Composites, breaking Mach, and other stupidity.

Discussions on high/extreme altitude and mach busting rockets.

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drew
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Composites, breaking Mach, and other stupidity.

Postby drew » Thu Jun 14, 2012 6:27 pm

So after the latest Williams Wildfire Westernationals I’ve been plagued with the thoughts of going Mach 2+. Given this I’ve decided to embark on a process of building minimum diameter airframes to accomplish this goal. After flying two rockets past Mach 1 last launch (and recovering one of the two) I feel my path is set. So here’s the plan.

I should be receiving some of AeroPack’s minimum diameter retainers shortly. One of them I’ve ordered without an eye bolt affixed to it. My plan is to adapt this retainer (a M38BE) as the central structural point of a single break minimum diameter 38mm rocket. The focus of this rocket will be to produce a rocket from “off the shelf” components that will be capable of flying at near Mach 2 speeds. On the other side of the retainer I’ll affix a removable AV Bay / parachute tube assembly for “shotgun style” deployment. I’ve already got cuts of 29mm coupler and airframe in G12 and CF (remnants from modifying my Blackhawk 29) which will be used for said assembly. The airframe will be a severely cut down Mongoose 38 and will utilise the Mongoose’s fins. I’ll also be using a Shockwave 7:1 VK NC. I’ll house a Raven 2 (250G) in a Raven AV Bay in the 29mm coupler for deployment duties. The long 7:1 nosecone will have a BeeLine TX transmitter so I can hopefully recover the thing. I plan to fly it on Aerotech motors in a 38/1080 case, specifically J570's or J825's. All items will be bonded with ProLine epoxy as I’ve still got plenty.

The “second iteration” of this plan will be to produce a similar rocket, albeit with composite components I produce (with the goal of a lighter rocket and therefore faster speeds). I’ve got some CF sleeves from Soller as well as a couple yards of 2x2 Twill and Plain Weave (199GSM). With this rocket I’ll make my own fins, roll my own airframe, and possibly fabricate a nose cone. I’m still not sure about the NC though as that seems quite involved and I’ve got no experience historically with producing them.

Now, onto the plethora of questions that arise from my stupidity, I mean, goals.

1) Does anyone know where to lay their hands on Porous Teflon Coated Release Film (peel-ply) domestically? Specifically this stuff. Otherwise anyone have any recommendations on release agents that when removed require minimal airframe sanding?
http://www.aircraftspruce.com/catalog/cmpages/vb7025.php

2) Cotronics Epoxy. Which one should I consider when making airframes and fins? I’m suspecting I’ll want the Duralco 4700 but I’m very unfamiliar with these epoxies.
http://www.cotronics.com/vo/cotr/ea_ultratemp.htm

3) Curing. I’ve been able to lay my hands on a simple curing oven setup (Cheers PK). That stated I’d like to cure under pressure even though I know it can be quite challenging. Any recommendations on quality equipment for accurate curing temps and relevant vacuum bag systems/techniques that can withstand a fairly high heat cure would be appreciated. I’m leaning more towards off the shelf components for this if possible as I feel confident that I spend too much time on rockets already.

I’m sure I’ll have more questions but right now that’s good enough to get me started. Any assistance would be appreciated.

Cheers folks.
Andrew Hamilton
AMRS 28 L3
AMRS Records Committee Chairman
Max Alt AGL - 23,908ft - K300 - Balls 22
Max V - 2,488 ft/s, ~Mach 2.2 - M2250 - THUNDA 2015

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Re: Composites, breaking Mach, and other stupidity.

Postby OverTheTop » Thu Jun 14, 2012 6:50 pm

Good luck with this bird. I am thinking of something along the same lines. Using the minimum diameter retainer can allow the aft section (fin can) of the airframe to be in tension. That is where composites shine for strength and also fortuitously where most of the mass is!

Forward of the retainer only basically needs to support (G + 1) times the mass of the airframe and NC (G is peak accel). Should make for a nice light rocket and a screaming flight.

Have fun!
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Re: Composites, breaking Mach, and other stupidity.

Postby ROCKet STAR » Thu Jun 14, 2012 7:02 pm

Hi Drew,

I'm sure this thread will make for interesting reading. I currently have a 38mm carbon tube rolled that I plan to do something similar with :)

As for peel ply, I buy it from these guys: http://boatcraft.com.au

Good Luck!
Chris Barnes

AMRS# 29 - L3

UKRA - L3

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Re: Composites, breaking Mach, and other stupidity.

Postby PK » Sat Jun 16, 2012 7:25 pm

Sigh.. Poor Drew, my diagnosis that you have contracted a terminal case of Lotterings disease.

You could do this in metal for a poofteenth of what you're gonna spend trying do do this with exotic epoxies.

I know I'm talking to a wall here so let's just move on....

Use glass and phenolic resins. Carbon will just conduct heat into the entire matrix and your epoxies will turn to mush. Phenolic glass will just insulate.
Go fast enough and it will ablate, char and insulate even better.

You don't see many carbon fibre heatshields.

The only downsides to glass/phenolic are that they are cheap, reasonably easy to get and don't confer any "My rocket has a positronic brain and is machined from a single block of elemental I'mbetterthanyouium!" type bragging rights.
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Re: Composites, breaking Mach, and other stupidity.

Postby cryoscum » Sat Jun 16, 2012 7:50 pm

Evil nanna! :twisted:
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Total impulse for 2016: 32,458 Ns (thus far)
Total impulse for 2015: 84,231 Ns
Total impulse for 2014: 40,757 Ns
Total impulse for 2013: 62,927 Ns

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Re: Composites, breaking Mach, and other stupidity.

Postby Scoop1261 » Sat Jun 16, 2012 10:49 pm

PK wrote:Sigh.. Poor Drew, my diagnosis that you have contracted a terminal case of Lotterings disease.

You could do this in metal for a poofteenth of what you're gonna spend trying do do this with exotic epoxies.

I know I'm talking to a wall here so let's just move on....

Use glass and phenolic resins. Carbon will just conduct heat into the entire matrix and your epoxies will turn to mush. Phenolic glass will just insulate.
Go fast enough and it will ablate, char and insulate even better.

You don't see many carbon fibre heatshields.

The only downsides to glass/phenolic are that they are cheap, reasonably easy to get and don't confer any "My rocket has a positronic brain and is machined from a single block of elemental I'mbetterthanyouium!" type bragging rights.



:lol: :lol:

Humor at it's best!

:lol: :lol:
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Re: Composites, breaking Mach, and other stupidity.

Postby CATO » Mon Jun 18, 2012 9:38 pm

You guys are too funny.....
"In thrust we trust"

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Ns 17: 5,973; 16: 34,558; 15: 35,955; 14: 6,016; 13: 10,208
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Re: Composites, breaking Mach, and other stupidity.

Postby strud » Tue Jun 19, 2012 6:50 am

So what can we do about sourcing Phenolic resin ?

As we know this should be easy since is it likely the most widely used resin 'in the world' however the previous supplier we've used no longer makes it in Aus it seems.....

It is harder and more brittle than many epoxies we typically use I believe. It also must be cured at elevated temp ie this is not an option.

Our beloved Dr Cato has made an airframe this way from memory, which pulled about 100G off the pad and was never seen ever again.

CS

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Re: Composites, breaking Mach, and other stupidity.

Postby PK » Tue Jun 19, 2012 7:27 am

strud wrote:So what can we do about sourcing Phenolic resin ?

Maybe a deal with O'Brien's can be had??

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Re: Composites, breaking Mach, and other stupidity.

Postby drew » Thu Jun 21, 2012 6:06 pm

After much soul searching and a couple rolls of the chicken bones whilst spraying fresh chicken blood across them I believe I've come to a solution. I will do THREE iterations of this build! The third will be a PK special built out of glassed phenolic. Relevant orders have already been made to respected vendors (thanks Blake!) and hopefully I'll have some 38mm phenolic tubing shortly.

In reference to phenolic resins PK, I'm keen to look into these. That said I've got little experience with them personally.

The main reason why I'd like to utilise high temp epoxies is Nic's experience with Sideshow 4. Every time I look at sad faced Blake holding that rocket with shredded fins all I can guess is the leading edge of the fins were met with enough heat to partially melt the epoxy and cause the layup to separate and shred. As mentioned in the thread the fin fillets held up fine so I'm doubting fin flutter had much play in the failure, especially initially. I could easily be wrong though.

I'll admit, I like CF. It looks nice, it's strong, and has positive weight characteristics. The cost differential for sleeves is roughly 2:1 in this airframe size and given the lengths I'll be using I'm probably going to be out of pocket $11 for using CF instead of Fiberglass for the airframe.

In reference to exotic epoxies, At this point I'm kinda leaning towards ProLine 4100. It has beneficial heat characteristics and Wildman sells it at a reasonable price.

I've already ordered some of the Teflon coated Peel Ply from Sky Shop in Queensland (skyshop.com.au). The product can be seen here.
http://www.skyshop.com.au/pdf/2009-2010_catalog%2039.pdf
The line item is "POROUS TEFLON COATED RELEASE FILM - #7025"

I've chosen to use this peel ply after watching some of tfish's videos on youtube. This is a convenience choice, I spend enough time sanding as is and my shoulder despises me for it.
Andrew Hamilton
AMRS 28 L3
AMRS Records Committee Chairman
Max Alt AGL - 23,908ft - K300 - Balls 22
Max V - 2,488 ft/s, ~Mach 2.2 - M2250 - THUNDA 2015

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Re: Composites, breaking Mach, and other stupidity.

Postby PK » Thu Jun 21, 2012 6:39 pm

Like I said, talking to a wall.
Have you considered making the rocket out of Ice Cream?
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Re: Composites, breaking Mach, and other stupidity.

Postby drew » Thu Jun 21, 2012 6:48 pm

Silly me, I thought phenolic resin and ice cream were two different things...
Andrew Hamilton
AMRS 28 L3
AMRS Records Committee Chairman
Max Alt AGL - 23,908ft - K300 - Balls 22
Max V - 2,488 ft/s, ~Mach 2.2 - M2250 - THUNDA 2015

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Re: Composites, breaking Mach, and other stupidity.

Postby cryoscum » Thu Jun 21, 2012 8:43 pm

Evil nanna! :evil:

Drew, your endeavor is both valid and relevant. Some big names in rocketry are chasing the same dragon at this very moment. Not all rockets are machined from a solid chunk of aluminium and remember that virtually every great leap forward has been initiated by a defiance of the pragmatic. So, just keep going. New ideas are what makes this a great hobby.

Cheers
N
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AMRS Technical Advisory Group

Total impulse for 2016: 32,458 Ns (thus far)
Total impulse for 2015: 84,231 Ns
Total impulse for 2014: 40,757 Ns
Total impulse for 2013: 62,927 Ns

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Re: Composites, breaking Mach, and other stupidity.

Postby OverTheTop » Thu Jun 21, 2012 9:23 pm

Sounds good Drew. I'm looking at a mix of some sort (not yet decided) composite materials. I am currently researching how best to use the different materials to get better damping ratios. If I can improve those, I can build lighter for adequate strength. Complex composites are called that because they aren't straight-forward! Lots of interactions between the fibers and filler materials.

I'm guessing I will need to do some (probably destructive) testing for confidence. Most of the composite books seem to rely on testing as the assembly of the composite can greatly vary affecting strength.

Also looking at aluminium leading edges to keep it somewhat together. Maybe some other idea might jump into my head also.

Looking forward to learning from your results as I'm sure you will beat me to the launchpad :D
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Re: Composites, breaking Mach, and other stupidity.

Postby Kryten » Sat Jun 23, 2012 10:10 am

I can't remember if this was posted in another thread - but If you wrapped the edges with aluminium strips you'd prevent fraying of the composite at the edges. Probably just leading and tip edges - don't worry about the trailing edge
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