Binder Design Excel with Dual Deploy (54mm) build

woferry

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Hi,
Still fairly new to posting on this forum (and HPR, I flew a few small model rockets growing up, but a co-worker took me to XPRS in 2012 and got me hooked), I've built two HPR rocket kits so far, both GLR (Thunderbolt and Bumbl-B mk III), but this will be my first build thread.

As much as I love the pre-made fin-can idea, I figured its time to try to build up the skill-set (and the number of tools/fixtures in my garage) on doing fins myself. The fact that the Binder Design Excel basically involves building your own fin-can seemed like a good first-step. Plus I was looking for a larger rocket than the minimum diameter ones I've built so far to be able to fly more electronics, have more room to work with recovery bits, etc. I'm definitely not ready to start playing with FG yet, so I chose the Excel w/DD still using plastic and whatever paper-ish material the BT is made from. My goal here is to hopefully get a solid DD flyer, and likely use this for my L2 so that I can fly it higher with some of the larger 54mm motors (realizing that you can't fit the longest cases in this rocket).

For my previous two rockets I had a name and color scheme in mind at the time of (if not even before) ordering the kit. In this case I have a definite color scheme in mind (dark red + black, using Dupli-Color Effex clear over it for a color-changing effect, as I fell in love with the look of dlb's Wildman Jr), but I'm at a complete loss for a name. I think the color effect with red & black would look like some snakes, so I was hoping for a cool snake name (I guess it helps that I had just watched Kill Bill during the holiday), but it seems these colored snakes have totally unimaginative names like "red-bellied black snake". :p If anyone has any suggestions I'm certainly listening. The OR model really only roughly indicates what will be red & black, the nose cone, avionics bay band and fins I plan to make red and the rest black, except the bottom tube around the fins which will probably be a mix (I liked the pattern on Stewart's Excel DD so I'm planning to mimic that).

I did make two deviations from the stock kit at ordering time, as suggested by others on this forum I asked for the longer motor mount tube (came in at 17") and extra centering ring for it. It seems good to have the longer mount in general, and moving the shock cord anchor higher-up in the tube so that it might still be somewhat accessible seems wise. I also stated at ordering that I didn't need the motor retention as I plan to use an Aero Pack retainer, figuring that might help offset any extra expense Binder might incur for the extra CR & MMT.

Opening the box revealed basically all of the parts I was expecting (and it sure looks nice!). The kit included 1010 rail buttons, for some reason I was expecting a launch lug so I had already ordered buttons separately (I love the Acme conformal rail guides, but have already caught enough flack at launches about the aluminum guides so I figured I'd use the Delrin buttons on non-MD rockets). The included buttons have very short screws and lack a T-nut for the interior, so I'll probably still use the guides I ordered separately which include the T-nut. Two tubular nylon shock cords are included, I'm thinking of switching those out with kevlar since that's what I'm used to from the GLR kits. The main chute is 40" and looks very sturdy, I was rather surprised by the 12" drogue which feels inadequate to me for a rocket of this size & weight, and according to my OR model even with the 'dry-weight' rocket (before adding electronics, epoxy/paint, etc) will come down at 80ft/s (>50mph), which OR warns is fast for deploying the main. A 18" chute looks much better in OR (right around the 50ft/s that generally seems to be recommended speed from what I can tell) so I will probably replace this chute. No chute protection is included either and I'm not too keen on stuffing the tubes with 'dog barf', so I'll likely pick up some nomex/kevlar chute protectors as well. There are also no quick-links for the recovery (just eyebolts for the avionics bay and lower section, with a plastic loop on the nose cone side), which I'd rather have especially if I stick with (or start out with) the nylon cord. The avionics bay kit includes a screw switch, I've used the Featherweight magnetic switch before and liked that, so I have another pair on order for this rocket (for redundant electronics).

So here's the kit as received. I actually ordered two Excels, one DD and one not, the non-DD one is for my dad to build later this spring (I took him to XPRS in 2013, he built/flew a GLR T-Bolt in 2014, and was looking to build a bigger rocket for this year). So the rightmost 3 pieces and bag of bits are for that kit, the rest is for my Excel DD (the pair of extra centering rings is near the middle).

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I did a dry-fit of all of the parts (including throwing everything else inside the tube) and weighed it. Came in at 66.3oz. I weighed each major component separately and built as accurate of an initial model in OR as I could (I don't have the Aero Pack retainer yet, so that's missing). I intend to be re-weighing things regularly as I replace/upgrade bits, sand, epoxy, paint, etc. I don't plan on going out of my way for a light build, but would like to get a better understanding of how much weight gets added in the process. I did notice (and I believe I had read it elsewhere, probably on this forum) that the nose cone OD is a bit less than the body tube, so there's a noticeable discontinuity where the two come together. Not sure that I'm going to do anything about that however.

DSC02924.jpg DSC02925.jpg Screen Shot 2015-01-10 at 9.02.47 AM.jpg Screen Shot 2015-01-10 at 9.15.07 AM.jpg

Other than the longer MMT and upgrading some recovery bits as mentioned above, I don't plan on going too custom with this build, most of it will be as recommended in the instructions (I also have a LOC Minie-Magg on order that I plan to go more crazy with, that will get its own thread). I do want to fit my Eggfinder in the nose cone, I don't want to remove the center portion of this nose cone's base, so I'm hoping to be able to drill a hole for either BT-55 or 29mm tubing off-center on the NC bottom face (which angles in anyway), and fitting a piece of wood in so that it doesn't require all-thread (with pins/screws in the back to hold things in place). This would also help for adding some nose weight if I ever decide to fly this in the shorter (non-DD) configuration. I also have a Mobius ActionCam that I plan to fly on this rocket, so I have a camera shroud on order from Landru13 (I've flown one of these on Bumbl-B and really like it, link to my first videos in the signature).

Unfortunately, since I don't have the retainer yet I won't be starting with the fin can, as I need the retainer to ensure I position the thrust plate properly on the MMT. I do have some prep-work to do anyhow, I want to build one of the fin alignment jigs as from this thread. I also picked up a drill press from Lowes that I need to put together, and I want to build my own paint booth as well. But I'll likely start the build with the avionics bay. The grooves aren't as pronounced on this tube as the GLR Magna-frame, but I'll probably start out filling them to kill time. I want to try this trick of 'soaking' the ends of the tubes in CA, though I'm not quite sure the proper CA to use for this, is it something I can buy at a hardware store or do I need more of a hobby/craft shop or something? Everything I see in HD/Lowes that is thin claims to be instant-set which scares me.

I'm hoping to have this ready for the local February launches (LUNAR and/or TCC), we'll have to see how much time I get to work on it this month.
 

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watermelonman

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Why lengthen the motor mount tube at all? I am running 16 inch motors in a 10 inch tube on my favorite 38mm bird. Sounds awesome overall, though!
 

woferry

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Moving the shock cord anchor farther up the tube seems like the best reason. That CR will be right around 16", which is where Binder suggests the upper button should go. So I might thicken up the back of this plate a bit (another piece or two of ply), both to have something substantial to connect the rail button to as well as perhaps put the eyebolt through as well.
 

Binder Design

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The main chute is 40" and looks very sturdy, I was rather surprised by the 12" drogue which feels very flimsy,

We use zero porosity coated balloon grade fabric for all of our chutes. This is different than most of our competitors and will offer slower descent rates than non coated standard rip stop. Many of these kits have been recovered under drogue without damage when the main has failed to deploy. This is the first report that we've had that they might be inadequate.
 

woferry

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"very flimsy" was a poor choice of words, I more meant to say "inadequate". I've corrected it above. It feels like light construction compared to the GLR drogue I got with my Firestorm 54, but obviously a drogue doesn't have to put up with much and I'm no expert on chutes. I'm more concerned about extra strain on the main or body tube when it opens due to the fast descent.
 

Binder Design

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"very flimsy" was a poor choice of words, I more meant to say "inadequate".

No worries. That exact drogue has been used on all of our DD kits for many thousands of flights. It is well proven. That being said, if our competitors are offering a superior product at a more competitive price, we will reevaluate ours and set the price point accordingly.

I personally fly these DD kits drougueless, so I know by experience that they won't zipper when the main deploys.

Thank you for your input.
 
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AlnessW

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The main chute is 40" and looks very sturdy, I was rather surprised by the 12" drogue which feels very flimsy
You don't NEED a drogue - just saying...

The Excel is a fabulous kit and a great way to move up into 54mm motors - the stock kit will handle anything from a baby H to a K. Got my L2 with this bird, as well! I finally shredded mine when I flew it on a K375NW, the Warp-9 boost was just too much for the aged airframe...

Good luck on the build, and hopefully see you at an AeroPAC launch this year.
 

woferry

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Well, I didn't get much done during the week, I spent most of it rebuilding my Eggfinder LCD into a new enclosure, with switches and buttons to make it easier to use (and prepare it for the TRS I'm anxiously awaiting from Cris ;)). My Aero Pack retainers arrived Friday, so I can finally get started on the motor mount.

I did try the "CA soak" trick (my first time), first testing on one of the avionics bay coupler tubes. I wound up doing one end of each coupler, both ends of the upper body tube, and the top of the lower body tube. Used probably 2/3 of a 1oz bottle of flexible thin "Insta-Flex" CA from a local RC hobby shop. After hearing some comments about the CA possibly making parts more brittle, I figured the flexible stuff might be a better choice. No idea if this actually does any good or not but I figured I'd try it out. It did add about 0.05 oz to each end I soaked, going about 3" in and also adding a bit at the very edge / outer face. For the top of the upper tube the build-up was helpful in getting the NC to fit better (I still have 2 wraps of masking tape around each rib and it's still a bit loose, I'll use push-pin rivets to hold these pieces together in the end. For the other pieces I will have to do a bit of sanding to restore the fit of the avionics bay couplers to each body tube.

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I also figured out how much of the motor mount to put past the aft thrust plate to accommodate the Aero Pack retainer (my answer: 0.6") and initially lightly tacked (3 points) the thrust plate to the MMT using some of the CA from above while seating the MMT inside the body tube to ensure a flush seat, then removed from the MMT from the body tube and applied enough JB Weld to squeeze out the bottom and then forming a fillet with my finger.

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I then did the beveling on the fins as suggested in the instructions. To do the bulk of the cutting I used my rotary tool with a routing jig and a 1/8" round bit, coming at the fin from both sides. In my initial dry-fit I found that part of the root extends outside of the rocket, presumably because it's the same fins for the 38mm or 54mm MMT. So I marked each fin 0.9" from the end to ensure I routed far enough. After the routing I sanded to make the edges a bit more even & smooth. The slots in the lower tube were also a bit rough, so they needed some sanding. Once the JB Weld cures I should be able to get started with the rest of the fin-can.

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And finally, on the avionics bay I epoxied the inner and outer coupler bulkplates together (top and bottom, using 5-minute Z-poxy), installed the eye-bolts with threadlock, and threadlock'ed the nuts on the top-side of the bay (the bottom-side uses wingnuts so those won't get locked), and also epoxied on the switch band using the same epoxy.

I also staked out my local Orchard Supply (right around the corner from my house) as the place to get more advanced hardware like forged eye-bolts, small U-bolts and #6/#8 T-nuts. I will likely replace the lower eye-bolt that goes into the top centering ring with a forged one, more because this has a longer shaft and I have a plan that would require that (more on that when I get there). They also had some hardware that I think I can use to mount my sled to the 1/4"-20 all-thread provided for the avionics bay. I also got my parts from Dog House this week, namely the charge wells with built-in terminals and some wiring harnesses. This bay is huge compared to the one I had in my Firestorm 54, so I figure I will set it up for redundant altimeters, most likely with a StratoLogger CF that I just received and an EasyMini that I'm about to order.

So the fin-can and avionics bay sled are the main items remaining in the build, though I'm also planning on modifying the nose cone to support an Eggfinder, but for that I'm waiting on parts from Performance Hobbies that will hopefully ship this week.

What was typed above I meant to post on late Saturday / early Sunday. What follows is what I did Sunday.

I installed the Dog House (1.5g) charge wells on each avionics bay bulkhead, as well as a 2-pin terminal to connect a backup e-match for each charge well (I'm not planning to duplicate the charges, at least not yet). With the double-thick bulkplates I wasn't comfortable with the #4-40 1" screws included with the charge wells (there's barely enough left for the lock washer and two sets of nuts & washers recommended for the stack), so I picked up some 1 1/2" screws at Orchard that leave me with plenty of extra thread. I still need to drill a hole on each end plate to feed the wire through to the terminal block, it's too bad that there isn't a terminal block that works like the charge well does, using mounting screws to provide the electrical connection. I haven't wired these yet as I realized what I'd like to do isn't covered by what I ordered from Dog House now that I really think it through, so it looks like I'll be placing another order for more wiring (what I have is great, I just need more, and plan to see if Bill will do something slightly custom for me, assuming he builds what he ships).

I also cut the avionics bay sled from a piece of wood I bought for a different project but didn't need, and started to epoxy the sleeves for the sled, but there is more to be done here. I found nylon sleeves with a 0.257" center opening for the 1/4"-20 all-thread at Orchard, but they're 1/2" OD so they're pretty large. But they're a third of the weight of the stainless steel spacers I found originally so I went with them instead. But you have to build up quite a bit of epoxy to attach these suckers. I have milled fiber shipping right now, I may try adding this to thicken up the epoxy before doing more.

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I'm blocked on my next step for the fin-can waiting for the replacement rail buttons I've ordered, hoping those will show during the week. I'm debating putting the sanding sealer on the fins now while I wait, I'll avoid painting the fin tab area to not affect the epoxy there, but it seems easier to do it now rather than masking the rest of the rocket to apply it later. I'll also hit the thrust plate while I'm at it.
 

woferry

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Haven't touched the e-bay sled yet, have been busy working on the fin-can. First tacked the extra upper CR on at the top of the extended MMT as well as the lower CR onto the thrust plate (30m Z-poxy), the middle CR still floating. As both the upper and lower CR have 'thickening plates' added on one side to shore up the U-bolt and rail button attach points, I drew a line on both plates to ensure proper alignment. I then loaded the MMT into the body tube to do the fin attach.

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Last week during the week I built my fin alignment jig based on this thread from some 2x6 redwood, 1/4"-20 all-thread, washers, wing nuts and some deck screws for the legs. The mods in my version are that I don't have separate strapping points for elastic/whatnot, I just use the exposed all-thread and wing nuts on both sides and loop ball bungies over the all-thread ends (the nut wings help to hold them in place for larger tubes). I also cut the angles in the 2x6 at 30° not 45°, the shallower angle lets it accommodate somewhat larger tubes as they can make tangential contact farther inward. The very edges aren't as clean so I certainly want to stay away from those, I could obviously add another pair of spacers (the bottom one being long enough to support the fin) to deal with even thicker tubes, right now I think it can handle the 5.5" LOC rocket I have on order without spacers (if my math was right), it certainly works great for this 4" Binder tube. Since there are holes along two lines (to help avoid rocking of the two large pieces of wood) I can use the closer ones for larger tubes or the ones set back for smaller tubes. Ensuring that the center spacer (1/4" for me right now to match the thickness of the Excel DD fins) doesn't go all the way to the short face of the 2x6 creates a small gap that the top of the fin can slide into to help support the body vertically (I'm using this to support the fin-can for fillet epoxying right now). Only downside I've run into is that I should have made the legs longer, the Binder fin length is a bit longer than my overall jig height, so the fin hits the table if one has to point straight down. For a 3-fin design this isn't a big deal, it would be for 4-fin obviously.

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So to do the fin attach I did a few tricks. After inserting the MMT, I cut 3 lengths of wax paper the length of the slots, and fed each sheet into one slot and out of the next, and blue-taped them to the outside of the tube. This served two purposes: first it made the fins much easier to install (no snagging against the tube walls), and second it provided a surface that if any epoxy stuck to while trying to get it inside the slot I could easily slide/remove the wax paper to move the stray epoxy away from the fin before installing it. For each fin I mixed up a small batch of 5m Z-poxy, and scooped it through the slot directly onto the MMT (slot facing up obviously) using my coffee-stirrer mixing stick. Because in every case some epoxy came in contact with the wax paper, after it was all scooped in I loosened the blue tape and slid the wax paper such that the glue would move away from the slot edge (first time I would feed it inside the tube a half-inch or so, then when doing the next slot I'd remove that piece of wax paper entirely). And after this (but obviously before the epoxy set) I slid the fin into the slot, rotated the tube to support the fin against the jig, clamped the fin and let things set for at least an hour before moving onto the next fin. The instructions said to apply the epoxy to the root of the fin and then slide it in, I didn't see how I could possibly do this without getting epoxy all over the tube slot edges (and at that point it would smear up the fin sides with no way to remove that), so my way of applying it directly to the MMT and being able to slide-away any epoxy that accidentally hit the slot edges seemed much cleaner to me, and I had the wax paper in my kitchen anyhow. I also used some of the wax paper between the body tube and ball bungies, to make it a bit easier to rotate the tube without snagging on the bungies (it would rotate pretty freely, but then the bungies would want to rotate the tube slightly away from the final position, tending to lift the fin off the flat surface of the jig).

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One issue I ran into was with the clamping of the fins to the jig. I used two pretty strong clamps and after removing them from the first fin to do the second one, I noticed that it made two very noticeable dents in the fin. So before doing the other two I folded up some paper towel to act as padding, this led to a single, less pronounced dent on the second fin, and with more paper towels no dent at all on the third. So that's certainly an "oops" that I'll have to try to fill in before finishing the fins now. :p

Once the 3 fins are set, you take a hobby knife and cut away the 3 small sections of tube just below the slots that I guess was left in for structure (they're flimsy enough that it doesn't make it easy to slide the CR's in and out, so they got pretty chewed-up as I was prepping the rocket), which then makes it possible to slide the entire fin-can out of the rocket. This provides easy access to the MMT and fins to do your proper epoxy fillets. I used a pen to write a number on each piece before I cut it, I may attempt to glue them back in when I'm done. I also numbered each fin and put the number above each slot to keep track of things. I received some 1/32" milled glass fiber from Fibre Glast this week, so I mixed that in with 30m Z-poxy and have poured the inside fillet on 4.5 of the 6 fin faces as of this morning. The 0.5 was a complete disaster that I mentioned on this thread, I'll try to attack that tomorrow. I'm using my fin alignment jig standing on its end to position the fin-can while applying these fillets, the self-leveling of the epoxy is great. I suspect I probably overdid it on the epoxy, each fillet is around 3/4 oz of epoxy and fiber (by weight it's roughly 75%/25%, I mixed in roughly 1 tsp of fiber with each mix of epoxy for one fillet). I weighed the fin-can at 17oz before starting this, will have to see what the final weight comes in at.

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So next up is trying to remove that botched 5-minute fillet (last picture above) and finishing those final two inside fillets, plus two more CR surfaces to epoxy (bottom of the upper CR, top of the middle CR). I still need to drill the holes for the nuts that will secure the rail buttons into the 'thickening plates' I added, but I'm waiting on the rail buttons right now (hope to have them Monday or Tuesday of next week), then I can epoxy the fin-can into the rocket. Then finishing the attach of my e-bay sled sleeves, and early next week I should have a custom wiring harness Bill at Dog House made for me (I can't wait to see it!!) to connect two altimeters to the top and bottom charge wells using a connector/pinout I'm planning to standardize my rockets (and altimeters) on. Then it should be on to painting. I also have the nomex chute protectors on order as well as Kevlar shock cord from OneBadHawk so I can finish the recovery bits.

On paint, since I plan to use the Dupli-Color Effex in the end, I figured I'd try using all Dupli-Color paints. So I hit my local AutoZone and picked up two cans of grey filler primer, two cans of glossy black, a can of "victory red" and the two cans of Effex they had. I grabbed one of the tubes an AT DMS motor came in from my last launch and have been doing some paint trials with it. I primed it using filler primer which worked very well, applied two coats of the black which looked pretty good I think, and then tried some masking and applying the red, both over the black and over a section that was primed but not painted black. I can't tell the difference in the red, so that's good that it seems I can paint in either order where the two will be painted on the same part (only around the fins on the body tube), but the masking didn't go very well. I tried a trick suggested here of applying one more coat of the black after taping (to avoid the new color bleeding under the tape), then waited the normal time between coats (10 min recommended on the can) and started painting the red. This clearly wasn't a good idea, some of the black mixed into the first coat of red (two more coats covered this however), and after 3 coats of red, waiting 30 minutes and peeling back the masking tape, in some cases the red AND all 3 coats of the black peeled back, exposing the grey primer again. Also, a triangle point I tried making in the red peeled off with the tape (again just showing the primer underneath, this point wasn't over black). The red seems to go on almost more as a "skin" then really soaking in, not sure if it's because i've wound up with too many coats overall, or not waiting long enough before pulling the tape (or waiting too long??). I do need to do some more experimentation before I do the real paint job obviously. But right now I want to put the Effex over what I've done so far and see how it looks. I probably want to find a darker red than this also, I was trying to avoid metallic paints and there wasn't much non-metalic red at my local AutoZone. I may also try Rustoleum paint and the Effex over it instead. It's T-2 weeks until I'm hoping to fly this rocket, so time is running short on the painting. I guess it may make it's first flight in primer-only, we'll have to see.
 
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AlnessW

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Go easy on the internal fillets - no need to add excess weight.
 

Handeman

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Hav As both the upper and lower CR have 'thickening plates' added on one side to shore up the U-bolt and rail button attach points, I drew a line on both plates to ensure proper alignment. I then loaded the MMT into the body tube to do the fin attach.

View attachment 252727

The one thing that has bitten me and you might want to look into it, how much space will you have between the BT wall and the U-bolt? You may not have enough to be able to use a quick link. You may have to loop and tie your shock cord to the u-bolt.

I've found it's usually better to angle the u-bolt on the CR. One leg near the MMT and one near the BT. That gives you more clearance for a quick link.
 

AlnessW

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Why lengthen the motor mount tube at all? I am running 16 inch motors in a 10 inch tube on my favorite 38mm bird. Sounds awesome overall, though!
People on here are "scared" by the short Binder Design motor tubes for some reason. My Excel came with the standard 8" x 54mm tube which has housed a 22" long motor case before. If the rocket was still intact, I'd fly a 30" long case in it without sweating...
Mike once told me that "all the motor tube does is center the motor inside the rocket, and provide a place for the fins to attach to."
 

woferry

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The one thing that has bitten me and you might want to look into it, how much space will you have between the BT wall and the U-bolt? You may not have enough to be able to use a quick link. You may have to loop and tie your shock cord to the u-bolt.

I've found it's usually better to angle the u-bolt on the CR. One leg near the MMT and one near the BT. That gives you more clearance for a quick link.

The quick-link I have fits, with the fin-can installed in the body I've been able to reach in from the top and install and remove the quick-link. That's the main nice thing about extending the MMT I think, I can just barely reach it where it is now, but well enough that I can still turn the lock nut on the quick-link easily. If it was another ~8" down there's absolutely no way I'd be able to reach it.

I had initially considered a larger U-bolt that would have given more clearance because the nuts would have started to reach around the MMT and it would have moved the U away from the side-wall, but then I'd be in danger of not being able to use a motor that extended past the mount because it might crash with the U-bolt or quick-link. Where I have it is centered between the wall and mount and the quick-link doesn't crash with either. But thanks for the comment, I had thought about that when selecting my hardware.
 

woferry

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Okay, been a few weeks since I posted, frankly there isn't a lot to do with building this kit, but it's been a slow trickle with work mostly done on weekends, plus a small task here and there on random weeknights. And I hadn't taken the time to post anything here, I'm planning the maiden flight for this rocket this weekend, so I wanted to try to get caught-up before then. I'm going to split this up across a few posts for ease of attaching the pictures.

I was able to chisel-out the bad (5 minute epoxy) fillet successfully (without loosening the fin since it was epoxied on the opposite side before I started). I was afraid in doing so that I had weakened the MMT a bit (it appeared dented looking from the inside), so I borrowed a 54/1280 casing, wrapped it in wax paper in the right area to both thicken it up a bit and ensure nothing stuck to the case itself, and had it inside the mount while doing the (proper 30 min) epoxy for this final fillet. So no issue installing either this case or my 54-38 adapter.

Did the final fillets on the centering rings, installing the rail buttons, and the fin-can installation into the tube. That was the worst feeling for me, everything up to that point felt like there was still an option for recovery, but the finality of gluing the fin-can into the body certainly felt like the point of no return for me. :) Since there were 3 rings I tried to ensure each one had some attachment (with the least emphasis on the middle ring), there was enough distance between the top and middle rings that I could apply epoxy to the right spot inside the tube (using a dowel I had marked for the appropriate distances) for the upper ring, slide the fin can in far enough that the upper CR was above the fin slots but I could still tilt the can to apply epoxy inside just above the fin slots, then epoxy the very bottom of the fin can and slide it in once and for all. I didn't get a full fillet on the top CR (in hindsight I should have done the middle CR application first, to give the upper CR epoxy a bit less time to drift), so I went back and added some more epoxy after the first round had set to fill in the gaps.

On the rail buttons, I wound up using the Apogee Standard Rail Button. My original plan and why I had added extra wood below the top CR and above the bottom CR was to make an area of wood to house the T-nuts, so the nuts would actually be a part of the fin-can that simply lined-up with holes in the tube. So the shaft of the nut would have gone into the wood, not stuck out of the rocket. But I couldn't find buttons that were designed to work this way. The Apogee ones have the button part drilled wider than the screw, so it's expected that the nut shaft fits between the two parts to take up the extra space. So I wound up making a slight bend in the two nuts to roughly match the curve of the body tube and installed them where I had intended, so they're backed-up by the extra wood, but only connected to it via epoxy when I installed the fin-can. But all this means the buttons can be replaced, it just didn't work out the way I had originally hoped (that's what you get for making plans before you actually have parts that work the way you want).

Next up was the exterior fin fillets. I used a technique often mentioned here (with helpful pointers to other sites such as this one), using a small piece of 3/4" PVC pipe I had left-over from building my rocket stand. I turned my fin jig on its side so that its "V" faced upwards to support the rocket while doing all of these fillets, since it results in one fin pointing straight down so the other two make a nice "V" for the fillets (same as when doing the internal fin fillets earlier). First I applied a generous coat of red sharpie near one end of the pipe and dragged it along each fillet area to mark where the pipe makes contact with the body and fin, and masked along these lines. Then I mixed my 30 minute Z-poxy with added microbubbles and poured each fillet, shaping it with the PVC pipe after it was thoroughly washed in isopropyl. I was very satisfied with the outcome, especially considering that it was my first attempt at this. Shaping around the top and bottom was certainly the hardest part of all of this, especially when doing the second surface of each fin where the opposite surface was already cured. But where this proved tricky I chose to build it up just a bit, so that I could sand it away later on. So I took a shot of one set right after I had shaped it (quickly removing the masking afterwards to contain the epoxy that squeezed out onto it), as well as each fin afterwards. I wound up using a bit of the excess after each fillet to apply along the bottom of the rocket where the thrust plate meets the body tube (obvious in the last picture), though most of this will get sanded away in the end so it was probably pointless.

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woferry

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For recovery I have all of my quick-links, and purchased a pair of 25' 2-loop 7/16" kevlar harnesses from OneBadHawk. These things are indeed quite nice, they do weigh-in a bit over 6 oz each which is roughly 3x the stock cord weight. I added the chute attachment loops using a simple knot I thought was suggested in GLR's instructions but I can't find it now. Each harness needed one, the drogue normally does since you don't want to attach the chute at either end of the harness, but in this design the main does as well, where while the main often gets attached at the nose cone end of the shock cord, this rocket's design assumes the NC does not separate from the upper tube (the tube separates at the avionics bay instead), so you need to position the main chute far enough away from the NC on the shock cord to ensure the parachute gets pulled out of the tube by the cord. I avoided a quick-link at the NC as I didn't like the smaller contact point it would provide between the plastic 'loop' on the NC, especially given the extra weight of my NC with a tracking bay installed, so I simply looped the kevlar through itself for this upper attachment to provide a softer, larger surface-area against the plastic. Everything else (parachutes, avionics bay and booster attachment) are all metal-on-metal bolts (U or eye) to quick-links. I used 3/16" (616#) quick-links at the ends (largely because the smaller links didn't open wide enough to fit over Binder's eye-bolts, and smaller ones (can't find the package right now to note the size/strength) for the parachute attachment points. For the main I have a Sunward 18" protector I got from Apogee, and on the much smaller drogue I re-used a GLR protector from my Firestorm 54 that I no longer need there since it isn't DD anymore.

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I guess I hadn't talked about the NC up to now. Since I have Eggfinders, I obviously want to fly one in this rocket. Since this is DD it shouldn't be able to get too far away, but it's piece of mind at this point, I've had cases with my Firestorm 54 where I thought I could see exactly where it landed in a field, yet when I got there I couldn't find it, but the Eggfinder took me to where I could see it. So what I decided to do here is get some BT-55 body tubes (I'll be using the others in my next build), and cut an offset hole in the base of the NC to avoid damaging its plastic loop (so I wouldn't have to do anything special for the upper shock cord attachment). I happened to already have a hole-saw bit (the kind with the center drill-bit shaft that bolts onto different sized drill 'cups') that is some un-marked size between 1 1/4" and 1 1/2" that was perfectly-sized for BT-55, and this also fit quite well on the plastic face of the NC. So the full 18" piece of BT-55 fits into the NC and runs from being centered at the top to offset at the bottom, yet doesn't crash with the 4" body tube when the NC is installed. I poured-in 30 minute epoxy with microbubbles to lighten it until it was above the level the BT-55 would sit at the top of the NC, then fed in the BT-55 and epoxied it at the other end. I didn't have any of the small brass rods suggested to ensure the epoxy is well-attached to the top of the NC, but I did drill 4 holes and blue-taped them on the outside before pouring the epoxy, so the epoxy poured into these holes and it seems to me that this will do a fine job of keeping it in place, besides the fact that any load also transfers onto the BT which is epoxied at the other end as well. But anyway, this BT-55 tube happens to work perfectly for a sled I had already devised (using a free Home Depot paint mixing stick) to hold my Eggfinder and battery, that also inserts into the NC of my Firestorm 54. I had epoxied a plastic wing nut (1/4-20) to the end of this 'sled', which secures the sled in the other rocket's NC by threading onto the exposed end of the eye-bolt that goes through the NC base (first picture below). In that rocket I zip-tie the battery to the sled, here it makes things too big to slide into the BT-55, but it's a snug enough fit that the battery won't have anywhere to go. For this rocket, I'll thread on another eye-bolt through a BT-55 bulkplate to both help seal (though not perfectly) the tube from ejection gasses (it's as far from the charge canister as it can be, so I think it's adequate protection) and also hold the sled in place, so it doesn't either slide too far up the tube and risk damaging the Eggfinder's antenna, or fall out of the NC. Or at least I hope, I have seen other rocketeer's similar designs snap the zip ties or tear through the tubes from launch or ejection forces, so I used a re-usable tie that I think will be less likely to slip and certainly have less sharp edges, and have reinforced the BT holes with CA. Some of the failing instances I saw were also zip tie against PCB, here it's against an eye-bolt so I hope that will also help.

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woferry

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So by this point, the nose cone is done as is the booster section. The only thing left was sorting out the avionics bay. The bulkplates were done long ago except for wiring, but the inside sled still needed some work. I will re-visit this later to see if I can make it more modular once I have another rocket I could actually trade the electronics with. But I have a StratoLogger CF that I intend to be the primary, and holes drilled so that I can either use my old StratoLogger SL100 as the backup or else an EasyMini I have on order that will hopefully arrive this week. I standardized on a specific connector and pinout (using Dog House Rocketry harnesses) for all of my altimeter connections (as well as a JST connector for all of my power connections, including the in & out terminals on Featherweight Magnetic Switches). And I have to give special kudos to Bill at Dog House, I asked if he could make a custom harness to map my altimeter connectors to connectors for the bulkplates, and he not only did so but even provided a drawing that I could use to verify what he was going to make and keep to make future harnesses for future rockets, and made sure we were in agreement on terminology w.r.t. connector genders. Unfortunately, while I had the electrical details all sorted-out (I am an EE after all), I hadn't considered one aspect of the mechanical details properly. So Bill made exactly what I asked for, and I had to go back and ask for 2 pairs of the wires to be re-made longer so that I could actually make the connections work. :p But Bill quickly made and shipped the longer wires, so that I could pop the short wires out of the plastic connector housings and replace them with the longer wires.

My goal was to have two 4-pin connectors in the middle of the sled, one to connect to the 'primary' altimeter using my 'standard' altimeter pinout & wire colors, the other to connect to the 'backup' altimeter using a different set of colors but the same drogue/main pinout. This harness then cross-wires the cables such that the primary and backup drogue connections run to a 4-pin connector at the lower end of the sled, and the primary and backup main connections run to a 4-pin connector at the upper end of the sled. These connectors also use a common pinout (primary on pins 1-2, backup on pins 3-4) and colors matching those of the harness. The bulkplate connectors are the same gender as the altimeter connectors, so you can't make a direct connection and mis-wire things, the harness makes the necessary gender conversion. So the primary at each end gets wired to the charge well terminals, the secondary goes to a screw terminal to connect a second ignitor. At least for now I've decided to double on the matches but NOT the black powder, I have extra charge wells with terminals so I can change my mind on that later. My mechanical issue is that I started out with all 4 pairs of wires in the cross-wired harness the same (very short, I told Bill to make them as short as he was comfortable making them), and while that works fine for the upper bulkplate since it is permanently attached (well, thread-locked) to the sled, but I didn't consider that once you slide the assembly into the avionics bay couplers you can't reach in to connect the lower bulkplate's harness. So now the lower bulkplate connector wires are longer so that it can reach beyond the bottom of the tube with the sled inside, so you just mate the lower connection and screw in the drogue plate and everything is ready to go.

Next up was taking care of the remote arming. When my Firestorm 54 still had an avionics bay (oops), I had used a Featherweight Magnetic Switch for the activation, and really liked it. So I picked up two more for this rocket, and they're installed on either side of the sled (the nuts they screw into are epoxied to the sled, but not the boards themselves). This places them right next to the vent band walls. When I drilled the ventilation holes for the bay in the switch band, I intentionally offset two of these holes slightly so that they would line up better with the LEDs on the switches, so that I could get visual confirmation of whether the power is on or off. These switches work pretty well, but I do find that occasionally when passing the magnet by they either don't register (probably moved the magnet past too quickly), or toggle twice such that things end up in the same state as before, so I prefer to be able to check the light as well (the altimeter beeping makes it obvious when turning on, but less obvious when turning off if it doesn't keep beeping). So that covers the charge wiring and powering of the electronics.

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Unfortunately, I have yet to do a successful ground test. :( I have a total of 83 MJG Firewire Initiators, 3 that I bought back in September at XPRS through Bay Area Rocketry, and a box of 80 that I ordered direct from electricmatch.com and received mid-January. I've tried to set off 1 of the former and 2 of the latter, and have only proceeded to change the lead continuity from ~1Ω to infinite, without ever getting any fire or even smoke. I mentioned some of this on this thread, since then I tested the third one (from the September set, figuring it had to be a different batch than the ones I got in the mail in January) using my SLCF (and a vacuum cleaner against a single un-taped vent hole to do the deployment test since I don't think there's any other way to do a ground test with a StratoLogger), and it had the same result as when I connected the initiator leads directly to my 2s LiPo, it just blew the connection open without actually igniting. So I'm starting to doubt that it was just a bad batch, either the 2s battery is just too much for these things or there are issues with these ignitors. I've emailed the seller, waiting for a response.

So while I plan to fly this rocket for the first time this weekend at the TCC launch, I'll likely be doing single deployment (motor eject) since I have absolutely no confidence that any of my altimeters can actually ignite BP using these Firewire Initiators. :( I guess that will let me test out a friction-fit of the upper section, I'll stuff the drogue in there and see if I can land with it still in place. I had done this with the first flight of my Firestorm 54 and it landed with both chutes deployed, but it also deployed at high speed due to insufficient ventilation of the body tube, so it wasn't a 'proper' BP ejection. I had initially figured I'd use shear pins on this rocket, but I've seen enough discussion here lately about friction fit being fine for a 4"/non-FG rocket that I figure I'll try it out before poking more holes in things. :)

I do still want to attach a Mobius ActionCam shroud (one of landru13's nifty 3D-printed ones) to this rocket. To start I think I'm going to attach the shroud to the vent band (clear of the vent holes obviously), first off in this area I can screw it in without risk of snagging on any recovery bits (there's more to bite on with the vent band + coupler also), and I prefer the idea that during drogue descent it will be pointing up at the drogue but will shift to pointing down when the main deploys, some DD videos I've seen it can be hard to tell just when the main really fired. But since I'll only be screwing it in I can obviously fill those holes and epoxy it to the lower body tube instead if that proves to be the better way to do it (i.e. to never be looking up).


So the rocket is out in the garage with its first tip-to-tail sanding done, ready for priming now. I'm hoping that Rustoleum filler primer alone will let me address in any minor imperfections around the fillets and tube spirals, but I'll have to see. If it takes more I probably won't get to that until after the first launch.

And I still haven't come up with a name for this rocket. :p
 

B787_300

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where did you get the terminal blocks from? i tried finding them at Home Depot while I was getting paint but all they had were some GAINT ones
 

woferry

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where did you get the terminal blocks from? i tried finding them at Home Depot while I was getting paint but all they had were some GAINT ones

I bought these from Dog House Rocketry. AdaFruit also sells them (well, the 4-position one at least), though without the bolt and hex-wrench to attach it to the bulkplate (I guess you could epoxy it instead). I had ordered one from there earlier for a non-rocket project.

So I got the rocket primed with ~3 coats of filler primer this past week, and flew it on an I280DM (motor eject drilled to 10s, main in the lower bay and the drogue stuffed in the upper with extra tape for a friction-fit) Saturday at the TCC launch. Went to 2256' and was recovered successfully (and the upper bay remained closed, though it did slide out partly). My next intended flight was to put a J350W in it and do my L2 cert flight, but while the rocket proved itself ready to take the test I didn't (hadn't studied since October and didn't get the time before Saturday since I was finishing the rocket and loading up my truck for the drive, and got 44/50). So I'll likely go back to the March TCC launch assuming it happens. With any luck it will be fully-painted by then, or at least the right color but maybe not the Effex coat yet.

And so far the best name I've come up with is "dd.xls". :p

I'm still finishing my album and videos from this weekend's flight, so I'll make another post later this week, the link in my signature hasn't been updated yet (or my signature for my first N-sec flown this year).

Oh, BTW, saw your picture on the daily thread, B787_300. Looks great!!
 
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neond7

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Great build, I love the Binder Design kits! Got a bunch, and have my eye on one or two more.
I just built my second Excel kit, my first one (54mm) has been flying for years. I am involved in a contest and built a 38mm one as the contest required using a 38mm CTI I242 motor.
On both kits I used the longer MMT's, both were 16" I believe with a third centering ring. This mod was simply done to make reaching the eyebolt on the top centering ring an easy task.
I also used the .1010 rail buttons from apogee - with the rear metal backing plate, it's very secure.
One suggestion, the internal fillets were pretty massive - I use Aeropoxy structural epoxy from giant leap for internal bonding and you don't need to use much and it's the strongest stuff available. I have found hobby epoxy to be brittle.
Post some pictures of your final painted rocket - would love to see it!!
ImageUploadedByRocketry Forum1425667554.454684.jpg
 

Binder Design

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Once the 3 fins are set, you take a hobby knife and cut away the 3 small sections of tube just below the slots that I guess was left in for structure

Correct. If the tube was slotted all the way to the end, it would get destroyed in shipping. It also helps keep tension on the fin while you tack it in.

Regarding everybody requesting the long motor tube and extra ring...
Here's a trick for those people who believe they can't replace the recovery harness if they can't reach the eye-bolt. Find a cardboard tube that when slid over the narrow end of a carabiner will open it up. Tie your harness to it. Slip the harness through the tube then onto the carabiner. Put the whole works down into your airframe and hook the end on the eye-bolt. Then pull the tube off the carabiner. Removal is the reverse procedure.
 

jeff2space

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Regarding everybody requesting the long motor tube and extra ring...
Here's a trick for those people who believe they can't replace the recovery harness if they can't reach the eye-bolt. Find a cardboard tube that when slid over the narrow end of a carabiner will open it up. Tie your harness to it. Slip the harness through the tube then onto the carabiner. Put the whole works down into your airframe and hook the end on the eye-bolt. Then pull the tube off the carabiner. Removal is the reverse procedure.

Great trick!
 

woferry

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Great build, I love the Binder Design kits! Got a bunch, and have my eye on one or two more.
One suggestion, the internal fillets were pretty massive

Yeah, I did go a little crazy there. :) My dad definitely used less on his non-DD Excel started after mine.

Post some pictures of your final painted rocket - would love to see it!!

So far it's still primer-only unfortunately, there is a picture on the rocket's EMRR page (I should take some better shots at the house). I went through 4 cans of rusto filler primer to get it the way it is now, and half of my garage has a grey-ish tint to it now. :p I had started to construct a paint booth, but didn't have it ready before that first flight and wanted it to at least be primed for that flight. But I'm not doing any more painting until I can do it inside the booth. I think I have the rest of what I need now to finish the booth, I just haven't actually put it together yet. So once I do that (perhaps Sunday) and verify that the blower I bought can move enough air to be comfortable using it, I'll at least move from grey to black. My previous paint trial certainly proved that I was rushing things, so I'll probably let each color sit at least a week before moving onto the next. So there's a launch tomorrow, and I'm hoping to go to one on 3/21, then I may not have another one until mid-May. So it will be grey tomorrow, hopefully all-black by 3/21, and then ideally it's final color plan (added red + Effex) by May.


I am curious though, I put together the most accurate OR model for the rocket in its current configuration as I could (attached), including the 5438 adapter (modeled separately so that I can easily move it between rockets) and an offset for the motor (so far I found one motor that was ~3oz heavier than the ThrustCurve model, and another that was ~3oz lighter, I really wish there was an option for a negative weight Mass Component, I had to deduct weight from another component to get the right rocket weight with that motor). But with a weight and Cg in OR that exactly matched what I got when I measured both, OR predicted 1865' and the StratoLoggers reported 2256/2258'. So that was a pretty significant delta, I don't see that with my other rocket, I had found OR to get pretty close to what I get out of the flight recorder (an AltimeterTwo, specifically). So that's only one flight so far (I280DM) and I didn't fly the A2 so it's a different opinion, an A2 and my A3 will go in the next flights. But I'll be interested in seeing how well the next flights correlate to the OR sims for the motors (next flight is an I297SK, this time I had to adjust the weight up because it's a Pro38-5G reload in a 6GXL case w/spacers). OR does complain about the Mobius shroud which is modeled as a thick fin, but I have the same shroud on the other rocket (and get the same sim complaint) yet it seems more accurate there.

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woferry

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Unfortunately, this particular rocket will never be painted, as it no longer looks anything like a rocket. :p

The first flight on an I280DM-10 (2/21 @ TCC) went flawlessly, as did the second on a I297SK-10 (3/7 @ Snow Ranch), both set for motor eject single deploy. Saturday at TCC's 3/21 launch I took the L2 exam and passed, so I loaded it up with the J350W-M I had built a month ago (everything but the BP). I loaded the BP and capped the well, flew an A2 and A3 (that I had just purchased as my previous units were lost during my first flight of the day with my other rocket, which now has a 2.5" zipper to deal with in addition to losing the altimeters that were zip-tied to the upper eye bolt) as well as a SLCF, EasyMini, Eggfinder and a Mobius ActionCam. The L2 cert flight was uneventful, as in there was no event. :facepalm:

It took over 90 minutes to find it in the field, the Eggtimer TRS last reported GPS position was way past where the rocket actually crashed. I started out looking past that position in case the GPS lost lock during descent, but after failing to find it there I started working back closer to the launch pad and found the red chute protector among the alfalfa field. The nosecone was crumpled and buried in the dirt, took a shovel to remove it (many thanks to Mike @ BAR and his friend Marcus for still being on the field and having a shovel). The upper airframe and avionics bay and part of the lower airframe were crumpled to about 5 inches tall, the lower airframe split and broke at the lower U-bolt and was about 10 feet away (most of the lower shock cord was still in the crumpled upper section. The A3854 adapter had separated at the end and the Aero Pack retainer tore the outer cardboard layer off the motor mount. It appears the 38/720 motor casing is intact, the cap which was still on top of the charge well was split (though the white disk underneath was intact) so I guess that and the retainer separating from the MMT absorbed most of the shock. The fin can still looks perfect from the middle CR to the bottom of the rocket, too bad the rest of the rocket wasn't as over-built. :)

So two final pictures, one of the pieces I recovered, and another after removing all the paper and most of the wood.

P3220015.jpg P3220003.jpg

The Eggfinder in the nosecone split in half and the large components sheared off (the Hope RF module was separate and bare). The upper LiPo had a serious bulge but was intact. The A2 and A3 were zip-tied to the top eye bolt of the avionics bay (in the upper section with the unused drogue), the only piece of the A2 I found was a bit of its bottom-case, the A3 was shattered but all in one place. In the avionics bay one of the two LiPos ruptured, either it burned due to that or the power wires must have shorted and caused overheating, the entire upper half of the bay was scorched. The EasyMini looked fairly intact, the PCB was bent a bit and the speaker had sheared off and one of the top terminals was bent over, but it otherwise looked okay. When I tried connecting the USB to see if I could talk to it the connector fell off the board. I am going to see if I can get any data off the SPI flash. The StratoLogger PCB had split in half and most of the parts had come off. The two Featherweight Magnetic Switches appear intact, though one was singed from the battery event so I'll have to test them out (one was still lit when I tore the bay open a day after the recovery). Unfortunately all of my Dog House wiring harnesses are destroyed, the connectors are all bent & broken, though the charge wells themselves seem to be fine as well as the HW other than the screws. While its shroud was shattered, the Mobius camera looks intact from the outside (only the mini-B connector was bent), but it did not behave properly when I tried connecting it to my computer (top LED lit green but the back red LED did not flash, and it did not enumerate on USB). The SD Card sadly had ejected from the camera, I could not find it on the field. Once I get a small screwdriver tomorrow I'll try opening the unit up to see how badly damaged it is, maybe I can at least salvage some parts from it.

I certainly enjoyed building this rocket (though I'm relieved I hadn't spent too much time painting it yet), and the failure was no fault of the kit, I really don't understand why the J350W charge didn't fire. So I'm likely going to order another one and re-build it, as well as replacing all of the other electronics I lost. If I do I'll reuse this thread for the re-build.

And I'm now 0/2 in getting my L2. :( So I may put my focus on the night launch rocket I planned to build after this one, and stay out of the L2 game for a while. I definitely need to find e-matches that work and start doing electronic eject before I try this again.
 

B787_300

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That totally sucks that your ejection charge did not go off. What brand of ematch are you using and are you sure that you turned everything on before launch? Also why were you using the motor charge at all if you are running with electronics?
 

Tonimus

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What did the delay grain look like? I suspect that the delay may have extinguished itself...
 

bobkrech

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It was a very nice rocket and it's sad that it augured in.

You had 3 independent ways to make an apogee deployment happen, and 2 ways to deploy the main and if I understand it, all 5 failed. That's highly unusual. I wonder if the rocket was too complicated for a Cert rocket?

There was a lot of electronic "stuff" in the rocket. I don't know how you could confirm that your deployment altimeters were functioning properly as almost certainly the 5 rocketry specific items were beeping. Did you have a check list, and if so, did you follow it? With all the beeping, how did you confirm that the e-matches for the deployment altimeters had continuity, and were set up properly, before the rocket was launched. There were several transmitters in the rocket, did you confirm that the transmitters did not interfere with the deployment altimeters?

Bob
 
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