I know that there are a few methods for the difficult and sometimes long process of getting good strong fillets for fin to motor mount and inside the airframe without using glass carbon fiber etc. Some people use a dowel while others pour the epoxy from the aft end and tilt the rocket which allows the epoxy to run down the joint. I on the other hand have found another way that some of you may find unique and even easier.
The materials you will need other than the obvious will be (2) 20 cc catheter syringes, a piece of automotive vacuum hose (length will depend) and, Epoxy thinner. Make sure the hose fits tightly over the small end of the syringe. Cut the hose so it will reach the forward end of the fin but don’t connect it to the syringe yet. You can get the syringes at any medical supply facility. I also prefer to use 30 minute epoxy.
First, tac all the fins to the motor mount by which ever means one may be accustom to. I like using CA myself. Next mix the appropriate amount of epoxy to do one side of two fins. Suck or pour the epoxy into the syringe. If you choose to pour the epoxy in then you will have to plug the end with your finger so the epoxy won’t run out and make a mess. After that you will have to insert the plunger part way in and turn the syringe upside down allowing the epoxy to run towards the plunger and then squeeze the plunger forward to get the air space out. Now connect the piece of hose you cut to the end of the syringe. With the rocket laying flat, insert the hose to the forward end of the fin and dispense the epoxy while pulling back to the aft end. Take your time to ensure that you get the desired amount of epoxy on the joint. That’s it. Let it sit and set up before you do the next set. At this time you can wipe of any epoxy that may have gotten on the aft end of the airframe. But if you did it right and took your time you don’t have to worry about that. Clean the hose and syringe buy flushing the epoxy thinner through. Do this several times to make sure its clean and reuse it for the rest of the fins.
Submitted by: Scott Regan