Trouble with Grappling hook

So I plan to create a grapple hook and have. although i do have momentum it cant be applied upwards but instead i stop if heading up and fall while continuing in the horizontal direction. anyone able to point out some tips or help

Code (csharp):

1.  
2. using System.Collections;
3. using System.Collections.Generic;
4. using UnityEngine;
5. using UnityStandardAssets.Characters.FirstPerson;
6.  
7. public class Hool : MonoBehaviour
8. {
9.     public Transform cam;
10.     private RaycastHit hit;
11.     private Rigidbody rb;
12.     public bool attached = false;
13.     public float momentum;
14.     public float speed;
15.     private float step;
16.     public RigidbodyFirstPersonController cc;
17.     LineRenderer line;
18.     public GameObject m_endorb;
19.     public float maxDistance;
20.     public GameObject shootfrom;
21.  
22.     bool groundedLastFrame;
23.  
24.     // Use this for initialization
25.     void Start()
26.     {
27.         rb = GetComponent <Rigidbody>();
28.         line = GetComponent<LineRenderer>();
29.  
30.        
31.     }
32.  
33.     // Update is called once per frame
34.     void Update()
35.     {
36.         if (Input.GetButtonDown("Fire2"))
37.         {
38.            
39.             if (Physics.Raycast(cam.position, cam.forward, out hit, maxDistance))
40.             {
41.                 if (hit.transform.gameObject.tag == "Gyes")
42.                 {
43.                         attached = true;
44.                         cc.mouseLook.XSensitivity = 5;
45.                         cc.mouseLook.YSensitivity = 5;
46.  
47.                         GameObject cube2Instance;
48.                         cube2Instance = Instantiate(m_endorb, hit.point, Quaternion.identity);
49.                         rb.isKinematic = true;
50.                 }
51.             }
52.         }
53.         if (Input.GetButtonUp("Fire2"))
54.         {
55.             if (hit.transform.gameObject.tag == "Gyes")
56.             {
57.                     cc.mouseLook.XSensitivity = 5;
58.                     cc.mouseLook.YSensitivity = 5;
59.                     attached = false;
60.                     rb.isKinematic = false;
61.                     rb.velocity = transform.forward * momentum;
62.             }
63.         }
64.  
65.         line.enabled = attached;
66.         if (attached)
67.         {
68.             momentum += Time.deltaTime * speed * 1.25f;
69.             step = momentum * Time.deltaTime;
70.             transform.position = Vector3.MoveTowards(transform.position, hit.point, step);
71.             line.SetPosition(0, shootfrom.transform.position);
72.             line.SetPosition(1, hit.point);
73.         }
74.         if (!attached && momentum >= 0)
75.         {
76.             momentum -= Time.deltaTime * 5;
77.             step = 0;
78.         }
79.  
80.         // if we've just landed this frame, zero momentum
81.         if (!groundedLastFrame && cc.Grounded && momentum >= 0)
82.         {
83.             momentum = 0;
84.             step = 0;
85.         }
86.  
87.         groundedLastFrame = cc.Grounded;
88.     }
89. }
90.  

 

What kind of behaviour are you looking for? A direct-pull in a straight line towards the hit point, or more of a swinging motion? Looking at your code it appears you're going for the straight-line pull.

I can't immediately see why you're dropping off the hook, but first of all I'd recommend moving your physics code into FixedUpdate rather than Update, as that's where rigid-body manipulating code is meant to be (In order to stay in sync with the physics engine).