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Old Oct 31, 2012, 02:45 AM
a.k.a Maltone
Pat Lynch's Avatar
Australia, NSW, Goulburn
Joined Jan 2005
6,924 Posts
A Plug for plastic cowls.....

The last couple of days have been spent creating vast amount of offcuts, shavings, dust and more swearing
A plug to vacform some cowl parts is being made from 6 laminations of 12mm Craftwood (MDF) glued into two mirror image blocks which were then joined with double sided tape. Slots were built into the plug to allow fitting over the engine bearers so the shape could be checked.
Most of the hacking to shape was done with a sanding bar with 25 grit paper glued to it - not to be waved anywhere near soft block balsa!
Templates were made to check the front-to-back shape and sections sanded until correct. These were marked with a red pen and sanding done 45 deg further round. The bits between the red lines were then rounded and so on until it looked about right. Fine sanding and filling will be done prior to use.
Another couple of plugs are needed for the oil cooler housing on top and the supercharger inlet on the side. Fortunately, the nacelles are identical left and right.......
The plug is about 5X4X3 inches and could also be used to create a female master in fibre-glass for FG cowls if I felt that way inclined.....

Pat
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Old Oct 31, 2012, 02:58 AM
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Spitfire1954's Avatar
United Kingdom, England, East Riding of Yorkshire
Joined Jan 2011
620 Posts
Hi Pat
Certainly creating a masterpiece – congratulations on the prizes, well deserved.
Best
Charles
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Old Oct 31, 2012, 03:19 AM
What's 3D?
trumps's Avatar
Australia, WA, Ellenbrook
Joined Feb 2008
3,316 Posts
The cowl forms are coming along nicely mate, 25grit, wow that is near on roadbase material, wouldn't take much to take too much
with them being such big structures do you think you will need to build any form work inside them, or will they be sturdy enough by them selves?

Cheers
Craig
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Old Oct 31, 2012, 03:25 AM
a.k.a Maltone
Pat Lynch's Avatar
Australia, NSW, Goulburn
Joined Jan 2005
6,924 Posts
Thanks Charles. Craig, the motor mounting plate is about halfway down the cowl so it will be fully supported at the back and midway. The gritty paper I use is off a stash of floor sanding belts left over from a 1:1 build many years ago!
Now I have to add bits on each cowl plug half to stand off the vac former and to form a flange to join the two halves......might clean the workshop up first - mdf dust is revolting - as bad as balsa!

Pat
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Old Oct 31, 2012, 10:36 AM
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Steve85's Avatar
Canada, ON, Kingston
Joined Mar 2004
2,857 Posts
Hey Pat,

You're doing what I have to do for my Lancaster nacelles, canopy and turrets, so please keep posting as you go along. I've never used MDF before as a plug material, so it's all instructional at this point!

Steve
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Old Nov 01, 2012, 12:03 AM
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Modelholic's Avatar
Perth WA
Joined Feb 2007
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Please be careful using MDF for the plugs - and note a dust mask is not a respirator.
When MDF is cut a large quantity of dust particles are released into the air. It is important that a respirator be worn and the material be cut in a controlled and ventilated environment. It is a good practice to seal the exposed edges to limit the emissions from the binders contained in this material.
Formaldehyde resins are commonly used to bind MDF together, and testing has consistently revealed that MDF products emit urea-formaldehyde and other volatile organic compounds that pose health risks at sufficient concentrations, for at least several months after manufacture.[6][7][8] Urea-formaldehyde is always being slowly released from the surface of MDF. When painting, it is a good idea to coat all sides of the finished piece in order to seal in the urea-formaldehyde. Wax and oil finishes may be used as finishes but they are less effective at sealing in the urea-formaldehyde.[4]
Whether these constant emissions of formaldehyde reach harmful levels in real-world environments is not yet fully determined. The primary concern is for the industries using formaldehyde. As far back as 1987 the U.S. EPA classified it as a "probable human carcinogen" and after more studies the WHO International Agency for Research on Cancer (IARC), in 1995, also classified it as a "probable human carcinogen". Further information and evaluation of all known data led the IARC to reclassify formaldehyde as a "known human carcinogen"[9] associated with nasal sinus cancer and nasopharyngeal cancer, and possibly with leukaemia in June 2004.[10]
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Old Nov 01, 2012, 12:59 AM
a.k.a Maltone
Pat Lynch's Avatar
Australia, NSW, Goulburn
Joined Jan 2005
6,924 Posts
I found cutting and sanding MDF in a garage effectively open to wind at both ends a good way of minimising the dust. I agree, a dust mask only stops the annoying aspects of the dust particles (same as I do with balsa sanding). Sadly, our modern environment has so many formaldehyde and other nasty-bearing substances (plastics, glues etc) we seem to be digging a hole for ourselves.(!) - new cars/aeroplanes/carpets almost smell toxic! Thanks for the health warnings and precautions Simon.
Pat
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Old Nov 01, 2012, 03:54 AM
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michaelghammer's Avatar
Denmark
Joined Dec 2004
559 Posts
Hi Pat

The Heinkel is coming along nicely. The quality of your work is very inspiring to us all. Thank you for taking time to post progress reports about this beautiful and interesting plane.

Now a bit of trivia few people know about the Heinkel 111:

The big window hatch above the pilot could slide back and a small windscreen in front of the opening would (automatic?) be raised. The pilot could then raise his seat and fly the plane with his head out in the open. Must have been a feature incorporated to comfort the generations of pilots that were used to fly in open cockpits. The japanese Zero and the american Vought F4U Corsair had the same feature to aid looking past the cowl. Ive never seen a photo of a Heinkel He-111 flown with the hatch open but I did manage to find a photo of a crash landed Heinkel which shows the windscreen in the raised position.

- Michael Hammer
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Old Nov 01, 2012, 04:41 AM
a.k.a Maltone
Pat Lynch's Avatar
Australia, NSW, Goulburn
Joined Jan 2005
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Thanks for the info Michael - I had made the little 'window' in front of the sliding hatch but didnt realise it was an opening windscreen! I may make it open and the hatch slid back just for interest

I hadn't studied this beast in fine detail as at 1/12 scale, I wasn't going overboard with fiddly bits! So little elements as youve just mentioned are a bonus! I haven't even decided on a scheme yet but am always attracted to the standard Battle-of--Britain or Blitz dark green/black green splinter scheme and som coloured fuselage bands and spinners...

I have just vac-formed to cowls so will describe that shortly.

Pat
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Old Nov 01, 2012, 05:32 AM
a.k.a Maltone
Pat Lynch's Avatar
Australia, NSW, Goulburn
Joined Jan 2005
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First Attempt at cowls.

The four cowl halves took about 1/2 hour to make but the plastic sheet I had is a little bit thin. I'll try and get something about 1mm thick - I used .5mm and it thins a fair bit when moulded.

The pictures show the split master on the little vac-form table, then the various stages up to a trial fit on the model. Without any fine finish on the plugs, the surface of the plastic is slightly mottled but easily filled later when painting.

The plastic sheet was just stapled to the wooden frame and heated under the griller until soft! (the oven was well ventilated afterwards!)

The plug makes a handy support for the plastic when cleaning up edges etc.

The cowls would be usable as is but a heavier grade will be better.

Pat
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Old Nov 01, 2012, 06:12 AM
What's 3D?
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Australia, WA, Ellenbrook
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Very nice work mate.
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Old Nov 01, 2012, 08:08 AM
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Gree's Avatar
Sydney, Australia
Joined Jun 2006
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That's a nice vacuum table set up. Home made?
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Old Nov 01, 2012, 08:41 AM
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Bill Smudge's Avatar
United States, KY, Bowling Green
Joined Jul 2011
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Pat quite a project you have going... Great work!!

BTW, make sure when your Vac-u-forming, put the plastic sheet in the vacum machine---not the toaster!!! The smell would be horrible...


Bill
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Old Nov 01, 2012, 11:53 AM
What's 3D?
trumps's Avatar
Australia, WA, Ellenbrook
Joined Feb 2008
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Quote:
Originally Posted by Bill Smudge View Post
Pat quite a project you have going... Great work!!

BTW, make sure when your Vac-u-forming, put the plastic sheet in the vacum machine---not the toaster!!! The smell would be horrible...


Bill
The joys of kitchen vacforming, nothing gets my ballnchain's interest up when I set up on the bench with my setup and start making plane bits with her tools of trade, it isn't always positive interest either!

Craig
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Old Nov 02, 2012, 12:39 AM
a.k.a Maltone
Pat Lynch's Avatar
Australia, NSW, Goulburn
Joined Jan 2005
6,924 Posts
Gree - yes, the vacform stuff is very home-made. Just bits of odd wood/mdf/particle board screwed into a 12X8X3 box with a hole for the vacuum cleaner hose and lots of 1/16" holes in a 1" matrix on top. A strip of door weather-stripping is stuck around the edge to help seal when sucking. Like many of these 'exotic' techniques, it's not the gear that's important as much as developing the skills to use it. I'm not scared of it now but had a lot of failures when starting out

The cowl halves were cleaned up and the edges joined with a strip of plastic 3/8 wide inside the joint. Plastruct glue (MEK) was wicked into the clamped joints.
A 5mm ply rear former and a front ply ring were epoxied in place after roughing up the styrene with a coarse file. The glue in the front had some micro balloons added to make sanding to final shape easier.

The cowls are now MUCH stronger than I first thought and will certainly do for this project. Three screws hold it in place from behind the main firewall - accessed through the UC bays and the battery hatches.

I may make the battery hatches from balsa and the UC fairing from a vacformed part. Still thinking.........

Pat
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