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Old Jun 24, 2012, 03:26 PM
Stirring the pot
johannlochner's Avatar
Port Elizabeth South Africa
Joined Jun 2008
4,011 Posts
Quote:
Originally Posted by Fubar 123 View Post
...... only 3 weeks to the Lundy Trip
I would love to join you one day....

Not much work today as most of the time spent was waiting for epoxy to cure!

The split edges came out fine with one or two "hollows" to be filled.
They are very tight and should give a good result.
I'm 1-2mm out on the split line in places, but short of breaking every thing out, I don't know what to do!

Probably will be OK, but it's in the area of the nose where I have some concerns.
I'll fill the spots and worry about it tomorrow!
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Old Jul 11, 2012, 02:27 AM
...missing the PE Slope Rebels
Flying Beagle's Avatar
United States, MI, Manchester
Joined May 2004
3,012 Posts
Quote:
Originally Posted by johannlochner View Post
Not much work today as most of the time spent was waiting for epoxy to cure!
............I'll fill the spots and worry about it tomorrow!
uh....hello ?

how long does it take for epoxy to dry ?

















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Last edited by Flying Beagle; Jul 11, 2012 at 02:31 AM. Reason: one popcorn for each day since the last goldfish post
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Old Jul 11, 2012, 03:13 AM
.....till the wind drops.
Sean Oelofse's Avatar
Port Elizabeth, South Africa
Joined Oct 2006
3,520 Posts
Hehehehehe!
You'll wait for ever for it to dry!....but 12 hours passed long ago for it to cure! ;-)
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Last edited by Sean Oelofse; Jul 11, 2012 at 03:14 AM. Reason: Welcome back to Africa FB!
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Old Jul 11, 2012, 08:48 AM
Building with TLAR precision
Zenmaniac's Avatar
near Madison, WI
Joined Jan 2009
2,611 Posts
Quote:
Originally Posted by Sean Oelofse View Post
Hehehehehe!
You'll wait for ever for it to dry!....but 12 hours passed long ago for it to cure! ;-)
I don't trust anything a Coro builder says about epoxy!

-= Dave
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Old Jul 11, 2012, 12:51 PM
Stirring the pot
johannlochner's Avatar
Port Elizabeth South Africa
Joined Jun 2008
4,011 Posts
Quote:
Originally Posted by Flying Beagle View Post
uh....hello ?

how long does it take for epoxy to dry ?
:
Welcome back FB!
Hope you survived the tornado's and heat waves back home.....

There is a bit of progress!
I have been sidelined by Graham's DLG pod mould the last two weeks.
I also need to order more resin, as I've used buckets of it lately!

Anyway,
The one half has been cast and I'll try for the other half over the weekend.
So far so good.
I just need to clean it up and fit the resin wells.
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Old Jul 22, 2012, 01:52 PM
Stirring the pot
johannlochner's Avatar
Port Elizabeth South Africa
Joined Jun 2008
4,011 Posts
The build continues....
At a sedate African pace.

but hey, I've managed to get all the other "stuff" out the way!
The squaring and filling of the mould takes a huge amount of resin.
There is almost 10l in there!

I'm hoping to get the last sand resin mix in there soon and crack it open by next weekend!
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Old Jul 22, 2012, 11:24 PM
just a rumour
Drusky's Avatar
Joined Jun 2006
876 Posts
10L of epoxy resin? That's got to be pricey! Where do you source your sticky goo and super weave?
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Old Jul 23, 2012, 12:05 AM
Stirring the pot
johannlochner's Avatar
Port Elizabeth South Africa
Joined Jun 2008
4,011 Posts
Quote:
Originally Posted by Drusky View Post
Where do you source your sticky goo and super weave?
You can try Specialist composites here in PE or order directly from AMT in JHB/CT or Durbs.
It's cheaper from AMT by a long shot, but delivery costs are high for small quantities. They also have a larger assortment of items we use in stock. Especially items such as light weight Carbon and Kevlar cloth.
Evan in JHB is also very much involved with the aircraft modelling scene and has a good understanding as regards our usage and requirements.
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Old Jul 23, 2012, 01:41 AM
just a rumour
Drusky's Avatar
Joined Jun 2006
876 Posts
I get the little bits that I use from Specialist Composites.
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Old Jul 23, 2012, 04:34 AM
scratch build everything
DudleyLeRoux's Avatar
South Africa, KwaZulu-Natal, Botha's Hill
Joined Aug 2009
1,218 Posts
Nice work as usual Johann.
I thought I used a lot of epoxy, geez, 10L is epic.
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Old Jul 23, 2012, 06:32 AM
Stirring the pot
johannlochner's Avatar
Port Elizabeth South Africa
Joined Jun 2008
4,011 Posts
Quote:
Originally Posted by DudleyLeRoux View Post
Nice work as usual Johann.
I thought I used a lot of epoxy, geez, 10L is epic.
Yeah, the volume is about 25 cubic litres
so, the rest has to be sand/glass and gel coat!
It is quite a lot...
I don't quite know how to get around the inflation/clamping without squaring it off.
Then there is the warping and twisting issues too...
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Old Jul 23, 2012, 07:56 AM
scratch build everything
DudleyLeRoux's Avatar
South Africa, KwaZulu-Natal, Botha's Hill
Joined Aug 2009
1,218 Posts
Quote:
Originally Posted by johannlochner View Post
Then there is the warping and twisting issues too...
In my rather lengthy discussions with Evan on the subject, specifically around wing moulds, Warp occurs if you are introducing different materials to the layup, like sand, metal bars etc... His recommendation to me was to use "returns" made of the same material as the mould layup. This gives the strength without the warp.

Of course this means nothing when you are building a mould for inflation bladder moulding, since you have to reinforce for internal pressure and hence external clamping force.

Good luck, I'm glad my fuse is long and skinny.
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Old Jul 23, 2012, 02:06 PM
I'd rather be.....
geoffers0_0's Avatar
Bristol, UK
Joined Jun 2008
208 Posts
Quote:
Originally Posted by johannlochner View Post
Yeah, the volume is about 25 cubic litres
so, the rest has to be sand/glass and gel coat!
It is quite a lot...
I don't quite know how to get around the inflation/clamping without squaring it off.
Then there is the warping and twisting issues too...
Excuse my ignorance (following this thread with great interest)

Presumably, having completed the mould face
  • You're back-filling the "b-side" with sand/glass/resin for strength againt the bladder/clamping pressure?
  • Wouldn't it be possible to substitute a form of concrete - for instance glass-reinforced-concrete (GRC) as the backfill.
  • I appreciate that concrete itself would probably not have the required tensile strength without some kind of reinforcement, but GRC is widely used in the construction industry for lightweight cladding etc For example see ... http://www.grcuk.com/
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Old Jul 23, 2012, 02:09 PM
Just fly it!
wyowindworks's Avatar
Cody, WY
Joined Nov 2007
6,915 Posts
Quote:
Originally Posted by geoffers0_0 View Post
  • Wouldn't it be possible to substitute a form of concrete - for instance glass-reinfoced-concrete (GRC) as the backfill.
  • I appreciate that concrete itself would probably not have the required tensile strength without some kind of reinforcement, but GRC is widely used in the construction industry for lightweight cladding etc For example see ... http://www.grcuk.com/
I have tried this and had problems with the bond between the FRP face and the concrete.
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Old Jul 23, 2012, 02:32 PM
Stirring the pot
johannlochner's Avatar
Port Elizabeth South Africa
Joined Jun 2008
4,011 Posts
Hi geoffers0_0
Yeah, I'm currently "filling side B
Adam's right, it's all about the bond.
In composites, you can add the "fibres" as they do with the fibre cement boards using resin as the bonding material. The use of cotton flock tends to be very resin thirsty, but the bonding agent still has the same characteristics as the glass layup and therefore delivers good adhesion.
Sand in this case acts as the filler to give better bulking results per volume. Strength is not the main consideration.
But....
Warping and deflection of the mould part is a real problem.

Hehehe
On my 1st wing mould I stripped it after 24h and watched it curl and deflect with absolute horror!

Now, I've learnt at least one thing....
Let it cure, and perhaps consider some reinforcing bars!
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Last edited by johannlochner; Jul 23, 2012 at 02:37 PM. Reason: Dam, I know I should have put some steel framing in!
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