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Old 16-08-2016, 19:21   #1
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Best Hardtop Bimini Ideas

Hi Folks,

What are some of the ways that you all have seen hardtops on cats done? Plywood? Fiberglass? Edge trim?

I'm about to replace mine and looking for ideas.

Cheers!
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Old 16-08-2016, 19:49   #2
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Re: Best Hardtop Bimini Ideas

I am in the same search but with a much smaller catamaran

Nevertherlees, here is a link I found that might be usefull
How to add an arch and hardtop to your sailing catamaran
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Old 16-08-2016, 20:30   #3
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Re: Best Hardtop Bimini Ideas

3-6mm ply sheathed in light glass, topped with foam core, round over the foam's edges (bull nose), & add 1-2mm of glass atop foam (or 2-4mm ply). It'll be stiff, light, and easy to shape & build.

So between the sandwich construction & building in a bit of camber, it'll be nice & solid. And to attach anything to it, either glue on some mounting pads, or epoxy bond the fasteners into the sandwich.

Edit: With the above, it's pretty easy to build in an acrylic panel or deck hatch, so that you can still see sail trim. Ditto on adding lighting on the underside. And attachments for side curtains & the like.
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Old 16-08-2016, 21:10   #4
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Re: Best Hardtop Bimini Ideas

PS: Were it me, I'd Platen Mold the first layer of Ply w. Glass Sheathing, so as to get a mirror finish on it. So that it'd need zero sanding, with little added fabrication labor.
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Old 17-08-2016, 05:34   #5
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Re: Best Hardtop Bimini Ideas

We just completed our new hardtop for our Wildcat 350. It's 11' wide and 10' long, so 110 sq ft. Two layers of 3/8" marine ply, covered in two layers of fiberglass. It now has 1060 watts of solar on it, and I can walk on it when accessing my boom. It also has a built in lip and drain holes so we can catch rain water and get 100 litres per cm of rain.
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Old 17-08-2016, 09:35   #6
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Re: Best Hardtop Bimini Ideas

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Originally Posted by DavidLGCrawford View Post
We just completed our new hardtop for our Wildcat 350. It's 11' wide and 10' long, so 110 sq ft. Two layers of 3/8" marine ply, covered in two layers of fiberglass. It now has 1060 watts of solar on it, and I can walk on it when accessing my boom. It also has a built in lip and drain holes so we can catch rain water and get 100 litres per cm of rain.
You're such a tease...

How about some pictures? Sounds like quite the project.
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Old 17-08-2016, 09:48   #7
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Re: Best Hardtop Bimini Ideas

https://www.google.ca/search?q=hard+...w=1366&bih=667
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Old 17-08-2016, 09:48   #8
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Re: Best Hardtop Bimini Ideas

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You such a tease...
Agreed!

David, how'd you manage the greater than 8ft span with plywood?

Uncivilized, also some solid ideas. I liked the idea of bull nosing the foam core on the edges to clean it up some.
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Old 17-08-2016, 10:24   #9
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Re: Best Hardtop Bimini Ideas

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Agreed!

David, how'd you manage the greater than 8ft span with plywood?
I'm guessing a bit as I haven't seen his boat:

It's two layers thick, so offset the joints and scarf the joints will result in a pretty strong structure and you can build it pretty much any size you like.

2 layers of fiberglass is a little non-descript but assuming they are structural layers, the wood acts like the webbing in a I-beam with the fiberglass carrying the bulk of the loading. Which is even stronger than just the plywood.

The tradeoffs I see:
- Wood core is easy to work with and make strong enough to walk on but susceptible to rot if you start drilling thru the fiberglass and don't do a good job sealing it.
- If you aren't going to walk on it, foam core largely eliminates the rot concern. If you upgrade to a more dense foam, you can make it strong enough to walk on but you are much more dependent on proper fiberglass work as the foam doesn't have the same structural value.
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Old 17-08-2016, 10:42   #10
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Re: Best Hardtop Bimini Ideas

Just a suggestion... King Starboard or similar. Comes in different thicknesses and sheets up to 54" X 96". Will flex slightly and doesn't fade. A few different versions of white available. Use word wording tools to cut and finish it.


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Old 17-08-2016, 11:58   #11
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Re: Best Hardtop Bimini Ideas

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.
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Old 17-08-2016, 12:28   #12
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Re: Best Hardtop Bimini Ideas

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NICE hard dodgers!

On the foam laminate, if you bump the glass up to 1.5-2mm you can walk on them just fine. Some hulls & decks are built like that. And a wood/foam/wood laminate is super stiff & solid.
Ever walk on Blue Board with work boots? It's 1/3 the density of structural hull foam.
The only catch is to build things strong enough for whatever span distance you choose. And that's dependent on your laminate stack.

The flipside is that 3/4" ply with 1mm of glass per side weighs 3lb/sqft. Where a structure consisting of 6mm ply, 3/4" foam, 4mm ply, & 8oz glass sheathing will be about 1.4lb/sqft.

I mention this as lots of catamarans go for these kinds of cockpit covers. (Some oe which) are weight sensitive. So the difference between the two adds up to a lot of beer. And weight up high on any boat is bad.
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Old 17-08-2016, 12:43   #13
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Re: Best Hardtop Bimini Ideas

Quote:
Originally Posted by elaak View Post
Hi Folks,

What are some of the ways that you all have seen hardtops on cats done? Plywood? Fiberglass? Edge trim?

I'm about to replace mine and looking for ideas.

Cheers!
Hi Elaak,

I've been collecting hard top ideas to replacing existing canvas dodger and bimini on my monohull.

Some of these may scale to provide some food for thought for your project as well.

Cheers! Bill
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Old 17-08-2016, 14:48   #14
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Re: Best Hardtop Bimini Ideas

I really like some of the ideas presented. I am not as ambitious as most. I have just finished a 10' wide top. I found two fiberglas tonneau covers from wrecked trucks. I cut one in half and took 38" out of the centre of the second top. These tops have a resin impregnated core which is easy to scrape out. I then took 5/8 X 8" X 6' pressure treated plywood coated with PL adhesive and keyed this into the void . The rounded corners not used from the second top, was used as a combing around the flybridge access. I reinforced the back edge with multiple layers of plywood and fibetglased over. used hull liner on underside. looks professional and cost me $100.
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Old 17-08-2016, 16:50   #15
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Re: Best Hardtop Bimini Ideas

Here's a few post I did on making a hard top out of sheets of Azek.

Very easy to work with using wood working tools.

No finish work or painting is required as the sheets are white throughout.

Warranty is for 25 years.

Sheets come in different thickness and 4x8 or 4x11 foot sheets.

Bimini

Bimini
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