Aerodynamic improvements.

[Hersbird]

I have started on a few modifications I hope will improve aerodynamics as well as add some useful dry storage on the back.

First my 1993 Tow lite is a foot wider then the tow vehicle, a 2008 Chrysler Aspen. So I put some 9" galvanized ductwork split down the middle and opened up to a 12" 1/2 round cylinder along the outside edge to help smooth and attach the air coming off the Aspen.

Then I added some styrofoam 12" 1/4 spheres to the top I plan on covering in fiberglass.

I also plan on adding a nosecone and tapered tail to the side awning, skin the belly with coroplast sheets, and then build a 20" long slightly tapered tail on the back that will aslo double as a dry, lockable storage.

 

[Luckydog671]

Interesting - when complete you can take it to the Lucas wind tunnel at Caltech for testing!

John W. Lucas Wind Tunnel - Graduate Aerospace Laboratories at the California Institute of Technology

 

[gus-HILO]

Interesting, just make sure the fiberglass top is secured well. I suppose those of us that have the Hi-Lo classic has the front and rear end already rounded for aerodynamics.

 

[Hersbird]

It was $25 worth of materials. I figure the way all that air off the side of the TV hits that edge it would be worth a try. I really noticed the spray on the freeway in the rain getting kicked way out away from the side with it stock. That is as close to a wind tunnel I will get! I've been getting a bunch of advice from the aerodynamics forum at ecomodder.com. They seem to think these should "trick" the air into thinking the front of this had 6" radius corners which is a big improvement over sharp corners. They also say just as much drag comes from the back as the front, why those trailer tails on semis really work.

 

[hilltool]

A cool feature would have been to make the globes at the top translucent and wired in lights. You would have the best ornamental lights in any campground.

 

[Hersbird]

A cool feature would have been to make the globes at the top translucent and wired in lights. You would have the best ornamental lights in any campground.

Actually I could, after making the fiberglass cover you can remove the styrofoam under and the glass could be translucent. That is actually a cool idea even just for the sidemarker lights I covered up and was thinking of where to move them to.

 

[Hersbird]

Here is the boattail storage box so far

What I'm thinking for the profile of the top which will be a frame of 1/2" conduit covered in 1" foam then covered in epoxy.

This shows how I left room to tow a 2nd small trailer, my Jetski, and the new LED lights. I will cover the wood in Titebond II and fabric then paint.

Here are the cones I made for the awning, they need epoxy and paint.

Here is the whole side shot.

 

[Fountain-FRF]

Not to sound too negative, but have you put a pencil to the added benefit you may get with these mod's? I can only assume you were shocked at the mileage your Aspen logged in when you were towing?

 

[Hersbird]

The front and awning mods cost less then $30 and is kind of like a hobby. The rear mods are mainly to add storage but figured might as well be made to improve aerodynamics as well. A trailer that was designed with aerodynamics in mind from the start should be able to not only not add to overall drag but actually improve it. Meaning steady state, level highway MPG would actually improve while towing the trailer then without it. I am not going to achieve that but even adding 1 MPG would be a success. Actually I was kind of bummed at the 14-15 I was getting stock, I think the biggest factory flaw was making it wider then the tow vehicle.

 

[Luckydog671]

Howdy Hersbird,

Not sure how much weight the rear storage box will ultimately hold, but when complete, I would be interested in hearing if there are any negative effects on stability or tongue weight from the extra weight.

 

[Hersbird]

The box itself weighs about 100# and I plan on putting maybe 100# worth of stuff in there. If I tow the jet ski with it's 100# of tounge weight I'll leave it empty. I put 75# in there yesterday and then I climbed in it and jumped up and down and it seemed quite solid. I weigh 225#. I need to weigh the tounge but with the box and 75# in it I still can't budge the tounge which means it's still over 300#, I would guess we'll over 400#. I will get the whole thing weighed when loaded for camping and make sure it's 10-15% on the tounge. I think Hi-lo went a little heavy on the tounge from the factory.

 

[hilltool]

Everything is worth a try. They are your toys- you should be allowed to play with them as you see fit. That said, most folks towing travel trailers of that length and weight would be generally pleased getting 14-15 mpg. Unless, of course, they were using an older Ford diesel as tow vehicle. Good luck. It all looks like great fun. Keep us posted.

 

[Hersbird]

So I've gotten some more done. I made a top awning out of 1/2" conduit covered in 1" rigid foam. It covers the bottom box and makes an awning when raised.

 

[JackandJanet]

That's pretty neat!

- Jack

 

[Hersbird]

I would really like to make a slide out BBQ into where the clothes closet is in the back bathroom. It would store in there and slide out the side when popped up. Then the back box could be a buffet or food prep area near the BBQ. I'd also like an outside sink as well. Somebody already suggested a keg and a tap back there, and I did make in maroon and silver the local college football colors...

 

[Hersbird]

We are back from our trip. We were fully loaded with water and gear for 3 adults and 3 kids for a week without many services, probably over 4000# in the trailer and 800# in the SUV. When all said and done NOT counting a 360 mile tank not towing touring Yellowstone, we did 1301.8 miles and used 92.53 gallons for 14.07 mpg average. That is including a 10,900 climb and many other smaller passes where you could no way coast down without lots of engine and traditional braking. Mostly around 60 mph with some sections slower or faster, nothing over 65. The non-towing tank for comparison was 17.3 MPG and the max speed possible in Yellowstone is about 50 mph but mostly 40 with lots of stopping for wildlife.
The best tank was the last with a 275.2 miles at 15.1 MPG losing 3200 feet but also having a large pass in the middle that needed braking on the way down. The indicated on that tank was also 15.1 and before the pass and the 65 mph interstate run it was indicating 16.5 mpg!
Overall I'm happy, I want to still try a belly pan and upgrade my hitch to a WD anti sway. I'd love to see how well it might do towing it with something that has better economy. The 5.7 Hemi isn't exactly known for getting good mileage.

 

[Herb-in-FL]

More sleek with less drag.

It is really cool to see your interest in making your Hi Lo more aerodynamic,
and drag on the tail section is one of the biggest factors to consider.
Have you looked up any of the research done by a German engineer
on the Kammback, also known as the Kam Tail.
https://en.wikipedia.org/wiki/Kammback

And for ideal proportions they considered as an ideal compromise.

"the tail should be cut off where it has tapered
to approximately 50% of the car's maximum cross section
( or in this case: trailer )"

Food for thought and design, maybe?

GoCamp

 

[Hersbird]

Thanks, I got the basic shape from the aerodynamic forum at ecomodder.com we just finished another trip to Yellowstone and back and averaged 14.5 MPG towing and had a blown wheel bearing at some point in the last 120 miles. That was with 4 adults, a child, and all that gear. My average not towing 50-50 city and Highway is only 15.5 mpg but I have gotten as high as 18 mpg not towing. These numbers are all hand calculated based on full fill up.

I had originally wanted a teardrop shape but was clued in on ecomodder that almost every teardrop camper shape has way to much angle on the back actually hurting aerodynamics compared to the Kamm. I was looking mainly at those R-pods and if you look in their forums you see they really don't get better mpg then a less expensive common box trailer of the same size. The steep drop-off on the back has the same effect as a parachute.

 

[Hersbird]

Update, we did another trip to Yellowstone and month ago and back and averaged 14.45 mpg blowing a wheel bearing on the way back at some point in the last 100 miles.

Then last week we took it hunting and averaged 14.5 MPG there and a whopping 16.8 mpg on the way home, we replaced the wheel bearing that failed along with the ones on the wheel on the same side. I have the parts to finish the other side so will get that done before spring. Averaging 15.65 mpg for that trip makes me pretty happy.