Tuesday, November 30, 2010
On the left is a before and after pic of the fin airfoil.
On the right is the rotor blade airfoil (one side flat or chambered) before and after.
The fins are smaller so the airfoil was sanded using a sanding block.
The rotor blade is 10 inches long so a consistent airfoil could be hard to do.
I used the emery board featured in an earlier post, HERE.
TIP: For support, place the trailing edge of the blade near the edge of a hardcover book. Set the emery board over the trailing edge at a slight angle on top of the balsa blade. Sand down the entire length of the rotor blade.
I find it easier to hold all three alike pieces with my left hand and square them up against a sanding block held in my right hand.
Finally the SKY WRITER MMX downscale flew for the 15th time! I've been trying to include it at every schoolyard launch.
You might be asking - Why bother to fly the small stuff?
Monday, November 29, 2010
Here's all the parts laid out on the floor. This looks to be a fun, different build.
The last helicopter rocket I built was the Estes Gyroc in the early 1970s.
Here's some parts of interest:
Three Du-Bro hinges
.025" dia. music wire for the hooks
Cast urethane nose cone
Three rubber bands
Red Kevlar thread
In the picture above you can see the self adhesive decal sheets
Back then we only had the small brown garnet, coarse "files".
This board is much larger, 3/4" wide by 7 1/2" long. There are four different grits, two on each side. The roughness spans (around) 100 grit coarse to 400 grit extra fine.
The great thing is, these boards don't really load up. If they do, they are washable.
You can pick them up at beauty supply stores like Sally Beauty for a few dollars each.
Sunday, November 28, 2010
You can eliminate some tangled lines by moving the parachute attachment point away from the nose cone.
With the nose cone so close to the shroud lines, the nose cone can pass through the open lines at ejection.
If you've ever seen a slow motion video of how violent an ejection charge can be, you would understand how the nose cone could get tangled in the lines.
Every low power kit instruction I've seen has you tie the parachute to the screw eye.
I'd suggest tying an overhand loop knot in the shock cord, one third the way down from the screw eye.
Attach the parachute's snap swivel to the loop and you are ready to go!
With the parachute tied on 1/3 the way down the shock cord, your rocket will fall in three separate parts, all tethered together by the shock cord. First to hit the ground is the tail end of the rocket, the nose cone and finally the parachute. This is the same way many mid and high power rockets are built for recovery.
If your rocket has a tower or tall nose cone, adjust the distance down the shock cord so the longer nose cone won't be banging against the body tube during descent.
Saturday, November 27, 2010
Friday, November 26, 2010
The lug and standoff were filled with CWF and sanded smooth. A coat of primer followed and sanding with 400 grit.
The instructions tell you to cut the launch lug in half, but it wouldn't match the length of the standoff. I cut it to fit the standoff, the lower lug will be longer than half it's original size.
This is the longer, lower launch lug.
I found it easier to keep the white lug against a white fin. I didn't want to do any more masking.
Thursday, November 25, 2010
The glue was placed drop by drop using the blunt back end of a toothpick. I rounded a small dowel to spread out the glue more evenly.
Wednesday, November 24, 2010
Some of the silver paint was sanded off the bottom of the nozzles for a better glue bond.
The inside of the nozzle bell was blackened in with a Sharpie pen. This is much easier than masking and spraying. After the outsides of the nozzles were painted and dried there wasn't any bleeding through of the Sharpie black color.
After the end sanding they were a little out of round. I went back with a dowel and made sure the nozzles were well shaped before gluing onto the bottom plate.
Tuesday, November 23, 2010
The retro rockets are in position.
The instructions don't specify a color. When at the Meatball Rocketry site I saw they were red and white. Working this small, I decided to just go with the red.
According to the pictures on the Meatball Rocketry site, the red motors go in the center of the upper band, not beneath it like shown in the Zooch instructions. Either way would look fine, it's ant scale! Nobody is going to tell you your model is right or wrong.
I decided to glue the nozzles in the pictured position. It's a stronger bond gluing the wood dowel to the paper wrap. If I were to glue the dowel to the white spray painted area, I'd have to remove some paint.
Monday, November 22, 2010
I got the angle as close as I could. I'll fill the gap with white glue and touch up the joint with white paint later.
Scale mistake note: The retro rockets didn't connect to the lower LH2 ducts! They were set on four of the eight standoffs. On this model, the upper launch lug is glued to a standoff.
You can make all eight standoffs and glue the retro rockets to every other standoff if you'd like. This was my mistake, I didn't look close enough to the S-1 drawing inset in the instructions. But on the positive side, this way the retro rockets are stronger with two gluing areas instead of just glued to the upper centering ring alone.
Check the Meatball Rocketry site for a better pictorial explanation.
The upper LH2 ducts go a little to the left of the lower duct placement.
Sight down the body tube to get them just to the left and straight.
While the nozzles were drying, I glued on a new bottom plate.
This time the position of the engine hook notch was rotated so the hook movement wouldn't bump up against the nozzles.
I blackened in the edges of the body tube and the old plate so when the new one is glued on the first try will be less noticeable.
Sunday, November 21, 2010
I've never had much luck making the Funky Glue Putty for the Zooch kits.
But, like everything else, you usually get better results if you keep trying!
I don't have the recommended yellow glue, so I'll give it a try with white glue.
In the first attempts, I found I was spreading out the glue to far when rubbing it between my fingers.
In later successful tries, I pressed my fingers together, spreading out a drop of glue. Pull your fingers apart and let it the thin glue sit for 10 seconds. This lets it tack up a little before rubbing again. Rub the glue for a few seconds.
Again, hold the fingers open and still and wait again. Then more rubbing.
The glue was starting to "thread up".
I rolled these small, drying pieces into a ball.
Here's the F.G.P. in place, on the turbo pump dowel. I haven't done any forming of the putty yet. It'll be smoothed out and feathered into the engine bell.
This is the Hot Rod Rockets BELL BOTTOM won on Ebay.
After two launches of the smaller 13mm UP! CUP there was soot and slight melting of the inside foam wall. On this larger cup the inside of the cup was coated with white glue to protect the foam from engine flash. That seemed to protect the inside wall. It wiped up clean with a damp paper towel.
Here's the math -
The MMX SKYWRITER it's 14th flight on a Quest Micro Maxx engine. I also caught this one on recovery.
TIP: A note on the Micro Bertha - Two years ago, Instead of Kevlar, I was using hemp shock cords. The hemp has held up very well after quite a few ejection charges. Hemp is cheap and works fine, it just isn't very pretty.
All five rockets (MMX, 13mm and 18mm engines) were launched using my surplus Quest Micro Maxx Q2 igniters! No pyrogen, just thin bare nichrome.
Saturday, November 20, 2010
The angled dowel was cut to a 1/8" length.
The sealed dowel "ducts" will look much smoother when the paint is applied. I'd recommend sealing and sanding everything in one piece before cutting the ducts to length. It's easier to sand the dowels when the piece is longer.
When sanding, this line lets you know the dowel is still facing up. The line also works like a depth gauge, the more you sand off, the less of the line is left.