Saturday, July 31, 2010
Friday, July 30, 2010
Wednesday, July 28, 2010
The MX-774 has four flat bottomed fins that stand flat and square.
I've gone back and forth over the years on the best way to fill body tube seams.
Thirty years ago I used white wall spackle, back when it was real wet and gritty. It was too wet and gritty for the kraft paper tubing.
More recently I've been using Elmer's Carpenter's Wood Filler mixed at the same consistency you'd use on to fill balsa.
I first used small brushes, painting over the seams. Then I'd lightly "squeegee" off the excess with a razor blade, leaving as much as I could in the seam.
For now I use a old, dull X-Acto blade to apply it. I dip just the tip of the blade into the filler, leaving a drop on the blade tip. The bead of filler is set into the seam. I can drag and spread the drop of filler down the seam. The Blade edge easily stays in the seam trench as I push the filler forward and back.
You are doing about an inch at a time, then going back for another drop of filler.
Because the filler will shrink when it dries, I don't "Squeegee" off the excess. I simply sand the raised ridge down to the surface. Tube seam widths will differ between tubes, a smaller width seam will hold the filler better than a wider width seam. Let the filler dry thoroughly before sanding.
I use 400 grit on a block to sand off the dried filler. Sand lightly, you don't want to knock the filler out of the seam. Using Carpenter's Wood Filler will usually fill 3/4 of the seam depth. The last 1/4 will fill with spray primer.
Tuesday, July 27, 2010
The tail cone was used to push in the mount against the lower centering ring. When the tailcone was about 1/4" from the end of the body tube I removed it and twisted the engine mount to spread the glue evenly around the top centering ring. The tailcone was replaced and pushed in the final 1/4" against the body tube. With the tailcone butted up against the body tube, the mount is in the correct position.
The picture above is taken from the top looking in. You can see how the upper glue bead is even from twisting the mount and evening out the glue bead.
With every engine mount installation, you are working against the clock. This install had three distinct movements. Partial install slide in, twist of the mount to spread the glue evenly and final push into position.
I know some are thinking: "Why bother? Nobody will see the inside anyway." I try to get both - good, clean internal and external construction.
Here's the dry fit of the tail cone, both engine mount tube and the end of the tailcone are even.
Occasionally I'll post some pictures of something I've worked on from the past.
Here's my version of a Saucer, very loosely based on the old Centuri design without the blind embossed surface. It's 7 1/2" in diameter and 3 1/4 inches high.
The top was drawn on my laptop and printed to cardstock. that print was glued to thin foamboard making it light and very strong.
The "Landing Lights" were printed in yellow, but I alternated with some Monokote Chrome Trim dots, punched out with my rotary punch tool.
The four underside fairings were tough. Even though they are the same width from side to side, they would pull in when glued giving it a scalloped effect.
To correct this, the fairings would be drawn to "bow out" a bit in the middle. Next time, the outside edges of the internal fins will be cut shorter.
It'll fly again on a C6-0 at the N.E.F.A.R. launch in Bunnell, Florida on August 14.
Monday, July 26, 2010
There is a 1/8" step from the end of the body tube to where the tail cone starts to angle in. This'll require a little filling. I'll probably end up just filling the small hole in balsa root edge instead of filling the entire tailcone step.
In the picture you can see where I cut sharp "Vs" in the leading edge of the cardboard.
You can be as careful as you want when doing a laminate like this, but there will be a little misalignment.
Sunday, July 25, 2010
The decal has been drawn up on Corel Draw. I'm waiting on another project so I can print for two rockets on one decal sheet.
After the decal is applied, I have to decide whether to spray a flat coat or gloss coat overall. Flat finishes get dirty quickly and white can really show the dirt.
You can see there is a notch for the engine hook in the lower ring. There is no no engine hook supplied in the Bull Pup kit. While the Estes instruction drawings don't show the notch, I would assume Estes just went with a generic ring set that can work with or without hooks.
I don't use Estes "Tea-Bag" shock cord mounts. Kevlar was tied around the upper centering ring. A small hole was drilled for the Kevlar to pass through. I should have put the notched ring at the top and feed the Kevlar through the notch!
That brown lip on the end of the BT-20 tube is CA glue. To increase strength, I always run a bead of thin Super Glue around the ends of body tubes and lightly sand smooth.
Saturday, July 24, 2010
I'd already built a Estes Bull Pup 12D, but it was a little tough to pass up the clearance price.
I always wanted one, but never built the old Centuri kit. This version will be a bigger at around 16 1/2" tall. The Centuri kit was a short 11" tall.
To the left in the picture are the extras going into my spare parts box.The white body tube and everything to the right are the parts I will use for the build. I still have to find a 1/12" diameter dowel.
If you'd like a high resolution PDF to make your own mini Missile Toe, email me at:
John had an interest in competiton and I suggested the online EMRR Challenge. The Challenge is a great way to expand and try a few things you wouldn't normally do in a weekend launch. I think these pictures are his way of getting even for my suggestion.Here's entry #6 in the EMRR Double Vision Photo Contest:
"Chris and I are prepping the twin Squatty Body rockets for their moment in glory. A moment of robot dancing overcomes us both. Note the finely applied details and paint, similar in color yet diverse in effect."
"Chris Capturing the moment. If one ever wondered what 30+ years of rocketry do to someone . . . check out the hair. Next time he needs to back up when he hears the countdown!"
Well, John - it was windy that day! I started in rocketry in 1969, off and on I've been doing this for 41 years. You'd think I would have figured it out by now!
You can vote (for John's entry) at:
By accident, I bought some square toothpicks when I meant to get the round ones. I was stuck using the square toothpicks when prepping some MMX engines.
Some of my best rocketry "finds" have been by accident.
Friday, July 23, 2010
Thursday, July 22, 2010
I ended up buying gloss in the colors I use most - White, Black, Yellow, Orange and Red. I don't paint my rockets green or blue (unless it's dark blue) for obvious reasons. I finished up my shopping with one can of flat clear.
The paint in the picture is my new spray of choice - Rustoleum Painter's Touch - Ultra Coverage, 2X. I had to find a new paint after Krylon changed (and screwed up) it's formulation.
TIP! Water slide decals adhere better to a smooth, gloss finish. If a decal is placed on a flat finish, the edges won't stay down and the clear areas will "silver". So on scale models, apply decals over a gloss finish, let dry, then apply the flat clear coat.
ANOTHER TIP! Krylon Gloss Clear Coat is garbage! It'll turn your shiny finish to satin with one pass of the can. (Unless you buy the flat coat to purposely dull a gloss coat like I did!)
Wednesday, July 21, 2010
Axe figured it out yesterday.
There's a pretty surprising misprint on the engine.
It's a 1/2 A3-2T, printed in Green ink overall.
Check the top of the casing - UPPER STAGE?
Someone at the Estes factory obviously didn't reset that printed area at the top when this single stage engine was printed.
Pretty easy to spot when you look twice, I wish I'd double checked the engine before I used it!