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I've been doing a detailed build thread on my Facebook page, but figured it'd be appropriate to give an abbreviated thread here.

based upon the 1987 movie directed by Clive Barker.

7.5" LOC tubing, kevlar anti-zipper bands, 1 ply 7781 FG wrap.
Ogive FWFG nosecone by Rocketry Warehouse
98mm MMT
Bulkheads, Interlocking Centering Rings, and Fins 1/2" ply cut by Nat, Upscale CNC.
Harnesses by One Bad Hawk.
Telemetrum 2.0
Raven 3
Blastcaps x3 pair
Through-bulkhead terminals by Doghouse Rocketry.
Y-Harnesses by One Bad Hawk
Apogee event: 24" x 25' Streamer
Main Event: 48"Fruity Chutes Iris Ultra pilot, 96" Fruity Chutes Iris Ultra in freebag.
Nosecone recovers separate
75/98mm Aeropack adapter
Aeropack retainer
127" tall
23kg (ish) pad weight
CTI M-1770SK

Projected altitude: 6,500ish
Velocity: 750-800FPSish

[Image: 11263080_10204400256432395_8732896918188...e=56A198CD]

7.5" Hellraiser Nosecone vs. 5.54" Mondo Kraken Nosecone.  L2 bird and Elmore Leonard novels look on.   

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My pet mouse, Wayne, inspects the coupler assembly before epoxy is mixed, and approves.

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Making my super high-performance fin marking guide: wrap paper around the airframe, fold in half, then half again.  Works on Estes, works on LOC. 

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Slot Cuttin'.  I thought it was kind of neat that you could see the whizzy wheel flexing, here.

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Slots cutted.  They go all the way to the end to permit the interlocking fins to be assembled outside of the airframe.

More later...

Moving on: Fins/ CRs and MMT

Fins and CRs are by Nat, at Upscale CNC. He also did the stepped bulkheads. Wood is 1/2" Birch ply, and his work is fanTASTIC. If you need custom-cut wood for your project, I'd suggest you shoot him an email. Prices were very reasonable, and the product is first-rate. I will cheerfully use his services again.

Anyways... it goes like this.

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Two of the CRs are cut to fit inside the coupler. This is the test-fit.

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The fins get a 3/2/1 layup over the wood. Overkill? Perhaps. But It makes me feel better, and I'm not overly concerned with weight. I'm mildly apprehensive about them snapping on landing, so I gave them the reinforcement and will hope for the best. Tape is placed over the interlock sections to make installation easier.

[Image: 10304502_10204643251507120_1344341762400...e=566911C9]

Once glassed, and the tape removed, the fins are prepped for installation. Here, you can see the dado cuts in the aft CR for the fins.

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Despite my careful handling of this step, the fit was a bit too tight. Some... persuasion was necessary.

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Fins and the CRs happily ever after on the motor mount.


Airframes, PT Deux: lower/fin can connection, av-bay mounting and switch holes.

I have a 2000 Subaru. component size is dictated by trunk space. Therefore, to permanently attach the lower airframe to the fin can, creating a 60" tube is simply not feasible.

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During mock-up, holes are drilled in the upper airframe into the coupler. Threaded inserts are epoxied into the coupler. 8 #10 screws in a staggered pattern bolt the lower airframe to the fin can.

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The top two centering rings are mounted in the coupler, with the coupler insert installed. The threaded inserts are visible up near the fore CR.

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Marking switch location for the av-bay on the upper AF. This particular tube was going to be used on something else, which is why the spirals are already filled. It added a little bit of weight, so that's why it's serving as the uppermost airframe section.

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And the holes drilled. The one looks a little rough, I admit. I'll get her cleaned up by flight time. The av-bay is attached to the upper AF by 4 #10 screws and threaded inserts, similar to the lower AF/fin can. This will let me transport the rocket in Subaru-sized chunks, and assemble at the field without too much trouble.

Next: layup.


Nice keep posting!
Layup and Anti-Zipper technique...

At the advice of Robert DeHate, who is graciously acting as a TAP for me, Kevlar anti-zipper bands were incorporated into the layup at the break points.  I'd never used Kevlar in a layup before --only as shock cords-- so this was a new experience for me.  Not altogether difficult, once I got the stuff cut --which, lacking specialized tools to do so, was a bit of a challenge.

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Prior to doing this, the bench was covered, FG, Kevlar, and peel ply weighed, then epoxy mixed for that weight.  I used Aeropoxy... something with 3's and 6's, if memory serves... whatever the laminating formula is.  I laid down a bed of epoxy on which to lay the Kevlar anti-zipper band.

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Here's the aforementioned band.  2" wide Kevlar ribbon.  The end looks so ratty because I wasn't about to drop $80 on Kevlar shears to make two cuts.  Perhaps in the future, I will, and incorporate more Kevlar into my layups, but it didn't seem worth it to me this time out.

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One of the things I noticed about Kevlar (which I read before) is that it's not as easy to tell when it's wetted out.  FG has the courtesy of turning clear to give you indication of wet-out.  Kevlar owes you no such favors.  I used thin nitrile gloves that may or may not have been acquired from an emergency department when a certain cute nurse asked me to start the IV on a difficult and combative patient.  The thin gloves really let me get a feel of the material as the layup progressed.  I wasn't particularly concerned as it was going to be a single layer of Kevlar under FG, but still wanted to determine for myself what it was like to work with this material.

[Image: 10425060_10204669246796986_8853500794273...e=56733ED6]

FG went on without issue, and then a layer of peel ply.  After this was taken, I worked it a bit more to remove excess, but here you can clearly see the Kevlar band under the FG.  Yes, the OD at that end is slightly larger than at the other.  Slightly. Body work after curing will conceal it further.

The idea is to prevent zippers.  Will it prevent a zipper from forming that would otherwise occur?  I don't know, and really don't have the time, money, or means to set up a useful experiment to determine its efficiency to this end.  But I like the idea.   The way this rocket is configured, there is a Y harness--two attachment points inside the airframe.  These two points go into one past the tube opening.  So, rather than one contact point from the recovery harness, there are two, which by itself distributes the force over a wider area and should reduce the chance of a zipper.  Way I figure it, any extra strength at the potential contact points further reduces this likelihood and can't be a bad thing. 

Some may ask: "True, but is it NECESSARY?"  I cannot answer, but welcome discussion on the topic.  What are your thoughts?

Next: Av-bay.



(09-13-2015, 08:41 AM)wclune Wrote: [ -> ]Nice keep posting!

Thanks much!  I hope to launch her at Higg's Farm, at the earliest available opportunity.


Av-Bay Exterior

Rather than purchase an av-bay kit, I had stepped bulkheads cut for me by Nat from Upscale CNC.  They were cut a smidge oversized, which required sanding down for a good fit, but this is the way I prefer it anyway.  

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To mark the interior of the bulkheads, I drew a centerline, then used one of the centering rings to mark out a 4" circle.  

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I figured where the center line and circle intersect is a good place to drill for the allthread.

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To figure spacing for the hardware attachment, a similar approach is used.  There are two points on this side (top), and one on the lower.

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Here's the result of those efforts.  

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The terminals are a new style for me, but I rather dig them.  These are through-the-bulkhead type from Doghouse Rocketry.  The supplied screws are plenty long enough for most bulkheads, but a wee bit short for these, as they're 1/2" thick.  The screws were replaced with longer versions.  Also, somewhere in there, the face of the bulkheads got a layer of glass that was laying around doing nothing.  

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Switches are the rotary Schurters.  There's one for each flight computer.  the 1/2" hole drilled in the airframe permits the body to pass through, but the bezel sits on top of the av-bay... which will not do.  Countersinking is necessary.  

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After a brief, satisfying affair with the step bit, the switches sit flush like they're supposed to: Easily accessible from outside the airframe, without the switch band.

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Six Blastcaps are added... three on each bulkhead.  Simple, slick installation here: place, screw, done.   These are the medium-sized versions... don't figure I'd need more than 4 or 5 grams per charge.  These'll hold up to 8, so I've got plenty of wiggle room.  

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Vanity.  Pure vanity.  That's why I painted the av-bay.  There were too many squiggles and marking lines on there for me to process.   I figure it's permissible, as how often do you make a L3 attempt?

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And the top bulkhead, all complete.  Figured I should paint the bulkheads, too.  

Fun fact: the only thing I measured thus far is the switch holes off the centerline, and the vertical position of the screws from the end of the tube.  Everything else was derived from known figures and impromptu tools, like the CR and paper wrap.  This low-tech approach must have worked, because the slots lined up with the CNC'd dado cuts in the CRs.  

Next: Av-Bay interior.


Av-Bay, Interior:

Hellraiser is running a Raven 3 and a Telemetrum 2.0.  There's enough room inside this av-bay to make this happen several times over.

[Image: 10986844_10204598481667902_6247335398355...e=56619A92]

Here's my trusty Raven 3.  She's been in at least 4 different rockets: Hornet, Goblin, Phoenix, and now, Hellraiser.  That said, this will be the first time I'll be using it without the Power Perch, as I want the rotary switch rather than the magnetic one inherent to the Power Perch setup.  Normally, I'm a fan of the magnetic switch--just not on this project.

[Image: 10650060_10204791506133393_3565039415676...e=569E11C0]

I used JST connectors to connect components to make it easy to remove the sled and transfer components between other av-bays, so I did a fair amount of splicing, soldering, and heat-shrinking.  In the background, you can see the Telemetrum computer.

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While I could have used a 9v or other battery, I opted to use the standard 3.7 LiPo for the Raven 3.  In order to secure the diminutive power supply, I fashioned a small battery holder, as there wasn't a commercial one available to the best of my knowledge.

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Crude, but functional.  A single #2-56 screw is used to secured the crossbar.  

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Some odd RFI was noted during testing... addition of the ferrite choke, here, improved things dramatically.  

Next: Airframe assembly.


Airframe Assembly

As the rocket was designed to break down into Subaru-sized chunks, there is very little permanent bonding required.

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The coupler is prepped by vacuuming off any dust. There is a single hole in the bonding area which was taped off from the back. This is where the rail guide attaches. Above the bonding area masking tape is wrapped around the coupler to keep excess epoxy under control.

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Evidently, such a plan actually works. I let it set up, slightly, before removing the tape.

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The fin/motor mount assembly is epoxied in place. As the slots went all the way to the end of the airframe, a coupler and insert are epoxied in place to fill the voids. After insertion, large hose clamps are placed on the outside of the airframe and kept tight until the epoxy cures.

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So, here's the assembled fin can.

Next: Fillets ...and blood!


Fillets. And BLOOD!

I was going to jump right to primer/paint, but then realized if I do not show a photo of fillets I'll be flogged. So in the interest of self-preservation...

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These are the fillets at the MMT/CR/Coupler joints.

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Here, I'm making the fin fillets. These were taped off and shaped with a piece of PVC pipe that was laying around not doing anything in particular.

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And here's one from the back. I apologize for the photo quality. Each fillet was approximately 12.5g of epoxy--a small amount of which wound up being scraped into the fin slot.

[Image: 11831727_10204937994475510_5182495697943...e=5698E9CF]

During trimming, I nicked my fingertip. A drop or two of blood fell into the motor mount. Have you seen the original Hellraiser film? If the rocket starts building itself, I'm going to be slightly worried.

Next: Primer/paint/Decals


Coop if your rocket starts building itself Robert is going to disqualify your L3.....
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