G12 Tubes and Epoxy/Keying

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jase
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G12 Tubes and Epoxy/Keying

Postby jase » Wed Feb 22, 2012 6:18 pm

Not so much a me show you how to thread, more a could someone let me know if this is how to...

So, I've got one of those 4" PR Nike Smoke kits (thanks Trev) and was wondering if using 40 grit is sufficient for keying using epoxy (105/205/403 blend) to bond the MMT CR's to the airframe? (it's taken me 3 days to figure out how to frame that question!!! - hope it makes sense :oops: )

Aft view inside 4inch G12 tube.JPG
Aft view inside 4inch G12 tube.JPG (67.85 KiB) Viewed 3234 times


You can see I've scrubbed the hell out of the aft end with 40 grit as far in as need be - will that be enough?

I've search other threads/forums but maybe didn't look hard enough (ie: if there is a thread on this, could someone post a link?)

My first attempt at building using G12.

Thanks in advance.

[edit - typo]
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Re: G12 Tubes and Epoxy/Keying

Postby Scoop1261 » Wed Feb 22, 2012 6:20 pm

Yep!.....Scrubbing with 40 grit will set it pretty right for adhesion

Keep us informed of how the build goes. 8)
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Re: G12 Tubes and Epoxy/Keying

Postby jase » Wed Feb 22, 2012 6:26 pm

Awesome Scoop, thank you very much :D

The build will go bloody good now you've provided me with that advice :D

I've been staring at it since late last year :!:
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Re: G12 Tubes and Epoxy/Keying

Postby Lamp » Wed Feb 22, 2012 11:04 pm

Nice one Jase! :D
I have been repairing mine after the zipper last year, and converting it to DD, It is coming along slowly.

I'll look forward to seeing yours fly, I presume you will attempt your L2 with this..... :D
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Re: G12 Tubes and Epoxy/Keying

Postby jase » Thu Feb 23, 2012 7:41 am

G'day Pete :)

Yes mate, I reckon mid-year (still studying the exam).

I am taking my sweet time with this one and really really want to see it go up on a long burn motor (K270 or there abouts):

PR 4 inch Nike Smoke.jpg
PR 4 inch Nike Smoke.jpg (49.61 KiB) Viewed 3205 times


And then maybe something like a K1050 down the track 8)

Just ordered a bunch of motors for March, I've got a crazy mach-busting project on the go too (because I've never done it before and, you know, just 'cause!). A reasonably extemely modified Estes Executioner that I am planning to launch on an H268 and/or an I200 :lol:

Looking forward to catching up mate - fingers crossed for good weather.
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Re: G12 Tubes and Epoxy/Keying

Postby jase » Thu Feb 23, 2012 7:48 pm

So with a bit of trepidation here are some more (rank amateur) images:

54mm MMT with CR's.JPG
54mm MMT with CR's.JPG (161.85 KiB) Viewed 3188 times


I added a 'fin root' CR (5-ply doped with 105/205) that will literally butt against the fwd root of the fins - 316 Stainless U-bolt at the top.

54mm MMT Aft view with 'keying' slots.JPG
54mm MMT Aft view with 'keying' slots.JPG (94.04 KiB) Viewed 3188 times


Scoop - whilst I do not doubt your build credentials for one second, nor your advice, I asked about the 40 grit keying because it (to me) didn't seem adequate. What I've done in the image above to the MMT (prior to opening this thread) is use a cut off wheel attachment on the Dremel to add some 'deeper' keying points (about half way through the MMT, maybe ~0.75mm deep - aft/thrust plate/retainer end. Below them you can see my 40 grit work). I gave it a some consideration firstly thinking that I would weeken the structural integrity of the tube, but if it is being re-filled with 105/205/403 I reckoned that that should/would compensate? Waddayathink, because I was also thinking of doing the same to the inside of the airframe, fwd of where the CRs would need to be adhered to - in addition to the '40 grit workover'...? Or would that be overkill?

4 inch PR Nike Smoke 'bits'.JPG
4 inch PR Nike Smoke 'bits'.JPG (101.61 KiB) Viewed 3188 times


As the image name suggests - all the bits and pieces (54/1280 on left and 54/2560 on right for scale) - only thing I need to make from scratch is AV Bay/coupler.

Thanks again in advance for input/suggestions.
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Re: G12 Tubes and Epoxy/Keying

Postby Bourney » Sat Feb 25, 2012 4:57 pm

Hey Jase,

I think you're right about the epoxy filling those deep keying points, but from what I've seen on other sites and in Wildman's various instruction sheets I'd be sticking with a good roughing up with the 40 grit. I haven't heard of any coming adrift when using that method.

I note that your ubolt only has nuts underneath the CR, not above. I haven't seen it done that way before, any special reason you didn't use nuts both above and below the CR?

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Re: G12 Tubes and Epoxy/Keying

Postby Scoop1261 » Sat Feb 25, 2012 6:38 pm

Probably overkill but mechanical "keying" is the trick.
Whilst the 40 grit doesn't seem to make huge grooves, it is quite sufficient to get a good bond.

Clean with acetone after sanding and you should be good to go!
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Re: G12 Tubes and Epoxy/Keying

Postby jase » Sun Feb 26, 2012 1:08 pm

Bourney wrote:Hey Jase,

I note that your ubolt only has nuts underneath the CR, not above. I haven't seen it done that way before, any special reason you didn't use nuts both above and below the CR?

Cheers


G'day Bourney :D

'Cause they only came with two nuts in the bloody pack!!! :(

Ubolts and Carpet Roll core.JPG
Ubolts and Carpet Roll core.JPG (169.58 KiB) Viewed 3141 times


I reckoned that all of the force will be pulling adjacent to the nuts? (or not) - They also got a fair covering of epoxy when I finally plucked up the courage (thanks to Scoop's reply) to install the MMT. The nuts themselves got covered in epoxy (hopefully that'll do the job).

I added the Carpet Roll cores (95mm x 1800mm x 2.5mm) to the picture because I used a length of them to make the AV Bay (image to follow). I've got 6 of the buggers and reckon they'd make a nice rocket/s at some stage - also, anyone in TRAAU who is going to Serpentine in March want one - sing out!!!

I used 60ml of 105/205/403 which ended up being about ~8mm deep around the top MMT CR:

Down the barrel at the top of MMT.JPG
Down the barrel at the top of MMT.JPG (49.68 KiB) Viewed 3141 times


And since I got the MMT in and the shed was bloody hot 'cause it was 38c here yesterday, the epoxy cured quicker than usual so I thought 'might as well get the fins in, thrust plate and retainer (HAMR 54mm - thanks Trev!!!)':

Fins on.JPG
Fins on.JPG (153.01 KiB) Viewed 3141 times


And while all that was going on I decided that due to the extreme heat, me sweating so much and some 'build insanity' creeping in I'd get cracking on the AV Bay/Coupler using the Carpet Roll core and 6x layers of unidirectional CF:

AV Bay-Coupler on the BBQ Rotisserie.JPG
AV Bay-Coupler on the BBQ Rotisserie.JPG (124.27 KiB) Viewed 3141 times


I've never used electronics before so the mentality here is to completely overbuild the AV Bay in case tragedy strikes. Also, I am still getting use to using CF/epoxy so needed the practice - aiming for that really nice professional finish that still eludes me :( (I'll get there!)
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Re: G12 Tubes and Epoxy/Keying

Postby jase » Sun Feb 26, 2012 1:16 pm

Scoop1261 wrote:Probably overkill but mechanical "keying" is the trick.
Whilst the 40 grit doesn't seem to make huge grooves, it is quite sufficient to get a good bond.

Clean with acetone after sanding and you should be good to go!


Cheers Scoop :D

Me and Acetone are good friends now :lol: great for clean-up.

I also ended up injecting some more 105/205/403 in behind the middle MMT CR, drilled the hole under a fin root and made a smaller 'breath' hole just above it. They'll both be covered by a fin.

I suppose that with the 40 grit-work done and using pye r squared etc, there is quite a large surface area around the CR's to airframe for the epoxy to bond - I also rotated the tube when the epoxy was curing so that a tapered wall would build up, and to be sure to be sure :wink: fingers crossed.

Thanks again heaps for your advice - the thing has gone from 'bits and pieces' to almost looking like a rocket now!
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Re: G12 Tubes and Epoxy/Keying

Postby Scoop1261 » Sun Feb 26, 2012 1:19 pm

jase wrote:


And while all that was going on I decided that due to the extreme heat, me sweating so much and some 'build insanity' creeping in I'd get cracking on the AV Bay/Coupler using the Carpet Roll core and 6x layers of unidirectional CF:

AV Bay-Coupler on the BBQ Rotisserie.JPG


I've never used electronics before so the mentality here is to completely overbuild the AV Bay in case tragedy strikes. Also, I am still getting use to using CF/epoxy so needed the practice - aiming for that really nice professional finish that still eludes me :( (I'll get there!)



One thing to remember here is that CF is NOT radio transparent...... so if you are intending to put some sort of radio finding beacon or a GPS module in there.... don't be surprised when it doesn't get reception.

You can of course run an antenna outside the av bay and it will work quite nicely.....actually if your really clever you could embed an antenna into the outside of the av bay
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Re: G12 Tubes and Epoxy/Keying

Postby jase » Sun Feb 26, 2012 1:25 pm

Scoop1261 wrote:
jase wrote:
One thing to remember here is that CF is NOT radio transparent......


Indeed, good point.

At the moment I'm planning on using Stratologger and a Timer with G/Switch (maybe x2, Lamp has got me sold on the 'redundancy principle')...

I haven't look at the Fibreglass nosecone yet, and was thinking of sitting the Bulkhead plate back a bit to accomodate RF electronics down the track - that scares me a bit though considering the potential for 'lawn darting'...Although, if I want to get more involved in rocketry that will be one fear I'll need to overcome :P
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Re: G12 Tubes and Epoxy/Keying

Postby Scoop1261 » Sun Feb 26, 2012 1:27 pm

I assume you can get your hand down that tube to attach the shock cord to the U/Bolt then?
Why Limit Yourself?

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Re: G12 Tubes and Epoxy/Keying

Postby jase » Sun Feb 26, 2012 1:45 pm

Scoop1261 wrote:I assume you can get your hand down that tube to attach the shock cord to the U/Bolt then?


Yes, I made that mistake before on an Estes kit :lol:

I practiced a couple of times with some stainless quicklinks I used on my Tomahawk scratchie - same ID - snug fit with my forearms, but I managed to link-unlink ok.

In fact, what I've done with all of my recovery gear now is NOT to permanently attached it to any builds, hence the 4x stainless ubolts. I'm using 2x 3m 600kg tie-down straps with stainless quicklinks attached to both ends and carabineers on the chutes so they'll be all interchangeable. Probably a bit excessive I know, but that is me :|
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Re: G12 Tubes and Epoxy/Keying

Postby jase » Wed Feb 29, 2012 8:10 pm

Guess I've turned this into a build thread - sorry...

So, got the Av Bay on the thing tonight, finished the outer fin fillets last night and decided it was time to bring it inside so I can stare at it for a month or two deciding on paint colour:

waiting for paint.JPG
waiting for paint.JPG (97.26 KiB) Viewed 3104 times


I added two key switches to the outside of the Av Bay recessed into the CF, also some bevelled chrome LEDs for each switch - Green for Altimeter and Blue for the Timer. The rocket will never go supersonic, so hopefully they wont melt off :roll:

av bay external.JPG
av bay external.JPG (105.18 KiB) Viewed 3104 times


That is pretty much it I guess - apart from making the av sled, bonding the nose cone bulkhead plate and maybe getting a stainless steal nose cone tip machined...oh, and paint.
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