no foil have you seen survive?

    I've heard of boats failing without a foil
    nothing like hitting a big puff and a bow ripping off your boat a dozen miles offshore in the atlantic (happened to a friend of mine)



    What you're saying has merit and is one of the reasons I make the recommendation not to rig a spinnaker/hooter on a boat that was not designed form the onset to carry one... I am under the opinion that there is not enough reinforcement in the way of stringers and bulkheads in the hulls to carry the load.

    I did a spinnaker set up on a 5.8 and this really put a strain on the hulls even with the NA bow foil. I started to experience a lot of gel coat spider cracks around the main beam area and a noticeable increase of bow flex when pushing the boat on a beam or broad reach..

    With regards to the purpose of the foil itself and only speaking from the experience with the 5.8 this was done to give the boat a lower footing jib for better "off wind" performance... it really had nothing to do with strength... thought some will argue it prevented the hulls from towing in when the main was sheeted too tight. The NA option I believe was first deployed in the late 80's a little before the spinnaker/hooter craze hit the beach cat community... I have sailed the 5.8 both pre-NA and NA set up... both with and without spinnakers... to me the best set up is a 5.8 that came from the factory with the NA option and square top sail. On a beam-broad reach... there is not better boat out there. Guess this is why this is one of the or popular classes in the Land of Oz.
  • Reduced, not eliminated - for sure
    but i THINK the force "direction" is also moved - no longer trying to tow inward but the forces moved into a more straight upward direction.

    the hulls have a lot more strength in this direction of force


    Andinista
    MN3lowering the bridal improves performance and stability and sometimes sheeting angles
    but at the risk of adding forces to the hull

    I think tension at the bridle is only reduced, the effect of a bigger jib doesnt seem to add a lot, as opposed to the angle improvementEdited by Andinista on Jan 08, 2018 - 05:20 PM.
  • QuoteSpeaking only for myself, I don't see any upside in adding a larger jib to my 5.7. A few sq feet more dacron is not going to register much. Let's face it, when a team in a recent America Cup race cut their ENTIRE jib loose, (literally), their speed dropped by only a few mph. It wasn't like the jib gave them even a quarter of their speed.


    most sailing Races are upwind downwind these days, and the spin is used on every downwind leg

    they used to have another gate for a reaching line
    having 20% more (jib) sail area makes a big difference when off the wind and down-wind (sans spin)

    I use both a 5.5 and 6.0 jib on my 5.5
    i gain speed with the bigger sail on a reach and downwind - it does nothing for me upwind



    Edited by MN3 on Jan 09, 2018 - 09:00 AM.
  • MN3Reduced, not eliminated - for sure
    but i THINK the force "direction" is also moved - no longer trying to tow inward but the forces moved into a more straight upward direction.

    the hulls have a lot more strength in this direction of force



    The force direction changes but its magnitude changes even more. Direction is simply the direction of the bridle.

    The following happens assuming there is no jib and looking from the front (simplifying a bit)..

    The vertical line is the vertical component of the force and the horizontal one is the inward force applied to the hulls. The hypotenuse is the tension of the bridle

    https://www.thebeachcats.com/gallery2/main.php?g2_view=core.DownloadItem&g2_itemId=129538&g2_serialNumber=3

    As the angle changes the inward force is increased or reduced but the vertical force is kept constant, because it equals half of the tension of the forestay

    You can see on the example that the inward force is more than doubled with such an angle change. And that it can be similar in magnitude to the vertical force.

    When you put a spinnaker it becomes more tricky, there lateral forces will increase the stay and the bridle tensions to compensate.

    I still tend to think that the most significant forces come from the main and mainsheet. The forestay angle multiplies that force because of its angle (now seen from the side). And the bridles amplify that effect again as explained.



    Edited by Andinista on Jan 09, 2018 - 03:43 PM.
  • i don't understand (at all)
    QuoteDirection is simply the direction of the bridle.
    huh?



    are the 2 graphs:
    1 with a foil above the bridal attachment tang
    1 without a foil

    or

    just 2 examples without a foil
    (showing how lowering the jib attachment increases the magnitude of the force)?



    Edited by MN3 on Jan 09, 2018 - 03:50 PM.
  • Quote still tend to think that the most significant forces come from the main and mainsheet.


    I take that out.. It all happen mostly through the shroud and forestay, jib and spi contribute the same way, one more than the other



    Edited by Andinista on Jan 09, 2018 - 10:01 PM.
  • MN3i don't understand (at all)
    QuoteDirection is simply the direction of the bridle.
    huh?


    are the 2 graphs:
    1 with a foil above the bridal attachment tang
    1 without a foil

    or

    just 2 examples without a foil
    (showing how lowering the jib attachment increases the magnitude of the force)?Edited by MN3 on Jan 09, 2018 - 03:50 PM.


    The graphs show forces with different bridle angles, the more vertical one could be the one with a foil. What matters is the angle, it would be the same forces with no foil and longer bridles. (what happens in the foil stays in the foil...)

    As shown in the graphs, the net force is the oblique one, decomposed in vertical and horizontal components. Say you apply a side force at the lower end of the stay. That would produce more tension in the oposite bridle and the stay. The other bridle would reduce its tension (the new force is doing part of the job). But forces are in all cases aligned with the wires. That’s how tension works. A rigid device rigidly attached would work differently, but it’s not the case.



    Edited by Andinista on Jan 09, 2018 - 09:49 PM.

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