Flippifin is an unusual tube-launched, folding fin rocket.
The kit comes with all of the elements to construct the rocket. The key element is the lightweight steel folding fin assembly that derives from a surplus military flare. The plastic nosecone will require added weight to offset the relatively heavy fin unit on this lightweight model rocket, so the kit comes with lead shot for noseweight. The kit comes with some shock cord of appropriate material however it is too short. The military surplus chute that came with the kit is overkill and makes flight preparation tricky due to its bulk. I substituted a slightly smaller, cheap square nylon chute that could be packed in half the volume. Recovery was safe and there was no damage to the rocket when using this chute.
This kit provides an unusual building and flying experience. The rocket can be assembled in an hour or two. The 24mm cardboard airframe is fitted to the metal fin unit in a very straightforward manner using improvised tape centering rings and CA glue. As mentioned in the instructions, do not use too much CA. I amused myself for more than 1 hour cleaning excess CA from the hinges with acetone and Q-tips. My freshly humbled ego forced me to reengage my brain and I proceeded to finish the rocket. It went together very easily and is suitable for anyone who has built a few model rockets and enjoys a slight challenge. The Kevlar® attachment of the shock cord is good, but the shock cord itself is way too short. I ditched the material that came in the kit and used 8 feet of medium-duty elastic that I had on hand. Once I had completed assembly, I decided to look at the instructions again. That is when I noticed that there is a clear description of how to attach the fin assembly to the airframe and that in fact, the fins have a front and rear end. I was surprised to see that I had put them on backwards. I decided to check out the Aerocon website and noticed for the first time that Bob Fortune has this very nice little slide show that walks you through construction and points out the differences between the fore and aft ends of the fin assembly. My ego was bruised once again and I sent an email to Bob who assured me that my brain is probably no more feeble than the average doofus and that I should forge ahead and fly the Flippifin anyway. This turned out to be excellent advice. I never told Bob how I had dumped a quart of CA all over the fins and had spent all afternoon breathing acetone fumes while trying to get the fins cleaned up... I epoxied all of the lead shot in the nosecone as per instructions.
Bob does not place much emphasis on the launch tube, but he does mention some experimentation that has been done with it. I think that the launcher may be an area where some improvements or modifications could be made that may significantly improve the flight performance of the rocket. Bob alludes to this in the kit and leaves it up to the modeler to use a little creativity.
Thus, I decided to think about the launcher when I should have been doing more important things. I decided that for the initial launch of Flippifin I would make any modifications to the launch system as long as I could complete the modifications in one hour or less. Naturally, I started this process at about 3:00am in the garage after having consumed some rocket fuel. I decided that I wanted a strong rear seal on the tube that would still allow quick preparation for flight. To satisfy these requirements, I cut a couple of flanges from trash plywood paneling about twice the diameter of the launch tube and drilled a hole in one of them to slide onto the tube. It then cut these into a sort of "C" shape so that the tube could nestle up against a launch rod or some such pole. I cut a plug and bolted this to the solid flange. I then drilled three holes around the perimeter of the flange so they could be bolted together. I epoxied the open flange an couple of inches from one end of the launch tube. I now had a way to quickly and easily bolt the bottom flange/plug on to the tube for a secure base. I should have used some higher quality plywood for the flanges as they were mangled a bit when I had a slight mishap at the first launch but they still work fine. I will make them a bit more streamlined and beefier on future launch systems. I think the launch system deserves more attention and this kit is wonderful in that it opened my mind to all sorts of possibilities.
Upon examining the fit of Flippifin in the launch tube, I decided that I wanted to better conserve the pressurized gas that forms behind the rocket upon motor firing. Bob mentioned in the instructions that wadding or a piece of felt at the rear of the rocket might help. I decided to cut a simple, floating centering ring (a seal disk of sorts) from plywood. I figured that it would help capture the ignition gases and push up against the rear of the rocket and fall off as the rocket exited the launch tube. I have no proof that this improves performance, but my hunch is that it does. My brain suffered a moment of extreme ingenuity at this point and I painted this little disk bright orange so that it would be easier to find after launch. I can pat myself on the back for figuring out that little trick, because it took several minutes to locate the disk after launch even though it was bright orange and it would have been lost for sure if it was unpainted. I think there may still be some hope in this world that I will one day succeed... doin' sumpthin', I suppose...
PROs: Simple construction. Enjoyable assembly with clear instructions. Fin assembly fits both ways and still seems to work just fine. Website has an excellent tutorial for those bright enough to check it out prior to construction. The launch system provides the possibility for a variety of modifications that will be cheap and simple.
CONs: Shock cord is too short. Fin assembly does not come with an automatic doofus alarm to warn you that your brain is switched off and that you are about to install the fin assembly upside down.
Following construction I decided to finish Flippifin in colors that go well with the neat little decal that comes with the kit. It has kind of an all-American red, white, and blue scheme, so I decided to go patriotic and paint Flippifin like a flag. After completing most of this process, it occurred to me that I had in fact, produced a reasonable facsimile of the French flag. The Flippifin decal matches nicely, and I am quite proud de mon petit oeuvre d'art. The paint job consisted of a coat of primer, a light sanding, and enough of the three colors to make it look right. I think I pretty much just used one coat of each. As the instructions indicated, I was careful not to paint the fins. I will once again point out my stroke of genius when I endeavored to paint the floating centering ring bright orange.
Construction Rating: 5 out of 5
FLIGHT: Construction mishaps behind me, I set Flippi-Doodle aside and waited for the chance to launch it. I waited with increasing impatience as the long hot days of August and September ticked by in Utah. Perfect flying days number fewer than 300 per year here and I did not want them all to pass me by before I had a chance to test out the tube launcher and the folding-fin contraption. I finally put it to the test in late September. There was a gentle breeze from the Southeast, visibility was less than 50 miles but still quite respectable, and I think there might have been a cloud at one point but the sky otherwise suffered only from a distinctive desert shade of blue.
I had some ACME conformal launch lugs on the launch tube so that I could place the tube on a rail well away from the flight line at a club launch. The rail was about 10 feet tall, and I was afraid that the fins might tangle in the rail slot if the rocket exited the tube alongside the rail. Thus, I taped the tube high on the rail with the mouth of the tube above the top of the rail. Unfortunately, the force of the launch on an E30 knocked the tube down the rail, ripping off the lugs, and smashing the plywood flanges at the rear where they collided with the blast deflector. No serious harm was done though. In the final analysis, I think the tube can just be taped to any old launch device or pole stuck in the ground so long as it is secure. I never saw any hint that the fins might tangle in the rail, but I suppose it is possible so some measure should be taken to prevent this. The rear of the tube should definitely rest on a firm surface. It was not good to suspend the tube like I did on the first launch.
The first launch on the AT SU E30-7 was surely a fine sight. I don't know exactly how fast I should expect this rocket to leave the ground on this motor, but it shot out of the tube with surprising speed and a muffled kind of a pop. The floating seal ring was recovered, the launch system rigged again in a sturdier fashion and the second launch was on an AT SU F21-8 Econojet. The launch was again perfect. I do not have an altimeter since I destroyed mine recently following a moment of brainlessness, but I suspect that Flippi-Doodle went well over 2000 feet. The speed and suddenness of takeoff are satisfying.
I read in the instructions and on EMRR that the rocket will get coated with soot from the launch. The floating seal ring seems to prevent this. As seen in the pictures, after two launches, the rocket is clean (I did not wipe it off after the launches) but the seal ring is filthy. For this reason alone, even if the ring does not improve performance, which I still suspect it might, I will continue to use the floating seal disk as described. I think I will cut several of them because it can be tricky to find them after launch despite the bright color.
PROs: Launch tube system worked well. Rocket flies incredibly fast and straight as an arrow. Reversing the fin can did not seem to make the rocket fly backwards...
Flight Rating: 5 out of 5
I give Flippifin my highest possible marks. This kit is simple and can probably be flown without ever pondering the possibilities that exist if one was to experiment a little with the rocket and the launch tube. I think that this rocket is as safe to launch as any mid-power or high-power model rocket out there. My experiences with this kit exceeded my expectations. I plan to fly it again and again.
Overall Rating: 5 out of 5