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Build Thread: Pemberton Technologies King Kraken for Level 1 Cert

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mbeels

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After considering many options for my Level 1 rocket (Zephyr? Super DX3?) I chose the King Kraken. Besides being a really great looking rocket, I liked the tube fins and it could fly on Gs at non-HP fields. But mostly it is a great looking rocket.

My plan is to do my Level 1 flight at Red Glare in April, so I'll provide build and flying updates through then.

Layne was helpful and sent quick responses to my questions over email. After a couple of days, the kit arrived in good shape, but some of the pieces were hungry, I don't think that the USPS fed it very well.

First step was filling tube gaps:

Fortunately my son likes sanding:

Had a little help with clean up as well:

For the squiddly bits on the nose cone, I couldn't find a melon baller, so I tried a cheese grater.



And after marking the fin tube, I went to work with a new #11 blade, time lapse:
https://vimeo.com/user4092129/review/316267586/8ce25fb781

At this point, I'm trying to decide if it is a good idea to fiberglass the inside of the tube fins. I have some 0.75 oz cloth, it would smooth out the interior, and add a little extra strength, but I'm not sure it needs it, they seem pretty strong!
 

Tobor

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Hello and welcome to TRF.
The Kraken series are really sexy rockets. I did a BT-80 upscale of Pem-Tech's Kraken in the fall/winter of 17'. But, unfortunately I lost it on it's maiden flight :(
I have plans to do the King Kraken with a fiberglass wrap. Should be interesting.

Anyhoot, best of luck on your build and L1 cert.

Tobor.
 

mbeels

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Thanks, Tabor. I do like the looks, it has a very unique aesthetic. I have plans to do some mini Kraken, a squid-squad. They'll be 18mm tubes with 13mm motors and streamer recovery. It think it'd be fun to launch 4-6 18mm Krakens and the King Kraken.

Are you going to wrap the entire King Kraken with fiberglass, tubes and body? Are you planning high thrust I's, or J's even?
 

dhbarr

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Thanks, Tabor. I do like the looks, it has a very unique aesthetic. I have plans to do some mini Kraken, a squid-squad. They'll be 18mm tubes with 13mm motors and streamer recovery. It think it'd be fun to launch 4-6 18mm Krakens and the King Kraken.

Are you going to wrap the entire King Kraken with fiberglass, tubes and body? Are you planning high thrust I's, or J's even?
MIRV the Krakes? I love it!
 

mbeels

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Ah, wrong link to the time lapse of the fins.....

 

Tobor

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lol... Love the squid attack in the video :p

...Are you going to wrap the entire King Kraken with fiberglass, tubes and body? Are you planning high thrust I's, or J's even?
Edit: Yep, planning on glassing airframe and tube fins.
As I am not L2 certified (J, K, L Motors) the largest motor I can fly atm is an AT I435T in my RMS-38/600 Hardware. I do not have anything larger in 38mm cases atm.
 
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mbeels

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It's hazardous work down there in the dark depths of my basement, but somebody's gotta do it!
 

mbeels

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lol... Love the squid attack in the video :p



Edit: Yep, planning on glassing airframe and tube fins.
As I am not L2 certified (J, K, L Motors) the largest motor I can fly atm is an AT I435T in my RMS-38/600 Hardware. I do not have anything larger in 38mm cases atm.
I'm curious, do you think that the tubes and airframe aren't strong enough? Or other reasons? I'm also expecting to launch H and Is, and was debating fiber glassing the tube fins interior, but I'm undecided.
 

Tobor

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I'm curious, do you think that the tubes and airframe aren't strong enough? Or other reasons? I'm also expecting to launch H and Is, and was debating fiber glassing the tube fins interior, but I'm undecided.
My main reason is durability. I know I will fly the tar out of that bird, so I need to strengthen it as much as possible.
 

Arsenal78

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I’ve eyeballed the Kraken a few times. BTW, what did you use to lay the wood filler into the spirals? I seem to get more on my fingers than what goes into the spiral.
 

mbeels

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Tentacles. I mean fingers!

I thinned out Elmer's Carpenter's wood filler (interior) with water, and then (wearing gloves) smeared a light bead over the spirals. There is a quite a bit of filler piled around the spiral, but this stuff sands quickly and easily. I did one pass on 150 grit to knock down the thick stuff, and then followed up with 220. Next will be primer.
 

mbeels

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A little more progress over the weekend, the motor mount went together, it was pretty straightforward. I taped down the shock cord to hold it tightly against the tube and distribute the epoxy evenly.


I then decided that I wanted to build this for head-end dual deploy, even though my cert flight will be a simple motor eject the main at apogee. To add a secure mounting point at the tip of the nose cone, I first probed the interior of the nose cone just in front of the TTW canards and created a template that matched the interior diameter and taper of the nose cone.


Then I transferred those diameters to the top and bottom of a piece of 1/4" plywood with a compass,


and epoxied it in place. The canard tabs will hold this hard point captive. This will give a place to add or remove nose weight, and also a parachute attachment point for HED dual deploy.

 

Nytrunner

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Great build! Love the video documentation

I then decided that I wanted to build this for head-end dual deploy, even though my cert flight will be a simple motor eject the main at apogee.
I'm curious here. How are you laying out the dual deployment? I've only seen that technique applied in fiberglass rockets where the cone shoulder is actually a coupler piece that acts as ebay and ejects the nose with the main inside.
 

mbeels

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Great build! Love the video documentation

I'm curious here. How are you laying out the dual deployment? I've only seen that technique applied in fiberglass rockets where the cone shoulder is actually a coupler piece that acts as ebay and ejects the nose with the main inside.
Thanks. I'm following the DD ideas from this thread:

https://www.rocketryforum.com/threa...oyment-details-explanations-requested.129482/

See post #16, second image. I will attach an additional length of airframe onto the shoulder of the nose cone, and the AV-bay will be normal. I'm also considering putting the deploy charges in finger glove cots at the end of the ematch wires so I can place one near the tip of the nose cone, so it pushes the chute out. Although many say that this isn't necessary.
 

mbeels

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Aeropack motor retainer is jb welded in place, and fillets have been added to the canards. My preferred method is 30 minute epoxy with as much phenolic microballoons that I can mix in. At least to peanut butter consistency.

Fiberglass and finishing resin are here, next step is glassing the inside of the tube fins.

 

Tobor

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Nice work on those fillets. I'm jealous, I always manage to mess up the forward ends of my fillets... :(
 

mbeels

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Nice work on those fillets. I'm jealous, I always manage to mess up the forward ends of my fillets... :(
Thanks! Yeah, that's the most awkward part, I often end up with divots or blobs there that take extra filling and finagling. These canards have two fillet "ends" (and this one was the better looking one!).
 

AHansom

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Awesome work. Always great to see another Kraken!!! I don't believe its necessary to fiberglass the fins unless you just want to. I have a King Kraken built stock that's survived several H flight without any fin damage.
Krraken2.jpg
 
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mbeels

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Awesome work. Always great to see another Kraken!!! I don't believe its necessary to fiberglass the fins unless you just want to. I have a King Kraken built stock that's survived several H flight without any fin damage. View attachment 374646
Nice pic! Yeah, the consensus seems to be that the fins are plenty strong as they are, and don't need any extra reinforcement. I'll probably fiberglass them anyway, because:
  • It would be easier than filling the internal spiral seams
  • I just bought a bunch of 3/4 oz fiberglass
  • I want to try out the method of using a balloon to fiberglass the inside of a tube.
 

AHansom

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I can tell you from experience its much easier to balloon the fiberglass before the fins are cut or fiberglass the outside. With the scalloped shape the balloon didn't set good for me. I ended getting another tube and using a Solor composite sleeve on the outside of a full length tube and then cutting the fins with a dremmel.
 

mbeels

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I can tell you from experience its much easier to balloon the fiberglass before the fins are cut or fiberglass the outside. With the scalloped shape the balloon didn't set good for me. I ended getting another tube and using a Solor composite sleeve on the outside of a full length tube and then cutting the fins with a dremmel.
Thanks for the input! I'm actually sitting in the basement right at this moment, staring at the tube fins, and the fiberglass, and thinking the exact same thing. I imagine that doing two at a time would be easiest, the two pairs that each together make a mostly complete cylinder. Hmmm......
 

mbeels

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Oi! You're totally right, but I just had to try it. I limited the balloon to the bottom, and then used a foam brush to pat down and soak up the upper part. I can see a definite bubble where the fiberglass lifted like a wave in front of the balloon. It isn't pretty, but I think it is salvageable. I'm going to skip the balloon on the rest, and just use the foam brush.


 

mbeels

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Egh, I didn't like what the balloon was doing, so I deflated it and removed it. After shifting around the fiberglass and some blotting, it looks ok. It will be alright after some sanding and filling.

 

mbeels

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Alright, the blotting worked, it looks good. After trimming, the fiberglassed fin weighs 2.1 oz, compared to 1.8 oz for an unglassed one. So it didn't add much weight (it was only 3/4 oz fiberglass). The unglassed fin is so stiff, it is hard to tell much difference in stiffness. Maybe the bottom edge will hold up better against dings, but I'll consider it a primarily cosmetic choice.

On to the rest......
 

mbeels

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Finished fiberglassing the other three fins tonight. It is a bit of a tedious process, because applying tension to the cloth to smooth it out and lay it flat doesn't work on the inside of a tube. Using foam brushes to blot out the resin, and tease the cloth around to lay flat did work quite well though, just a manual process.

Cutting the pieces and checking the sizes, they look like pigs in a blanket.


And after everything is all tucked in neatly and blotted out.


The hardest part was choosing the right music station. I ended up a Pandora mix of Birdy, Bon Iver, and Banks. Perfect.
 

AHansom

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Looks like a fun learning experience!! The scary part for me is once the resin is mixed and the clock starts ticking. One thing I think is an advantage to fiberglasing the outside of the tubes is the stronger bonding surface. I feel its a much stronger bond than paper to paper. After loosing some Kraken fins I made the replacements with the Fiberglas on the outside of the tube.

fintube.JPG
markingtubes.JPG
 
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mbeels

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Looks like a fun learning experience!! The scary part for me is once the resin is mixed and the clock starts ticking. One thing I think is an advantage to fiberglasing the outside of the tubes is the stronger bonding surface. I feel its a much stronger bond than paper to paper. After loosing some Kraken fins I made the replacements with the Fiberglas on the outside of the tube
Interesting, which weight Soler tube did you use? Could you still cut it with an X-acto? Did it take a lot of filling to finish it?

I don't recognize the U shaped cut in the second photo, is that the body tube?

Did you lose the tube fins on landing, or shed them in flight?

Yes, every step of the way is always a learning experience!
 

AHansom

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I'm enjoying your build and look forward to seeing the first flight pictures. I Don't remember the weight, it was the lightest weight sleeve they offered and It stiffened the tubes up pretty well. I never tried cutting with an exacto knife, went straight to the dremmel with a cutoff wheel. Probably cut as fast or faster than the knife. Filling was fairly easy after a couple shots of high fill primer, filled the weave in nicely. I don't want to derail your thread, but I had a couple of successful and unsuccessful Kraken's over the years. Maybe you could guess what the U shaped cutouts where for?

IMG_9524.2.jpg
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photo-6.jpg
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P1040382.JPG
 
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mbeels

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I'm enjoying your build and look forward to seeing the first flight pictures. I Don't remember the weight, it was the lightest weight sleeve they offered and It stiffened the tubes up pretty well. I never tried cutting with an exacto knife, went straight to the dremmel with a cutoff wheel. Probably cut as fast or faster than the knife. Filling was fairly easy after a couple shots of high fill primer, filled the weave in nicely. I don't want to derail your thread, but I had a couple of Kraken's over the years. Maybe you could guess what the U shaped cutouts where for?
Awesome!

Yes, that cut makes much more sense now. No worries about hijacking the thread, I post here to learn from others, and seeing more rockets is always cool. I love the upsized Kraken, what size body tube is that? Nice paint job on the clustered Kraken, I like that detail near the nose.

Another question for you, I've seen some folks mount the rail buttons inside the fins, where did you put yours?
 
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