Master pattern work in Perspex instead of Ureol

[Scratchbuilder]

Hi, having tired of the dust from Ureol, I thought a model aircraft might be a bit easier to do in Perspex. I place in Wickford, Essex supplied quickly and here we are.

wing, tailplane and fin/rudder. Bandsawed out and filed to outline, the tailplane rasped and filed, ready for a final scrape to finish, scraping being something we don't do nearly enough.

The beauty of Perspex is that it keeps perfectly straight and carries a very crisp edge, so panel lines and the like are always as sharp as they can be.

Cheers,

Martin

[Jon Kunac-Tabinor]

Hi Martin - isn't perspex quite brittle? Certainly I know from experience that you have to have the patience of a saint to drill it!

Just wandering what tools you use to work it?

cheers

Jonners

[Scratchbuilder]

Jonners,

I'ts brittle in a way, as in, if you try bending it. It can also chip if you cut it unsupported.

But I always saw it either in the bandsaw or well supported in the vice, where I cut it with a junior hacksaw close to the jaws.

To shape it I currently use rasps to really chew it off, then smooth it off with a 2nd cut hand file and Swiss files. I also have some of those diamond dust small files available from a well known alternative supermarket chain for a wicked £9 a set!

Wet and dry papers to finish it off and I also scrape with a variety of edge tools, some home made from old Swiss files and ground into chisels of different shapes. Pretty much the same tools I always use, from brass to styrene, including Milliput and wood.

If I made a glider wing that long in Ureol, it would tend to bend and deform generally as Ureol doesn't like to be too thin.

Nothing short of metal will hold an edge like Perspex either. It is a bit tough to get down to thinner sections like trailing edges, so I also have a disc sander I built up years ago from Picador parts, alas no longer available.

I know that all the early Matchbox and Corgi Toy patterns were done in Perspex.

So far, I'm enjoying working with it. But no, you can't use it's perspicacity to read the drawing through....Refraction is your enemy!

Cheers,

Martin

[regulus]

Have you ever tried using RenShape? I don't know who stocks it in the UK, but the following source gives you an idea of the different types available. I use the Renshape 460 and it takes a decent edge, scribes without chip-out, and is much softer than acrylics or other hard plastics. Not too soft, and without grain, it is very stable dimensionally.

http://www.freemansupply.com/RenShape460MediumH.htm

[heloman1]

Hi Martin - isn't perspex quite brittle? Certainly I know from experience that you have to have the patience of a saint to drill it!

Just wandering what tools you use to work it?

cheers

Jonners

Hi Jonners, you can't just drill Perspex with a standard twist drill ground for metal, you have to 'back it of'. That is take some of the cutting angle off, to do this touch the cutting surfaces of the drill bit on a grinding wheel until you have about 1mm of cutting edge at half the angle you would set for metal. Some lubricant is always a good idea too, water with dishwash liquid does the job.

Don't try the cheap stuff either (cast sheet acrylic) go for Perspex, slightly more expensive but worth the extra cost.

Colin

[Scratchbuilder]

Lee,

I have persisted with Perspex for the wings, but gave up and used Ureol for the fuselage. Ureol is the same as Renshape, btw. Lots of different grades.

But the dust from Perspex is not as friendly as I'd hoped, especially off the disc sander which tends to throw it up in a cloud due to the fan effect.

I think we'll go back to pearwood or similar for wings, but for the Grob glider wings, Perspex was the only thing for certain stiffness and it also took scraping for the undercamber very easily.

Martin