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tonyrenshaw268(at)gmail.c
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 Posted: Sat May 30, 2020 5:23 am Post subject: Europa-List Digest: 2 Msgs - 05/29/20 |
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Gidday,
Well with much trepidation and about a 4 hour reduction to 20 degrees Celsius ambient temperature I opened up my little refrigerator panelled camper van box thingy and FaceTimed it to Kingsley Hurst to share in the anguish. It worked, it all survived and my straight edges are all still 100% as they were before, straight.
Thanks for the input & advice fellas, now to build a box for the wings and moreso work out how best to distribute the heat around the wings, using the same heater but an entirely different shaped box, less amenable to a circular airflow.
Tony R.
| Quote: | On 30 May 2020, at 4:39 pm, Europa-List Digest Server <europa-list(at)matronics.com> wrote:
*
==================================================
Online Versions of Today's List Digest Archive
==================================================
Today's complete Europa-List Digest can also be found in either of the
two Web Links listed below. The .html file includes the Digest formatted
in HTML for viewing with a web browser and features Hyperlinked Indexes
and Message Navigation. The .txt file includes the plain ASCII version
of the Europa-List Digest and can be viewed with a generic text editor
such as Notepad or with a web browser.
HTML Version:
http://www.matronics.com/digest/digestview.php?Style=82701&View=html&Chapter 20-05-29&Archive=Europa
Text Version:
http://www.matronics.com/digest/digestview.php?Style=82701&View=txt&Chapter 20-05-29&Archive=Europa
================================================
EMail Version of Today's List Digest Archive
================================================
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Europa-List Digest Archive
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Total Messages Posted Fri 05/29/20: 2
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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 <tonyrenshaw268(at)gmail.com>
Subject: 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: Re: Post curing response
From: "Kelvin Weston" <kelv(at)kdweston.biz>
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(at)kdweston.biz
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brian.davies44(at)gmail.c
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| Posted: Sat May 30, 2020 7:12 am Post subject: Europa-List Digest: 2 Msgs - 05/29/20 |
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Is yours a classic Tony?
Regards
Brian Davies
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