Roofbox- roof secure?

[Chunkymunky]

Hi all
I’m In the process of attaching my Thule motion 900 to the roof for a trip to Europe in the next couple of weeks - now ( I think) I’ve thoroughly researched the subject re weight limits etc ( roof won’t be being raised anyway , whole shaboodle should weigh <50kg), and I know lots of people puts lots of exciting junk up there, but I’m a little concerned / interested in how the roof actually “ secures” to the body when it’s closed down and finished making that “ whirring sound”! Is it latched internally? Or just held down by the inverse ( reverse?) forces of the hydraulics? I’m a bit worried of the forces exerted on what’s a big old roof box as I hurtle down an autoroute!
ps It’s an ocean! Cheers

 

[steve_b]

My understanding is that the whirring after the roof has stopped moving is the latching, it is held shut by much more than luck otherwise failed hydraulics would give you a sail.

You should have a set of hold down straps in the van somewhere for emergency use if you have to bleed the hydraulic fluid to lower the roof, which doesn't complete the latching process. Could use them as a belt and braces for the first run if you are paranoid.
They sit in the rails and hold the roof to the pillars - two bits of plastic and a velcro strap for each side , from memory.

 

[Chunkymunky]

My understanding is that the whirring after the roof has stopped moving is the latching, it is held shut by much more than luck otherwise failed hydraulics would give you a sail.

You should have a set of hold down straps in the van somewhere for emergency use if you have to bleed the hydraulic fluid to lower the roof, which doesn't complete the latching process. Could use them as a belt and braces for the first run if you are paranoid.
They sit in the rails and hold the roof to the pillars - two bits of plastic and a velcro strap for each side , from memory.

Cheets Steve.
I thought the whirring must have been some form of locking system. I haven’t seen the manual roof on beaches or conversions etc so didn’t know what secured them internally either .
I’ve Got the emergency straps- and it was the thought of such a hydraulic failure that got me thinking! Even with them, it’s basically just a bit of Velcro buttoning the whole thing down isn’t it?
you see kayaks and boats and boxes etc up top and there must be some tremendous external forces involved at speed. -it’s not that I’m paranoid , the box is going up there come what may,! I just would like some understanding of what’s keeping the thing in place before I boot it down the A26!

 

[Amarillo]

I haven’t seen the manual roof on beaches or conversions etc so didn’t know what secured them internally either.

The Beach has a pair of robust clamps holding the roof down. There are also a pair of independently fastened safety clips in case the clamps fail.

I have no doubt that the Ocean has an equally robust system for locking the roof in place.

 

[Ch1pbutty]

Roof boxes don’t create any lift so no need to worry.

 

[Chunkymunky]

Roof boxes don’t create any lift so no need to worry.

Now your talking! it’s obvious really I suppose otherwise there’d be massive impacts on mpg and cars would be taking off like The Jetsons.
I knew there’d be some aerodynamical reasoning that someone ( brighter than me) would know about! If only I’d paid more attention in physics

 

[Chunkymunky]

So now then, a further query. In the interests of aerodynamics , MPG , and (being able to open the tailgate!) thoughts on positioning. As far forward as possible or as far aft?

 

[Ch1pbutty]

So now then, a further query. In the interests of aerodynamics , MPG , and (being able to open the tailgate!) thoughts on positioning. As far forward as possible or as far aft?

It’s not so much of an issue with a van as the roof is nice and long so you can avoid any overhang. I find it’s best to have the centre of the box lining up the sliding door cill as it makes it easier to load; If it opens on the wrong side, then stand on the the front cabin / rear tyre.....Roofbox bags are good as makes for a quicker load & easier to close the box.

Hapro roof box bag set no. 29775

Full set of four bags to make the most of your roof box space. They are a useful addition to any brand of roof box. The front bag is specially shaped to fit perfectly in the tapered front of the roof box. The three other bags can be used behind the nose bag to make the most of the space inside...

www.roofbox.co.uk

 

[Chunkymunky]

It’s not so much of an issue with a van as the roof is nice and long so you can avoid any overhang. I find it’s best to have the centre of the box lining up the sliding door cill as it makes it easier to load; If it opens on the wrong side, then stand on the the front cabin / rear tyre.....Roofbox bags are good as makes for a quicker load & easier to close the box.

Hapro roof box bag set no. 29775

Full set of four bags to make the most of your roof box space. They are a useful addition to any brand of roof box. The front bag is specially shaped to fit perfectly in the tapered front of the roof box. The three other bags can be used behind the nose bag to make the most of the space inside...

www.roofbox.co.uk

Cheers chipbutty
I know it seems ( is) a daft query regarding the positioning as it’s sitting on a big un- dynamic brick anyway- just checking I’m not missing anything
I’ve previously used the box several times on an a6 avant and a q5 and had no choice over where it went. It just went where it would fit- on the plus side then, as it overhung at the front I could check it hadn’t fell off!