Topic : Rig tensions

What is the best rig tension (in pounds) for the lowers and shrouds at zero position with a super spars carbon mast.

Posted: 06/11/2007 17:41:22
By: Jon Steward
There are no standard numbers. While sailing the leeward shroud should be "just" tight. Lowers should firmly add support before the kicker is applied.

Posted: 06/11/2007 17:55:31
By: Chris M
Thanks Chris. The wires seem to give a good twang and no leeward sag at 250/300 pounds but feels too much above 300. Do you try to keep the same tension throughout lowers and shrouds. I do understand that more tension is required as the wind picks up. Do you know the tensions that are put on the wires in force 5-6.

Posted: 06/11/2007 21:41:25
By: Jon
don't know never measured them.

Posted: 07/11/2007 07:11:29
By: Chris M
fair enough. maybe there is little poimt to this!

Posted: 07/11/2007 07:18:41
By: Jon
It depends what rig tension guage you use.  The Loos and Superspar seem to give different readings.  My Superspar guage tells me that in really windy conditions I have got about 400 lbs - in light winds250 - 300 (Winder boat, Chipstow rig).  Never measured the lowers - follow Chris's advice).  Hope this helps

Posted: 07/11/2007 08:08:07
By: JC
I will test the rig tension at fully raked to see what the maximum tension is that I can produce. From what you say it should be 400 pounds +. I suppose I should consult mast and sail makers for exact requirements. I was hoping to find out what rocketeers had discovered in their experiences.

Posted: 07/11/2007 19:18:42
By: Jon
Due to the dynamic nature, and general twiddling of the rocketeers rig, adjustments to rake are made whilst sailing on each leg of the course and as a consequence rig tension gets adjusted dynamiclly, this is different to fixed rake boats (e.g. GP14, Ents etc) where 'fast' rig tension is set up at launch time and stays the same durig the race.  The basic principal of setting up on the beat and let the rig tension drop until you can visible see the leeward shroud sag, and then tighten up gently to take up the slack is a good starting point. Experince says (at least to me), if you are going slowly (relative to those around you) in very light stuff try reducing the rig tension (or put your crew on a diet, thats less quick to adjust), again this is a dynamic excercise

Posted: 07/11/2007 20:57:45
By: Alan F
I would suggest in light airs you would require more rig tension than you may think. This will give you a little more mast bend , flattening the mainsail

Posted: 08/11/2007 10:19:23
By: Racer
It has been suggested to me that in very light airs, when it is difficult to get laminar flow working over the sails, that some rake is useful to help open the leech. As soon as laminar flow is established, mast to upright seems to be the trick.

My preference is for more rig tension as well.


Posted: 08/11/2007 12:55:11
By: Measurement Man
I think that due to the subtle shiftyness of wind in very light conditions especially inland that it would be very hard once established to maintatain enough airflow to rake the mast to a horizontal position. This action in itself could shake the wind away. From my laser sailing experience light winds require a tight rig using only a small ammount of kicker flattening the leech with the main with some windward heal, balance is the key.

Posted: 08/11/2007 20:14:35
By: Jon
I know that raking the mast to horizontal is very slow in any condition!

Posted: 08/11/2007 20:42:23
By: Alan F
It also can break the gooseneck fitting!

Posted: 08/11/2007 20:43:00
By: Alan F
you get the same open leach effect buy using a very small amount of cunningham,
and when its moving again let it off.

Posted: 09/11/2007 11:05:07
By: daveF
This is much misused in sailing.
Laminar flow, sometimes known as streamline flow, occurs when a fluid flows in
parallel layers, with no disruption between the layers. In fluid dynamics,
laminar flow is a flow regime characterized by high momentum diffusion, low
momentum convection, pressure and velocity independent from time. It is the
opposite of turbulent flow. In nonscientific terms laminar flow is "smooth,"
while turbulent flow is "rough."
The dimensionless Reynolds number is an important parameter in the equations
that describe whether flow conditions lead to laminar or turbulent flow.
Reynolds numbers of less than 2100 are generally considered to be of a laminar
type. When the Reynolds number is much less than 1, Creeping motion or Stokes
flow occurs. This is an extreme case of laminar flow where viscous (friction)
effects are much greater than inertial forces.
For example, consider the flow of air over an airplane wing. The boundary layer
is a very thin sheet of air lying over the surface of the wing (and all other
surfaces of the airplane). Because air has viscosity, this layer of air tends to
adhere to the wing. As the wing moves forward through the air, the boundary
layer at first flows smoothly over the streamlined shape of the airfoil. Here
the flow is called laminar and the boundary layer is a laminar layer.
For a practical demonstration of laminar and non-laminar flow, one can observe
the smoke rising off a cigarette in a place where there is no breeze. The smoke
from the cigarette will rise vertically and smoothly for some distance (laminar
flow) and then will start undulating into a turbulent, nonlaminar flow.

Posted: 09/11/2007 13:42:01
By: Laminar Flow
Not being an expert, but I think you are right, it isn't an issue of laminar airflow, but of airflow detaching due to a deep chord (too much of a curve to follow) hence creating turbulence and loss of power, hence flatenning the sails keeps the air flow attached.

Jon, I still maintain a horizontal mast is not the correct positon :-)

Posted: 09/11/2007 16:58:20
By: Alan F
I would like to find the rig tensions at a start point (zero position)for both shrouds and lowers, assuming that a horizontal mast is a good point to start. I would like to know what tension people have attained at various raked positions. It is interesting to know about light wind effets on the sails. Knowing the rig tensions would help towards acheiving the best raked positions for all conditions.

Posted: 09/11/2007 18:57:54
By: Jon Steward
Horizontal is not the best starting point for a mast. Try Vertical!

Posted: 09/11/2007 20:22:04
By: Alan F
sorry been a long day! Although i did manage a horizontal in my laser this afternoon.

Posted: 09/11/2007 21:23:58
By: Jon
arent we an expert bunch.  I have not thought about Renolds numbers since studying mine ventilation in the last century.

Posted: 10/11/2007 10:55:17


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