Thursday, December 18, 2014

Secrets of Estes Modeling, Part 1

In a blog comment, David Carllucy sent me the link to this article by Mike Dorffler telling how Estes builds their catalog models. This copy was in Sport Rocketry magazine but is worth repeating. 

      Secrets of Estes Modeling
by Mike Dorffler, Estes Industries

We break down the method to build a good quality model into specific tasks, then bring these together almost like an automobile assembly line. We plan it out before we start. That way if you screw up one task you can redo that portion and go on. It's much more difficult to completely build the model and then try to paint it. We build the engine mounts, fins, body tube assemblies, etc., finish them as necessary, then bring them together.

We do fins like this. First of all, we replace the balsa with basswood. It's nuts to try to fill and finish fins made from balsa. The basswood is much finer grain and finishing goes so much faster, the results are superior. Go find yourself some Sprayon brand industrial primer light gray #00341. Peel the sales label off the basswood sheet and use some lacquer thinner to rub away any of the adhesive left on the wood from the sticker. Use some 400 wet or dry paper and sand both sides of the sheet smooth. Then stand the wood up on one end against a cardboard box or similar and power drive a heavy coat of the primer into one side. Let this dry and repeat for the other side.

Sand again and paint again. Then sand the sheet again almost back down to the wood itself. Once you have tried this you will immediately see why it works so well.

Now use the balsa fin you are going to replace as a pattern and trace it on the basswood sheet the appropriate number of times. Cut the fins out with a razor blade or X-Acto. We don't use a bandsaw because the fin edge will chip no matter how careful you are. Sure, you could cut them about a 1/16" oversize and sand them back, but it's more work than just blade cutting them in the first place. Sand the fin edges smooth while occasionally stacking them all up to see if they match. Take the 400 and just kiss the edges where they meet the fin sides to make a small radius. Don't make the effort to try to radius all the fin edges. I don't want that. They look better if the edges look almost square. Put a piece of plastic bag over the end of your finger and seal all the fin edges with cyano EXCEPT the root edges. You can actually do this now or after the fins are attached.

We seal the body tubes with a heavy coat of gray primer, sand, seal again, and then sand again. Use whatever tube marking guide or method you choose, but use only a pencil to mark the tube for fin and launch lug placement.

Anything but pencil will get absorbed by the paint pigments. We run straight lines the entire length of the tube so you can sight down them when attaching the fins. Also, to get the lines straight we use two-foot lengths of 1/2" aluminum angle. You just lay it on the tube and it's automatically straight.

First run a set of alignment lines the length of the tube, spaced appropriately for the fins. Then run another set next to the first, spaced the thickness of the fins. The idea here is that you will attach the fins BETWEEN the lines and you can see immediately whether they are straight or not. Now take your pencil and put cross marks on the tube where the fins are going to be making narrow rectangles. Use a narrow sanding bar or those little finger nail sanding strips to sand through the primer and back down to the 'brown' of the body tube.

Build the engine mount, test-fitting it in the body tube as you go along. Paint it flat black when done. Also paint the inside of the body tube flat black where the mount will go just deep enough so that you can't see the brown on the inside. Install the engine mount using epoxy. We use the 15 minute type which allows enough time for adjustments before it sets. We don't use Titebond here because, when it dries, the water in it makes 'coke bottle' type impressions around the body tube where it was applied inside.

These are the Estes methods for building catalog and trade show models.
Over the years I've used similar ideas, like building in sub assemblies and filling all grain and seams before gluing it all together.
Interesting to note: "It's nuts to try to fill and finish fins made from balsa." But, balsa (or now Tung wood) is included in most all kits.
On occasion I use basswood, it's stronger and easier to finish.
Mike mentions using epoxy for engine mounts: "We use the 15 minute type which allows enough time for adjustments before it sets." We've all figured that one out! 
I wouldn't recommend painting the inside of the engine tube flat black, that might interfere with inserting an engine. Again, this is how they build for catalog and face card pictures.


  1. So, they fill spirals with primer only? And will primer alone fill basswood fins? If so, that would cut down the build time on a couple of my rockets!

    1. For me, it's easier to use CWF on the spirals and one coat of primer filler, then sand. To fill the spirals or grain with primer alone it could take a few coats and sanding between coats.
      Basswood really doesn't have any real grain, primer alone could fill and seal it. Understand that these methods are for catalog and trade show models. They needed to be stronger for packing and transporting. Try it out and let me know the results.
      Most all kits I build use the wood that comes with the kits.

    2. FYI, I used the CWF sealer on my basswood fins, and I wondered why it worked so well...3 coats and you have to look very, very hard to see any grain. I haven't had a chance to paint them yet, but I imagine the paint will go on very nicely. T_L_B

  2. Interesting. I will definitely give the "primer only" technique a try on my next build.

    1. Hi Eddie,
      Primer only on body tube seams requires a thick coat and sanding, then repeat. I use CWF because it's just one fill and sand then one coat of primer filler to fill any remaining seams.
      Primer sanding is a pain. Sanding CWF is much easier for me.
      I don't think balsa would look as smooth with just two coats of primer and sanding.
      Try it and let me know how it works for you.

  3. Interesting! I have just returned to the hobby after 30 years...anyway, my first two rockets I built, I ditched the balsa fins (what is Tung wood?) because they seemed too weak and flexible; I replaced them with basswood. I decided to do that with all my models, but was just wondering if that was overkill. Based on this, it appears not.

    1. Hi Anonymous,
      They make Tung oil (wood finishing oil products) from the seeds of Tung trees. Tung wood is China's version of balsa.
      Tung wood is stiffer, harder and a little heavier than balsa. I'm finding Tung wood is harder to fill than balsa.
      I'm also leaning towards replacing kit Tung wood with basswood.