To elaborate on what James says:
Whatever you do on the road, you owe a duty of care to everyone else
whose lives you may affect.
A sculling boat is not unlike a javelin - long, stiff, pointy & affected
by air currents. If insufficiently secured it can slew diagonally,
pitch with an oscillatory motion of growing amplitude or be ripped off
if the wind forces exceed the restraint capacity. Then you, &/or some
innocent person, are in deep trouble.
With something ~8 metres (or more) long, although very stiff &
remarkably strong, ensure that its points of attachment are well apart
lengthwise, & more than the typical spacing between car roof-bars. So
you need a bolted-on boat rack. These are typically 2.2 metres long (or
more), stiff, & with vee structures at each end - either with slings or
padding - to cradle the boat.
If held in padded vees, the boat should travel inverted as the deck
edges (sheers) are the hardest, stiffest part of the boat & can take the
loads. And an inverted boat won't collect rain-water or detritus.
Tie the boat firmly but not too tightly, & always with 2 ties at both
end positions. It's not necessary to tie down in the middle. With
ratchet or other webbing tape straps do _not_ overtighten. As with
rigger bolts, being strong is no reason to use bolts or tie-downs to
prove your strength! "Gently secure" is good & won't come loose; with
straps you can do lasting crush damage to any boat. Personally I avoid
webbing straps like the plague: they're surprisingly abrasive, easily
overtightened & their die-cast buckles are a pain to thread the end of
the strap though & vulnerable to fracture in use (usually after someone
had driven over them on the ground). IMO, far better are bungee cords,
in loop form - quick to attach, kind to the boat, strong & forgiving.
but always use straps or bungees in pairs.
Pitching: Your boat can oscillate for 2 reasons: a) the roof bars are
too flexible or b) its very windy (& passing a truck can mess with the
air flow). An oscillation, once started, can often grow as the further
out of line the greater the aerodynamic loads that sustain its movement,
with the potential to rip the boat off the rack.
With flexible roof bars the immediate answer to wobbliness is to mount
the rack close to the ends of the bars (tighten but don't overtighten
those bolts). And a rational precaution (sometimes mandatory) is to
also _lightly_ tie down the forward part of the boat to the front towing
eye. For this, do _not_ take the cord forward to the bow of the boat as
that not only stresses the boat & is less effective (being longer, it
stretches more), but because it won't be easily seen by a passing
cyclist or pedestrian, neither of whom wants to be garotted when
crossing in front of your stationary vehicle. So take the cord
vertically down, & have it just tight enough not to be slack. Then if
the boat starts to pitch the cord will kill the upward motion & thus
prevent sustained & amplifying oscillations.
Also check overhangs & legislation. Some national traffic regs require
a passenger if you have over certain overhang length & some others are
very prescriptive. Best to carry printed copy of the relevant
regulations as many traffic cops don't know about car-topped racing
shells. And properly flag both ends of the boat (lights at night).
Carl Douglas Racing Shells -
Fine Small-Boats/AeRoWing Low-drag Riggers/Advanced Accessories
Write: Harris Boatyard, Laleham Reach, Chertsey KT16 8RP, UK
& now on Facebook @ CarlDouglasRacingShells
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