Bruce Bell's 41 pound Big Dog is over 6' tall and 10" in diameter and is made from pre-fiberglassed tube. For the primary electronics Big Dog utilized a Perfect Flite Alt-WD and a G-Whiz LCX as backup. Recovery was via a drogue 36" parachute at peak altitude and a 12' main chute at 1,000' agl.
BigDog lifts off under power of an Aerotech M1419 to a successful Level 3 certification flight. The altimeters reported altitudes of 9,120' and 9,132'.
|The upper part of the 98mm motor mount tube in Big Dog houses a piston tube to eject the main chute. To help strengthen the tube, fiberglass tape was epoxied to the tube. Bruce used a combination of West Systems 105 Resin and 207 Hardener. Note that this combo AT ROOM TEMP (75 degrees) will allow a working time of more than 30 minutes. However, according to Bruce, "as I found out, working in a shed in 98 degree temps, the working time was reduced to about 15 minutes!"
You can do several things to offset this, work early in the morning when it is cooler or, apply a little less hardner (West Systems advises against this as the incorrect mixture will make the epoxy brittle) or go with the 209 Hardner which has a working time of more than an hour.
|On the upper centering ring is where the parachute connection U-bolts are located. Most kits use one u-bolt, however I went with two so that the drogue chute and main chute would be separated on opposite sides of the motor tube, minimizing the chance of a tangle.|
|BigDog lifts off under power of an Aerotech M1419 to a successful Level 3 certification flight. The altimeters reported altitudes of 9,120' and 9,132'.|