Binder Design - Excel Jr. {Kit}

Contributed by Kevin Johnson

Manufacturer: Binder Design
Rating
(Contributed - by Kevin Johnson - 11/01/02)

Brief:
Smaller version of the popular Excel rocket.

Construction:

  1. 2.6 inch pre-slotted BT
  2. 2.6 inch payload bay coupler and bulkhead
  3. 29mm motor mount
  4. Plywood TTW fins and centering rings
  5. Lots of tubular nylon
  6. 2 quick links and eye bolts
  7. 18" nylon parachute
  8. Plastic nose cone
  9. 3 plastic rivets
  10. 2 vinyl decals
  11. * 29mm Motor Collar retainer- was included as a special in my kit

This kit was one of the best packaged kits I’ve ever purchased. The sub assembly components were all sealed into individual sections of a large heavy gauge plastic bag. Even the instructions and decals had their own pocket, making it so you could see at a glance is everything was there.

The instructions were a booklet of 8.5 x 11-inch pages with photos and illustrations of the major construction steps. The directions were easy to follow and didn’t include any gotchas. They even pointed out a couple of areas that could cause trouble, like securing the shock cord quick link to the motor mount before epoxying it in place.

The fins and centering rings needed no fine tuning and slid into place with no trouble. This is the first kit I’ve built that uses eye bolts and quick links for recovery. This is also the first kit I’ve built that used plastic rivets to keep the nose cone and the payload bay together. I used 15 minute epoxy throughout the construction, and this well designed kit went together very quickly.

Finishing:
For finishing, I decided to paint the payload bay and nose cone Popcicle Orange, and the rest of the airframe and fins white. I used Painter’s Choice paints from Home Depot. The fins needed a few coats of primer and some sanding to fill the minor grain in the plywood, as did the spiral on the body tube. Make sure you sand and wash the nose cone prior to painting to help your paint adhere to the plastic surface.

After the paint had dried, I peeled off the backing strip for the decals and pressed the exposed adhesive to the body. Two decals are provided, an EXCEL and a Binder Designs logo. They both were of excellent quality and I had no trouble applying them. I gave the rocket a final gloss overcoat to seal the decals to the body.

I can’t think of anything I would change in the construction or finishing of this rocket.

Construction Rating: 5 out of 5

Flight:
Binder Design says that the Excel Jr. can fly on motors from D to G impulse, but doesn’t list any specific motors. They do provide RockSim stability information to allow you to adjust the CG/CP relationship for the motors you choose to fly.

I have flown my Excel Jr. on Econo-Jet G and F motors with no additional ballast needed.

Flight prep begins with prepping your motor. For Econo-Jets, you MUST peel the sticker off and make sure there is no residue on the casing before inserting the motor into the mount. I haven’t tried any other single use motors, but my RMS casing slides in with no trouble. I also had to add a tape thrust ring to the aft end of the motors as the Excel Jr. doesn’t use a thrust ring in construction.

I added a Pratt Hobbies Kevlar® shock cord sheath to protect the tubular nylon from hot ejection gasses. I found that with the size of the body tube, this product is all the protection the shock cord and parachute need.

Motor retention on my Excel Jr. was provided by the Binder Design Motor Collar. This is an aluminum sleeve that is bonded to the rear of the motor tube that extends about an inch aft of the motor tube. A snap ring slips into a groove after you insert the motor to keep it in place.

All of my flights with this rocket have been arrow straight. The Excel Jr. really flies well and leaps off the pad under G power.

Recovery:
I’ve had a couple of recovery mishaps with this rocket that were of my own doing, and not the fault of the kit or it’s design. One flight I used a delay that was too short and popped one of the shroud lines, and on another I packed the chute incorrectly and it did not deploy. No damage was done to the rocket in either of these instances.

Flight Rating: 4 out of 5

Summary:
I was very impressed by the quality of this kit’s packaging and design. The Excel Jr. is a great combination of style and size that fits for the smaller fields that I fly from and also fits in my small car.

Overall Rating: 4 out of 5

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