fiberglass and ply hardtop build question...

Whoa, 24oz roving is way heavy and not needed, it'll just add a lot of weight, soak up a lot of resin and be extra work. You're not so much looking for the laminate to add structure as you are increase durability.
I'd shoot for around 6oz cloth, somewhere around there, or as PAR suggested 4-8oz. When doing it you're likely not going to find cloth wide enough to do your top in one piece. If you have to do a lap make it about 3". Also assuming you'll wrap the cloth around the edges, if you want wrap from both sides, that will get you 2 layers around the edges and corners, that's where things usually get beat up.

 

yeah I think the 24 oz is too much. will wrap it if I can and will over lap.

 

I thought you might want to rest your outboard motor on it. lol

 

To get some "purchase" on a cambered roof, use a table saw and lop the top of one of the 1x2's at the angle necessary.

Shown here is a 1x2 on it's flat with a 9 degree angle on it's top face. This is glued and screwed to the curved plywood. The camber is 3.5" (height of a 2x4) across 7', which make a nice roof crown.

If using some 1" tubing (shown) then you might want to use a 2x2 instead around the edges, so the tubing has a better "bite" on the perimeter frame (shown on right). The curved thing on the left is a length of "hollow back half oval", which will cover the end grain, fabric edge and makes a nice trim piece, that can take a beating too.

To bend the plywood, use a 7' long piece of something thin and moderately flexible. Place a 2x4 on edge at it's center then weight the ends so they touch the ground. Trace this curve on some scrap plywood and cut out. This is your "crown" template. Make a few of these by cutting some 1x4's to the same curve. Across 7' you'll only need 3 or 4. Stand these cut 1x4's on edge and screw them to something serious, that's not going to mind some weight or other torment. With your crown "jig" established, toss the plywood pieces over it and weight them down (or use temporary screws) so they hit the curved portions of the jig.

Now you can setup for your perimeter frame. Layout the sides with the angle on top so they'll align vertically to the tubing. Glue and screw these in place. At the front and back you can bend in a piece or saw to shape. These also get glued and screwed in place. If you want some beams, do the same as the front and back pieces of the perimeter frame.

The centerline seam can be a butt joint, scarfed or a "Payson butt joint". All will work, the butt joint the simplest, the scarf the neatest, but requiring some wood working skills.

To 'glass it over, any temporary screws will have to come out of course. The centerline seam sanded smooth any dings, divots or screw ups filled, etc. A 4 or 6 ounce cloth looks much like a canvas top if you don't fill the weave. It'll add some abrasion resistance too. You don't really need it, but it does have benefits. You can also use canvas, glued down with PVA (TiteBond III) or oil based paint. You can also use light 'glass cloth (4 - 6 ounce) and set this in PVA glue too. All of these coverings will need painting to protect from UV.

 

I thik I attached a pdf drawing of the edge (sort of a drawing) of the down angled edges. wrap this in glass shuold be good?

 

Don't forget the products made for securing your perimeter canvas windows:



They work like a charm and with the matching bolt ropes in the canvas panels make short work of pulling the gear for sunny days & storage off season.

 

hmmm...interesting...where from and what is i it called?
I was thinking of snaps with velcro between.

 

Here is one supplier:

http://www.sailrite.com/Awning-Track-Flanged-White-96

They also have it in AL for half the price.

See the matching bolt rope products for the canvas side.

 

PAR shortend the Job for you.

I have two questions on a job like this:
Is there a compound that can be sprayed onto the Canvas top to effectively turn that Canvas into a sheet of pliable waterproof Rubber like Rag top?

And one more:
Why couldn't the operator wet the Canvass down, apply a coat of Fiberglass Cloth, and wet it all down, to make a fairly solid Hard top?

 

Yes, my method makes the perimeter frame and the attachment points for the tubing all one assembly. Simpler is usually better, unless looking for a soul mate.

You could try an elastomeric compound on canvas, but this is an expensive way of doing things.

As to wetting down some canvas (assuming resin), I'm not sure why you'd want to do this, a 'glass laminate would be much lighter and of course stronger. Canvas would act like a sponge and you'd use lots of resin.

About my sketch above, you could attach the tubes to the inside edge of the perimeter frame if preferable, instead of a mortise as shown.