Hi guys

My question is this. I have tried the prepreg and each time I get pinholes.

My problem may be of my own making. I have 2 vacuum pumps. The oil  bath works to absolute 29.9 HG.

I am reluctant to leave this running over night for fear of burning it up.(Warren said it would be OK I but haven't tried this yet)

My other vaccum pump will only run at 24 HG but is designed for 24 7 running. It is a air vane type.

It is this pump that I have used with both of my preprg tests. Is 24 HG the problem???

I haven't done another test yet.

Thanks

Fred  

Not pulling full vacuum certainly sounds like the issue.

If your pump is our Composites Vacuum Pump  then you will be absolutely fine to leave it switched on over night while you put the pre-preg through its cure cycle.

Warren Penalver
Easy Composites / Carbon Mods - Technical Support Assistant

Hi,

 

I find that if I use a hot air gun on the prepreg to warm it up as I lay it, the prepreg becomes tacky and makes better contact with the surface.

It helps drastically when laying in complicated shapes and up sides as it sticks in place and holds in corners. 

When I cook it under vacuum I take it up to 50 deg for a couple of hours, then around 120 deg for an hour still with vacuum on.

I find running at 50 deg makes the resin run giving a good finish.

 

It works for me.

But just try it.

 

Good Luck

Hi Warren

I don't have your pump but mine looks exactly the same. I assume these pumps all come from the same manufacturer with different names attached. Your is oil bath? correct? So I assume I will be Ok as you suggest.

I will try agin with full 29.9 vacuum.

Thanks for your reply.

Fred 

Thanks for the tip.

When you say 50 deg do you mean Celsius or Fahrenheit? ( surely you mean celsius?) 

Fred

Hi Fred,

Yes Celsius.

As I said it works for me.

All the best

Hi Warren

I did my second test and used full vac and the results were near perfect, just a few pin holes.

So low vacuum was the problem for sure.

Thanks

Fred 

Hi Fred, good to hear your getting better results Pre preg is the next thing on my "to do" list. How are you finding using it?

Hi Warren

Like everything you have to get used to it. I am getting more relaxed using it now. I really like how it sticks to where you put it and the unlimited time you have to work it. I also like how little work it is to prepare the stack. No peelply, no infusion mesh and no resin to mix and infuse.

I tried my 3rd test and seeing I have an autoclave I used it. (yes I know it isn't needed or necessary but I used it anyway)  

I used full 29.9 HG vacuum          212 fahrenheit  temp       80 PSI pressure   maintained for 6 hours.

I was delighted, the part was absolutely perfect and so densely compacted.

I think for my 4th test I am going to follow the advice of a previous poster who said to allow the resin to flow at a reduced temperature 50 c for I think he said 2 hours then at  full temp. (no autoclave this time)

Fred

Prepreg really sounds interesting... it should be the easiest way to make composites, but were do you stock the fabric? do you need a big freezer?


Alessandro