Manufacturer: Yank Enterprises
Rating
(Contributed - by Jon Hatch - 08/10/02)

Pic Courtesy of YankRocket Pic

Materials:
All parts were accounted for, except for a Yank Enterprises decal, which was advertised but not included. As this was a scale rocket, I had no intention of using it anyway, so this was no loss. The kit consisted of 2 lengths of 3" flexible phenolic body tube (34" & 31" long), one of them slotted for the aft fins. The forward BT was supposed to be marked for the forward fins per the included instructions, but was not (no big deal, as it's not that difficult to make a fin guide with any graphics program). Also included were 1 30" ripstop nylon parachute, 20 feet of 9/16" tubular nylon, 2 quick-links, 2 eyebolts w/ washers, tube coupler, one birch ply bulkhead, 2 baltic birch ply centering rings, a 38mm motor mount, ogive nose cone, and 8 1/8" 5-ply baltic birch fins. A couple of the aft fins were slightly warped, but I attribute this to the kit probably sitting in the hobby store basement for a considerable amount of time, as the masking tape also left marks that no amount of sanding would remove. All parts were very high quality and fit well together, although with an assembled weight of 60 oz, I thought 3/16" or 1/4" ply would have been more appropriate for the aft fins, as they sweep back past the aft end of the rocket.

Materials score: 4 out of 5
Pros: Very sturdy BTs and nice hardware
Cons: Aft fins are a little thin and the parachute might be a size small (the website says they now ship 36" chutes) for the weight of the rocket.

Construction:
Instructions were thorough if small, with one exception. They did not specify at the appropriate step exactly how far forward from the BT junction to put the forward fins. I guessed at 1" and after looking at the scale finishing directions, I believe this to be correct. I decided to go with an anti-zipper design as detailed in InfoCentral on Rocketry Online, which changed my construction considerably from the directions.

I drilled eight 5/16" holes in the bulkhead, which was pre-drilled for the eyebolt assembly. I attached the eyebolt assembly (washers were included) and epoxied it into the coupler tube with a heavy fillet around the outside.

The forward BT needed to be slotted, and took a bit of time, as there are a lot of layers to cut and peel. Since I would be cementing the coupler to the lower BT instead of the upper, I cut the slots a touch short and pushed the fins through the back in order to get a very tight fit before running fillets along the outside joints with 30 min epoxy.

On to the motor mount. After cementing the forward centering ring 1/4" from the front of the MMT as directed and cementing it to the BT, I realized that I should have gotten a 3rd centering ring to add right in front of the fins. The instructions said to cement the aft centering ring immediately and to simply run a bead of epoxy to the fin root in order to affix the fins to the MMT. I chose to run fillets instead and held off on cementing the aft centering ring until that was done. Since I didn't have a CR at the front of the fins to serve as a dam for the forward end of the fillets, I used 5 min epoxy for the internal fillets. I then used 1.5 oz glass to reinforce the fins and ran some very heavy outside fillets using 30 min. epoxy.

After putting blind T-nuts in for retention, I saw that I didn't have a whole lot of room to fillet the aft centering ring to both the MMT and the outer BT, so I decided to just go with an epoxy well. To protect the T-nut opening, instead of using tape and redrilling through the epoxy, I cut some plastic drinking straws down to size, fitted them over the mounting screws and screwed them down until the straws were snug against the threads. Once the epoxy set, it was easy to simply pull the straws out, leaving a hole for the mounting screws.

Then, I cemented the coupler to the aft BT with the bulkhead facing forward. Since I was using the nosecone for the forward end of the shock cord, I covered the other eyebolt with epoxy and inserted it into the hole in the bottom of the NC. I then cut a hole in the shoulder of the NC and used a syringe to insert an epoxy well, which I hoped would ensure that the eyebolt stayed in place.

Now, this kit has a very interesting method for attaching your shock cord to the eyebolt. The instructions recommend looping the cord through the eyebolt and back onto itself (I did this on the nosecone end). Then, approximately 4" of overlap is completely saturated with 30 min epoxy and wrapped with tape. I chose electrical tape for this process and it comes out very strong. Another loop at the other end is completed and will be hooked onto a quicklink at the other end. Since I wasn't going to be modifying this kit any further, I sanded the nosecone shoulder and epoxied it to the top of the rocket. A quicklink on the bulkhead eyebolt and on the parachute complete the recovery harness. Rail buttons were substituted for the enclosed launch lugs, as I was told it's easier to get a rail than the right size rod at a launch.

Construction score: 4 out of 5
Pros: Everything fits well together.
Cons: Slotting flexible phenolic with a hobby knife isn't my idea of fun.

Finishing:
I had filled the spirals with cheap spackle prior to construction, so all that was needed at this point was several layers of gray Krylon primer to fill in what the spackle missed and a coat of white Krylon primer on top to guard against colors darkening. Due to the thickness of the flexible phenolic BT, there was a little additional filling to be done from the top of the BT to the nose cone prior to priming. All of this was easily accomplished, and the primer took readily to all sanded surfaces. Krylon paint was then used throughout for a scale paint job that drew several compliments at the launch site. Gotta love Krylon! You really have to work at it to make that stuff run.

Finishing score: 5 out of 5
Pros: The scale paint scheme is really neat and is a crowd-pleaser.
Cons: Slight filling needed between the nosecone and the body tube.

Construction Rating: 4 out of 5

Pic Courtesy of YankRocket Pic

Flight:
The model weighed in at the launch almost exactly at 60 oz. dry, even with the 45" chute that I substituted for the 30" enclosed chute and a Transolve TransBeep as well. Well, this was my Level 1 certification flight on an H242T, as well as my first "real" project beyond Aerotech, so needless to say I had plenty of nerves here. There was a slight wind (maybe 5 mph) which seemed to be slightly affecting most of the flights that morning. Since the anti-zipper design caused about 4 margins of stability with the motor loaded, I decided to launch vertically to minimize weathercocking instead of saving myself a walk. When the button was pressed, the rocket went perfectly vertical, with zero weathercocking. Deployment was perfectly at apogee on a 10 second delay. RockSim said this would be at about 1700 feet at this weight and with the modifications, but it honestly looked higher than that. Since I was a little paranoid about the drag separation and deployment, I placed the chute about 6 feet from the aft part of the rocket, which I think may have been a mistake. I suffered some minor fin damage, which, I now believe may have been due to the front end of the rocket hitting the fin during deployment. All told, it was a fantastic flight, and was good for my level 1.

Pros: Straight as an arrow in the slight wind
Cons: Can't really think of any.

Flight Rating: 5 out of 5

Summary:
This thing builds like a tank, despite being as long as it is. Flies beautifully on the 242 and I can't wait to up it a touch to the I357. This is a great certification kit, despite its length, as it's tough as nails with a little fin reinforcement. Had I not cemented the nose cone in, I would wager that it could be modified for dual deployment and easily stand up to a level 2 flight as well.

Overall Rating: 5 out of 5

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