Hard top from scratch

erikgreen

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Jan 8, 2007
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Guys, I'd love to hear your thoughts on this plan.

As my winter project, I'm going to add a hard top to my boat, a 21 foot Sea Ray cuddy cabin. I'm choosing a hard top over a bimini because of the environment I'll be using the boat in, the great lakes. I need protection from rain more than sun, and the ability to keep some heat in would be good too. The hull is deep V, so I'm looking to avoid a lot of weight up high, since that'll raise my CG up and make me more tippy.

I'm starting the hard top from scratch, and I'm going to design it to fit where the current cuddy windshield is. I'll be buying custom cut safety glass for the new windshield, and I'm planning on fiberglass covered foam for the rest of the structure, which will be enclosed at the front with the windshield, sides with windows that open, and have an open back with a slight overhang.

The materials are my major question at this point. Structural foam from a marine store is too expensive to use on this since I'm not sure I can make this work. I want to use 1 inch thick panels for this, and I'm planning on making through holes every 6 inches or so, to tie the two sides together with solid resin. I'll be using marine epoxy.

I was thinking of using Quik-R board, which is styrofoam board with a layer of fiberglass pre-adhered to one or both sides. I think this would make sure that the glass layers I add would stay laminated to the foam. Alternatively I could use plain pink styro sheets, which has the advantage that I could shape the panels with a hot wire cutter.

I'm basically going to form the shape of the top with the sheets, glass them together with 3-4 layers of 8 oz cloth (what I have) and then glue/screw (polyurethane/sikaflex) the window frames in place. I'll be glassing some hardwood (mahogany or something) mounting pads to the top so I can screw on antennas, lights, etc. I'll attach the whole thing to the boat with bolts - I'll embed aluminum brackets in the top glass for attach points, and use backing plates on the boat.

I have the necessary welding equipment (but not the skill, yet) to add an aluminum frame to the top if needed, but I'm hoping I can skip it to keep weight down. I'm not planning on walking on the top, although I could see resting my weight on it long enough to adjust something.

What do you guys think?

Erik
 

erikgreen

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Re: Hard top from scratch

I've seen that project before too... just haven't heard much recently, and I was hoping someone here might have fabricated something similar and would be willing to chime in.

Erik
 

Chris1956

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Mar 25, 2004
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Re: Hard top from scratch

Eric, I think you are on the right track. You might embed some wood strips in the hardtop to give added strength. Check out surfboard construction, since you will be doing something very similar, and if you can achieve the strength of a surfboard, I think you have it licked.

How about 2" thick styrofoam in a frame of 1" x 2" fir strips? You could fasten the aluminum frame to the wood quite easily.
 

Bondo

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Re: Hard top from scratch

I have the necessary welding equipment (but not the skill, yet)

Ayuh,.......... Now might be the Perfect time to Learn.........

I threw this together a few years ago with scrap Aluminum conduit,+ some railroad crossing parts,+ hospital bed pieces.......

It keeps the Rain out in the Summer,+ I heat the inside when fishing Late season with a little Mr.Heater.........

And,....... I don't think the Whole Kit,+ Kabootle weighs 100lbs..........

f17692.jpg
 

erikgreen

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Re: Hard top from scratch

Eric, I think you are on the right track. You might embed some wood strips in the hardtop to give added strength. Check out surfboard construction, since you will be doing something very similar, and if you can achieve the strength of a surfboard, I think you have it licked.

How about 2" thick styrofoam in a frame of 1" x 2" fir strips? You could fasten the aluminum frame to the wood quite easily.

Well, I have the inherent dislike of wood that anyone who's replaced stringers and transom has :) But it's a good idea. So the glass covered foam wouldn't be strong or stiff enough on its own, you don't think?

I think I'd lean toward welding for a frame.. I suppose I could try to find some carbon fiber spars instead... maybe attach/embed some aluminum in the panels to stiffen them, then use the ends of the aluminum spars as bolt points to join the panels.. maybe I can post a drawing.

I was kind of hoping to just mock it up in foam, cover in glass, and add the windows, and that would be enough... maybe the person whose thread is linked above can join in?
 

erikgreen

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Re: Hard top from scratch

Oh, and Bond-o that's one wild set of through-hulls.

I'll give some thought to doing things with a soft-ish top. Right now I like the hardtop look, but maybe if it's too hard to make, or I get a lot better at TIG welding soon....
 

penst8grad

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Aug 23, 2007
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Re: Hard top from scratch

I think that if I were going to attack this, I would sandwich a piece of luan between 2 sheets of foam. Using epoxy as the glue and covered with glass, I think this would be both strong and light. Would also be a good excuse to learn vac bagging.

That's what I'm pondering for my doghouse. I think that the factory one is too heavy and I could save a substancial amount of weight with that setup.
 
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erikgreen

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Re: Hard top from scratch

Yeah, I've been thinking about that too. I may start by making a new doghouse before I tackle the hardtop.

If I can replace the doghouse, my manifolds and intake with aluminum, and maybe even relocate my batteries, I can balance out some of this sterndrive weight.

I like the idea of vacuum bagging, I just think it looks expensive to get into. I could build/buy a vacuum pump, but I would think you'd need specialized bagging supplies to make it work right...
 

Chris1956

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Mar 25, 2004
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Re: Hard top from scratch

First of all, Luan plywood is Phillipine Mohagony. Mohagony has natural oils which make fiberglass resin not bond well to it. Secondly, plywood has little strength to resist bending. You want bending resistance in order to support the hardtop. if you want to frame it in aluminum, great. I recommend you run a 1X2 or a 2X2 down the center of the hardtop, attached to the frame front and back, to give it some strength.
 

Mark42

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Oct 8, 2003
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Re: Hard top from scratch

Ericgreen,

That's my project on shareaproject. Just got too cold to continue and we need the garage for the cars in winter, so it is stored until spring.

I think the foam will be strong enough with 3 or 4 layers of glass. The foam is really easy to work with, I'm using the 1.5" stuff. I have ripped down 1x pine to use as the base all around where the top touches the boat. Threaded inserts are in the wood strips so screws can be inserted from below the gunwales and cuddy roof to secure it, but also make it removable.

Thats as far as I got before wrapping the boat up for the winter.

I may glass in some pine or oak strips in critical areas for strength and to attach things like radio and grab handles.

The strength of my top will be by building up the layers of glass/epoxy. Hopefully it wont gain too much weight. Just the foam only weighs a few pounds, but its just there to hang the glass on.
 

Bondo

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Re: Hard top from scratch

Oh, and Bond-o that's one wild set of through-hulls.

Ayuh,........

That's about GenVI, or GenX,........ I've lost count of the Reengineering Attemps.......
Unfortunately,.... After design #1,.... The "Looks" of them doesn't get any Better,......
Although the "Function" Is Greatly Improved........

And,......
While I Wish I had a Tig welding set up,...... I'm still doing my aluminum work with my Mig......

Good Luck....
 
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