When I was doing some research for another thread, I found out something about the new SAE J2807 towing standards that seems like it has ramifications for owners of small egg trailers.
It appears the trailers used to test tow ratings under the new standards are cargo trailers, and the frontal area may be much smaller than the typical egg trailer of the same weight
. For example, in the 1000-2000 pound class, which is where may 13'ers fall
, the J2807 standards specify a minimum frontal area of only 20 sq. ft., defined as the entire front of the trailer down to the ground plane. Using that definition, I'd estimate the frontal area of a Scamp
13 at about 45 sq. ft. In the 2000-3500 pound class, encompassing many 16-17' trailers, the standards specify a minimum frontal area of only 30 sq. ft.
Here in an excerpt and a link to my source:
SAE J2807 Towing Standards
Frontal area makes a significant difference at highway speeds. Air resistance increases as the square of speed. A 1600 pound Scamp
with a frontal area of 45 sq. ft. is going to put a lot of additional demand on the tow vehicle's drivetrain compared to a 1600 pound, low-profile cargo trailer with a frontal area of 20 sq. ft. (even factoring in the Scamp's rounded profile).
The takeaways for me:
- The new towing standards don't really fit the realities of molded fiberglass eggs too well. The ratings assume dense, compact loads. Our eggs are mostly air!
- It is prudent to allow a significant margin in the tow rating when selecting a tow vehicle for an egg-type trailer due to the additional demand of the higher-than-tested frontal area.
- Manufacturers of tow vehicles and trailers need to provide more information to consumers. Few owner's manuals I have looked at give any guidance as to how tow ratings are affected by frontal area.
I was keenly aware of how much wind resistance a lightweight trailer can generate on our trip to CA this summer. Climbing a moderate (5-6% or so) grade west of Palm Springs against a stiff headwind (estimated at 35 mph sustained with higher gusts), we were reduced to 35-40 mph in 2nd gear. Our Scamp
only weighs about half the 3500# rating of our tow vehicle, but it felt like we were dragging an anchor.