12
Note! If the calculation gives a top extrusion length (D) that is shorter than 700 mm, the
calculation must be reworked by exchanging one of the 2400 mm extrusions with the uncut
1700 mm top extrusion. By doing so the top extrusion will be cut from a 2400 mm length
and its length will then exceed 700 mm. If the calculation gives a top extrusion length (D)
that exceedes 1700 mm, the top extrusion must be cut from one of the 2400 mm extrusions.
In this case the 1700 mm extrusion will not be used.
2.6 Calculating the length of the luff extrusion
The Furlex luff extrusion consists of a number of shorter sections. Starting from the bottom there is a 560 mm
luff extrusion connected to the drum unit and extending up to the sail feeder. Then, from the sail feeder and up
there are a number of full length luff extrusions (L=2400 mm) and finally there is a 1700 mm top extrusion that
has to be cut to length to suite the actual forestay length.
To find out the cutting length of the top extrusion (D) and the length of the top distance tube (E), start with the
length of the forestay wire (WL) that was calculated in table 2. Then follow the steps in table 3 below. On fixed
length forestays (incl. rod stays), verify WL by measuring the stay length from centre of eye to end of stud
(wire) or end of rod head.
Table 2. Calculation of top luff extrusion length and top distance tube length
Your
forestay
Example
(404TD 12mm)
With rigging screw 50%
extended
WL
Length of the new forestay wire (as per Table 2).
15700
A+B
930
N
Number of full length extrusions to be used:
N = ( WL - (A+B) )/2400
(15700-930
/2400=6.15
N=6
C
Total length of the number of full length extrusions (2400 mm) to be used:
C = N x 2400
6 x 2400 =
14400
D*
Length of top luff extrusion:
D = WL – (A+B) – C
15700-930-
14400=370
X
Fixed deduction:
300mm
300
E*
Length of the top distance tube:
E=D-X
370-300=70
Wire
Without rigging screw:
With rigging screw 50% extended:
Ø12: 1040mm
Ø14: 1085mm
Ø12: 930mm
Ø14: 980mm
Rod
Without rigging screw:
With rigging screw 50% extended:
-30: 1060mm
-40: 1080mm
-30: 965mm
-40: 970mm
