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Bending perspex / polycarbonate / plastics

Ed Poore

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Mods - feel free to remove if you feel this is inappropriate but hopefully I can tap into some of the knowledge available on this forum and I know that a few of the notable members here have links with the Hampshire & Isle of Wight Air Ambulance.

The charity has a "pod" which is used for various events, as seen below, in fact I think I delivered it there for that particular event... They have a number of issues, one being it's their old helicopter and it's getting a bit tired from continuous use. It's also pretty heavy because it's the air-frame bolted to a normal trailer which means Cat E to tow, hence why I got involved. Anyway - they're having a new pod built up to mimic the new helicopter and hopefully keep it below the 750kg limit opening it up for easier shifting around the county. The company building it has been having trouble with the front windscreen so this is where you guys might be able to help out.

Does anyone have any recommendations or experience in the areas of pending perspex, polycarbonate or something else that's suitable for a windscreen? It doesn't need to be airworthy, just strong enough to survive being towed around the county and on motorways, and obviously survive little kids!

I have no ideas what budget they have available for this but I was asked by one of the girls in the office because I have a few (as it turns out not quite so) useful contacts. If it can be a Hampshire / nearby county based company then that might be preferable but I think at this point they'd like anything.


I'm pretty sure the new helicopter is a Eurocopter based one like this, when I was last at the base it was just taking off on a night mission when I arrived but I saw the one they were trialling which looked similar but with red paint on.


Thanks in advance for any leads...

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Should have mentioned, they've tried sourcing one :rolleyes:. As it's a fairly new 'copter there don't appear to be any available. The chap in charge of this in HIOWAA says they're not sure if they get broken when removed.

I'm kind of not involved other than I help out occasionally and because of who I work for I had a few avenues to explore. So I'm going on the basis they've tried the obvious, so its time to think outside the box.

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Polycarb isn't very user friendly for bending/moulding. Perspex or one of it's derivatives could be easier to work with. It would need to be thin enough to mould but thick enough to stand upto the job asked of it 2-3 mm? Thinking back to my school days vacuum moulding is possible if you can make a mould and heat the material to be stretched over the mould.

Liteglaze is a glazing sheet sold in diy stores for greehouse/shed window replacement that can be cut with a saw and bent within one axis, if this could be used for straighter smaller pieces.


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If it helps, I believe the K7 Bluebird restoration team had a new canopy moulded and finally fabricated by Bay Plastics. Look up Vacuum Forming then pick up the phone.

I cannot find exact words that state this, but I recall there was some text with the relevant Pictures of the Day, but while they have an archive of the pictures, they are without the caption text. From a Forum post there may have been mentions around Oct 26 2016.

 Some early pictures, when they are creating a pattern, then bending some plastic to apparently form the trailing edge stiffener.




Good Luck

Edited by David Sparkes
Adding K7 pictures.
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Guy Martin 'Speed' showed how to do this to make a canopy for his 24hr endurance bike ride. If I remember it was aply wood box with heat lamps in it. Place in sheet of clear plastic, turn on lights, then vacuum to draw down. Seemed to work and looked very home made.

Edited by B reg 90
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11 hours ago, miketomcat said:

We had some 10mm perspex bent for a sunseeker windscreen I'll try to find out who did it.


I somehow guessed you might have some input Mike. If you could dig up the company that would be superb.

Thanks for the suggestions on the vacuum forming. I'm tempted to give it a shot in the garden, although temperatures at the moment aren't helping matters! Was wondering if a steel frame with a clay forma and then a fire lit underneath might work... I've seen both vacuums and simply flexing it over, perhaps with the inverse of the mould.

With regards to strips, the problem I see is visibility, it might look a bit naff with lines in it. It is life-size after all and thats been part of the problem, the sheer scale. Although not massive it does require a substantial oven...

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I would mold it over the existing windows too but whats to stop you using the existing ones,,,there is a good chance that perspex strong enough to take a hit from a stone at 60mph on a road would actually be heavier than the plexiglass type stuff that you have freely available already.

as regards temperature its approximately what an electric bar fire would produce at a range of about 3cm. You have to watch it really carefully so it doesnt bubble.

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The issue apparently is that there aren't any windscreens available from Eurocopter. I severely doubt we can use the existing windscreen as a forma because its now on standby 24/7. I also think Bond who own the airframe are likely to not allow it.

The charity has spoken to Airbus and Eurocopter and it seems that there just aren't any windscreen available for use.

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I've pinged a text to a mate who (used to) work on helichoppers see if he knows anyone. Could try putting a call in to Fleetlands in Gosport, they might have some keen apprentices they'd put on it.

Other suggestions: They could always ask a local technical college or uni see if they'd do it as a project (an arts & crafts institution might also have the gear). Likewise perhaps asking some of the motorsport places, as they're based at Thruxton they might turn up a few contacts who can form a sheet of polycarb or similar, a-la racing screens... sure I've seen them advertised in Autosport etc.

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After watching too much of the Discovery channel may be a custom fish tank place could help in you cannot find a vacuum moulding place.
As they work with custom shapes in acrylic
e.g. http://www.aquariumgroup.co.uk/aquarium-gallery/custom-built-fish-tank/large-circular-acrylic-aquarium/

must have been heat formed?


" With one of the largest thermo forming ovens in Europe "

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Worth noting the bubble screen mentioned in that Guy Martin thing was not vacuum formed, they just heated the perspex up with it clamped over an oval hole in a board and it naturally "sagged" into shape with just gravity.

As miketomcat also suggested, doing similar by forming it over an existing screen could work. Maybe not over the one that's in-service :ph34r: although I suppose you could protect it with a sheet of polythene or something and then form a buck over the top in relatively quick time, then heat-form the new one over the buck at your leisure.

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Thanks for all the suggestions - I'll start chasing them up when I get a moment which will probably be the weekend...

Might be a bit tricky getting the ovens / heating elements required up to Thruxton - or maybe they can just fly the helicopter into the workshop, it's pretty impressive where these guys can land it.

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