What's more important?

[Reace]

What's more important......aerodynamics or interior storage space?

We are thinking of angling the front wall of the trailer to help reduce the 'drag' effect but in doing so....we lose cabinet space.

hmmmm........

Reace

[Bobbie Mayer]

I'm not buying one anytime soon, but drag would be more important to me, with gas prices what they are. The TV has plenty of storage if needed.

Bobbie

[Glenn Baglo]

Short of building one with the angled wall and testing it in a wind tunnel, you have no way of quantifying the mileage you would gain. So, you lose that as a marketing tool. All you can do is claim it's more aerodynamic, whether it is or not.

But, the cupboards. Well, they are either there or they're not. You don't say how much cupboard space would be lost, but I'm using every inch of the cupboard space at the front of my 17' Escape ( space under the seats is more or less empty, however ).

So, my vote is to keep the cupboards. When you're set up at camp, those cupboards are important and aerodynamics is having no effect at all.

baglo

[Rob M]

Gas mileage is important to us, so the more aerodynamic you can make it the better it is. The only concern we have is how will it affect the gaucho bed option?
Rob

[Daniel V.]

One of the reasons we got our Trillium is that it did not have any angled walls. Some of the non-FG trailers that we visited before had them over the dinette and required people to sit at an angle and/or bump their head on it.

I'm no scientist, but it seems to me that improving the aerodynamics would be the most helpful in cases when you're pulling with a vehicle that is significantly lower than the trailer, such as a passenger car. And hardly any of those cars have a high enough tow rating to be pulling even the smallest trailer (up to 1800# loaded) in the first place, and many people end up getting a bigger car or small truck because of that. I would rather install some sort of fairing or wind deflector on top of the tow vehicle than lose any of the storage space or sit at an angle.

[Donna D.]

What's more important......aerodynamics or interior storage space?

Reace THANKS for asking! It's refreshing that a manufacturer asks what the consumer wants.

My 2-1/2 cents... FWIW. I vote aerodynamics. We don't know what's going to happen with fuel prices, other than the fact they won't go down to pre-2000 levels. The economics of camping is going to continue to climb and may very well prevent owners from camping in areas other than very near. I'd love to have MORE overhead cabinets, but not at the expense of not being able to afford to camp anywhere except my driveway. Even if the possible change only brings about 1 extra mile per gallon, that will add up over the lifetime of the trailer ownership. Of course in my case, it doesn't matter... because I'm going to have an Escape 5th wheel and the front is already built with a front-angled nose.

[Ken C]

My vote is aerodynamics.

[Cam A]

I'd say it depends. How much of a break in mileage would an angled front create? Perhaps folks that can afford a new trailer aren't that concerned about an extra bit of mileage. If I could buy an Escape, I'd vote for the storage space. And to echo Donna, thanks for asking.

[Mark Hayes]

Hi Reace,

We would much prefer better aerodynamics at the cost of some storage space. Using less fuel, even a little, is important to us. The Escape has quite a bit of storage as far as I can tell.

This would be especially nice for the 19ft, which of course will have more drag because it is both wider and taller than the 17ft. We're #2 on your list for the 19ft, so I'm hoping this is where you're going.

Thanks for asking!

--mark

[Joe MacDonald]

having had a Trillium 1300, and now a 5500, I would have to say , on any trailer up to 17 foot, storage space is #1. with the 5500, we have enough space for everything except the dining tent, the folding lawn chairs, and the outdoor kitchen. Someday I'll get around to putting a fibreglass box on the back for these. The two of us and all our other gear fit in no problem. A small gain in fuel economy wouldn't offset the loss of storage for me.

[Mark Hayes]

I googled around for information on travel trailers and aerodynamics, but didn't find a lot of concrete information. Most people say that the deflectors on the TV are too far away from the trailer to do much good. Most seem to agree that a pointy front end on the trailer will help, but I could not find any specific numbers on mileage. Several articles say that side skirts work really well, but that's only done for semi trailers as far as I can tell.

There was an earlier discussion of this topic here:

http://www.fiberglassrv.com/board/in...howtopic=29086

--mark

[peterh]

Hi Reace,

I'm not sure it would make much of a difference, Reace. There are a lot of factors that come together to establish how much drag an object has, but the largest part of the equation isn't what the front end of your rig looks like, but how large the overall "wind face," the frontal area of your trailer, is that has the largest effect.

After the wind face (and contrary to what common sense says) the next largest factor in how much drag an object has is what the back side of the object looks like. Think about airplane fuselages: round and blunt at the front, long and tapered at the back. The back end is tapered to follow the natural flow of the air as it closes in behind the airplane body. If the back end of the airplane were as blunt as the front end there's be a huge, sucking low-pressure area behind to the rear trying to pull it backwards all the time.

The front end of your trailer is actually the place where you have the least control. You have no control over the aerodynamic efficiency of the tow vehicle and no control over the mid-vehicle airflow disruptions that occur between the tug and the trailer. I wouldn't stake a large amount of money on it, but I'm not at all sure that small changes in the front aspect of your trailer would have any noticable effect on towing efficiency as long as you maintain generally rounded outer and upper edges on your trailers. (Blunt, rapid changes of angle cause major disruptions in the flow of air over a surface, and that does causes substantial drag. This is one of the reasons why "egg" shapes like those of the Boler, Casita, and Scamp are easier to tow and create less drag than their "sticky" counterparts.)

The correct way to figure this out would be to make a dummy "bra" for one of your trailers, then tow it at 100 kph with a vehicle that has a fuel consumption meter hooked into the TV's ODB code reader, then remove the bra and try again. If you ever do that I'd love to hear the results.

[Glenn Baglo]

Ahhh....

The voice of logic, with information to back it up.

And, from me, a solution to those who want better mileage. Buy an Escape 13. You lose storage, but get better mileage.

baglo

[james kent]

Go for the aerodynamics.
If I, as a consumer, move up to a larger trailer then I'm already going to greatly increase both my living space and my available storage. Loss of, or the downsizing of, one front compartment isn't going to be a problem. I think it would only be noticeable to someone comparing the two styles or someone changing to a smaller unit. [yeah, right]
Take a unit off the line, chop it up, rebuild it, and do some road tests to see if there is a significant difference in towability or in gas consumption.
But then you've probably done that already.

[Joy A]

I vote for cupboards.

Sure aerodynamics is important but not that much with a small trailer being pulled behind a tow vehicle which buffers the air to start with.

I doubt you save that much on gas mileage with your design change. Not enough for me any way. What's a couple of mpgs....now if it were 10 or more mpg's I'd vote for aerodynamics.

I still say the tow vehicle has a bigger dynamic on the air flow with a small trailer.

[Jim Bennett]

I guess it would be hard to quantify the increased fuel economy by sloping the front back, but if it was significant, like 10% or more, I would surely be in to it. It would likely be different for each individual tow vehicle too.

How much upper cabinet space would you be losing anyway. If the back was to angle in by 1 foot, then you would only lose 2 feet of upper cabinet space. (One on each side)

Again, glad you are looking in to all these things, and it was great chatting on the phone. I am very excited to see what the final product looks like. I am sure it will fit our needs perfectly, way better then anything else out there.

[Bruce H]

RV manufacturers could take a cue from the trucking industry on this subject. With wind tunnel tests and principles of fluid dynamics used in the design process, the aerodynamic efficiency and fuel mileage of commercial trucks has improved dramaticly over the past 20 years. It would be a good subject for an on the ball RV manufacturer to exploit. They would be better able to do the research and change the design of their vehicles than individuals are. The aerodynamic efficiency of trailers and trailer/tow vehicle combinations is a little complicated because of the variety of tow vehicles but it could be figured out. Experiments could be conducted with different trailer shapes until they came up with designs and configurations that showed improved fuel mileage. The findings could be used at an advantage to market products. The trailer manufacturer that claims it's trailers are more aerodynamicly efficient and allow better fuel mileage and can offer some kind of proof is going to get a lot of attention.

[Reace]

I agree a windtunnel would be great if the funding was there! Hey....election coming up....maybe the govt want to chip in for a good cause!

Peter you make great points on the front and rear and I think this is where the Oxygen had a great aerodynamic design. I didn't want to go that far tho.

We are in the process of building a new 17' mold and angling the front end was something that came up after touring the local RV show this past weekend. There are some goofy looking 'stickys' trying to save fuel....but today it is something to look at.

Reace

[Doug & Anna-Marie P]

I think Peter's comments were pretty well spot on. I think for these considerations it's best to strike a happy medium between the two. You might already have that with your present Escape design with its rounded edges but less overall roundness than a Boler. And, personally, those stick builts with the slanted down front end strike me as clumsy and I wonder about their effectiveness.

Doug

[Andrew Gibbens]

We are in the process of building a new 17' mold and angling the front end was something that came up after touring the local RV show this past weekend. There are some goofy looking 'stickys' trying to save fuel....but today it is something to look at.

Reace, you already have the aerodynamic shape - it is the rounding of both the side and top corners of the front that really matters. Sloping the front a bit is 'styling' - it might 'look' enough like a low-drag shape to let another manufacturer justify feel-good claims in adverts or brochures, but what matters is the corner profile.

Here in Europe, trailer manufacturers do use heavily sloped front panels - but that is to make sure the very light hitch weight percentages used here don't result in a negative hitch weight at speed - the flow over the front of a trailer makes the front end lift as speed increases, but this will be much less apparent with the higher hitch weights used in America.

If you want to make the front end perfect, aerodynamically, then using an elliptical shape on the corners would be best - a tight radius next to the front, growing to a bigger radius as it smoothes into the top. After that, attending to the drag from the rear would be the next step, as peterh says. To cut overall drag, taper the back end of the roof down, really slowly, and end in a sharp corner - contrary to some folks' instinct the rounded corners on the rear will not be doing much good at reducing drag. However this suggestion would mean giving up headroom at the back of the body, so probably isn't very 'sales-worthy'.

For a view of what a really aerodynamic trailer shape looks like, see this new British semi trailer, with a long slow taper on the rear:





http://www.donbur.co.uk/gb/products/aerody...p_trailer.shtml

What is important to notice here is that the cross sectional area of the trailer has been [b]increased in order to enable that teardrop shape to be used - usually any increase in area means an equivalent increase in drag (it's the single biggest factor), but in this case, by tapering the roof very carefully, the reduction in drag factor (often called Cd or Cx) is greater than the increase in area. Applying this shape to a travel trailer with, say, 7 feet of headroom in the middle in exchange for having only 5 feet right at the back, might not be such an impossible idea.

Road vehicle aerodynamics (a hobby interest of mine) is a complex issue and it's easy to get wrong. Some wind tunnel time would be really useful, but it's hugely expensive - unless you have a college/university with an automotive programme somewhere near you, in which case providing them some real-world student research projects will get you welcomed with open arms.

Andrew

Edit: This old NASA paper on building full-size aerodynamic trucks is a good 'primer' on the subject:
A Reassessment of Heavy-Duty Truck Aerodynamic Design Features and ...