Whirl a While - A Helicopter Duration

[JAL3]

The upper nose cone was supposed to be lined with some kind of tube which completely escapes me right now. Thinking I understood what it was to be used for, I bought some soft aluminum tubing at the hobby shop that would just slip over the carbon rod. I marked the length from the plans and used a razor saw to cut it to length.

 

[JAL3]

I slipped the tube over the carbon rod and found that the fit was still a bit rough. I took out a round file and de-burred the ends and reamed it so that the rod turned freely.

 

[JAL3]

The tube was to be fitted in the forward nose cone. To drill the hole, I took a very small drill bit and twirled it by hand into the back end of the cone. When it had gone the entire length, I used that hole as a pilot and selected the correct sized bit and twirled that through by hand.

 

[JAL3]

Some epoxy was then mixed and spread along the tube which was then inserted into the forward cone.

 

[JAL3]

The forward BT was then glued to the forward NC with some Titebond III.

 

[JAL3]

The rear nose cone also needed to be drilled to receive the carbon rod. It was done in the same manner as the forward one but a smaller bit was used since the rod would be mounted directly, without any tubing.

 

[JAL3]

The carbon rod was then glued into the rear NC with a bit of thick CA.

 

[JAL3]

The rear cone was then glued into place in the rear BT.

 

[hcmbanjo]

Hi John,
I'm enjoying your (comprehensive) build thread.
I've had this one on my want list for quite a while.
Great work, as always!

 

[JAL3]

Hi John,
I'm enjoying your (comprehensive) build thread.
I've had this one on my want list for quite a while.
Great work, as always!

Thanks.

Coming from you, that's high praise indeed. Of course from the distance you are, you cannot see the "airfoils".

I do appreciate the encouragement.

 

[JAL3]

The grain on the rotors was "filled" by smearing a bunch of thin CA into the surface, using a latex glove of course.

 

[JAL3]

A few minutes later, the rotors were flipped over and the opposite sides were similarly treated with CA. When the CA had set, both surfaces were sanded with #600 paper.

 

[JAL3]

Following the advice received on TRF and in an effort to put all inferior paintjobs to shame, I "painted" the bottoms of the rotors with a black Magic Marker and the tops with a red Sharpie.

 

[JAL3]

The plan for this rocket specified the type of hinges to be used for the rotors and I was pleased that my local hobby shop knew exactly what the plan meant because I did not.

 

[JAL3]

The hinges were just the right size to form a triangle circumscribed by the BT5 tube when inserted into the hub unit.

 

[JAL3]

The most difficult part of this build thus far was trying to epoxy the hinges into place. I mixed a small amount of epoxy and tried to use a toothpick to stuff it into the space between the hinges and the BT while avoiding contamination of the pivots. I was only partially successful but the small amount of contamination I did cause seems not to have been enough to completely lock up the hinges. I was able to work them back and forth.

 

[JAL3]

I selected one of the rotors and then drew a line through its middle.

 

[JAL3]

Then, using a steel ruler as a guide, I sliced it down the middle with an X-acto.

 

[JAL3]

We now pause this build thread while I ask a question.

I know I am supposed to bend pins to form the attachment hooks for the rubber bands. I suppose that with enough pins to waste, I can eventually form the shapes needed with some needlenose pliers. Assuming that is done first, how does one insert them through the blades? If you insert them through the blades while they are still straight, how does one bend them without destroying the rotors?

 

[jsdemar]

We now pause this build thread while I ask a question.

I know I am supposed to bend pins to form the attachment hooks for the rubber bands. I suppose that with enough pins to waste, I can eventually form the shapes needed with some needlenose pliers. Assuming that is done first, how does one insert them through the blades? If you insert them through the blades while they are still straight, how does one bend them without destroying the rotors?

Use two pairs of pliers. You can also do a partial bend before poking the pins through. It's been a few years since I did this, but that's what I vaguely remember.

 

[kjohnson]

Make the bend more than 1/16 long and you can insert it after bending. If you are concerned, practice on a scrap piece of balsa till you can do it before trying it with your rotors.

kj

 

[JAL3]

Use two pairs of pliers. You can also do a partial bend before poking the pins through. It's been a few years since I did this, but that's what I vaguely remember.

Thanks. I'll try but I have a feeling its going to get ugly. I better wait till my wife is out of the house so she won't feel the need to wash out my mouth with her homeade Korean lye based soap.

 

[JAL3]

I cut out the template for the pin reinfocements and traced the outline onto a piece of 1/32" plywood.

 

[JAL3]

The rotor halves were rejoined by cutting a strip to trim monocoat and applying it along the bottom of the rotor.

 

[JAL3]

The plan was then used as a guide to cut out a piece of the trailing edge of each rotor on the hub end.

 

[JAL3]

The reinforcing squares traced onto the plywood were cut out with a pair of scissors and the applied to the bottom of the rotors with thick CA.

 

[JAL3]

A rubber band was cut into strips and 3 strips were glued along the top surface of each rotor to snap them open when released. Thick CA was used.

 

[JAL3]

Each of the rotors was then tacked to a hinge with more thick CA.

 

[JAL3]

I used a pin to try to drill holes through each of the rotors and the reinforcing squares. I learned that balsa is harder than I thought and that the CA did not do a very good job of sticking the squares to the rotors.

 

[JAL3]

I used a razor blade to scrape away the magic marker stain from where the reinforcing squares were.