Since i have limited space i was wondering if i could make a
Cocktail fig tree by grafting 4-5 different kinds of figs on 1
(Black, white, big, small) but all will be right for my zone (6B)

you could do that or  brade them together .i think it's called pleeching  . do a search i think there are some threads on that

Yes you can.  You can also grow more than one tree in the same hole/container.  Twist, or, braid the still green trunks together, and train into a single stem tree.  The branches growing from the top end will carry the different varieties of figs.  Just make sure the varieties are all equally hardy.  Eventually, the individual stems will start to fuse together.  This process is called "pleaching".  There are a number of threads on this forum that describe just this sort of thing....some very recent postings too.

I have 7 small "Black Mission"  treelets that were twisted together into one, single stem.  I did this last year.  As they continue to grow throughout this coming season, I will continue to twist and tie the new wood, while still green.  It will take a number of growing seasons to develop a nice, fat,"trunk". 

Without a doubt...it can be done, and it has been done already.  Check out the You-Tube video: "Pleaching a Fig tree" Dave Wilson, as an example.

Good luck, and have fun.

Frank

One thing to be cautious of is different varieties grow at different rates.  If you graft several varieties onto the branches of one tree, you may end up with a lop-sided tree or continually prune some of the limbs to keep the tree balanced (the tree will only get as big as the slowest limb allows).  If pleaching, it will be difficult to braid the trunks if they are growing at different rates.  Another option which will help ease some of the issues is to grow them individually as single cordons (a form of espalier).

Grow as a single trunk tree.  Allow for branching all the way up the trunk.  At the end of the season (or before bud break on the following season) cut all the branches back to one or two nodes.  Repeat this each year.  Conceivably, you could fit 4 varieties in a 2-3' square (and possibly even closer with proper pruning) or in a 6' row.  If one variety grows slowly, the others can be allowed to stretch out a bit more until the slow once catches up.  I have a small space project that will require many espaliers to accomplish.  This method is very intriguing to me.  I imagine after several years the trunk/limbs will look extremely interesting without leaves.

If you go the pleaching route should you use something to separate the various root zones? I was thinking maybe 3 cookie trays at 60 degree angles to split into 3 root zones. Once they are older and bigger there will be some competition, but at least each tree will get a year or two without fighting its neighbors.

I think pleaching is a better idea for a nice male, like one of those B Mad seedlings, with Zidi or Kalamata or some other awesome Smyrna fig.  Of course, you have to arrange for the sexual activities.

Otherwise, I think grafting is just a better idea.  Tree grapes, Tree wisteria, pleaching, espaliers, most of these things are a demanding waste of time unless you *specifically* need the feature.  Otherwise, unless you're the type of person that also like bonsai, I wouldn't say pleaching is advisable. 

All great ideas for growing fig trees in limited spaces.  Check out the Japanese methods of fig culture too.  There are links on this forum. 

Any training methods, whether grafting, pleaching, espalier...are all labor intensive.  Pick your poison.

With an open mind, and a sense of adventure, all these methods will be fun to try.

Frank

Thank you very much guys for the information