Motor retention in minimum diameter rockets

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RayGNJ

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Looking to build a minimum diameter 38 rocket and was wondering what you would use to keep the motor casing from coming out at ejection.

I was thinking, maybe use tape or trying Aeropacs mini dia mortor retainer.

Problem I have with the aeropack is you are stuck with it as it limits using longer motors.

I have an RT 720 6g case I want to use in it now, If I go with CTI I would be limited to only 5g.
 
For my MD 54mm I used the Aeropack retainer, but found the longest motor I plan on using (CTI 6GXL), and used three machine bolts to hold it in place. That way it is removable, and for shorter motors I use an extension. You can look in my build thread titled "My Madcow Tomach (Money Burner)" for ideas.

Cheers,
Kyle
 
I am planning on trying aluminum tape over the rear of the airframe and motor.
 
I also just used the 54mm MD Aeropack retainer in a new 54mm MD rocket.

As Kyle said you can just drill, tap and use some machine screws. I epoxied some self clenching nuts onto the inside the the Aeropack and have had it in and out of the rocket no less than a few dozen times at this stage. I sized it for the biggest case I plan to use, a Loki 54\2800 with extended bulkhead. But I can put anything in it with some simple adapters or even threaded rod; I am launching it this weekend at NYPOWER on a 1 grain CTI 54mm case. If I was planning on using more shorter motors then I would drill multiple mounting holes which would not be a problem, and do away with the adapters.

4-40 self clenching nuts epoxied inside

View attachment 263723

Had to make an adapter to go from Loki to Aeropack thread sizes

View attachment 263724

Flat head machine screws countersunk to sit flush and use a T10 head

View attachment 263722
 
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The Aeropack MD retainer can lead to problems with snap-ring motors!
If you allow the trust to press on the forward closure in a snap-ring motor, you will crush the liner and have a CATO.

These should only be used with the screw-type forward closures! [Maybe Ok with CTI, but I don't know their HW that well]
 
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Even if the thrust ring is touching the aft end of the motor tube?
 
Personally I say just use tape. It sound like you plan on flying it using fairly long cases and you should have no problems with the friction fitting method
 
The Aeropack MD retainer can lead to problems with snap-ring motors!
If you allow the trust to press on the forward closure in a snap-ring motor, you will crush the liner and have a CATO.

These should only be used with the screw-type forward closures! [Maybe Ok with CTI, but I don't know their HW that well]

This is not true. Despite what myself and others thought, applying thrust to the fore bulkhead will not CATO a motor.

Case in point...here's my tests of 38-2G motors at high pressures (1250 psi +) with the motor thrusting directly into brass fittings installed in the bulkhead:

[YOUTUBE]VXwve3S61l4[/YOUTUBE]
 
The force due to internal pressure against the forward bulkhead exceeds the thrust by a considerable margin. There shouldn't be a real problem with transferring thrust through the forward bulkhead directly to the airframe, rather than from bulkhead to case to airframe. However instability could wiggle the o-rings and that would worry me. Design details, of course!

Gerald
 
This is not true. Despite what myself and others thought, applying thrust to the fore bulkhead will not CATO a motor.

Your wrong........& your right.........& you were lucky. There are almost always exceptions to rules.
Depends on pressure & thrust. Some small motors & you can get aways with it.

Remember Rocket City Rednecks?
When they had 2-N-5800's in a project that had thrust on closures to bulkhead? It ended VERY bad. Enough thrust and your theory is toast.

That's the first one that comes to mind, I have seen others.:smile:

I just thought of another one:

Several years back at Airfest I witnessed a 2-stage where motor was used as coupler on sustainer to booster. [AMW 7600 case] Motor was M-something research.
Held in place by treaded rod in closure to bulk plate/coupler affair glued in.
Soon as sustainer lit it was Boom-Boom time. After post mortem it was obvious the closure was pushed back, crushing grains & liner. It was over before it started.

Guess when your old like me & been around long enough, you see just about everything.
But then, there is always the next surprise around the corner...LOl
 
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These should only be used with the screw-type forward closures! [Maybe Ok with CTI, but I don't know their HW that well]

FYI: All the Aeropack MD retainers can be used with Pro38 and Pro54 motors that they were designed for (i.e. all reloads).

Jeroen.
 
I see the argument both ways, however I believe build quality and attention to detail can play a big role in the outcome. So essentially it is no different than most technologies, it has to be used within it's specifications.

On my MD build the retainer is held firmly in place with machine screws, there is no measurable slack. The airframe is also carbon fiber, so compression should not be a factor. Also the retainer is positioned at a distance that allows me to very tightly turn the applicable motor hardware into it to get tension. Logically to my way of thinking, in this case when the motor hardware is under pressure there would be very little room for expansion, and subsequent forward closure movement or enough additional compression to cause a failure.

I will know one way or another as I plan on launching my rocket this weekend twice on the CTI I445 Vmax, then again at LDRS on a Loki K350 and possibly a L1400...if I can stay under the waiver. Regardless of the outcome, I will report back to this thread just to help those in the future sort out fact from fiction when deciding on what technology to use.
 
I also just used the 54mm MD Aeropack retainer in a new 54mm MD rocket.

As Kyle said you can just drill, tap and use some machine screws. I epoxied some self clenching nuts onto the inside the the Aeropack and have had it in and out of the rocket no less than a few dozen times at this stage. I sized it for the biggest case I plan to use, a Loki 54\2800 with extended bulkhead. But I can put anything in it with some simple adapters or even threaded rod; I am launching it this weekend at NYPOWER on a 1 grain CTI 54mm case. If I was planning on using more shorter motors then I would drill multiple mounting holes which would not be a problem, and do away with the adapters.

4-40 self clenching nuts epoxied inside


Had to make an adapter to go from Loki to Aeropack thread sizes


Flat head machine screws countersunk to sit flush and use a T10 head

Ahhhhhhh, That's a nice setup to be able to remove the internal retainer that I will have to keep in mind for the future. I believe it will be most helpful if one is running a retainer that has a screweye and they want to be able to remove it to replace a worn
shockcord. Darn! I have two 38mm projects I epoxied the bulkhead in and took pains to protect the shockcords. Making it a screw-in would be better for cord maintanence. But............ Drilling and tapping won't necessarily make it interchangeable unless
a means could be had to drill holes in a new airframe that would "exactly match" the pre-drilled holes in the Aero-pack. Kurt
 
Ahhhhhhh, That's a nice setup to be able to remove the internal retainer that I will have to keep in mind for the future. I believe it will be most helpful if one is running a retainer that has a screweye and they want to be able to remove it to replace a worn shockcord. Darn! I have two 38mm projects I epoxied the bulkhead in and took pains to protect the shockcords. Making it a screw-in would be better for cord maintanence. But............ Drilling and tapping won't necessarily make it interchangeable unlessa means could be had to drill holes in a new airframe that would "exactly match" the pre-drilled holes in the Aero-pack. Kurt

I would love to take credit for it, but like most of my ingenious rocketry ideas, I simply gleaned it off another TRF member. Actually Teddy Chernok (AKA onebadhawk) came up with it...he has his moments :)

As for lining it up, yes most definitely you have to be accurate. I made a template that I used to drill the airframe and transferred those marks to the retainer. I have gotten into the habit (mostly from lack of confidence in my measure once cut twice approach) to drill one hole at a time, check and adjust. Also to keep things completely lined up I put a witness mark on the retainer as well as inside the aft end of the airframe.

If you're going to be at NYPOWER or LDRS just drop by and I will pull it apart so you can see how easily it comes apart, and more importantly how well it lines up and secure it is.
 
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Aero Pack Minimum Diameter Motor Retainers are designed to be used with the motors thrust ring (aft-closure or snap-ring) against the end of the airframe so that most of the thrust load is taken there. We have seen several rockets flown where there was no thrust ring and the retainer and forward closure held the load, however, Aero Pack cannot endorse or guarantee this as we cannot control the rockets construction and there are several types of forward closure motor configurations possible, not all of which are safe for that type of load. Therefore Aero Pack only recommends using the retainer to hold the motor from coming out and that the end of the airframe take the prime transfer of thrust.

As for location of the retainer; as was already stated above in this thread it is best to mount the retainer for the longest motor ever planned for the rocket. If a shorter motor is flown just use an extension, either home made from a hardware store coupler and threaded rod, or by using one of our lighter aluminum and stainless extensions or extensions sets.

Regards,

Bob
Aero Pack
 
I also just used the 54mm MD Aeropack retainer in a new 54mm MD rocket.

As Kyle said you can just drill, tap and use some machine screws. I epoxied some self clenching nuts onto the inside the the Aeropack and have had it in and out of the rocket no less than a few dozen times at this stage. I sized it for the biggest case I plan to use, a Loki 54\2800 with extended bulkhead. But I can put anything in it with some simple adapters or even threaded rod; I am launching it this weekend at NYPOWER on a 1 grain CTI 54mm case. If I was planning on using more shorter motors then I would drill multiple mounting holes which would not be a problem, and do away with the adapters.

4-40 self clenching nuts epoxied inside

View attachment 263723

Had to make an adapter to go from Loki to Aeropack thread sizes

View attachment 263724

Flat head machine screws countersunk to sit flush and use a T10 head

View attachment 263722

Michael,

If your airframe goes all the way from the Aeropack down over the top 6-8 inches of the motor case (or the complete motor case) I do not see this to be a problem. The aerodynamic forces on the airframe would be distributed to the motor case just like a coupler tube would see. Because of the fact that your Aeropack retainer is removable, you won't have to worry about getting the threads on the bulkhead stuck in the retainer and having the bulkhead spin inside the case. The airframe will hold the motor centered, and as long as the Aeropack adapter is mounted on the center line of the case and the entire assembly slides smoothly inside the airframe, thrusting the motor against the retainer should not cause any problem what so ever in my opinion.

The only weak point (if any) I can see in this type of design would be the screws holding the airframe to the retainer, or perhaps the airframe material or retainer itself around where the screws are. I honestly don't think that you'd have a problem, but there's one way to find out. Mount the retainer in the airframe, put a large wooden dowel up the back end, stand it all upright and balance yourself on top. That last part's the hard part. ;-) If you can still use the motors thrust ring, that would be the safest approach, but it will stick out into the air stream a bit.

Those screws might be your ultimate thrust retention point I think. If you have enough screws that are strong enough to hold the expected G forces X airframe weight, then you should be good to go. Let me know if you need any help in figuring that out. Nice work btw. This is very similar to what I am planning for Airfest this year, but I'll be using the Loki Lock Collar in place of the Aeropack retainer to hold the motor to the airframe. Also check out the tail cone below. There's still a few ways I can do that, not sure which one just yet, but I'd like to remove the motor cases thrust ring for a more flush design since even the low profile thrust rings still have a bit larger OD than the airframes out there.

However if the retainer were to be mounted permanently, what you need is the bulkhead Lock Collar I am trying to work on. Otherwise the threads could get locked and when you go to unscrew the motor from the adapter and the bulkhead could spin inside the case, since it's "floating". CTI forward bulkheads are floating as well, but they are under compression which keeps them from spinning.

What I am missing on the bulkhead lock collar pictured below are the internal threads that will screw onto the 54mm Extended Bulkhead. The bottom .200" on the ID are not threaded so that when the set screws dig into the threads, those threads won't be engaged on the bulkhead. You'd screw down the collar so it is tight on the motor case and then tighten up the set screws so it doesn't move. This will hold the bulkhead firmly in place so that it does not spin inside the case. At least that's the plan. One of it's purposes was so the motors using the extended bulkhead would work with the Aeropack MD retainer.

If that works as planned, the next step is to drill and tap holes in the top of the lock collar to act as the rear bulkplate of an electronics bay. You'd screw in your all-thread into these holes and mount a bulkplate at the top end of the bay. The troublesome thing here is, FG coupler tube that is centerless ground like most all of them are, doesn't hold a good tolerance on the wall thickness. What you end up with is a lip sticking out on the thick wall side and a flush fit on the other. The only fix I can see right now is to have a sloppy fit so the coupler tube can be properly centered. This may not even be a problem though because most tubing is 2.150" ID and the motor cases (Loki) are 2.127"OD so there's some amount of play right there which should compensate and equal things out.

blackjack2564 said:
Depends on pressure & thrust. Some small motors & you can get aways with it.

Jim, every 54/4000 and 76/12000 I have tested has put the full thrust load of the motor directly on the load cell through the forward closure. That is how I have always done all my testing. As long as aerodynamic forces are not applied directly to a forward closure itself, pushing on the closure in this manner should never be a problem in my opinion. Do the math and it'll tell you the same thing. Looking at the photos I posted, if you were to attach the airframe directly to the forward closure assembly and the airframe was not sleeved down the top end of the motor case, all bending or flexing at the CP would put the force directly on the closure retention, something it was never designed for, unless perhaps you have a bolted case MD rocket like you'd see at BALLS. I had to cobble some scrap parts together and this was all I had. :-(

Note- the CTI P-8000 is designed to mount from the forward closure, albeit a composite case.
 

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I also just used the 54mm MD Aeropack retainer in a new 54mm MD rocket.

As Kyle said you can just drill, tap and use some machine screws. I epoxied some self clenching nuts onto the inside the the Aeropack and have had it in and out of the rocket no less than a few dozen times at this stage.

That's a really neat idea, and makes accessing the shock cord attachment point easy as well. A question though, what trick do you use to determine the right position in the airframe to drill the holes so that they line up with the ones you made on the retainer? There must be some technique for this that I just don't know, as I clearly demonstrated by my attempt to line up the single hole in APE's 38mm nose cone altimeter bay piece, I missed by about half the #4 screw diameter, so now I'm forced to turn the hole into more of a slot to actually get it to line up. I'd hate to have to do that with a motor retainer and a hole on the outside of the airframe as opposed to this one that is only on the NC shoulder, so not visible and no impact to the aerodynamics.

I'm in a bind with the Go Devil 38 I'm building, as the 38mm MD retainer and my 6GXL casing leaves a bit over 6" at the top for the apogee recovery and avionics bay coupler. If I go drogueless that wouldn't be a problem, but fitting any drogue in there (even a streamer) looks pretty challenging. The other thing I've considered is positioning the retainer for the 6G instead of the 6GXL (which gives up to 3.6" more space) and inserting an extra piece of airframe between the bottom of the rocket and the motor closure ring when using the 6GXL. This of course moves the Cg back since it effectively moves the fins forward, I think I have enough weight in my electronics that it will still be stable, but I'd want to get everything else finished to be sure before sticking the MD in place "forever". Your suggestion would solve the forever part, and I could have a position for 6G and 6GXL.

Another question is if you set the retainer in a lower position, then you're left with some significant airframe holes above it, I'd be afraid of the BP not being able to build up enough pressure to eject the laundry. Do you plug these holes somehow when using a smaller motor? Or just use more BP, or...?

Sadly I think the right answer for me is I should have recognized this issue before gluing the fins on, and ordered a lower airframe that was a few inches longer. Or just forget about flying 6GXLs in this rocket. But I already have the case, I'd hate to not be able to use it! :)
 
This has been an interesting thread and relevant to a MD design I'm working on. I've been batting an idea around that I would love to get some opinion on regarding a retainer/shock cord mount. This design assumes the following:

1. Using a motor casing that has a tapped forward closure and an aft thrust ring.
2. Immediately above the motor is a recovery bay and a shock cord mount is needed.

My idea is to use what could perhaps be called a floating motor mount. In consists of a bulkhead with an eye-bolt through it as shown in figure A. An Aeropack retainer could probably be used here as well. It is not glued or attached to the airframe in any way. Inside of the airframe, figure B (not to scale) there is a piece of coupler, figure C, or perhaps a centering ring that is epoxied in place. The idea is that you attach the shock cord to the eye-bolt and drop the retainer into the forward end of the airframe. The motor casing, figure D (also not to scale), goes in the aft end and its forward closure is screwed on to the end of the bolt until everything is "sandwiched" together.

I think that this would work okay from a motor retention point of view, but my concern is the shock cord. The entire force applied to the shock cord would be translated through the motor casing to the thrust ring. Would this be a problem?

The motivation for the idea is to make the shock cord mount accessible to easily attach and remove the cord, but without having to use the external screws to secure the retainer in place as Kyle and mpitfield described above. This design does not, however, support changing the placement of the retainer as theirs does.

diagram.jpg


Any opinions as to the soundness of this idea? Has anyone done something like this before?

Thanks

Steve
 
That's a really neat idea, and makes accessing the shock cord attachment point easy as well. A question though, what trick do you use to determine the right position in the airframe to drill the holes so that they line up with the ones you made on the retainer? There must be some technique for this that I just don't know, as I clearly demonstrated by my attempt to line up the single hole in APE's 38mm nose cone altimeter bay piece, I missed by about half the #4 screw diameter, so now I'm forced to turn the hole into more of a slot to actually get it to line up. I'd hate to have to do that with a motor retainer and a hole on the outside of the airframe as opposed to this one that is only on the NC shoulder, so not visible and no impact to the aerodynamics.

When I drilled the holes I made sure that the maximum motor of choice, in my case a Loki 54/2800 with extd. bulkhead, would work with my recovery gear. If not then you need to go back to the preverbial drawing board.

Once I was comfortable with the motor I simly assembled the motor and laid it beside the airframe, marking where the holes should be and transferred that to some masking tape on the airframe. Originally I thought I would tap and screw right into the retainer, however the wall of the retainer is pretty thin and there was not much to grab onto, so I opted to use a self clenching nut by first taking my dremmel to rough up the inside of the Aeropack and then epoxy the 4-40 self clenching nut.

You can drill the Aeropack or the airframe first, however whichever one you drill first I would only drill one hole in the other, then temporarily screw it in and make sure the next hole is going to line up. If you drilled the airframe then you could just drill right through that hole into the Aeropack so long as the Aeropack is temporarily screwed in with the first screw and you are confident of it's placing.

I'm in a bind with the Go Devil 38 I'm building, as the 38mm MD retainer and my 6GXL casing leaves a bit over 6" at the top for the apogee recovery and avionics bay coupler. If I go drogueless that wouldn't be a problem, but fitting any drogue in there (even a streamer) looks pretty challenging. The other thing I've considered is positioning the retainer for the 6G instead of the 6GXL (which gives up to 3.6" more space) and inserting an extra piece of airframe between the bottom of the rocket and the motor closure ring when using the 6GXL. This of course moves the Cg back since it effectively moves the fins forward, I think I have enough weight in my electronics that it will still be stable, but I'd want to get everything else finished to be sure before sticking the MD in place "forever". Your suggestion would solve the forever part, and I could have a position for 6G and 6GXL.

One thing I did on another build, my GT PK3, was to get a longer coupler for teh AV bay and move the aft bulkhead up into the AV bay, effectively buying me enough real estate to use a much longer motor. If you are close you could do the same thing withing reason. In my case I only had to move it 2".

Another question is if you set the retainer in a lower position, then you're left with some significant airframe holes above it, I'd be afraid of the BP not being able to build up enough pressure to eject the laundry. Do you plug these holes somehow when using a smaller motor? Or just use more BP, or...?

Sadly I think the right answer for me is I should have recognized this issue before gluing the fins on, and ordered a lower airframe that was a few inches longer. Or just forget about flying 6GXLs in this rocket. But I already have the case, I'd hate to not be able to use it! :)

On all of my rockets I not only have the sampling ports drilled into the AV bay for the barometric altimeter, but I also have static ports drilled into the fore and aft payload bays to relieve the pressure differential and mitigate premature separation. I know it seems counter intuitive to drill holes which is undoubtedly going to relieve some pressure which is needed to separate the rocket, however it works.

I am very deliberate about the size of holes I drill for my static ports as it's not just a random sized hole and I would add that you need to ground test to make sure you get it right. Possibly someone who is more knowledgeable on this subject can pop in.

To be clear this strategy does not preclude shear pins. I just stated using them and have done quite a lot of testing which has not resulted in a single failure to shear the pins due to the gases escaping out the static holes.

My guess is that the BP expands at a much faster rate than the holes can equalize and although some gas likely escapes, it does not do it quick enough to reduce the pressure build up...just a guess on that one.
 
Your wrong........& your right.........& you were lucky. There are almost always exceptions to rules.
Depends on pressure & thrust. Some small motors & you can get aways with it.

Remember Rocket City Rednecks?
When they had 2-N-5800's in a project that had thrust on closures to bulkhead? It ended VERY bad. Enough thrust and your theory is toast.

That's the first one that comes to mind, I have seen others.:smile:

I just thought of another one:

Several years back at Airfest I witnessed a 2-stage where motor was used as coupler on sustainer to booster. [AMW 7600 case] Motor was M-something research.
Held in place by treaded rod in closure to bulk plate/coupler affair glued in.
Soon as sustainer lit it was Boom-Boom time. After post mortem it was obvious the closure was pushed back, crushing grains & liner. It was over before it started.

Guess when your old like me & been around long enough, you see just about everything.
But then, there is always the next surprise around the corner...LOl

Nothing you posted is conclusive evidence that force on a bulkhead will cause a motor to CATO. Think about how force is transferred from burning propellant inside of a chamber to the case and then subsequently to the rocket. Hint: there's drawings of this online with arrows.

Secondly, a post mortem of an over pressurized motor should be taken with a grain of salt. The depressurization process does a lot things that may seem to suggest something occurred, however it's not something that you can point to as the smoking gun.

I also wasn't lucky.
 
For a 38mm MD, tape and friction-fit should be just fine. The aluminum tape on the outside isn't a bad idea, either.

I have a rocket like that, I was thinking about using a couple of Estes LPR retainers epoxied to the outside of the fincan with the top tab just catching a small slit in the tube. In the end, I just decided to tape the motor in, no problem. You might want to take a little BP out of the well, though... the volume you need to pressurize is likely to be pretty small. The first time I flew it the AT DMS G80 motor ejected out, even though it was a really tight fit. Reducing the BP solved the problem, it flew really well on an AT DMS I280.
 
As I promised in my earlier post, below is an update on my launches from NYPOWER.

The Aeropack retainer held up well as far as retaining the motor, and both CTI I445 Vmax reloads performed nominally without any issues due to forces on the forward bulkhead. One thing I did notice is that the eye bolt for the attachment point on the recovery harness is now slightly bent after the launches, which I will replace. The positive point is that I can disassemble everything and inspect/replace as required, which is not usually an option.

View attachment 264000

The day did have it's moments though. On my first launch I put my AV bay in backwards :facepalm:. This resulted in my main popping at 3300 and a really loooooong walk. However I need the exercise, and the rocket was recovered without any issue. While walking back from recovering the second launch, which was also long due to much higher winds and an over sized chute, my nosecone tip which was hand tightened, fell off. Of course I did not notice this until I got back to the launch line. :bangpan:

Both issues were my error and lessons were learned.
 
As I promised in my earlier post, below is an update on my launches from NYPOWER.

The Aeropack retainer held up well as far as retaining the motor, and both CTI I445 Vmax reloads performed nominally without any issues due to forces on the forward bulkhead. One thing I did notice is that the eye bolt for the attachment point on the recovery harness is now slightly bent after the launches, which I will replace. The positive point is that I can disassemble everything and inspect/replace as required, which is not usually an option.

The day did have it's moments though. On my first launch I put my AV bay in backwards :facepalm:. This resulted in my main popping at 3300 and a really loooooong walk. However I need the exercise, and the rocket was recovered without any issue. While walking back from recovering the second launch, which was also long due to much higher winds and an over sized chute, my nosecone tip which was hand tightened, fell off. Of course I did not notice this until I got back to the launch line. :bangpan:

Both issues were my error and lessons were learned.

Weellllll...... You make me feel like a stupidhead:bangpan: I epoxied mine in a 38mm fiberglass project and I have the PEM nuts on hand!!!:facepalm: Plus I have the stuff to drill and tap! Oh well, will save that for the future. One lives and learns. I also epoxied one in on a cardboard LOC tubed project I don 't feel quite so bad about as the drill/tap/screw situation might not be was workable with a cardboard tube. Repeated removals might put wear and tear on the tube and not stand up as well with fiberglass. Heck with that rocket, it will be easier to rip it apart and recover the retainer if the rocket is irrepairably damaged.

Sooooo, you have a symmetrical Ebay? I have a story about a symmetrical ebay. I put a Beeline GPS tracker up forward in an extended ebay with the antenna through the forward bulkhead stented with a plastic tube so it wouldn't get crushed by the main recovery laundry. Idiot head :facepalm: here painted the rocket with metallic paint and didn't do an adequate range check. Launched rocket, one packet from 8000 feet then nothing. Luckily came down within sight and recovered. Now what to do? Since ebay was "symmetrical" was able to flip it around so the MAWD rides on top, put an SMA bulkhead mount for the antenna on the forward bulkhead that is now the "aft" bulkhead. The antenna faces aft and is now out in the "open" when the apogee charge fires. Avoids having to strip the paint off the rocket.

The bulkhead antenna mount sort of like this one: https://www.ebay.com/itm/SMA-female...755?pt=LH_DefaultDomain_0&hash=item587f18d0a3 has a stiff wire so the BLGPS can face forward so the G-Switch on this older unit functions properly. I lucked out on this remedy. Kurt
 
As a followup to my previous post.

I sent and email to Aeropack asking for the specs on the bent eye-bolt and to my surprise they simply asked for my address and shipped me one no charge. To me, that is the epitome of a quality vendor! :clap:
 
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