Another King Kraken (L1 Certification) Build Thread

[himitsu]

Hello! I'm a new member to this forum, though I've read through its threads from time to time, for some years. I'm a BAR, and have built quite a few LP rockets, but now I'm trying to achieve an L1 certification, and I've chosen to build the King Kraken, a kit I purchased a couple of years ago. So, in the tradition established by rbelknap (and others), I've decided to create a thread to chronicle the build.

Here's what I've accomplished so far...

First, I cut out the stylish tube fins. I didn't cut these fins from the two 17” long tubes provided in the kit, but substituted one of my damaged 34” long tubes.

The damaged 34” tube came via a well-known carrier that I will simply call OOPS (in an attempt to avoid any contention). I suspect that OOPS may have some of the happiest employees working the delivery route between the hobby stores of the Midwest and my home, because they consistently use packages, destined for my address, in their team building exercises (or so it seems). I think they use them in competitions like, “who can make the loudest impact against the wall of the truck”, or “who can bounce a package the most number of times”. The once-straight-but-now-elbow-shaped package containing my damaged tube likely participated in a match or two of “King of the Hill”, a work-shoe print prominently embossed into the concave side.

Nonetheless, I hate to let a perfectly good damaged tube go to waste, so I cut it up into the Kraken's tube fins (the original kit tubes will one day compose the airframe of a scratch-built rocket). I centered the damaged portion onto the future glue line of one of the fins. Thus, the weakened part will eventually become strong, after the fin gets bonded to the airframe. So, after cutting things up, three of the fins came out unblemished, and only one will require some rehabilitation.

Here is a scene now familiar to all builders of the Kraken: the tube fins just after cutting (the second tube fin from the left has the damage, but it's on the back wall, and fully obscured at this angle)...



The construction of the motor mount and airframe came next. The instructions weren't very specific, and assumed prior rocket-construction experience. The 30” airframe consists of two tubes joined together: a 17” and a 13” tube. I decided to place the 13” section at the bottom, so the tube coupler could double as a thrust bearing structure (the forward centering ring of the motor mount will sit flush against the bottom of the tube coupler).

This picture illustrates the arrangement of the motor tube relative to the tube coupler. The tube on the right is the actual airframe of the in-progress King Kraken (with the motor tube, and shock cord, already installed).



To join the airframe, I severely lacerated the outer surface of the tube coupler with my hobby knife. I did the same to the inner surfaces of the body tubes (the portions destined to exist under the coupler). I used “standard” 30-minute hobby epoxy. The epoxy seeps into the lacerations and soaks through the multiple layers of paper to form a strong composite. This tube coupler will not move, and neither will the adjoining motor mount.

I also lacerated the motor tube just underneath the centering rings. Additionally, I embedded two lengths of Kevlar shock cord within the fillets strengthening the joint between the forward centering ring and the motor tube. The aft centering ring received “normal” epoxy fillets. After all, it's the forward centering ring that will convey force to the abutting tube coupler; the aft centering ring simply centers the motor tube. Finally, I installed two 1/4” #6 T-nuts (and a pair of #6 screws) spaced to accept a Madcow motor-retention plate.



I've begun work on the spirals, but I'll say more about that at a later date.

 

[CarVac]

Welcome to the forum.

I presume from your username that you have something you're still withholding from us?

You can feel free to tell us anytime; we won't tell a soul.

 

[himitsu]

Welcome to the forum.

I presume from your username that you have something you're still withholding from us?

You can feel free to tell us anytime; we won't tell a soul.

Thanks CarVac!

I'm not really trying to withhold anything, not even my inability to come up with a clever username. Even so, I appreciate your comforting words, and if I decide to disclose any important secrets to the Internet, I will certainly consider this forum, before all others.

 

[himitsu]

I completed treatment of the spirals.

Before I began this work, I checked out the forums to learn the state of the art. I found a method that blew me away. I've come to call this method, Spiral Denial.

I use the method where I deny their existence.

Since they don't exist, I don't have anything to fill.

Not one person has been able to see a spiral on any of my rockets that I've left hanging in trees for their inspection:roll:.

At first, it seemed that Spiral Denial could only work from a distance, but after further research, I discovered that some of the more experienced rocketeers found a way to eliminate even that limitation.

I wear gloves and take off my glasses. Can't see 'um, can't feel 'um-push the button! (need glasses for recovery....)

This was just too clever to pass up, so I decided to implement the method. Unfortunately, I've been handicapped with excellent eye sight since birth. While I could easily put on a pair of thick gloves, I had no glasses or contact lenses that I could remove to impair my vision, so I came up with a variation of the method. I call it Assisted Spiral Denial.

In Assisted Spiral Denial, I actually remove the spirals. This makes denying their existence considerably easier.

Here's how I accomplished it.

First, I cut off the top-level glassine layer spanning the primary spiral gap. I simply traced a sharp hobby knife against both sides of the spiral groove. The glassine came out of the spiral like a thread, and exposed the darker colored paper below.

Then I did the same thing to the secondary spiral, only this time I cut through the two top-most layers. Unfortunately, the second cut (on the secondary spiral) simply retraced the first cut, so it didn't produce a nice thread of paper. The paper over the secondary spiral was simply bisected. I was unconcerned, because I knew that the next few steps would remedy the situation.

I then traced the spirals with the backside (blunt side) of my knife a few times. A metaphor might prove helpful, here. Think of the knife traveling through the spiral, as a snowplough traveling through a road, or the needle of a record player tracking the grove of a record. The purpose of this step was to push any paper, still spanning the spiral gap, upward. I did this a few times, mostly on the secondary spiral, until the little bit of paper still spanning the spiral gap remained upright.

Then I flooded the spirals with water-thin CA to harden the upright paper. Next, a light sanding took the upright paper away. Now, the spirals were clean, and without any paper “drapery”.

I finally filled the spirals with Elmer's Wood Filler Max (with 3X the strength!), sanded, flooded with CA, and sanded again. (this is the first time I've used this particular wood-filler product--we'll see how it holds up).

The spirals are filled. I'm confident that when I finally finish this rocket, I will be able to deny the existence of my spirals with the best of them!



BTW, the spirals inside the tube fins required no cutting (no paper “drapery&#8221. I simply filled them.

 

[himitsu]

After masking off the future glue joints, I applied a coat of Rustoleum automotive primer. This filler coat will become sanded off (mostly). The previous spiral-filling efforts paid off, and it looks like I'll only need one coat of automotive primer, excepting for the interior of two of the four tube fins.

 

[himitsu]

The King Kraken's nose cone requires the installation of some nose weight and two small fins. The fins get installed 4 inches from the tip. Given the distance, I had no confidence that these fins could double as an anchor point for the nose weight by simply sloshing some epoxy around (not in a nose cone made of polyethylene plastic—very few things adhere to it). So, I decided to cut off the bottom of the nose cone and do a bit of “engineering” on the inside. Here are the components of the modified nose assembly.



The little rods in the picture are made of carbon fiber, and were liberated from an old kite. I'm going to use them to join the nose weight with the internal fin tabs. Eventually, I'll also use them to “pin” a plywood bulkhead to the bottom of the nose cone.

I cut the slots for the fins (using a hobby knife), and removed the bottom of the nose cone with a Dremel cutting wheel spun on a drill press. Here, the fins and a new bulkhead sit friction fit in the newly cut nose cone.



I cut the bulkhead from some plywood sub flooring, and made a loop from a cut-down u bolt. I countersunk the nuts of the u bolt using a Forstner Bit, and glued the assembly together with JB Weld.

 

[himitsu]

After I finished cutting the nose cone, I washed it with acetone (the inside and the outside), and then sanded the outside surface with 150 grit sandpaper, several times. With the bottom of the nose cone cut off, I could easily examine the inside.



The tabs on the nose fins protruded beyond the inside surface by approximately 2mm. I cut four lengths of carbon fiber rod (removed from some discarded kites) and epoxied them to the sides of the fin tabs. I positioned these four rods so they extend from the fin tabs to the tip of the nose cone. This way, they not only help to "lock in" the nose fins, but they also provide support to the nose weight.

Unfortunately, one of the carbon fiber rods moved off the fin tab during the curing process. I tried to remove it, but couldn't, so I epoxied in the nose ballast, and then added a few layers of glass cloth to strengthen the gap between the fin tab and the now somewhat out-of-place rod. I then epoxied one more piece of glass cloth over each fin tab assembly for additional strength.



For now, I won't close up the nose cone, until the Kraken comes closer to completion. I may need to add more nose weight, later.

 

[himitsu]

I finally tried fixit epoxy clay. I had it for a few years, and didn't use it, because I thought it too heavy for fin fillets. However, for fins on the nose cone, the extra weight is probably OK. The results were passable, but I think I will sand it to a more perfect shape.

 

[himitsu]

Here's my poison of choice, with all the additives, excepting for 1/4" chopped fiberglass (it's on order). I transferred the resin and hardener into a couple of 100ml squeeze bottles purchased from Hobby Lobby (it's easier to mix small amounts that way).

 

[himitsu]

From now on, I'll be mixing my poison in this costume, to terrorize the neighbors, although they've already seen me in it when I paint (they're nosy neighbors). Notice the nitrile gloves (substantially more chemical resistant than latex) purchased from Harbor Freight.

 

[Fe Dude]

Looking great so far!

What are you thinking of in the way of colors?

 

[himitsu]

At the fin glue joint, I drilled 3/32" holes 1/4" apart into the region of the body tube between the motor mount centering rings. Above and below the centering rings, I cut divots using a 1/8" spherical cutter on my Dremel. I also cut divots into the tube fins (at the future glue joint). These holes and divots will receive thickened epoxy, and form "glue" rivets, an old-school technique from the 60's. I read about this trick in an Apogee newsletter, Mario Perdue's book, Seize the Sky, and I also read about it here, on TRF.



To keep the divots from becoming cut too deeply, I attached the general-purpose cutter housing to my Dremel.

 

[himitsu]

I thickened epoxy with the West Systems 404 filler to the consistency of peanut butter (without the chunks) and pushed it into all the holes and divots with a plastic spatula.

While it cured, I cut out some fin fixtures. I used 4mm thick project board, it's composed of a plastic foam sandwiched between two layers of poster board. This stuff is cheap (you can get it at Hobby Lobby), and it produces fixtures that do not require additional reinforcement (it's strong enough to support small to moderately sized rockets).



I mixed another batch of epoxy, and thickened it with West Systems 404 filler to the consistency of ketchup. I used this mixture to tack on the tube fins, one at a time (I attached one fin, and then allowed it to cure for a full day, before I moved on to the next).

 

[rbelknap]

I finally tried fixit epoxy clay. I had it for a few years, and didn't use it, because I thought it too heavy for fin fillets. However, for fins on the nose cone, the extra weight is probably OK. The results were passable, but I think I will sand it to a more perfect shape.

View attachment 153883 View attachment 153884

I used epoxy clay on my canard fillets too. Looks like your's came out much better than mine

 

[rbelknap]

I thickened epoxy with the West Systems 404 filler to the consistency of peanut butter (without the chunks) and pushed it into all the holes and divots with a plastic spatula.

While it cured, I cut out some fin fixtures. I used 4mm thick project board, it's composed of a plastic foam sandwiched between two layers of poster board. This stuff is cheap (you can get it at Hobby Lobby), and it produces fixtures that do not require additional reinforcement (it's strong enough to support small to moderately sized rockets).

View attachment 153889

I mixed another batch of epoxy, and thickened it with West Systems 404 filler to the consistency of ketchup. I used this mixture to tack on the tube fins, one at a time (I attached one fin, and then allowed it to cure for a full day, before I moved on to the next).

View attachment 153890

And I should have made some of these. I don't think I did too bad aligning my fins by eye, but a guide would have reduced my anxiety over getting everything on straight.

 

[rbelknap]

Also - welcome to the Forum! I'm glad my build thread seems to have inspired yours. I'm sure I'll learn something new.

(Oh, and welcome to the Brotherhood of the Kraken.)

 

[himitsu]

Looking great so far!

What are you thinking of in the way of colors?

That's the million dollar question, and right now, I don't know the answer. The Kraken is just so unique looking, everyone went out and got one! The only way to distinguish one Kraken from the others is with a unique paint job. Unfortunately, I've come late to the party, so this might prove a challenge. We'll see.

 

[himitsu]

Also - welcome to the Forum! I'm glad my build thread seems to have inspired yours. I'm sure I'll learn something new.

(Oh, and welcome to the Brotherhood of the Kraken.)

Thanks rbelknap. I read your build thread back when I was just a lurker on TRF, back when you were still writing it. You put a beautiful finish on that project, with the color-shift paint, custom decal, and metallic-green tube-fin walls. That's a tough act to follow.

 

[CarVac]

That's the million dollar question, and right now, I don't know the answer. The Kraken is just so unique looking, everyone went out and got one! The only way to distinguish one Kraken from the others is with a unique paint job. Unfortunately, I've come late to the party, so this might prove a challenge. We'll see.

Paint it the original material colors. I think that'd be pretty clever...

(or just fly naked)

 

[himitsu]

Paint it the original material colors. I think that'd be pretty clever...

(or just fly naked)

That would be clever... and yet... at the same time, it would also be dreadfully unsatisfying. :wink:

 

[CarVac]

That would be clever... and yet... at the same time, it would also be dreadfully unsatisfying. :wink:

I thought of a situation where it would be satisfying: if you make an upscale of a low-power rocket, you paint your huge fins with very coarse balsa grain, and draw in the proper spiral angle of the original tubing...

 

[himitsu]

I thought of a situation where it would be satisfying: if you make an upscale of a low-power rocket, you paint your huge fins with very coarse balsa grain, and draw in the proper spiral angle of the original tubing...

OK, I can see that.

 

[himitsu]

Modified the fin fixture to stay clear of the fin fillet area. Mixed epoxy with equal parts colloidal silica and phenolic micro-balloons, thickened to the consistency of cake icing. Fashioned fillets using a 3/4" diameter dowel. Created the fillets two at a time, giving each pair one day to cure, before proceeding to the next (the fillet mixture was thick enough to do all four pairs in a single shot, but I chose the slower route to ensure that the epoxy stayed in place).



These results are pretty crude. Additional sanding and filling will be forthcoming.

 

[Pem Tech]

Maybe I should check in on the forum more often, completely missed this thread.
And a wonderful job you are doing as well! No joke, you take your rocketry seriously.
Keep it going.

My apologies on the coupler debacle, you must have gotten an old version of the Destructions. Thought I had hunted them all down and buried them in a shallow grave.

Also - welcome to the Forum! I'm glad my build thread seems to have inspired yours. I'm sure I'll learn something new.

(Oh, and welcome to the Brotherhood of the Kraken.)

OK, consider this stolen. That is a great idea! It will never outweigh the Llamas but I like it.

At the fin glue joint, I drilled 3/32" holes 1/4" apart into the region of the body tube between the motor mount centering rings. Above and below the centering rings, I cut divots using a 1/8" spherical cutter on my Dremel. I also cut divots into the tube fins (at the future glue joint). These holes and divots will receive thickened epoxy, and form "glue" rivets, an old-school technique from the 60's. I read about this trick in an Apogee newsletter, Mario Perdue's book, Seize the Sky, and I also read about it here, on TRF.

View attachment 153887

To keep the divots from becoming cut too deeply, I attached the general-purpose cutter housing to my Dremel.

View attachment 153888

Hey, that is a cool that idea! Was there much mess inside the tube fin?

I thickened epoxy with the West Systems 404 filler to the consistency of peanut butter (without the chunks) and pushed it into all the holes and divots with a plastic spatula.

While it cured, I cut out some fin fixtures. I used 4mm thick project board, it's composed of a plastic foam sandwiched between two layers of poster board. This stuff is cheap (you can get it at Hobby Lobby), and it produces fixtures that do not require additional reinforcement (it's strong enough to support small to moderately sized rockets).

View attachment 153889

I mixed another batch of epoxy, and thickened it with West Systems 404 filler to the consistency of ketchup. I used this mixture to tack on the tube fins, one at a time (I attached one fin, and then allowed it to cure for a full day, before I moved on to the next).

View attachment 153890

Could you detail how you got the fin slots squared on the fin guide? Been look for a way to do it in Rocksim, without any luck.

 

[himitsu]

My apologies on the coupler debacle, you must have gotten an old version of the Destructions. Thought I had hunted them all down and buried them in a shallow grave.

No problem. I think I purchased my King Kraken a few years ago, so I'm sure I got an earlier version of the kit.

Hey, that is a cool that idea! Was there much mess inside the tube fin?

It mostly came out well, but the wound-paper tube did foul the spherical cutter too often, and I had to stop frequently to clean it (this cutter works better with regular wood). I did get impatient a number of times and finished a cut by applying excessive pressure. Where I did this, a shallow pimple formed on the inner wall of the tube fin. I did push most of this back in place, but the remainder will become sanded off, now that the underlying divots have become filled with epoxy. These uniquely shaped tube fins really show off the inner walls, so I will make sure they come out unblemished in the end.

Could you detail how you got the fin slots squared on the fin guide? Been look for a way to do it in Rocksim, without any luck.

I'm a Rocksim user too, but I don't use it too often to create templates. I normally use CorelDraw, but this time around I actually used InkScape (a free, open source, vector graphics application). Normally, I would create the whole fin-alignment template in the drawing program, print it out, glue it to project board, and cut; however, this time the process got a little bit more involved.

First, I cut an 11” by 11” square from 4mm project board, as accurately as I could. I marked the midpoint (at 5.5&#8221 of each side, and drew two guidelines, proceeding from the midpoint of one side to the midpoint of the opposite side. The two lines formed a cross at the center.

I then opened InkScape and produced the following template.



I printed out four copies of that template, and cut them out (the larger rectangle), as well as the "window" (the square) in the middle of the left circle. This "window" helped me to align the template to the center of the project board (the square project board with the two guidelines that intersect perpendicularly at the center). I think you can see how the guidelines on the template correspond to guidelines on the project board. So, I simply taped down a template, cut out a fin circle (the circle on the right), removed the template, and repeated, with another template rotated 90 degrees. After I cut the fourth and final fin circle, I also cut out the center circle (I had to cut the center circle last; otherwise, I'd lose the ability to align the templates prematurely).

Maybe I should check in on the forum more often, completely missed this thread.
And a wonderful job you are doing as well! No joke, you take your rocketry seriously.
Keep it going.

Much appreciated. I intend to put in a good effort to the end.

Like many others, I like this particular design of yours. The deep helical sweep of the tube fins really make this rocket stand out. But it's not only interesting, it's really good looking. I think that you somehow managed to commune with the muse of sport rocket design. Now, tell her to come visit me!

 

[dward]

I completed treatment of the spirals.

Before I began this work, I checked out the forums to learn the state of the art. I found a method that blew me away. I've come to call this method, Spiral Denial.



At first, it seemed that Spiral Denial could only work from a distance, but after further research, I discovered that some of the more experienced rocketeers found a way to eliminate even that limitation.



This was just too clever to pass up, so I decided to implement the method. Unfortunately, I've been handicapped with excellent eye sight since birth. While I could easily put on a pair of thick gloves, I had no glasses or contact lenses that I could remove to impair my vision, so I came up with a variation of the method. I call it Assisted Spiral Denial.

In Assisted Spiral Denial, I actually remove the spirals. This makes denying their existence considerably easier.

Here's how I accomplished it.

First, I cut off the top-level glassine layer spanning the primary spiral gap. I simply traced a sharp hobby knife against both sides of the spiral groove. The glassine came out of the spiral like a thread, and exposed the darker colored paper below.

Then I did the same thing to the secondary spiral, only this time I cut through the two top-most layers. Unfortunately, the second cut (on the secondary spiral) simply retraced the first cut, so it didn't produce a nice thread of paper. The paper over the secondary spiral was simply bisected. I was unconcerned, because I knew that the next few steps would remedy the situation.

I then traced the spirals with the backside (blunt side) of my knife a few times. A metaphor might prove helpful, here. Think of the knife traveling through the spiral, as a snowplough traveling through a road, or the needle of a record player tracking the grove of a record. The purpose of this step was to push any paper, still spanning the spiral gap, upward. I did this a few times, mostly on the secondary spiral, until the little bit of paper still spanning the spiral gap remained upright.

Then I flooded the spirals with water-thin CA to harden the upright paper. Next, a light sanding took the upright paper away. Now, the spirals were clean, and without any paper “drapery”.

I finally filled the spirals with Elmer's Wood Filler Max (with 3X the strength!), sanded, flooded with CA, and sanded again. (this is the first time I've used this particular wood-filler product--we'll see how it holds up).

The spirals are filled. I'm confident that when I finally finish this rocket, I will be able to deny the existence of my spirals with the best of them!

View attachment 150834

BTW, the spirals inside the tube fins required no cutting (no paper “drapery&#8221. I simply filled them.

It's looking like a great build thread, sorry I'm late to the party. On a lot of tubes you will see a deep spiral, which can just be filled, and a secondary spiral that is visible but you can't really feel it with your finger. I take it, it is the later that you are cutting the glassine from. I am definitely going to use this technique in the future even though it sounds like a pain.

 

[himitsu]

It's looking like a great build thread, sorry I'm late to the party. On a lot of tubes you will see a deep spiral, which can just be filled, and a secondary spiral that is visible but you can't really feel it with your finger. I take it, it is the later that you are cutting the glassine from. I am definitely going to use this technique in the future even though it sounds like a pain.

You are right (or, you should be). The secondary spiral has the glassine covering; the primary should not.

Yet, I distinctly remember removing the glassine from both spirals. And now, when I reread my description of the process, I'm confused. Interesting. I wonder if the primary spiral was so tight, that I actually went after the secondary and tertiary spirals. I don't remember, and the tube is now so well sanded and filled that I can't tell anymore.

 

[rbelknap]

*bump* I'm dying to see how your Kraken is coming along (and/or hear about a successful cert flight)

 

[himitsu]

Thanks for bump! I put this project on the back burner for some time, first, because of the winter weather, and then because of other competing priorities. But now, I'm almost ready to start this up again. I'll probably be able to post an update in a couple of weeks.

 

[himitsu]

My L1 certification effort has been put on indefinite hold, as I devote my efforts into starting a new business. So, goodbye for now rocketry forum! Hopefully, I'll return some months down the road, and finish this project.