Talk Composites - The Forum for Advanced Composites

Pattern coat primer application

http://www.talkcomposites.com/Topic19102.aspx

By Ian Mantula - 8/28/2015 10:06:17 AM

I've been building my first plug for the air conditioning housing on my Marcos Mantula. While I'm quite happy with the way it has turned out in general I am finding the application of the pattern coat primer to be more difficult than shown in the Easy Composites video. I've tried using a brush and a roller, but can't seem to get to the stage where it only needs minor sanding. There always seems to be new imperfections with each coat.

Maybe the working time is too short. I try to mix accurately using digital scales, but never seem to get a consistency that allows the brush or roller marks to flow out. Any ideas what I'm doing wrong?

Thanks
Ian
By TURK - 11/14/2015 4:43:18 AM

Hanaldo (12/11/2015)
Why are you not filling the low spots with body filler? 




Hi Hanaldo,

Good question,  normally that would be the way to go ........  but at the stage where I'm currently at ( 20 odd coats of pattern-coat primer ) I can't ....... or rather I'm afraid to 'undo' all the work I've already done.

If I were hand laying or bagging carbon fibre I think it wouldn't matter,  but I'm using my plugs as 'tooling plugs' for vacuum forming.  As that process involves subjecting the plugs to high heat,  the build-up of pattern-coat primer acts as a shell if you like,  as pattern-coat primer has aluminium in it.  If I go and fill the low spots with body filler now,  I'll only create weak spots in that heat resistant 'shell'.  I've had issues in the past with thin layers of polyester filler cracking due to heat,  so I really don't want to risk it at this stage,  so I'm having to use the pattern-coat primer as a filler as it were.



As the OP was commenting on the pattern-coat primer as a product,  I thought I had to pitch-in with my findings ........  that is to say,  it doesn't actually do what it pertains on the Data Sheet !

It's seen as a very high viscosity primer almost like syrup,  so a couple of coats of pattern-coat primer and you're done. 
I can assure that is not the case ......... it may become thicker in the last two minutes of it's pot life,  but the initial mixture is more like regular emulsion paint.  



I had to build up my plugs by 2mm as they have to fit inside a bracket,  so with the Data Sheet I concluded that 2 coats of 1mm each would be enough ........ it's taken 20 coats to get to that stage !



Don't get me wrong,  I'm not complaining about the actual product as it's doing what I want it to.  But the Data Sheet information is very misleading  Angry


Next time I'll be looking for a different product,  something much thicker but also very durable as I have to able to vacuum form many many parts from it.




TURK