Shape of trailer body

[farm1810]

I was reading on another website about tow behind trailers. One person highly recommended a design that has the sloped front (toward the motorcycle) rather than a more flat front, possibly tapering at the rear. The reason given was, at speed the wind will tend to push the flat facein a way that lifts the tongue and rear of the motorcycle. The sloped front tended to use the force the wind at speed to apply down pressure. Has anyone here experienced either of these conditions?

[MiCarl]

My trailer is sloped at front. I did it in hopes of reducing drag, nothing to do with tongue weight. I can't imagine that a flat trailer would cause the tongue to lift enough to be a problem.

 

A nice benefit of the sloped front is I don't have to get on my hands and knees to look in there.

 

I don't know whether that slope is an advantage for towing or not. What I do know is that even fully loaded it's easy to forget it is back there.

[MiCarl]

I got a question about the dome and the pipe in the picture.

 

They are ventilation for the dog. Dome is solar vent, pipe is ram air which is capped when stored to keep dirt and critters out.

[XV1100SE]

One advantage of the sloped front is sound from the exhausts. Sound deflects by the shape.

 

If it is a straight up front the sound deflects back to the bike.

[Brake Pad]

this is my trailer,,not home made, but it was bought, for the reason of wind deflection

[dacheedah]

I have a tag along, very lite, and have pulled it almost empty at 80mph, never lifted it at all. It's not a wing and I don't think we get enough speed to get lift.

[CaptainJoe]

Take off speed for a Cessna 150 is 65...

 

But you are right, most trailers aren't shaped like a wing.

 

The thing I'd be more concerned about is cross wind (from the side).

 

 

The best looking trailer I've seen todate was at Dons MD 2 or 3 years ago. It was tear dropped shaped. Believe it was custom made so aerodynamic is the way to go... Better fuel economy, less drag. IMHO

Edited May 21, 2013 by CaptainJoe

[jfoster]

Take off speed for a Cessna 150 is 65...

 

But you are right, most trailers aren't shaped like a wing.

 

The thing I'd be more concerned about is cross wind (from the side).

 

 

The best looking trailer I've seen todate was at Dons MD 2 or 3 years ago. It was tear dropped shaped. Believe it was custom made so aerodynamic is the way to go... Better fuel economy, less drag. IMHO

 

That's what I've always heard about van style semi trailers is the square back creates a lot of drag. There's one carrier that runs blue trucks out El Paso that has flaps installed to decrease the drag.

[meach]

Had a case a day or two ago of a semi passing a HD pulling a trailer on I75 nearby, wind against the trailer caused the driver to lose control according to police report causing bike to roll killing the driver. No idea what type of trailer or its shape.

 

http://www.ajc.com/news/news/local/paulding-funeral-director-killed-in-freak-motorcyc/nX2rh/

 

My recent HF trailer doesn't seemed affected by passing trucks, etc. I have driven at different speeds while on interstate (recently took 800 mi trip w/ trailer) fastest being about 85 under differing conditions to see how trailer responds. The only time I was a little nervous was driving in a constant rain where I kept the speeds much lower. Was worried about slick spots on road, etc.

 

Meach

[Chicago]

When I attached my Sears X-Cargo car top carrier to me Harbor freight trailer kit, I put the pointy end to the front (like it would be on top of a car) and it pulls like a dream. Oh yeah, and I've only got a little over $200 in it.

[djh3]

I had a home built trailer years ago we pulled behind or Suzuki GS1000. It was only about maybe 2.5' wide x 3' or so tall (box) and maybe 4' long. Being that narrow I never really felt any wind issues. I like the sloped end forward ideas for all the reasons mentioned. If you turn them around I guess you could induce lift at the hitch. Which wouldnt be good.

[Guest tx2sturgis]

Had a case a day or two ago of a semi passing a HD pulling a trailer on I75 nearby, wind against the trailer caused the driver to lose control according to police report causing bike to roll killing the driver. No idea what type of trailer or its shape.

 

 

 

Meach

 

I think there is more to this story.....I suspect the trailer/bike combo was unstable for some reason, (maybe tongue weight was too low or low air pressure on the bikes rear tire...or loose neck bearings?) and the wind blast from the semi upset it to the point of a high speed wobble of the worst kind.

 

I guess we will never know.....

 

 

 

[Condor]

Here's my thinking on the trailer shape.... I may be wrong?? But... air flow over the top of an airplane wing creates lift by a low pressure area above the wing. When air flow is increased over the top of a trailer by a sloped front toward the bike it will form a low pressure and lift the trailer. A trailer front sloped back away from the bike...from the top toward the rear.. should create a low pressure beneath the trailer and keep it more stable...?? How much effect does this have on a trailer?? Probably not much... IMHO...

[Prairiehammer]

Here's my thinking on the trailer shape.... I may be wrong?? But... air flow over the top of an airplane wing creates lift by a low pressure area above the wing. When air flow is increased over the top of a trailer by a sloped front toward the bike it will form a low pressure and lift the trailer. A trailer front sloped back away from the bike...from the top toward the rear.. should create a low pressure beneath the trailer and keep it more stable...?? How much effect does this have on a trailer?? Probably not much... IMHO...

 

In theory, an aerodynamic trailer with an air foil like profile might act like airplane wing in a wind tunnel and cause a lifting of the trailer, however all the trailers out there, whether aerodynamic or not are following a motorcycle. A touring motorcycle is a very un-aerodynamic vehicle. There is a huge amount of disturbed and chaotic air flow in the space behind a motorcycle where the trailer is. I don't think that the air foil shape would have any laminar flow to cause lift when being towed. In fact, the turbulence behind a motorcycle may actually push DOWN on a trailer rather than cause a lifting. IMHO

Edited May 27, 2013 by Prairiehammer

[Brake Pad]

we were on our way up 65, during a heavy rainstorm, our trailer was being pushed around as Big Rigs, came passed us. I kept moving closer to the shoulder as they came up on me.

[BEER30]

The BEERCART is somewhat boxed shape and has slight slope in front top and side. Some flare around wheel wells and a wing spoiler on rear. Empty weight is 190 lbs., however had fully burdened down with 550 lbs..

I find it more assuring when riding in the rain. The BEERCART causes enough drag to keep me straight going through standing water in lane grooves. I somewhat think it helps with hydroplaneing. There has been more times that I have passed slowed down cagers in the rain. Onetime while coming back from MD, we rode too close to a tornado that just passed. 60 MPH crosswinds, rain , hail and heavy traffic to which NO one was giving us a break. There were no where to pull over as there were no shoulders. As I was more concerned and concentrating on keeping 2 wheels on the road, wife later said we were leaning into the wind very hard and was suprised we managed as good as we did. Honestly, I was not sceered at all....maybe I'm too crazy to say the least.

Another time, Muffinman and I were both 1 up pulling our trailers. His was a Harbor Freight with box on it. Just to see how they pull, we pegged the speedo's to the max. Needless to say, we never even noticed that the trailers were behind us.

Bottom line is, I think regardless on how your trailer is shaped, it's more on how you pack your cargo and tongue weight. Tongue length is also a factor. I later had to lengthen the BEERCART's tongue about 10" to reduce the tail wagging. Shorter tongue = more sway, longer tongue = less sway.

 

BEER30

[Guest tx2sturgis]

In theory, an aerodynamic trailer with an air foil like profile might act like airplane wing in a wind tunnel and cause a lifting of the trailer, however all the trailers out there, whether aerodynamic or not are following a motorcycle. A touring motorcycle is a very un-aerodynamic vehicle. There is a huge amount of disturbed and chaotic air flow in the space behind a motorcycle where the trailer is. I don't think that the air foil shape would have any laminar flow to cause lift when being towed. In fact, the turbulence behind a motorcycle may actually push DOWN on a trailer rather than cause a lifting. IMHO

 

Yeah that!

 

 

And dont forget the very disturbed airflow under the bike and trailer...almost nothing there to 'push' (lift) up on the trailer...lifting pressure is always created UNDER the object, whether its a wing, or a trailer, or a nascar racer. With the front airdam keeping air out from under the chassis, there is almost zero lift on a race car, not matter what the shape, and they have plenty of 'downforce'...unless the front end gets mechanically damaged or bumped up, it stays planted.

 

 

[farm1810]

Your responses have been great, thank you. I wasn't thinking of lift i.e. the trailer starts to lift off of the ground, I was thinking about tongue forces. So a single axle trailer with a flat front surface, would this at highway speed - 75 mph - cause a lifting force on the tongue? That was my real question. I would assume with proper tongue weight this would be a non-issue. I recently read that a larger surface on the area facing the bike would / could cause exhaust to be drawn up into the rider / passenger area much like leaving the rear window down on an old station wagon. It's all interesting. I'll post a pick of the little trailer I am building once it is complete.