I'll give you an example of my last hunt.My initial patrol orders were to patrol grid BF17 for 24hrs (a waste of time I know),which covers roughly the western approaches into Britain,just south of Ireland.After 24 hrs I decided to patrol my own sector,and decided I needed to find the main lanes a bit further to the west away from Britain and in deeper water,directly south of the south western tip of Ireland,this was and IS a major trade hub for shipping coming from Canada and USA.
First,I decided to head for BF14 and when I reached the southern edge of the grid I would head north onto the northern edge of BF11 (roughly a 200km patrol corridor) moving submerged for most of the patrol (roughly 6-7 hours submerged) at 4kts.Moving submerged at about 30m you can pick distant contacts up a lot further than if you were relying on your watch crew.When the batteries had drained to 10% I surfaced and ran for about 4hrs or so at ahead standard while charging the batteries,which expended approx 200km or so of fuel,from a total of well over half the tank to start with.I had enough fuel at this rate to cover the short surface run for well over a week,and possibly more!.I also recorded how much fuel I would need for the return journey back to Wilhelmshaven,approx 2000km worth taking the short cut through the channel (very risky,but I made it through at the beginning of the patrol,but this will be the last time as patrols are increasing in that area now).
After heading into the northern sector of BF11 I would again head south back into BF14 submerged,and recharged as neccessary when the batteries had drained to 10%.
In this time I spent almost 2 weeks in the area and managed to sink 6 ships for a total of just under 37000 tonnes,including a very juicy whale factory ship for 12000 tonnes!.
Thats the way I do it,pick an area that you expect to have high traffic (ideally at chokepoints and not too far from your initial 24hr patrol orders),usually this may cover one or more grid squares to patrol,then stick to your plan.And in my case I would only attack incoming ships,and ignore the outgoing,as my intention was to cut off supplies HEADING for Britain,and not going back to Canada.This adds to the realism factor.I am now about to enter the channel again after spending 17 days in total at sea with 2 stern torpedoes left and 150rds of HE ammo.
You will realise the greatest threat from this method of patrolling is fuel,but if you work out how mank kms you cover surfaced while recharging for a 24hr period,deduct it from your current total of fuel left,then work out the surface totals for a week,and maybe two,you should have enough fuel to cover it,if your fuel notes and calculations are correct.It is better to dynamically patrol an area than to remain in one spot and hoping for traffic to come to you,the oceans are too vast for that approach.But once you are certain you have found a lane frequented by many ships you can then afford to hang around just off the track and wait for them to arrive
You will certainly need patience,persistence,foresight and luck to patrol like this,but its very rewarding when it works.
Good hunting!
