Cabin Wall Strength Question if Increase Window Opening Size

Feb 3, 2016
Spacesailer 18 Longmont, CO
I'm performing a cabin window replacement on my 1984 MacGregor 25--out with the pink and in with new. Question: Can I increase the area of the window opening without compromising the cabin top strength directly over the windows? I plan on increasing the hallmark pink windows with a light gray polycarbonate, which is thicker than the stock window acrylic and will be bedded and fastened more securely than the stock windows. I am assuming the 1/4 inch polycarbonate will be acceptably strong with adequate fasteners. Opinions wanted. Thanks
Feb 21, 2013
Hunter 46 Point Richmond, CA
Last edited:
Apr 11, 2020
Hunter 170 Grapevine
Two things that would help, IMO, would be to choose a material as strong as the material you are removing, and attach it firmly enough that the integrity of the structure as a whole is maintained.

In home building, framing is done such that the structure is sound even if there is no window or door in the opening. This is because windows and doors have to open, thus cannot bear a structural load. If this is a non-operating window, then the clear material can substitute for the original hull material if properly attached. If it is a window that can be opened, the frame must bear the load. This is why operating boat window frames are so beefy.

Fortunately, overhead loads on a boat are not great, except when the mast rest on the roof of the cabin.