Cooking pre preg Carbon

[Bad Kitty 252]

Hey there, anyone got any thoughts on an easy way to cook our new carbon rudder stocks?

We've got the vacuum side sorted, but need to get them to about 100 degrees.

Size is 1500mm x 90 x 120 approx, so need about 1600 long x 250 wide x 150 high of cooking space.

We've got a gas heater that should get up to temp but how do I make an oven?

Fire bricks?

Any input welcome.

Thanks,

[Guest]

Check the thread on pizzas

[Guest]

Go to Hirepool and get the pig spit!

 

You may struggle to hold temp, some people just use 40 gallon drums...

[chic014 0]

Depending on the mould shape and how you're doing it you could use a heater blanker with insulation as seen in:

 

 

Near the end they put on silver heating pads. Also commonly used in military field repairs. Or you could build an insulated box and heat that with a gas or electric heater.

 

Are you sure you need 100degC? Some prepregs cure as low as 65degC now. Generally you can halve the cure time for every 10degC increase in temperature, but follow the manufacturer's data sheet.

 

You usually need good control of the ramp rate and temperature. Having some accurate thermocouples in the part is good and base all your timings of the lagging thermocouple, to ensure you get to a full degree of cure. Depending on how thick your part is you may need to have an intermediate temperature dwell to reduce the chance of a high peak exotherm, which will cause degradation of the resin.

[wheels 543]

I have to raise the same question. You sure it's 100degC? Or is it 100deg F

Because 50 to 65 is the norm. The temp does not have to be gained from and "oven" as such. Infra red heat lamps will work. The other thing is, see if you can hire a Car paint bake room, maybe even when they are baking a car, there maybe enough room to put the rudder in.

[VERGE 1]

Chest freezer or old catering fridge. Cut hole direct fan heater inside, have seen pvc pipe with multiple holes used to distribute heat more evenly in enclosure.

[Guest]

A sheet of low density polystyrene, 40mm odd maybe, chop to size and make a box, may need 2 sheets. Seal it against air leaks i.e. use gaffer tape to construct it. Blow in heat from one end and you'd be surprised at how hot it can get and stay. We cooked our Javs that way and just left one of those oil column heaters inside, worked brilliantly.

 

Watch your heat source doesn't melt the foam or your rudders may resemble a BBQed snarler.

 

I think Wheels may have a good point, check the temp and if C's or F's. 100C does sound up there.

[otto 31]

Done this, you on the shore?

PM me with an email address.

[Guest]

A sheet of low density polystyrene, 40mm odd maybe, chop to size and make a box, may need 2 sheets. Seal it against air leaks i.e. use gaffer tape to construct it. Blow in heat from one end and you'd be surprised at how hot it can get and stay. We cooked our Javs that way and just left one of those oil column heaters inside, worked brilliantly.

 

Watch your heat source doesn't melt the foam or your rudders may resemble a BBQed snarler.

 

I think Wheels may have a good point, check the temp and if C's or F's. 100C does sound up there.

 

Hey - sknot-me is spot on. Temp does sound a tad high. I used 100mm Polystyrene sheets - 8' x 4' x 4" - used 5 of them - made good sized heat-box. Vey efficient. Used a 2400w - 240v - heat gun - baked products regularly over 20 years in the industry & easily got 180 degrees C when required for electrical work. At 80* to 90*C was curing - double catalyst system, 68% solids isothalic polyester resin & easily getting 90% cure factor fibreglas laminate - just like 'Sundancer' was built - just the other day - back in 1967. Laminate in now VERY old hat but still structurally sound. Shame about the boat & bigger shame about the owner. FDH!!!

 

When you're finished with the Polystyrene sheets - cut to size - use solvent free epoxy/hardener, some dynel & make a top-shelf 'chilly-bin' which will hold ice for 5 to 8 days. No waste, & at the end - very cold beverages - you to beer, Mt Gay & me to lots of vodka - Here, here to many 'sundowners' - on tap (Smithy!!) or in small buckets. Ciao, james

[Guest]

A sheet of low density polystyrene, 40mm odd maybe, chop to size and make a box, may need 2 sheets. Seal it against air leaks i.e. use gaffer tape to construct it. Blow in heat from one end and you'd be surprised at how hot it can get and stay. We cooked our Javs that way and just left one of those oil column heaters inside, worked brilliantly.

 

Watch your heat source doesn't melt the foam or your rudders may resemble a BBQed snarler.

 

I think Wheels may have a good point, check the temp and if C's or F's. 100C does sound up there.

 

Hey - sknot-me is spot on. Temp does sound a tad high. I used 100mm Polystyrene sheets - 8' x 4' x 4" - used 5 of them - made good sized heat-box. Vey efficient. Used a 2400w - 240v - heat gun - baked products regularly over 20 years in the industry & easily got 180 degrees C when required for electrical work. At 80* to 90*C was curing - double catalyst system, 68% solids isothalic polyester resin & easily getting 90% cure factor fibreglas laminate - just like 'Sundancer' was built - just the other day - back in 1967. Laminate in now VERY old hat but still structurally sound. Shame about the boat & bigger shame about the owner. FDH!!!

 

When you're finished with the Polystyrene sheets - cut to size - use solvent free epoxy/hardener, some dynel & make a top-shelf 'chilly-bin' which will hold ice for 5 to 8 days. No waste, & at the end - very cold beverages - you to beer, Mt Gay & me to lots of vodka - Here, here to many 'sundowners' - on tap (Smithy!!) or in small buckets. Ciao, james

 

 

I wish english wasn't a 2nd language to you

[Bad Kitty 252]

I have to raise the same question. You sure it's 100degC? Or is it 100deg F

Because 50 to 65 is the norm. The temp does not have to be gained from and "oven" as such. Infra red heat lamps will work. The other thing is, see if you can hire a Car paint bake room, maybe even when they are baking a car, there maybe enough room to put the rudder in.

 

70 minimum, 16 hr cure

80, 8 hrs

100, 2 hrs

120, 30 mins.

 

65 degrees won't cure it.

 

Working on a couple of options, Otto, will pm you tomorrow Ta.

[wheels 543]

Wow. What the heck resin is it? I am really surprised. Al the resins I know would boil and smoke like heck at 100 to 120 deg.

 

Umm silver Raven, you don't need to heat cure Polyester resins. It is not a chain link resin like Epoxy. Polyester starts curing from the day it went in the can. The catylist (Ketone Peroxide) simply speeds up the reaction process. With epoxy, the molecular chains link to create a solid material. You have one "half" of the chain in part A and the other "half" in part B. But as the resin links and becomes thicker, the chains have greater difficulty in coming to gether to continue linking. Heating causes the liquid to become more fluid and thus allows the remaining chains to find each other. Then once it cools again, the resin stiffens and all the chains have linked and you get the best strength possible.

[chic014 0]

Yea those cure cycles sound more like what I'm used to. I assume you're not mass producing these, so I would recommend trying to stay as low temp as possible, as your tool will distort less(less of an issue if you have composite tooling), you will have smaller thermal gradients(and therefore cure gradients and cure warpage), and voids will expand less at lower temps.

 

 

Wheels remember this is prepreg, not post curing ambient temp resin. This is a low temp curing prepreg resin. They only get higher temp from there. Generally the Tg of the resin is only ever slightly above the temperature at which you cured it. E.g if you cure a wet layup or infusion boat at 20degC in NZ, then take it to the islands, it will probably get floppy around 30degC, so a typical post cure is ~65degC to get maximum cure and Tg. With prepreg the same rules apply except every thing is shifted up the temperature scale. If you want something to work at 100degC, you have to cure it above that. 120degC is typical cure temp for aerospace prepreg.

[Guest]

I wish english wasn't a 2nd language to you

 

I thought it was one of James more cohesive postings.

 

Interesting topic guys.

[Guest]

We cooked the Javs at 70 degrees inside the bodged up polystyrene box. 12hours each and with very little fiddling we were able to maintain a steady temp the entire time.

[Bad Kitty 252]

So no-one suddenly remembered that 1.8mtr wide pizza oven in the garage then?

[That Guy 0]

have you considered a section of spiralock tube? you can get it any diameter. Wrap your tube in bats and use fan heaters to heat. One blowing down the top of the job from one end and the other below blowing from the other end along the bottom. make sure you have some form of vent at both ends, to control temp simply restricted the size of the vent.

I would recommend the purchase of an infrared thermometer. try get the smaller version with the approx 1/2" sensor this way you can drill a few 1/2" holes and check the temperature through out the cook.

[Bad Kitty 252]

have you considered a section of spiralock tube? you can get it any diameter. Wrap your tube in bats and use fan heaters to heat. One blowing down the top of the job from one end and the other below blowing from the other end along the bottom. make sure you have some form of vent at both ends, to control temp simply restricted the size of the vent.

I would recommend the purchase of an infrared thermometer. try get the smaller version with the approx 1/2" sensor this way you can drill a few 1/2" holes and check the temperature through out the cook.

 

Thanks, what's spiralock made from?

[That Guy 0]

have you considered a section of spiralock tube? you can get it any diameter. Wrap your tube in bats and use fan heaters to heat. One blowing down the top of the job from one end and the other below blowing from the other end along the bottom. make sure you have some form of vent at both ends, to control temp simply restricted the size of the vent.

I would recommend the purchase of an infrared thermometer. try get the smaller version with the approx 1/2" sensor this way you can drill a few 1/2" holes and check the temperature through out the cook.

 

Thanks, what's spiralock made from?

 

tin, its mainly used as extraction, chimneys etc

[Guest]

have you considered a section of spiralock tube? you can get it any diameter. Wrap your tube in bats and use fan heaters to heat. One blowing down the top of the job from one end and the other below blowing from the other end along the bottom. make sure you have some form of vent at both ends, to control temp simply restricted the size of the vent.

I would recommend the purchase of an infrared thermometer. try get the smaller version with the approx 1/2" sensor this way you can drill a few 1/2" holes and check the temperature through out the cook.

 

Thanks, what's spiralock made from?

 

G'day 'B-K' ? - is there a good 1 ?? We have a product here in OZ that's called 'cliplock' - it's made from high density polystyrene sheet (not foam)& is used for the molds for the in-situ molds for concrete pillars. I can't remember how high you can take the temp before distortion. 20 yrs since I used it however it was OK for moderate temps of aprox 80* C. without distortion.

 

Tnx 'E-E' - bit difficult to advise anyone in this forum as there are many persons in here that know so much - so much more than everyone else - even when they might only be expressing a very limited knowledge personal opinion. Shame that, but that's life, eh.

 

1000's of high-teck polymer chemists have wasted many years (since the late 30') & countless dollars in the pursuit of top-shelf (high quality - high solids) resins & the best method of obtaining the maximum cure ( ie max $ value for $ spent) & they have been on the wrong track - just ask the guy in here that knows everything - KNOT. Again - that's a shame. There are many resins of all types that do not achieve full cure without being heat cured. The accepted cure - back some years now - was between 32% & 48%. With some modification of the hardeners used & in some cases the combination of hardeners the cure accepted raised to 70% & up to the high 80's & low 90's without to much difficulty - that's inspite of the 'better' knowledge in this forum.

 

These - "X-purts" (as the joke goes) have - of course - spent 30 to 50 years in the professions that they espouse to know everything about Yeaa RIGHT I think KNOT. It's a shame when it spoils it for so many others. Maybe in 2012 some may wish to express a more diplomatic attitude. Here's living in anticipation.

 

It's a bit like the conversation about 'foils' their design, construction etc. There was a valuable conversation happening until another 'he who knows everything' - - just ask him - he'll tell you whether you want to know or knot - how smart he is. Again KNOT

 

Everyone - everywhere - have a great festive season & I personally wish everybody a very successful 2012 - hope it's gets better & better for each & everyone of you all. Ciao, james!!!