Estes Mini A Heli #007272, Finished

Well, this was different.
TRIVIA: I believe this is one of the few designs Estes has suggested for NAR competition. The other two competition designs were the original Drifter (24" parachute?) and the BT-50 based Sprint.

My finished weight was .72 oz. The kit face card doesn't show a weight, but the Estes website says .76 oz.
I hope to launch this one at the upcoming NARAM in the Helicopter Duration competition. We'll see!

Estes Mini A Heli #007272, Build, Part 18, Hold Down Thread

The instructions show two small holes "drilled" on opposite sides of the body tube.

GOTCHA: The burn string and helicopter blade deploy is not explained in the instructions or on the website. I understood how burn-string models work before assembling the kit, I've been around a while. A first timer might be confused.



Don't just blindly drill two holes with the tip of a hobby knife. Measure and mark the hole locations directly opposite each other.
These marks are 6" up from the bottom of the body tube.

A new blade with a sharp tip was used to start the thread holes.

After a small hole was made, it was rounded and cleaned up using a smooth sharpened dowel.

The holes got some CA glue applied with a Q-tip. Light sanding followed.

A needle is used to run the thread through the holes.



Fold the blades down with the ends between two fin faces. Hold the blades down against the body while tying the thread.
Follow the instructions illustration to weave the thread around the blades.
Tie off the thread with the blades are held against the body tube, each blade set between two facing fins.
Set the three rubber bands into the hinge hooks.

Estes Mini A Heli #007272, Build, Part 17, Hinge Dowels & Fin Trim

Here's how the rubber bands fit into the notch at the top of the side plates.

The short dowel hinge pines were dry fitted here.






The instructions say to cut the dowel into three 1/4" pieces. After the test fit I cut them a bit shorter.









A glue dot is applied to the outside after the dowel pin is pressed into place. Raise and lower the blades to make sure the inside hinge is still clear.




I added some small vertical trim stripes of Contact Blackboard Material. The leading edges of the fins are almost straight so the strip was rolled over the top and down the sides. These weigh almost nothing and are cleaner edged than the marker lines under the blades.

Estes Mini A Heli #007272, Build, Part 16, Blade Marking

This rocket won't be painted, I want it light and smooth as possible. Some coloration can be used.
I've read where marker ink adds very little (if any) weight to boost gliders. Competition flyers will color the underside of their glider wings so they can be seen against the sky.

The kit face card shows a dusting "blend" of spray paint.
TIP: Blending spray paints (two color blends) will end up with a rough finish and higher drag. You can't really sand and smooth two blended colors with sandpaper or polish.

Before doing any marker ink "bands" on the underside of the blades, I tested markers on the leftover balsa sheet. As expected, there was some bleed of the ink down the wood grain.
I'll have to use an Ultra Fine Point Sharpie.





I planned a pattern on paper before any ink was applied.
These markings could help with tracking and recovery.

The blades were set directly above the marking template. My trusty 2" machine square helped draw lines perpendicular to the blade.

The ultra fine point Sharpie gave the sharpest lines with very little ink bleed.

Notice the marks inside the squares to be colored. When you get rolling, it's easy to color in the wrong box.

Draw the box sides with the smallest pen then switch to the medium point pen to fill in the space.

Here's the underside of the blades after all three have been marked.

With any luck, during descent the spinning blades will show circles in different widths from narrow to wide.

Estes Mini A Heli #007272, Build, Part 15, Nose Cone & Hinge Fit

The replacement balsa nose cone had a better shoulder match than the plastic nose cone did. There is still a seam to fill.


The picture on the right shows a wrap of masking tape beneath the seam. This prevents sanding of the body tube.

The nose cone also got one pass of CWF and sanding. After that a coat of  CA was wiped on. This strengthens the balsa and after sanding will give it a smooth, low drag finish.

This is the upper assembly after the hinge housings are glued on.








A test fit of a helicopter blade. This shows the blade against the "stop" after ejection.

Estes Mini A Heli #007272, Build, Part 14, Vent Slots, Tubes and Fins

Here's all three sides of the helicopter blades - top, back of the top and low end.









The inside and outside of the vent slots got a wipe of medium CA to strengthen them, especially at the corners. Light sanding to smooth the surface followed after it dried.







TIP: The two tubes were glued together using an aluminum angle. This helps keep them straight and is better than trying to roll them over a flat surface.

I used a Q-tip to apply a bead of glue for the engine block.
TIP: I marked the glue distance on the Q-tip with a fingernail. You can see the depression near my fingers in the upper picture.




The fins are glued on 1/2" from the end of the body tube. This 1/2" open tube area allows you to use a wrap of tape for engine retention, no engine hook.

The small, tapered launch lugs were glued and aligned. The low lug glues to the fin root edge.

Estes Mini A Heli #007272, Build, Part 13, Helicopter Blades

Yellow glue was run down the open cut line and the excess removed and smoothed out with a Q-tip.

Go a few inches at a time, don't allow the glue to set and skin over before smoothing it out.

Here's how the backside of the blade showing the break line.

The blade reinforcement pieces are cut from the fiber paper. You barely have enough to trace and cut four pieces. You'll only need three.

I only smoothed glue over 3/4 of the fiber paper. This gave me something to hold onto when the reinforcement was positioned on the hinge arm end.




The glued side was centered and pressed into place.



Glue was added to the dry side and pressed down even with the end of the balsa blade.

Estes Mini A Heli #007272, Build, Part 12, Helicopter Blades

The blades are cracked down the lines that were lightly cut in the last step. If the blades don't crack easily, cut the lines a little deeper.

TIP: Before using the blade angle guides, wipe out the laser cut ash from the center slots.
Any burnt ash could discolor the balsa when they are slid down the length of the blades.

The #1 guide form is slid down first.
TIP: Be ready, it's a little difficult getting the #1 guide started on the far end. The angle slot is the opposite form with the high end to the right side.
It might have been easier to wait before gluing the hinge arm on. With the arm in the way you have to slide the #1 form all the way down the blade from the opposite side. It is do-able but had me concerned at first.

The 2 guide goes to the mid point, followed by the 3 near the outside end. 

A few drops of medium CA was allowed to run down the cut trench. Go light, don't glue the forms to the blade.
I'll follow up with yellow glue after the forms are slid off.

Estes Mini A Heli #007272, Build, Part 11, Helicopter Blades

The helicopter blades are removed from the balsa sheet. The leading, trailing and outside edges are rounded. The notched end (near the X3 side) stays square.
The instructions make no mention of air foiling the blades.

The instructions show the hinge arm glued in place and CA glue applied to the outside edge.
I set the arm into the blade slot to see where it made contact with the balsa. I applied medium CA glue to the edges where it wouldn't touch the blade.




Here's how the arm is positioned on the blade.




The bottom of the arm should be flush, even with the flat side of the blade.

The blade is to be scored with a knife and cracked down the line.
I tried to score the first blade but my knife wanted to travel out of the laser cut line and into the wood grain.

TIP: Trace down the line with a sharp, soft pencil. The pencil line will give you a better contrast and help direct the knife down the line.

Use light consistent pressure, you aren't trying to cut all the way through the 1/16" thick balsa.

The blade will be cracked down the line, leave some of the balsa to act like a crack "hinge".

Estes Mini A Heli #007272, Build, Part 10, Hinges

Here's how the sides match up, the double layer D parts are positioned on the outside single layer E piece. Another E piece will glue on the top of this.







Use the dowel again to help line up the E pieces and the holes.
Three clothespin clamps were used on each hinge assembly.

Once it's glued up, the hinge assembly is thick! You could just glue it to the body tube but the side edges would be raised.

Some 220 grit was wrapped around a 1/2" dowel and the root edge of the hinge assembly sanded to a inside curve. I didn't sand too much, I didn't want to lower the blades close to the body.






The kit includes a hinge alignment tool.
GOTCHA: It couldn't be used as directed, the hinge assembly thickness was wider than the slots in the alignment tool!
I still used it to visually set them around the tube with equal spacing.

Estes Mini A Heli #007272, Build, Part 9, Hinges

The two "D" center parts (with the rubber band hook) are glued together.
This one started to separate, not down the glue joint but between the layers. The split was widened a little and glue spread inside with the knife blade. Both pieces were clamped again to dry.








I used the dowel when pairing up the "F" for some sanding cleanup on the edges.







I took this picture before the F pieces were glued on the sides of the interior D pieces.
This shows how the center arm rotates forward (to the right). The interior D part has the upper and lower travel stops.
A second F piece will go on the top. The D and F parts are glued up without the C arm in place.

Before gluing up the assembly I added a glue bead fillet to the upper surfaces. This rounded edge seals the card stock and might result in less drag.
The double thickness center D pieces got a wider round glue bead.

Estes Mini A Heli #007272, Build, Part 8, Hinge Arms

The thick card stock hinges are definitely the way to go for a first time helicopter recovery build. No weird wire bending!

The inside swing arms were lightly sanded on the flat sides for better adhesion.
On the left is the before with the charred surfaces, on the right is after sanding.


The arms are glued together, I clamped them with clothespins.

To help the alignment, the dowel was slipped into the holes.
Three sets of two are made for the three blades.

I didn't sand the arm sides until after they were glued together. Don't sand off much or change the shape, just clean them up with 400 grit on a block.