Hardtop

Hi hopefully some one can help guide me here. Planning out a hardtop bimini. quite large 147 inches by 180 inches at its wides points. My plan was female mold , gelcoat, layer csm, 4 layers 1708, 1/2 inch core, (foam or balsa) 4 layers 1708. Polyster resin , with a tic tack toe layout of stringers. It totals about 160 sq yards of fabric and 45 gallons resin. My Problem is weight. What would be the minimum layup that would give strength to walk on but lighten the structure

thanks for any advice

 

It would be interesting to have a drawing with the layout you have. In principle, if weight is your concern, you could fit a thicker core and reduce the number of layers. 8 layers of 1708 plus 1 csm layer seems too much, but without knowing the distribution of panels and reinforcements and without knowing the real load on the structure, it is not possible to say. You speak of having "strength to walk on" but how many people per m2 should the structure support, what other loads can there be on it?

 

Thank you for the response. Without going into the slight curve to match the cockpit with , it is a basic rectangle. 147 inches x 180 inches The forward end will lay and bolt on the arch which supports the dodger and main sheet. The aft end will be supported by x2 stainless tube at helms about 1/3 from the back. It will have a very slight camber and stringers will run x2 forward to aft /// x2 port to starboard evenly spaced So there will be 9 sqaures of 60 inches x 49 inches between stringers with 1/2 inch core (Im thinking 2x2's for stringers) It only needs to support 1-2 people max to get to the end of boom, other then that just solar and maybe paddle boards. Whats the lightest layup schedule i could go with?

thanks again

 

The panels with their reinforcements constitute a whole and the laminate of a panel cannot be defined without knowing what its reinforcements are like and how they are supported (the reinforcements).

 

Wayyyy too much glass.

900g CSM
1/2” 6 lb PET foam
900g CSM

if you want it stiffer, increase to 3/4” core.

 

There is a forward to aft span of 147 inches, a port to starboard span of 180 inches. The forward section is supported completely across a 108 inch span port to starboard on the arch. The rear supports are 2 vertical posts 36 inches from the port/ starboard edge and 48 inches from the rear edge. So you have a 95 inch span from rear supports to front support and 36 inch overhang port and starboard from the rear vertical supports.

 

As I have understood, you have the arrangement of panels and reinforcements as in atteched picture. I'm probably misunderstanding you because that arrangement doesn't seem adequate to support weights on it. The reinforcements, specifically, are poorly supported, so it is expected that reinforcements with very high inertial moduli will be necessary in certain sections. The problem, in my opinion, is the reinforcements, not the panels. For these it would be enough with something similar to: CSM 900 + Coremat XM 2 (half an inch) + CSM 800

 

Dear Steven , at first could be good to know if you think to use hand layup building process or infusion . Generally for my fishing boats design I provide 2 shells ( Upper side and Down side ) solid skin in fibercarbon or fiberglass and stiffeners . The stiffeners can be used like cable duct for wiring system ( radar,gps , lights ,spotlights etc...) at least 6 small pillars connect the stiffeners and the 2 shells (naturally perimetrally have to be are well fixed to improve the stress flow ) . Reinforce where the 2 vertial posts and other structrures will be connected with the hard top . Use speakers holes to screw the locknut from the interior part.