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3" Loc Isis Build

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peter_stanley

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I've been working on the 3" diameter Loc Isis (which is really a 1/4 size sport scale Iris) for the July launch in Orangeburg. I only have a 1.5 weeks to finish it, but think it will be done. So far I've built everthing stock, except I converted the payload coupler to an altimeter bay. I installed t-nuts in the rear centering ring for motor retention clips. Also replaced the elastic shock cord with tubular nylon. I would like to have replaced the screw-eyes with forged eye bolts, but I don't know where to get those. Also, looked for u-bolts, but didn't see any small enough. Everyone says don't use those standard eye-bolts. So far I have never had an issue. I'll accept the risk.

The altimeter bay probably has taken the most time, but I'm very pleased with how it turned out. I performed a ground test with the perfect flite altimeter last night by sucking air out of the static port to create a vacuum and simulate a pressure change. Everything worked great.

The only things left to do are fillet two more fins, install rail buttons and attach forward section to altimeter bay. I'm not as concerned with finishing before the launch, but would like to at least get a good coat of primer on it.

I should have been posting this all along, but have been more busy building than writing. I did cross-post this on my blog, with a few changes.

Here's a pic after opening the box. The fins and centering rings appear to be high quality 1/8" 5 ply birch. The bulk plate is 5 ply 1/4" birch. Everything looked great, but the pre-slotted slots were not precisely made perfect from one another. I worked around that.



38mm motor mount tube.



I used a tube stiffener in the coupler, and left enough room on the ends for the bulk plates. These were held together with all-thread. The altimeter is mounted on a piece of stiff board glued to a 1/4" tube which slides up one of the all-thread rods. I cut 3/4" of the bottom body tube section and glued in the center of the e-bay. This provided a good place for the static port and a permanently mounted switch. I used a Newton's 3rd Rocketry screw-in switch.













I made an alignment template for the fins. I did notice that the slots were not perfectly spaced from each other. This prevented me from using the entire alignment guide. I cut it in half and used it for one fin at a time. I'm using 30 minute epoxy to fillet the fins. So far two sets are done.





Here are my motor retention clips.



and me...

 
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patelldp

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Word of advice: You may want to be careful hanging clips over the end of snap ring-type cases. There have been cases in the past where the metal will heat and actually cut a divot into the case. I would suggest retaining it by the thrust ring, that way the clips are out of the exhaust path.
 

peter_stanley

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Word of advice: You may want to be careful hanging clips over the end of snap ring-type cases. There have been cases in the past where the metal will heat and actually cut a divot into the case. I would suggest retaining it by the thrust ring, that way the clips are out of the exhaust path.
That makes sense. I'll do that. Thanks for the suggestion.
 

DAllen

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IMHO I think the 1/4" threaded rod (that is 1/4" - right?) is a tad overkill. You could easily get away with 10/24 or smaller rod. 6/32 size rod would be plenty in a rocket that size. The smaller rod will save you a lot of weight. Then instead of using a 1/4" launch lug for your sled you could use a 1/8" lug with 6/32 rod.

Just out of curiosity, what are you going to do to keep the sled from rotating freely on that rod? From the photo it looks like your sled could rotate around the rod and bang against the sides of the ebay. You could shake a wire loose that way during drogue deployment.

Looks like a fun build. What motors are you planning on flying it on? Methinks the 38/1080 case might fit in there. :y:

-Dave
 

peter_stanley

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IMHO I think the 1/4" threaded rod (that is 1/4" - right?) is a tad overkill. You could easily get away with 10/24 or smaller rod. 6/32 size rod would be plenty in a rocket that size. The smaller rod will save you a lot of weight. Then instead of using a 1/4" launch lug for your sled you could use a 1/8" lug with 6/32 rod.

Just out of curiosity, what are you going to do to keep the sled from rotating freely on that rod? From the photo it looks like your sled could rotate around the rod and bang against the sides of the ebay. You could shake a wire loose that way during drogue deployment.

Looks like a fun build. What motors are you planning on flying it on? Methinks the 38/1080 case might fit in there. :y:

-Dave
It looks a little big in the pic, but the rod is 10-24. Thanks for pointing out the need to keep the sled from rotating. I've got some soft packing foam. I think if I glue some underneath the sled edges that'll help. I've done that before and it worked ok.

I'm flying it with a 38/740 case. I haven't calculated the motor designation yet, but I think it's supposed to be around J-540 give or take.. It's from a Thunderflame mix kit (SRB flavor). Going to fly it on the 11th at Orangeburg. Based on the weight and approximating the motor, Rocksim estimates around 5300'. If it survives ok, I might invest in a longer case :cyclops:
 

rstaff3

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The build looks great. I wouldn't sweat using standard eye bolts on that sized rocket. It should really get out of Dodge on a J :)
 

peter_stanley

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Had two great flights this weekend, but one not-so-great recovery. On the second flight, the charges didn't go. The altimeter beeped correctly on the pad, and I used a new battery. I don't think it was the altimeter though. It was a fairly new Perfect Flite. I ground tested a few days before, and it worked on the previous flight. I think it was my fault in how/where I mounted the battery. It probably either disconnected or hit/jarred the altimeter. I need to really rethink how I mount everything. Here are the remains.







My beeline transmitter and altimeter were destroyed along with most of everything else. the motor was ok, but I deformed the nozzle and thrust washer getting them out. The case of forward closure are fine.
 

Rocketjunkie

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Peter,

I got at least one of the flights on video - at least the liftoff. They were fast :y: Look for a frame capture on the TripoliSC site soon.
 

peter_stanley

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Peter,

I got at least one of the flights on video - at least the liftoff. They were fast :y: Look for a frame capture on the TripoliSC site soon.
Thanks,
Can't wait. I have some video too, but not sure who all or what. My wife was shooting it. I'll try to capture and process tonight.
 

Handeman

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Sorry to see your rocket like that, shovel recovery is never very good.

It does sound like the problem was probably a power disconnect in flight if everything worked before.

I don't know how you mounted your battery, but I mount mine with two tie wraps directly to the sled, one around and one end to end. I also use a snap on connector with it's own wire leads to the altimeter and I mount the battery so the terminals are facing forward. I've had no problems, and that includes a ~80 G flight on a I1299N.

Good luck on the rebound!
 

Viperfixr

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Peter, it was great to meet you last weekend at Orangeburg (Lauren and I were next door in the Honda Odyssey), and your Isis was a superb rocket--very sorry to see it's end. With your building skills, I am sure you can have another up and running in no time.
 

peter_stanley

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Peter, it was great to meet you last weekend at Orangeburg (Lauren and I were next door in the Honda Odyssey), and your Isis was a superb rocket--very sorry to see it's end. With your building skills, I am sure you can have another up and running in no time.
Thanks Mark. It was nice meeting you and Lauren, and your dogs. I don't know if you've checked, but there are a few pics of Lauren's Dragonfly on the ICBM site.
 
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