# Trailer Aerodynamics



## johnandcharlie (May 2, 2007)

As the last discussion on trailers was in panel van conversions, and this is similar, I'm putting this one here too.

I've just been measuring my trailer to work out how to convert it to carry all the stuff that won't fit in my van. It's currently got 12" high galvanised sides, and I want a box about 7ft long, 4ft high and 4ft wide. I'm planning to build this out of plywood. I can taper the sides from front to back, and the top in any direction, and will probably slope the top anyway for water to run off. This will make it more complicated to build though.

Do I need to worry about shaping it to improve aerodynamics, or will a rectangular box be OK?
Will it have much effect on handling and fuel consumption?


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## johnandcharlie (May 2, 2007)

Looks like no one knows!

I looked at a lot of web sites last night, but they didn't help much. If the trailer has a smaller front profile than the van will it be OK? Do I only need to worry if it's being towed by a car?

I need start building it in the next few days.


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## Scotjimland (May 23, 2005)

Hi John

Personally I wouldn't be overly concerned, most box trailers I've looked at are just that.. boxes. 

My new trailer has a moulded fibreglass front which houses the spare wheel and gives the trailer a sleeker look but as far as aerodynamics are concerned I doubt it has much effect, especially behind an RV. 

Fuel consumption won't be overly affected, I've never noticed any huge difference, it will affect it less than a roof box.. 

As you suggest, if pulling behind a car it may be more important.. and lets face it, motorhomes are not know for good aerodynamics.. :lol: 

Good luck with the 'build' 

Jim


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## 100004 (Jul 12, 2006)

Keep it simple, as areodynamics don't really make that much difference until speeds higher than you'll probably be doing. The important thing is CdA., which is the area offered to the air. As the trailer will be behind the van, obiuosly it will be the van's Cda that's important and you can't do much about it. If anything it's about turbulance and smoothing the airflow after the trailer and, with starting with a square, is most definately not the best starting point. If you really are interested, just have a look at caravans rear ends and you'll see there's not a lot that can be done. H


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## johnandcharlie (May 2, 2007)

From the stuff I looked at yesterday it seems sloping it towards the back helps. I'm aiming to slope the top as much as possible, but it won't be much, so the rain runs off. It's almost level attached to the van and I'll probably keep it attached to the van, with a hitchlock, whenever I can on site.


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## 100836 (Sep 3, 2006)

johnandcharlie said:


> From the stuff I looked at yesterday it seems sloping it towards the back helps. I'm aiming to slope the top as much as possible, but it won't be much, so the rain runs off. It's almost level attached to the van and I'll probably keep it attached to the van, with a hitchlock, whenever I can on site.


i would forget aerodynamics as you wont have smoothed airflow over the corners so it wont make any difference anyway, i would concentrate in making the trailer as load efficient as possible for what you want to carry. always err on the slightly bigger size as you may find you need to squeeze more in there.


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## maddie (Jan 4, 2006)

Hi don't worry about areo-dynamics asyour van punches a big hole in the air and your trailer follows,a bit like driving a truck up another trucks behind the wind drags it along if close enough.I saw a lovely looking trailer 2 weeks ago which had the top made from a roof-box top,all painted to match the van,realy nice.Wish I had taken a pic now.
terry


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## 100004 (Jul 12, 2006)

That's the right idea J, as it keeps the aiflow attached and if you did the sides,then you could be getting somewhere. trouble is, you then start eating into your volume and that would mean you would have to go longer to keep the same volume Remember, the best aero shape is a teardrop, so it would be a funny looking trailer. Aero though!  Ask Charlie, he'll tell you if you're barking up the wrong tree   H


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## johnandcharlie (May 2, 2007)

I bought the plywood this afternoon. It will have to be more or less a rectangular box. I don't want to make it too high so I can still see out of the van rear window, but the bike has to stand up in it. I'll do a quick job on it for now and see how it works. It can always be rebuilt later. Thanks for the help.

Charlie's no use, he's never done a useful thing in his life :lol:


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## Spacerunner (Mar 18, 2006)

Maybe a pitched lid would help. It would shed the rain and would give you height in the middle to stand the bike.


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## johnandcharlie (May 2, 2007)

Spacerunner said:


> Maybe a pitched lid would help. It would shed the rain and would give you height in the middle to stand the bike.


I'd thought of that. I'd have to buy more wood, as they're 4ft wide sheets and the trailer is 4ft 3in wide. I was just going to taper the sides slightly. It's a mountain bike with wide handlebars and sticky up bar ends, so I'm not sure a pitch is practical, but I could add gutters and build in a water butt :lol:


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## Spacerunner (Mar 18, 2006)

Don't forget the stove pipe!! If you turned the handlebars 90 degrees it should fit, maybe.


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## johnandcharlie (May 2, 2007)

Spacerunner said:


> Don't forget the stove pipe!! If you turned the handlebars 90 degrees it should fit, maybe.


Wood fuelled heating boiler for the van. I could build in an oven too :lol: I don't want to keep loosening the handlebars. I'm putting a guide rail on the floor for the wheels and I can whip it out, peddle off to the shops or pub and whip it back in again. You should hear the noise when Charlie knows we're going cycling. I need to make a quick exit from the camp site before he wakes everyone up :lol:


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## 100004 (Jul 12, 2006)

There was me thinking this was serious  Put the lad on J and then I can ask if he's been to Wooferton. Serious! H


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## johnandcharlie (May 2, 2007)

It did start off serious. I just got a bit sidetracked with interesting things I could do to the trailer :lol:. It's parked in the garage tonight so I can work on it in the dry tomorrow.


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## 100004 (Jul 12, 2006)

Best of luck! Let's hope you have fun and the end result is what you want. Stick some pixs of it on when you're done. H


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