---------------------------------------------------------- Europa-List Digest Archive --- Total Messages Posted Fri 05/29/20: 2 ---------------------------------------------------------- Today's Message Index: ---------------------- 1. 01:45 AM - Post curing, My Saga (Tony Renshaw) 2. 07:36 AM - Re: Post curing response (Kelvin Weston) ________________________________ Message 1 _____________________________________ Time: 01:45:17 AM PST US From: Tony Renshaw Subject: Europa-List: Post curing, My Saga Gidday Bud, Phil, Pete, Kingsley, and co., Post curing, what a headache.! The Ampreg 20 by Gurit as Bud said requires post cure to gain its full strength, nevertheless of course it gets hard, goes rigid at room temperature and years later with fluctuating temperatures, one could think its ok. My conclusion is that the 50 degrees for 16 hours is mandatory if you want the full design strength, however like all certification requirements there are safety factors you eat into or make obsolete if you dont. The post cure increases one of the strength characteristics by 45 %, thats a lot! So, Im of the view you can post cure anytime after construction and 20 years of fluctuating temperatures unless they are probably up over 80% of the desired temperature, repeatedly, and for extended duration each heat cycle, wont achieve the same. Ill be honest, my flight controls are that age too. Im worried, they are cooking as I speak, have been for 8 hours, and I have two temperature indicators saying one thing, and a Weber dual temperature food probe saying 10% more, the first 2 in the mid forties, the Weber meat probes, one at 53, the other 54. The temperature sourcing is at the top of the controls surfaces. The actual heater is set for 49 degrees, is mounted 200 mm from the roof, and as it contains the heat sensor I find it hard to believe the temperature could be 8 degrees hotter a couple of feet below the heater, this would be unlikely. Anyway, Ill tell you in the morning when I open the door.... yes, I have been unable to visually monitor anything. If its all melted, keep chainsaws away from me! Bud, I got to read what you said and yet in the master email your response was all gobbly-gook. This used to happen to me with Graham Singletons emails too, I never worked it out but Kingsley sent it through to me so I read what you have said. Thanks fellas, wish me luck when I open the door tomorrow morning. TR ________________________________ Message 2 _____________________________________ Time: 07:36:31 AM PST US Subject: Europa-List: Re: Post curing response From: "Kelvin Weston" Gents The Europa Build Manual calls for a post-cure, see Chapter 37, Page 2, which states: "The first thing that you need to do with your flying surfaces is post-cure them at a temperature between 40 - 50C. This will improve their strength and cook off any remaining volatiles and moisture within the epoxy system. Make a simple oven with foam blocks, timber or sheets and an electric fan heater and cure your flying surfaces for 8-10 hours. Do take care not to get them too hot and make sure that they are fully supported." The Ampreg 20 and 21 datasheets from Gurit shows an initial cure at a minimum of 18C (ideally 24hrs at 21C) followed by an elevated post-cure of 5 hours at 70 - 80C or 16 hours at 50C. The datasheet also states: The post-cure need not be carried out immediately after laminating. It is possible to assemble several composite components and post-cure the entire assembly together. It is recommended, however, that elevated temperature curing should be completed before any further painting / finishing operations. Furthermore, care should be taken to adequately support the laminate if it is to be post-cured after demoulding, and the laminate must be allowed to cool before the support is removed. When post-curing it is recommended to use a ramp rate of 10 degC/hour when heating from ambient to the post-cure temperature, to ensure that the thermal performance of the laminate stays ahead of the oven temperature. Higher ramp rates may result in the resin softening and distortion of the part. The resulting specs with standard hardener for Ampreg 20, 21 and 30 are all very similar and result in a Tg of around: 58C - Room temperature cure (28 days at 21C) 73C - Elevated post cure (16hrs at 50C) The ultimate Tg for Ampreg 20 and 30 is stated as around 98C. Ampreg 21 was slightly lower at 91C -------- Regards Kelv Weston Kit 497 kelv@kdweston.biz Read this topic online here: http://forums.matronics.com/viewtopic.php?p=496570#496570 ------------------------------------------------------------------------------------- Other Matronics Email List Services ------------------------------------------------------------------------------------- Post A New Message europa-list@matronics.com UN/SUBSCRIBE http://www.matronics.com/subscription List FAQ http://www.matronics.com/FAQ/Europa-List.htm Web Forum Interface To Lists http://forums.matronics.com Matronics List Wiki http://wiki.matronics.com Full Archive Search Engine http://www.matronics.com/search 7-Day List Browse http://www.matronics.com/browse/europa-list Browse Digests http://www.matronics.com/digest/europa-list Browse Other Lists http://www.matronics.com/browse Live Online Chat! http://www.matronics.com/chat Archive Downloading http://www.matronics.com/archives Photo Share http://www.matronics.com/photoshare Other Email Lists http://www.matronics.com/emaillists Contributions http://www.matronics.com/contribution ------------------------------------------------------------------------------------- These Email List Services are sponsored solely by Matronics and through the generous Contributions of its members.