[valleyboy]

I have used West Systems, Aeropoxy, Proline and others for laminating and structural work. Mainly for high power rocketry projects but for all I have used; I will always have West Systems on my work bench. With West Systems various augmenting media available and I have used all of them, I find it the easiest to use and most versatile of the epoxy's I have experienced. The pump measuring system is part of that ease rather than mixing with a scale. BTW: The pumps don't have to be used with complete pump strokes. 1/4 pump of resin with a 1/4 pump of hardener works just fine.

The only bad experience was my fault, mixed up a liter in mixing container rather than having it spread out. It was on a summer day and I was laminating outside in the sun. It was about 3 minutes and my container of activated resin became a sizzling smoke bomb due to the run away exothermic reaction. I thought I could get it spread out quickly enough on the part being glassed but I was wrong

However it does have a weakness and that is a relatively low HDT heat distortion temperature which is an issue with rockets and heat generated from air friction above mach 2 but there are other epoxies available for that application.

I can see it being a concern though with use close to a turbine pipe though. I think most use hysol in that application

[stegl]

Originally Posted by Dutkoski

I’m primarily a polyester guy but I do use epoxy resin when requested. I have used tge Rayplex brand and I have had good results, so no complaints. The West System brand however, is a better product though along with the lesser expensive SystemThree.

However, if you wish to make moulds, save your epoxy and stick with polyester resins, fair less expensive and it does the same thing. All my moulds are polyester and if you count the individual mould sections, I have well over 150 moulds made over the past 25 years. The moulds range for small to ones that are almost 6’ long. The key thing for making moulds is support, I always attach plywood bridges to ensure the moulds do not distort over time. Polyester, like epoxy, will disorder if left unsupported. In open moulds, I normally store them with the original master inserted inside.

Thanks John ; Exactly the point I was trying to make, and only with molds which was one of the questions the OP had.
Although I didn't elaborate quite so much in the exact technique on larger molds. I made no mention on finishing resin to be used for coverings. I am outa here.

[michaely]

Ditto what John and Len have said about using polyester resin - the ordinary stuff at Canadian Tire works - for molds; polyester is cheaper and, in my experience, is less fickle about precise proportions of catalyst/hardener than epoxy and always cures rock hard.

I scanned some of the 'tech tips' on the Rayplex website..... it's good for clarifying terminology and some of the application stuff but in other areas presumes the user is doing production work.... for example you don't have to spray gelcote; you can paint it on a male (or female) mold with brush.

If you go with polyester, you first paint a coat of gelcote (it's like thick syrup) on the prepared (waxed, pva) mold - it provides a cosmetically smooth finish to the female mold/finished part and doesn't show the weave of fiberglass cloth on the finished surface)...... then lay in strips of initially light fiberglass - 2oz? - then resin and heavier fiberglass cloth and/mat to make a rigid female mold.

Bty, before epoxy became generally available in the hobby - decades ago - I made a polyester female mold and pulled a couple of polyester cowls for a large - Robert Switzer - Beechcraft Stagger GS17 ... I never completed the project but kept the molds and cowls ... they remain in great shape decades later.

good luck

[Myzee]

Awwww, exactly what I was looking for. I was looking to see if the experts use polyester for molds, then epoxy for the parts. And the common product I see mentioned here is West Systems so thats what I will use for the parts. All of this is great information!!!!!

When the time does come for me to tackle a plug and mold project, I will definitely be back for more info

[kaptain]

MGS Epoxy is used by many of the guys making Pylon Racers. It has a lower viscosity than West and therefore flows easier, allowing for thinner more precise layups. West is OK, I have used it in laying up fuses, tails and wings and is widely used because its readily available. If MGS was as easy to get it would be my first choice. MGS is available at CST or Aircraft Spruce.

[4*60]

I only used West Systems on a few things like floats with guidance from a couple of gurus but the "pros" around here seem to use it for some pretty major and great projects!

[Dutkoski]

Thanks for the info on MGS epoxy Kevin. I just checked Composite Canada’s website, they carry that brand, as well as all the others. They will ship products too.
I just might order some to try out.

[Myzee]

If you do John, let us know how it works ok? I'm interested to find out myself. I need a few things from aircraft Spruce anyway...might tack this to the order.
Reviews on AS say to call them to avoid the horrendous shipping cost though...hmmm

[David Ford]

I will add to the West systems recommendation, it works for me too. I do not rely on the pumps for measuring. I weigh it and have never had an issue.
Below are 2 pictures, one a cowl mold and its plug, the other are parts from the mold. The parts are stiff and light.
I use this product for most things that need epoxy including sheeting foam wings. I use cabosil to thicken and ground glass to add strength selectively.

[k.fluney]

Dave, nice Estreletta cowls.