Aerodynamic trailer plans

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Re: Aerodynamic trailer plans

Postby tony.latham » Tue Oct 16, 2018 3:08 pm

jimbo69ny wrote:
tony.latham wrote: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.)

:thinking:

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
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Re: Aerodynamic trailer plans

Postby jimbo69ny » Tue Oct 16, 2018 3:10 pm

tony.latham wrote:
jimbo69ny wrote:
tony.latham wrote: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.)

:thinking:

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. :(
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Re: Aerodynamic trailer plans

Postby jimbo69ny » Tue Oct 16, 2018 3:11 pm

Is there any chance someone would be willing to use CAD to make this for me?
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Re: Aerodynamic trailer plans

Postby OP827 » Tue Oct 16, 2018 7:07 pm

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.
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Re: Aerodynamic trailer plans

Postby jimbo69ny » Tue Oct 16, 2018 7:15 pm

OP827 wrote: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!
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Re: Aerodynamic trailer plans

Postby OP827 » Tue Oct 16, 2018 7:16 pm

jimbo69ny wrote:
OP827 wrote: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!
Yes, click the link in my signature below


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My foldable foam trailer build: http://www.tnttt.com/viewtopic.php?f=50&t=61344
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Re: Aerodynamic trailer plans

Postby jimbo69ny » Tue Oct 16, 2018 7:29 pm

OP827 wrote:
jimbo69ny wrote:
OP827 wrote: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!
Yes, click the link in my signature below


Sent from my Moto G Play using Tapatalk


Well there goes my night, that is a lot of content to review. I also found your photos on your profile. Gotta go guys, lots of reading to do. haha!
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Re: Aerodynamic trailer plans

Postby timm » Sun Oct 28, 2018 5:43 pm

You may find my wind tunnel (CFD) simulations interesting. I've done a couple different situations with my car (2010 Honda Civic Coupe) towing various shapes of trailers.

Just Car
Drag = 270 N
Image

With 5x8 Enclosed Trailer
Drag = 820 N (3x Car Drag)
Image

With Normal Teardrop Trailer
Drag = 710 N (2.6x Car Drag)
Image

So according to my math, my car would go from about 38 MPG to about 17 MPG pulling a normal teardrop, and it would drop to about 15 MPG pulling the 5x8 enclosed trailer.
I'm not sure exactly what decrease in range you would see pulling the shape you've proposed but I'm guessing it would be a pretty significant decrease. Probably not half like I would see with my car though.

There are a bunch of things you can do to make a design more aerodynamic.
- Reduce the gap between the vehicle and trailer
- And wheel fairings in front of and behind the wheels (Google wheel pants)
- Add a boat tail
- Lower the roof of the trailer
- Round all exterior corners

Here's a sneak peak of the trailer design I'm working on right now, so far it's much more aerodynamic than the normal teardrop shape while maintaining about the same amount of internal room.

Image

The air splitter on the front takes care of the turbulent air between the car and the trailer. I still need to add wheel fairings but other than that this is a pretty aerodynamic trailer.
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Re: Aerodynamic trailer plans

Postby jimbo69ny » Sun Oct 28, 2018 5:51 pm

Wow I love your work! Great job! That is a really sweet program you're using.

Since posting here I have a totally new design in my mind. I dont have an awesome program like yours (or the skills to input the data) so i am using graph paper. Ill work on it tonight and post it asap.
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Re: Aerodynamic trailer plans

Postby jimbo69ny » Mon Oct 29, 2018 7:39 am

Here is what I am thinking for my build. It would fit directly in the slipstream of my Rav4.

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Re: Aerodynamic trailer plans

Postby Tigris99 » Mon Oct 29, 2018 7:28 pm

timm wrote:You may find my wind tunnel (CFD) simulations interesting. I've done a couple different situations with my car (2010 Honda Civic Coupe) towing various shapes of trailers.

Just Car
Drag = 270 N
Image

With 5x8 Enclosed Trailer
Drag = 820 N (3x Car Drag)
Image

With Normal Teardrop Trailer
Drag = 710 N (2.6x Car Drag)
Image

So according to my math, my car would go from about 38 MPG to about 17 MPG pulling a normal teardrop, and it would drop to about 15 MPG pulling the 5x8 enclosed trailer.
I'm not sure exactly what decrease in range you would see pulling the shape you've proposed but I'm guessing it would be a pretty significant decrease. Probably not half like I would see with my car though.

There are a bunch of things you can do to make a design more aerodynamic.
- Reduce the gap between the vehicle and trailer
- And wheel fairings in front of and behind the wheels (Google wheel pants)
- Add a boat tail
- Lower the roof of the trailer
- Round all exterior corners

Here's a sneak peak of the trailer design I'm working on right now, so far it's much more aerodynamic than the normal teardrop shape while maintaining about the same amount of internal room.

Image

The air splitter on the front takes care of the turbulent air between the car and the trailer. I still need to add wheel fairings but other than that this is a pretty aerodynamic trailer.
your calculations are way off for MPG losses.

Aerodynamic drag is a function of speed as well. And for MPG the loss is a variable of the speed. But that's only a portion of determined MPG. The weight of the vehicle, load weight, trailer weight etc all effect that.

My CRV only lost about 15% at 55mph towing something 1500lbs , some front angles and square back. Your not going to loose half your fuel mileage because of a large increase in aerodynamic resistance.

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Re: Aerodynamic trailer plans

Postby timm » Mon Oct 29, 2018 8:43 pm

You are correct that fuel mileage is dependant on multiple things, however, my calculations have taken pretty much everything into account. Of course, I can't say for sure that my math is perfect without building the trailer and doing testing.

I calculated the mileage losses at 62 mph, which means your 15% decrease in mileage would probably be closer to 20%. You also have to consider that a CRV has a larger engine than a Civic so it will tow a trailer easier. Considering aerodynamic drag and rolling resistance are basically the 2 major things contributing to fuel mileage it doesn't seem crazy that tripling the aerodynamic drag and multiplying rolling resistance by 1.5 would reduce mileage by half.
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Re: Aerodynamic trailer plans

Postby DaddyJeep » Tue Oct 30, 2018 11:54 am

jimbo69ny wrote:
DaddyJeep wrote: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/articles/truck-smart/maintenance/july-2013/aerodynamics-101-streamlining-your-trailer


What I was trying to point out is that you are not going to make significant improvements because the TV is what is "cutting" the air. The nasa testing as well as the information on that trucking site supports that. The one guy did all kinds of stuff... side skirts, wheel covers, under trailer smoothing, relocating his license plate, improved mudflaps and he gained 1mpg. That might be a lot if you are driving hundreds of thousands of miles, but for a weekend camping trip it isn't going to be substantial savings. My design is very complicated for the same reasons you are striving for and I realize there will be little gain from my extra work. I spent a lot of time researching aerodynamics for my camper project as well as my son's van project in an effort to gain a few mpg's. I read a bunch of stuff on ecomodder.com and other places and realized there will be very little benefit from complicating things. I also had a couple classes in aerodynamics when I was in college for automotive design. All this said, I am all for working a little harder to make something unique. Build what makes you happy. :thumbsup:
My big hybrid toy hauler with lots of curves build viewtopic.php?f=50&t=69618

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Re: Aerodynamic trailer plans

Postby Tigris99 » Tue Oct 30, 2018 4:08 pm

timm wrote:You are correct that fuel mileage is dependant on multiple things, however, my calculations have taken pretty much everything into account. Of course, I can't say for sure that my math is perfect without building the trailer and doing testing.

I calculated the mileage losses at 62 mph, which means your 15% decrease in mileage would probably be closer to 20%. You also have to consider that a CRV has a larger engine than a Civic so it will tow a trailer easier. Considering aerodynamic drag and rolling resistance are basically the 2 major things contributing to fuel mileage it doesn't seem crazy that tripling the aerodynamic drag and multiplying rolling resistance by 1.5 would reduce mileage by half.
yes it has a slightly larger 4cyl but is 4wd and a much larger profile.

Your images show that you actually tested on not actual teardrop (partially flat front) which is a problem for cars. You percentages seem more in line than the way I read the first post of about 50% loss in fuel mileage.

I know a guy who towed one that was production squaredrop (horrible profile) with a Suburu and his losses werent as bad as one would expect combined with 1500lbs of trailer.

Now my old trailer fully load plus stuff in the back and full family in our odyssey the faster we went the better the mileage. 55-60mph loss wasnt bad, got better mpg at 70mph. 4000lb minivan with 2 adults, 2 kids, cooler and gear plus 1500lb trailer. My wifes van is way over powered along with 8speed tranmission for a minivan. Trailer was built flat back but to stay in the draft of the van as much as possible.

Biggest concern with cars is and flat nose space. Getting all crazy is cool (love the lines I'm seeing of going full aerodynamic around here) but weight and eliminating square surfaces front and rear seems to make a huge difference.

Try simply wedging the nose so leading edges stay in cars draft and see how much of a difference that makes compared to benroy/canned ham styles. Or even true teardrop.

Keep in mind that a with a civic weight is going to play as much of a role as aerodynamic drag because unless you live where it's perfectly flat hills are going to be a big issue, even a small grade is going to make it strain alot if you try to push is max rating. and that rating INCLUDES all weight in the vehicle minus the driver and tank of fuel.

Just thoughts of keeping it simple and cost effective versus trying to make a bullet on wheels. But that of course depends on your time and funds.

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Re: Aerodynamic trailer plans

Postby jimbo69ny » Tue Oct 30, 2018 4:19 pm

Hey guys I dont want to be a dick but if you want to debate his figures please do it privately or in a new thread.

I am really hoping for real, factual, advice on my build.

Thanks!
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