Today's Message Index:
----------------------
1. 02:35 AM - Composites and mold work (WurlyBird)
2. 05:52 AM - Re: Composites and mold work (Mike Chaney)
3. 08:41 AM - Re: Composites and mold work (Guy Buchanan)
4. 09:53 PM - Re: Composites and mold work (WurlyBird)
Message 1
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| Subject: | Composites and mold work |
I am sure there are some people on here with a good amount of experience with composites
and I have a few questions for you. I am looking to make a few parts
for my plane when I get home and I want to play with composites and molds.
One of my biggest concerns is with preparing a mold properly, everything I have
been reading involves waxing the mold with several layers and then spraying with
a mold release. Is there any type of mold release that skips the waxing step?
I am considering using some molds with a lot of sharp inside corners so
I am concerned about not getting enough wax on and a spray would be much more
convenient.
There are countless resin combinations available. Are any of them better suited
to mold work? I plan on doing some work with carbon fiber for aesthetics, are
some resins better for this as far as coloring goes? I have seen some resins
claim to be more clear then others. I have also seen mention of UV protection.
Still trying to figure all this out so any insight is appreciated.
Does anyone have a preferred method for pulling a plug from an existing part?
The techniques I have read most about and am leaning towards is gel coat painted
over the part and then backed with a two part mold putty or fiberglass for
strength.
I am sure I will think of more of the questions rolling around in my head after
responses. In the mean time thanks for any input.
--------
James
Kitfox 3 / 582 / 70" IVO 2 blade GA
50 hrs on the Fox in between deployments,
now she lies in wait
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=327758#327758
Message 2
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| Subject: | Re: Composites and mold work |
James
-
Check out www.fibreglast.com for information concerning composite work.-
They are a supplier of products and they also have a section on this websit
e with demonstrations.- I've ordered from them in the past.
-
Mike
-
Kitfox IV
Jabiru 2200
--- On Fri, 1/21/11, WurlyBird <james.t.trizzino@us.army.mil> wrote:
From: WurlyBird <james.t.trizzino@us.army.mil>
Subject: Kitfox-List: Composites and mold work
l>
I am sure there are some people on here with a good amount of experience wi
th composites and I have a few questions for you.-
--------
James
Kitfox 3 / 582 / 70" IVO 2 blade GA
50 hrs on the Fox in between deployments,
- - - now she lies in wait
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=327758#327758
le, List Admin.
=0A=0A=0A
Message 3
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| Subject: | Re: Composites and mold work |
On 1/21/2011 2:32 AM, WurlyBird wrote:
> One of my biggest concerns is with preparing a mold properly,
>
I've never seen a reliable mold release that's a simple spray-on. I and
the professionals I've worked with have always done 6-8 layers of wax
plus PVA mold release. Done correctly you won't have corner build-up.
You'll want to minimize sharp corners, particularly for hand-laid parts.
The various woven goods just don't like to turn corners very sharply so
you'll be forced to vacuum bag. Otherwise, you'll have to use a milled
fiber build-up (fillet) in the corner and have the cloth turn inside
that which leaves the corner material relatively weak and not very
aesthetic.
> There are countless resin combinations available. Are any of them better suited
to mold work? I plan on doing some work with carbon fiber for aesthetics,
are some resins better for this as far as coloring goes? I have seen some resins
claim to be more clear then others. I have also seen mention of UV protection.
Still trying to figure all this out so any insight is appreciated.
>
The resin you use for tooling depends on how you intend to cure the
part. In general you want a very long pot life and slow, low temperature
cure for tooling because molds are thick and relatively unstable. If you
intend to heat cure the part you may will want a tooling resin that you
can post cure at an elevated temperature so it remains stable when you
cook the part. See
http://www.ptm-w.com/dynamicdata/data/docs/pt2520%20bulletin.pdf for a
likely tooling resin.
For parts I like the System-Three Silver Tip series for clarity. You're
right that some are clearer than others. You hint that you'll be leaving
the part natural. For UV protection I rely on the clear-coat I use over
the cured part. I use Stirling urethane clear coats because they're
very, very clear and spray on nicely. Expensive, though. I saw that they
have clear gel-coat now so I suppose it's possible to pull a "finished"
part from a tool, though I've never seen it done and don't know how
clear clear gel-coat is.
One more note on clear carbon parts. As you probably well know black
surfaces get quite hot in the sun. It's possible for black painted steel
to get up to over 250F in the sun. You're clear-coated carbon part will
also get quite hot if it's exposed to direct sunlight. This means your
part will have to be cured at least somewhere near the service
temperature so it doesn't get all soggy in the sun. This means your tool
will have to be able to withstand an elevated cure temperature without
getting all soggy. When I did my clear carbon glare shield I cured it at
140F on the tool using a black bag and hot air blower, then I post cured
it at 250F in a crude foam insulation oven with hot-air blower.
> Does anyone have a preferred method for pulling a plug from an existing part?
The techniques I have read most about and am leaning towards is gel coat painted
over the part and then backed with a two part mold putty or fiberglass for
strength.
>
You've got it, though don't forget the mold-release. ;-)
Guy Buchanan
Ramona, CA
Kitfox IV-1200 / 592-C / Warp 3cs / 500 hrs. and grounded
Message 4
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| Subject: | Re: Composites and mold work |
Thanks for the great information. Here is the first followup question.
What does baking a composite part do to the build up?
Does heating the resin while it is curing cause it to more thoroughly cure? From
the way you phrased it it sounds like if you expect your part to be exposed
to 200 deg in use then it should be baked at a minimum of 200 deg during build
up, is this about right?
I do plan on leaving some of the parts natural. If I get the HKS when I get home
I am going to need a new instrument panel and I figure it might as well be
carbon or carbon/kevlar. Light, functional, and sexy, you cant beat it. With
the Kitfox being as low tech and old school as it is, I anticipate that the carbon
on the dash will look a little out of place so there will need to be a little
carbon here and a little there just to balance it out aesthetically. I
am conceiving a part that will be a LOT of sharp corners but I plan on getting
into bagging and maybe even infusion. If the part I have in my head works out
I will be telling you all about it, until then it is hush hush.
In case anyone else has been toying with the idea of bagging but can not find a
reasonable set up, check this out:
http://www.veneersupplies.com/
http://www.joewoodworker.com/
Joe Woodworker has designed and has free plans for venturi style vacuum press and
vennersupplies sells the kit. This set up has the benefit of having a vacuum
reservoir that can easily be made a little larger and even as published should
be great for dash sized projects.
--------
James
Kitfox 3 / 582 / 70" IVO 2 blade GA
50 hrs on the Fox in between deployments,
now she lies in wait
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=327856#327856
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