Advice on Hard top construction

I posted this in another forum, but I think this is the correct one.

Hey there, I'm new here and been reading through many of the posts and I'm looking for some advice on my up coming project.

I will be replacing the soft top on my 27ft sport craft this spring with a hard top. This is new to me so I am hoping my plans will work. We are trying to keep the cost down since we don't have a lot to spend. Anyways here is what I have planned.

I plan for the project to include new windshield and side windows. I would like to build the whole structure with 1/4in marine grade plywood fit it to the boat, and then glass over it, using the plywood as a core. I can the install windows in the finished product. Will this work? I'm not sure what fiberglass mat to use, since I will have the plywood as a core I'm assuming that I won't need a very heavy mat as the wood will give it its strength. Any help would be much appreciated.

 

You can build the whole thing on a table and then just lift it on the boat and attach You are going to need some verticles ( studs) from your deck up to a top plate that acts like a window header to support your windows. You will want some curvature to the top for water run off and you must do this before glassing. Some folks like a slight inward tilt to the walls about 1/2" per foot of height looks good. If you can draw it out on grid note paper and post it with picture of where to attach it to the boat it would be very helpful and you will get much more reponse to it. Your method of attachment of the studs to the hull is critical.

 

You shouldn't use mat, it gives a very coarse finish. Also, it uses a lot of resin and makes it heavier. 1/4" plywood with 10 oz cloth will work fine. Are you also building the windshield? That is going to determine how the shape of the hardtop, so is the first step. Also, you need to reinforce the edges, because people will use them as handholds.

 

Foam sandwich is a possably lighter option, though possably more costly. Plywood as you've described would work very well. A 1x2 (or bigger, scaled for the boat) around the perimeter of the roof will offer a solid piece for hand hold and to install the supports or other items. You can build the roof to a common curve (cylindrical or conical), in which case a single sheet will easily conform (assumes a reasonable radius) or you could make a stylish compound shape, which will likely require you to diagonally skin the roof with ripped down pieces of plywood or multiple layers.

Use epoxy, which will truly seal the plywood and I'll second the use of cloth only as mat is unnecessary when using epoxy. Go down to the local Lowe's/Depot and pick up a couple of sheets of door skin material, which is thin and easy to bend. Use duct tape or ratchet straps to bend it to the desired curve and get any idea of what will fit and look good. With this in hand, you can make a "buck" to bend the plywood over and apply the outer layer of 'glass.

 

Thanks for the answers, I will look into the epoxy, if I can get away with out using the mat that would be great. I will post some sketches of my design when I get them complete, along with some pics as the project progresses. I know I will have many more questions as I get going.