Mini Darkstar Centering Rings

Finally hoping to get my Wildman Mini Darkstar build underway.

I had a thought and was interested in opinions.

If I'm reading the instructions correctly (which are written for the Minis and other smaller rockets), the recommendation is (I'm omitting the harness stuff as it's not relevant to my question; also I'm summarizing, but you get the point)
1. Install top CR onto Mmt. Epoxy and let dry.
2. Temporarily install bottom CR onto mmt with scotch tape around it for easy removal.
3. Slide mmt into rocket. Install fins and glue.
4. Remove rear CR and make internal fillets. (The epoxy also secures the top CR from inside)
5. Replace rear CR, only glue it in this time (or just fill everything with foam and be done with it)

The problem with this method in my build is that the gap between the mmt and the body on the mini is really small - like 1/8", if memory serves. I don't know if foam would flow down into that before it started expanding, and I don't think I could easily get epoxy in there.

Here's my idea, I'm interested in input. My big difference is that I put the "bottom" CR between the fins and don't worry about trying to pull out a CR:

1. CAREFULLY measure mmt. Install top CR above top fin on mmt. Install bottom fin between top and bottom fin set (remember - it's a split fin design). Epoxy and let dry. Use top fin as guide to make sure spacing is correct.
2. Take a deep breath and prepare fin guide from payloadbay.
3. Mix up some epoxy. While epoxy is wet:
-put epoxy deep into body near top of top fin set.
- also put epoxy on outside of top CR.
-slide top inch of mmt into rocket.
-apply more epoxy into body tube.
-slide the rest of the mmt into rocket.
-Carefully align mmt.
-Using double-dip method, install top 3 fins. Use jig. Let dry.
-Using double-dip method, install rear 3 fins, aligining to top 3 fins. Let dry.

I just followed the instructions for foaming, and did it in a couple passes. Mix foam, inject with syringe, let cure. Repeat, then trim. I stuck a piece of tubing on the end of the syringe the first time to get it all the way to the top centering ring.

Just epoxy the fin roots. Use the CJ double dip method if you like. Then give it external fillets. Nothing you can fly will hurt it.

I agree 100% with Matt double dip and forget it. Just fly it.

crossfire said:

I agree 100% with Matt double dip and forget it. Just fly it.

Click to expand...

Can you explain the double dip method? Searches come up with nothing.
Thanks

What I do is apply epoxy to root of the fin. Set fin down to mmt and kind of slide to back and forth in the fin slot. Next pull fin out of the fin slot and butter it back up up with more epoxy and reset the fin to stay this time. It works out well to get extra glue onto mmt and the fin root. I have had very good results using this method.

Like @crossfire said. Also, I think this is one of the earlier mentions of it: https://www.rocketryforum.com/threa...-stage-build-vindicator-jr.55463/#post-552270

Update and a question.
First the question:
So I realized that I wasn't paying attention to the bottom of the mmt when I put on the top CR. Now there isn't enough mmt sticking out of the rocket to mount the aeropack retainer. I think if I CAREFULLY cut off about 1/8" of the bottom of the body, I should have enough mmt exposed. (On this kit, the body is narrow enough that the retainer won't fit inside, it's almost exactly the same width as the body). Any reason not to do this?

Now the update:
All went really well. Second ring is behind first fin set and feels solid.Need to mount second fin set now.

Nice lesson learned. I almost always start my builds at the retainer and work up from there on anything with though the wall fins.