Friday, January 29, 2010

Viper IV build thread part 1: the parts

Because I'm bored, and it's my fervent but misguided hope that there's at least one person on planet earth who is interested (and also cause it'll help write the EMRR review), I present the Viper IV build thread.

I might cross-post it on TRF. Basically depends on if I feel like it tomorrow.

(note on abbreviations: LOC-Precision, here just 'LOC', is the company that makes the kit, including all the components. PNC = Plastic Nose Cone; BT = Body Tube)

Without further ado, what actually came in the bag:

  • Nose cone: 3.5:1 plastic ogive PNC-2.56, color off-white. The shoulder is 2.5" long and includes a molded eye for shock cord attachment. It's standard-issue LOC thick-walled plastic - 112g (3.95 oz) accoridng to Apogee, and has raised ribs on the seams.
  • Body tube: 30" of LOC BT-2.56; 2.56" internally and 2.63" externally weighing 139g (4.92 oz). The tube is thick-walled and high-quality, with an outer glassine wrap for strength and ease of finishing. The spirals are tight and shallow and will not interfere with finishing.
  • Coupler: 3" of LOC 2.56" tube coupler; 2.479" internally and 2.555" externally weighing 11.8g (0.41 oz). It is also thick-walled and made of kraft paper; it is used to fit the 4 motor tubes into the rocket. Formerly Viper IV kits contained 2 plywood centerting rings, but those tended to snap durign sendign hence the change.
  • Motor tubes: 4 lengths of LOC 24mm motor tube, each 12" long and in total weighing about 1 ounce. As well as the motor mounts, they are the entire aft end of the rocket.
  • Fins: 4 plywood fins each 1/8" thick and total weight about 2 ounces. The root is 5" long, the tip 2", and they they're 4" wide. The plywood is incredibly high quality - very strong, and just 2 minutes with 120-grit sandpaper and steel wool makes each fin smooth on the faces and glass-like on the edges.
  • Shock cord: 8 feet of 1/4" flat elastic for the shock cord plus a short length of nylon to mount it to the wall of the tube. Not incredibly strong, and below Madcow quality, but good enough.
  • Parachute: 18" diameter circular black ripstop nylon parachute with 6 medium-length sewn-on nylon shroud lines. High quality and able to stand up to abuse; however, there is one tear in the edge sewing that is mostly merely cosmetic and takes 10 seconds with a sewing machine to fix.
  • Launch lug: 6" of LOC 1/4" diameter launch lug. Decent quality.


To which I will likely add the following:

  • Quick-link: simply to aid in changing the parachute.
  • Motor retention: threaded rod between the motor mounts plus a few assorted nuts and washers. Will prevent the ejection charges from pushing the motors out instead of the parachute.
  • Chute protector: 9" piece of aramid (Kevlar™) cloth that does not burn, to protect the parachute from the heat of the ejection charges. Will add with a quick-link to allow use on multiple rockets.
  • Rail buttons: to allow launching off launch pads with launch rods or launch rails.


The total height is 9 + 30 + (12-3) = 48 inches tall. My second-tallest rocket after the Nike-Apache, my third cluster (after the Twofer and Multi-Goon), and my first 4-motor cluster.

Pictures, simulations, and actual building coming soon.

4 comments:

brett said...

It is a cool rocket. Are you planning on using black powder or composite 24mm motors?

One of my winter projects that I may or may not get to is a 4x29mm assembly in a 3" tube that I built a while back - I just need to build the rest of the rocket!

KenKzak said...

You have internal and external BT diameters transposed.

What method do the instructions recommend for plugging the gaps around the motor tubes?
The original centering rings were delicate, and no doubt difficult [read expensive] to produce before lazer cutting.

I had a Viper IV many moons ago. Flew it many, many times before hanging it up in a local pizzaria.

I don't recall if mine had an all- thread stud between the motors, though it should have. I've done it to plenty of other clusters though.

The EGE said...

Brett: definitely blackpowder. D12-5s are cheap and easy to ignite; composites unfortunately aren't. I may try a pair of Es or Fs later, though.

Ken: no I don't. 2.63" > 2.56"

The instructions recommend tissue and epoxy. I may use balsa too simply cause I have a lot.

KenKzak said...

My bad on the diameters.

On plugging the gaps.
I suggest bits of Pink 'glass insulation. Stuff in dry wads of it and tuck it into the corners with a pointy stick or pencil, maybe 1/8" below the end of the coupler, then pour in a bit of epoxy and spread it around.
15min epoxy would allow reasonable soak in, without soaking through and running out the other side.
More conformable than tissue so less chance of run through, and stronger.