Scratch E-Qualizer Original Design / Scratch Built

Scratch - E-Qualizer {Scratch}

Contributed by Larry Brand

Manufacturer: Scratch
(Contributed - by Larry Brand - 11/10/04) (Scratch) E-Qualizer

Brief:
I built the E-Qualizer as one of four experimental designs used for my NARTREK Gold project. Only one survived the required 6 test flights and E-Qualizer wasn't the one. E-Qualizer was an exercise to create a model optimized for the long-burning, heavy, low initial thrust Estes E9-8 motor. It combines narrow diameter and light weight with both conventional and tube fins to move the CP well towards the aft end to balance the heavy motor. I have since found better ways to do this. All that aside, it is a fun model to build and fly, which is why I'm sharing it.

Construction:
To keep the experiment simple, I built E-Qualizer by re-combining the components of the Custom Rockets Razor and the Vaughn Bros. TFNC kits. Unfortunately, the excellent Vaughn product line is no longer available.

E-Qualizer is a deluxe design including G10 glass fins, a payload compartment large enough for a Perfectflite micro altimeter, and a nylon chute recovery system attached with a mini-carabiner.

Construction uses 5-minute epoxy (no Elmer's glue) is as follows:

  1. Build the Razor airframe as per the instructions, omitting the nose cone attachment and motor mount. The fins are also attached 1 1/4" forward of where the plans show.
  2. Build the TFNC airframe as per the instructions, omitting the fins and motor retention.
  3. Graft the two units together with the TFNC on top and using a coupler consisting of 4" of 24mm tube coupler stock. I make my own by double laminating two lengths of slit 4" x 24 mm Estes tubing with epoxy.
  4. (Scratch) E-Qualizer
  5. Add the three TFNC G10 fins to alternate valleys of the tube fin array. Epoxy a straightened long Estes motor hook through the space between 2 tube fins, such that a retained motor will protrude about 3/8". Place the TFNC launch lug centered 3 1/4" above the tube fin can and precisely aligned with the space between the two tube fins opposite the motor hook placement (the 1/8" launch wire has to pass through here).
  6. Add recovery system to the lower section using your preferred attachment or the system and method that comes with the Vaughn TFNC. I prefer 6ft of parachute cord over the underpants elastic that comes in the kit and a 12in "lite" Top Flite chute.
(Scratch) E-Qualizer

E-Qualizer is pictured with the other 3 rockets used in my NARTREK Gold project (pictured left to right are Quest-4-Estes, PipeCleaner, Mongoose, and E-Qualizer). The other three designs are all found in the EMRR website and you can read more about the NARTREK Gold project in the SPORT ROCKETRY May-June 2004 issue.

Finishing:
Finishing was with Testors flat battleship gray primer spray and red for the payload section.

Flight:
E-Qualizer boosts straight and briskly on the E9-8 and D12-7, even with a breeze. Altimeter reported 1240' on the E9 and 740' on the D12, which works out to a rough drag coefficient (Cd) of 2.2 or so for the design, a bit high even by tube fin standards. I was only able to get 2 measurements before a crash ruined the altimeter. E9-6 and D12-5 are also possible motor choices but eject a bit early. I nearly lost it on a single flight on an E30-7--super fast, out of sight, and appeared to be climbing to at least the 1500' at 390 mph predicted by simulation. I was afraid of a shred and too chicken to fly it with my MicroAlt in the E30 flight).

(Scratch) E-Qualizer E-Qualizer flies pleasantly on C11-5 motors as well, equivalent to the performance of an Estes Big Daddy (350'). I have so far resisted the urge to fly E-Qualizer on an F21-8 as simulations predict nearly 2000' at 400 mph. It would probably survive structurally but a water landing would be a certainty at our island field here in San Diego.

(Scratch) E-Qualizer I have been experimenting with an all-PVC, 29mm version of E-Qualizer to fly on G/H-power as well. First test flight on an E30-7 (with adapter) was perfect, however, the second flight CATO'd the E30 (front closure failure) and spectacularly torched the PVC rocket body (PVC would make a good nitrous hybrid motor, maybe). R&D continues.

Summary:
PRO: A good fun fly rocket, and easy to build. Flies the E9-8 without nose weight despite weighing only 88 grams. Very stable in wind.

CON: Vaughn kits no longer available, but could be scratch built from parts. A small rocket, thus can be easily lost if flown over 1000'. It is also unnecessarily draggy (way too much fin area) but I have since found better ways to achieve good performance combining light tube fin designs flying heavy motors.

comment Post a Comment