This is a rocket that flies on mid and high power motors, has tube fins, and uses parachute recovery.
The first step in the construction of this beast is to begin the finishing process. Spirals are to be filled in and the tubes sanded down. This latter step is so that the adhesives may grip better. I did sand down the tubes but did nothing about the spirals. They were not bad and they usually don't bother me.
After sanding down the tubes, I had to check them to make sure I knew which was which. One is the airframe and the other is the source from which the tube fins are to be cut. I identified them by length and marked them with a pencil so they would not get mixed up.
One page of the instructions contains two wraparound guides to be cut out. This page is distinctive in that it is the only page printed on legal paper (as opposed to letter paper). I cut out the guide for the fin tubes, which was the simpler of the two. It contained markings for 2 lines, 180 degrees apart. I wrapped the guide around the tube and found that it would not quite close. I checked alignment on everything to satisfy myself that everything was right and everything was, except that the guide had about a 1/16 inch space between match lines.
I was unsure whether this gap was allowed for in the markings or not and sent a message to Layne at Pemberton Technologies. I went ahead an drew the lines on the tube, however, figuring that if the gap is incorrect, I would make my final marks by construction offsets. For now, I just wanted to keep on working.
The instructions give a list of distances at which the upper and the lower lines are to be marked. These distances will be very important for making the cutting marks and were checked carefully.
Making the tick marks on the fin tube was not too difficult. Drawing the lines between them was. The instructions give a well thought out method. You need some sort of flexible straightedge. You line it up with the appropriate tick on the top and bottom lines. You make sure it's tight and flat and correctly positioned, then you draw a line. It's logical, it sounds easy, but it's extremely frustrating.
I used a piece of poster board. I cut out a strip and marked the "good" side, the side with the factory cut that I was confident was straight. I would get it aligned with a tick mark and pointing the in approximate right direction. I would tape down that end and then wrap it around, trying to keep it tight and straight. Cellophane tape does not work. Neither does narrow masking tape. It keeps wanting to let go under stress. Finally, I settled on some Frog Tape. It was tacky enough for a single pair of lines but that was only part of the problem. Invariably, the strip was just a little bit off and I would have to take up the tape and try again. When it was in the right place, marking with a pencil was easy. Then the entire process had to be repeated to draw the mirror image of the line just drawn. Then everything is shifted and you do it again...and again...and again. I had to take a break halfway through because of the frustration factor.
Let me be clear: This is not a problem with the design or the kit. Part of what makes this kit appealing is the unusual curve of the fin tubes. I can't think of a better way to do it that the way provided for. Its just that it was my first time and it was frustrating.
With the contours of the fins marked on the fin tube, it was time to cut them out. The instructions recommend using a fresh X-Acto blade. I found them to be imprecise at this point. Things work much easier using a fresh blade for each separate fin.
The process is simple. You just trace the lines you drew with the blade being careful to be exactly on the line. You don't push very hard at all--it's more of a scoring than a cut. You then draw the blade over the same path again...and again...and keep doing it until you cut all the way through. For me, this varied between 5 and 15 passes on any given segment. This is tedious but the result is worthwhile.
Taking a breather, I cut out the body tube marking guide and applied it to the BT. I had the same small gap in it that I had in the fin tube guide. By this point, I have decided that the small amount is not enough to worry about. Lines for the 4 fins and the launch lug were transferred to the BT and elongated to the entire length of the tube using a pocket door frame.
With the tube fins cut, the next step is to mask off the lines along which they will be mounted. I did this on both the tube fins and the body tube using 1/4" Tamiya tape. I ran out on the penultimate line on the BT and cut a strip of Frog Tape to finish. I then applied Elmer's Wood Filler to the spirals inside the tube fins. I had decided at the outset that I would not worry about the spiral on the BT or the outside of the fins because they are not prominent, but the spirals on the inside of the tube are.
The filler had a day to dry out and then I started sanding it. It filled the spirals well but sanding inside of them was a nightmare because my hands are too big to fit them well. The tops and bottoms were not too hard but the parts completely surrounded by tube were.
With the spirals filled, I proceeded to prime the Kraken with Kilz. It covered the pencil marks very well and did better than anything else I could think of for priming the inner surface of the tube fins. However, spraying the insides of tubes is not easy. It needed another coat. Also, the sanding I had done on the inside of the tubes resulted in the primed tubes having a bad case of the fuzzies. This will probably mean one extra iteration of spraying and sanding before it is ready for the finish paint.
The fuzzies got sanded down and I learned something important: If my hands are going to sand the insides of tubes, they need to be a bigger diameter. It was painstaking work, not because of the difficulty of doing it but because of the difficulty of getting access. Even so, I judged that another coating of primer would not be needed. I moved the tube fins to the booth and proceeded to spray their interiors with a bright purple.
When the purple had dried, I decided to go ahead and paint the black. The instructions give a creative way to mask of the interior of the tube fins and protect them. You just roll up a piece of cardboard, insert it in the tube and let it expand. Much to my surprise, it worked very well. I had thought that it would only do a "so so" job but is seemed to do a better job than my normal masking tape application.
The tube fins were placed in my booth as well as the BT. I then began applying coats of black. I applied the paint lightly for three coats and was satisfied with the result.
While waiting for the black to dry, I tackled the nosecone. It has 2 canards which needed to be mounted. These are not mounted on the surface but in slots which must be cut. The instructions say to use the 2 mold lines for guides and make marks 4 inches back from the tip. These points mark the forward edges of the fitting. The canards were then used to mark the width and length of the cut.
The instructions recommend to use a Dremel tool to cut the slots. I have still not located mine since moving my shop, and I decided to do it the "hard way" with multiple passes of an X-Acto. To my surprise, this turned out to be easy. It was much easier than cutting the tube fins!
I decided that I wanted to dress the edges of the canards so I broke out the sandpaper and beveled the leading, outer and trailing edges. I then mixed a small amount of 5 minute epoxy and used that to mount them.
The kit comes with a small bag of lead droppings to be used as nose weight. In order to better facilitate getting it into place, I drilled a 3/8" hole in the base of the NC. The shot was then poured into place and allowed to settle at the very tip. Two ounces of 12 minute epoxy were then mixed and poured into the cone to hold the lead in place. While the epoxy was still fluid, I canted it over to let it flow over the tabs on both of the canards. The hole I had drilled was large enough to be able to look in and make sure that I had tilted the cone far enough to accomplish this. I moved the cone back and forth to let the epoxy wash over the tabs several times before it finally set up. This way, a thicker layer was able to be applied to the tabs than would otherwise be the case. When the epoxy started to stiffen, I set the cone up on its nose to allow it to finish curing.
Attention then turned to the motor mount. One of the centering rings needed to be designated as the "forward" ring. That ring had a slot filed into its inner boundary to accommodate the passing of the flat nylon shock cord. A Dremel tool is recommended for this, but as I mentioned previously, mine is MIA. The file I used was supplemented with some judicious cutting with the X-Acto.
Masking tape was used to hold down the end of the nylon tubing against the motor tube. The forward ring was then slipped into place and epoxied 2 inches from the end. When that had set, the aft ring was epoxied into place 2 inches from the back end. Both rings were filleted with epoxy.
Working on the NC and motor mount had allowed sufficient time for the black paint to dry so I turned next to installing the motor mount. The rings had to be sanded a little bit, but that was quickly taken care of and the mount was put in place with epoxy and a generous amount of filleting. It was installed so that the end of the motor mount was flush with the aft end of the BT.
With the motor mount in place, I stripped off the masking of the fins. The instructions say to use carpenter's glue so that's what I did. I wanted to hedge my bets however and first drilled a series of 1/8" holes along the fin mounting lines to form glue rivets. Yellow glue was then used to put the first fin in place and it was allowed to dry.
I took gluing of the tube fins slowly, applying one and then taping it into place and letting it dry. That left me with time on my hands to ruin other components so I turned my attention back to the nosecone. It had been primed with Kilz and sanded. The Kilz was the only filler on the wooden canards and seemed to do the job well. After sanding, I sprayed it black.
After the black NC had a day to dry, I masked off the outer edges of the beveled canards and brushed on a squidly pink. My intention was to let it dry and then remask and get the leading and training edges but I kind of like just the tips.
I also started highlighting the cut edges of the tube fins with the same hot pink. While I was at it, I began to experiment with some pink blobbing and the forward tips of the tubes. Originally, I was just giving a first coat over the black and planned to mask off a simple area and go over it again with another coat. Close up, it doesn't look all that good and still needs some touching up but from a few feet away, it has a look of "biological coloring" to me.
After staring at the results of the pink for a while, I decided to go back to my original idea and masked off a roughly diamond shaped area at the front of each tube. I also masked off a small triangle at the rear. I then started brushing on the Panther Pink.
On the day after, I pulled off the masking and was horrified to see some of the bleeds. They will be "fixed" by remasking and hitting it with the black again. For the time being though, I started filleting the fins.
The instructions warned that this can be difficult, but it was not as bad as I expected. I used masking tape to form dams and then mixed up 12 minute epoxy 2 tablespoons at a time. I used a plastic cup to pour the epoxy into the troughs and when it started to thicken, I pulled off the tape. This usually left some bad stringies but a rubdown with ethanol smoothed things up. This was done 4 time to hit all the joints.
I had the funny feeling I was forgetting something at this point and started looking through the bag of parts. I found the launch lugs. That could have made Saturday embarrassing.
I located the tape that was masking the lug location and peeled it off. The kits comes with two lugs so I started looking for a piece of 1/4" rod with which to get them straight. I could not find it and sat for a few moments. Then I looked in one of the drawers again. I did not find the rod but I did find a 4" x 1/4" lug. I decided to use that. I attached it with 5 minute epoxy at the forward lug mark.
I let the lug epoxy set overnight and then got to work with a brush and some black acrylic to clean up pink blobs, paint the lug and touch up the rocket. It was going to need more but it was starting to bother me.
PROs: This is a fairly simple rocket but has a cool design. The instructions for cutting the fin tubes are first rate.
CONs: While the instructions for cutting the tubes are first rate, actually marking and cutting them is tedious.
I finished my King Kraken while it was being constructed. This is described above and made simple what would be a nightmare of masking if the rocket had been assembled.
After assembly, a brush was used to touch things up.
PROs: The black gives a powerful look.
Construction Rating: 4 out of 5
The King Kraken is sold as a HPR but for the maiden flights, I had no Hs and the field would have been too small for them anyway. Pemberton Tech also says that the rocket can be flown on Gs and even Fs. I decided to try the first flight with a Roadrunner G80-7 using a 38-29 motor adapter.
The boost was perfect but the delay was a little long. Even so, the chute deployed and the King Kraken landed without a scratch. That is some feat in the midst of all the whitebrush.
The first flight exceeded expectations and I decided to wimp out with an F60-4. THe rocket was prepped and set up. Again, it was a flawless flight and the 4 second delay seems to be perfect for this motor.
An inspection of the rocket after recovery showed that the nylon recovery cord had just started to zipper the BT. This will be an easy fix.
This rocket is fairly heavy to my thinking but it performed admirably of F and G motors. I can only imagine what the bigger stuff will do.
PROs: Impressive in flight, durable.
The shock cord consisted of nylon tubing attached to the motor mount. This was in turn connected to the NC with a snap ring. The generous, quality nylon chute was similarly attached to the NC.
Except for a minor zippering problem noted above, the system worked well.
Flight Rating: 4 out of 5
This is a simple high power rocket that is something other than a 3FNC. It provides a good introduction to the building of these bigger rockets.
Overall Rating: 4 out of 5