For quite a while I have been thinking about building a tube launched rocket, and after seeing the "Flippi Fin" kit sold by Aerocon Systems, I decided I to buy one!




The rocket consists of a BT55 tube and nosecone, with a 24mm motor mount, and a steel "fin can" with folding fins that is originally from a tube launched rocket flare. Also in the kit is an 18" nylon parachute, kevlar shock cord and lead shot to be used as nose ballast, as well as a 36" long cardboard launch tube.

I intend to extend the rocket to incorporate a flight computer to compare the performance of the rocket when launched from different lengths/diameters of launch tube.

I've looked at those a bunch of times, very cool!

What did they charge you for postage ??

Krusty

That is way cool. I've always liked the Flippi Fin. These things would like great coming out of a sealed tube on a white lightning motor

Postage was roughly $40, presumably because of the length of the package. I'm planning on taking a trip to bunnings at the weekend to look at "launch tubes", as I think a pvc tube would probably be a lot better than the included card tube.

I'm going to hold off using white lightning propellant initially until I get a feel for the rocket. One of the guys that wrote a review if it for the EMRR website said that as a result of white lightning's habit of "chuffing" at ignition, the rocket left the tube before the motor had come upto full pressure.

How heavy is the fincan ?

Do you reckon you will be 'allowed' to launch this at Doonside ? ie being metal

CS

I must admit it is heavier than I expected, I had assumed it would be made of aluminium. I'm not sure of the exact weight as I have not weighed it yet, but I will weigh it tonight.

I would say it is unlikely I'll be allowed to fly it at Doonside, I think I would have trouble trying to persuade anybody that the rules should be bent to allow steel fins!

Looks like an interesting rocket ROCKet STAR.
How strong are the springs on the fins? And do they lock open or are they likely to move back and forth in flight? I take it the fins just press against the inside of the tube, is there a significant amount of friction between the fins and tube?

the springs aren't overly stiff, but I think they should be stiff enough to keep fin flutter to a minimum. They don't lock in place once open and they do press against the side of the tube. I have tried them in the cardboard tube and there is some resistance there. I think a PVC tube should have a lower coefficient of friction, but that is something I plan to determine by placing the rocket inverted in the tube, and adding weight until it starts to move.
I am also keen to try spraying the inside of the tube with a product called "Back to Black". It is a silicone based spray that is used for restoring the shine to car bumpers and trim. I used to do quite a lot of snowboarding on dry slopes, and we used to spray it onto the base of our snowboards because we found it would seriously reduce the friction between the board and the nylon dryslope matting. I'm hoping it should have the same effect between the rocket and tube.

I'd have to agree - it couldn't be classified as a "model rocket"

Here we go again.... You are allowed to use metal where required as structural or load bearing components in rockets. And for all the level 2 certified people: The load bearing components of a rocket are..?

The club rules specify a minimum amount of metal. Try making that fin can in plastic...

PK

Heh, pick me pick me!

Well, lets see, load bearing would be: The sinkers you glue into the nosecone, the motor case, and, uhh, the swivels and/or quick-links in your recovery harness?

Treat it like a HPR rocket and you'll be fine - and make sure you get pics of the launch! Interesting about the White Lightning comment. I haven't had one chuff, but would using a longer tube have reduced the problem? If you had any doubts, use a solid igniter and sand the grain core.

well whats the difference between G10 fins and steel fins like that in a high speed impact? Its all going to do damage at those energies

If your WL motor is prone to chuffing, then SOME static friction between the fins and the wall would be a GOOD idea as it would tend to hold it in place until it comes up to pressure.

In fact, why not put a free piston inside the launch tube for good measure?

No need to justify it. The club rules allow for metal components where they are required . End of story.
PK

So I have weighed the fin can, and I can confirm that it weighs 63g

I was browsing on the Aerocon website today and noticed two things... firstly that the price of the kit has gone up by $10 US since I bought it a few weeks ago, and secondly they are now offering the fin can on its own for sale for $15 US. So If anybody else was thinking of building one of these, your best bet would be to just buy the fincan from Aerocon, save yourself the extra cost of shipping a large package from the US, then buy the rest of the bits (tubes, nosecone etc) from Bones, and the lead shot from k-mart.


I started building this evening, and I am doing it completely differently to the instructions.

Because the fincan is not a dedicated rocketry part, the motor tube isn't a perfect fit inside the fincan. The instructions say to create two centering rings on the motor tube with masking tape, to get a good fit inside the fincan. I decided that this would look pretty messy as there would be two large bands of masking tape clearly visible behind the fins.



My solution to this (as can be seen in the above photo) was to take a couple of the card thrust rings that I had left over from some Aerotech 29mm single use motors, and cut a section out of them so that they could be fitted inside the two rings at either end of the fincan. The resulting centering rings are just slightly too tight to slide the 24mm motor tube into, but this was resolved by enlarging the internal diameter very slightly with sandpaper after they had been glued in place. The 29mm thrust rings used are almost the perfect width aswell, so they do not protrude up behind the fins, as the masking tape ones would have done.

The other thing I have done differently to the instructions is to paint the visible section of the motor tube before I install it into the fin can. The instructions suggest to colour in the tube with a black marker pen after the rocket is built... I just thought that would look naff!