Canoe Rack

I have a topper Centennial aluminum truck and a boat 15 'fiberglass. Can I carry the canoe on top of the upper layer without having to buy a roof rack?

You might want to get pads for the truck canoe. And 4 blocks of dense foam adjustment on the gunwales and a skid pad on the bottom. You still need to tie, but they are cheap and fast.

I do not think it's a good idea, you should spend a little money.