Estes V2 - I Encountered a Fin Fit Problem

The fins on the V2 don't get glued directly to the outside of the rocket as on most model rockets. The fins have tabs which go through the slots in the boat tail and make contact with the motor tube. It's the fin tab roots which attach to the motor tube. This is called through-the-wall construction, and usually it adds strength to the fin attachment. It's used a lot in high power rocketry.

But while test fitting the fins, it became apparent to me that the V2 fin tabs made solid contact with the motor tube on three sides, but on the fourth side, there was a tiny gap. Wood glue is great adhesive for model rockets, but it's not very good at gap filling. To get a strong bond, the two parts have to touch.

At first, I thought maybe I had installed the motor mount crooked. But looking at the boat tail from the bottom end, it looked like maybe it was slightly out of round. If I gave it a squeeze, I could get the parts to touch.

So, what to do?

I could use a thicker adhesive, like epoxy. That would fill the gap, and I could also use it to attach the fin roots to the outside of the plastic boat tail, for extra strength, if I wanted to.

But I prefer not to use epoxy with paper rockets. For wood to paper, it's no better and adhesive than wood glue, and also, it's heavy. With smaller fins, I want to keep the excess tail weight to a minimum. I'm already likely to use a small amount of epoxy for fillets. So I'd prefer to use wood glue here.

Then I had the idea - what if I could reshape the boat tail by hand, and get it back to a round shape? I could warm the plastic and try and mold it while it was soft.

I got out a hair dryer and warmed up the part. I got it so hot I had to use an oven mitt to handle the plastic boat tail.

The good news is that it worked - sort of. I was able to squeeze it and change the shape, which set when it cooled.

The bad news is that I didn't shape it correctly, and the fin still didn't quite touch the motor tube. In fact, I kinda made the boat tail look worse.

But only slightly, and you have to look closely at the back end to tell. The picture above is the before shot, and I forgot to take an after, but it doesn't look any better.

So, I'd have to figure out the best way to adhere the fins to the rocket with the boat tail out of round...

I figured it out and will tell you how it went in the next post.

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