Ahoy Chall03 ...
Here''s what I see, see if I''m close. The winds are sort of light, around 3 to 6 mph. Your sails are sheeted close,(your main is up right?) things feel stable the boat if let got might want to fall off but you are correcting with rudder, which more less feels normal. You tack, the rudder responds slowly but positively and then after getting through the wind you sheet the jib and find the rudder can no longer hold the course. You''ve lost rudder effectiveness you''ve lost steerage. You''ve lost control. Your boat is now taking you for a ride. No problem happens to all of us from time to time for various reasons. Remember if you can''t steer with the rudder the only thing you have left are the sails.
Quickest solution out is let the jib out immediately and sheet the main this should stop lee helm and increace weather helm, the boat will pick up speed the rudder effectiveness will return and you regain control. Re-trim the sails and sail away on your new course.
The biggest tendency for a new sailor is to over sheet the sails, careful not to over sheet. Let them out ... let them breath
If in doubt let them out until they luff then sheet them in until they stop luffing. Anytime the wind changes or you change course the sails will need re-trimmed.
If the wind changes you can also change course and leave the sails where they are. A balanced boat will if allowed change course on its own. Stay loose on the tiller, feel the boat. Not getting zen on you here.
Just a note sailing in light air 5 mph or less isn''t easy, mistakes are exaggerated and things happen slowly. 5 to 10 is a bit better and anyone can sail from 10 to 20.
Your sails are out of balance, the jib has more pressure on it than the main. Like feathers on an arrow the jib is turning you down wind especially after the tack. This is called lee helm. What you need is a better balance to produce a nuetral helm or a little weather helm which gives the boat the tendency to turn into the wind.
Try this or have you noticed? If the main is sheeted in and the jib is out the boat will tend to turn up wind or head up.
And if the jib is in and the main is out the boat will fall off or turn away from the wind.
Weather helm is the boats tendency to head up, lee helm is the boats tendency to fall off. Heading up depowers or puts on the brakes and falling off powers up the boat or puts on the gas.
Work with sail trim and sail balance and you''ll find things will settle down and behave the way you like.
There is a slight possibility your rigging is out of adjustment which could aggravate this situation and older tired sails make things a little hard at times too but you can cross that bridge when you come to it.
I highly recommend Sail & Rig Tuning by Ivan Dedekam. If I were to only have one book on sail trim and tuning this would be it.
Fair winds Eric Jon