Saturday, December 17, 2016

Estes Long Tom, Follow-Up - Sustainer Fin Locations?

At a recent Orlando R.O.C.K. launch, Glenn S. launched his Estes Long Tom.
I looked at the fins and wondered why they were positioned up from the end of the sustainer body tube.

On the left is my finished Long Tom. On the right is Glenn's model. Notice the upper stage fin locations?
Glenn said this was his second Long Tom build. He noticed in the instructions that it showed the fins glued on up from the rear of the body tube. His second build had the raised fins.
I read and follow directions and wondered how I could have missed this.

Earlier in the instructions you are instructed to mark the fin locations with a wrap around guide.
No mention is made to make a mark 1/2" or so above the low end of the tube.

The fin gluing illustration in the middle of page 4 shows the two fins marked "J" above the tube. Look at the straight on view of the middle fin. It looks to be even with the end of the body tube.

The inset picture is from a later step in the instructions. The trailing edge is even with the end of the tube. Most all other drawings show the same fin position.

Here's the face card illustration.
The back end of the second stage is black but you can make out the fins are glued on up the body tube.

The Estes instructions are inconsistent. Is it a big deal, does it effect the flight? Probably not.
If you wanted to build it closer to the old Centuri version it's a little maddening.
I went to double check the instructions on the JimZ site but many of the Centuri plans don't come up.


  1. Chris,
    Did a little digging and I found a good picture of the original Centuri face card here:
    As you can see, the sustainer fin root end seems to be even with the end of the sustainer tube. So rest assured, your build does conform to the original Centuri model.

    1. Thanks BAR,
      I'll sleep better tonight knowing I got them right! I did some searches but didn't find that Aerocon page. My question is, why did Estes show the trailing edges set higher on the tube in a few places? The people that help design these kits are still alive. A few phone calls could have answered any design questions.

  2. Addendum: Looks like the Estes Long Tom has the sustainer fins higher than the end of the tube, as opposed to Centuri's. So your build "preserves the original design". At least that's what you can claim.

  3. The Centuri Long Tom plans, like many of the others missing from the JimZ site, have been preserved at the Internet Archive's Wayback Machine:

    1. Hi Rich,
      I looked it up on the Wayback before I did this post. While the opening thumbnails page comes up like JimZs did, you can't enlarge the individual pages to see any real detail.