Few Questions About Aerodynamics of DIY Travel Trailer

[Hersbird]

Oh and BTW, there is a great calculator that is a sticky on this aerodynamics forum so you can see how much better .18 Cd is compared to .34 or how much better 30 sq ft is than 80 sq ft, or 4000 pounds is than 10,000 pounds all at different speeds.

[kach22i]

Originally Posted by Hersbird

This was my first attempt on a $1000 Hi-lo........

Great post, and yes if it costs you $5,000 to build your dream trailer from scratch and takes you five years to do it, that fixer-upper is extremely attractive in more than one way.

A $4,000 difference is a lot of gas money in your pocket - just saying.

Originally Posted by Hersbird

Oh and BTW, there is a great calculator that is a sticky on this aerodynamics forum so you can see how much better .18 Cd is compared to .34 or how much better 30 sq ft is than 80 sq ft, or 4000 pounds is than 10,000 pounds all at different speeds.

Good reminder, I forgot about that.

[stcyrwm]

Originally Posted by kach22i

The depth allows for plywood or other rib/frame needed as the roof is all open, picture a pick-up truck bed that has a top flange - there is thickness otherwise the bed side would fold in. The alcoves between the spars would be for shelves or counters. I would have to draw this up for you to understand, it's not typical in any way.

https://projectviper.wordpress.com/2014/08/

That Viper project is crazy cool!

I think I will be doing a framing system that will be a fair bit simpler, grin...

[stcyrwm]

Originally Posted by Hersbird

A big thing to keep in mind is frontal area, you can get great Cd but if it has the frontal area of a standard camper (mine is almost 10 feet tall and 8 feet wide or 80 sqft) you still will be at a disadvantage compared to say a pop-up camper that is just a box but follows almost entirely in the wake of the tow vehicle. Best of all worlds would be a low profile pop-up camper that actually improves the Cd of the tow vehicle by making basically a boat tail trailer.

What happened to your HiLo?

If I went pop up style I would probably get a used Trail Manor unit which is a brilliant design in its own way as it definitely gives the small frontal area with a pretty healthy interior space. I think if I had more confidence in my capacity to reproduce the lift mechanism and slideouts, I might give it a go.

Thanks for pointing out that sticky. I will check it out for sure.

Bill

[kach22i]

Originally Posted by stcyrwm

Trail Manor ........... lift mechanism and slideouts, I might give it a go.

That is a brilliant design.

An older design I was playing with had a 2-foot high base that an aerocap lifted up from. Now the TrailManor gets into my head and I question rethinking it all.

My latest design sketch relies on a simplification; a piano hinge and gas springs mid-roof pop up verses the complexity of telescoping an entire cap.

The TrailManor seems just a little beyond a home-build concept with the engineering involved, but not by much if you can live with some potential leakage.

https://www.trailmanorowners.com/for...ead.php?t=4003


That Gif helps, at first I thought it went straight up and then slid horizontally, not so with the scissors mechanism.

[Piotrsko]

Pivot is simple: 2 parallel rods of what ever height is needed set up as a parallel ogram on each side. The swing is a very flat upside down "U" and ending point is the same height as the start. The length of the rods determines the horizontal offset and incidentally the apogee of the swing. Like a swing out shelf on a fishing tackle box.

[kach22i]

Originally Posted by stcyrwm

That Viper project is crazy cool!

I think I will be doing a framing system that will be a fair bit simpler, grin...

I found an update, as I had not looked past the Spitfire example.

March 16, 2019
https://projectviper.wordpress.com/2...-engine-start/



Not FAA approved I assume, but it's going to make a great parade float or something like that.

.................................................. ....

Back to the TrailManor.

http://www.trailerlife.com/rv-gear/r...le-downsizing/

Once the bottom latches are released, torsion springs help lift the front section into position. Repeat the process for the rear section, then pull the king-size bed into place from underneath. After the door and frame are assembled, a conveniently located switch just inside deploys the front slideout. Exterior foot stirrups assist with the closing procedure.

I'm wondering if TrailManor has gone though several generations of improvements over the years, or if they all work exactly the same.

Because the TrailManor’s top halves close over the bottom half, there has to be a way to create a seal from the weather once the trailer is fully open and the halves no longer overlap. TrailManor’s solution is to fit the trailer with insulated flaps that fasten with hook-and-loop material. Leave the flaps unfastened, and the breeze is free to circulate throughout the trailer. In this way, TrailManor has effectively provided users with a way to enjoy the most positive aspect of tent-trailer camping — without the cloth walls.

[slowmover]

The interior finish-out is the killer. Where mistakes can’t be fixed. This was a FULL-TIME staff design position.

There are still plenty of:

AIRSTREAM
AVION
BOLES AERO
SILVER STREAK
SPARTAN
STREAMLINE

brands of travel trailers out there. Too many have been gutted due to owner stupidity (no other word for it). The classic era of 1960-1990 features space utilization that won’t be matched.

Go to VIEWRVS.com

The aero problems are solved. For a likely lower cost for a decent shell-on-frame than the materials alone working from scratch.

Be willing to travel. Airstream was the entry level bargain brand. But sells used for too high a price compared to other brands. And wasn’t as well made. This route would put you years ahead.

Building it may be the motivation. So let me say that even restorations take years. How old are you (not quite tongue-in-cheek)

You don’t need a pickup or van to tow unless that’s best for solo use in your case. But an empty bed makes a lie of “need”. Family car with small open trailer can carry more than a one ton pickup. Pickups and RWD vans are inherently unstable.

Road-going stability won’t be there in the first DIY attempt without pro engineering help. This alone would cause me to find a mechanics special.

.

.

[stcyrwm]

Originally Posted by Piotrsko

Pivot is simple: 2 parallel rods of what ever height is needed set up as a parallel ogram on each side. The swing is a very flat upside down "U" and ending point is the same height as the start. The length of the rods determines the horizontal offset and incidentally the apogee of the swing. Like a swing out shelf on a fishing tackle box.

I know, I know - I have thought about that a lot. It all seems so simple and I guess, really it is except that there are so many other factors like sealing it all while traveling and while it is in position. How to do the bottom slideouts on each end and then seal and support those in alignment with the lifted units etc.

Part of me would love to take on the challenge just for the fun of it and part of me wonders how much I would regret it, haha. My guess, from what I have read is that there probably is no more fuel efficient design than some kind of pop up so this keeps coming back to me. And then of course there is also the alternative to just buy a used one but that would be way less fun, grin.

Either way, it is fun to ponder and I do appreciate the encouragement.

Bill

[Hersbird]

I thought about Trailmanor and there was a used one but I think even if you buy a factory built one you might have to put up with a little leakage.

Obviously my Hi-lo suffered from some leakage as well, probably around the windows which you would think would be easy for a "professional" company to install and seal for life. The leakage there rotted the bottom sill of the top clamshell and most of the side wood. The rear cables pulled from their mounts dropping the top. This all happened before I got it. I wouldn't trust even the repaired cables at that point and always braced the 4 corners up inside with 2x4's if anyone was inside with it up.

I have come to question, "why make everything hard sided?" which both the Trailmanor and Hi-lo limited themselves with IMO. Now I have a "hybrid" camper where it's full height and hard sided but both ends pop out with queen tents. I have lost the low profile and towing MPG sucks, but oh baby the room this little 20' trailer has! This is my "honey is going camping camper". She wants the soft beds and private potty. As far as we will go is about 5 hours to Yellowstone. (That is the one place a single campground requires hard sides, but that campground stinks as it feels like you are in the Walmart parking lot and I wouldn't camp there anyway.) Basically 9mpg only going 1000-2000 miles a year isn't going to break us. Just 3 nights hotels in or around Yellowstone would buy 2000 miles worth of gas. When I retire and we go on longer US tours we will do it differently, hopefully in a diesel high top van.

I personally love going out with out wall tent. I just got back from a "breakout of winter trip" with my daughter and 4 boys of a friend, and used the wall tent (which is kind of a frameless circus tent design 12x15' and a good 10' high in the center. I do wish I had a small kitchen trailer as it's hard to fit 6-7 people along with all the gear even in a Suburban and then setup and teardown takes an hour or more depending on how much those boys pitch in. We have gotten in to "bushcrafting" as well and you need some raw land for that normal trailers will have trouble getting in to. I know, the wall tent doesn't qualify but in my defense it was 20 degrees and there are still patches of snow 2' deep all over.

I'm blessed to live here in Western Montana and there are still a 100+ places I want to camp within 4 hours. I would like to do things as economically as possible, or with clever designs just because they are cool. Some designs like the Cricket trailer seem to be cool but not necessarily clever or better. I kind of have that opinion of Airstream, but their design is cool and better executed but they have size issues. An expandable Airstream or why not a hi-lo Airstream, or at least a slide out. Then there is the price already. I know they are built well but really that well? Even if my camper was complete garbage after 10 years it would work out to a better value. My buddy has a Jumping Jack which is also a pretty dynomite setup especially if you had a ATV to bring along.

Building stuff can be fun in itself. I even came up with a name for my unbuilt, teardrop/popup, the "Drag-gone".