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andygtt
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morepower (22/08/2013)
Warren (Staff) (22/08/2013)
Its horses for courses at the end of the day.
Sure no ones doubting that pre-preg parts are the pinnacle of the industry at the moment.
But twice the material cost for something thats maybe 20% stronger and lighter.
Clearly not worth it for most people for larger panels. But it does have its place for smaller, complicated parts where material cost isnt such an issue.Twice the cost?? Dry cloth is about £20 per sq/m and resin works out about another £5 per sq/m Plus you need pipes and other consumables spiral tube and infusion mesh which is just under £6 per meter and there will be some extra resin wastage in the pipes through to the catch tank. So that is up to about £31 per sq/m plus VAT. Pre-preg can be had for between £36 and £48 per sq/m depending on which material you have and the PRF material is good enough for most people at less than £40 per sq/m. This is using a pre-preg that cost less than £40.00 per Sq/m and a motorcycle body kit is anything but small... But I have a week to lay up the parts and can take my time getting it all done.
no way I use £5 of resin per square meter of cloth... and I only use the same amount of infusion mesh etc regardless of layers... so a 4sq meter layup with 4 layers of carbon/kevlar using resin infusion is around £420 all consumables and resin. For pre preg thats over £680 (guessing £40 consumables tape, bag, breather etc) Im going to give pre preg a go at some stage, but for a DIY making body panels I see the cost of storing the materials long term as very high indeed... Id also need a massive oven (could do with one now tbh but it isnt a must have yet). One thing I would like to know... the difference in strength is mainly the resin properties... how strong/weak is the resin infusion resin compared to pre preg?
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morepower
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I got an 8 foot commercial freezer for £230.00 lol... Making an oven is not hard but it does take up space and the bigger the part the more space. I am lucky I can convert an old outside toilet into an oven. So I have 7 feet deep 4 feet wide and 9 feet high if I want to use it all.. So I still have all my workshop space and not have an oven taking up space.. So I am lucky... But the costs if you look round are not that high compared to many other manufacturing businesses like engineering ect...
You may find you can lose a layer of material or two in places and only add pre-preg where it is needed to get the strength where you need it.... My seat unit is 2 layers thick where it has no structural requirement but 10 to 15 layers thick where I need a lot of strength... It just depends where you need to have strength or just need something to create the shape.... lol
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TomDesign
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and what baking machine you use any advise and cost?>
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morepower
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TomDesign (24/08/2013)
and what baking machine you use any advise and cost?>I make up a box to suit my parts... It can be anything from 2 double wall cardboard boxes inside each other (Good insulator) or a brand new Wheelie bin for slightly larger parts.. My biggest parts have been done in a friends oven but when I have time I am going to line an unused outside toilet, which is in my garage at home, with sheets of Kingspan insulation and make a forced air circulation system which can be used with my portable heater and controller. Here is my basic heater set up.... http://www.ebay.co.uk/itm/261248875323?ssPageName=STRK:MEWNX:IT&_trksid=p3984.m1439.l2649 http://www.ebay.co.uk/itm/221069382477?var=520098955846&ssPageName=STRK:MEWNX:IT&_trksid=p3984.m1439.l2649http://www.ebay.co.uk/itm/3kw-Industrial-Heater-Electric-Thermostat-Fan-Heater-Portable-Blow-Cooler-Warm-/190734861601?pt=UK_Home_Garden_Hearing_Cooling_Air&hash=item2c68af0521http://www.ebay.co.uk/itm/261257736361?ssPageName=STRK:MEWNX:IT&_trksid=p3984.m1439.l2649http://www.ebay.co.uk/itm/190836999056?ssPageName=STRK:MEWNX:IT&_trksid=p3984.m1439.l2649I have had to alter the heater to keep the fan running and bypass the thermal over rides which turn it off at 65 degrees C and run the heating elements directly through the controller and 40amp SSR. The fan runs continually that way.
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TomDesign
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Any images of your construction autoclave? so can imagine all that stuff connected ? that would help a lot to get and visible idea!
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morepower
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I will get you a photo of my simple box oven for the small parts with everything connected when I make up the next part..... It IS basic.... lol
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TomDesign
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ye but give me an idea so i can try to build 
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fgayford
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mawgan (17/08/2013)
I am new here and have had a quick look through the forums and on the easy composites website/videos and I have yet to see any real advanced techniques shown (please correct me if I'm wrong and there is in fact advanced tutorials somewhere that state the techniques that I am referring to). I have personally had over 10 years experience working with all aspects of advanced composites and the family run company that I own has been in the business for over 30 years. We have worked mostly in marine but have covered all aspects along the way from F1 through to aerospace. I thought that I would list just a few things here and people can maybe carry this on and extend any knowledge/tips they may have learnt along the way. To start with, no matter what composite project you are working on, it is all in the preparation, it is the most important thing. I.e, cutting materials correctly and all consumables ready to go before you even think about getting started. Working cleanly is also very important and something you learn working professionally within the industry. I will post some of my top tips of preparation and working cleanly later on this thread. For now a couple of advanced pre-preg tips: Spike rollers - I have not seen these listed anywhere on this forum or the main site, if you do not know what I refer to, it is basically a roller with spikes sticking out. It is important to spike roller each layer of pre-preg that you put down in the stack as this creates small holes within the otherwise solid resin structure for any air pockets to escape during debulking. Debulking - As a general rule of thumb you should always debunk every 2 layers, along with the spike roller this gets rid of air pockets trapped in the stack and helps 'set' the pre-preg in place as you go. Breather tows - A breather toe is simple a short tow of fibreglass placed around the edge of the laminate (in the area to be trimmed), you should place one tow roughly every 250-500mm for large panels/mouldings and smaller distances apply for smaller jobs. This is more important with infusion and Sprint system pre-pregs as it enables the air to escape more easily between layers but also applies to pre-preg as well if you want to do a professional job. Pre-preg curing - I have had a quick look through the easy composites pre-preg offering and was surprised to find fairly basic information regarding the resin systems used and the cure process. Not anywhere mentioned is the recommended ramp rate for cure which is extremely important. As a general rule of thumb anywhere from 0.3C to 2C per minute is acceptable but this really depends on the application and should be specified by the manufacturer. Ramp rates allow the resin to flow correctly eliminating pin holes and voids and it allows the cured resins tg1 to stay ahead of the 'cure'. Dwell times - A dwell is a temperature hold for a set period of time in order for the stack and mould to catch up with the rest of the cure, this all depends on the oven and should be analysed using oven test before curing any pre-preg. Once you have learnt your oven you can apply this to all future cures and can set an appropriate dwell time. That concludes just a few things that I have noticed were never mentioned thus far. I am working on a very detailed pre-preg guide which will include many tips and goes into extreme detail in order to achieve results seen in the most advanced racing yachts/f1/aerospace applications. Please let me know if you are interested in this. Please feel free to add any other advanced suggestions on working with pre-pregs and I will post more up when I have time. Thanks and I hope this helps anyone interested. Hello Mawgan
Welcome to this forum. You really seem to know your stuff and i am really looking forward to you sharing information.
But I must say "Down Boy" some of the enthusiasts on this forum are still having trouble getting a perfectly sealed vacuum bags. There is a full range of experience in the membership, some are even professionals like you. I have learned a tremendous amount of information from the EC guys and their videos, and for that I am very thankful. Having said that, I took note of your tips on your debulking, spike application, breather tows and think that this makes good sense and will remember that in the future. I have never heard of this spike tool before. Can you show us some pictures?
Fred
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mawgan
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Hi Fred, Thanks for your question. I will take a photo of the spike rollers that we use and put it up this week, I'm not sure exactly where you can buy them from as we order through a company called Monks & Crane who supply all of our workshop consumables (like rollers and handles etc) but there must be an online retailer that will sell them. I have also attached some photos of some Carbon fibre skateboards that I have produced, they utilise a vertically laminated bamboo core with Carbon fibre/glass fibre composite and we mill them on our CNC machine. The boards in the photos are produced using wet layup, I have also made them with pre-preg, etc.
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Airship-Jim
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Hi Morepower. I like the details you are providing for the equipment to make up an oven for working with pre-pregs, I am hoping you will be putting up some pics of your finished oven designs and hope you are open to a pm to discuss helping me build my own in the near future when I am ready to have a try at pre-preg carbon production. Jim
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