LOC Viper III tailcone

[Mr G]

Never liked the abrupt transition from one to three, so a nosecone was cut up to taper tail end. Bit of a hack job so lots of filler. Won't be pretty but with three Estes E9-4s, it may no last very long anyway. If it does, there are another 5 flights-worth of E-9s to burn. Added a threaded rod at the bottom for motor retention and a screw eye at the top for the 1/8" Kevlar shock cord. Another screw eye was installed in the centering ring as a back up if the center one doesn't hold.

E-9s sim apogee in Open Rocket at 612 ft. Might try E18Ws (1,290 ft) or F24Ws (1,734 ft).

 

[Mr G]

Question - will reduction in drag from the transition make much difference? It did add some extra weight.

Has anyone else tried something like this?

 

[Tim51]

I've never built a boat tail but I did run a few OR sims a while back when considering one for an HPR project, and adding the transition did make a noticeable difference in simmed alt, even with the added weight, so it is something to seriously consider. If modelling the transition of your cluster Viper build in OR is too complex, I suggest running sims on a simpler design of similar weight and diameter with and without, and calculating the differentiating factor.
Cool build!

 

[JDcluster]

It may look nicer but, the base drag reduction helps more at higher speeds.

 

[Mr G]

Exterior completed with first coat of primer. Not bad looking from 10 feet away.

 

[Theory]

i like it!

had a viper IV back in the day and i really like what you did here

 

[Mr G]

Done.
Shakedown flight may happen at October Skies - the next local launch.

 

[Wallace]

I like it! Looks like a perfect application for a 3d printed part.

 

[mbeels]

Really nice, that tail cone adds a lot!

 

[cerving]

Nice! I have a Viper III, and yeah, the transition is kinda ugly. Did you have to add any ballast up top to offset the weight of the boattail?

 

[Mr G]

Open Rocket shows 3.4 calibers with no motors, 2.3 with three E9s and still 1.5 with three CTI G127s. So, even with the boat tail, nose nose weight is not necessary.

 

[Nytrunner]

Now you get to find out how far you overshoot your sim with the boat tail hehehe