I acquired this boat, dated from the 1970s, at a car boot sail for £7. She wasn't in too bad a state but needed refurbishment, a new suit of sails (the originals being 'ripe') and re-rigging (there was none!). The keel was cracked at the join with the hull and the two halves were separating plus the lead ballast was missing. it also had no fin forward of the rudder leaving the rudder exposed to knocks.
She had never been Radio Controlled and while the sailing fittings were salvageable the oval cabin windows were either missing, broken or the 'glass' badly misted. There were no other deck fittings.
Before starting serious work I made a cradle and researched the model on the internet to get an idea of the 'spirit' of the model and formulate my plans. I managed to find Images of the boxed kit and its plans and determined that mine was an early Collie, not a Collie II that came later.
The first job was to strip everything off, repair the keel and add the fin in front of the rudder. Epoxy resin (bound with masking tape until fully hardened) was used to stabilize the cracks and strengthen the joint. Car body filler was then added to further strengthen and blend the join prior to sanding and fairing into the hull.

Looking at comments on the internet I noted that the original rudder was said to be a little small and would benefit from being changed. First, lengthening it to give better bite when heeling. Second, adding a fin in line with the keel to give some protection from knocks and also to help avoid picking up weed by giving the fin a sweep backwards to push weed downward and under the rudder. Finally by projecting the rudder extension forward and fairing it into the line of the fin an element of (counter)balance could be achieved to reduce servo strain.
The rudder was replaced with wood, shaped and keyed to a new rudder shaft. The fin, also of wood, was then added by pinning plus epoxy and then the fairing process repeated. The hull was then stripped back, smoothed and primed.
Next a new keel ballast weight was shaped in wood, then used as a plug to make and mould and cast (in lead) a copy with embedded pins to fit into holes drilled up through the keel. The new ballast was fitted, epoxied in place and faired in as before. With this the hull was complete and could be painted.

Part 3
While the hull was watertight it didn't feel very rigid and I was concerned that the hull material might be brittle with age. I therefore decided to fit fore and aft frames in the hull. Using templates made to the outer hull form and reduced by the hull thickness; plywood frames were cut out with lightening/access holes and epoxied in place.
Following this attention was given to the RC gear ' primarily the working/fitting of the servos. As only a simple extended arm high torque servo was intended for sail control the geometry was simple enough. Tubes were fitted in the deck for the sheet control and run back into the hull to the servo positions (see photo). For durability the sheet outlets on deck were made of brass tubing with plastic tubing inside. The RX and battery pack were boxed in case of water ingress (although, so far, this has proved unnecessary 😀 ).
The original deck (plywood with printed planking) was in good condition and was sanded down and given a number of coats of French polish until the deck had a pleasing smooth and gloss finish.

The final construction job on the hull was to fit the cabin/cockpit sides which had been broken off. With the basic hull completed many of the original fittings were reattached after cleaning. The original gooseneck could not be salvaged however and a new brass one was fitted.
A new suite of sails was made using the original, very ripe ones, as a pattern. The material came from a very cheap children tent that had seen better days. The mainsail was a success but the foresail needs to be remade as on the water It Isn't fully effective and doesn't have a good shape.
The rigging was made to allow the boat to be de-rigged quickly. This Is satisfactory but would benefit from the stays being permanently attached to, rather than simply hooked Into, the eyes screwed Into the deck as they get tangled In transit.
On the water my Collie has proved to be a good sailor In most weather and great fun to sail. She Isn't the fastest around being easily beaten by some modern RTR models ' the difference Is that I've made this one mine and we'll be sailing together for some time yet!