Ye Olde Rocket Forum - View Single Post - Scrounged-Up Designs 2006

Quote:

Originally Posted by CPMcGraw

Talk about procrastination, I've had this rocket sitting off to one side for so long, I've forgotten how long I've had it. Maybe six years...

The LHS had this LOC Viper 4 in stock probably since the day they opened, and that was long enough for the price sticker to fade, yellow, and crack. I'm not really sure why I bought it, other than I was just looking for "something bigger" than a typical modroc. I didn't particularly care for the fin shape of the Viper, but figured I might find a better fin shape sometime in the future...

Well, it's "Back to the Future" time, and the inspiration is a combination of several EnerJet fin patterns, with a contribution from not just a few Estes models...

The ViperJet 4256...

Length: 45"
Diameter: 2.63" (LOC 2.56)
Fin Span: 12.06"
Weight: 15.5 oz

This is a high-performance cluster model, requiring four (4) 24mm motors. All motor combinations (except the poor E9-8) will reach flight V on a 48" rod, 1/4" diameter.

(4) C11-3..................270'......20 FPS......Margin 4.18
(4) D12-5..................783'......23 FPS......Margin 3.97
(4) D15-6..................992'......11 FPS......Margin 3.93
(2) E9-6 + (2) D12-7......1112'......36 FPS......Margin 3.69
(4) E9-8..................1438'......30 FPS......Margin 3.45 (Needs 56")
(4) E18-8.................2305'......27 FPS......Margin 3.58
(4) E6-8..................2347'......28 FPS......Margin 3.86
(4) F72-10................3879'......47 FPS......Margin 3.31
(4) F32-10................4252'......32 FPS......Margin 3.17
(4) G37-10................5277'......56 FPS......Margin 2.81

The LOC 50" nylon parachute is used for recovery. Use birch plywood, 1/8" thick, for the new fins. All Dv values above 25 need to have their parachute lines reefed to prevent an explosive opening, which may result in a shredder...

Enjoy!

Hey, nice design Craig

I really like your ViperJet 4256 and saved it with my other RockSim files!
The Loc 2.56 dia tubing is fairly thin walled and your design for such a large rocket at only 15.5oz moves out pretty well on the black powder motor clusters

I always really liked the Loc Viper III and IV kits but found the Viper IV the more versatile of the two because it could be flown on 2 or 4 motors. Although I have never owned either kit a very good friend of mine has the Viper IV and has had many good flights using chad staging of 4 D12-0's to 4 D12-7's.

Do you have a RockSim file for the Viper IV standard kit that you could post? I'd like to build 4 dummy motor tubes into the design to make it two stage and see what the DV's and altitudes are with 4 D12-0's staged to 4 D12-5(7)'s.

No doubt in my mind that Ron Schultz with Loc was thinking EnerJet 2250/2650 when he designed those two Viper kits .....