Step 5: Building the Rack, Part 3
E -- Loosely lay out the cross-bars on the rails, spring clamp, think about it, and draw pencil marks where you think (1) they all attach, and (2) where any load-attachment holes will be drilled. You will need holes for the straps holding rack to roof, and holes for rope loops, eye-bolts, eye-straps, etc., for strapping loads to rack.
Note -- I like rope loops (3/8 inch, and tie them with nonslip knots, especially the bowline bend or some other) because they are cheap, strong, flexible (will not damage load if you rub against them), and easily checked and replaceable. You can paint the nylon rope loops if you think UV damage will degrade them sooner than wear and tear.
F -- Now assemble on your roof loosely and think about it. Make final adjustment and change your marks if needed. Simulate the way you will load your loads (such as kayak) so that the rack will intercept all bashing, damaging, angered motions of the loading event. If you want to spend more money, now is the time to buy or build rubber rollers to help load the kayak on the rear cross-bar, or install plastic slidey things.
G -- Now level the assembly on the roof if you did not scribe the roof curve on the rails. I used wood wedges to level the rack on the roof by lifting the rear end of the rack, took the measure-ments, and built spacer blocks (angled to the roof angle) by laying the blocks against the wedged up wrack and drawing the outline of the relationships on the blocks. Finally, I shaped the blocks, glued them one the rails, and reinforced them too with a 3/8 wooden dowel glued into block and rail. The photo shows the spacer blocks leveling the rack as well as the illustration for the Step J, 'test load your kayak.' Just trying to save Instructables' data space.
--photo of kayak leaned on the rear cross-bar
H -- Then glue and screw the whole assembly. Sand and paint.
I -- The final step is to cut your foam pads to wrap around the front rail and the rear leveling blocks. I used stainless steel screws and washers to attach the pads (the washers prevent tear out).
--photo of the foam pads being screwed on