Also, when you glue in the motor mount with glue only on the front ring and the back ring without glue, you glue on your fins. By glueing the fins on with the aft ring loosely in place, this will secure the motor mount tube concentrically. THEN you pull out the aft ring to do your fin/motor mount fillets. Be sure that no fin glue gets on the aft ring or you can't get it out! Watch this guy's video starting about 19:22 for a good demo. th-cam.com/video/Xtr3758PvzA/w-d-xo.html
Also, when you glue in the motor mount with glue only on the front ring and the back ring without glue, you glue on your fins. By glueing the fins on with the aft ring loosely in place, this will secure the motor mount tube concentrically. THEN you pull out the aft ring to do your fin/motor mount fillets. Be sure that no fin glue gets on the aft ring or you can't get it out! Watch this guy's video starting about 19:22 for a good demo. th-cam.com/video/Xtr3758PvzA/w-d-xo.html