"Mk4 Rocket Propelled Companion Pod" - SCR Quake L1 Build Thread...

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A nose cone bay should be relatively easy. The same size centering rings that fit the rocket should fit in the nose cone above the shoulder, at least that has been my experience. You will have to chop the base off to get acess of course. Depending on how you want it installed and what not, you won't necessarily need a tube inside. I just happen to be working on a 2.6" kit myself and will be putting a bay in the nose cone.

I hadn’t thought of using CRs in the nose cone, but now you mention it I’ve seen that on a few builds before.

Have you got any details of how you’re planning on building the AV bay in your 2.6”? I’d be interested in seeing it.
 
Yeah. I'll show you what I have in mind. Several ways to do it. I have done it on 3" and 4" nose cones already. I'm at work atm and I hate typing on my phone, may have to wait til I'm home. Can you cut your own rings?
 
Sent you a PM explaining the process. Didn't want to clog up the thread with such a lengthy write-up.
 
Yeah. I'll show you what I have in mind. Several ways to do it. I have done it on 3" and 4" nose cones already. I'm at work atm and I hate typing on my phone, may have to wait til I'm home. Can you cut your own rings?

No but I can order some.


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bay.jpg

Maybe this picture will help get what I was talking about. Don't know the exact dimensions of your nose cone but this will give you an idea of what you are striving for.

The yellow is the route your kevlar will take. You can do the kevlar several different ways, but this is the way I mentioned. The orange/red cap will actually be made onto the sled so it will all be one piece and held on with screws.

Another option would also be to let the inner tube run about 1/2" farther out and put a retainer on it. Like I say, if you can get one printed, that would be an easy way to close off the bay.

sled prints.jpg

I designed these for a RRC2+ and a 2 cell LiPo, fits in the box. While this setup is for a 4" nose cone, they fit in a 38mm tube. The tube I use is actually a sink drain head pipe but the OD is the same as 38mm motor tubes. This is kinda what you will be going for when building yours. Once I get my Viper nose cone chopped, I'll see if this sled fits in it and you may can use the exact same thing in yours.
 
View attachment 333230

Maybe this picture will help get what I was talking about. Don't know the exact dimensions of your nose cone but this will give you an idea of what you are striving for.

The yellow is the route your kevlar will take. You can do the kevlar several different ways, but this is the way I mentioned. The orange/red cap will actually be made onto the sled so it will all be one piece and held on with screws.

Another option would also be to let the inner tube run about 1/2" farther out and put a retainer on it. Like I say, if you can get one printed, that would be an easy way to close off the bay.

View attachment 333232

I designed these for a RRC2+ and a 2 cell LiPo, fits in the box. While this setup is for a 4" nose cone, they fit in a 38mm tube. The tube I use is actually a sink drain head pipe but the OD is the same as 38mm motor tubes. This is kinda what you will be going for when building yours. Once I get my Viper nose cone chopped, I'll see if this sled fits in it and you may can use the exact same thing in yours.

The NC pics are actually very helpful - thank you.

I’m not too keen on screwing through the NC shoulder - the CRs are only 3mm think, I don’t think there’s enough material to cope.

There’s always the option of running the Kevlar via the tip of the NC to prevent lateral timber tube damage.

I’m going to play with a few ideas.

OR isn’t good for sled mock-up or design and I’m yet to find a 3D CAD app that is cost effective and useful.
 

I’m not an EAA member... I don’t think I could be as an Australian can I?

Ive looked at solid works as a concept and the thought of having to use windows kinda makes me crazy (I’ve only JUST managed to get windows out of my life completely in the last 12 months, after 7 years of trying...)

I might have to have a play and figure out if it’s worth the effort...


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Some progress again tonight now I have glue and found 20mins to myself.

Fwd CR of the MMT glued in.

I’m getting used to MPR flue volumes (I’m pretty good at estimating LPR epoxy quantities) but I didn’t put enough into the tube for the fwd MMT CR.

After the 30min set time I removed the aft CR and realised there were gaps where there wasn’t enough epoxy.

Damn it!!

So I fashioned a “Laparoscopic squirter” out of a coffee stirrer and a 1ml syringe.

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I found that an old spritz bottle cover top was an ideal tall & thin epoxy mixing pot that allowed me to draw the epoxy more easily into the syringe without ending up with massive air bubbles.

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A little LapSquirt™️ later and I’d laid a fillet on the outer tube (paying attention not to encroach on fin tab territory.)

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It’s now resting vertical with the rear CR slotted in to cure overnight.

I realised when I (instinctively) ran a fillet in the aft side of the fwd CR in the MMT that I made it so the fin tabs wouldn’t sit flush on the motor tube.

I took advantage of some epoxy curing time to file the corners of the tabs off to allow for the MMT FWD CR fillet.

IMG_0013.jpg

Tomorrow I add fins...


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That drawing was done on FreeCAD, don't know if it is Windows only or not, I am not as into the computer field as I once was.
If done like the drawing you won't need screws. The recovery forces will be on the ring above the shoulder. The other ring is glued to the tube so it's not going anywhere. You could use small pins, needle small, in the forward ring to help hold it in place until the epoxy sets but they're not needed.
 
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That drawing was done on FreeCAD, don't know if it is Windows only or not, I am not as into the computer field as I once was.
If done like the drawing you won't need screws. The recovery forces will be on the ring above the shoulder. The other ring is glued to the tube so it's not going anywhere. You could use small pins, needle small, in the forward ring to help hold it in place until the epoxy sets but they're not needed.

Taken under advisement. I like this idea better than all thread. I’ll have a play and a think.

As for FreeCAD - it’s available on the Mac. As soon as there’s a version that doesn’t crash in the first few button presses I might try it out.


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Up late for work, so fins got done tonight:

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This means I can start internal fillets tomorrow between running around tasks.


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Internal fillets done.

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External fillets begun.

Started using the sharpie transfer method someone clever in these parts shared:

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So now I knew where the edges of the fillet would be once I pulled it.

Masked fin and BT and tried my best to make a tape dam to catch overflow. (If anyone has pics of a good way to make a dam - please post them...)

No pics of the tape setup - a distracting phone call meant I forgot to snap pics before I mixed the epoxy.

Working with 15min epoxy - more work time than 5min but there’s a lot more going on here.

I wanted to use a 10ml syringe to apply the epoxy so I could get a feel for how much is needed. Future fillets I might skip this step.

First fillet, I applied way too much (2x by my observations) if I was just letting it settle level it would have been ok, I failed to think through the fact that pulling the fillet meant I didn’t need as much.

Saved by a clever use of the cap I’m pulling with - used as a scoop to remove excess epoxy before it was a disaster.

Pulled the fillet with the tool pictured above (same spray cap seen previously) dipped in isopropyl.

Waited till the epoxy in the mixing container started to gel, then pulled the tape off.

Second fillet and this time I was a little light on the epoxy. Lesson learned - more mixed is better than not enough.

Overall - so far I think they look pretty smooth...

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That’s it for tonight. I’ll let it cure and do more in the morning...
 
Now that is a serious fillet! The tube may rip, but that fillet won't bust!
I built my L1 on my own (months before actually flying it) before finding the forum and really wish I'd known of some of the techniques back then.

Although these days, I use woodglue for the cardboard/ply Mid/L1 rockets.

Good to see you've got the tracker and chute release down for this skinny rocket to 3k'
 
Now that is a serious fillet! The tube may rip, but that fillet won't bust!
I built my L1 on my own (months before actually flying it) before finding the forum and really wish I'd known of some of the techniques back then.

Although these days, I use woodglue for the cardboard/ply Mid/L1 rockets.

Good to see you've got the tracker and chute release down for this skinny rocket to 3k'

Yeah - this for me is more about learning the construction techniques.

The computer bit I’m very confident with - it’s the building stuff with my hands part that is the massive learning journey for me.

I’d also like rockets like this to be long lasting - until the corn field eats them that is... [emoji12]
 
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Fillets 3 and 4 done.

I figured out how to round the ends - using my trusty pulling tool I can alcohol dip and just pull around the ends once the epoxy goes taffy like...

Pulling tool:
IMG_0013.jpg

I also remembered to photograph the tape layup this time.

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The results, I’m quite happy with:

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I’m particularly happy with the LE/TE root section - being able to drag the pulling tool around the LE/TE gave me what look like super slick transitions from BT to fin:

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Those have always been the part of the fin/BT transition I’ve hated the look of with all my previous builds...
 
MMT front end epoxied and drying.
View attachment 332808
I’m using 5min epoxy for this build - HW store only had 5min or 1-3hr epoxy - and I’m not that patient.

I’ll need to get some 15min from my local rocket vendor when I next think of it.

For what this rocket is doing though, I’m confident 5min will be ok. I’ll be using something more flowy like 15min for internal filets.


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How about this... use the 1-3 hr epoxy so you get the soak factor, but tack first with CA. Seems like the best of both worlds. Here is an example I found. The 1-3 was likely the same price as the 5 minute if your stores are like the ones near me.

Homer
 
5-min should be fine as long as all relevant surfaces are wetted properly and you don't try to go breaking records.

Heck, Big SAM doesn't even have mmt fillets, and it's survived with 5min lol (admittedly the most extreme it's seen is M.6 and 15g's)
 
CWF + sandpaper trying to even out some of the imperfections in the fillets.

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Slow progress while I wait for rail buttons to arrive.

CWF the nosecone seams

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Small dabs of CWF to fill some small air bubbles I found when finish sanding the fillets

IMG_0013.jpg

And another side of BT spiral filling to use up the mixed down CWF (I wasn’t going to bother with BT spirals, but I was there, I had the CWF and brush, and I’m still waiting on rail buttons...)

IMG_0013.jpg


I’ve opted for the double CR design nose cone AV bay. I ordered 66mm(coupler) to 38mm CRs and a 66mm coupler bulkhead in 3mm ply they should be coming with the rail buttons.

I’m planning on opening up the inside of the AV bay CRs to 40mm and will use BT60 (as I have heaps of it).
 
I’m curious if anyone has thoughts on altimeters in nose cones.

Anyone have a read on where / how vent holes can be put in NCs?

Should I do it though the shoulder and BT or should I drill the NC?


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If you're just doing it for maximum altitude readings, drilling holes in the nose near the base is fine. If you're trying to derive velocity from your readings with a baro altimeter, you need to do it down on the body tube.
 
You have an oblique shockwave across the nosecone if it's going past Mach 1. There are also un-relatable normal shocks when supersonic that are used to mathematically from compressible gas dynamics tables and shock diagrams to compute the oblique shockwave from normal shock tables as a component Mn1=M1* Sin(Beta). Then you read off the normal shock value at M2 the exit mach on opposite side of the shockwave in normal shock table = Mn2 etc as components of the mach numbers. Then you find M2 the exit mach as = Mn2/sin(Beta-wave angle). Then if the bugger reflects the oblique shock angle changes and you refer to a seperate chart again and start iterating for M3 values. The mach number drops is the nutshell idea across the shock. The pressures rapid change drop. There's turbulent flow. And even math doesn't know at some point. My head just started hurting in compressible gas dynamics at some point. The shocks can reflect, and it just gets harder to figure out where it is. You can physically drill a hole into a nosecone. I don't want to think about what would happen. I don't recommend it. You start messing with boundary layers, flow patterns, and shockwaves. A CFD will visualize that, I'm not even dork enough to do a CFD fully, but.... Reality man isn't math model always. Your dealing with invisible moving shockwaves here... The nosecone has a wave deflection angle and the mach number on a chart relates a Beta angle to that depending on mach number. A lot of bad unknowns await. You don't want a rapid unwanted force acting on that hole for any reason on a nose is my roughest stupid guess at this from a shockwave movement if its mach plus. There's stuff I don't even know, I just got an inkling of it. Sorry if I wank thread crapped all over it... Its a weird idea to grasp and I never knew it existed. Maybe someone else has an idea of how to explain it better.



When I talked with a L-3 RSO guy before scratching two multistages he said never drill pressure relief a hole in a nosecone. And we took that advice seriously. But hey I'm still a rookie. Down on the body tube or atleast in the nosecone shoulder or slightly lower is preferable. Don't piss off a shockwave.
Maybe you could do it on a subsonic rocket. Maybe it won't crash. I'm not ballsy enough to try and I admit that. Also heard drill one or three holes but not two.
 
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