Binder Design Sentinel (54mm)

Binder Design - Sentinel 54mm {Kit}

Contributed by A. Jeffrey Goldstein

Construction Rating: starstarstarstar_borderstar_border
Flight Rating: starstarstarstar_borderstar_border
Overall Rating: starstarstarstar_borderstar_border
Manufacturer: Binder Design

Binder Design Sentinel

Brief:
Built as specified, this single stage rocket from Binder Design with 54mm motor mount and a planned parachute recovery at apogee separation totally dependent upon the motor's delay charge. The rocket stands 7' tall and is quite impressive, even for a 4" rocket. This is quite a nice project for a Level 2, although it could be flown for both Level 1 and Level 2 qualifications. 54mm Motor Mount is recommended since the user may want to put larger motors.

Construction:
I used 38mm motors with PML's 54/38 Heavy Duty Adapter. No problems here. Very reusable and easily removed to allow for 54mm motors.

There were two 34" paper body tubes, originally. I thought some of the parts were quite inferior such as the 1/16" masonite bulkhead holding the eyelet and the stock 48" Binder Design parachute with inferior threads holding the risers to the ripstop nylon. Were these items of higher quality and strength, my failed level 2 attempts would surely have been successful.

I'm sure this would be a much sturdier kit if the tubes were phenolic or Quantum Tubing. I think strength is important in a kit like this.

The instructions in the Sentinel kit were very complete and detailed. I have no complaints about these. Only the parts that were given (as described above) were inferior. I used 30 minute epoxy in most all of the joined parts.

With my first failed attempt having a ripped bulkhead and torn body tube, I purchased a 3.9" x 36" Quantum Tube by PML. This was far superior to the phenolic given as evidenced by the Sentinel's unintentional streamer recovery without a scratch.

No special tools were needed for this project, however on the down side, the body tube fin slots had to be cut for each fin to fit through-the-wall. Binder Design provided the lines for the hobbyist, but leaves the cuts to the builder. These cuts were not only tedious to do, but they were also difficult to cut in a straight line. It really made me appreciate body tubes that were pre-slotted for through the wall fin construction.

My heavy epoxy fillets made up for the imperfections in straight fin slots that I made. Of course, no one will notice these cuts once the fins are epoxied and painted.

Finishing:
Decals were provided, however, Binder Design's quality control had inadvertently omitted the "I" in "Sentinel". My first attempt had the "SENT NAL" decals on it.

I painted my Sentinel in gold with orange fins and an orange nose cone. This looked striking against the blue sky with the Red flame of the AT420R.

Construction Rating: 3 out of 5

Flight:

RockSim has recommended the optimum delay of 10 seconds for the J420R, however, my first two level 2 attempts ejected 4 seconds prematurely, despite each package marking for a medium (10 sec) delay.

For the Sentinel's first flight on a J420R, the short delay of 6 seconds caused separation between the nose payload section and the booster section. The force was far too great to hold the 1/16" masonite bulkhead provided with the kit. I figured that separation occurred at 150 MPH. The bulkhead separated with the eyebolt and center section of the bulkhead parachuting safely to the ground. The nose and forward body tube were found buried 3' into soft tilled soil.

A second attempt was made one month later with similar problems in Aerotech's delay charge. After 6 seconds the premature separation this time caused Binder's stock parachute to separate at all risers except for one. The RCO and all of us thought the chute was tangled. It was actually an unplanned streamer recovery. The rocket landed without a scratch, but the parachute had to be repaired.

Having bought a new 45" parachute from our vendor and this time a Cesaroni J400 (delay was personally set by me at 12 seconds), the flight went flawlessly, and I earned my NAR L2 certification finally!

All launches went perfectly straight from the launch. I noticed that in each of the flights there was a "whistling" probably from the launch lugs. All flights were awesome, except for the early separations.

Recovery:
After the first attempt, I added about 15' more bungee to the 12' Kevlar shock cord that was supplied with the kit. I think longer bungee should be supplied for less than optimal apogee (motor delay dependent) recoveries.

Flight Rating: 3 out of 5

Summary:
PROs: Overall a very good choice for a Level 2 rocket. Not a difficult build. Very sturdy booster section. Awesome off the launch pad!

CONs: Binder Design's parts (masonite bulkhead, centering rings, and parachute) as described previously were inferior for a kit of this size. These parts need to be beefed up to allow for less than optimum recoveries. Also, the stability of the rocket is marginal (from the stock parts). Only about 0.7 Calibers (marginal).

Overall Rating: 3 out of 5

Flights

Comments:

avatar
Mike Fisher Binder Design (July 30, 2004)
This sounds like one of our older kits before I owned the company. None of our newer 54mm kits have come with masonite centering rings for several years now. When they did, it was 1/8", not 1/16" like the review suggests. It also sounds like the parachute was from our old supplier, "Top Flight" or "Pacific Winds". Our newer chutes are very strong, with double sewn lines on the canopy. The kit now comes with 18 feet of tubular nylon, not 12 feet of Kevlar® as stated in the review. Thank you
avatar
M.F. (December 27, 2004)
I'm not sure where the kit in the review came from, as the reviewer mentions a lot of parts that have never been included in this kit. The review mentions a 48" chute was supplied. We have never manufactured a 48" chute, so I'm not sure where that came from. The review mentions that the centering rings were 1/16" masonite. Not only have we switched all of our 54mm kits to plywood centering rings, but when we did use masonite, it was 1/8". Twice as thick as mentioned in the review. The review mentions the use of 12' of Kevlar®. None of our kits come with Kevlar®, only generous lengths of mil-spec tubular nylon. I can only assume that either the kit reviewed was re-packaged with non standard parts, or that the review is wildly inaccurate. Mike Fisher, owner, Binder Design

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