Hard bimini layup

[AndyR]

I have made the corecell core for a hard bimini to mount flexible solar panels that will be stuck down using the manufacturers double sided tape. The bimini is 32" by 102". It is 1/2" corecell, with 1.5" flange of corecell all around. It is curved athwartship by about 9" over its 102" width. It is fully supported by 1-1/2" pipes of the stainless solar arch over its full width but the arch is only 18" deep (ie. between pipes in the fore/aft direction") so there is an unsupported cantilever of 14" forward of the steel. I could move the panel further aft and reduce the overhang to 10". I can add fore/aft stiffeners if needed. have a big roll of 12 oz biax and will laminate using vacuum bag. No loads except wind. I want to try and get away with a single layer of 12 oz top and bottom or at most, 2 layers top and one on bottom. If anyone can advise whether this seems too light, I would be grateful. Thanks

 

[fallguy]

I think you’ll be good, although the 12 oz is not my favorite for this application. I would prefer a Hexcel 10-16 ounce. The reason is there is no stitching to sand away and leaves a nicer finish and can be weave filled with a couple extra layers of clear epoxy or resin, again for nicer finished look, although noone cares much about the hardtop finish.

For the cantilevered portion, you can just double that area. You may want to use bleeder film in the stack to reduce the pull away of resin. The coosa needs some resin. I assume you will add the thicker flange at the end; it will create a nightmare in the bag. Is the thicker flange just to direct water/a gutter? Always need to consider where water goes..maybe you are way ahead of me, but I added the gutter out of the bag and glassed it separately with two pieces, one from the bottom and over and then another up and over the edge.

I did not use coosa thru n thru and only made local reinforcements of it, but came to regret not going all the way around the edge.

 

[TANSL]

This structure shouldn't withstand heavy loads, only the force of the wind (the surface acts like an airplane wing), which will try to tear it from its anchors. Therefore, it's the area of these anchors and the metal profiles that hold it to the hull that need to be studied and, perhaps, reinforced. The surface of the bimini itself only needs to be beautiful and well polished.

 

[AndyR]

fallguy: Thank you. The flange is both to direct water and to stiffen the edge. Amazing how, with an extra layer of 12 oz, it really stiffens the panel. I am using corecell, not coosa.
tansl: Thank you, too. Attachment of steel arch to the hull is no issue. It is a really heavy, factory, arch through bolted to the hull. It previously held 4 large solar panels during three atlantic crossings so I am sure it will be ok for this smaller panel. I think I will incorporate fore/aft stringers of pultruded fiberglass angle to both support/hold down the overhang and to give a strong point for bolting onto the steel.

 

[fallguy]

For corecell, you’ll need local reinforcement of either M200 corecell or something like exterior plywood to attach anything extra to..say for example anchor light base. Otherwise you’ll end up bonding a base to the top later.

I used 3 x 6mm corecell for mine to get the curvature the way I wanted and then cutout the areas for 18mm coosa, faired to flat and glassed with 10 oz woven. Sorry I misread that earlier.

For the attachment of the top to a frame, I used 1/4” screws and 2” flat washers on the corecell, but a hurricane wind might rip it off, so been considering some 5200 around the edges.

 

[gonzo]

Could you use a pipe with spacers along the edge? It would reinforce the cantilever and work as a handrail or to tie things.