Got Squid? Got flight report?? 66% K Cluster!

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Salvage-1

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4in Blue Tube, 51" long, sleek Kraken lines. This beauty will ride the winds on four (4) 10" 38mm MMTs. Designed to fly on as little as 2 H class motors, staged 2 to 2 airstarts, or dare you try all 4 right off the pad! Dual deploy ready.

You may commence drooling.

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AHansom

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Release the Kraken!!!! I think airstarts are a great way to fly and im sure youl like it. Look forward to watching you build and fly this.
I built a 4' Kraken A few years ago with a kind of Dueces Wild mm. So far the biggest sucessfull launch was a pair of J-350's off the pad then airstarting a I-161 then airstarting another I-161.

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jpummil

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Hmm...never really paid much attention to BlueTube...but the design......WICKED!

You have to do a launch video :wink:
 

AHansom

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Umm....how fast is this thing??

Not near as fast or high as a standard 3fnc rocket but after you calculate in the Kraken cool factor his rocket will be unbeatable

Salvage-1's motormount design should also give him a little more speed and better stability than my canted motors
if the motors dont ignite together.

http://www.youtube.com/watch?v=248ZLdN4Gis
 

fyrwrxz

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* m u s t-n e v e r-v i s i t-t h i s-t h r e a d-a g a i n...
(chest pains, rapid breathing, profuse sweating and alarms going off in my wallet)
OMG guys! I used to hate on tube fins but both of these are absofantasalutely >edited for public viewing<
 
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Salvage-1

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Not as fast as you would think... Although not quite the drag queen that a true tubefin is, the Kraken is still not the sveltest beast on the planet.

Definitely not the finished product, but, 80% there

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Salvage-1

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Started on the fin reinforcement this evening whilst watching The Avengers. I cut 4 sections that are 5" long but have the rear end sculpted back 1" to match the Kraken fins. Slice and fit inside the rear of the fin and then use my dremel with cutoff wheel to remove the bits that arent necessary. This will be glued inside the rear of the fin to double the thickness and really beef up the tube section.
I am trying to keep simulations under 15G peak acceleration. I am wanting to touch Mach with this beastie (down the road quite a way) and I dont wish to rip it to shreds.

Already changed design. MMTS will now be 2 x 15" and 2 x 10" This means that I can slide a 2x38 centering ring and secure it at the front of the 10" tubes, etc. and not have to rely on one 1/2" thrust plate. (see Rocksim pic on the post above)

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Salvage-1

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Scuffed up the matching sides and used wood glue to fix the inner section. Went over the whole thing with wood filler n spit. First round of 'fill the spirals' finished, now to leave it cure over night before smoothing it all out. Used wood filler to create a smooth transition on the front and rear.

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Salvage-1

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A little background on this project.

A while ago I had scared the moths out of my wallet and purchased a couple of the "Blue Tube Specials" from LOC/Precision. You get a 48" length of 4" Blue Tube, cut into 36" and 12" pieces, plus 38mm MMT tube, centering rings, coupler, bulkhead and nosecone. I have been eyeing them up and wondering what I could make. First project that came to mind was to stack them into a traditional two stager, booster and sustainer. About a month ago, I was watching AHansoms videos of his quad Kraken (see posting above) and thought to myself that I could mix the cluster idea that I had on my BT60 LPR Kraken into the 4" tubing and work a rocket that had clusters and staging. The Kraken design seemed to fit the idea due to its high drag and so the bird wouldnt go completely out of sight if the motors were chosen right.

This led to throwing together an idea in Rocksim. I asked Layne if he minded me upscaling the Kraken and he has no problems with it, as long as I document it for the Llamas bedtime reading. Ta Da!!

I am aiming at this being in the region of 7-8lb without motors. There will be a Stratologger in the AV bay to handle the laundry, as well as a timer, most probably the MT3G or its successor and my BRB900 GPS tracker on flights over 5K. If bank balance (or birthday/Xmas pressie) allows, then I am going to use a Raven to do most of the work, and use the Stratologger as backup. This will be my 'workhorse' for clusters and staging. The 38mm MMTs will also allow me to use 29mm and the H54 longburn as sustainer motors. I am looking forward to the new batch of 38mm's from CTI, I heard that they may have some longburns for this engine size coming soon.

Hopefully this will be a challenging scratch build and one that allows me to experiment and gain a lot of information along the way. Down the road, after a few flights, I am hoping to really push this beastie and try for Mach. Blue Tube is really strong stuff and so I should be able to get away with no fiberglass reinforcements if I build it right.
 
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Pem Tech

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Sexyyyyy...
Very sexyyyyyy...

Go man Go!
 

AHansom

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Started on the fin reinforcement this evening whilst watching The Avengers. I cut 4 sections that are 5" long but have the rear end sculpted back 1" to match the Kraken fins. Slice and fit inside the rear of the fin and then use my dremel with cutoff wheel to remove the bits that arent necessary. This will be glued inside the rear of the fin to double the thickness and really beef up the tube section.
I am trying to keep simulations under 15G peak acceleration. I am wanting to touch Mach with this beastie (down the road quite a way) and I dont wish to rip it to shreds.

Already changed design. MMTS will now be 2 x 15" and 2 x 10" This means that I can slide a 2x38 centering ring and secure it at the front of the 10" tubes, etc. and not have to rely on one 1/2" thrust plate. (see Rocksim pic on the post above)

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Interesting idea on fin reinforcement. Did you use the dremel to make all of the cuts? Where will the electronics for air-starting be located?
 
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Salvage-1

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Interesting ideas r us... no idea how this will work, but, now its cured overnight, it feels as strong, or stronger, than the dyna-wind fiberglassed section of tube that i have laying around, plus it is about 1/3 lighter than dyna-wind. Since I used wood glue (yellow) and wood filler, it still retains some of the 'spring back' that Blue Tube has.

Most of the cuts were made with a craft knife and razor saw. I am far better at scoring the lines deep and then following through with a razor saw than freehanding with the dremel. The cut off wheel only gets used when I want to do something that doesnt need a 'near perfect' edge. Only slight problem is that BlueTube blunts a razor saw quite quickly.

All the electronics will be housed in the coupler / AV bay. I am going to run an aluminum arrow shaft along the inside of the body tube to run the wiring, with a pull apart three pin audio header for the connection. I will keep it at 3 pins, instead of cutting it down to 2, so that I have an extra wire that I can use later. Will be nice to have a spare, or I will connect the - from each igniter to one wire, and then use a wire for each of the +'s.
 

MasonH

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I am trying to keep simulations under 15G peak acceleration. I am wanting to touch Mach with this beastie (down the road quite a way) and I dont wish to rip it to shreds.
15G's seem so small to me now...my H410 project peaks at 173G's...
 

Salvage-1

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Yeah, know what you mean. I have a 29mm Blackhawk that sims to Mach 1.6, 59Gee on an I243, but, that's not what I am looking for in this build. Although I can understand and admire the quickburners, I want to be able to see most of these flights :eek: 15 to 20Gee's should be more than enough for this style of airframe. If there is any chance of getting to high speeds with 'tubefin' design, it appears that punching it through the trans-sonic state would be worse than easing it through. Slow and steady acceleration looks like it stresses the airframe / fins a lot less than Mach in under a second.
 
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Salvage-1

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More info on the fin reinforcements.

I could have beefed up the Kraken fins a few different ways. Fiberglass was my first thought, but then I started thinking about the logistics of glassing the weird shape fin, how to 'tip to tip' , etc.. etc.. This lead to me looking at the spare coupler section that I had and using that. Measurements were against me. I had an 8"section of coupler and 4 fins, so, I could do an internal tube of just under 2". Another look around led me to the two sections of 4" BT that I had left over from the original two kits. One section was the 10" I had chopped off a 36" BT to get the lower section of the Kraken. The other section was the 12" payload BT that I hadn't used yet.
So, from these two sections, I realized that I could get internal tubes of 5" each. This would not only support the actual 'tube' section of the fins, but also extend nearly two inches forward as well. Cutting these with the flat front and scolloped rear allowed me to match up the back ends. Chopping nearly 1/4" from the 'top' then allowed me to fit the piece inside the fin. Added bonus is that this piece is like a spring and is putting pressure on the outside tube. Locking this together with wood glue meant that I got the strongest adhesion possible, whilst also allowing it to retain some elasticity. Now that it has been left overnight, the idea seems to have worked. The 'tube' section of the fin is rock solid.

To join the fins to the body, I will be using the wood glue again, with 4 short bolts going through the fin and body tube. One of these bolts will also be against the rear of the aft most centering ring and will be epoxied to the ring. Fill the rear cavities between the motor mounts with expanding foam and nothing should go anywhere that it shouldn't.

The other problem that I see with high thrust on these fins is that they only connect to the tube along one line. I am going to correct this by running a wooden triangular round dowel down the length of the fin on each side. This will provide far more surface area connection between fin and body tube, and also add a nice filet to the whole thing. Adhesive again will be wood glue, but I will then add thin covering of epoxy to finish the filet.

All this weight at its business end means adding a little more to the nose, but, the CP is so far towards the rear, I can compensate easily.

If anyone has any ideas or thoughts on this, throw em out.
 
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Salvage-1

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Motor mount assembly is dry fitted a looks good. Allthread to run the entire length of the assembly, shock cord point at fore end, washer and nut at the other for motor retention. Simple and it means that I know the motors are secured to the recovery system. Aluminum arrow shaft is in there as a conduit for the airstarts. Currently all held together with a 2.5" long section of 4" tubing, with a bulkhead at the aft end to center rod and make sure all motor tube ends are at the same place.

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Salvage-1

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Got quite a lot done on the motor mount assembly. Started by pairing a 15" and 10" and epoxying them together, did both sets. Both sets then got epoxied together to form the quad. Allthread was positioned down the center of the tubes, then on went the centering rings. Each position was checked and the rear two were epoxied into place. A pair of centering rings was then drilled for U Bolts. These were glued together with wood glue, and then the U bolts were positioned and epoxied on. When this was done, the double ring was installed onto the allthread and fixed in place.
At this point I started thinking about some support for the conduit tube. I was going to epoxy it to the inside of the body tube, but, I realized that leaving the base of the body tube 'open' was going to turn this drag queen into a soul sucker. This and the need for support for the rear of the allthread spawned an idea. Take one 4" ring and cut out all 4 holes for the 38mm motor tubes. This left me with a center and 4 side pieces. These got lightly glued into the rear of the mount assembly, and when I had checked and was sure that they would go in and out of the body tube, they were fixed in place. Next was to cut down the arrow shaft to 20" and mount and glue that.

Whilst I was checking and rechecking (and rechecking) the fit, yet another thought dragged itself through my head. I was already planning to put bolts through the joint of the fin and through the body tube to lock the fin. Why not rejuggle the positioning of the connections and use screws through the fin, body tube and into the centering rings. This would lock the motor mount assembly nicely to the body tube. I took another 38mm centering ring and chopped it up. These segments were then glued to the aft two rings to provide a good place to screw into, the fore ring, being a double, wouldnt need extra wood. I did this on two sides, so that I can used three screws down two sides of the body tubes. This line could be positioned to run along the base of the tube fin, or positioned between two fins. This could also be used as placements for the launch lugs.
That thought had a friend that tagged along. If I have now set this up to be screw locked in place, what is stopping me building other mounts with the rings in the same positions. Then what would stop me from being able to swap these mounts in and out. I could set this up with multiple 'motor mount assemblies'. Seeing as nothing appeared to be stopping me, I changed my plan, put together a single 38mm mount 'as a test'. Looks like it may work. Hmm, 54mm mount? Multi 29mm's?

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Salvage-1

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Using a couple of the 38mm 'holes' I cut earlier, I threw together a useful doodad which will let me close the rear of the two motor tubes that wont be used when this bird is flying on just a pair of motors. By using longer bolts, I can add washers to this that will help balance out the CG when the rocket doesnt have a full load of 4 motors.

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AHansom

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Using a couple of the 38mm 'holes' I cut earlier, I threw together a useful doodad which will let me close the rear of the two motor tubes that wont be used when this bird is flying on just a pair of motors. By using longer bolts, I can add washers to this that will help balance out the CG when the rocket doesnt have a full load of 4 motors.
Doodad's are always fun to invent and build but im not sure im getting if this one is needed. Im thinking if you load up the motor tubes that go all the way through, arn't the other two all ready blocked? Im also thinking that removable nose weights could be used to ballance the rocket and the rocket would weigh less overall in the less than full load flights.


Keep the build going lots of interesting ideas!!!!
 
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Salvage-1

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Couple of reasons for the doodad idea.
1- Base drag. Leaving two open tube faces at the rear would send the base drag right up ( I think )
2- Weight distribution. So far, the sims show me 4 motor setups with a CG-CP in the region of 1.1-1.4, using only two, the relationship was over 2.0. Adding the doodads into the rear of the motor tubes brought that back down to 1.5ish. The Kraken setup is a flared base tube fin, so I wasnt really looking at these numbers for stability, except for the windcocking aspect. The pair of doodads weigh 6oz total. Redoing rocksim, I found that reducing the nose weight when I fly with just 2 motors didnt do me much change for take off speed, etc, but it did rob me of nearly 300ft of altitude. Doing sims with the heavy nose weights, and the MMT plugs gives me 200ft more than if i reduced the nose weight, and speed is still in the acceptable ranges. In fact, adding that weight to the rear allows me to add another few motors into the usable range and still keep them under 900ft/sec

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3- protect the rear of the unused motor tubes from getting crushed with a hard landing, and overall extra protection for the rear.
 

Salvage-1

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mmt plugs in their new states. Double shock cord added. Loops at both ends of each, running to sturdy quick links.

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MasonH

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DAMN YOU PEOPLE FOR MAKING SUCH GOOD LOOKING ROCKETS!!

Looks great S-1, keep it up!
 

Salvage-1

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So, things are getting along slowly. My next HPR launch is this weekend, and it clashes with the kids schools 'Harvest Festival' fundraiser. I am now giving my cash to the school instead of sticking it up the tail end of this and burning it. I am actually relieved as it took some of the rush out of this. I got to the point where I had realized that I was never going to get it finished in time, what with all the extra fiddley bits I am planning, and the extra work that has gone in to this project.

Lets get up to scratch. Finished the motor mount assembly, then started on the filling of da spirals, ugh. That job took a while, mainly due to apathy which comes over me at this stage. Its not like I actively dislike the job, but I don't really look forward to it either. Fins then got stuck on to the body tube with Elmers wood glue. Prepping of the tubes was done with 100grain open cut sand paper, I want the glue to soak in and bond all the raised fuzzy hairs together. Got both sets on, and the bird is starting to look like a Kraken now.
I also got the time to put together an AV bay. It is a little of a throw together, using the parts that I had on hand. 3 sets of terminals at each end. Top one will be wired to main deployment charge, bottom will have drogue charge and airstart connections. Extra set at each end for 'backup' charges, if I go that way, and since I have found that I have a 'spare' Adept22, I am definitely thinking of putting that in as a backup.

Friction fit the motor mount, added all the shock cords and chutes, etc. Main will be two 4 ft parabolic cups, drogue will be a 24" flare chute. All in at the moment it weighs bang on 7lb. I still have wiring, switches, two altimeters, charges and holders, etc to throw in there, but all that weighs less than one chute. I am thinking I will be adding a few ounces of paint too, although I like the bluetube look and may just do clear coat and floor polish.... nah, need something garish!

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Salvage-1

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Also have a 5:1 pinnacle nose cone on order, want to see how it looks with that on before I make final decision of pointy end. CG at the moment is 2" in front of the pointy end of the fins, needs to be moved forward at least another 4". Prepped a bag of .375 and .454 round balls from muzzleloading supplies and worked out that with this nose, I need 3/4lb of lead up there. The pinnacle nose is 5" longer, so I may be able to make it 1/2lb. This all depends on how much extra weight goes into making the bulkhead for the nose, etc. I have already cut the rear off the nose cone and plan on adding 4" bulkhead in there and a U Bolt.

I am planning this as a minimum 7.5:1 power ratio, so I need an minimum of 250-300N/s to get his safely off the pad and at speed by the time it gets to the end of the rail (which I think is 7 or 8 ft, calculating at 7ft to give wiggle room). A pair of H143SS should be the lowest impulse according to this. Dual H225WT's would be a nicer option, but less 'ink'.

Now to a question for you folks. Is it safe to light the airstarts one at a time with a delay between the two, or should they both go off together?
 

Salvage-1

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For comparison
LPR Kraken --- King Kraken -- WARPed Kraken

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