"What-A-Drag": A funnel fin rocket

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lalligood

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My latest project is a rocket that uses a couple of funnels in place of fins. There was a review recently for a similar design on EMRR & it inspired me to build one for myself. I'm also a big fan of saucers & Qubits so why not combine the most recognizable features of saucers & rockets into a single design???

Construction was very simple. 38mm MMT inside of 2.6" diameter tube. Zipperless airframe with recovery equipment stored in the payload bay. There are 2 funnels--one main funnel with a 7.5" diameter supported by a funnel underneath facing the opposite direction (used to take the place of gussets). While I am a HUGE fan of rails (& rail buttons), there was not an easy way to do this without making it u-g-l-y, so that means using lugs. One lug is mostly hidden inside the funnels & the other is further forward.

One challenge I really wanted to accomplish was not using ANY epoxy (yeah, you heard me right!) Unfortunately, I succumbed to using a very small amount for the lug fillets. I just didn't have anything that would have done as good a job filling in the area around the lugs & providing strength.

I don't have a nose cone yet but I'm planning to get a LOC 2.56 in the next few weeks. Total length will be 63" & should weigh in at about 2 pounds. Plans are to fly it on 3-, 4-, & 5-grain Pro38s. It's hard to get RockSim to give an accurate altitude (which is pretty typical for high drag designs) but I figure that it'll need a big push so that it has enough time for even a short delay to burn off before ejecting the chute.

First picture here is with my Phobos for scale & I borrowed the upper tube & NC from my tube fin rocket, Tube-a-licious, to have a good idea of the finished product...
 

lalligood

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Next picture is a close up of the aft end. You can see the lug & how the funnels fit together. I lightly scuffed the funnels so I can paint the entire rocket flat black.

BTW, the funnels were procured in the automotive section at Wal-Mart. They were less than $1 each. I used the shroud template generator at EMRR to help judge where to cut the funnels & then got them to shape with a Dremel. Funnels were attached with CA & Gorilla Glue (which sticks to anything!)
 

cls

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pretty cool! I am sure you won't ever pop a funnel from a hard landing :)
 

lalligood

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Originally posted by teflonrocketry1
This design looks similar to the Rouge Aerospace deep Surface Probe, the RockSim file I made for this design is posted at:

https://www.rocketreviews.com/rocksim/OOP_Roguedsp2.RKT

Your design should fly good on the motors you mentioned.

Bruce S. Levison, NAR #69055
The great composer Igor Stavinsky once said, "Good composers borrow; great composers steal."

The Rogue Aerospace Deep Surface Probe was indeed the inspiration for the funnel within a funnel design. It also saved me the trouble of cutting, sanding, and gluing plywood gussets. Laziness breeds innovation :p

BTW, Bruce, don't know if you read my PMs or not but I re-ran my design in RockSim today. The delays (from motor burnout to apogee) are still very short, but a J350 puts it up around 1200 feet. I want to really put this rocket through its paces but an upscale sure sounds attractive, especially since there are more long burn motors available in the 54mm range. (Anyone know where I can get some really big funnels?!?) And speaking of long burn motors, an H45 puts my design over 1100'...just gets it there a lot more slowly! Well, if I could get my hands on an H45 :rolleyes: And thanks for the link to the RockSim file.
 
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