This paper gives the results of study on the form effects on viscous resistance of full ships. The form effects are divided into two components, one is the effect on frictional resistance and the other is on viscous pressure resistance. An investigation is made about the characteristics of the two components and it is shown that the main part of the form effect is on the pressure resistance. On the basis of this result a practical formula for estimating the form factor of full ships has been developed. A comparison of the calculated form factors with those by experiments shows a good agreement in a wide range of the ship form parameters. The formula is compared with several published ones.
