car top hull up or down??

[Tim Reardon]

I've seen pictures of car topping single shells with the hull side up and hull side down. Which is correct?

[Dick White]

On Tuesday, June 29, 2021 at 6:49:33 PM UTC-4, Tim Reardon wrote:
> I've seen pictures of car topping single shells with the hull side up and hull side down. Which is correct?

If you are not going far in a single day of known good weather, it shouldn't matter. If you are going a distance in uncertain weather, you don't want the hull/cockpit to fill with rain water, so hull bottom up. My "official" Vespoli rack is designed with the slings tight enough that I probably couldn't hold it level on its keel, but the deck fits nicely in it. There is an opinion that at high speeds, some wind over the car roof might blow up into the cockpit, creating stress. But the rack and boat have successfully gone from Virginia to Alabama, a distance of ~700 miles with no discernable issues. Others have boat bags to protect the boat.

[bnw...@gmail.com]

Agree with above, but equally, if not more important, is the proper method to secure the boat to the vehicle during transit. I transport daily approx 7 miles each way. I use round marine grade 7/16" diameter bungee cord loops at each sling location to hold the hull in place upside down. If traveling a significant distance, in addition, I secure the bow to my front bumper with cordage, and throw 2 straps, 1 fore and 1 aft of the cockpit, to the vehicle roof rack.
Not saying this is the best/only way, but it has worked well for me for the past 5 years or so.

[Marc Messing]

I would check first with the builder.

As to the cordage/strapping issue, however, I'll offer my own suggestions, for what they may be worth. Any cordage that doesn't stretch -- especially when wet -- will work, but webbing should be easier on the hull and the finish. More importantly, in my mind, is that elastic bungee cords are more appropriate for holding the bow and stern rather than securing the boat to the car. The reason for this is that the flex I see when I'm cartopping is actually a result of flex in the cross bars. The webbing is holding the boat securely and the hull is remaining rigid, but the bow is rising and falling as a result of flex in my forty-year-old Yakima bars. The purpose of cords or bungees on the bow is primarily to prevent right/left sway and act as some sort of a safety strap.

[carl]

Hi Marc -

Much interesting stuff in your adjacent thread - thank you - but as
someone who does a fair bit of car-topping I 'd like to make a few
slightly contrary points.

1. I would always carry a boat upside-down. There are usually
stronger, safer contact points along the sheerlines (deck edges) & less
chance of the boat rotating in slings.

2. If inverted, the boat can't collect water on a rainiy day, or dirt.

3. Webbing straps have a couple of snags. Folk tend sometimes to
overtighten them - because they can - which is not great for the boat.
If they have diecast buckles and someone drives over them (as does
happen) those buckles can fracture. And the straps can be quite hard,
which can mark the surface, and if they pick up dirt they hold it in the
weave which can really scratch the hull.

4. If the bars are too springy, if possible move the rack to the side
where their deflection will be much reduced.

5. I would never use and elastic tie-down for the ends of the boat.
The purpose of the additional tie-down is to prevent self-sustaining or
amplification of the pitching moment of the racked boat (see springy
roof bars), which it does by preventing the upwards bounce For that you
need a rope, not an elastic cord. Further: never take the end tie-downs
to the ends of the boat - it's not necessary, while extending beyond the
vehicle presents an unexpected hazard to anyone passing beneath the boat
(as they do!) & thus a danger to the boat. And it maximises the bending
stress in the boat.

That said, I can't speak too highly of your work on RowSafe.

Cheers -
Carl
--
Carl Douglas Racing Shells -
Fine Small-Boats/AeRoWing Low-drag Riggers/Advanced Accessories
Write: Harris Boatyard, Laleham Reach, Chertsey KT16 8RP, UK
Find: tinyurl.com/2tqujf
Email: ca...@carldouglasrowing.com Tel: +44(0)1932-570946 Fax: -563682
URLs: carldouglasrowing.com & now on Facebook @ CarlDouglasRacingShells

[Marc Messing]

I don't disagree with any of your points, though I'm unclear about this last one: "Further: never take the end tie-downs

to the ends of the boat - it's not necessary, while extending beyond the vehicle presents an unexpected hazard to anyone passing beneath the boat (as they do!) & thus a danger to the boat. And it maximises the bending stress in the boat."

In practice my standard for tying all boats and other sorts of other things has always been 5mm cord, tied with a trucker's hitch so that the tension can be carefully controlled. On rare occasions I use an untensioned bow line to prevent lateral sway.

The gimmick that I use to prevent people, including myself, from bumping into the ends of the boat is to drape a loose line from the end of the boat to the rack, hanging about 6" below the boat. Usually I see that before I hit my head. Usually...

Marc

[carl]

On 21/10/2021 16:06, Marc Messing wrote:
> I don't disagree with any of your points, though I'm unclear about this last one: "Further: never take the end tie-downs
> to the ends of the boat - it's not necessary, while extending beyond the vehicle presents an unexpected hazard to anyone passing beneath the boat (as they do!) & thus a danger to the boat. And it maximises the bending stress in the boat."
>
> In practice my standard for tying all boats and other sorts of other things has always been 5mm cord, tied with a trucker's hitch so that the tension can be carefully controlled. On rare occasions I use an untensioned bow line to prevent lateral sway.
>
> The gimmick that I use to prevent people, including myself, from bumping into the ends of the boat is to drape a loose line from the end of the boat to the rack, hanging about 6" below the boat. Usually I see that before I hit my head. Usually...
>
> Marc

Hi Marc -
Taking a cord to the very end of the boat increases the bending moment
on the hull while simultaneously increasing the length of the line from
car to boat & thus its extensibility. But it doesn't reduce the
side-sway, nor does it so adequately reduce the vertical bounce (which
is due largely to roof-bar flexibility, not to the flexibility of the
boat). It's best not to use the leverage of the full length of the boat
and add to its structural loads just to stabilise flexible roof bars.

A slanted rope that's twice as long as the vertical rope from the bumper
(typical for a rope run to the bow from the bumper) is a much less
efficient way to restrict vertical motion, & it applies 70% more
longitudinal force to the boat than its vertically restraining effect.

And that you recognise the need for adding something visible to warn
aware of the potential hazard acknowledges the (unnecessary) hazard to
boat &, e.g., cyclist or pedestrian of running the rope to the bow. If
it ain't necessary, gives no benefits & can be hazardous (any number of
people still won't see the rope), then best not to do it?

Cheer -