Surrey top

[Full Tilt]

I am planning to build a surrey top as seen on antique motor launches for my 17' skiff and am considering my options.
The top will be elliptical in plan form to correspond to the boats cockpit coaming and will match the sheer longitudinally. The frame will probably be 1/2" aluminum tube and consist of the potato chip shaped perimeter and 3 or 4 athwartship bows to give it some crown. The uprights will either be bamboo or cedar. I'm thinking the uprights will have brass ferrule end caps at their bases with a circular plate brazed to them for fastening to deck. The ferrule will be attached at an angle to the baseplate to compensate for the sheer in the deck, allowing the posts to be plumb. Six posts seem to be the correct number. I can install threaded brass inserts into the deck to accept the bases, just outside the coaming. The middle pair of uprights would attach to the gunwhales and couldn't have a base plate, just room for a threaded insert.
I think you get the idea. Has anyone any first hand experience with surrey tops or ideas that might be helpful.
I'm fairly handy with canvas and would like to do the work myself.

Thanks,
Mike

[JimConlin]

I'd be concerned that someone will grab the verticals and think that they were strong enough to heave on.
1/2" aluminum tube won't withstand that.
I'd suggest 1" (maybe 7/8") stainless tube.
At the bases, I'd design for the tube going through the deck to the bottom of the boat beneath. Getting a strong enough connection fastened to the deck would require serious blocking and an overzealous tug could tear out some deck.
There are good tee fittings for the stainless tube joints at the top. Borrow a conduit bender to form the top bow.

[BBSebens]

Agreed with Jim. They need to be strong enough to be a grab handle. It'll happen at some point.

I do like the thread in base idea. If you went with something like an Atlas thread, you could get good bite without an hour of hand turning.

[Full Tilt]

Thanks Jim, but stainless would be too heavy for this little boat. The uprights will be wood or bamboo, I don't want any exposed aluminum. I was given some half inch aluminum tubes today, old catamaran battens, and I have access to a friends bender. I hope I don't need to anneal the tubing to bend it into a 20" radius, never bent the stuff before.
Big holes through the deck aren't going to work for me either. I know what you're saying about strength, I may need gussets or guys, or both. I hope a bamboo upright doesn't give the impression that it can be wrenched on.
The tees make sense, but I doubt I'll find them in aluminum. Plastic or copper tees would probably work for the roof bows and on the tops of the uprights. They will be hidden under the canvas.
I'm trying to figure out how to attach the canvas. I think grommets and lacing are probably the best way, since tension can be adjusted, but the lacing would need another tube to lace to. I envision a lozenge shaped aluminum frame with a second smaller inner lozenge shape providing something to lace around. The scalloped edge would be a separate sewn on piece.
Mike