Monday, May 8, 2017

Estes Photon Probe #3026 Build, Part 8, Tube Prepping

The launch lug was glued on in line with the engine hook side.

A painting wand is slipped in the back. Rolled up paper towel is pressed into the engine mount recess to keep paint out of the inside.
Primer coats followed.

There is a light difference in the nose cone shapes. The original plastic nose cone (on the left) is slightly broader at the tip.

Here's a strange photo edit:
TIP: To prevent yourself from sanding over and thinning the end of the tube, slip your left thumb into and against the tube end. The skin at the base of your thumb acts like a "bumper" and prevents the sandpaper from rolling over the tube edge.

The original kit fin marking guide was off! I would expect the older kit to be more accurate. I could tell it wasn't correctly spaced by rotating the guide after initially marking the tube.

While the newer kit guide didn't quite meet at the ends, the fin spacing was accurate.

After the primered tube was sanded down and the fins lines marked, the fin positions were scraped to remove the primer right down to the bare tubing.

The scraped area are a little wider than the 3/32" thick fins to allow the fillets to bond to the tube.


  1. Hey Chris,
    In the instances where it's necessary to fill/prime the body tube and fins prior to gluing due to tight placement and design elements ( the Hydra 7 comes to mind) I've been using pin stripe tape to mask the glue lines. An added advantage is that it preserves any fin and lug lines that were marked. Anything to save time, lazy slob that I am. Thoughts, pro or con?
    Also, thoughts on sanding off the glassine on body tubes prior to gluing? A couple of manufacturers have recommended it, most don't even mention it. Cheers!

    1. Hi Bar,
      I have used tape to mask the fin gluing areas in the past. It really just depends on my mood. Maybe I'm getting lazy! You're right, it would protect the fin lines.
      I don't sand the body tubes. I fill the seams and when sanding the filler to the surface the tube is roughed up a bit. I've seen builder's sand the glassine completely off! Another builder peels it off. What for? Removing it completely would weaken the tube. A little bit of roughing up the surface should be enough to allow the glue to permeate it.
      Estes instructions show the launch lug being roughed up. For years I never sanded launch lugs and never had one come off the body tube.

  2. I prep my glassine tubes for glue by gently rubbing it with denatured alcohol. It removes the gloss without removing material from the tube.

    1. Hi Dave,
      I've never heard of using denatured alcohol on a body tube. I'll have to check that out.