Don't just punch out the rings, the hold down "tics" should be cut with a hobby knife. The small vent holes are also cut and removed.
It's just me - I like to use a sharpened pencil or dowel to clean up the holes.
Leave the sharpened dowel rough, set it in a hole and turn. This rounds out the hole and cleans up some of the charring.
TIP: Instead of sliding the engine block into a ring of glue from the bottom -
The yellow spacer tube is marked at 1/2" and taped in place at the bottom.
Slide the engine block in from the top and down onto the top edge of the yellow tube.
Apply a glue fillet using a Q-tip from the top along the inside edge of the engine block and tube. On a short engine tube like this, it's easier and cleaner to glue the block in from the top. Set it in place, add the fillet from the top.
The rear notched centering ring is glued 1" from the low end.
The black retainer ring is slid down from the top and glued against the lower ring.
The inset picture is the front view -
TIP: That black retainer ring is against the upper ring to help install it perpendicular to the tube. Apply a glue fillet to the ring/tube top joint, then slide and glue the ring against the lower ring. Apply a fillet on the lower side of the ring/tube joint.
In the instructions The upper vented ring is glued 3 1/4" from the low end. I set it a little lower, over the forward end of the engine hook bend.
I like that you use the retainer ring to get the upper centering ring on straight. I do stuff like that when I can. I know it may not be critical, but I feel that it's neater.
ReplyDeleteRegarding filleting the top of the engine block ring, I sometimes wonder if motors get stuck because I've glued that ring in by pushing it down into the glue, and that the heat of the motor melts the dried glue or something. I have a few rockets where I always have this problem - mostly earlier builds. I mean to test that some time and see if there's something to it.
Hi Daniel,
DeleteOn gluing the engine block from the top -
You are right, sliding the spacer tube and engine block through glue from the bottom can be a problem. If glue is left in the tube next to a just launched HOT engine, the glue can melt and "glue" the engine in place!
Fred Schector recommends pulling out a friction fitted engine immediately when the rocket is recovered. While most things expand when hot, the now hollow engine actually get a little smaller in diameter. That and the tape around the casing is warm.
I'll do a follow up post and get into more detail.
Daniel,
DeleteThanks for the reminder - I went into a little more detail as to why the retainer ring was against the upper centering ring.