Kyosho Twin Broken Cowl - Making a New Cowling w/Plaster of Paris
Posted: Mon May 01, 2017 11:25 pm
I have made Plaster of Paris molds for out of new kit plastic canopies and cowlings along with other parts that have been hard to get or get bashed constantly. I remember flying my small GWS Zero over the club airstrip and the canopy blew off out in the cornfield. I thought I would just order another one. To my surprise they were hard to get without buying another kit. I found one but the shipping was more than the part. The next day after spending time in the corn field up and down the rows I found it. I got lucky. Later I found a GWS Zero kit at an auction and I made molds for the original canopy and cowling.
This is not a hard thing to do but it can be frustrating parting the new parts out of the molds. So I show a few ways to help you get it out of the mold with some easier work. The first picture shows The P of P by DAP. A cut milk carton for the mold support. I have most items shown in the picture but there may be a few tools left out that came into the works as I went along, Cut open any large enough plastic bottle to use as a container for molding. The other tools are in the next few pictures as I go along. P of P is inexpensive and mixes easy with water. I mix it almost loose like a pancake batter. It sets up in about 20 minutes and hardens a little more overnight. The good cowling should be waxed with a good boat or car wax. I just tried some cooking vegetable spray this time but I will say the the wax seemed to work better with a few coats. I used more work time releasing the old cowl than I should have.
In the second picture you will see I mixed the P of P into the old plastic milk container. The cowling pat is forced down as it naturally wants to float. I just quickly grabbed a pair of bench batteries to weight it down to the point of P of P flowing over the edge. Weight can be lead sinkers bolts or whatever is at hand. Just do not let it touch bottom of the container. The plaster has to be deeper than the part. It was late so I left it for the next day.
In the next photo you see all the Plaster of Paris all set up and ready to get it out of the new mold.
Now you need to make the magic plastic tools to get it out of the plug. Look for an old bleach bottle or something similar and cut it open with scissors around the bottle to get the straight mid section out. Cut tapered plastic spoons of different widths. I start with the smaller ones that are not to sharp so it will not damage the mold Push it in slowly with some left and right motion and get as deep as you can. Remove it then move it over a little and repeat all the way around. I then used a larger one all around. I carefully used a flat needle nose pliers and pulled on the edge slowly and it popped out. You really can't pull to hard or it will break the original part. If it does not come out go around again with smaller plastic spoons to try to spread the walls deep as you can get them. Then try the needle pliers carefully again and it will eventually come out..
Now you will see how the mold looks with the part out. The blue was from the plastic spoon material and I cleaned it out. The hole drilled is for another another helpful way to extract the new epoxy glass part in the finish step should I have problems pulling it. It will be for air pressure blow out with an air gun. Fortunately it was not needed.
This is not a hard thing to do but it can be frustrating parting the new parts out of the molds. So I show a few ways to help you get it out of the mold with some easier work. The first picture shows The P of P by DAP. A cut milk carton for the mold support. I have most items shown in the picture but there may be a few tools left out that came into the works as I went along, Cut open any large enough plastic bottle to use as a container for molding. The other tools are in the next few pictures as I go along. P of P is inexpensive and mixes easy with water. I mix it almost loose like a pancake batter. It sets up in about 20 minutes and hardens a little more overnight. The good cowling should be waxed with a good boat or car wax. I just tried some cooking vegetable spray this time but I will say the the wax seemed to work better with a few coats. I used more work time releasing the old cowl than I should have.
In the second picture you will see I mixed the P of P into the old plastic milk container. The cowling pat is forced down as it naturally wants to float. I just quickly grabbed a pair of bench batteries to weight it down to the point of P of P flowing over the edge. Weight can be lead sinkers bolts or whatever is at hand. Just do not let it touch bottom of the container. The plaster has to be deeper than the part. It was late so I left it for the next day.
In the next photo you see all the Plaster of Paris all set up and ready to get it out of the new mold.
Now you need to make the magic plastic tools to get it out of the plug. Look for an old bleach bottle or something similar and cut it open with scissors around the bottle to get the straight mid section out. Cut tapered plastic spoons of different widths. I start with the smaller ones that are not to sharp so it will not damage the mold Push it in slowly with some left and right motion and get as deep as you can. Remove it then move it over a little and repeat all the way around. I then used a larger one all around. I carefully used a flat needle nose pliers and pulled on the edge slowly and it popped out. You really can't pull to hard or it will break the original part. If it does not come out go around again with smaller plastic spoons to try to spread the walls deep as you can get them. Then try the needle pliers carefully again and it will eventually come out..
Now you will see how the mold looks with the part out. The blue was from the plastic spoon material and I cleaned it out. The hole drilled is for another another helpful way to extract the new epoxy glass part in the finish step should I have problems pulling it. It will be for air pressure blow out with an air gun. Fortunately it was not needed.