Rotation Speed

How can I set how fast a ship turns with rotation? say maybe degrees per sec or something? Heres the current code…

using UnityEngine;
using System.Collections;

public class ShipControl : MonoBehaviour
{
	public Transform ship;
	float flyingSpeed = 0;
	float turnSpeed = 50.0f;
	
	void Update ()
	{
		//Accelerate the ship using the thrust key.
		if(Input.GetKeyDown("e"))
		{
			if(flyingSpeed == 0)
			{
				flyingSpeed = 2.5f;
			}
				else if(flyingSpeed == 2.5f)
				{
					flyingSpeed = 5f;
				}
				else if(flyingSpeed == 5f)
				{
					flyingSpeed = 7.5f;
				}
				else if(flyingSpeed == 7.5f)
				{
					flyingSpeed = 10f;
				}
		}
		
		//Decelerate the ship using the thrust button.
		if(Input.GetKeyDown("q"))
		{
			if(flyingSpeed == 10f)
			{
				flyingSpeed = 7.5f;
			}
				else if(flyingSpeed == 7.5f)
				{
					flyingSpeed = 5f;
				}
				else if(flyingSpeed == 5f)
				{
					flyingSpeed = 2.5f;
				}
				else if(flyingSpeed == 2.5f)
				{
					flyingSpeed = 0;
				}
					else
					{
						flyingSpeed = 0;
					}
		}
		
		if(Input.GetKey("w"))
		{
			ship.transform.Rotate(20.0f * Time.deltaTime, 0.0f, 0.0f);
		}
		
		if(Input.GetKey("s"))
		{
			ship.transform.Rotate(-20.0f * Time.deltaTime, 0.0f, 0.0f);
		}
		
		if(Input.GetKey("d"))
		{
      		ship.transform.Rotate(0.0f, turnSpeed * Time.deltaTime, 0.0f * Time.deltaTime, Space.World); //and then turn the plane
   		}
		
		if(Input.GetKey("a"))
		{
      		ship.transform.Rotate(0.0f, -turnSpeed * Time.deltaTime, 0.0f * Time.deltaTime, Space.World); //and then turn the plane
   		}
		
		ship.transform.Translate(0,-flyingSpeed * Time.deltaTime,0);//move the ship
	}
}

Here’s an example:

public class SpinningBox : MonoBehaviour {

	public float yawDegreesPerSecond = 10.0f;

	// Update is called once per frame
	void Update () {
		Vector3 localEulers = transform.localEulerAngles;
		localEulers.y += yawDegreesPerSecond * Time.deltaTime;
		transform.localEulerAngles = localEulers;
	}
}