troyhm

Hi everyone

I have a canopy that I cant get anymore made from lexen. I was just wondering what the best way to make a Mold of the canopy so I can make some fiberglass or carbon fiber later. I have seen moldeling clay at the fiberglass suppliers. I dont want to damage the other canopy at all. Thanks for any ideas

thanks

Troy

Ed Smith

The quickest and cheapest. If the canopy has a flange around it pin it to a flat board. If it does not have a flange around it fit say 1/4 balsa sheet to fill the bottom and back pin or glue it to a flat board. build a box around it about 1/2 deeper than the canopy. Mix up some Plaster of Paris (Hydro Cal)? and pour it in. Allow a couple of days to dry. Pop the canopy out and the result is a female mould. The inside will have to be sealed with paint or anything else that will dry hard and smooth.

The more expensive alternative is to make a mould the usual way by polishing the outside with several coats of mold release wax and lay up a glass mould. Do not use Polyester it might attack the plastic.

If the canopy is supported with a basic frame it can be filled with Plaster of Paris. This will give a plug that can be used to vacuum form other canopies.

Ed S

topstitch

Hi Troy,

I use two methods depending on the final result required...
You can make a mold with epoxy resin and glass cloth/mat, using PVA (poly vinyl acetate) release agent. This gives and excellent female mold for further reproductions in carbon or polyester etc. It is important to use Epoxy, and not Polyester. The polyester will attack some plastics, even through the release agent, the epoxy usually will not.

Or, you could pour casting plaster directly into the canopy for a male mold, which will give a plug suitable for drape/vacuum molding a new canopy in plastic or lexan. With this method, you may have to make a frame, or jig, to hold the canopy from spreading from the weight of the plaster. If the canopy is smooth, a release agent is not required. As with all things, plaster/epoxy etc on a scrap or inconspicuous area to make sure nothing will react!

I hope this helps, or gives you some ideas. Good luck!

Regards,
David

topstitch

Correction: Poly Vinyl Alcohol release .... (not white glue)

troyhm

Hi Guys

Thanks for the ideas. I want to make several canopies using both carbon and fibre glass and even maybe some clear lexen.
I think if I fill the canopy with plaster it will expand way to much. The canopy is about 600mm long by 100mm wide in most places lots of plaster and wieght.

How do you polish up the lexen of the canopy with the mold release wax ? what weight of cloth do you need to use to make the mold ? How do you lay the fiberglass on the canopy what order how many layers ? I know so many questions I want to be able to vacuum bag the canopies into the mold. I have spent a long time making one and used only on a few wings. This is my first fiberglass mold project but I have more to tackle soon. But one at at time.

I was even looking to do a course on fiberglassing etc but couldnt find one

Thanks

Troy

Darrinc

My Feedback: (5)

The most important thing is to practice this with a different canopy, a cheap one that you can buy several just for testing!

One thing that you will want to do is to use a resin with a long pot life, like Pro Systems 125, with 229 hardener, or even 237. (I don't have much experiance with 237) The reason for the need for a slow cure is that you have to watch that your layup does not exotherm on you, the heat building up from too fast of cure would distort the lexan canopy and ruin the shape.

http://cstsales.com/ESProSet.htm

I would try to wax the canopy about 5 times, then a thin coat of PVA. You can try just PVA in one of your disposible canopies. I know people that just use PVA with success. Or try a solvent free liquid mold release like Watershield from Zavax. (they will send out a small sample kit sometimes, tell them I sent you)

http://www.zyvax.com/products-englis...terShield.html

Once the release is done, I would mix up a thick batch of epoxy/cabosil and spread that into your canopy, try to make a consitant 1/8" thickness. This will get very hard and help hold the shape of your mould. I would wait until this has setup some what, (about 12 hrs if you are useing 229 hardener) to start placing in your cloth, just the thickest cloth that will make your bends in the canopy, this prevents voids. Build up about 1/8" of cloth and you should be done. I would wait at least 24hrs from when you finished the cloth befor trying to remove. Once you get the canopy off, you will have to wash your mould with water to get the PVA off.

Just my 2 cents.

Darrinc

My Feedback: (5)

If you want to make carbon and fiberglass canopies, you will have to layup a mold from the outside of your canopy. You will need to have the canopy stiff in order to do this, so I would layup your inside mold for making lexan canopies, then leave this mold in the canopy for when you make your outter mold. Actually, I would make your outter mold before you remove the inner mold for the first time, that way the canopy is down tight on the inner mold. otherwise tou will have to 3M 77 the canopy on to the inner mold.

Use the same procedures as I listed above for inner and outter molds.

The epoxy/cabosil is the same thing as using a face coat, which is just a tough, hard surface that helps you when making your parts later.

Make sure you practice this on other canopies before you start on your irreplacible one. There will be lots of little things that there is not enough space here for me to write out that you will run into, so do not even get near your important canopy until you have made successful fiberglass and lexan canopies from your test canopies!

Remmeber, composite work is at least 90% prep work and 10% layup. The prep work is everything!

Ed Smith

Which is why I suggested stiffening the canopy with a framework.

Ed S

hayman

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