Canopy construction

[balefish]

Has anyone out there built a composite canopy for a medium size vessel? I wish to build a hardtop, free standing cover at the stern approx 1800mm, this will extend approx 1000mm at the front. I do not wish to have posts at the stern of the boat for support have spoken to a few people and they commented that if it was built of stainless it would move perpendicular to the boat ant crack, the wieght to have it strong enough would out weigh the benifit. Any help greatly appreciated.

[mal555]

Any upper structure will have quite an amount of tranverse movement, flex as the vessel runs at planing speeds through choppy seas.

I fitted a 2.4m x 2.0m x 2.5mm (thick) alloy cockpit HT, supported at the rear near each transom corner by two, near vertical (laying slightly forward) 40mm alloy tube sections, running parallel, braced by two short 25mm dia. horizontal lengths.
The structure has been in place for seven years now, and even in the roughest conditions (with an inflatable dinghy on top) there has been no sign of fatigue or damage and the powder-coating is fine. I find the rear supports useful to hold onto when climbing in and out etc.

The forward section of the HT is attached to the GRP cabin.