I need to fabricate a tack fitting for an asymetrical spinnaker out on
the bow sprit forward of the stemhead. What I need is a design load so
I can choose a pin size and then work the other dimensions back from
that. Does anyone know how to predict the tack load for a cruising
chute? Would it be the same as the halyard load?

--
Glenn Ashmore

I'm building a 45' cutter in strip/composite. Watch my progress (or lack
there of) at: http://www.rutuonline.com
Shameless Commercial Division: http://www.spade-anchor-us.com

Glenn,
I once asked Shore Sails in RI that question, and was told that they didn't
really know..... In the end I calculated what load the tack ring could take,
and used that plus 50% as a basis. Size the tack line to be the first thing to
give, for a little extra piece of mind.
As a guide, I have used 2500lbs on a 40-footer, and 5000 lbs on an Open 60.
Tack fittings still in place. ;-)

Steve

That is the range I was expecting. I am going to aim at 3,000 lb. with
a 4:1 safety factor. That will match the 7/16" Warpspeed halyard pretty
well.

The next question is what type of fitting should it be? I am thinking
either to mill a piece of 1/2" x 2" 316 and drilling for a 1/2" pin for
a shackle or bending up a ring out of 1/2" rod.

Stephen Baker wrote:

Glenn,
I once asked Shore Sails in RI that question, and was told that they didn't
really know..... In the end I calculated what load the tack ring could take,
and used that plus 50% as a basis. Size the tack line to be the first thing to
give, for a little extra piece of mind.
As a guide, I have used 2500lbs on a 40-footer, and 5000 lbs on an Open 60.
Tack fittings still in place. ;-)

Steve

--
Glenn Ashmore

I'm building a 45' cutter in strip/composite. Watch my progress (or lack
there of) at: http://www.rutuonline.com
Shameless Commercial Division: http://www.spade-anchor-us.com

Glenn says:

The next question is what type of fitting should it be?

I've always liked the simplicity of a bolt through the end, on centre, with a
tang attached and free-rotating, long enough to attach a block to other end of
that will be above the pole when under tension (any ideas for improving the
grammar there gratefully received)
It all depends on the construction of the pole. Whatever, the end fitting must
be free to rotate so as not to induce torque into the tube. Simple is
better....

Steve

The load is about the same. The major load is when the
shock load comes from a set, or a broach. I have been using standard
padeyes for foreguys and snoutlines.

I have used a bent 1/2 SS rod for a 43 footer with no problems for several
years.
It is bent, then a die run on both ends.

"Glenn Ashmore" wrote in message
news:9%6yb.71994$xV6.41833@lakeread04...
I need to fabricate a tack fitting for an asymetrical spinnaker out on
the bow sprit forward of the stemhead. What I need is a design load so
I can choose a pin size and then work the other dimensions back from
that. Does anyone know how to predict the tack load for a cruising
chute? Would it be the same as the halyard load?

--
Glenn Ashmore

I'm building a 45' cutter in strip/composite. Watch my progress (or lack
there of) at: http://www.rutuonline.com
Shameless Commercial Division: http://www.spade-anchor-us.com

Make that a 7/16" rod.

"Glenn Ashmore" wrote in message
news:9%6yb.71994$xV6.41833@lakeread04...
I need to fabricate a tack fitting for an asymetrical spinnaker out on
the bow sprit forward of the stemhead. What I need is a design load so
I can choose a pin size and then work the other dimensions back from
that. Does anyone know how to predict the tack load for a cruising
chute? Would it be the same as the halyard load?

--
Glenn Ashmore

I'm building a 45' cutter in strip/composite. Watch my progress (or lack
there of) at: http://www.rutuonline.com
Shameless Commercial Division: http://www.spade-anchor-us.com