Got a flat peice of carbon to make, using 18 mm mdf going to high build primer it then blocking down and mold relase.
Will this hold vacuum ? Any tips if not dnt want to faf about and not work 
Pay a visit to your local glazier. They may have some scrap windows instead.
Carnt mate it needs a 90 degree angle at one side to much messing with glass
Could you perhaps cover the MDF in bagging material? Saves on having to seal and finish the MDF
I lined some right angle steel with it and it worked a treat! Needs to be tight to avoid wrinkles.
Could get a local metal shop to bend you a piece of sheet metal. would save so much time and trouble and wouldnt cost much. but to answer your question, it will be able to hold a vac without leaks, but its always good to do a leak check first time before making the part to be sure
Leak check is standard. I jus didnt want to prep mdf then it be a waste of time and already got it any way 
ill post results
No MDF won’t hold vacuum without a bit of work, plus the vacuum on one side can make the sheet bend.
The easiest way is to put the whole thing in a bag. Then the vacuum forces are balanced and there is no worries about leaks. Sure it might cost more in bag but what will it cost you in time to look for leaks or to redo it.
He’s putting a high build primer on it, it will hold vacuum just fine. unless the bag has tension on it from not enough pleats it will not distort the MDF(assuming hes using 3/4" thick).
18mm mdf min. with a frame made from 2"x4" the mdf will not bend ill post up in a thread as i do it
From the two piles of rubbish sitting outside my office from my old FSAE team, MDF with high build duratec leaks. And they aren’t the first time this year they have tried to get MDF with duratec to hold vacuum but with the same results. Why wouldn’t you just eliminate the chance of leaks by putting the entire sheet into a bag, it will save a lot of time and money.