Roofrack wind deflectors

Submitted: Saturday, Jan 15, 2005 at 16:03
ThreadID: 19399 Views:1622 Replies:9 FollowUps:11
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Got hold of a secondhand TJM steel full size roof rack for the GU. All good, but makes a bit of wind noise at highway speeds as expected.

Do those angled wind deflectors at the front leading edge of roofracks make a noticable difference to noise / fuel consumption, or are they just for show?
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Reply By: Lone Wolf - Saturday, Jan 15, 2005 at 16:05

Saturday, Jan 15, 2005 at 16:05
Dunno.

But they LOOK good, and that's enough reason, ain't it?

Wolfie
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Follow Up By: V8Diesel - Saturday, Jan 15, 2005 at 19:05

Saturday, Jan 15, 2005 at 19:05
"I'm gonna make mine a RED ONE Edwin...."
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Reply By: GO_OFFROAD - Saturday, Jan 15, 2005 at 16:08

Saturday, Jan 15, 2005 at 16:08
If designed correctly, they can improve noise, and air flow, but the most important part is the distance from the vehicle roof, to the bottom of the roof rack, where most of the noise is generated.
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Follow Up By: V8Diesel - Saturday, Jan 15, 2005 at 19:04

Saturday, Jan 15, 2005 at 19:04
Roachies is 40mm from roof to bottom of deflector. How close should it be do you reckon?
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Follow Up By: GO_OFFROAD - Saturday, Jan 15, 2005 at 19:24

Saturday, Jan 15, 2005 at 19:24
well, its not how close it should be, but where it deflects the air, as the mesh floor of the roof rack is normally where alot of the noise comes from, so the air needs to be directed to the outside, not down and under the rack.

Take a look at what ARB does with some of its racks now, especially the 120 series one to help with noise.

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Reply By: Member - JohnR (Vic) - Saturday, Jan 15, 2005 at 17:07

Saturday, Jan 15, 2005 at 17:07
V8, I found my basket made quite a lot of noise until I had something in it or exentually sliced a section of 160mm stormwater pipe and hold it on the front with cable ties. Painted black is ok until the stone chips take the paint off and it is a good place to put your EO sticker..

I found the noise seemed to come from the back of the basket when I had stuff in it even, before I put the deflector there.
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Follow Up By: V8Diesel - Saturday, Jan 15, 2005 at 18:59

Saturday, Jan 15, 2005 at 18:59
Like your thinking JohnR, I'll give it a go. Cheap and easy.

Thinking about putting a whole pipe up there now and using it as a water tank for a gravity feed hose. Kill two birds with one stone.

Nice rig too by the way.
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Follow Up By: Member - JohnR (Vic) - Saturday, Jan 15, 2005 at 21:35

Saturday, Jan 15, 2005 at 21:35
Thanks for the compliment V8D. I would be cautious about having a 20-30 kg fluid capable of moving from side to side easily or that much high up at all even though a lot do. Think of putting in baffles open at the top and bottom to allow small volumes to move.

Yes, it was inexpensive for me too, using about 190 degrees of the circle covered the whole of the front back to the second row of wire of the basket. Depending of your structure of your basket or rack you could try to smooth the airflow top and bottom of the pipe backwards a little.
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Reply By: Member - Roachie (SA) - Saturday, Jan 15, 2005 at 18:05

Saturday, Jan 15, 2005 at 18:05
The big aluminium deflector I put on doesn't seem to have reduced the noise factor, but maybe the 40mm (approx) gap I've left between it and the roof has something to do with it....might try and move it down another little bit...

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Follow Up By: V8Diesel - Saturday, Jan 15, 2005 at 19:02

Saturday, Jan 15, 2005 at 19:02
Roachie, that was what I was initially thinking of knocking up on the bender from road sign aluminium.

Let me know how it goes when lowered.

Cheers.
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Follow Up By: Member - Roachie (SA) - Saturday, Jan 15, 2005 at 19:46

Saturday, Jan 15, 2005 at 19:46
G'day again mate,
Well, I've just been out and "done the deed"...so to speak. My wind deflector is simply attached to the front of the ARB rack using 4 muffler clamps (now quite rusty cos I used plain steel instead of gal'). So all I had to do was loosen them off and push in at the bottom of the deflector until it almost touches the roof. I bought the aluminium as a plain rectangular piece, but the bloke offered to put 2 small bends in it at the lower edges, so it conforms to the curve of the roof better than you'd imagine; in fact the 2 edges are about as close to the roof as the centre. Maximum gap is now about 20mm and minimum is about 3mm.
Will post results on here once I've road tested it tomorrow.
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Follow Up By: Member - JohnR (Vic) - Saturday, Jan 15, 2005 at 21:41

Saturday, Jan 15, 2005 at 21:41
Roachie and V8D you could use irrigation hose clamps, they can be stainless or plated and heavy duty and would go over whatever size you want. I have some at 120 mm and 140 mm in use now but not for that purpose.
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Reply By: David Au - Saturday, Jan 15, 2005 at 20:00

Saturday, Jan 15, 2005 at 20:00
I don't think anything saves from the fuel hit of a roof rack.
I tried all sorts of shapes and style. While I did manage to kill some of the noise, nothing helped the massive hit on fuel consumption. I would not have another roof rack.
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Follow Up By: Bonz (Vic) - Saturday, Jan 15, 2005 at 21:50

Saturday, Jan 15, 2005 at 21:50
David, whatd u do in the end to reduce the noise? I have recently lowered mine 50mm, but its still noisy.

Thanx for you reply
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Follow Up By: David Au - Sunday, Jan 16, 2005 at 00:22

Sunday, Jan 16, 2005 at 00:22
Bonz we fitted sheet metal deflectors of various shapes and places. I owned a steel manufacturing business at the time so bent up different configurations. By the time we got rid of the noise it certainly did not look all that great. We expected once we got better air flow and reduced the noise we would get better fuel consumption - wrong.
Perhaps if we had somebody that new more about aerodynamics we may have been able to get rid of the noise and improve the fuel consumption. I think we lost in the order of 2.1kms to the litre. Speaking to others with full roof racks that appears normal. The roof rack did not stay on for to long.
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Follow Up By: Bonz (Vic) - Sunday, Jan 16, 2005 at 00:24

Sunday, Jan 16, 2005 at 00:24
Thanx David, planning on a roofrack addition across the Simpson, might just put up with the noise then
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Reply By: D-Jack - Saturday, Jan 15, 2005 at 21:43

Saturday, Jan 15, 2005 at 21:43
I agree with most posts - have experimented a little and no difference. Bloke at a 4wd shop said the same. However, one of their best functions is to keep bugs/bees/moths from hitting your lugguage on top and splattering their guts all over it. Ever been through a locust plague - you'll be glad you had a wind deflector. Believe it or not, also helps keep lugguage up the front a little drier too in rain at hightway speeds.

D-Jack

p.s. I hear Hiclones are good for fuel consumption!
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Reply By: Willem - Saturday, Jan 15, 2005 at 22:03

Saturday, Jan 15, 2005 at 22:03
I have a clear plastic wind deflecter on my RR It came with the RR. Get no noise from the RR so the deflector must work to some extent.
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Reply By: Member - Captain (WA) - Sunday, Jan 16, 2005 at 00:17

Sunday, Jan 16, 2005 at 00:17
Hi V8Diesel,

I had an ARB rack on my 80 series and always found it very quiet. Then my mate borrowed the rack for his 80 series and complained how noisy it was. Went for a test drive and couldn't believe how noisy it was in his cruiser (rack was in same position). But then we realised I had a sun visor on my cruiser and it must have deflected the air over the rack just right to stop any noise.

When i got my patrol, I transferred the rack across and it was one noisy bugger. Have ended up putting a 160mm black HDPE pipe cut in half across the front (see rig pic below) and it makes all the difference.

I think its a matter of experimentation to get the deflector to flow the air right to stop the noise. Roachie has one big deflector yet sounds like it doesn't perform as well as the small half pipe types. Will be curious to read Roachies results after lowering closer to the roof (I think it actually may be worse, but will read about it soon enough!)

Cheers

Captain
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Reply By: V8Diesel - Sunday, Jan 16, 2005 at 00:38

Sunday, Jan 16, 2005 at 00:38
Thanks for all the responses folks, I'll start buggerising around and report back. Looks like pipe gets the nod at this early R&D stage due to low cost and positive feedback.

Big fan of the K.I.S.S. theory myself.

Cheers

Dono
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