8" Fincan

Discussions on high/extreme altitude and mach busting rockets.

Moderator: Moderators

User avatar
cryoscum
STOP... Hammer Time The Prodigy
STOP... Hammer Time    The Prodigy
Posts: 1802
Joined: Wed Oct 06, 2010 2:54 pm
Location: QLD, NSW & VIC

Re: 8" Fincan

Postby cryoscum » Thu Jul 14, 2016 7:21 pm

Blake was kind enough to put the fin frame drawing through his router while I was up in Brisbane earlier in the week.
Material is G10 3.2mm thick, colour = "Agent" Orange.
0.JPG
0.JPG (74.03 KiB) Viewed 1919 times

Back in a frosty Albury, after work today I assembled the fin frames with some 5 minute epoxy and got the bulk Epiglue in place to form the beveled fin edges. Included angle is 10 degrees.
1.JPG
1.JPG (65.6 KiB) Viewed 1919 times

2.JPG
2.JPG (53.24 KiB) Viewed 1919 times

The Corecell will go into the central areas and the whole thing then wrapped in carbon...
AMRS L3 | NAR L3 | QRS 089 | MDRA 224
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

User avatar
cryoscum
STOP... Hammer Time The Prodigy
STOP... Hammer Time    The Prodigy
Posts: 1802
Joined: Wed Oct 06, 2010 2:54 pm
Location: QLD, NSW & VIC

Re: 8" Fincan

Postby cryoscum » Wed Jul 27, 2016 8:10 pm

With the Corecell inserts in the fins done and the last shape grinding complete I've put the fins aside for the moment.
The attachment 0.JPG is no longer available


The next step was to figure out how to make a length of all carbon tube that had an ID of exactly 8". Sure, you could probably get a galvanized steel pipe like that, but I understand they are notoriously "not-so-round", hence the 'nominal' OD rating - good for water, bad for mandrel! Decided that it'll be best to just not use a mandrel at all.

I made a 700mm long carbon tube on the 10.1" mandrel I have with only a single layer of 200GSM plain weave. Once cured this has the right amount of stiffness, but bends easily enough, to allow it to be used as an initial "skin" on a sub-frame. One cut along the length and you wrap it onto the sub-frame. Easy enough, just need to make sure the sub-frame is spot on and has enough points of support to ensure the roundness of the whole endeavor.

Some CAD and laser work made the frame:
0.JPG
0.JPG (68.09 KiB) Viewed 1874 times

1.JPG
1.JPG (52.61 KiB) Viewed 1874 times

3.JPG


I wrapped the single layer carbon skin onto it, pulled it tight and then did one full continuous layer of carbon tow to ensure it is tight onto the sub-frame. It is now ready for the bulk carbon layers to build the wall thickness up to approx 5mm.
4.JPG
4.JPG (74.4 KiB) Viewed 1874 times


In the meantime the new dry vane vacuum pump arrived, as the one I had would not be up to the upscale vac-bagging to come.
5.JPG
AMRS L3 | NAR L3 | QRS 089 | MDRA 224
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

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

Re: 8" Fincan

Postby martymonsta » Thu Jul 28, 2016 7:16 pm

Looking good Nic. It looks like you have got a nice smooth radius, I would have expected that it would be more of a Dodecagon.
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
cryoscum
STOP... Hammer Time The Prodigy
STOP... Hammer Time    The Prodigy
Posts: 1802
Joined: Wed Oct 06, 2010 2:54 pm
Location: QLD, NSW & VIC

Re: 8" Fincan

Postby cryoscum » Fri Jul 29, 2016 1:11 pm

martymonsta wrote:Looking good Nic. It looks like you have got a nice smooth radius, I would have expected that it would be more of a Dodecagon.

Hi Marty
Yes, it came up pretty good. The carbon sheet was fairly stiff and wanted to spring open, hence tightening it with the carbon tow made it take the shape of the 3 rings and the struts in between the rings only touched the inner surface. Works pretty well...
1.JPG
1.JPG (71.37 KiB) Viewed 1814 times


Will have to push hard this weekend as time is ticking!
AMRS L3 | NAR L3 | QRS 089 | MDRA 224
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

User avatar
cryoscum
STOP... Hammer Time The Prodigy
STOP... Hammer Time    The Prodigy
Posts: 1802
Joined: Wed Oct 06, 2010 2:54 pm
Location: QLD, NSW & VIC

Re: 8" Fincan

Postby cryoscum » Sun Jul 31, 2016 5:09 pm

The fins went into the vacbag with the initial layers of carbon on it. The carbon totaled about 1200gsm per face with it wrapping around the edges to ensure continuity.
1.JPG
1.JPG (44.69 KiB) Viewed 1787 times

The cold weather is really slowing things down! Temp in the workshop never goes above 15 deg C this time of year, so I will have to think about how to use the hot box with the vacbag in there while under vacuum... No epoxy likes these kind of temps, but the Ly3600 really needs something like 30 deg C to ensure short polymer strings and initial curing above 40 deg C is the right answer for great results after ramped-regime heat treatment .

Stripped them this morning and did several hours in the hotbox to ensure the epoxy was fully cured before doing any sanding. Remember that this is not the primary (structural) heat treatment of the fin can - that only happens once it is complete and in one piece, just prior to the final finish (likely to be just a 2pack clear coat).

Some sanding and the fins are ready for bonding to the fin can tube, fillets and tip-to-tip to follow...
2.JPG
2.JPG (58.03 KiB) Viewed 1787 times
AMRS L3 | NAR L3 | QRS 089 | MDRA 224
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

User avatar
Jordz
Rocket Flyer
Rocket Flyer
Posts: 54
Joined: Sun Jul 03, 2016 8:26 pm

Re: 8" Fincan

Postby Jordz » Mon Aug 01, 2016 9:38 am

Hey rookie question here so bear with me, but why are you using corecell for the centre panel? Balsa wood supposedly weighs the same and has a higher lateral shear strength. Is there a difference in absorbence rates with the epoxy, or is there a siginificant enough weight saving to be had? Sorry for threadjacking, just curious.

User avatar
cryoscum
STOP... Hammer Time The Prodigy
STOP... Hammer Time    The Prodigy
Posts: 1802
Joined: Wed Oct 06, 2010 2:54 pm
Location: QLD, NSW & VIC

Re: 8" Fincan

Postby cryoscum » Mon Aug 01, 2016 4:08 pm

Jordz wrote:Hey rookie question here so bear with me, but why are you using corecell for the centre panel? Balsa wood supposedly weighs the same and has a higher lateral shear strength. Is there a difference in absorbence rates with the epoxy, or is there a siginificant enough weight saving to be had? Sorry for threadjacking, just curious.


Hi Jordan

There are a few reasons why I prefer Corecell over balsa:
- balsa coring panels are not widely available, e.g. Gurit makes a thing called Balsaflex that would work OK for this application, but the ONE small factory that it is manufactured at is running at 110% capacity to supply the wind farm market. For me to get some of it is not so easy and you need to order a lot at once. Corecell I can get any day of the week.
- Balsa may have higher mechanical properties than the Corecell M80 I use, but the medium density Balsaflex (the only one you have any hope of getting) weighs 150kg/m3, almost double that of the corecell (80kg/m3). On top of this, balsa really wicks the epoxy at a much greater rate than the corecell, making the final composite even heavier without any added strength. A corecell construction weighing the same as a balsa fin of the exact same design would have a lot more reinforcing cloth in it, thus making it inherently stronger for the same weight. So, if you have 2 fins of identical shape and thickness and they are of exactly the same overall strength, the balsa one will weigh more than the corecell one.
- There are many questions surrounding the sustainability of balsa harvesting. Sometimes they are in plantations, but most often not and logging companies supplying it tend to have other issues associated with it, e.g. rain forest clearing to expand plantations etc. Australia nowadays have strict regulations as to how plantations are to be managed locally, certainly a good thing. Balsa, however, comes mostly from Central and South America (also PNG, Thailand, some Pacific Islands) and the same level of regulations, chain of custody, environmental practices / certifications and good common sense does not prevail there. I therefore do not support the use of balsa in general, because it is likely that it came at too great a cost.

Thanks
Nic
AMRS L3 | NAR L3 | QRS 089 | MDRA 224
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

User avatar
Jordz
Rocket Flyer
Rocket Flyer
Posts: 54
Joined: Sun Jul 03, 2016 8:26 pm

Re: 8" Fincan

Postby Jordz » Mon Aug 01, 2016 4:40 pm

Appreciate the response mate, fair bit of info. Cheers :)

User avatar
cryoscum
STOP... Hammer Time The Prodigy
STOP... Hammer Time    The Prodigy
Posts: 1802
Joined: Wed Oct 06, 2010 2:54 pm
Location: QLD, NSW & VIC

Re: 8" Fincan

Postby cryoscum » Mon Aug 01, 2016 7:18 pm

It's raining again outside with temps in the low teens, so after work I went into the dungeon to go do some gluing.

Making a fin guide of this size gets tricky, so after some CAD and laser time, the fin guides were pieced together and put to use.
1.JPG
1.JPG (48.92 KiB) Viewed 1742 times

For now the fins are just tacked on with 5 minute epoxy with the bulk carbon/epiglue fillets to follow:
2.JPG


Starting to look like business...
3.JPG
3.JPG (115.25 KiB) Viewed 1742 times
AMRS L3 | NAR L3 | QRS 089 | MDRA 224
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

User avatar
cryoscum
STOP... Hammer Time The Prodigy
STOP... Hammer Time    The Prodigy
Posts: 1802
Joined: Wed Oct 06, 2010 2:54 pm
Location: QLD, NSW & VIC

Re: 8" Fincan

Postby cryoscum » Mon Aug 15, 2016 1:58 pm

Fillets and external layers of carbon all done. Now just refining the surface and the final heat treatment before paint.
1.JPG
1.JPG (82.59 KiB) Viewed 1670 times

2.JPG
2.JPG (61.27 KiB) Viewed 1670 times
AMRS L3 | NAR L3 | QRS 089 | MDRA 224
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

strud
Engineer
Engineer
Posts: 917
Joined: Thu Oct 02, 2008 7:37 am
Location: Central Tablelands, NSW

Re: 8" Fincan

Postby strud » Mon Aug 15, 2016 2:41 pm

Hi Nic

Does the assembly accumulate much distortion during the curing process ?

User avatar
cryoscum
STOP... Hammer Time The Prodigy
STOP... Hammer Time    The Prodigy
Posts: 1802
Joined: Wed Oct 06, 2010 2:54 pm
Location: QLD, NSW & VIC

Re: 8" Fincan

Postby cryoscum » Mon Aug 15, 2016 7:28 pm

Hi Strud, hope things are well over there?

Distortion isn't something that I've tried to quantify of late as I've not had problems with it. Heating things up too fast seems to guarantee disaster whilst slow-and-easy ramping seems to have no effect on shape, noting that the initial cure happens at room (20-ish) temp for 24 hours. Another 24 hours at "warm Brisbane Day" (35-ish) in the hot box tends to ensure the epoxy is fully cured before you start the serious polymer cross-linking. The low temps this time of year is the biggest enemy I've found to rocket building with composites... Environmental control mitigates this and investing in additional equipment is always a good idea, but "brace for impact" when your energy bill shows up :(

In addition to this, good circulation inside the hot box is crucial to avoid hot / cold spots. When closed there is a veritable gale blowing inside and three independent thermometers, spread out to the extremities of the box, confirm the temperature variance, usually no more than 1 deg.

To complete the answer then, the fin can seen there in the hotbox for it's final heat treatment has already spent several hours at elevated temps during various stages of construction and I don't expect distortion worth mentioning at this point, even though the final stretch sees it sitting at 90 deg C for 4 hours after ramping up. The max strength (approx 80MPa ultimate tensile strength for the epoxy) has already been reached and this last push to heat treat at 90 deg C is purely to increase the glass transitioning temp further (useful for high Mach flights). This is something they don't put in the instructions...

Hope to catch up with you soon in central NSW :)

Cheers
N
AMRS L3 | NAR L3 | QRS 089 | MDRA 224
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

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

Re: 8" Fincan

Postby martymonsta » Mon Aug 15, 2016 7:59 pm

Wow Nic. Really nice job. Did you vac bag the external layers of carbon? And what size did you end up making the fillets?
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
cryoscum
STOP... Hammer Time The Prodigy
STOP... Hammer Time    The Prodigy
Posts: 1802
Joined: Wed Oct 06, 2010 2:54 pm
Location: QLD, NSW & VIC

Re: 8" Fincan

Postby cryoscum » Mon Aug 15, 2016 8:50 pm

Hi Marty. Yes the outer layers (2 x 387GSM) were vac-bagged on. What a PITA to do that size in a huge bag! Once bagged, vacced and looking OK, I transferred it to the hot box. One hour later at 75 deg C and it was done. Plenty of sanding and a session of wipe-on-wipe-off got it to this point...
The fillets are about 40mm radius, but this fin can is intended for a P-motor after all...
AMRS L3 | NAR L3 | QRS 089 | MDRA 224
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

User avatar
SpaceManMat
Astronaut
Astronaut
Posts: 2076
Joined: Mon Dec 15, 2008 9:56 pm
Location: Brisbane

Re: 8" Fincan

Postby SpaceManMat » Tue Aug 16, 2016 9:22 am

cryoscum wrote:Hi Marty. Yes the outer layers (2 x 387GSM) were vac-bagged on. What a PITA to do that size in a huge bag! Once bagged, vacced and looking OK, I transferred it to the hot box. One hour later at 75 deg C and it was done. Plenty of sanding and a session of wipe-on-wipe-off got it to this point...
The fillets are about 40mm radius, but this fin can is intended for a P-motor after all...


What do you use for primer / filler?
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 1 guest