The glob of original sealant shown above shows that the junction between the two shells was imperfect at the time of original manufacture since the glob shows the sealant was used to attempt to close the gap between the assemblies that showed itself when the hole for the original ventilator was drilled. When I first examined my boat I was concerned by the fact that there were areas in the cabin where you could push up the cabin overhead, indicating a gap. However, as evidenced by the construction sandwich shown by the first figure and the complete integrity of the balsa-fiberglass sandwich, the bond between coachroof and overhead was not perfect in the original construction and is not essential to the structural strength of the coachroof. Proof of the pudding. Jump on it, if it doesnt crackle and is not soft, theres plenty of strength

See 79 H33 cabin top section

In replacing the original static ventilators with solar ventilators, I found some things in the coachroof construction that may be of use to other H33 owners.1. The core is end grain balsa and even though the inside of the original ventilator hole was not sealed, the balsa and its attachment to the lower and upper fiberglass was completely sound. The structure was evidently built upside down with the buildup progressing from gelcoat, fiberglass layup, installation of end grain balsa and finally the lower fiberglass was bonded to the balsa and laid up. 2. With the assembly turned over, a separate laid up shell comprising the cabin interior overhead was then evidently attached and it is this attachment line that is shown separated in the photo as identified by note ragged fiberglass The overhead portion of the section is shown by the next photo.