Looking over my crossbars/hulls and the attachment arrangement, I discovered something that makes absolutely no sense. My crossbars attach to the hull with two studs which stick up from the bottom of each crossbar craddle:



The through holes in the crossbar are larger in diameter than the studs. The outermost through hole is larger than the inner through hole:



When I noticed that the through holes were larger I thought well, they must have done that to make it easier to assemble and the hull alignment (as in parallel and square) wouldn't be an issue as when the tramp is tightened (with the nuts on these studs just snug) the studs will find the innermost position in the crossbar's through holes, both front and back, thus the boat will be in proper alignment.

When I disassembled the rear crossbar I found a different type of crossbar casting with a centering boss:



So, with the centering type of crossbar casting on the rear crossbar and the non-centering on the front crossbar in theory the hulls would end up with toe in.

Can someone please explain, thoughts, ideas, how to align a Nacra? I only see one type of casting on Murrays which appears to be bossless. I'm going to race this boat locally and I fought for years to keep the hulls aligned on the Hobie 16's I've owned, constantly checking diagnals and tightening/loosening the tramp. From that I know first hand how much mis-aligned hulls can slow you down.



Edited by leeboweffect on Aug 06, 2015 - 09:43 AM.

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Hobie 16 (3 formerly)
MacGregor 25 (formerly)
Chrysler Dagger 14 (formerly)
NACRA 5.0 (currently)
High Point, NC
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Lee, I have the same year 5.0 as you. You need the correct castings to secure your front crossbar properly. When assembling these it is really helpful to have someone assist in pulling the hulls outward to get that
boss to fit down securely in the hole. (The tramp is already on and a tight fit.) Good luck.

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Mark Hirte
Nacra 5.0 1983 - (1st cat)
Deerfield, Il
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Thanks Mark. Where can I get them?

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Hobie 16 (3 formerly)
MacGregor 25 (formerly)
Chrysler Dagger 14 (formerly)
NACRA 5.0 (currently)
High Point, NC
--

I see that the ones available (Murray's) have no boss to fit in the crossbar hole. I'd recommend that you give Pete Begle a call - his number is on items on the parts page. Maybe someone here will have a lead on the correct part. It's probably sailed a long time with the wrong parts.

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Mark Hirte
Nacra 5.0 1983 - (1st cat)
Deerfield, Il
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I'm not familiar with your "stud" setup, both mine just use regular chocks in the front beam only.
The holes in the beam are larger than the studs as it is not a precision fit, bigger holes allow for some tolerance in manufacture.
However, do your hulls have those little metal straps,(about 2-3" long), on the inside of the hull, just below where the beam sits?
Can't quite see far enough down in your photo.
If you have those tangs, then there should be a small fitting on the underside of the beam. Actually, it is the same "fork" that you hook the mainsail halyard into. When setting up the boat, those "forks" should be butted up against the metal strip on the hull.
Both Nacra manuals make reference to them. If yours is set up that way, that is what prevents the hulls from moving inwards.
IIRC your front width ends up appx 1/4" bigger than the rear,(measure from centre seam to centre seam).
When the rig & wind loads are applied, the bows will be pulled inwards, equaling the dimensions.

--
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
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Quote

IIRC your front width ends up appx 1/4" bigger than the rear,(measure from centre seam to centre seam).
When the rig & wind loads are applied, the bows will be pulled inwards, equaling the dimensions.

Interesting.

--
Tom
Hobie Getaway, Nacra 5.5, Hobie Tiger
Wish list: A-cat classic, F16 Viper!
Northern California
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Thanks Ed.

Edchris177

However, do your hulls have those little metal straps,(about 2-3" long), on the inside of the hull, just below where the beam sits?
Can't quite see far enough down in your photo.

I think this is what you're referring to:



My boat doesn't use that arrangement. It looks like this:



--
Hobie 16 (3 formerly)
MacGregor 25 (formerly)
Chrysler Dagger 14 (formerly)
NACRA 5.0 (currently)
High Point, NC
--