Making hard Coach Roof/ Bimini - questions

[Cpt Mark]

following

[magentawave]

I think a couple of these have already been mentioned, but just in case...

https://youtu.be/iEo7Y-fCG0I

https://youtu.be/WJSAdZTollc

https://youtu.be/XoNUowUE1uE

https://youtu.be/rK3lWlVF3ys

https://youtu.be/kB1A1tz0WTg

I'll be building a hard bimini top for my boat soon. It's a trimaran so it won't be as huge as yours, but I will definitely put some curve in the structure for stiffness and I'll include a lip along the outside perimeter of the top to serve several functions:

1) It will also stiffen the structure.
2) It will be something to grab on to.
3) It will catch water.

[Scorpius]

Originally Posted by mvweebles

Builder of my hard top (trawler 11' L x 8'W) is using 1/2" cpvc pipe as electrical conduit to lights.

I have to say, I'm surprised there have been scant comments on (1) structural strength of spanning a 16-foot width; and (2) single layer of glass OP proposes over/under the foam. If this were a floor in a house, would see something like 2x10s on 16" centers.

The Building Code around here says 2 x 10's on 16" centres can span only 12 feet. 16' is an awfully big span. To walk up there I'd think you almost need trusses!

[Compmar]

This is a freestanding hardtop I built for an Outer Reef cruiser.
1" H60 Divinycell core. 1 layer 1708 biax top and bottom. 4 solar panels mounted to fiberglass hat section stiffeners. 2 lower side stiffeners/wire chases with 4 Hella red/blue dimmable LED lights. With 4 180 lb people on top the deflection was less than 1/2". the edges were dropped down 3" and tracks for Isinglass installed. The edges were reinforced with an additional layer of 1708 biax. This was installed in Florida and the boat went to northern California via the Panama Canal.


16' x 14' Hardtop

Transportation to boat from Florida west coast to Florida east coast (Boat in background.)

[magentawave]

Beautiful job, Compmar. Do you have photos of it installed on the boat? Did you use stainless steel or aluminum tubes to support it?

[Compmar]

I have more picture somewhere and will drag them out. The foreword posts are aluminum and the rear is attached to the radar arch.

[clockwork orange]

I have built a few hardtops for customers boats over the years by a number of different methods including building a temporary female mold using plywood and formica for a gelcoated finish that was required to look like it came from the factory. I generally use a combination of uni and double bias with VE rather than epoxy. No reason for the massive laminates that some propose. H60 makes sense to keep the weight down, its not a hull. I am planning to build one for my own boat and at the moment i'm thinking of infusing it flat on the table with H60 perforated core/VE/full laminate on the top/light mat on the inside then score the inside and bend into a minimal form and hand laminate the inside. I want to be able to walk on it and mount panels but it does not need to be like a sidewalk, no reason to hold a party up there.


Steve.

[Compmar]

Infusing on a temporary formica mold works very well. I do not bother having a thin skin on the up side. Just infuse the down skin and core and then cold form to the camber templates and laminate. Works for me. Will cold form easily up to a 6" camber. The second skin creates the stiffness. I have also created a complete mold at times to the correct camber with plywood templates overlayed with 1/2" mdf and formica glued to mdf. Spray PVA film for release. Then a full infusion or even a hand layup with the core vacuum bagged.

[Michael Pope]

Great!! lots of interesting Dodgers and fine looking as well and many or perhaps most of them eminently satisfactory! --- I am scared of the sixteen foot span and wanting to walk on the top surface . There are a million ways to do this "My old man's Caution" having done many of these as well is consider just briefly what happens if you do overload it and it collapsed across the companionway , The Cabin top winches (if they exist,) a number of sail controls and also perhaps a steering station--AND if it was almost strong enough for the job and therefore is going to take a lot of UNDOING to restore control of the boat and whoever happened to be underneath it when it collapsed. It is hard enough when it is done with thin wall SS tubing and Sunbrella. When it is welded Alum or strong enough FRP you may be wishing for a Chain saw or a big sharp Axe or for someone to "Beam you Up out of a nasty situation. I think some of the welded Alloy ones are "Peachy" I really liked them but before going to "Hobart" please get three Large Rugger Forwards to jump up and down on it first! ------ I built an Upside Down Spoon Cabin top and was surprised how flexible it it was and it was built with Kevlar and the span was only 10.5 ft
with 1.5 lnch thick Corecell foam core . It was lovely in the end with handles noulded in the aft edge . But it used a a lot of unidirectional reinforcement before I felt safe with it Offshore.. Just a caution! Mike P

[Compmar]

Originally Posted by magentawave

Beautiful job, Compmar. Do you have photos of it installed on the boat? Did you use stainless steel or aluminum tubes to support it?

Best I could find (not great quality)

[carlosproa]

Originally Posted by magentawave

I think a couple of these have already been mentioned, but just in case...

https://youtu.be/iEo7Y-fCG0I

https://youtu.be/WJSAdZTollc

https://youtu.be/XoNUowUE1uE

https://youtu.be/rK3lWlVF3ys

https://youtu.be/kB1A1tz0WTg

I'll be building a hard bimini top for my boat soon. It's a trimaran so it won't be as huge as yours, but I will definitely put some curve in the structure for stiffness and I'll include a lip along the outside perimeter of the top to serve several functions:

1) It will also stiffen the structure.
2) It will be something to grab on to.
3) It will catch water.

Great
Take a look at the Mainecat38 detail on the hard top and see how they integrate hands holds built in.

[Jon Hacking]

Originally Posted by carlosproa

...make a hard coach roof like a Mainecat 38 or 41. My thought is to have Aluminum posts and build the hard to out of either foam Divinycell or Nida-Core Honeycomb. The latter has the option of having pre-laminated with 1 layer of 18oz woven roving in either side with polyester.

The coach roof or hard top would be roughly 8 ft long by 16 wide.
My question is which thickness to get so if I have to walk on top, it would hold. They offer 1/2, 3/4, 1 inch...

We built a 10ft x 10ft bimini in foam sandwich with epoxy & biaxial. It's supported at the back by the Targa bar, but at the front only by a post at each corner (which double as rain-catch down-spouts). At 1" foam thickness (actually 27mm) it supports 3 people pretty easily, although it flexes a bit. The overview (which has apparently been used to build several other biminis) is here, with descriptions of what we did & links into our daily blog to where the actual work happened (with more detail, but cluttered with other work that was happening at the same time)

[Nepidae]

I got on this forum thinking it was more than a sailboat 'cruiser' forum. We own a trawler.

I keep checking on it as I figure just because it's a sailboat doesn't mean I can't learn something.

I saw this thread and though, we took our canvas Bimini off and replaced it with a hard top, aluminum frame and plastic structure within the frame. We used the SS tubing from the canvas as the support for the hard top.

The top will hold solar and of course could be setup, installing a lip around the hard top, to catch rainwater and channel it to a holding tank.

Maybe you sailing guys like to over engineer everything but for those who either might have a canvas Bimini OR could build with 1" SS tubing then a Hard to Top might be the answer.

Hard to Top can be found here (Home | Hard To Top). You can't walk on it, so if that is important, build to your hearts content. For this who want a structure that doesn't flap, protects you and isn't a structure you feel the walls moving in, then a Hard to Top might be just what you want. You can add canvas sides if you want, we did and they are removable.

I've added a few pictures of our Hard to T.op

[StoneCrab]

I never understand why so many feel that they can just "wing it" and don't see the value of actually hiring a degree'd engineer who can optimize the design.

The cost of the amount of material saved from the "belts and suspenders" approach, or the cost of doing it over after it fails, will more than pay for the cost of the engineering.

Be smart. Hire a professional to design it.

[Morph]

It's not that hard, however you do need to know basic fibreglassing techniques. I build a foam and glass cockpit cover for my 39' cat. It was roughly 6' deep by 15' long. I used 50mm foam laminated with 200-225gm biax glass using kintex laminating epoxy resin. It's a big laminating job but quite possible. I build temporary frames so it would have the right bend--after it came out it bent to what ever shape I wanted. I used stainless poles to hold it in place--two long ones coming off the aft beam at the back and three short ones off the bridgedeck cabin at the front. It held brilliantly for 10 years (I sold the boat then), the composite structure is amazing. It handled people walking on it however it did flex a bit--I didn't bother with ribs as it was clearly strong enough and I put the solar panels on top--
The edging was pvc pipe glassed on which is great and allowed us to catch water--the owner of the sister ship directly copied what I did and build one for his boat--

Cheers
Phil