Mini Rotaroc

[JAL3]

I needed a copter design that I could build fairly quickly and easily and which would be fairly idiot-proof in order to compete in an A helicopter duration contest. I had already built a Whirl-a-While but I managed to mess it up each step of the way and it did not survive its 4th flight. Time was running out for me and I settled upon the mini Rotaroc. Construction began but cutting a sheet of balsa stock to length.

 

[JAL3]

The blade stock was then marked for 1” width to form 3 blades.

 

[JAL3]

Since a piece of BT5 happened to be sitting close by, I went ahead and cut it and marked it to length as well.

 

[JAL3]

I searched around for a BT5 nosecone and chose a Semroc BNC5E mainly because that is what I had. the cone was glued into one end of the BT.

 

[JAL3]

The plans called for an elongated vent to be cut just abaft of the nose cone to allow ejection gasses to escape. The vent was marked and cut.

 

[JAL3]

A full size fin guide was printed on the plan. I reprinted the plan on cardstock and cut the template out.

 

[JAL3]

The template was then used to mark off 3 fins on the balsa stock.

 

[kjohnson]

The First Man in Rome? Really?

I've got 3 HD models on the workbench right now. A QCR High Rotor II, and 2 different droptail piston action models.

kj

 

[Micromeister]

I'm still flying the same 13mm Rotaroc I built some time back in the 90's LOL! I just keep getting it back. it's been gone a couple times only to show up later in the day that someone happened across
something I've noted over the years about these models. It's a good Idea to lightly reinforce the area around the vents with a coat of CA and a split bamboo skewer. I'm sure you could wait a flight or two before adding the split skewers but as the ejection gases char the inside of the tube it becomes very weak at those points. I've folded the vent port tube in on a model or two while attaching the rubber bands to the pins in the NC.

 

[JAL3]

The First Man in Rome? Really?

I've got 3 HD models on the workbench right now. A QCR High Rotor II, and 2 different droptail piston action models.

kj

I thought it was The Grass Crown at about the time the photos were taken but it could have been. I'm waiting for Caesar's Women right now.

 

[JAL3]

I'm still flying the same 13mm Rotaroc I built some time back in the 90's LOL! I just keep getting it back. it's been gone a couple times only to show up later in the day that someone happened across
something I've noted over the years about these models. It's a good Idea to lightly reinforce the area around the vents with a coat of CA and a split bamboo skewer. I'm sure you could wait a flight or two before adding the split skewers but as the ejection gases char the inside of the tube it becomes very weak at those points. I've folded the vent port tube in on a model or two while attaching the rubber bands to the pins in the NC.

I've learned some of what you speak of. Though I haven't post it yet, this one won 2nd place and boosted me to 2nd overall for the competition.

 

[JPVegh]

Thanks for this thread John. I've been thinking of going this route for my B Heli build. I'm just not sure if I have enough time to work the bugs out of an original design.

 

[JAL3]

The 3 fins were then cut out with a razor knife and a steel ruler.

 

[JAL3]

A piece of wax paper was laid down and the fins set upon it. They were then drenched with thin CA in order to toughen and seal them.

 

[JAL3]

A fin alignment template was generated from Template Widget, cut out and wrapped to mark the fin locations.

 

[JAL3]

The fin alignment guide was then removed and an Estes angle was used to lengthen the lines.

 

[JAL3]

The fins were then applied along the lines with thick CA.

 

[JAL3]

The instructions gave a method to sand the airfoils of the rotors before the individual rotors were cut from the stock. Using those as a guide, the highpoints were marked and the stock was taped to a piece of plate glass for sanding.

 

[JAL3]

When the sanding was done, I cut the first of the rotor blades from the stock and examined the result and found it to be satisfactory. I did a little more sanding to work the leading edge.

 

[JAL3]

That left the stock free to be taped and the trailing edge of the third airfoil to be sanded.

 

[JAL3]

After sanding, the stock was ripped again to produce a total of three blades.

 

[JAL3]

The rotors were then sealed with thin CA and later sanded.

 

[JAL3]

I marked the BT with distance to the rotor hinges and then used some masking tape to assist in marking the tube.

 

[JAL3]

Thick CA was used to tack nylon hinges around the BT at the hinge line.

 

[kjohnson]

For folks who have the locked pin hinges (the pin is flattened so it can't pull out and the hinge halves can't be pulled apart) now would be a good time to put vaseline on the hinge to keep any stray CA out of the hinge.

The other option is to use the dremel or snips to remove the flat part of the pin so you can glue half of the hinge to the tube, and the other half to the rotor and not worry about getting glue in the hinge. You can replace the pin with an L shaped piece of music wire to make replacing rotors much easier.

kj

 

[JAL3]

For folks who have the locked pin hinges (the pin is flattened so it can't pull out and the hinge halves can't be pulled apart) now would be a good time to put vaseline on the hinge to keep any stray CA out of the hinge.

The other option is to use the dremel or snips to remove the flat part of the pin so you can glue half of the hinge to the tube, and the other half to the rotor and not worry about getting glue in the hinge. You can replace the pin with an L shaped piece of music wire to make replacing rotors much easier.

kj

Now you tell me!:eyepop:

 

[kjohnson]

You didn't ask

kj

 

[JAL3]

You didn't ask

kj

:dark:

 

[JAL3]

Thin CA was then used to tack the end of some thread to one of the hinges.

 

[JAL3]

The thread was then wrapped around the BT and upper hinges in order to more secure seat the hinges. When done, the entirety was soaked in more thin CA.