Rudder sizes

Morning all making a new lifting rudder just wondering on the general length and width of the rudder should be for the seahawk I feel mine might be a bit small, cheers.

I've got no accurate measurements for the standard rudder, but the information on the site here:
https://www.seahawk17.org.uk/boat-description-keel.php#rudder
and here:
https://www.seahawk17.org.uk/owners-custom-sailing-rudder.php#feckless

should help. At least the pintles should be a fixed distance apart for you to get reasonable assurance on the standard size.  

Cheers Greg mine goes around 70cm under water right now

My new rudder is 45 inches from the top of the pintle