building hardtop
I'm a composite guy having designed and built boats forever, some submarines, airplanes, rockets, worked on AC campaigns and even a bit on satellites. Building a light weight hardtop is pretty easy, I am currently building one for our Grand Banks 36, it's roughly 9' x 9' with a weight of only 41 pounds, (NOTE: this did not include the legs, that adds another 10 pounds or so). The construction is carbon fiber and Nomex honeycomb. It works out to under .5#/sq. ft. and is easily strong enough to stand on. I installed hard points to attach 4- SunPower 170 Watt solar panels. I am running the power cables through the legs into the flybridge. Carbon fiber and Nomex honeycomb aren't the only options available, fiberglass and balsa core could also be viable and easily under .75 pounds/sq. foot.
Molds can be easy or hard. If you have only a 2D "developable" surface, it's pretty easy. By "developable", I mean it's a surface you can get by bending a sheet of paper or plywood. In other words, it doesn't have compound curves. I often use melamine finished Masonite or better yet, "FRP" sheets from the lumber store. These are flexible sheets for use in shower enclosures and are pretty inexpensive. I wanted a bit more of a sculpted look so I did curve it in 3D. I added foam blocks to the front of the mold then sanded it to shape, fiberglassed it then covered everything in Teflon mold release film. The film is only a few thousandths of an inch thick so the inevitable creases and folds are easily filled with putty or primer. Since I was using honeycomb, vacuum bagging is a must and it's best to use that on foam or balsa but you could get by without vacuum.
Attached are some photos of the mold for my hardtop and the hardtop with the teak consoles. I added teak consoles forward and on the sides for reading lights and to hide wiring for the lights, radar and solar panels. These are nearly the weight of the hardtop alone but add a lot of panache in my opinion and make for a lot better lighting. Also note that at the front is the mount for the radar.
I am waiting for the custom color paint to come from Alexseal then I can spray and mount the hardtop. BTW, Alexseal is my favorite brand of paint. It's as glossy and easy to apply as Awlgrip but can be touched up and repaired. Awlgrip is a wonderful product but you can't buff it to match the original.
I will be making some more hardtops from this mold this winter depending on time available and interest. You can contact me at
dan@pegasusaeromarine.com if you are interested or have questions about making a hardtop.