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Old 20-08-2016, 15:50   #31
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Re: Best Hardtop Bimini Ideas

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Originally Posted by DavidLGCrawford View Post
To finish the edge of mine I used a router with a 3/4" rounding bit along the top and along the bottom so it has a 1.5" radius rounded edge. This also helped with the glassing as it wouldn't have taken to a sharp corner as well as it did to the rounded one.

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Not to be picky, but I think you still have 3/4" radius.

Sounds like it looks good though
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Old 21-08-2016, 06:43   #32
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Re: Best Hardtop Bimini Ideas

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I chose .063 aluminum. Finished the edge with awning track for whatever canvas I want to add.

400 watts, back when it was $2.50/watt (that was an excellent price then) I can rework for more efficient panels when the time comes...


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Old 21-08-2016, 06:51   #33
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Re: Best Hardtop Bimini Ideas

Once, about ten years ago, under a bit of material duress, I made a hard top out of FRP panels normally used in commercial kitchens and bathrooms Link to Lowes for an example

I have seen it recently, and despite a few hurricane strikes in Key West, it is still standing and the panels look good as new.
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Old 21-08-2016, 20:23   #34
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Re: Best Hardtop Bimini Ideas

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Originally Posted by ggray View Post
Not to be picky, but I think you still have 3/4" radius.

Sounds like it looks good though
Ohh.. it was a long day. Yes, obviously I still have a 3/4" radius. I meant to say I have a 1.5" DIAMETER rounded edge.
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Old 21-08-2016, 23:11   #35
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Re: Best Hardtop Bimini Ideas

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Originally Posted by elaak View Post
Some solid ideas! I currently have a bunch of decrepit 3/8 ply sheets painted with what now looks like aged bird s***. Looking forward to some improvement.

Few questions for the masses:

- I'd love to be able to have finished wood (varnish, cetol) on the underside of the bimini (not exposed to direct sunlight). Feasible? Including being able to keep it looking good in the tropics.
~ You can put a perfect glossy finish onto a nice piece of ply, like Okoume, or a DIY strip planked panel, via Platen Molding. Which is when you use a perfectly flat & smooth surface as your mold.In this case a piece of Formica (Melamine) backed by particle board works well. Though you may have to mount two pieces side by side on a frame work in order to get a large enough working surface.Using a piece of clear plastic packing tape to cover the joint, for a seamless “mold”.

Then you;
~ Scarf together the plywood pieces which will be part of the hard Bimini, if needed. To make full sized panels.
~ Wax up your mold table well with, preferably with mold release, but some other release agents will work too.
~ Lay down your glass cloth & resin onto the flat, prepped mold surface. Preferably using a light weight piece of standard woven cloth.Say 12oz or less in weight.
~ Spread on some epoxy, on top of the glass cloth in preparation for adding the plywood layer.
~ Spread some epoxy onto your plywood, & lay it atop the already wetted out glass cloth.
~ Spread some neat resin onto the top of the plywood. Then add a 2nd coat o epoxy to the wood, as some of the first coat will have been absorbed by the wood.
~ Spread some thickened resin on top of this, to act as the bedding compound/bog for the foam.
~ Spread a layer of neat resin onto the side of the foam which will be being bonded to the plywood.
~ Position the foam atop the plywood.
~ Spread some resin onto the top of the foam.
~ Add your top layer(s) of wetted out cloth or plywood to the top side of the foam.
~ Vacuum bag the stack till cured. Or if not that, then use weights atop it.
This latter method only really being viable if the top of the panel will be plywood. Although you can do it if you’re using glass for the final top layers of the panel. But you’ll need to cover the wet glass with plastic sheeting, & then add a piece of plywood to aid in evenly spreading out the compressive loading of the weights.

~ Then, once the panel has cured, you can trim it to it’s final size, & bull nose the edges. Then using fiberglass tape & epoxy, to seal the edges & make them part of the monocoque panel/lid.
~ After this, once things have cured SOLIDLY. Clean the mold release wax off of the bottom side of the Bimini panel (the bottom piece of platen molded plywood), & give it several coats of varnish overtop of the epoxy, to protect it from el Sol (the Sun).
Ditto on similarly coating the top side of the panel, that, or paint it.


One other way which you can do things, is to first put a perfect finish on the bottom sheet of thin plywood as described above, via Platen Molding. Or via more traditional methods. But either way, the plywood will still be pretty flexible, even with a coating of light weight glass on one side. And it will have some flexibility if there’s glass on both sides, too.


From there, take this pre-sealed/finished panel & mount it onto some formers in order to give it a bit of camber. And then simply add the rest of the layers; foam, glass, or plywood , onto it. So that with everything being bonded together while still being attached to the formers, once the epoxy between the layers cures, the cambered shape will be locked in.


You can, of course, use any number of materials in lieu of the plywood, for the bottom layer of the hard Bimini, where it’ll be very visible. Such as some cedar strips (optionally tongue & groove), edge glued together in strip plank fashion. Backed with a layer of heavy glass cloth in between the wood & the foam layer.
Things such as cedar strips edge glued together like this, look great when epoxy coated & varnished, & make for a very strong panel when backed with a light – mid weight layer of glass.

Also, if you’re doing some variant of a composite stacked layup as above, you can add extra layers of reinforcements (cloth & epoxy) anywhere in the stack, in order to add more strength to things.

- For laminating foam to ply - just normal polyurethane resin?
You’re best off using epoxy resin for all of this, as most other resins tend to have much poorer bond strength when using the materials in question. And realistically, unless you're doing a huge project, the cost differences in resin types isn't that big a thing.

But try bonding some different materials with various resins, & then do some destruction testing on your results which simulate real world, long term, worst case conditions. Thermal swings, & water that expands when frozen in between layers, are fun ones for any materials & adhesives to try & cope with

Also, with epoxy, you can use it to blend your own thickened bog/paste for bonding the foam to the plywood with.

- I'm keen to hear more about how folks are finishing the edges of the their masterpieces. I feel this is is what makes the difference between something that looks DIY and looks pro.
The best way to make something look professionally done is to build & use a jig, so that everything is repeatable & precise. Though in addition to that, little beats taking your time on things. As well as experience & practice of course. Including practicing on things other than the big project at hand. Test projects rock! And... save you money in the long run.

With foam, one way to do the edges is to simply hand sand a radius into the edge of the panel, prior to fiberglassing it’s edges. Or, you can use a router to bull nose the edges before glassing them.
Another way would be to buy or make some wooden quarter rounds, & trim the foam back from the panel’s edges enough so that you have room to glue them in place, in order to give the perimeter of this lid a nice finished edge. Though this route would be a lot more work than just bull nosing the foam, & then glassing over it.

- AZEK - Does anyone have any photos of what it looks like after being baked in the sun for a few years?
With a proper painted finish, the Sun shouldn’t give you any trouble at all with this type of construction. Ditto on parking the boat somewhere frosty for a few seasons. As these methods & materials are the same ones which are used in a lot of boat hulls & decks.

Cheers folks
Hope this helps.


PS: If there's some part of the structure that'll see stupidly high loads, you can add solid internal blocking in place of cores, when first building things. Though such can be added later too. Or extra external structure can be added in the form of ribs & frames, ring frames, or bonded on mounting pads, etc.
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Old 24-08-2016, 08:44   #36
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Re: Best Hardtop Bimini Ideas

Who built it? Do you have any other info about it. I want one just like it.
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Old 24-08-2016, 09:08   #37
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Re: Best Hardtop Bimini Ideas

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Who built it? Do you have any other info about it. I want one just like it.
Who are you talking to? There have been 3 or 4 people talking about their hardtops...
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Old 24-08-2016, 09:29   #38
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Re: Best Hardtop Bimini Ideas

[QUOTE=DavidLGCrawford;2196470]Who are you talking to? There have been 3 or 4 people talking about their hardtops...[/QUOTE

I hit reply instead of quote. I'm new to the forums. Thanks for letting me know.
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Old 24-08-2016, 09:31   #39
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Re: Best Hardtop Bimini Ideas

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Originally Posted by iliohale View Post
Check out this blog: Out Chasing Stars Out Chasing Stars - Sailing Adventures on Our Helia 44

David and Amy on their FP 44 built a custom Bimini that turned out really good.
Who built it? Do you have any other info about it. Thanks in advance. Jim
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Old 24-08-2016, 17:30   #40
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Re: Best Hardtop Bimini Ideas

Here is my latest thoughts on my hard top bimini. Granted is on the cheap side becuase my catamaran is cheap. Materials are from Loews. One 4x10 white fiberglass pannel, one blue foam pannel, one luan 1/4 inch plywood, west epoxy, and create a sandwich. On top the fiberglass pannel, in the middle the blue foam, underneath the plywood. Shape like a flat piramid, round corners, routing the edges, and place on top of SS 1" thick posts. 4 ft long by 8' wide in the back, tapering to 4 ft wide in the fron, and call it a day. The material cost is about $100 for the top, and $6/ ft for the stainless tubing here in Miami, unless I can find old stock somewhere.

Any other ideas on the cheap?
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Old 24-08-2016, 17:41   #41
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Re: Best Hardtop Bimini Ideas

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Who built it? Do you have any other info about it. Thanks in advance. Jim
Here is all the details on who made Out Chasing Stars hard top.

Out Chasing Stars Palmetto Projects Part 3: Enclosure and Hardtop - Out Chasing Stars
.
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Old 07-09-2016, 21:30   #42
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Re: Best Hardtop Bimini Ideas

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I just did up an aluminum frame the appropriate size and filled it with solar panels. They ARE the bimini top. No wood, no fibreglas, no nothing. It also has lips (I used 2" aluminum T-bar around the perimeter) that catch the water and direct it to two drains at the back which, with a little plumbing and a filter or two will capture rainwater and direct it to the water tanks.

There are six solar panels up there totaling 420 watts. It works like a hot damn!
Can you send me photos and information?

Charles
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