First High power build with PBL AMRAAM4, converting to CPR3000.

[tsmmiller]

I am posting this build primarily for the learning experience.
I’ve built and launch many a rocket in my younger years. All Estes. The Renegade was my favorite.
Since I’ve been lurking here starting in 2014 I’ve cloned the Renegade and done a few mid power builds.
This is my first foray into the realm of high power.
The AMRAAM4 was purchased via the yard sale from a “well known member.” I’ll let him chime in if he so desires.
I’ve also wanted to go with dual deploy, so this seemed like a good way to start. The pricing was right.
Once the kit arrived I checked it over and promptly ordered the CPR3000 from PML.
The CPR kit arrived at my door this morning after being mistakenly delivered to a neighbor down the road.
Opened and unpacked, inventory of the ‘4 kit and the CPR3000.
This looks like it is going to be fun!
The first thing I’ve noticed is slight difference in the retrofit instructions and what you would normally receive with the factory CPR kit. The retrofit instructions indicate to cut the lower airframe at 16.5 inches, making two sections of 16 and 16.5 inches. The parts list that would come from PML shows that the lower airframe is two sections of pre-slotted 12 inches and 20.5 inches. This will be the cut I make.
Other than this minor deviation from my received instructions I will build this as if it were from factory CPR and all stock, since this is a learning kit for me, and perhaps what I will use to cert for Level one, sometime this year if I am lucky enough!
The first image is of the ‘4 kit. The second of the CPR3000 components and lastly all of it together.
Inventory on the floor since my work bench is buried in the garage for the moment.

 

[Steve Shannon]

I did exactly this after lawn darting a rocket due to a motor deployment not firing when I thought it should. I bought four or five cpr3k retro fit kits and built them into my fleet of PML rockets. They worked well. The only thing I would change is to replace the cpr3k tube with an equivalent sized G10 tube. Otherwise, if the phenolic tube shears off right where the aluminum coupler abuts the centering ring the altimeter becomes a structural component.

 

[heada]

Great kit, I did my L1 on it. A few things I'd do different looking back
1) ditch the brass lunch lugs and go with rail buttons
2) ditch the kwik-switch motor mount system and go with just the 54mm motor mount and an Aeropack motor retainer. You can use the Aeropack adapters to drop it down from 54mm to 38mm if needed
3) plan the e-bay for the electronics you'll be using. Its a good, if unique, setup but it was originally designed for a specific altimeter which isn't available any more
4) play close attention to the pistons. The QT based body tubes are more sensitive to changes in temp so the piston fits will change between summer and winter.
5) the TN that connects everything gets toasted between the e-bay and both pistons. Either plan for the possibility to replace it in the future or protect it with a Kevlar sleeve.

Good luck and have fun

 

[tsmmiller]

Great kit, I did my L1 on it. A few things I'd do different looking back
1) ditch the brass lunch lugs and go with rail buttons
2) ditch the kwik-switch motor mount system and go with just the 54mm motor mount and an Aeropack motor retainer. You can use the Aeropack adapters to drop it down from 54mm to 38mm if needed
3) plan the e-bay for the electronics you'll be using. Its a good, if unique, setup but it was originally designed for a specific altimeter which isn't available any more
4) play close attention to the pistons. The QT based body tubes are more sensitive to changes in temp so the piston fits will change between summer and winter.
5) the TN that connects everything gets toasted between the e-bay and both pistons. Either plan for the possibility to replace it in the future or protect it with a Kevlar sleeve.

Good luck and have fun

Thanks, all good points that I’ve thought of as well.
I had already decided to ditch the brass lugs and am going to install the Acme Conformal rail buttons fromGiant Leap Rocketry.
I checked out the Aeropack retainers.....I like it. I’ll have to do some more looking there.
Altimeter.....not real sure where I am going down that line, so many I like, but I don’t want to break the bank either so I’ll keep that to a less expensive but dependable item.
TN toasted. Thanks for the warning there. Kevlar sleeving sounds like an easy fix, or just replace it with Kevlar from the get go. I just looked at harnesses for OneBadHawk. It would mean changing the way the chords are attached, easy enough to remedy in order to use the Kevlar.

 

[heada]

If you replace the TN with Kevlar, you'll need to use a longer section than you would if using TN. The nylon stretches whereas the Kevlar doesn't stretch nearly as much. I don't have any exact numbers on the differences but I normally go with 1.5x the length.

 

[manixFan]

A lot of good advice so far. When I got started I built a bunch of PML kits using the CPR system. I have a Nimbus that I built about 15 years ago that I still fly routinely that has the same CPR system you have. I agree to ditch the Kwik-Switch and just use a regular motor mount. But even after 15 years the tubular nylon is fine - toasty yes, but still in very serviceable condition. But of course nothing wrong with making it replaceable or just using a sleeve. The conformal rail guides are a bit problematic with Quantum tubing. I used them on a number of PML kits but if the surface is not prepped really well they can pop-off pretty easily if you apply much side torque on the bottom button during loading. I used JB Weld finally and that seems to work ok, but I now prefer regular buttons. Steve's comment about using a G10 tube in place of the phenolic tube for the CPR part is one I learned the hard way - I had one break just above the centering ring. In addition to using G10, I also build up a fillet along the CR and the aluminum piece to spread out the stresses.

I have had two of the AMRAAM kits from PML that used Quantum tubing, the great thing is they are really easy to paint since it's already gray and it's such a smooth surface. But you do need to rough it up pretty good anywhere you are going to bond it using epoxy.

The PML kits are a great way to get started in HPR since they have good instructions and are so easy to finish. Enjoy your build.


Tony

 

[tsmmiller]

Steve, Tony. Can you please clarify for me what part I should replace with G10.
If it is the mounting tube that the CPR3K is glued to and is also the avionics bay, it looks like PML has made that switch already. This would be the two standing next to the blue anodized sleeve and threaded sleeve.
My mind has also been made up. Ditch the Knick-Switch in favor of the Aeropack and adapters.
I’ve not even started and am already deviating from the plans.....but that is OK. This is exactly why I decided to start a thread on this.
I’ve learned lots from reading over the years, but now to put it to work.
I appreciate the advice and knowledge and thank you to all who have contributed so quickly!

 

[manixFan]

Yeah, they did make that switch to G10, I can see that in the photo. In the 'old days' that tube with the slot was just phenolic. The changes you are making are for the better, so that's a good thing. I build a couple of rockets using the Kwik-Switch and regretted it when I tried to use a longer motor. And since all other kits will use regular centering rings and motor mounts might as well get familiar with them now.

I should have pointed out that I use sleeves over the tubular nylon in my rockets that use large ejection charges that seem to be a lot harder on the TN than something like a gram or two. The nice thing about the PML way of using the TN is that it is very secure and yet easy to do.


Tony

 

[Steve Shannon]

Yeah, that’s the tube. Had PML just machined a shoulder onto the aluminum coupler that would epoxy into the centering ring it would have been even better but I’m glad to see they made that change.
I agree on the kwik switch too. First time I flew a K550 I had to use a dowel and hammer to break off the 54 mm Kwik Switch fitting.

 

[tsmmiller]

Not a whole lot of progress. Baby steps.
I glued the upper motor retainer on, moving it down .500 of an inch due to eliminating the Kwick Switch.
That allowed me to place a .375 fillet above and below the ring. This was allowed to cure overnight in my hot garage.
This afternoon I placed the 16 inch strap using a popsicle stick and several zip ties.
Probably overkill, but I wanted to ensure positive retention of the strap.
The next step is to start mounting to the fin section. Since this is a conversion I will need to cut my longer tube to get the two shorter tubes required. I measured and marked where that cut will be, now to decide how to cut it.
I am leaning to putting in my 11 inch coupler for rigidity and using a long hose clamp and a new #11 Xacto blade.
The next item is the 7 inch coupler, so I measured my mid point on that.
The parts list has (2) 7 inch couplers, the CPR3K kit came with one, the ‘4 came with an 11 inch coupler that I will trim down. The Instructions are showing a 7.5 coupler used. I would think in keeping things standard items were trimmed to be two of the same. Less inventory. When I make my trim I am going to split the difference and cut it to 7.250.
I’ve spent a good deal of time looking for 38mm hardware and the flanged 54 mm motor retainer. Seems most everyone is out of stock. I am also out of funds for a bit, so no matter. I still have lots of time before I need those particular items. I am also planning on increasing my parachute to a 60 inch.

 

[swatkat]

I literally JUST finished this same kit and made many of the modifications that others are recommending. I did actually ditch the piston eject system, opting to just go the traditional route with 2000# Kevlar to a 7/16th inch tubular nylon set up. I'm also moving to the 60" chute, even though the weight of the rocket came in fully completed at 77Oz. I just don't like the way those thin base fins are exposed. I did leave the Kwik Switch in, only because this one isn't a high flyer for me.

 

[tsmmiller]

On the way home today I stopped at my favorite hardware store and purchased two 4inch dryer duct clamps.
After a few afternoon chores I lined them up on the tube and spent a few minutes cutting them to length.
After honing the ends flat on my surface plate and a sheet of wet 400 paper they came out pretty good.
The only way to tell my cut from the factory cut....mine is smoother.
Not anticipating gluing tonight I just wanted to dry fit, see how everything lines up.
It seems I have a problem. Not a big one.
So this brings forth a question for those of you who have built this CPR3K.
Steps 4 and 5 are glueing the couple and the engine mount into the fin can.
This line of the instructions is where I am having issues.....
“Remember that the upper centering ring is actually going into the coupler tube.”
This upper centering ring is the FWD engine mount ring? If so.....there is my issue. my 54mm ring is for the ID of the airframe, not the coupler.
I think this may be due to me mixing kits parts. I did check all the rings and the only one I have set for coupler is this one.
If you confirm that this ring is going into the coupler, a few minutes sanding is in order.

 

[Steve Shannon]

What’s in that picture looks like the coupler tube and bulk plate for constructing the piston. If that’s what you’re asking about that bulk plate does indeed need to fit in the piston coupler tube. But your description talks about a centering ring. So before you start sanding or gluing, what are you talking about?
Or not the piston, but you’re building this using the zipperless design with the phenolic coupler protruding from the aft section. That’s right, that’s how the cpr3k conversion works. The bulk plate still needs to fit into the coupler.

 

[tsmmiller]

Thank you Steve, sometimes I even confuse myself.
No, this was not for the pistons, I have those all separated and the bulkheads inserted into them, not finished yet, just fit checked to make sure I had the right parts in the right place.
With that....yes, I will need to do a little bit of sanding to get that ring to fit.
In the end when the fin can is finished it will have the FWD engine mount ring as the middle engine mount ring and then the slotted bulkhead as the most fwd ring where the D ring attaches.

 

[tsmmiller]

Some days it takes me a little longer to get going, other days I wake up and it dawns on me, well duh?
I am converting this from the standard "4 to the CPR3K. I downloaded the build instructions and have been following them, as if this were a from factory kit.
The above 54mm centering ring is the one item different.
There is a conversion sheet that comes with the CPR3K kit, for the AMRAAM it instructs to cut the boost section at 16inches. Had I done that, I would not have to trim down the centering ring to go inside the coupler.
Now I wonder what other minor differences I am going to come across.

 

[Buckeye]

Great kit, I did my L1 on it. A few things I'd do different looking back
1) ditch the brass lunch lugs and go with rail buttons
2) ditch the kwik-switch motor mount system and go with just the 54mm motor mount and an Aeropack motor retainer. You can use the Aeropack adapters to drop it down from 54mm to 38mm if needed
3) plan the e-bay for the electronics you'll be using. Its a good, if unique, setup but it was originally designed for a specific altimeter which isn't available any more
4) play close attention to the pistons. The QT based body tubes are more sensitive to changes in temp so the piston fits will change between summer and winter.
5) the TN that connects everything gets toasted between the e-bay and both pistons. Either plan for the possibility to replace it in the future or protect it with a Kevlar sleeve.

Good luck and have fun

Well, if you need all these changes, why bother with a PML kit? These kits from PML are 25 year old technology and with limitations that no longer exist in other products. Am I missing something? I had an Ariel many years ago and looks like not much has changed. The only good thing about the plastic tubes is the ease of painting. However, painting is low priority for me.

Enjoy your build. If you stick around in HPR, there are lots of options to play with.

 

[Steve Shannon]

Some days it takes me a little longer to get going, other days I wake up and it dawns on me, well duh?
I am converting this from the standard "4 to the CPR3K. I downloaded the build instructions and have been following them, as if this were a from factory kit.
The above 54mm centering ring is the one item different.
There is a conversion sheet that comes with the CPR3K kit, for the AMRAAM it instructs to cut the boost section at 16inches. Had I done that, I would not have to trim down the centering ring to go inside the coupler.
Now I wonder what other minor differences I am going to come across.

Ahh. That makes sense.
I really like the PML kits. The techniques used in building them directly translate to anything you’re likely to do in HPR. Their instructions are clear but as you found it’s very important to read and follow the conversion instructions when using a conversion.
By not shortening the aft section you may discover that another section ends up quite short (unless the part that you were supposed to cut off the fin section body tube was intended to be discarded).

 

[Steve Shannon]

Well, if you need all these changes, why bother with a PML kit? These kits from PML are 25 year old technology and with limitations that no longer exist in other products. Am I missing something? I had an Ariel many years ago and looks like not much has changed. The only good thing about the plastic tubes is the ease of painting. However, painting is low priority for me.

Enjoy your build. If you stick around in HPR, there are lots of options to play with.

I agree with Aaron (Heada) that those are smart considerations. They are all easy to accomplish too and have very little to do with the actual kit. What makes PML kits a good way to learn are the clear instructions (at least when building according to the instructions) and completeness of the kit.

 

[heada]

Well, if you need all these changes, why bother with a PML kit? These kits from PML are 25 year old technology and with limitations that no longer exist in other products. Am I missing something? I had an Ariel many years ago and looks like not much has changed. The only good thing about the plastic tubes is the ease of painting. However, painting is low priority for me.

Enjoy your build. If you stick around in HPR, there are lots of options to play with.

If you really look at what I suggested, there were only 2 changes, rail buttons and motor retention and even those aren't required, only suggested. Everything else was a "plan for" or "pay attention to"

Rail buttons vs launch lugs (not lunch lugs like I originally typed...I don't want to eat a lug for lunch) is an on-going debate and brass launch lugs are still a valid option and can be used. At our club, we still lay out 1/2" rods next to our rails and they're used at each launch. Really its a change in $1.50 worth of parts.

Motor retention can be done with a t-nut, a screw and and washer. Again, less than $1.00 worth of parts. The Kwik-Switch is a good idea but implemented badly in my option. Few are the kits that include motor mount adapters between 29mm/38mm/54mm so it isn't something to dismiss out of hand.

PML kits are still good and valid. QT is not my choice of tubing material, I much rather prefer phenolic or paper, but that is pure preference. The instructions are very good and if you're just getting into HPR, they're great to ease you into the HPR way of thinking/building.

 

[manixFan]

I still have several PML kits I built when I first started flying HPR, including the fin can of my Sudden Rush, which was my L1/L2 bird, a Tiny Pterodactyl, a Nimbus, and a Little Lunar Express. They were built back in the very early 2000's (2001-2003) and all still fly to this day. The great thing about PML kits is they are easy to build due to the very good instructions. The Quantum tube, in spite of its limitations, finishes very nicely and avoids the pain of lots of sanding and filling fiberglass weave. And they have good motor recommendations making it easy to get started. I feel they allowed me to be successful in HPR with my very first flights and gave me enough knowledge and confidence to build more conventional kits that often came with no more instructions than a parts list.


Tony

 

[Steve Shannon]

I still have several PML kits I build when I first started flying HPR, including the fin can of my Sudden Rush, which was my L1/L2 bird, a Tiny Pterodactyl, a Nimbus, and a Little Lunar Express. They were built back in the very early 2000's (2001-2003) and all still fly to this day. The great thing about PML kits is they are easy to build due to the very good instructions. The Quantum tube, in spite of its limitations, finishes very nicely and avoids the pain of lots of sanding and filling fiberglass weave. And they have good motor recommendations making it easy to get started. I feel they allowed me to be successful in HPR with my very first flights and gave me enough knowledge and confidence to build more conventional kits that often came with no more instructions than a parts list.


Tony

Very well said!

 

[tsmmiller]

Thanks all!
As I’ve mentioned, this was to be a learning experience for me, and it is.
I chose this kit simply because the price was right. It was not my first choice.
Even this with the QT was not actually what I would have chosen. If I ordered this stock from PML I would go with the glass wrapped phenolic.
I really wanted the Madcow DX3 or the Level2 from Apogee. One of those or even both will come later.
I”ll build this, try to cert with it and go from there. It would be really cool if I could get it done by the Tri Cities launch in July. Not gonna happen. Too much other stuff happening. But maybe one of the later launches I will make.
The changes I am making I am doing because it does make sense to me. At first the Kwick switch seemed kind of cool, then looking at other motor retentions I decided to do away with it. As has been mentioned, even a couple of washers works, so why get overly complicated.
Launch lugs I have never liked. Doing away with those was a non issue that I had planned from the beginning.
Works going to take up most of my weekend, so I”ll not get much done for a few days.
Even with what I’ve done so far I have ideas of things I would/will do differently on the next build, and there will be one. That is a given, it just depends on what Mrs will allow me to get away with!
I think a new pair of Gucci shoes and I’ll be good to go for a while!

 

[tsmmiller]

] A little bit of progress in one afternoon while the house was kind of quiet.
Glued more centering rings for the av bay, building up the center section.
This also revealed that I will need to sand down two more rings that are to be mounted in the coupler.
I inserted the ring into the body tube, followed by a coupler, reached in to trace how much I will need to remove.
Not much, so a few minutes with each ring on the belt sander should do the trick.
This is a project that has to wait till Mrs. is not home. Even with the vacuum going wood dust migrates, so I often work out in the driveway for projects like this.
Once the rings are sanded to size I will continue with the piston straps.
I do have one question, with the CPR3K, PML “recommends” the foreword fins be glass re-I forced.
Is this necessary?
The next thing I am trying to decide on is mounting and holding fins during cure. I know there are as many ways as there are members on TRF, just trying to decide how I am going to do it.

 

[jd2cylman]

That's because the forward section now will land on it's bottom where your upper fins are. Just sand real good and use a healthy external fillet (since you can't do internals)...

 

[Steve Shannon]

Glassing the forward fins adds a little more weight up front, which is good because adding the forward fins shifts the center of pressure forward.
I have a PML BBX which has small canard fins. PML routed small shallow slots in the QT body tube for the canards, not all the way through, but even so the fins came right off the first time it landed. Glass reinforcement is probably what it would take to get them to be completely protected against landings. I just never put them back on.
As mentioned in the previous post preparation of the QT before applying epoxy is the biggest thing. From your pictures it looks like you’re doing a great job, but you might find that you’ll wish you had assembled the slotted centering rings to the tube with the straps in place. Opening up those slots after they’re epoxied to the 38 mm tube can be challenging. Don’t ask how I know. [emoji2955]

 

[tsmmiller]

Thanks Steve, I hadn't thought of the CP shifting fwd, and the landings did concern me to a point.
I think I'll go ahead and reinforce mine with the glass.
I won't ask how you know about opening the slots after being epoxied, but I can guess.
Foresight on my part saw the same issue and I made sure I had room before I glued the ring into place.
Keeping on my present track I should be able to sand my rings this weekend and by Monday start gluing assy's into the body tubes.
I am making progress, at least I am running out of parts.

 

[Steve Shannon]

I used to work on watches. Rockets, rocket motors, and watches share this: you never want to get them all put together only to find a leftover part. Some guy’s Citizen watch in eastern Montana is still missing a dust cover from when I learned that lesson.

 

[tsmmiller]

I got a great big chuckle out of that!
At least it is just a watch, a rocket and or rocket motor might be a little different issue.
I am employed in the aviation industry as a QA inspector, and spent many years prior to that chasing and working on helicopters. Spare parts are never a good thing after a reassembly and or build.
I will give one exception to that: Lego, Lego almost always tosses in a few extra pieces in each of their sets.

 

[tsmmiller]

It was such a beautiful day today my son wanted his bounce house set up. I couldn’t refuse.
After setting his house up and getting him set for a day of fun, I began mine.
I yarded the sander out to the far side of the back yard so I could monitor the activities on the bounce house and sand on my centering ring.
I began by fitting the motor mount into the fin can, and then slid in a coupler. Tracing a line with pencil gave me a good reference on how far to sand. A few moments and the ring slid nicely into the coupler.
While doing this I was thinking of instructions on sliding the coupler and motor tube together quickly in subsequent steps. I think I came up with a better plan.
I figured out how much my motor tube needed to stick out the back for the Aero Pack 54 mm retainer. I slid the coupler in and then the motor tube, marking where everything was going to fit. A quick disassembled and then prepped everything with a rough sanding and thorough cleaning. The forward centering ring sits approximately mid point of the fin can coupler. I applied my epoxy to the coupler and fed the motor mount into the coupler from the top. Doing this allowed me to create a nice fillet on the back side of the foreword motor centering ring.
I let this set for a couple of hours and then mounted the engine tube to the fin can and added the upper epoxy fillet.
Tomorrow will be prepping and getting the aft fins mounted.

 

[tsmmiller]

I’ve spent the morning sanding and prepping the aft fins. Roughing up the fillet areas with several good passes with 180, eliminating any shiny or smooth spots. I did of course wash them down with hot soapy water prior to sanding, and then again when done. Prior to adhesive application I’ll wipe them down with a tack cloth and IPA.
If I can swing it, I will have our “creation lab” cut me a fin guide from rigid foam downloaded from PayloadBay.
Looking for motor hardware, I’ve come up with a question.
Since I am new to high power and have had no interaction with those in high power I just don’t know and can’t find the answer.
Since I will be limited for a time to flying up to the 38mm engines I will need to adapt down from the 54 mm.
I will be using an Aeropack retainer, and adapters.
This brings up my question, Do I need to start with a 54mm casing and then adapt down to the 38 mm casing, in other words for my initial purchase I will need to buy both the 54mm and 38 mm hardware.
Wildman has a 38/600 special that includes the spacers although I would rather get the 38/720.