Aerodynamic trailer plans

[jimbo69ny]

Hello,

I am planning on building a lightweight aerodynamic teardrop to pull behind my all electric Toyota Rav4 EV.

I dont know how to use CAD (nor do I have the software) so I did the best I can sketching this out on paper. Please let me know what do you think.

Do you see any issues with the design that will become troublesome in construction?
What do you think of the idea?
Anything I should add?

I am not sure how the rear should hinge. I am thinking that the rear most section, after 8', could hinge up or to the side. I am open to suggestions.

Thanks!

UPDATE: Version 2....

 

[jimbo69ny]

My motivation for the rear of my teardrop is the rear of semi trucks with the wind deflector. Its better for aero. Here are examples.
https://www.google.com/search?q=tra...24neAhXrT98KHRHmCesQ_AUIDygC&biw=1238&bih=681

I wanted to round the roof a bit to also help aero.

Lastly, I wanted the front of the teardrop to be flat so my wife and I can lean up against it when we are park if we want to sit and read a book or play with our baby. 36" is perfect. That leaves the overall height within my slipstream from my Rav4 too.

 

[Pmullen503]

I would make the whole Kam tail swing out sideways. Unless there is enough height at the roof junction to make a useable galley with the hatch up.

 

[jimbo69ny]

Is there a good place to buy the parts to make it swing sideways? Just starting out so forgive me if there is some awesome trailer parts website that I dont know about.

Has anyone else done a side swinging rear door?

 

[troubleScottie]

There are several threads in here on this topic. I have not seen anyone suggest or build the rear deflector -- even on a square back design.


The teardrop profile is possibly the optimal shape as it presents good flow over the trailer. A brick shape is the worst. Wedges somewhere in between.

For any object, the biggest issue is the projected cross sectional area. Ideally the towing vehicle (TV) cross section is equal to or greater than the trailer. Due to the space between the TV and the trailer, the trailer often behaves like a separate object. Your trailers height might be less than the TV which is good, depends on your wheel size, axle placement, etc

Your upright front face may be the least than optimal. If you want a panel to rest against, you might consider a bulkhead inside the trailer. Of course given the 8' length, this might be impractical.

Also, the wheels are sources of drag. They might stick out relative to the TV, and present drag

BTW, 36 inch is pretty short. Given a mattress (2-6") and ceiling (1-3"), the usable height is cramped. Think about sitting under your desk. You might consider a taller design. A whole plywood sheet on top of the trailer bed will give you an additional 12 inches.


The other thing is to consider the materials that you are constructing this out of. Foam is the lightest. Plywood, etc can get quite heavy.

 

[jimbo69ny]

Thank you for your post!

I forgot to consider the thickness of the mattress when considering the height! Thank you!

I do plan on having the overall height and width slightly smaller than the Rav4.

Do you think I should curve the roof like I have in the plan? It really would be so much easier NOT to but I want to make it right. From what I have read and seen it is better to have the top/edges rounded off.

I googled it and the edges are a source of 6% of the overall wind resistance of a trailer.

 

[Pmullen503]

The compound curved roof will shed water better and be stiffer than a simple curved roof. So theoretically you can build it lighter. You have to ask yourself if it's worth the time and effort to get small increases in efficiency. My trailer costs about 10% on my gas mileage at 70mph. It's a cargo hauler with a big flat back end. Not very aerodynamic. But it's hard to justify building a better trailer when it only costs an extra penny or two per mile to bring it along.

Functional features should be your priority, then making that as aerodynamic as practical.

 

[jimbo69ny]

The compound curved roof will shed water better and be stiffer than a simple curved roof. So theoretically you can build it lighter. You have to ask yourself if it's worth the time and effort to get small increases in efficiency. My trailer costs about 10% on my gas mileage at 70mph. It's a cargo hauler with a big flat back end. Not very aerodynamic. But it's hard to justify building a better trailer when it only costs an extra penny or two per mile to bring it along.

Functional features should be your priority, then making that as aerodynamic as practical.

I drive and will be towing with an electric vehicle. So to us it is very important to increase efficiency. You can refill in 5 minutes at any gas station. It would take me 45 ish minutes at a fast charger (which are still kinda rare).

So thats why I need to make it as efficient as possible.

 

[Tony Latham]

Camp-Inn says that their Raindrop model gets better mileage than their traditional teardrop-shaped model. You might PM those on this forum that have built raindrop shaped campers.

I noticed a difference when I went from a 4-wide teardrop to a 5-wide. Some of that was probably weight. (But I won't be going back to a 4'-wide.)



Tony

 

[swoody126]

your drawings are not at all unlike the CLC teardrop

https://www.clcboats.com

here is a link to videos of it

https://www.bing.com/videos/search?q=cl ... &FORM=VDRE

like the concept waiting to see how you proceed

sw

 

[DaddyJeep]

I have read this article a couple times during my designing. There are some interesting facts in here. It appears that the leading edge of your trailer is far more important that the trailing edge.

https://www.nasa.gov/centers/armstrong/ ... -DFRC.html

 

[Pmullen503]

I drive and will be towing with an electric vehicle. So to us it is very important to increase efficiency. You can refill in 5 minutes at any gas station. It would take me 45 ish minutes at a fast charger (which are still kinda rare).

So thats why I need to make it as efficient as possible.

In that case, I'd think about rounding the leading edges of the trailer, keeping the underside smooth, and reducing the aero drag of the wheels if they'll be outside the body.

In my own case, I know just by watching rain through my back window (and the dirt patterns on the trailer itself when I tow through rain) that the airflow between the trailer and TV is chaotic. That has to be a major contributor to the total drag. So cleaning up that in any way will help.

 

[jimbo69ny]

I have read this article a couple times during my designing. There are some interesting facts in here. It appears that the leading edge of your trailer is far more important that the trailing edge.

https://www.nasa.gov/centers/armstrong/ ... -DFRC.html

I will definitely read this article. However before doing so I have to say that the leading edge would be the front of the car. If I can minimize the gap between the rear of the car and the front of the trailer, the front of the teardrop isnt as important.

There was another thread here on this site that showed the different aero turbulence points but here is a link that also shows it.

https://www.teamrunsmart.com/articl...13/aerodynamics-101-streamlining-your-trailer

 

[jimbo69ny]

your drawings are not at all unlike the CLC teardrop

https://www.clcboats.com

here is a link to videos of it

https://www.bing.com/videos/search?q=cl ... &FORM=VDRE

like the concept waiting to see how you proceed

sw

I do really like that teardrop but I want something larger. Also, it seems like a lot of work putting that kit together. I have read about fitment issues with the door too.

 

[jimbo69ny]

Camp-Inn says that their Raindrop model gets better mileage than their traditional teardrop-shaped model. You might PM those on this forum that have built raindrop shaped campers.

I noticed a difference when I went from a 4-wide teardrop to a 5-wide. Some of that was probably weight. (But I won't be going back to a 4'-wide.)



Tony

Thank you but that thing is too heavy. I just checked out their site. Its over 1000lbs! I am looking to build one around 400-600lbs.

I think my body design is good but I am keeping an open mind. So if anyone can prove differently I am leaning towards my design.

 

[Tony Latham]

Camp-Inn says that their Raindrop model gets better mileage than their traditional teardrop-shaped model. You might PM those on this forum that have built raindrop shaped campers.

I noticed a difference when I went from a 4-wide teardrop to a 5-wide. Some of that was probably weight. (But I won't be going back to a 4'-wide.)



Tony

Thank you but that thing is too heavy. I just checked out their site. Its over 1000lbs! I am looking to build one around 400-600lbs.

I think my body design is good but I am keeping an open mind. So if anyone can prove differently I am leaning towards my design.

I wasn’t suggesting you buy their Raindrop. I was suggesting you should consider building yours with that front shape in the interest of aerodynamics.

Whether you build a traditional shaped ‘drop or mimic the Raindrop’s profile the weight should be sixes. My 5x20s come in at about 1250 pounds so that weight isn’t surprising.

T

 

[jimbo69ny]

Camp-Inn says that their Raindrop model gets better mileage than their traditional teardrop-shaped model. You might PM those on this forum that have built raindrop shaped campers.

I noticed a difference when I went from a 4-wide teardrop to a 5-wide. Some of that was probably weight. (But I won't be going back to a 4'-wide.)



Tony

Thank you but that thing is too heavy. I just checked out their site. Its over 1000lbs! I am looking to build one around 400-600lbs.

I think my body design is good but I am keeping an open mind. So if anyone can prove differently I am leaning towards my design.

I wasn’t suggesting you buy their Raindrop. I was suggesting you should consider building yours with that front shape in the interest of aerodynamics.

Whether you build a traditional shaped ‘drop or mimic the Raindrop’s profile the weight should be sixes. My 5x20s come in at about 1250 pounds so that weight isn’t surprising.

T

Oh my bad. I misunderstood.

I am so eager to start this. Unfortunately winter is right around the corner, I live in Central NY, and resin doesnt like cold temps.

 

[jimbo69ny]

Is there any chance someone would be willing to use CAD to make this for me?

 

[OP827]

Sketchup is not difficult to learn and previous versions are free. I have learned how to use it in a matter of few hours by coming across this site and watching videos, very good tutorials and a link to download the software.
https://jayscustomcreations.com/sketchup/

I am also building a larger lifting roof foamie with epoxy fiberglass surface, now close to finishing. I did a small overhang in the back of my trailer to help with aerodynamics and structure. When in transport mode the roof is same height as TV. Good luck with your build. Hope the above info helps.
OP

 

[jimbo69ny]

Sketchup is not difficult to learn and previous versions are free. I have learned how to use it in a matter of few hours by coming across this site and watching videos, very good tutorials and a link to download the software.
https://jayscustomcreations.com/sketchup/

I am also building a larger lifting roof foamie with epoxy fiberglass surface, now close to finishing. I did a small overhang in the back of my trailer to help with aerodynamics and structure. When in transport mode the roof is same height as TV. Good luck with your build. Hope the above info helps.
OP

Do you have any videos or photos of your build?!?! Sounds right up my alley!