antennahead

I would like to make a plug from my new heli canopy. this canopy is made from bleach bottle plastic. I have never done this before and am not sure what material to use to make a mold and cast a new plug to eventually make a fiberglass canopy. since the canopy is flexible, do I need to fill the canopy with something to keep it stiff,especially at the rear of the canopy? if so what could I use?

I assume the mold would be a 2 peice silicone mold with the parting line down the center leaving the back open?

Once the mold is made, What material would be used to make the plug from ?

Can this be done without destroying the original canopy?


I have been reading alot on this forum about materials and techniques but I am not sure how to make a plug from an existing molded item.
Thanks for any help.

Ed Smith

You have the plug already, the canopy. Using the canopy as a plug a mold can be made. There are two choices here. Either way some sort of internal structure to stiffen and support the canopy will be needed. This structure can be balsa formers.

One method would be to fit a parting board around the canopy along the centre line. This can be a chore.

I would split the canopy along the centre line. fit the two halves along the centre line to a flat board .

In both cases the back end can be left open, hence the need for stiffeners. The pictures do not show the underside of the canopy. Are there any reverse angles that would lock the canopy in the mold.

If you agree to the foregoing I will describe the next step.

Ed S

antennahead

After my first post I was thinking that I could use the canopy as a plug. adding some braces to the inside should be easy to do. here is a pic of the bottom of the canopy, I don't see anything that might keep it from releasing from the mold. I have made some basic silicone molds that were filled with resin for static model cars, I think the casting kit I used was fom a company called alumilite.........or something like that. I know it's not the same but it gave me a basic undestanding of making molds, just need a better understanding of the materials needed in this aplication. So after I have a mold,assuming two piece, split at the centerline of the canopy (lengthwise). I would lay up fiberglass in both haves of the mold,then clamp them together and then lay in a thinner strip of fiberglass at the parting line once both mold halfs are brought together........

Ed Smith

That would be the procedure. With the back end open applying the joining strip around the seam would be fairly easy. I realise that strength is not an issue for a canopy. I join my fuselages in the mold before anything has cured. I trim one half of the layup flush with the mold edge and leave a 1/2" flange on the other. I carefully close the mold tucking the flange inside the other half. I brush the flange down and the process is complete with everyting curing together. Since I started doing this I have never had any cracks along the join.

Ed S

antennahead

Ok, I think I have a pretty good idea what to do once I have a mold.............just having a hard time deciding on how to go about making the mold. What can I use to make the parting flange? can I use some thick styrene sheet plastic, or will I need to use something stronger like some sheet aluminium? once I have the parting flange made, do I fill the open part of the plug with clay to keep the mold material from flowing into the back of the plug? What material would be used that would then become the mold? I have seen some threads on here using a plaster type material.....I would like to use something a little more durable as I plan on making a few canopies from this mold if things turn out ok. and thanks for answering some of my basic and mabey stupid.........or basicly stupid questions.

Ed Smith

Go here and explore the site. It lists all of the various materials and offers instructions in their use.

http://www.fibreglast.com

antennahead

thanks for the link Ed, I also checked out cst's website as my LHS stocks all of the west sytems products and CST's line of materials as well. After reading CST's how to make a mold I do have on question, instead of going through the hassles of waxing and subsequent polishing of many layers of wax,Then using a liquid release aget, can I substitute a thin layer of petoleum jelly without any adverse affects?

davidfee

Wax and PVA are so cheap compared to the fiberglass and epoxy you'll be using for the mold and parts... so why cheap out? It's not that much work to do it right... and it will save you a lot of pain and frustration.

-David

Ed Smith

I think I have mentioned many times that the finish on the inside of the mold will be determined by the finish on the outside of the plug. What sort of finish do you think you will get with vaseline smeared all over the plug?

Listen to David and and pay attention to this.

To get good results with fibreglass work there are no cheap or quick shortcuts!

Ed S

antennahead

Ok, i'll wax and PVA...........now have to find a different use for the vaseline................ anyway, I have assembled all of the needed components except for the wax, PVA, and a suitable material for the parting flange.