Modification - MonoGoose {Modification} Modification

Contributed by Larry Brand

Manufacturer: Modification
Style: Sport

MonoGooseBrief:
I have re-designed the Estes Mongoose as a single-stage 24mm, minimum diameter rocket I call the MonoGoose. It utilizes the kit's two plastic fin assemblies to create a strong, diamond airfoil fin can. MonoGoose can be flown on D12's, the new Estes E9's, E15's or any 24/40 reload.

Components:
To the packaged components of an Estes Mongoose all that is required to build a MonoGoose is two additional Estes 24mm x 18" tubes. One of these is used to build the epoxy-laminated motor tube that forms the base of the rocket.

Construction:
The usual excellent Estes quality and fit of parts. The MonoGoose actually goes together much faster than a stock Mongoose. One hour does it, easily, except for painting. I happen to prefer attaching recovery systems through the hull, about 1-2" below the bottom of the nose-cone. The knot retaining the shock cord is covered with half of a BIC pen cap, sawn lengthwise.

Modifications:
The MonoGoose is built by first grafting the two kit fin assemblies tail-to-tail using the long green adapter tube supplied with the kit (see diagram). I used 5-minute epoxy throughout. Take care to be sure that the fins are exactly aligned to create a perfect diamond airfoil. The body of the rocket is built by gluing the yellow tube provided with the kit to one end of the fin can, and then extending this by adding another 18" section of 24mm Estes tube, using 2" of 24mm tube as a coupler (it is slit lengthwise, and a 1/8" sector is removed, allowing it to be inserted into the two body tube sections. The process can be repeated for additional strength. The Mongoose kit nose cone is mounted per the packaged instructions, along with the recommended recovery system.

Combine the Fin CansThe motor tube is fabricated from 24mm Estes tubing as follows: three 4.25" lengths of tubing are prepared, and two of them are slit lengthwise. Cover the exterior of the intact section with a thin layer of 5-minute epoxy mixture, and slide one of the slit sections over it, doubling its thickness. Let the epoxy harden, and repeat the process with the second slit section, adding it to create a triple-thickness, epoxy laminated motor tube (make sure the cuts are on opposite sides of the tube to assure strength).

Now complete your MonoGoose by simple gluing the motor tube to the remaining end of the fin can. An Estes motor hook is added by gluing with epoxy to the exterior of the motor tube, leaving it to extend about 3/8" beyond the bottom. No glue is applied to the bottom 3/8" of motor tube so the retaining hook can be bent a bit when inserting a motor. I use an extra long Estes motor hook, and bend the top straight with a pliers so it sits flat on the motor tube. Wrap the retaining hook to the motor tube with a little fiberglass cloth tape and epoxy -- I just used duct tape, since I'm lazy, and paint covers it anyway. Add a 3" length of Estes soda straw centered 6" above the fin can (above and and between the fins) as your launch lug; this is the balance point. Remember that with the motor in the atypical position, behind the fin can, even a long rocket like this could become tail heavy. I painted my MonoGoose battleship flat gray, except for the nose cone, which I left in that awful Estes Mongoose pink to show its heritage.

Tail EndYou're ready to fly. Use a D12-5 to start. You'll get about 1300', with somewhat premature ejection. The thing coasts forever. A D12-7 is perfect, and the MonoGoose will show you a twirling tail-slide until the chute takes hold. Be warned that an E15-7 will take the light-weight, minimum diameter MonoGoose out of sight to 2500' or more. I wouldn't risk losing a reloadable 24/40 RMS set-up E18-8 or F24-9 without a suitable flying site. The MonoGoose survives 450 mph E30-7 launches, but simulations show the height gained is virtually identical to that with an E15, so why bother. I like to use 2 feet of 3/8" elastic and 5 feet of parachute cord on the 12" Estes chute for a recovery that looks like a much bigger rocket -- until it lands.

Flight:
You gain a quick-building stable high-flyer at the expense of the "excitement" of a two-stage, which to me means that you don't have to worry about losing the tumble recovery first stage that everybody eventually experiences with a Mongoose.

You gain the ability to fly on either Estes or Aerotech single use or on Aerotech 24/40 reloads, so this is an excellent training rocket.

Flights are arrow-straight up, with little weathercocking or influence of wind. The 12" chute is as much as I would use on this 47" rocket. It comes down like a propeller on its 7' of cord and elastic. The epoxy laminated motor tube has held up superbly to landing impacts.

Summary:
PRO- A great fun-fly and training rocket, with maximum performance for minimum cost and construction fuss, plus its unusual and it looks cool with its aft-of-fins motor mount. (see picture). Flies on a range of low-cost 24mm D, E and F motors.

CON - With its length and thin Estes tube construction, one has to be careful not to dent or bend it on storage or transport. But it holds up superbly to flight stresses.

I built the motor tube to accommodate the new long Estes E9 motors. But since I fly it mostly on 24x70mm motors, I slide in to the top of the motor tube a motor stop a 28mm spacer sawn from a used D12 motor.

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