"Blowing it up" is much more fun! But seriously, the foam laminate that was used in most early TheMightyHobie18's decks is low-density polyurethane, which has a few "poor" qualities for a foam core laminate. 1. It does not take any impact well (it will crush and delaminate). 2. It has a relatively low thermal capacity so that if exposed for long periods of time in a hot sun the thermal capacity of the foam can be exceeded and it will once again delaminate. 3. Although it is promoted as a "non interconnected cellular structure" it will absorb and hold moisture within it's structure, even at times drawing it from out of the air, if it is not permanently and completely "sealed" (and as shown over many years in many types of boats, to permanently seal it is almost impossible). The biggest problems with “injecting” resin back into the delamination are 1. Ensuring that the whole area of delamination is covered, and 2. If the foam is wet, the resin injected will not bond with the foam and/or the laminations. When polyurethane is internally “wet” it is difficult to impossible to dry it out.
We have successfully repaired delaminated TheMightyHobie18 decks in the past, but the only guaranteed way to ensure that the repair worked correctly was to cut the deck at the middle of the front and rear beam mounting points (this was so that after the repair the cuts were supported and hidden by the beams), then lift the decks between the cuts off, grind off the inner laminate and the foam, vacuum bag new “semi rigid PVC foam” and vacuum bag a new inner laminate. We would then join the deck back to the hulls. This repair has stood up until today on boats that we repaired as far back as the early eighties with no sign of any recurrence of the problem.