Maxi Honest John

[NUBlackshirts]

Hello all.

This weekend I am starting my latest build. I found a "whole-in-the-wall" hobby store close by that has several older kits sitting around. One of the kits I picked up is an Estes Maxi Honest John. I have built many rockets, but not one with plastic fins like this has. I have seen a couple of posts about filling the fins with different substances to make them stronger. I am thinking about going with expanding foam, but not sure about how to go about doing it. Any suggestions about the technique(s) involved would be greatly appreciated.

Thanks.

Ron

 

[Ryan S.]

Good idea the estes plastic fins are really flimsy. I didn't fill mine and they crack all the time. For this application you should use the PML foam. It is two part and won't heat up and melt the fins.
you need to cut the bottom off the fins so that it has someplace to expand to or else the fins will burst. I wouldn't use the expanding foam from a can. It will definantly burst the fins open.
I have used the stuff from a can in nosecones and fin cans before with no probles but in a place that is really small I would go with the PML stuff.

 

[Mark_Newton]

I filled the fins in my Maxi V2 with PML foam. It only takes about 3mL (3cc) each of Part A and Part B to entirely fill a fin. After gluing the fin halves together and sanding them, I cut a couple of rectangle spots on the root of each fin. Each rectangle was about 1/4" wide x 1/2" long--enough to pour the foam in, and permit overflow to escape.

It makes the fins rigid when heardened, and the weight difference is negligible.