I plan to do a build thread on my X-Celerator from Rocketry Warehouse.

This is an all fiberglass rocket, about 7 feet tall and 4" diameter. It comes with a 54mm motor mount. The kit weighs a little over 9 pounds.

I will have a thread on multiple forums as I am looking for advice. As my title indicates, I will be using this to get my L2 certification. This will be my first dual deployment rocket, which also means my first with electronics. These initial threads will be on my design.

Please let me know if I am doing anything wrong or stupid!

I know I am somewhat over-engineering this. I am not looking for a mach-breaking, sky ripping, hit the moon extreme flight. I want the rocket to return safely and get me my L2.

So – where do I stand…
I took advantageous of the various sales after Thanksgiving, one to buy this kit, another to buy CTI hardware and reloads, and another for decals (wait until I actually have it built – the decals from Stickershock are going to have a WOW factor!)

I did stay with 38mm hardware. The 3G and 6G CTI hardware with spacers were on sale. With these, I’ll be able to do more with my L1 Ariel plus I have a few other kits for 38mm. This means I will need an adapter. While not on sale, I did buy the Raven 2 Altimeter.

I included a sketch of the rocket. The main tube is 42” long; the upper tube is 24” long. Unfortunately, it does not show up well.

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Here is one of my cases of inexperience…

I plan to add a plywood bulkhead to the fiberglass bulkhead for the nosecone. I will use a T-Nut in the plywood and ¼” screw eye for the harness. This will be epoxied into the nose cone. I am still debating if I should fill the cone with a 2-part expanding foam.
When I fly, I plan to use 2 or 3 #2 nylon screws as shear pins to hold the nosecone on.

Does this sound right???

For the motor, I also plan to add a plywood bulkhead. I am going to use an Aeropack retainer. My thoughts are the plywood will give me something for the inserts that hold this retainer in, plus I will add an insert from the side for the rail button. The plywood may need to be “sliced” to work around the fins. Again, I am still deciding on foaming the can.

When I build, I plan to epoxy (after roughing up all appropriate fiberglass) the front centering ring and just slide the rear ring on to center the motor mount tube. My harness (still deciding on Nylon or Kevlar) will be epoxied to the motor mount tube. I will epoxy the top fins in. Then apply internal fillets. Install and epoxy the middle centering ring. Epoxy the bottom fins in. Do the internal fillet. Finally install the bottom ring with the plywood bulkhead.

Am I heading in the right direction?

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Based on the advice from replies to my post, I will be changing to a U-bolt for the top motor mount CR to attach the harness to. I’m still deciding on the all thread for the nose cone. At nearly 7’ long, I’m not sure I could make it unstable if I tried (LOL)

Now for the Electronics bay. The kit comes with an 8” long coupler with a total of 4 – 3/32” thick bulkheads; 2 that will fit inside the coupler and 2 that will not. Again, I plan to add plywood to these bulkheads.

The bottom set will be epoxied to the coupler. There will be a ¼” eyebolt for connecting to the harness. I saw a post suggesting using a carbon arrow to slide over the all thread for the sled. What I found was it would not fit over ¼”, so I am planning on using 10-32 thread (I may add a 3rd piece to balance the load).

The top will have a “thick” plywood piece that will have 6-32 inserts into the sides. The plan is to have 6-32 bolts (metal) through the airframe, through the coupler, into the inserts to hold the electronics bay in place. There will also be a ¼” eye bolt on top for the main harness.

The sled will be epoxied to the arrow shafts to slide over the 10-32 all thread. Lock nuts will be used on the all thread to seal it shut.

I also have a strange idea for providing electrical connections through the bulkheads. Use a brass bolt, a terminal lug, and a nut to make a tight electrical connection. There will be a washer to spread the force to the bulkhead. On the other side of the bulkhead, there will be another washer and nut to secure the bolt. Finally, another terminal lug for electrical connection and nut to secure this. So the protruding bolt is my “terminal block”. Thoughts?

Now for my biggest dilemma. Quite frankly, this has turned out to be more expensive than I anticipated (now I know why I never went for my L2). The Raven2 supports 4 channels of output. The default is Drogue, Drogue Backup (delayed from Drogue), Main, and Main Backup. So I can have multiple igniters and charges for redundancy – but this is still all dependent on 1 altimeter with 1 battery. Should I really spend the money for a second altimeter? And then do I set up a third set of igniters and charges?

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Interesting project.That is a fine looking kit..I do believe that you are, as you yourself stated, over engineering this a bit..A few comments:

Nosecone: An eyebolt thru the hole in the fiberglass bulk head should be sufficient..No need for a plywood one there as well..Just use a couple of washers, a lock washer and nuts..You can foam the nose cone, not necassary, it will help stiffen it some, and help if you have a rough landing.

AVBAY: Again, I would do away with the added plywood bulk head..I subscribe to the KISS method..Just use the parts in the kit..As far as attaching the avbay to the payload tube, I use nylon push/pull rivets- they work fine. I would also stay away from all those electrical connections to get power to your ejection charges. Just drill a small hole in the bulk heads and run the wire direct from the altimeter to your e-charges(less connection=less failure points).

Motor retention: I would also do away with the added plywood centering ring here..There should be plenty of material for the retainer bolts/screws to bite into..

Altimeter: Just go with the single altimeter. And single charges for each event..Again the KISS principal..

__________________
Jon
SAM #0396
BAR 02/07
NAR 86940
KF4GUL
Aim high, fly straight!

Well, I’ve decided to bite the bullet and get a backup altimeter. I am trying to decide between the P6K and the RRC2. Both will provide a basic Drogue and Main DD.

A few more questions for all the experts. I plan to use the Quest Q2G2 igniters, vinyl tubing, and Pyrodex for my charges. From what I’ve read, you hot glue the igniter into one end of the tube, pour in the right amount of Pyrodex, and seal the other end. I understand Pyrodex is not good as black power, but NYS does not allow the sale of BP. I understand I will need to wrap this up good and tight to make sure it burns properly. Does this technique sound right?

Also, suggestions as to how/where to secure these charges?

Then, the harness from the nose cone/electronics bay and main chute, and the same for the electronics bay/motor & fin section and the drogue. Can one long harness be used between 2 sections with just a loop tied to connect the chute, or are 2 harnesses (one from each section to the chute) required. Also, can the harnesses be tied (I know, less preferred) or do they need to have sewed loops?

I think I’ve just about got this design together…

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I have heard of one case in which a Q2G2 igniter was not compatible with an altimer and lit before it was supposed to. I will try to find out the model of altimeter which was involved, but in the meantime, ground test a Q2G2 with your electronics before adding any powder.


Bill

I want to thank everyone who has provided comments.
My other “hobby” (what I do to pay my bills) is being a design engineer. As an engineer, I recognize there are always tradeoffs between cost, weight, strength, ease of use, etc. There have been various opinions, some contradictory, and I’ve read them all, and I’ve decided which way I am going.

They say, for every project, there comes a time to shoot the engineer and start production (hey wait – I’m the engineer! ).

My first picture is of the kit. The Alpha does not come with the kit – I included it for scale.

First thing I did was sand the fins, CR, and tubes. I used tape to mark the limits of where to sand. Based on a suggestion, I also used a Dremel to make some grooves for the epoxy to grab on the fins.

I then drilled one of the centering rings to add the U-bolt. I used lock bolts on the bottom and washers top & bottom. I also epoxied everything when I was done so it can’t come loose.

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Trouble!
I work on my rockets in the family room so I can watch TV while building. My wife insists I clean up every night. I was trying to get something from the box when the nose cone fell on the concrete (I store the stuff in a utility room at night) and broke the tip of the nose cone off.

Where is that engineer? Fortunately, I only got a flesh wound – in the fleshy part of the heart (anyone remember what movie that was from?). So – we have the technology to rebuild it – Epoxy! I rolled a cone, filled it with epoxy mixed with micro balloons (they are brown), but it on top, let dry, and sanded. It should be OK.

The other issue I ran into is when trying to rough up the inside of the tube; I realize my arm just barely reached. How would I attach the harness to the U-bolt? So I purchased some wire rope and made a leader. The end is still within the tube so the strap will hit the edge and not steel (trying to minimize the chance of a zipper). On hindsight I wish I used a thinner cable, but what I got will do.

The epoxy is now drying to secure the motor mount into the airframe (only the top CR is being glued). The bottom CR was slid on to keep the MM centered. Once I start gluing the fins on, I will have it out so I can do internal fillets.

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I made a template from foam board. I’ve got the three front fins glued on. I’m working on the internal fillets now.

To support the cost of a backup altimeter, I’m thinking of changing to the PML Positive Motor Retention.

Also, I did get an Aeropack 54/38 adapter. It is only 7” long. The motor case is 16” (6G). Is it OK for so much to be unsupported?

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Looking good! And yes, you will be fine with the adapter, as I am sure the casing is longer then the motor tube anyway..as will the bigger 54mm cases will be when you step up to the higher powered loads for this bird.

__________________
Jon
SAM #0396
BAR 02/07
NAR 86940
KF4GUL
Aim high, fly straight!