So, maybe I'll try a three-stager

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Yeah I figured that's what the window was for, I could see how not having one could create a the opportunity for an unwanted scenario.

Question if you had a narrow firing time window of .5 seconds and a long igniter firing time of 1 second, could one setting cancel out/limit the other? That's the only interference I could see with using time windows.

-Kip
 
Yeah I figured that's what the window was for, I could see how not having one could create a the opportunity for an unwanted scenario.

Question if you had a narrow firing time window of .5 seconds and a long igniter firing time of 1 second, could one setting cancel out/limit the other? That's the only interference I could see with using time windows.

-Kip

If there was a situation where the igniter actually needed a longer firing time, then cutting it short could be a problem. It won't be an issue with ematches, though, as long as there is some amount of time in the window.

Jim
 
Me again...

Many of you know that I like to apply multiple layers of the Cotronics/Duralco 4525 for leading edge heat resistance. I just completed this for the second and third stages (recoating the third stage), and I think it turned out very well. Applying this epoxy is a pain because it isn't very user-friendly, particularly when you add some milled glass. However, I think I found a process that makes this relatively easy. I'll post details in the "Techniques" section.

Jim

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My very strong preference is not to use head end ignition - at least not with my current electronics setup. One procedure that I use when prepping the rocket is to do an "all-up" test of the electronics. Basically, everything is turned on, just as it would be on the pad, except that the igniter is not in the motor. If the test is successful, you turn everything off, put the rocket on the rail, and proceed with the launch. This is my last line of defense against a motor lighting prematurely. Since you can't remove the igniter with head end ignition, it is not possible to do the all up test. At some point, I may change my mind with suitable remote switching, but I'm not there yet, and carbon rockets don't help.

Jim

I have a circuit you need to take a look at.
 
Me again...

Many of you know that I like to apply multiple layers of the Cotronics/Duralco 4525 for leading edge heat resistance. I just completed this for the second and third stages (recoating the third stage), and I think it turned out very well. Applying this epoxy is a pain because it isn't very user-friendly, particularly when you add some milled glass. However, I think I found a process that makes this relatively easy. I'll post details in the "Techniques" section.

Jim

Please do! I just finished two sets of fins and will be using JB weld to coat the leading edges. I switched because 4525 is expensive, has a short shelf life (crystallizes very quickly), and it doesn't come in small quantities. I threw 90% of what I bought for my last rocket away.
 
Please do! I just finished two sets of fins and will be using JB weld to coat the leading edges. I switched because 4525 is expensive, has a short shelf life (crystallizes very quickly), and it doesn't come in small quantities. I threw 90% of what I bought for my last rocket away.

I've never dealt with Cotronics, but I have had epoxy crystallize before. I've placed the epoxy container into direct sunlight or hot water for a while and the crystals dissolved, leaving me with usable epoxy. You might try that. If you do, please let us know if it worked for Cotronics.


Steve Shannon
 
Please do! I just finished two sets of fins and will be using JB weld to coat the leading edges. I switched because 4525 is expensive, has a short shelf life (crystallizes very quickly), and it doesn't come in small quantities. I threw 90% of what I bought for my last rocket away.

X2 Jim, I have a T2T layup that I am just completing on a new build. It is not a build that requires it so it is a good place to test a your new technique. I was going to use some Proline 4500.
 
I've never dealt with Cotronics, but I have had epoxy crystallize before. I've placed the epoxy container into direct sunlight or hot water for a while and the crystals dissolved, leaving me with usable epoxy. You might try that. If you do, please let us know if it worked for Cotronics.


Steve Shannon

I think it did more than crystallize. The hardener color changed from golden yellow to dark brown. Cotronics advertises a 6 month self life for 4525.

Unfortunately I tossed what I had so there's no way to run that test.
 
I think it did more than crystallize. The hardener color changed from golden yellow to dark brown. Cotronics advertises a 6 month self life for 4525.

Unfortunately I tossed what I had so there's no way to run that test.

Yeah, my Aeropoxy goes from medium red to dark red. I assume it's due to loss of some solvent leaving denser pigments behind. Eventually I'm sure I won't be able to reconstitute it.
Thanks for the reply.


Steve Shannon
 
I think it did more than crystallize. The hardener color changed from golden yellow to dark brown. Cotronics advertises a 6 month self life for 4525.

Unfortunately I tossed what I had so there's no way to run that test.

Yeah, it gets pretty gross after 6 months. I usually use most of a pint when I make a rocket. This time, I only needed to do these leading edges, so we'll hopefully use the remainder in the club so that it doesn't go to waste.

The application thread is posted.

Jim
 
I've never dealt with Cotronics, but I have had epoxy crystallize before. I've placed the epoxy container into direct sunlight or hot water for a while and the crystals dissolved, leaving me with usable epoxy. You might try that. If you do, please let us know if it worked for Cotronics.


Steve Shannon
System Three says that the resin can be put in a 120 degree water bath to dissolve any crystals. But the hardener will darken over time which should not affect performance. Hard to say if something like Cotronics can be handled the same way but sure worth a try.


Tony
 
System Three says that the resin can be put in a 120 degree water bath to dissolve any crystals. But the hardener will darken over time which should not affect performance. Hard to say if something like Cotronics can be handled the same way but sure worth a try.


Tony

Haha wait, just mildly curious, I thought you couldn't heat water past 100 degrees Celsius. You meant 120 degrees Fahrenheit right?
 
Yeah, it gets pretty gross after 6 months. I usually use most of a pint when I make a rocket. This time, I only needed to do these leading edges, so we'll hopefully use the remainder in the club so that it doesn't go to waste.

The application thread is posted.

Jim

I've used outdated Cotronics 4525B or IP for less aggressive projects after it gets past its shelf life with no issues. They make even higher heat resistant adhesives but one would have to have materials that can tolerate being baked in an oven and "stand"
the baking temperature. (Plus have a large enough oven to do the job!) The stuff does pretty decent fillets too but doesn't reflow with heat. Heat makes it setup faster. I'm a neophyte and my experience with chopped fiber is that it's a Max/Min problem
along with using an adhesive of the right viscosity to suspend the fibers. To thin an adhesive and fiber distribution stinks. The fibers just settle down into globs and likely dubious whether or not it adds any strength. With the right viscosity adhesive, the problem becomes too little, too many or just enough fiber. Too little fiber and it likely doesn't do squat to add strength. Probably doesn't weaken the native, inherent strength of the epoxy though. (So why bother?) :wink: Too much fiber and I think the fiber/bond will break more easily under stress, be prone to flutter and actually be weaker than the plain inherent epoxy without enough adhesive to "lock" the fibers in place. Getting it just right and know one has it "just right" is the issue I don't have the skill to do. Obviously the more skilled out there are pulling it off with success. Kurt
 
So, my next activity is to make the box to transport the project to the playa. This year, I'm going to make a box that completely contains the rocket. In past years, I didn't do that, and dust getting into the rocket was a problem. This year, with lots of joints and several sets of bearings, I'm going to try and minimize that problem. I have completed the supports and now it's time to build the box itself.

Jim

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So, the box is done. Although it is constructed from the worst wood I've ever purchased, I believe it will work. I know the box seems a little on the dull side, but with high altitude windows closing at noon, it is quite essential to be able to transport the rocket mostly assembled and free of dust.

Jim

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Looks good Jim.

I was just finishing cleaning my 3" Darkstar this evening and going over the damage before storage. One of the disadvantages of painted fiberglass over polished carbon fiber is the durability. In looking at the damage from URRF4, it is almost entirely from transport, not rail rash or the the expected war wounds suffered from the flight and subsequent landing and possible dragging from a persistent inflated chute.

This is not to say my carbon fiber rocket launched from the same launch did not suffer any scratches, but as you know carbon fiber scratches are relatively easy to repair.

Anyway I was already thinking about this topic when I saw your post. In my case I think I am going to try to pick up some used sleeping bags and use them for transport.
 
Plans to apply felt or something soft to the bearing points? Seems like the vibrations from the road trip could cause some serious abrasion to that wonderful finish.
 
If this rocketry thing doesn't work out, you'd make a passable coffin builder....
 
Plans to apply felt or something soft to the bearing points? Seems like the vibrations from the road trip could cause some serious abrasion to that wonderful finish.

There's one section of the air frame that is .... aaack!... painted. I'll put something there at least.

Jim
 
Watertight? Does it float?
May be a requirement.

M

There were numerous design objectives. I'm sure you can see the caulk in the picture to make it water tight, along with the handles for helicopter rigging, but the pics don't show the fittings for the pontoons or the outboard motor.

Jim
 
I've been doing a little testing of the Eggtimer WiFi switch. I have three of them assembled, and I would use two of them in the three-stager is possible (the second and third stage). They work quite well!

I've been doing some range testing, which is not done yet, but I suspect that when the entire rocket is assembled, the carbon tubes and motor closures will prevent adequate range for the WiFi signal. So, I'm just starting to think about Plans B, C and D. Plan B is something called a slot antenna. I have a buddy that knows something about antennas, and he thinks a slot in the air frame might be sufficient. Something to test. Plan C might involve the current trace antenna (see the pic). This trace if bare metal, so it's possible something could be soldered to it. I could arrange for a wire to exit the air frame, but I have idea if that would help. Plan D is for this group to propose. I'm pretty clueless when it comes to WiFi and antennas.

Jim

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The wifi module is available with an antenna connector. If you asked really nicely, Mr Eggtimer might be convinced to flash a couple for you. Not very helpful on built gear, but it might be helpful later.

Just soldering to the existing trace is likely to just detune it. You would need to disconnect it, then solder a coax in. And provide a properly tuned antenna for it. All of that can be a bit tricky with 2.4ghz.
 
The wifi module is available with an antenna connector. If you asked really nicely, Mr Eggtimer might be convinced to flash a couple for you. Not very helpful on built gear, but it might be helpful later.

Just soldering to the existing trace is likely to just detune it. You would need to disconnect it, then solder a coax in. And provide a properly tuned antenna for it. All of that can be a bit tricky with 2.4ghz.

Testing this morning went a little better. With everything assembled, I get a range of about 30 feet, which should be sufficient. The only problem is that when using two of them, you have to pair with the second one after turning on the first one, and you have to be within about 10 feet to do that. So, it might be necessary to climb a ladder just for the purpose of acquiring the second WiFi. I could probably live with that.

Sounds like the coax, external antenna could work, but as you say, likely tricky, and it doesn't fit my project very well. I'm going to try out the slot antenna concept and see if that works.

Jim
 
So, this afternoon, I played around with the slot antenna. This is just a 6.25 cm x 1/16" slot in the air frame. Nothing more than that. I'm told by folks that know much more than me that this functions as a wave guide with a wave length equal to 1/4 (or 1/2 ?) wave length for 2.4 GHz. It has something to do with reciprocity and Maxwell, and then my eyes start to glaze over beyond that.

My testing was to cut a slot in a spare carbon tube and mount my altimeter bay near it. In one set of tests, I basically covered the whole tube in foil and then tested the configuration with the slot exposed and not exposed. In the second set of tests, I just kept the ends of the tube covered with foil, and either covered or didn't cover the slot itself. See the pics.

The key result is the pairing distance, which is the distance where you can still connect to the WiFi. With my rocket, the pairing distance was about 10 feet. For the covered tube in my testing (both configurations), this distance was reduced to about one foot at best (nowhere for signal to get in or out). With the slot exposed, the pairing distance increased to around 100 feet. Wow, what an improvement. It will work. Next is to cut a few more slots and then modify the altimeter bays to incorporate the switches.

Jim

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Jim, that is impressive for a relatively small slot.

Do you think this will have any significant effect on the strength of the airframe?
 
Jim- that's crazy that that actually works. How close are the electronics to it? Right under it, or so you have some leeway?
 
Jim, that is impressive for a relatively small slot.

Do you think this will have any significant effect on the strength of the airframe?

I don't think so. The one on the top stage has very little weight above it, and the middle stage air frame is a pretty thick tube. I will also fill the slot with epoxy, mainly to keep the wind out.

Jim
 
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