Composites, breaking Mach, and other stupidity.

Discussions on high/extreme altitude and mach busting rockets.

Moderator: Moderators

drew
Southern fried goodness
Southern fried goodness
Posts: 869
Joined: Sat Aug 01, 2009 10:20 pm
Location: Perth

Re: Composites, breaking Mach, and other stupidity.

Postby drew » Wed Jul 15, 2015 10:28 am

kopius wrote:Just my 2cents worth, I hate sleeves. I did some 4" and 7.5" lay ups of phenolic and blue tube wrapped tubes and found the sleeves to add a lot of overall weight. They also were a very bumpy finish and required a lot of work to smooth out the finish.


Fair enough. Sure they're not super easy to get on, but I think with 4 hands they're much quicker than a wrap or two of glass and I suspect structurally they're much stronger. As for the bumpy finish, I'll say this to anyone doing any layups themselves; use teflon coated peel ply. Have a look at TFish's glassing video, you'll see that's what he uses. It's the only peel ply I'll touch when doing layups. Skyshop in Queensland carries it, it's on page 36 under the name POROUS TEFLON COATED RELEASE FILM.

http://www.skyshop.com.au/COMPOSITE.pdf

Seriously, this stuff is magic. It compliments my "I want to do as little sanding as possible" approach to rocketry.
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

High Impulse
Rocket Crew
Rocket Crew
Posts: 281
Joined: Wed Dec 17, 2014 6:06 pm

Re: Composites, breaking Mach, and other stupidity.

Postby High Impulse » Wed Jul 15, 2015 11:06 am

Thanks all for your thought,

Rocket Star, when i simmed it up i can fit an L935 in their if i go drogue-less at apogee. Will that cover it :twisted: (but seriously it probably will only ever break mach once or twice in its lifetime, high thrust K motors are far too expensive for me to use more than once or twice) Most of the time the rocket will be in the transonic region and the glass would be done more so that it doesn't shatter on impact with the ground as opposed to the high stresses induced during flight (most of the time it will be running on 38's or high 29's).

But it might just be on the safe side to do it (plus it would give me some practice in something new).

Thanks Marty Monsta it gives me a bit more confidence if somone else is thinking along the same lines. What weight glass will be using for your build? I cant wait to see how it comes along :)

Well OTT the build equipment is probably the limiting factor in this enterprise. If i do decide to build it (which is more like when i get the money) i would have to purchase all of the fiberglassing equipment plus the glass some new epoxy (not sure what sort to use but will have to look into it) plus the phenolic. Now i haven't done any maths but im not 100% sure that that will be cheaper than the fibreglass tubes blake already sells.

If the premade fiberglass tubes were cheaper then i definitely would use them over phenolic to make the thing bullet proof but i chose phenolic purely based on its price (im a bit of a tight wad). I like the idea of keeping it in tension, but in saying that phenolic is much better in compression isn't it (but then if you glass it then its a composite so we can get fiber pull out etc in tension... a very tough decision indeed).

I had a thought this morning of using a fiberglass booster section and then the nosecone and av bay arrangement make in phenolic as it wont have the same amount of force on it but also needs investigating. the only issue i would have with a MD retainer is i will be running a wide range of motor diameters and lengths and that could be difficult to adapt for but nothing is too hard right ;).

Drew, could be another option to look at, i was thinking of buying some glass from bunnings and giving it a try on some smaller tubes first to get the hang of this so that i could do a bigger tube easier but the sleeves might be an easier option.

a glassing workshop would be a great idea, hopefully i will be able to squeeze some time away from uni and give it a try.

Thanks for all the help everyone, i just had one more concern i would like to raise...

Canards.. are they the devils spawn when it comes to cert and mach plus flights or can their issue with developing there own trajectory during flight be easily rectified.

I thought perhaps that you could mount them through the wall like the rear fins by using some kind of inner stuffer tube and a couple of centering rings but in my design they are in a shocking place right on top of the av bay. i could reduce the av bay to a 54mm tube and mount the fins to the switch band but i dont really want to after having some space issues with my current av bay design.

Does any one else have any good ideas or past solutions that have worked effectively??

Cheers,

Adam.
L1: Callisto - H410VM

martymonsta
Engineer
Engineer
Posts: 709
Joined: Mon Oct 13, 2014 11:57 am
Location: Drouin Vic.

Re: Composites, breaking Mach, and other stupidity.

Postby martymonsta » Wed Jul 15, 2015 10:45 pm

High Impulse wrote:high thrust K motors are far too expensive for me to use more than once or twice


Especially once you have seen a stack of O flights and are think I gotta get me some of them. :lol:

Thanks Marty Monsta it gives me a bit more confidence if somone else is thinking along the same lines. What weight glass will be using for your build? I cant wait to see how it comes along :)


125gsm (4oz), I'm going on what John Coker said in the video that I posted above, smaller then 4" 4oz, bigger then 4" 6oz (200gsm) 4" could go either way. Well I guess I had better make this rocket happen and start posting now that I've let the cat out of the bag.

Well OTT the build equipment is probably the limiting factor in this enterprise. If i do decide to build it (which is more like when i get the money) i would have to purchase all of the fiberglassing equipment plus the glass some new epoxy (not sure what sort to use but will have to look into it) plus the phenolic. Now i haven't done any maths but im not 100% sure that that will be cheaper than the fibreglass tubes blake already sells.


I tried to work this out a while ago and by the time that you buy epoxy and glass and glove and peel ply and all the other bits and pieces, on a 3" tube its cheaper to buy FWFG from AR, and then there is the time is roll the tubes, however if you already have an epoxy system for doing fillets etc. then the price may swing back the other way. I'm doing the 3" as a learning experience aimed at testing the build techniques that I plan to use in a 6" with a 75 or 100mm MMT :D once you go to 6", glass over phenolic is cheaper, the larger FWFG are a touch spendy. If it was purely based on cost I would have gone the 3" FWFG but its about learning, not about cost.
Many years ago the great British explorer George Mallory, who was to die on Mount Everest, was asked why did he want to climb it. He said, "Because it is there."
Well, space is there, and we're going to climb it

MARS #21
AMRS #41 L2/LCO/RSO/CO

User avatar
SpaceManMat
Astronaut
Astronaut
Posts: 2036
Joined: Mon Dec 15, 2008 9:56 pm
Location: Brisbane

Re: Composites, breaking Mach, and other stupidity.

Postby SpaceManMat » Thu Jul 16, 2015 8:57 am

High Impulse wrote:Canards.. are they the devils spawn when it comes to cert and mach plus flights or can their issue with developing there own trajectory during flight be easily rectified.

I thought perhaps that you could mount them through the wall like the rear fins by using some kind of inner stuffer tube and a couple of centering rings but in my design they are in a shocking place right on top of the av bay. i could reduce the av bay to a 54mm tube and mount the fins to the switch band but i dont really want to after having some space issues with my current av bay design.

Does any one else have any good ideas or past solutions that have worked effectively??

Cheers,

Adam.

Not sure if you've seen it, but that's more or less what I did with my L2 AMRAAM
viewtopic.php?p=55533&sid=b28378702551c4edc3ed953598ba0ddb#p55533
QRS: 124
AMRS: 32 L2 RSO
Highest Altitude: 13,647 feet
Fastest Flight: Mach 1.55
Largest Motor: CTI 1115J530 IM
Current Project: X Wing


Return to “Higher, Faster, Further”

Who is online

Users browsing this forum: No registered users and 2 guests