While musing about what commercial off-the-shelf (COTS) materials could be used to build a trailer box/sail tube (e.g. thin wall PVC duct pipe, rectangular tin ducting, marine plywood w/ resin coating, etc.) I stumbled onto a pic of a 16' aluminum (Coleman?) CANOE, more lightly built than those heavy Grumman "war" canoes...
... and I thought hmmmm... cut off the rear 6', remove seats, leave crossbeams, rivet a sheet of aluminum to the top edge of the gunnels and trim to fit, turn it upside down and bolt/strap it to the trailer! It would be very AERODYNAMIC, and the only remaining problem would be fabricating a locking door. No access from the front end, but oh well.
Once upside-down, the peak of the bow would now be the low point--good spot for a drain plug.
Anyone ever try this? What problems do you foresee? Thanks in advance.
It will be butt ugly?
A lot of work for what you would end up with. I had a supplier bend/shear some aluminum for me then had someone weld the corners. Real nice box. I figured what was the max size to get out of an aluminum sheet (8' x 10' sheet). Used up every bit of the sheet and got a real nice box for about $200. I'm sure aluminum is higher now.
If I knew how to put a sketch in here I would do it. 
Clayton
Why chop up a good canoe? Just sell it for a couple hundred (I sold my aluminum canoe for $250), and just buy a sailbox. I often have used ones that I sell for $150-250, and they are pretty nice (sometimes fiberglass, sometimes metal). I'm sure Rick has some sailboxes on his site here, or just go to a metal shop and have one built. Killing a canoe is going to be 1)expensive, 2)ugly, and 3)time consuming.
Dunno how many rotting plywood trailer boxes I've seen in Florida over many years. Most of em I guess, incuding mine. There is no such thing as a NEW wooden trailer box.
Epiphytic wood-destroying fungi we'll have with us forever, as dead wood has not evolved a defense against it. Never use wood unless well-$epoxied.
Also your stuff will always fall off the flat floor and get caught under the upside-down canoe = bad idea. But look on the bright side---You are now qualified to design a war in Mess-O-Potamia! 
ReefedOne:
Yea fiberglass Performance boxes are $600 now. TOO high. Here is a link for three box designs. Two out of pipe and one out off plywood. You could probably substitute aluminum sheet for plywood on the plywood design. Have someone cut it for you and either use bent strips and rivets or weld it together.
http:/
Good Luck
Doug Snell
Hobie 17
www.tcdyc.com
Yeah, just musing... not sure why a graceful canoe is butt ugly?... I guess a canoe that did NOT leak--minimum prerequisite--would be an expensive "donor" shell, and there'd still be a door and GASKET arrangement to fabricate.
Not sure what dacarls is visualizing, but it's not a problem in my thought balloon. 
However the crossbeams would have to be removed or they'd be obstacles to sliding things across the new "floor".
With all the hurricane rebuilding going on, there's gotta be some skilled "tin knockers" in town that could bang something out in short order, maybe even from "scrap" that's been "written off"...
nothing is more butt ugly than my homemade trailer box... but who gives a crap... its a trailer box.
Guys:
YEA when I started in 1979 that was all we had!! My homemade box served me well. I used a piece of black ditch pipe about 12-14 inches around for the sails and with holes in it they dried OK on the way home. I went all over they state and it was never a problem. I have two fiberglass ones now but got them for $399 before they became to pricey. If a had it to do again I would use plywood example and use aluminum.
Doug Snell
Hobie 17
www.tcdyc.com
Guys:
Something that ReefedOne gave me the idea about in one of the other threads. Take these:
http:/
Cut the end off four of them. Us some plastic to band them together. Make some ends out of glass over plywood, put a shelf in one end for boards, blocks, etc and you have a sail box.
Just a thought.
Doug Snell
Hobie 17
Soon to be Mystere 4.3
www.tcdyc.com