How thick of the boat mold ?

want develop a new model of 21ft fiberglass fishing boat now make the molds first. We want the molds to endure 6years, evey year release about 20sets good boats. What's the thickness of the mold is needed ?
Our plan is 21layers 350g/㎡ mats, the first four layers are Vinyl resin, others are polyster resin. gelcoat thikness is about 0.95mm , so total thickness is about 19mm.
Are those enough ?
Or what more should we do ??

 

Is 0,95 mm gelcoat thickness recommended by your tooling gelcoat manufacturer? I doubt.

Also, why use 350 gr/m2 CSM throughout? The last layers can be made of thicker mat, to save on labour.

Thickness seems to be OK, but make sure you add enough bracing. On hard points you can laminate it to the mould (chines, keel, flange) but on surfaces either do not reinforce, or embed reinforcing in plenty of flexible putty. (MS Polymer)

 

HAVE BUILT MANY MOULDS AND USED A COUPLE OF LAYERS OF 4 MM CORE MATT WITH GLASS BETWEEN TO BUILD THE THICKNESS FOR THE LAST 2/3 TO GET YOUR THICKNESS THE CORE MATT !
HELPS TO PROTECT THE MOULD FROM IDOTS THAT HIT THE OUTSIDE OF THE MOULD WITH A RUBBER HAMMER !!
19 MM IS A REALLY THICK MOULD SPECIALLY FOR A BOAT THAT SIZE 12MM TO 15 MM IS MORE LIKE IT !!!
MAKE THE MOULD A LITTLE THINNER AND USE A BETTER STEEL FRAME OUTSIDE !. MOST MOULDS IVE MADE THE WATER LINE OF THE BOAT IS PRETTY CLOSE AS THE POINT OF PIVOT !! AND A GOOD PLACE TO START !
AT EACH END OF THE MOULD I ALWAYS HAVE A 150MM WIDE X 100 MM HEAVY BOX SECTION ABOUT ONE METRE LONG TO MOUNT THE PIVOT TO!! STANDS, THE BEST IVE SEEN HAD A SLIDING TUBE IN A FRAME AND A SMALL CHAINBLOCK AT THE TOP TO RAISE AND LOWER EITHER END SO ONE PAIR IF STANDS CAN BE USED ON ANY MOULDS !

 

After the male molds ready we spray the gelcoat, about one hour later spray another time. About 4hours later laminate the first layer, one day later find the bubble and handle them then second layer with vinyl resin, four days four layers, then three layers one day.