PML Matrix

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Jan 18, 2009
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I am putting together my very first "true" HPR the PML Matrix. Construction is actually pretty simple. My question is:

The instructions say to drill 3 equally spaced holes thru the body tube and the nose cone and secure with some screws. Why can't I just glue it in place? It does not give any explanation. I realize that drilling the hole in the bulkhead relieves the air pressure on certain flights, but I don't understand why the nose cone is not glued in. Thanx guys.

The method you described is what PML indeed recommends for mounting; there are several reasons for it that I can note. First, you almost never want to glue in your nosecone. It can be done but is more difficult as epoxy really doesn't stick well to either the plastic nosecone or Quantum tube without some effort. Moreover, in case there was a need to replace the nosecone, it could not easily be done in a glued position.

Also note that even though the screws are for retaining the nosecone, you could friction fit it. This would require the need to drill some "breather" holes in the chamber below to equalize pressure and prevent premature seperation.

The whole purpose of the removavle nosecone area though is to give you a "Payload" area, where you could carry insects, etc... or better yet, altimeters, cameras and more! I have flown mine several times though and have never used the bay; it remains screwed to the bodytube. I do see me using it for dual deploy though in the future if I wish...the possibilities are endless.

Good luck and don't forget to post some launch pics!!! :)

My guess would be for removablity for future use of payloads...until then you secure it with screws so it will not blow out at apogee. You could glue it or friction fit with masking tape...but I'm just guessing as I have done all three ways on different rockets based on what I set out to acheive.
You know, I never thought of the altimeters or cameras. Thanx guys, I'll stick to the instructions. Don't worry, I'll post pics, oh wait I've got to join NAR first to get the 38mm motors (assuming I pass my L1 flight).
You will absolutely love the way that rocket flies. I built one and I have flown it on H123W and H242T motors, flew great on both of them. I'd love to put it up on an I161W next. According to PML, it should hit about 2,600 feet on that motor.

It's tough as nails too. On the most recent flight, it landed on the road at our field. I was expecting major damage to the lower fins. Instead, it just scratched the paint on one of them.

As for delays, I used a short delay with the H123W and the chute deployed as the rocket went over the top.

I used the medium delay with the H242T due to the fast burn. I figured that it would coast longer.

Hope this helps

Good luck:)
As of yet I do not have my L1 cert. What would be a good 29mm motor to use for this kit. I have the 29/40 -120 RMS kit. Thanx.
Looking at the PML motor guide, i don't think there are any non L1 motors you can safely fly it on.. Probably about time to cert l! on it. :) The H123 only gets it to a little over 1000. I would not fly it on a g. You might get away with it, but I wouldn't.
Originally posted by Justin Horne
Looking at the PML motor guide, i don't think there are any non L1 motors you can safely fly it on.. Probably about time to cert l! on it. :) The H123 only gets it to a little over 1000. I would not fly it on a g. You might get away with it, but I wouldn't.

I agree

This is a heavy rocket, weighing in at roughly 3-3 1/2 lbs and that's built stock. If you added reinforcements, it may weigh even more than that. Even the max lift weight for a G80 is about 2 1/2- 3 lbs and I know the max lift for a G64-4W is only 44 ounces, that wouldn't be nearly enough thrust.

BTW, I flew mine on an H123W, I think it reached about 1,400 feet according to PML's reccommended motor/altitude chart.

What I reccommend is that you save it for your L1 cert as this is a fine rocket to do it with or if you really wanna see it fly, maybe you can team up with a buddy that is already certified.
Justin is right
Donaldsrockets is right also, save it for your L1:)
Yeah, he's right. The H123 does get to 1400 according to PML. I meant to say the H128 (29 mm) which gets it to 1167. And PML builds really light, so your altitude will probably be lower. I've seen one fly on an I284 ( I think) and it was great.
So you're saying I should save myself for the "first time". I feel like 16 all over again.
Originally posted by kelltym88
So you're saying I should save myself for the "first time". I feel like 16 all over again.

Not necessarily;)

I know the feeling. I think we've all been there at some point.

I suppose that just maybe you could fly it on a G80-4T but absolutely nothing less than that and if you do attempt it, I would only do it on a day when there is zero, zilch wind and point the rod straight up. If you did have a straight flight, you'd only get maybe 500-600 feet.

Techincally, we're just kinda trying to save you from a potential heartbreak and an even bigger dent to your wallet.;)

I'd be absolutely sick if my first ever HPR rocket crashed.
That, or have someone who is L1 fly it, just to make sure that the rocket is strong and able to take the motor (which im sure it is) . At the least youll get to see it fly on a nice sized motor, plus youll get an early look at what to do for an L1. That, or just cert L1 on it the first time. Nothing wrong with that. :)
Originally posted by Donaldsrockets

I'd be absolutely sick if my first ever HPR rocket crashed.

Yeah, I have the PML Bullpuppy kit (my first HPR, a gift from my GF for my birthday) and decided to give it a test flight on an F-25 (which is not a recommended motor by the way). Boy was that stupid! Not only did the rocket get about 25 feet above the ground, but I also wound up having the tailcone separate from the main body tube and one of the fins popped off. As spectacular as the flight was, no serious damage occured (thankfully). I was kicking myself for the next couple of weeks though.

Took it out to Lucerne and flew it on a G-80 a few weeks after the mishap. Gave it a decent flight, about 400 feet or so. I am going to attempt to level 1 in august, but I just have to make sure my finances are in order.

I would have a hard time flying it on anything but it was said, my Matrix is heavy, 4lbs or so. The hardest part would be finding a very short delay so as to prevent core sampling.

I think I'll just have to wait. I'll have to scrounge up some $$$, join NAR and get certified L1. That shouldn't be too hard, the construction of that kit is pretty simple. Maybe I'll even get a wild hair and if I have a successful L1 flight, I'll cert L2 on the same day. Now I need to start studying.
I know you mentioned wanting to use a 29mm motor for your cert flight but I'd ask you to consider the Pro38 2-grain H153. One of those will put the Matrix up around 1500'. A guy in my club recently certed L1 with that rocket-motor combo. He made it look easy!

Good luck :)
I agree with the Pro38 recommendation.
I got my L1 cert on a Pro38 2 grain H143 Smokey Sam in a PML Tethys. Easy as heck. Either the H153 or the H143SS are as easy as it gets. I'll repeat some advice on cert flights from the guys in my group. "KISS"
Pro38 is more "simple" than Aerotech. An hour after my cert flight I flew again on an AT H238T (29/180). Then I flew on an I200W (29/360). I like the AT stuff better. It's more fun to build the motors, but keep things as simple as possible for the cert.
This is why I was planning on a lighter rocket for my first HPR, such as the PML Phobos or X-calibur...that way I could test fly it on a G before trying for the L1 cert, and also be able to still fly it at the local low-power field (which limits rockets to a singel G in impulse).
Just to reiterate, I wasn't planning on certifying L1 w/a 29mm motor. I don't have my L1 yet and wanted to fly it on a 29mm because I can get those. But after hearing everyone's suggestions, I'm going to wait until I certify and fly it on an H123.
Originally posted by NewEntity1
This is why I was planning on a lighter rocket for my first HPR, such as the PML Phobos or X-calibur...that way I could test fly it on a G before trying for the L1 cert, and also be able to still fly it at the local low-power field (which limits rockets to a singel G in impulse).

That's exactly what I did but if I had to do it all over again...I might have done it differently. First off, I certed L1 with the Phobos. It's a great rocket that flies well on G35 & G64s. When I certed though, I used a Pro38 H153. BIG difference as it easily broke 3000'. :eek: With that rocket-motor combination, you can forget the old "go slow 'n' low" mantra that anyone attempting a certification should follow. I certified successfully but in hindsight I kinda wished I would've used something to keep it lower...either a different rocket (with a larger diameter) or a lower impulse motor (like an AT 29/180 w/ H128). Make sure that the person(s) certifying your flight don't have a problem with you going that high.

Just my experiences...
I started with the same plan. Get a rocket that I could "test" on a G and then go for my L1 flight.
Well by the time I was done following everyone's recommendations on reinforcement.....
Put in a large wall anchor in the nose to reinforce the nosecone attach point with a 1/4" forged eyebolt. Reinforce the hell out of the fin can. Large fillets all around. Nomex on the piston strap. Throwing out the 12' shock that PML supplies and replacing it w/ 25' of tubular. 1000 lb swivel on the chute. Quick Links everywhere as opposed to tying and gluing the shock so you cannot remove it. Adding both rail guides and the launch lugs so you can use either depending on what is available when you go to launch. Bolting in the piston strap to the piston to reinforce the epoxy joint. Etc, Etc....
I ended up with a rocket that is 25 ounces over the PML weight. It will never fly on a G. I only got about 900 feet out of the Pro38 2 Grain. But I am happy I did it all. It was low and slow for sure. I feel my rocket is very strong. On the I200W flight it ended up in a tree. We got it out by yanking it out by the shock through a ton of very gnarly branches and bramble. I only got paint road rash.
So - build it strong - do your homework - ask questions - double/triple check everything - fly it for your cert.
Good luck.
either a different rocket (with a larger diameter) or a lower impulse motor (like an AT 29/180 w/ H128).

Dr. Rocket 29/180mm motor with an AT H128 load is exactly what I have in mind ;)

Quick additional note:
I'm probably going try to get the phenolic version of the rocket instead of the quantum tube, and apply 2 layers of 2 oz cloth. This means my rocket is liable to be slightly over the PML list weight as well. Between that, using an H128, and launching in the middle of a huge dry lake, I don't think height will be too big of an issue. :)

The maiden flight (planned for a G75j) is more likely to be a problem altitude-wise, because that launch may well be at the local small field (SCRA #430 launch at Santa Fe Dam). There, even moderately high flights are in danger of rocket-eating trees, cars, and taking a bath in the local reservoir. :eek:
Here's an update and a couple more questions. First off I have joined NAR, yeah. I have been working on my Matrix , in fact I'm just at the point now of painting and finishing . I plan on certing L1 at ROCStock in Nov. out at Lucerne. That also happens to be the TDD. Should be a fun day/weekend. Anyway, the questions:

1- I have a friend who has offered to let me use his Cessoroni casings. What motor is recommended?

2- I have heard of the problems with the piston sticking upon ejection, how about spraying that area with silicone before launch? I don't beleive it is flammable. Anyone tried this before?
Look forward to seeing you at ROCStock... it's gonna be my first launch since August with ROC... I miss everyone! (I'll be the guy with the 4" Arcas and L850W motor...)

Knowing the recovery area we have to work with, I'd go with either a 3- or 4-grain I motor. Both sim out as stable, and with a loaded weight of 4.5 lbs in Rocksim, you get about 2500 with the 3-grain and about 3500 with the 4-grain.

I've never used the pistons, so I couldn't give you too much advice on using them, but from what I've heard, make sure that the piston slides 100% freely (sand sand sand!) and wipe out the rocket after every flight to prevent it from getting stuck with gunk. I'm thinking of building a piston rocket sometime soon to see if I like it or not...

Should be a cool flight, I'm looking forwards to it!
Use the 2-grain Pro38 H153 for your cert flight. It'll stay under 1500'. Go crazy with the 3- & 4-grain motors after you're successful :)

All you need to do with the piston is just sand it until it fits so loosely that when you turn the rocket upside-down, it falls out. Follow the PML instructions explicitly.

Enjoy & HTH,
I agree - SAND, SAND, SAND!!!
I agree - Pro38 2 grain H153.

It should darn near drop through the rocket w/o any force. Check it again on launch day. Temperature really changes the diameter of Quantum. Make sure you bring more sandpaper to the field - you will probably be sanding the piston again there.
I learned from my first PML rocket how to handle the second. After you glue the piston plate into the piston, chuck it up in a cordless drill, support the drill and tape down the trigger. Now work that sandpaper over the rotating piston before you glue in the strap. (My method of a cheap lathe.) In other words - if your hands aren't tired and cramped and you think you have sanded your piston enough - you probably haven't.....
Do not sand the ID of the tube that the piston rides in. It will build up residue much quicker if you do.

I would not spray silicone. It is wet and will get nasty with the crap left behind from the ejection charge going off. Baby powder/Talc is what PML recommends on their FAQ section of their website.

After each flight wipe out the inside of the tube with damp papertowels or baby wipes or whatever and let it dry. You should probably have some fine sandpaper with you too (320 grit?) to lightly sand the piston after each flight just to get it clean from the residue.

My piston Tethys has 8 flights now. L1 & L2 flights included. No problems to date.
Good Luck.
I heard that if you put the quantum tube in the freezer for a little while, then sand the piston to fit the really cold tube, you will never have fitting problems.

Quantum is good stuff, don't get me wrong. But using pistons with it is kind of asking for trouble due to the fluctuations in size. Also, it's hard to glue to. If I were to buy a PML kit I think I would buy the phenolic version and give it a layer of glass.
Well too late for that it's already put together. But, since I live in Cal. the weather doesn't tend to flucuate as much out here. I will keep all of your advice in mind and check it regularly, and sand as needed. I will keep you posted....

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