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MCS / IMCS MAST MEASUREMENT SYSTEMS
MCS
The MCS (Mast Check System) allows comparison of stiffness and flex between masts by measuring the deflection under a fixed load at points along the mast. As the stiffness of a cylindrical mast section is proportional to the fourth power of the diameter, slight variations in taper,
thickness and materials have a great effect on the mast's behavior. Since windsurfing masts are developed by individual manufacturers in a variety of stiffness and flex, the MCS system is useful in determining mast / sail compatibility. In the MCS system, the 'character' of the mast is described by a dimensionless stiffness coefficient and base - tip flex percentages.
How to Make an MCS Measurement
1) Place the mast on two low-friction pins located 5cm in from each end.
2) Determine the mid-point and the 1/4 points between the pins.
3) Hang a weight of 30 kilos (66 pounds) at the mid point and measure the deflection at the mid and 1/4 points.
Hints:
1) You may want to use a small (2-5 pound) weight to preload the mast slightly and eliminate slop in the joint or other minor variations. This weight must be placed in the middle and remain in place for all measurements.
2) To determine the deflections, take differences from the undeflected (no 30 kilos) and deflected (with 30 kilos) positions at the top edge of the mast.
3) Strap the butt-end to it's pin while still allowing for rotation to prevent the mast from moving back and forth on the pins and possibly falling off.
To determine the stiffness and flex, enter the data into the following formulas:
MCS = (Length x 10 ) / Mid def(cm)
Base % = (1/4 def ) / Mid def
Tip % = (3/4 def) / Mid def
Mast Categories
Under the MCS system most popular windsurfing masts found in the marketplace can be placed into three basic categories:
Constant Curve
Any mast with a base - tip percent of mid-point difference in the 10% - 14% range is considered to be a 'constant curve' mast. The 'classic' definition of a constant curve mast is a mast having a 76% tip defelection percentage and a 64% base deflection percentage. These masts are often labeled as 12% constant curve masts.
Flex Top
Any mast with a base - tip percent of mid-point difference in the 18% - 22% range is considered to be a 'flex top' mast. The 'classic' definition of a flex top mast is a mast having a 82% tip defelection percentage and a 62% base deflection percentage. These masts are often labeled as 20% flex top masts.
Combi Curve
Any mast with a base - tip percent of mid-point difference in the 14% - 18% range is considered to be a 'combi curve' mast. The 'classic' definition of a combi curve mast is a mast having a 79% tip defelection percentage and a 63% base deflection percentage. These masts are often labeled as 16% combi curve masts.
IMCS (INDEXED MAST CHECK SYSTEM)
Windsurfing masts are developed by individual manufacturers in a variety of lengths as well as stiffnesses. As the defection under load varies with length it is necessary to account for the length factor when selecting a mast. The IMCS system 'normalizes' the MCS stiffness coefficients to a standard length mast which then allows direct comparison of masts. Currently, IMCS is the standard by which all windsurfing masts are categorized. Once an MCS measurement is made, the IMCS is determined as follows:
Converting MCS to IMCS
IMCS = (MCS x (Length)2) / (460)2
The chart below gives the conversion for most popular masts currently in existence.
Length - MCS - IMCS
400 - 25 - 18,9
430 - 25 - 21,8
430 - 27 - 23,6
460 - 25 - 25,0
460 - 27 - 27,0
480 - 27 - 29,4
480 - 30 - 32,7
500 - 28 - 33,1
500 - 30 - 35,4
