First Attempt at a 38mm Minimum Diameter Launch!

[charrington]

Hello everyone!

I am currently certified Level 1 and will be attempting my Level 2 certification this weekend at ROC (assuming it doesn't get rained out. EDIT: it did get rained out! What a bummer :/) I will be flying an older version of the Go Devil from Madcow rocketry. I purchased it about 4 years ago but between University and Covid, I hadn't been able to start building it until a few months ago. It is basically complete besides another pop test I will be conducting today. I am flying it on an Aerotech J570. I completely understand that this goes against all reason for a certification flight and I am someone who is usually on the side of 'Low and Slow' when it comes to certs. However since it has been awhile since I've been able to focus on my own personal rocketry projects, I wanted to try something special.

I am using the Rocketman ultra light weight parabolic chute for my drogue and the ultra light weight high performance chute for my main. My GPS is an eggfinder TX and I was somehow able to squeeze my eggtimer proton into the AV bay. This build has really given me a lot of respect for the altitude record chasers and I can imagine how much of a pain in the a** it is to do a flying case or 29mm attempt. For fin attachment I followed the techniques described in the thread "Properly bonding composites and what your government doesn't want you to know." by flynfrog. I went down the epoxy-rabbit hole and elected to use Hysol E-120HP (I'm sure JB weld would have worked great) with a half-inch radius. I was expecting this epoxy to be less viscous so they aren't the greatest filets but still extremely strong. Next time I will definitely add a thickening agent like West systems 406 silica for the fillets but leave the root bond unaltered. I clamped them and put into a homemade "oven" where I let them cure.

To retain the motor I used an aeropack min diameter retainer which I drilled and tapped a few screws into so that I can remove it and possibly fly a Loki K627 in the future (I hope!). I was a little worried about the thinness of the airframe and retainer so I Jb-welded nuts on the inside of the retainer to add some more metal for the screw to grab onto. I took photos during the build and if this post gets any attention I will do a post flight build thread! I need to update my sim one last time but I am looking at about 14k ft and about Mach 1.5 in open rocket. Max G-force experienced according to OR is 64.

Anyways, has anyone that's reading this flown anything similar? If you have any last minute tips for launch day besides study the written exam I would love to hear them. Questions and criticisms are welcome!

 

[Steve Shannon]

Good luck. That’s an ambitious project but it sounds like you did all the right things. Make sure you do something to prevent early separation when that motor shuts down. Vents plus something to resist drag separation (friction, shear pins, or shear tape).

Please report back with video.

 

[David Schwantz]

I have all the Go Devils, even a couple of modded ones. She will fly straight and fast. I do use fly away rail guides. Good luck. And since I suck at videos, yours can only be better

 

[cwbullet]

Good luck. I am launching a 29mm minimum, Thor, this weekend. It is a 50-meter bird (not good-looking), but we will see how it flies. It is dual deployment, and I am thinking about whether to fly on a G80 or an F.

 

[manixFan]

I have flown a number of 38mm MD rockets, based on the Mongoose, which is very similar to the Go Devil. I've done both the CTI extremes - the J150 and the J530. (6XL case.) It is a challenge working in such a tight area for recovery – I ended up using a 24" high CD Rocketman chute. Since either of those motors end up in the 15K' altitude range, I don't use a drogue so I can get the rocket down faster and closer to home.

I use a tower to launch, but that is a pain. But I've had bad luck with the fly-away rail guides. They seem to break or get lost on nearly every flight.

I really like the Loki K627 and have flown it a number of times. It's a great motor. At BALLS this past fall I flew 'the big three' - the highest impulse 38mm motors from Loki (K627–1619Ns), CTI (J530–1115Ns), and an Aerotech (J510–1162NS), plus a J150 to mix it up. For the money, the high impulse 38mm motors are a lot of fun and can grab some serious altitude.

For launch day advice, have a checklist for flight prep and actually use it! It's amazing how many folks make one up and then somehow don't use it as they prep. And don't let folks interrupt you as you prep – it's too easy to get distracted and do something dumb. But that's where a checklist really helps, it forces you to keep track of each step. I also try and take pictures of how I've rigged my charges and recovery, so I can refer to them later if things go sideways.

Good luck and enjoy your flight!


Tony

(photos of a couple of motors (K672 and J510) here – they were flown in a Shadow Aero Raven though. I flew the J530 and J150 in the Mongoose (no pictures unfortunately)
https://www.rocketryforum.com/threads/3-rail-6-launch-tower.175568/#post-2342468

 

[charrington]

Good luck. That’s an ambitious project but it sounds like you did all the right things. Make sure you do something to prevent early separation when that motor shuts down. Vents plus something to resist drag separation (friction, shear pins, or shear tape).

Please report back with video.

Thank you! I've been reading a lot of the build threads from people attempting altitude records. I picked up some 2-56 shear pins and will be installing those to prevent early separation. ROCstock was cancelled sadly so I am unable to launch this weekend. I will try again later this month or December and I will make sure to post a video!

I have all the Go Devils, even a couple of modded ones. She will fly straight and fast. I do use fly away rail guides. Good luck. And since I suck at videos, yours can only be better

I am planning on using fly away rail guides too. Its reassuring to hear that you have had successes with them! I really like the Go Devil kits but was thinking about doing a Blackhawk sometime in the future too!

Good luck. I am launching a 29mm minimum, Thor, this weekend. It is a 50-meter bird (not good-looking), but we will see how it flies. It is dual deployment, and I am thinking about whether to fly on a G80 or an F.

Good luck to you too! I hope it goes well. I have a G80 sitting around that I wanted to launch in a fiberglassed Estes Nike smoke. I'd say go with the G80!

I have flown a number of 38mm MD rockets, based on the Mongoose, which is very similar to the Go Devil. I've done both the CTI extremes - the J150 and the J530. (6XL case.) It is a challenge working in such a tight area for recovery – I ended up using a 24" high CD Rocketman chute. Since either of those motors end up in the 15K' altitude range, I don't use a drogue so I can get the rocket down faster and closer to home.

I use a tower to launch, but that is a pain. But I've had bad luck with the fly-away rail guides. They seem to break or get lost on nearly every flight.

I really like the Loki K627 and have flown it a number of times. It's a great motor. At BALLS this past fall I flew 'the big three' - the highest impulse 38mm motors from Loki (K627–1619Ns), CTI (J530–1115Ns), and an Aerotech (J510–1162NS), plus a J150 to mix it up. For the money, the high impulse 38mm motors are a lot of fun and can grab some serious altitude.

For launch day advice, have a checklist for flight prep and actually use it! It's amazing how many folks make one up and then somehow don't use it as they prep. And don't let folks interrupt you as you prep – it's too easy to get distracted and do something dumb. But that's where a checklist really helps, it forces you to keep track of each step. I also try and take pictures of how I've rigged my charges and recovery, so I can refer to them later if things go sideways.

Good luck and enjoy your flight!


Tony

(photos of a couple of motors (K672 and J510) here – they were flown in a Shadow Aero Raven though. I flew the J530 and J150 in the Mongoose (no pictures unfortunately)
https://www.rocketryforum.com/threads/3-rail-6-launch-tower.175568/#post-2342468

I was seriously considering doing a drogue-less recovery and I probably would go that route for my next flight. I was just worried about doing it on a certification flight. I didn't know if the TAPs would like that especially if its my first min diameter launch. Better safe than sorry! I am using fly away guides so I hope I don't run into that problem. I will definitely make a check list and tell my friends to leave me alone for a little bit lol. I've noticed the K627 has been out of stock for awhile now so I hope I could pick one up soon if stock pops up. Thank you for the advice! I

 

[charrington]

Since Lucerne is now a wet lake bed instead of a dry one, I will try to post a build thread with pics!

 

[GrouchoDuke]

38mm MD rockets are a ton of fun. Great altitude on cheap-ish motors and they're big enough that you can still pretty easily fit electronics in them. Like others have said here & other threads: checklists help, ground test everything, have good tracking and a plan for hunting it down after it lands. Have fun!

 

[charrington]

38mm MD rockets are a ton of fun. Great altitude on cheap-ish motors and they're big enough that you can still pretty easily fit electronics in them. Like others have said here & other threads: checklists help, ground test everything, have good tracking and a plan for hunting it down after it lands. Have fun!

Yeah I cant wait to see it disappear into the clouds! I will post a video when I get to launch.

 

[GrouchoDuke]

Yeah I cant wait to see it disappear into the clouds! I will post a video when I get to launch.

They definitely disappear!

 

[plugger]

Thank you! I've been reading a lot of the build threads from people attempting altitude records. I picked up some 2-56 shear pins and will be installing those to prevent early separation. ROCstock was cancelled sadly so I am unable to launch this weekend. I will try again later this month or December and I will make sure to post a video!

Given it's a 38 you should be fine with a single 2-56 shear pin. I normally only ever use one 2-56 for 38, 54, and 75mm MD flights and I've never had an early separation. The last 54 went so fast it melted the head of the shear pin and it still worked fine.

 

[charrington]

Given it's a 38 you should be fine with a single 2-56 shear pin. I normally only ever use one 2-56 for 38, 54, and 75mm MD flights and I've never had an early separation. The last 54 went so fast it melted the head of the shear pin and it still worked fine.

Alright sounds good! I figured the 2-56 pins would be beefy enough to just use 1. Question. Do you or anyone else know what a good amount of BP is for a rocket this size? I pop tested using the values I received from a calculator and it was NOWHERE near enough. I packed the charges pretty tightly so I don't believe it was due to the BP not burning completely. The Calculator gave me a value of about .06 grams for both drogue and main. I didn't believe this so I bumped it up to .08. I am using FFFFg.

 

[manixFan]

Alright sounds good! I figured the 2-56 pins would be beefy enough to just use 1. Question. Do you or anyone else know what a good amount of BP is for a rocket this size? I pop tested using the values I received from a calculator and it was NOWHERE near enough. I packed the charges pretty tightly so I don't believe it was due to the BP not burning completely. The Calculator gave me a value of about .06 grams for both drogue and main. I didn't believe this so I bumped it up to .08. I am using FFFFg.

Hmm, .06 or .6? It's a small volume to pressurize so it does not take much, but I have had trouble due to the tight fit. I have found rolling up the chute very tightly in the protector and then folding over the bottom seems to help it slide out more easily, and I always use talc inside the tube and on the protector (now cornstarch unless you already have a stash of talc somewhere). I have spent a considerable amount of time trying different packing techniques to get reliable deployment. Since you have plenty of time it seems, I highly recommend doing the same and keeping good notes.

My biggest problem when I first started doing MD was using too much BP and also using short recovery harnesses due to space. The result was very high g forces at deployment when the sections hit the end of the harnesss. I suffered a recovery failure as a result. At this last BALLS, for the drogue (on the 38mm Mongoose) I used .25 grams with .5 as backup, and for main it was .4 with .7 as backup (I only used one shear pin). (I am relying on memory so I may be a little off.) The altimeter was a Featherweight Raven 4 which has 4 outputs, so I configured the extra two to fire the backup charges.

If you do get your hands on a K627, make sure to read through the instructions. When I got my first one I called Scott and asked him how to put it together. He very politely walked me through it and I wrote it all down. Then I opened the kit up all the way and realized he basically just read me the instructions. I felt pretty dumb! You'll want to practice the assembly procedure a couple of times before you mix up any epoxy to glue the grains into the liner. It's not hard, but it is a bit nerve-wracking.

I hope you get some good flying weather soon!


Tony

 

[plugger]

Yea, for a 38mm with kevlar for a recovery harness I'd be targeting 0.5g for Apogee and 0.7 for backup, similar to what Tony said. Ground test, but as per usual it's better to blow it apart and have a recovery failure when compared to coming in ballistic.

 

[cwbullet]

I would echo @plugger 's ground test. Nothing good usually comes from skipping that step.

 

[David Schwantz]

Fly away rail guide trick is to position the buttons over a fin. this way when it opens it is in the "V" of the opposite 2 fins. That is on a 3FNC rocket.

 

[robopup]

Alright sounds good! I figured the 2-56 pins would be beefy enough to just use 1. Question. Do you or anyone else know what a good amount of BP is for a rocket this size? I pop tested using the values I received from a calculator and it was NOWHERE near enough. I packed the charges pretty tightly so I don't believe it was due to the BP not burning completely. The Calculator gave me a value of about .06 grams for both drogue and main. I didn't believe this so I bumped it up to .08. I am using FFFFg.

One other option for holding things together:

On all my rockets 3" diameter and smaller I use aluminum tape instead of shear pins. Usually I use three pieces spaced evenly around the tube. This is the stuff I like (as much as I hate shopping at home depot): https://www.homedepot.com/p/Nashua-...Weather-HVAC-Foil-Duct-Tape-1541238/100507541

Here's an example:

 

[plugger]

lol, Home Depot has geofenced their site from Australia. Incredible.

 

[manixFan]

lol, Home Depot has geofenced their site from Australia. Incredible.View attachment 545734

Were you using a VPN to access it? I find that many sites now routinely block any traffic from a wide variety of VPN, mostly as a security precaution.

Tony

 

[b.wieting]

Think Eggfinder. Not too hard to build.

 

[plugger]

Were you using a VPN to access it? I find that many sites now routinely block any traffic from a wide variety of VPN, mostly as a security precaution.

Tony

Nope. I'm on a wired connection from a major Australian ISP and my geolocation is out of Brisbane. Just turned wifi off on my phone which is Optus/SingTel and my IP is out of Perth and the site is also blocked on it. Seems like they've sink holed our entire country/continent.

 

[ghostfather]

HomeDepot is also geofencing most European countries, though my VPN using an east or west coast USA exit point gets me through.
I'd never thought of using alu tape for this, but it's something worth trying.
I've got the 38mm Go Devil ready for a couple of personal altitude records, I just need to find a field here in Europe with a high enough ceiling, otherwise make the pilgrimage to fly in the States. It sims to 11,500 ft on a CTI I216 Classic, and 14,800 ft on an CTI J150 Mellow Yellow, enough for personal altitude records.

 

[charrington]

Hey everyone!

Been a long few days. Between getting my colleagues ready for their L1 certification and troubleshooting their avionics I haven't been able to work on my rocket much. Every time I agree to mentor the Level 1 course through a rocketry club on campus I always wonder why I put myself through it but I know it will be rewarding in the end ! If all goes well with this group of students I think I will have somewhere around 50 L1 certs underneath me which has been making me feel quite strange as I am also in my last semester before I get my degree. It's been a long time coming.

Anyways I was able to pop test last night 11/12/22 and it was... unsuccessful! Two major issues I ran into:
1. Eggtimer Proton lost continuity on my main channel. Pulled it out to see what the issue was and ran into something strange. (Ill get to this later in a separate comment after the board can be properly examined). We decided to just shut this channel off and then test the drogue channel alone since it was getting very cold out and my hand dexterity was approaching catastrophic failure.
2. When we fired the drogue it did have a nice boom and ejection of the AV Bay. I increased my BP from 0.06 (calculator value) to 0.5 grams which is what a few of you recommended (Thank you a lot!). However the parachute was not pulled out. I gave the shock chord a pull and found that the chute was completely wedged inside the body tube. I mean COMPLETELY wedged. No amount of pulling could free this guy. We decided to try and pull the chute out the back after removing my motor retainer and motor case. We discovered that the quicklink I was using was wedged! I don't know why but I hadn't thought of "Hey, if this thing turns sideways its length is longer than the airframe diameter". All in all I'm really thankful it went wrong tonight. Im really glad that I didn't get lucky and then have this happen when I launch. I think I will be getting rid of the quicklinks altogether and just using a double overhand knot to fasten the chord directly to my parachute swivel and eyebolts.

 

[charrington]

Hmm, .06 or .6? It's a small volume to pressurize so it does not take much, but I have had trouble due to the tight fit. I have found rolling up the chute very tightly in the protector and then folding over the bottom seems to help it slide out more easily, and I always use talc inside the tube and on the protector (now cornstarch unless you already have a stash of talc somewhere). I have spent a considerable amount of time trying different packing techniques to get reliable deployment. Since you have plenty of time it seems, I highly recommend doing the same and keeping good notes.

My biggest problem when I first started doing MD was using too much BP and also using short recovery harnesses due to space. The result was very high g forces at deployment when the sections hit the end of the harnesss. I suffered a recovery failure as a result. At this last BALLS, for the drogue (on the 38mm Mongoose) I used .25 grams with .5 as backup, and for main it was .4 with .7 as backup (I only used one shear pin). (I am relying on memory so I may be a little off.) The altimeter was a Featherweight Raven 4 which has 4 outputs, so I configured the extra two to fire the backup charges.

If you do get your hands on a K627, make sure to read through the instructions. When I got my first one I called Scott and asked him how to put it together. He very politely walked me through it and I wrote it all down. Then I opened the kit up all the way and realized he basically just read me the instructions. I felt pretty dumb! You'll want to practice the assembly procedure a couple of times before you mix up any epoxy to glue the grains into the liner. It's not hard, but it is a bit nerve-wracking.

I hope you get some good flying weather soon!


Tony

.06. Yeah it was way too low. My common sense was telling me the same thing too. I was using the BP calculator and factoring in only the empty space of my tube. I just went with the 0.06g of BP because I would rather the calculator be wrong and I have a little sizzle of than the calculator be right and my ego damages my airframe lol. I will have to try using cornstarch. Do you put a lot or just a light dusting usually? Also, I'm running a 15 ft kevlar chord as I dont have much room for more. I figured this would be enough although I usually prefer having a 5:1 shockchord to rocket length for apogee deployment.

Fly away rail guide trick is to position the buttons over a fin. this way when it opens it is in the "V" of the opposite 2 fins. That is on a 3FNC rocket.

Thank you for the advice! I did not know that until now.

One other option for holding things together:

On all my rockets 3" diameter and smaller I use aluminum tape instead of shear pins. Usually I use three pieces spaced evenly around the tube. This is the stuff I like (as much as I hate shopping at home depot): https://www.homedepot.com/p/Nashua-...Weather-HVAC-Foil-Duct-Tape-1541238/100507541

Here's an example:
View attachment 545732

That is really convenient! I am gonna check that out sometime.

 

[charrington]

Big update everyone!

So I have been super busy with school so I haven't been able to focus on my rocket which saddens me but I have made some very good progress! Also, I just graduated with my degree in biology yesterday so maybe I will have some time to get this L2 launched now! Last weekend I was able to make it out to lucerne to launch some L1s that I taught through my school. Out of the 9 people we had their: 7 certified, 1 no launch (window closed and was relying on a shared altimeter, couldnt get both of theirs setup in time), and 1 failed cert (my fault, my gut was telling me to make his shockchord longer and his parachute ended up getting tangled and he hit the ground hard and broke a fin. I will buy him a kit since I feel responsible, a fiberglass one this time). We had 3 people use dual deploy systems and all were successful: 1 eggtimer proton, 1 eggtimer quantum, 1 Raven 3. DO NOT allow level 1's to launch their first rocket on electronics, I have gray hair now. Maybe that's an exaggeration but I highly recommend against it. The reason I allowed it is because this was my last semester here and if any of you know cal poly pomona's rocket recovery history... it's not great lol. I hadn't been apart of the rocketry clubs since before the pandemic so I figured I would have one last go and pass on my knowledge. Now I am confident that there are at least 3/4 students who are competent at using electronics for recovery. It was very stressful teaching people who had never launched a personal rocket at all before: Proper composite bonding, OpenRocket simulations, SolidWorks for lazercutting, General rocket theory (CP,CG,ShockCord Length, Parachute sizing, etc.), and electronic deployment. 10/10 feel accomplished but 0/10 would do it again.

Anyways, I have some photos from the go devil build and will be posting what I have so far down below!

 

[GrouchoDuke]

Congrats on the degree and the Lucerne launch! Now get that L2 rocket ready to go!

 

[charrington]

So this will be from the start:

I used 220 grit sand paper on an orbital sander to sand the areas where the fins would be attached. I used the method described in the thread "Properly bonding composites ... gov doesnt want you to know". I would sand and then wipe with acetone until it passed the water break test and then sanded and wiped with acetone one last time. I did only 1 fin at a time since this was the first time I attempted this. I then used hysol E120HP to bond the root of the fin (after sanding the root with same method). This was then placed inside my homemade 'oven' and let cure for 1 hour. The temps inside this oven were reaching a very surprising 150F. Pretty good for a space heater and cardboard box lol. To hold clamp the fins down i used a mixture of metal clamps and masking tape wrapped around tightly.

What I would do differently:
1. Use less pressure while sanding. I definitely went into the fibers and took off too much material. Only necessary to remove the very top oxide layer which requires no excessive downward force.
2. Use a better fin alignment guide. The cardboard one that came with the kit was quite flimsy and couldn't be used to put a downward force onto the fin during bonding.

For fillets I used a 8% radius compared to root cord which ended up at just about .5 inches. I went to michaels and picked up a wooden ball dowel thing that fulfilled this measurement. I then used masking tape to tape off the area for fillets, sand till water break, re-masking-tape and then ran the fillets. They were allowed to cure for 5 minutes in the oven, I removed the masking tape, then let cure for an additional hour per fin. After seeing how strong these turned out I have come to the conclusion, as many record breakers have, that Tip to Tip is not necessary and may end up causing more problems than doing good. I believe that these could easily go past Mach 2 and I plan on testing that with a Loki K627 in the future. I'm not saying that tip to tip doesn't work, if you do it correctly it certainly does. It just takes a lot of practice and it needs to be perfect to avoid delamination or hinder performance when reaching very high speeds.

What I would do differently:
1. Add a thickening agent such as colloidal silica to prevent sagging. E120Hp is much too thin especially when placed in the oven to cure.

Now comes fitting the motor and retainer in...

 

[manixFan]

That looks like a great build. I've built a number of 38mm and 54mm birds almost exactly the same, and as you guessed, tip-to-tip is not necessary for going past Mach 2, at least with smaller rockets. For fillets, a properly sized marble or ball bearing glued to a stick works pretty much exactly the same as your tool but is much easier to clean, and possibly cheaper. (Hot glue works very well to attach the ball to a stick.) I've also transitioned to using 3D printed fin alignment jigs – they are much stronger and I've gotten more accurate alignment than using jigs cut from flat stock.

Maybe it's just the lighting, but it looks like your fillets may have been a bit epoxy 'starved', but you should be able to easily fill that in for a nice smooth radius. One thing I've learned is to try and stick to the same material for filler as you did for the fillets - basically just use more epoxy. I found that if I used a different filler it would 'pop off' under aerodynamic heating, leaving pits where it used to be.

I'm a big fan of the K627, having flown at least one at Balls for the last several years. They aren't cheap but there is nothing else like it really. I just wish they were easier to get. Keep up the good work on your build.


Tony

 

[GrouchoDuke]

For fillets, a properly sized marble or ball bearing glued to a stick works pretty much exactly the same as your tool but is much easier to clean, and possibly cheaper.

SharkBite PEX tubing is my favorite for shaping fillets. Lots of tape in all the right places, too. I buy it in 5' lengths in various diameters from Home Depot then cut 2-3" lengths. I do one set of fillets, wiping the PEX tubing with each swipe, then throw away that PEX chunk after 1 set of fillets. You can hold them at different angles to change the fillet radius, which helps especially at the trailing edge. Almost zero cleanup!

possibly cheaper. (Hot glue works very well to attach the ball to a stick.) I've also transitioned to using 3D printed fin alignment jigs – they are much stronger and I've gotten more accurate alignment than using jigs cut from flat stock.

I was going to say the same. It takes some iterating to get the exact size for your printer & rocket combo, but once you get them dialed in 3d printed fin guides are perfecto. That said, I think many people size & orient them incorrectly.

Anyway... awesome looking build! MD 38mm rockets are my fav!

 

[charrington]

So when I decided to put the aeropack motor retainer in I knew that I would want to be able to move it forward to be able to fit a K627 in it. For my L2 cert I chose an aerotech J570 because I love the acceleration of it and can launch it in California unlike Loki reloads. With this being said I used mechanical fasteners. I used the labrat rocketry 38mm nosecone sled guide to drill 3 equidistant holes into the aeropack retainer. I then used the 38/1080 case with the plugged and threaded forward closure (courtesy of Chris Rocketry supplies) to slide the retainer where it will sit in the rocket. I then used Christmas lights which I had sitting inside the retainer to light up where the holes in the aeropack retainer were which was visible through the fiberglass. I marked and then drilled these. It would have been much easier to use the labrat min diameter 38 retainer which comes with a drill guide that fits on the body tube (the nosecone drill guide fits couplers). However, I have had this kit and the aeropack retainer for about 4 years now and wanted to utilize what I had already purchased. I also could have just drilled through the airframe and motor retainer from the outside but it was nice having the holes perfectly spaced out. I then tapped the airframe and retainer with a 4-40 tap. The aeropack retainer is pretty thin walled metal and I wanted to add more beef and threads for the screws to hang on to. I took a 4-40 nut and this next part is important - I threaded the screw through the retainer (outside of the airframe). Once this was seated I then added the nut. This was important because if the threads didnt line up then there would be binding issues between the retainer drill threads and the nut threads. Once this was in I JB-qwik welded the sides of the nut. This was all sanded and cleaned before bonding of course.

What I would do different:
1. Use a labrat 38mm MD retainer! I ordered one anyway tonight because the aeropack retainer is so big. I will need all the space I can get with the K627. I wish I had more space now lol! At least im not wasting a perfectly good retainer though.
2. Dont worry, I know round head screws defeat the purpose of MD. I changed them out for set screws already. These were just needed so that I could get everything lined up properly!

Next came recovery, and lord let me tell you this is where the mistakes and money pit began to happen...