skatun

Hello
I am looking for a dealer thats sells Mylar and ship international.. I have acsess to a cnc mill which i will use for milling negative moulds in wood for a ds model.. Then I hopefully just can put a mylar sheet on top of it and then put in the vacum bag..
Regards Kim
Norway

dreadnaut

My Feedback: (5)

Go to http://www.mcmaster.com/ and look up catalog page 3313. The four mil (.004 inch) stuff is great for making vacuum bags.

Ed Smith

What are you trying to do exactly? Are you using the mylar as a release film? If so will it not wrinke when the bag forces it on to the form. What is a "ds model"?

Ed S

skatun

Yes I will use mylar as a release film to get a smooth finish.. of course it has to be stiff enough so it dosent wrinkle, but I think that isn't a big problem..

A ds model is model for dynamic soaring...Look at grini.no/ds for more info about ds..
kim

ptxman

My Feedback: (2)

If I understand the method correctly: cnc mill a female cavity mold out of some stable, inert, (ideally less expensive) blank material like high density urethane foam or laminated wood. Then somehow attach the mylar to this mold cavity & use this sandwich 'tool' in the same manner as though it were a prefinished solid metal mold or something. I think in principle this should work OK. Here are some things that you would probably consider:

- the cavity would have to be offset milled deeper by the thickness of the mylar to compensate. So you would be wise to acquire the mylar first

- I think the mylar would have to be permanently bonded to the rough mold substrate in order to handle the releasing forces of pulling the molds apart from the wing layup. If the mylar ripped away every time you parted the mold, that would be a pain. Because mylar has inherant releasing properties (which is why you want it as mold surface to begin with) this might require some attention & experimentation. Maybe roughing the back surface & using a special adhesive (like what?) is required.

- ideally you would vac bag the mylar sheet onto the mold substrate so it gets sucked down uniformly. This may even be a prerequisite in order to keep the mylar shaped around the leading edge area. I think ideally you would want the mylar trimmed to th emold split line in the leading edge area though.

- if elevated temp post curing was being considered, this may not be as suitable a tool

- compound curves would be an potential problem as thicker mylar would not conform. This would have to be dealt with in the tip area especially & maybe between the 2 wing panels depending on the panel tapering. I wonder if mylar woul drespond to heating so it would flow slightly the way some packaging systems encapsulate products?

Id like to see your results, please share if you pursue. I always try new methods on something small to validate the method & deal with inevitable unforeseen challenges that pop up. Maybe consider making a stab mold first right through to part layup vs a wing. Good luck.

CoosBayLumber

My Feedback: (1)

I have a question as to intents also. However in responce to the original question, I obtain mylar at the drafting store. It comes in huge rolls and is the medium of preference today for plans and maps, due to being so transparent. I would think you could locate some locally. Per our standards it comes glossy, or matte, and in thicknesses from .003" to .015"

The problem being is this is pretty ridgid stuff. It does not like to bend nor fold. It will roll, but only slightly.

The other item we have been using locally is referred to as Visqueen. It is a very plyable thick plastic which is layed underneath concrete, just before it is poured. You can actually heat it a bit and it will shrink. It comes in thicknesses of about .008 to .025" and is available at masonry or concrete construction places, and very cheap.

Wm.