 |
Matronics Email Lists
Web Forum Interface to the Matronics Email Lists
|
| View previous topic :: View next topic |
| Author |
Message |
Michel
Joined: 10 Jan 2006
Posts: 966
Location: Norway
|
 Posted: Sat Mar 17, 2007 1:03 pm Post subject: Resin WAS: wingtip crack |
 |
|
On Mar 16, 2007, at 9:51 PM, Noel Loveys wrote:
| Quote: | Boat construction as you said uses a lot more resin.
|
It may be so, Noel, but do you have some figures? The way I understand
it is that GRP (Glassfiber Reinforced Plastic) construction where the
resin used is polyester, requires 70% of glassfiber and 30% of
polyester. Less resin and the glassfiber won't be enough impregnated.
More resin and it won't help strength more than an extra coat of
topcoat would.
Those are not my figures but those from engineers working for reputable
certification societies such as Lloyds of London.
Admittedly many "home-building" yachtsmen will use more resin than
necessary, but that could also happen with a home-building airman,
couldn't it?
Cheers,
Michel
do not archive
| | - The Matronics Kitfox-List Email Forum - | | | Use the List Feature Navigator to browse the many List utilities available such as the Email Subscriptions page, Archive Search & Download, 7-Day Browse, Chat, FAQ, Photoshare, and much more:
http://www.matronics.com/Navigator?Kitfox-List |
|
_________________
Kitfox 3 - Jabiru 2200 |
|
| Back to top |
|
 |
lcfitt(at)sbcglobal.net
Guest
|
| Posted: Sat Mar 17, 2007 2:03 pm Post subject: Resin WAS: wingtip crack |
|
|
Michel,
When we closed the elevator on the Lancair IV, the Hysol penetrated the
carbon fiber skins through the dreaded pinholes. After curing it looked and
felt like fine sandpaper. These skins were obviously vacuum bagged and
designed to be very light. Granted this was an Epoxy lay-up, but when we
were instructed in the manual to use the bid lay-ups, the recommended method
was to put the several layers of cloth, 2 bid, 3 bid, etc. on a sheet of
polythelene - 3 mil, saturate with resin, sandwich with another sheet of
polyethylene, and roll or squeegee as much of the resin out of the glass as
possible. This was for weight reduction. Then if there was any sign of
wetness on the surface to blot that up with paper towls.
I doubt any of this would hold gasoline or water for that matter. A very
complex procedure in preparing the fuel bays before closing eliminated fuel
leakage - for most.
Lowell
---
| | - The Matronics Kitfox-List Email Forum - | | | Use the List Feature Navigator to browse the many List utilities available such as the Email Subscriptions page, Archive Search & Download, 7-Day Browse, Chat, FAQ, Photoshare, and much more:
http://www.matronics.com/Navigator?Kitfox-List |
|
|
|
| Back to top |
|
|
Float Flyr
Joined: 19 Jul 2006
Posts: 2704
Location: Campbellton, Newfoundland
|
| Posted: Sat Mar 17, 2007 5:10 pm Post subject: Resin WAS: wingtip crack |
|
|
Admittedly many "home-building" yachtsmen will use more resin than
necessary, but that could also happen with a home-building airman, couldn't
it?
Unfortunately yes.
But in processes where the hull is sprayed up as opposed to layed up and
autoclaved a lot more resin is used. This makes the hull more impermeable
to water and of course heavier which is not a problem.
I guess what the insurance industry is getting at is insuring great
strength at minimum weight. This great strength may be needed like the step
for the mast and the structure to hold the keel. That is where the 70/30 or
pre preg comes into play. As a rank outsider to yachting, let alone world
class yachting, I expect that is why the ten meter boats cost tens of
millions of dollars.... And that's not counting the engineering that goes
into them.
The other part of the 70/30 mix (by mass) is also true... With a slight drop
in resin saturation it is easy to end up with serious voids in the final
product that can cause even greater structural weakness. For this reason
most parts made with this accuracy are also tested with ultrasonic equipment
and sometimes even industrial X-Ray to verify the validity of the part.
Even the clamshell cowls on the 777 have a good coat of gel coat on the
exterior to protect them from water permeation and possible delamination.
In fact it has become a bit of a concern, as a very small crack in the
surface of the cowl, as may be occur by careless loading with a lift truck
is a lot more serious than the same bump on a similar aluminium cowl.
The one thing I have noticed missing from this thread is the use of Kevlar
and what the difference between glass, graphite ( carbon) and Kevlar. It
strikes me for a lot of aviation purposes Kevlar would be the superior
composite fabric.
Noel
[quote] --
| | - The Matronics Kitfox-List Email Forum - | | | Use the List Feature Navigator to browse the many List utilities available such as the Email Subscriptions page, Archive Search & Download, 7-Day Browse, Chat, FAQ, Photoshare, and much more:
http://www.matronics.com/Navigator?Kitfox-List |
|
_________________
Noel Loveys
Kitfox III-A
Aerocet 1100 Floats |
|
| Back to top |
|
|
Float Flyr
Joined: 19 Jul 2006
Posts: 2704
Location: Campbellton, Newfoundland
|
| Posted: Sat Mar 17, 2007 5:24 pm Post subject: Resin WAS: wingtip crack |
|
|
We used to consider that the same as making our own pre-preg. After
squeezing the excess resin out of the cloth we could roll it up, still in
its plastic sandwich and put in the refrigerator to slow down the curing.
This was useful if you had to do several layers of different
materials...e.g. carbon and Kevlar even aluminium foil (embedded antennas).
That system makes a good strong part but one that is also permeable by
water... and I guess gas. What I found really interesting is when you
vacuum bag this stuff you will be surprised by how much excess resin will be
pressed out by the bagging.
Noel
[quote] --
| | - The Matronics Kitfox-List Email Forum - | | | Use the List Feature Navigator to browse the many List utilities available such as the Email Subscriptions page, Archive Search & Download, 7-Day Browse, Chat, FAQ, Photoshare, and much more:
http://www.matronics.com/Navigator?Kitfox-List |
|
_________________
Noel Loveys
Kitfox III-A
Aerocet 1100 Floats |
|
| Back to top |
|
|
|
|
You cannot post new topics in this forum
You cannot reply to topics in this forum
You cannot edit your posts in this forum
You cannot delete your posts in this forum
You cannot vote in polls in this forum
You cannot attach files in this forum
You can download files in this forum
|
Powered by phpBB © 2001, 2005 phpBB Group
|
Get Email Distribution Too!
FAQ
Search
Memberlist
Usergroups
Register
Profile
Log in to check your private messages
Log in
