RW Go Devil 38 community build thread

Got the electronics bay nearly done and tested. Just have the static ports, screw holes to drill and tap for 2-56 screws to secure to upper bay and
cut two slots for zip tying the battery. The battery will lay on top of some servo tape and the zip tie will help hold it down. Will put some dense foam on the forward bulkhead and you can see the epoxied legs of the wires to the forward main charge go just over the battery and will help keep it in place. I applied a dollop of solder to hold the wires to the magnetic switch. The nylon screws are "sort of" safety security.

The other three shots are of a converted AT HV Arcas that flies on a 29mm H128. It uses a single all thread
with the 3Dogs Rocketry eyenuts. Only thing I had to do for the conversion was cut two plywood bulkheads
besides the terminals, all-thread and wires. I use a kevlar loop in the eyenut for twisting isolation. Flown 13 times
with no trouble. (Except when H165 used had two fins crack from flutter. Just CA'ed and will just stick to H128's.
Nice flights to ~1400' to demonstrate dual deploy and great for sites with a low waiver.)
Has Featherweight Magnetic switch too for a great "clean" look.:smile:

I tried fitting an Adept 22 and it won't work with this configuration. Too big. One of Boris' Alti Duo SMT looks like its a close fit if one trims some of the leads for the through hole parts on the bottom of the board.

Anyone have a different arrangement for the Go-Devil electronics bay? I'm curious to see other ideas. I've seen a person bandy about using a kevlar cord in place of all-thread but I can't visualize how that would work without banging around the electronics under deployment forces. Kurt

ksaves2 said:

I tried fitting an Adept 22 and it won't work with this configuration.
Anyone have a different arrangement for the Go-Devil electronics bay? I'm curious to see other ideas.

Click to expand...

Adept 22 fits easily with a 9v battery.... if you re-think your plan.
Ditch the center tie rod.Use 2 smaller # 6 rods

This is Adept 22 in 38 bay...no problem.

blackjack2564 said:

Adept 22 fits easily with a 9v battery.... if you re-think your plan.
Ditch the center tie rod.Use 2 smaller # 6 rods

This is Adept 22 in 38 bay...no problem.

Click to expand...

Ahhhhh yes, You use plain nuts as opposed to wingnuts then to retain the bulkheads. I'll keep that in mind. Thanks Kurt

Leetle delay for further testing of ejection charges. Have to get a small 2S lipo so I can stick a remote switch in the ebay to test
the deployment charges. (https://www.eggtimerrocketry.com/page48.php) I should have used Jim's stratagem for the ebay with two 6-32 rods and simple nuts.

There isn't enough room to run wires from the outside to the terminals for testing unless I were to use kynar (superfine) wires.

I like to ground test to get the charge size correct before I fly. I've never had a deployment failure since ground testing. I've had tangles
mind you but no chute has hung in the tube so far.

I also have to get a different chute protector (read that thinner material) and may have to go to a 24" main chute instead of 30".
I couldn't get it to fit in the provided space of the stock upper bay tube. I think if mine were 2 to 3" longer it would be adequate.
I couldn't cut now the size of the nosecone coupler as I needed all the space for the Tele-GPS. That unit and the 750mah 1S cell just fit
perfectly with no room to spare.

Oh, once I get charge sizes, I'll post them for others with all my parameters. Kurt

Still waiting for batteries to arrive to allow for a ground test with a remote switch. Swapped out a chute protector for a different one and was able to cram a 30" Dino chute in there. Gonna hafta graphite the inside of the tube to make it slippery enough to help with the deployment. Using 2-56 nylon screws as shearpins on the N/C. A couple inches longer on the upper bay tube would have helped but ground
testing a "serious" charge will make certain for positive deployment. Will do shearpins for the apogee deployment also.

I discovered on a RS that if I want to opt for the potential for higher altitude, I'll have to "add" weight to the rocket. First time I've ever had that happen. Will be a Mach buster though. Kurt

Using an EggTimer remote switch https://www.eggtimerrocketry.com/page48.php for ground deployment testing. Cut a plywood sled for testing purposes had to get a 180Mah 2S battery small enough to fit in my unconventional setup. Next time I'll use plain #6 all-thread and plain nuts
to utilize all the room in the bay like Jim H. suggested. Picture shows the battery plugged in and the remote switch in standby mode. I wanted to make sure the match didn't pop with power-up...... No problem.

Next up is the test and using .9gms of powder. Bay is 1.533" diameter and 7.125" long not including the space occupied from the ebay and nosecone shoulders. 30" Dino chute. Kurt

ksaves2 said:

Using an EggTimer remote switch https://www.eggtimerrocketry.com/page48.php for ground deployment testing. Cut a plywood sled for testing purposes had to get a 180Mah 2S battery small enough to fit in my unconventional setup. Next time I'll use plain #6 all-thread and plain nuts
to utilize all the room in the bay like Jim H. suggested. Picture shows the battery plugged in and the remote switch in standby mode. I wanted to make sure the match didn't pop with power-up...... No problem.

Next up is the test and using .9gms of powder. Bay is 1.533" diameter and 7.125" long not including the space occupied from the ebay and nosecone shoulders. 30" Dino chute. Kurt

View attachment 266944

Click to expand...

Turned out that even though the packing is very tight, .9gms is too much. 250lbs of force. Going to drop to .6gms of
powder which is 163lbs. Would have been better if I had 3 more inches of length with the upper bay so the pack
didn't need to be so tight.

The remote switch doesn't like having a bunch of wires crammed in the bay. Range was like 10 inches due to the
antenna attenuation with all the metal in the copper wires. Out in the open the switch works from across the yard,
I dressed up in padding and a welder's mask to be that close. No problem but I didn't get the test video since I had
to stand so close. I unfortunately used the plastic snap cap instead of plain wadding and tape. The charge blew out the side of the microcentrifuge tube. I found out the eyebolt in the nosecone is loose so I will permanently epoxy it in place. I don't want the bolt to unscrew and pull out in flight. Bye-bye to the tracker in that regard.
Charge fried the shockcord protector but the cord is O.K. I have to shorten it anyways. Ran out of time testing so I have to try again another time. I have to make sure no power gets to the charge with the switch when it is turned out. So far no problem. Kurt

got mine in today..... can't wait to slap it around with a K1127/J510

Ahhhhh,

My gosh. You might want to mock it up and see how much nose weight you might need with them long motors if necessary. Do the ebay like Jim shows, use a small altimeter like a Qwark
or if you want data a Raven. I put a magnetic switch on my sled for a clean switching solution. A Tele-GPS will fit in the nosecone but my pictures of course show the small buttonhead screws that are out in the breeze. I did mine with a 720 case so am limited to loads that fit that case plus Ex loads I've developed for the AT cases. Kurt

Wont need weight. those long motors are HEAVY and that's good for stability.

I'm hoping to get data...so I need to find something that will deal with nearly 100G.... and a MARSA isn't quite going to fit.

I'm going to friction fit. Mostly doing those two cases, but I may do a 720 or loki 480 at some point.

DizWolf said:

Wont need weight. those long motors are HEAVY and that's good for stability.

I'm hoping to get data...so I need to find something that will deal with nearly 100G.... and a MARSA isn't quite going to fit.

I'm going to friction fit. Mostly doing those two cases, but I may do a 720 or loki 480 at some point.

Click to expand...

I was thinking that with the length, there is going to be quite a bit of moment arm "more forward" but question is, is it enough to compensate for the forwardshift in CP as the rocket goes supersonic? If you've done it before, you know more than me then. :blush:

Raven III would be the recording altimeter to use if you want a pile of data to download.

With friction fit, if you're good at it, but me I'm too paranoid I'd lose the motor. I'll again defer to Jim H. who suggested making a bulkhead with a piece of all-thread epoxied in the middle. One could either secure the bulkhead with epoxy or go ahead and use screws
that hold the bulkhead in place inside the sustainer. You could use an appropriately threaded eyebolt instead of all-thread and kill the shockcord attachment and motor retention issue in one shot. As long as the aft thrust ring on the motor case carries the load on the airframe, the bulkhead with the all-thread or eyebolt thread matched to the forward closure, should have no trouble securely retaining the case. My project is done awaiting final testing of the deployment charges so it's easy to think of improvements if I were to do a "do over". Kurt

I'm just starting it all, and it's my first MD. I'm thinking eyebolt in the forward as a "just in case"

This a great rocket to fly AT DMS motors. No case to loose.

crossfire said:

This a great rocket to fly AT DMS motors. No case to loose.

Click to expand...

Are you doing single deploy then? Or DD with motor backup? If the apogee deployment stuff isn't a tight pack to push out the drogue, a tape
thrust ring may do it. With my luck it would either thrust up the tube and fry off the tail or the apogee charge would blow the motor out and
may or may not get the ebay out of the sustainer. As long as the upper bay is out of the sustainer, all can be well.

I bet everyone has had a modroc or larger, blow out the motor and the chute in the "olden" days. Just meant the rocket landed softer.

Me, I'm chicken and go for positive retention for both "possible" directions of the motor case.:sigh: Kurt :grin:

It can't go up there is a thrust ring built into the DMS motors. Friction fitting motors works very well. People have been doing it for 30 years. It will work fine.

friction fit the motor and use a threaded forward closure with an eye bolt and you're good to go. then you don't have to attach the cord to the body tube at all. both those motors have a thrust ring so no worry about it pushing forward.

O.K., thrust ring on the case. Haven't used up the stash of RMS motors yet so DMS is new to me. Although I have read of some of the posted issues being had.
Kurt

BTW,

Did a formal TeleGPS test with the GoDevil nosecone mounted tracker. Used a Kenwood D72A to monitor the APRS packet that is emanated
along with the Altus Metrum data packet. I put the nosecone mounted tracker on the upper bay in a cardboard box (with a weight) and set it on the table top chimney on my single story home.

Walked away from the house. Of course there are the usual obstructions in a small town and used a Nagoya NA771 antenna on the D72A.

The tracker was upright about 20 feet off the ground. Walked towards town where the elevation actually declines. Spotty reception at 1/2 mile. Held the D72A above my head and was able to get packets. Went up into some high school bleachers that put me at least 30 feet into the air and got good reception at .75 mile away. The elevation was still lower than the tracker position but getting up above the obstructions improved the reception.

I label this as a success considering the test environment. First the nosecone is transparent to the incoming GPS satellites signals.
Secondly, rocket launches are in open fields and given the results with the obstructions in this test, the nosecone is transparent or nearly
transparent to the transmitted 70cm APRS position packet. Kurt

Did main chute deployment test but couldn't video it as I did it after dark. Used an EggTimer rocketry remote switch on a temporary sled. Had to mess around to get the 8 digit code to get it to "stick". Anyhow, space is very tight in the standard main bay and I had to ditch the quick link connection at the nosecone to get everything to fit. I did the test originally with .9 gram 4f and blew the daylights out of the thing. Fried the Dino cord protector. Soooooo.... I switched to a smaller chute, 24" instead of 30", tied the shockcord to the nosecone as opposed to using a quick link, just not enough room otherwise. Dropped the charge down to .63 gram and with two 2-56 nylon screw shearpins got a more civilized deployment when the button was pushed.

I used those plastic microcentrifuge vial holders and I put two sheets of Blue Quest wadding paper wadded over the end of the charge and wrapped the base of the shockcord protector with two sheets serially. That protrected the "protector" and nothing got fried this time. If I ditch both of the quick links on the shockcord might be able to get the 30" chute back in there. Now I need to drill the aft end of the ebay for two 2-56 shearpins and test that to determine the apogee charge from the sustainer.

I have a 38mm MD rocket out of LOC tubes that is going to be using an EggTimer TRS and a cable cutter to get the main unfurled. I've been able to test it with the remote deployment test feature on the TRS and I'll tell you that makes testing a heck of
a lot easier. Kurt

Ok..................

To summarize, Main chute test with 24" chute and two, 2-56 nylon screw shearpins .63 grams 4F.
I may ditch all of the quick-links on the shockcord and try to get the 30" chute back in there. Empty weight
without propellant is close to 2lbs.

Did apogee test last night with .7 grams 4F. Of course a smaller 12" chute that's easier to push out.
Again, I had two 2-56 round head nylon screws for shearpins on the sustainer also. There's 12.125" internal
length of that bay. Main chute bay was 7.125" long. Worked nicely, the pins sheared and the ebay/main chute/nosecone went the length
of the ~13' shockcord with a little jerk on the sustainer body. Should be ok for an 8 to 9k' flight on a J350.

Congrats to Alexis who mashed his to Mach 2.5 on a J1000 to 18k'. Since I'm not going there, I believe I'll be able to get away with
fin fillets using Proline 4500. Will be lucky if it breaks Mach. Interestingly, the sim shows if I want to get more altitude out of it, I have to add MORE to the projected weight. I'll take the little extra speed instead.

Soooooooooo. If anyone is building a GD 38, these numbers might be something to consider as a starting point for your ground deployment tests. I made a temporary sled using a 180mah 7.4V lipo and the EggTimer rocketry remote switch.

https://www.eggtimerrocketry.com/page48.php

Once connected up, I input the code and it fired the ematch from a safe distance away.

The controlling deployment device is a Raven III with a magnetic switch and a 180mah Lipo as shown in the prior photos.
Kurt

crossfire said:

This a great rocket to fly AT DMS motors. No case to loose.

Click to expand...

I have a AT H550 DMS for my maiden flight. That motor kicks ass!

Kurt have you flown yours yet? I'm planning on giving mine a clear coat. I saw some of this colored tube that was clear coated and it shined like ruby.

bill2654 said:

Kurt have you flown yours yet? I'm planning on giving mine a clear coat. I saw some of this colored tube that was clear coated and it shined like ruby.

Click to expand...

MWP 13. I have a LOC tubed clone DD with single apogee ejection with main unfurling with an Archtype cutter controlled with an EggTimer TRS I'm trying to get ready to go too.

Will fly both with J350' ish motors. The Go Devil is ready to go. Oh, Mayhem Rocketry rail guides so no buttons on the airframes

I need to "practice" prepping the rockets and arming with bare ematches. Also have to practice with making sure the tracking systems are working properly. The TeleGPS I can monitor with a D72/Garmin 60CsX combo and I
did get the Altus Metrum TeleBT I have mounted on a 7 element Yagi. The AltoDroid app allows downloading and caching the aerial photos of the launchsite in advanced so one doesn't need an online internet connection. Very
helpful for some launch venues. The EggTimer TRS will use the Android GPS Rocket Locator on the receive end. Kurt

Well, I started this thread and then didn't make a post after May (but thanks a bunch Kurt for your postings on your progress!). Around that time I sanded the edges of the fins and got them attached using Proline 4500 Epoxy, the black color of this epoxy was perfect for this rocket, though man that stuff is messy, I wound up with a few spots on the tube that went dark and wouldn't lighten-up no matter how much isopropyl I used to try to wipe it off before it cured. I had started working on the electronics bays (nose for GPS and mid-bay for altimeter) but was seriously blocked on getting my recovery bits to fit.

I wound up ordering some extra pieces from RW, I wanted av-bay bulk plates that didn't have the center hole as I wanted to drill offset holes for my all-thread, and I was convinced there was no way I could make my main chute fit in the upper BT, so I ordered a 2' tube instead of the 1' it came with (though I had planned to cut it down to more like 15-18", it just happened to be sold in foot increments). And then I broke my wrist mid-June so that halted all rocket building for a good ~10 weeks.

Anyway, first a shot of the fins. I roughed-up both the edge of the fins and the tube where the fins would attach, used the provided fin alignment guides to position the fins and tacked each one in place using a few drops of CA, which then allowed me to remove the guides without disturbing the fin positions and use my fin alignment jig to support the rocket while pouring the fillets and shaping them without interruption from the guides. I used the tip of a plastic spoon to shape the fillets.



But XPRS was coming up last weekend and there was no way I wasn't going to fly this thing, so I got busy last week once I was finally cleared to lift more than a pound with my hand again.

For the nose, I epoxied the coupler into the nose, and purchased one of Chris Attebery's APE - Altimeter Bay System for Wildman/CTI 38mm Nose Cones (specifically version 1 without the charge well, pictured here). This was a great fit in the coupler, and included a thin fiberglass sled that fits fine in this NC. I picked up a tiny set screw that matched the hole on the machined bulkplate and drilled a hole in the coupler to hold the NC to the bulkplate. I added some wood to shift the sled a bit more towards the middle, so that I could fit the battery on one side of it and the Eggfinder TX on the other side.



For the altimeter bay, I had decided to go with a design similar to GLR's Firestorm 54 that I had built previously, where the coupler that forms the bay is epoxied into one end of the upper BT, and the sled and upper bulk plate feed in through the upper BT and then get capped at the bottom. My goal was to minimize the number of places that could separate, so the upper BT only opens at the NC. I used the vent band even though the coupler is permanently attached to the BT, the extra 3/4" helped give more room for the main chute in the upper BT. I only left about 2" of the coupler exposed below the vent band to minimize how much space I took up in the lower BT. This confused the RSO on the first launch, as they saw the vent band but also saw no holes in it, the vent hole is a bit higher up for reasons I'll get to later.

Each of the bulkplates had an offset hole drilled (I drilled through both at the same time, using the vent band to align the two pieces). For the all-thread through the bay I used two long forged eye-bolts I found at my local Orchard Supply, connected together with a long nut (not in the middle since one eye-bolt is longer than the other). The nut and upper (longer) eye-bolt was epoxied to the bottom of the fiberglass sled I cut to fit in the bay. Because of the offset the sled sits roughly at the center of the coupler, to give the maximum room for the StratoLogger CF, Featherweight Magnetic Switch and my 950mAh 2S LiPo. This LiPo is a bit too large for this application, it's the one I had standardized all of my electronics on but I'm going to order a smaller 2S for this rocket, both for the NC and the altimeter bay. I had to strap this battery very tightly to the sled with a minimal amount of tape as every layer counted towards getting it to fit. The wiring harness was custom-made to my spec by Bill at Dog House Rocketry (and also uses his charge wells which I love for the through-the-bulkplate wiring), though I messed up a few things in my spec so I'm going to re-order it with some tweaked numbers and the wire colors reversed (I had standardized on brown for drogue and orange for main but I didn't think this one through properly apparently, and the wire lengths were a very conservative guess and I should have gone shorter to minimize extra wiring I need to stuff in this cramped bay). The magnetic switch wiring also turned out to be very cramped, but I had no problem turning the altimeter on and off. I positioned the vent hole for the bay such that you can see the magnetic switch's LED through it when the sled is positioned properly (it also indicates where the magnet needs to be swiped to arm the rocket).



For the lower BT shock cord attach and motor retention I went with the Aero Pack M38E. This allows motor retention via a threaded forward closure on AT motors, and the Aero Pack MC38 for CTI motors. After much debate on whether I was going to have enough room for the drogue I positioned the retainer such that I could thread in my 6GXL CTI case, which puts the top of the retainer about 8.5" from the top of the BT, which leaves less than 7" for the drogue and 11' of 1/4" kevlar, more like 6" or less once the quick-links and charge well are accounted for. My original thought was to go with a pair of 4x56" mylar streamers for the drogue, but I didn't leave myself enough time to fold them and attach a cord at the end, so I wound up buying a 9" chute on the field instead. For the main I went with an 18" chute I already had, though I should look to move up a bit on this I think, maybe 24" or 30" if I can get one to fit, the upper BT ends up with about 6.5" for its chute and 11' of 1/4" kevlar as well.

The position of the motor retainer requires a good number of Aero Pack's extenders for the 38/360 casing I used for my first flights, I should pick up a piece of all-thread long enough to use a single small coupler, assuming it weighs less than all of the Aero Pack bits.



NOTE: There is indeed a fillet crack on the next to the last picture, more on that in the next post.

And I have no rail guides attached, deciding to go with Bill Cook's fly-away rail guide. So on the outside of the rocket there is nothing but the fins and 3 1/8" holes, one for each BT section and one for the altimeter bay.

So overall I'm quite happy with how my build turned out. Ideally I would have preferred the kit with about 3" extra on both the upper and lower BTs, and then I would have skipped the vent band entirely and felt a bit more comfortable on getting the recovery bits to fit. I also suggest getting the altimeter bay bulkplates without the center hole and drill your own offset hole to allow for more height for electronics. My weight with all electronics but no motor comes out to 2 lbs, 2.7 oz. Smaller batteries might get me a bit closer to 2 lbs even, without the motor.

After scrambling to finish the bays and get the batteries squeezed-in at the launch, I decided to go with an H148R for the first flight, liking the red flame for the red rocket (and the Red Devil name I decided to go with) and the altitude which initially sim'ed right around 3000 feet. It took a bit of work getting the fly-away rail guide to move smoothly on the rail, the rollers were loose but they resulted in a pretty tight fit on the Aeropac 1010 rails, I think the screw head size was part of the problem here, seemed like it might have been dragging on the inside of the rail. But I had added some thin strips of duct tape to get what I felt was a snug fit of the 3D-printed guide when holding it in my hand at home, I wound up removing almost all of this tape at the pad, but it was still a tight enough fit that when I slid the rocket on the rail the guide stayed with the rocket and didn't move around (and my pad camera footage showed that the guide remained clear of the fins during liftoff).

The flight itself definitely could have gone better. Around 800-900 feet the rocket separated prematurely. I don't know exactly why, I had 1/8" vent holes on both airframe sections, and they were placed such that air trying to get out these holes would not pull the laundry towards the separation points. I'm not even sure just which section separated first. The nose coupler had several layers of tape to make it a pretty tight fit (trying to ensure it wouldn't come out during the main separation without using shear pins), I had no tape on the lower coupler and it was a quite loose fit there. It definitely wasn't an altimeter malfunction as both charges could clearly be heard going off during descent, when the SLCF said it fired them per its output. During the sudden deceleration the motor casing, which I had friction-fit in since I didn't have the proper threaded closure to secure it to the M38E retainer, was hurled out of the rocket. Thankfully it was found standing on the playa(!) not too far from the rocket. The rocket itself landed with both chutes deployed and light the weight of the motor casing (about 30 ft/s), so it was undamaged (a nice touch compared to my previous experience with cardboard rockets where such a sudden deceleration would have made a rather large zipper). The sudden deceleration seemed to do a number on my Eggfinder though, it refused to obtain a GPS fix after this flight, though it reported a fix while it was on the ground before I powered it off, and it could still get time from the satellites when I powered it on again. The SLCF survived the flight without trouble.



After consulting with several L3's I knew at the launch who inspected my rocket, they couldn't offer any suggestions on why it had separated early. As I thought about it the only things I could come up with is that the rather tight packing of the laundry in the rocket might have effectively plugged one or both of the vent holes, or else perhaps there was enough drag/deceleration after burn-out to cause the lower coupler to separate. So I decided to try a second flight with the same motor (realizing the cliche about doing the same thing while expecting a different result). The things I did different the second time was to add some tape on the lower coupler to make it a tighter fit (but still not as tight as the NC coupler), to ensure the laundry was packed such that the shock cords lined up with the vent holes instead of the chute protector (to ensure the vent holes wouldn't be obstructed), and I purchased a threaded forward closure (actually the spoked closure since I was flying the 38/240 reload in a 38/360 casing with the RAS) so I threaded the motor casing in this time to make sure it wouldn't get tossed again even if the same failure occurred. The extenders did add quite a bit of weight however, taking the loaded weight from 46.2 oz up to 54.8 oz, lowering the sim'ed altitude from a bit under 3000' to more like 2400'.

The second flight thankfully was not a repeat of the first, but it also was not exactly successful. The rocket remained together until apogee (reported at 2674' by the SLCF), and the drogue and main charges fired as expected. However the drogue lines got tangled at deployment, and the main melted together so apparently my chute protector didn't remain properly wrapped around the chute as I loaded it in. So the main didn't open at all and the drogue was only partly open, and the rocket hit the ground at around 60 ft/s and cracked the fillets on one of the fins. I should be able to remove the existing fillets and lay down new ones I think, that will be a project for tomorrow or next weekend as I'm hoping to fly this rocket again at October Skies in 3 weeks. This second landing totaled the Eggfinder, the GPS antenna popped off, again the SLCF survived just fine.



So I'm already thinking about what other motors I might want to try in this, I'm going to stay away from DMS motors since I have no way to thread them into the M38E retainer and I don't trust friction-fit after the first failure. I would like to break a mile on this rocket and it looks like an I212SS, I154J or I195J would be in the right ballpark (the first two may be a bit low with the added weight of the motor retainer). Most bigger motors start to push the rocket past mach which concerns me, though the J94 and J150 remain sub-mach and simulate to 8400+ and 11400+, so I'll probably give one of these a shot once I have my L2 (I'm not planning to use this rocket for my L2, I'll use my Binder Excel w/DD for that). I'd like to see if I can move up to a 24" chute while still getting it to fit in the tight tube, I'd like to try to slow down the landing a bit more if I can, especially since one of the sites I like to launch at has a lot of rocks on the field.

I thought the GPS antenna was gone in the picture you showed above. You might be able to salvage it by carefully removing the base and you could direct wire another GPS receiver. I'll post a picture of one of my units I've done that with. The new EggFinder design
might be worth investing in. A lot easier to swallow that loss than a >$200.00 device though. :wink:

I have my ejection charges sized for two, 2-56 nylon shearpins that might help with preventing premature separation. I believe the fin attachment is probably going to be good to Mach 1.5 for sure. Alexis pushed his to Mach 2.5 on a J1000 but also thoughtfully laminated the fincan.

Yeah, the rocket could use a few inches on the upper bay tube. I keep swearing I'm going to stop doing small rockets because it's a pain to get everything to fit. If I had a do-over, I'd do the ebay like Jim Hendricksen suggests. Thanks for sharing the flight Will.

Kurt Savegnago (might as well start throwing in the surname now)

ksaves2 said:

I thought the GPS antenna was gone in the picture you showed above. You might be able to salvage it buy carefully removing the base and you could direct wire another GPS receiver.

Click to expand...

Yeah, all of the pictures were taken post-launch, so post-damage also. This particular EF was a bit of a kit-bash anyhow, I had planned since April to build this one as an auto-start version and with the ability to reprogram the TX frequency. I started soldering the kit the morning of 9/12, and when I went to the Eggtimer page to make sure I had the latest assembly guide I found that just about a day earlier Cris had released the newer version which was designed with all of the features I was going to hack. So I ordered one that morning (and had it by Monday, thanks Cris!!) but decided to build this one the same way, making some minor detail changes based on how the rev B6 board works. I flew a B6 board in my other rocket last weekend and that one survived just fine. In addition to the GPS antenna being destroyed on this hacked B4d board it also crushed the "PGM" jumper I added, which turned off the GPS transmission since the Hope module was put into CONFIG mode by the jumper pins touching each other. This also would be easy to fix, but I intend to just order two more of the rev B6 TX's and have a clean set of (non-rebuilt, non-hacked) Eggfinders. And I saw a recommendation somewhere on Cris's documentation about taping the antenna module down to help protect it, I probably will start doing this moving forward, at least on the sleds where I can leave the EF in place. But I suspect most of the damage was done by the large battery and it's mass and the tight fit it created in the NC, so I think I'll make things much more reliable by going with a smaller battery underneath the GPS as well.

I really was aiming for no external protrusions, so I wanted to avoid even having shear pins. So long as pressure separation can be avoided I seem to have the NC tight enough that it won't throw out the main at apogee. Of course a sudden deceleration from ~300mph doesn't seem to be something any friction-fit can reasonably be expected to withstand, so I'll hope that doesn't happen again and stick with the NC friction-fit and the motor threaded in. The worst that can happen if the NC separates is the main deploys early and the rocket travels farther from the pad, but tossing the motor casing is something I absolutely will not risk happening again, it landed on the range but wasn't far from the flight line so it could have been much worse.

"I really was aiming for no external protrusions, so I wanted to avoid even having shear pins. So long as pressure separation can be avoided I seem to have the NC tight enough that it won't throw out the main at apogee. Of course a sudden deceleration from ~300mph doesn't seem to be something any friction-fit can reasonably be expected to withstand, so I'll hope that doesn't happen again and stick with the NC friction-fit and the motor threaded in. The worst that can happen if the NC separates is the main deploys early and the rocket travels farther from the pad, but tossing the motor casing is something I absolutely will not risk happening again, it landed on the range but wasn't far from the flight line so it could have been much worse."

Yeah,
I thought about it too but kept saying over and over to myself, "It's only a hobby. It's only a hobby. It's only a hobby." The little buttonhead screws and the nylon screw/shearpins will create drag to keep me under the
15k waiver at the local launchsite.:wink: The couplers with the GD38 are thick and I've so far had luck simply drilling and tapping them for 2-56 screws. I figure if mine survives a J350, I'll downsize the motor for a
given launchsite as needed. :smile: Kurt Savegnago

I got mine last week and I've been thing of a different approach to keeping the weight down. I was thinking of putting my Eggfinder in the NC and below that a Quark and below that is the separation point. I was thinking separate at apogee and pop a streamer. Im still thinking on motor retention.

I did my third flight this past weekend at October Skies. My goal with this rocket was to break a mile (5190' being my previous high), OR sim'ed ~5300' with an I285R, but it's sim for the H148R was lower than it turned out (2000' vs. ~2500'), when I tweaked my ThrustCurve parameters to get the altitude I got out of the H148R that put the I285R more like 6000', so I figured it was a safe bet to get the mile.

I was also curious about G's, so I did some experimentation beforehand and found that the AltimeterThree fits *perfectly* in the area I had inside the motor mount area, so I could tape it to the 5/8" all-thread that runs up to the M38E retainer, and placed a fender washer above and below it to ensure it wouldn't move up/down the rod (I have an idea to make this lighter, need to talk to someone who can machine metal for me), and drilled one more hole in the airframe just below the M38E so that the A3 could get a pressure reading. So while there was no more room in the electronics bay or NC I was able to turn my motor area into another payload bay (the A2 would also fit but you'd have to set it to flight mode before loading the motor into the rocket, at least the A3 can be set to launch mode via bluetooth provided it doesn't take more than an hour from loading the motor to arming on the pad).

I got 3820' out of this motor. At first I was totally stumped as to why it would come in so low. But as I went back to the launch pad to recover my fly-away rail guide, I couldn't find it, even in widening circles working out from the pad. When I went back to check out the video from the 2 ground cameras (up-looking action cam, 720p/240fps, handheld super-zoom 1080p/60fps) to see if I could tell when it came off, the rail guide apparently stayed on the rocket all the way to apogee. So I guess the extra drag is what hurt the altitude so much. I really don't know why it didn't come off, the rubber band worked when I put it on, and the video shows it was still pretty clear of the fins as it left the rail (shouldn't have hung-up on the fins or anything). In fact in some of the video I got of the rocket coming down under chute the rail guide was in the frame, tumbling down on its own. But I have no idea where it landed, so it's still somewhere out on the field. So truth in advertising, my fly-away rail guide really did "fly-away", and I still haven't managed to break a mile. But both chutes came out, I had replaced my 9" drogue with a 12" and my 18" main with a 24" (both Top Flite thin-mill chutes), I think I'll go back to 9" on the drogue, and I need to take a second look at the data as it seems the main came out early (more like 3000' instead of the programmed 700' on the SLCF), but it didn't seem to come out during the apogee separation. I haven't downloaded from the SLCF yet, only the A3, so I'll have to see what it thought about the altitude and when it fired (it was beeping out 3821', so it agreed with the A3's reported 3822'), I didn't hear any pops later on as I would have expected around 700'. Plus of course I need to buy another rail guide, this time I'll be writing my name / phone number on it just in case it is lost again.



I also realized that for some reason I had positioned the chute closer to the coupler than the lower BT, and when the main fired (or deployed without firing) the upper and lower shock cords got a bit tangled, though it didn't interfere with either chute. I really should re-position the drogue chute attachment loop such that the upper section would be below the lower section as it comes down, which I think would be less likely to tangle.