Which Trailer shape is better??

[Frank Lee]

Nice idea but he needs to be able to get in it.

The hatch extension is probably a good idea, modifiable to be useful even on a trailer that is taller than the car.

[Sven7]

I bought a Toyota RV-2 promotional card today and thought it might apply to this project. Have you considered having the roof "open" for more interior space when parked?

[jakobnev]

Originally Posted by Frank Lee

Nice idea but he needs to be able to get in it.

A two part boat hatch on the front edge where it it tallest:

Project: Ericson 29 Teak Cabin Hatch Boards Refinish | I Sail Away

[skyking]

Ed,for a pop up version of any of the trailers these guys have drawn up, I need to know what materials you had in mind. Work with what is comfortable for you. If sheetmetal, we could make the top section out of EMT and skin and insulate it for example. As small as that trailer is, the roof is in range of "crouch into it, lift up roof by standing up" with no mechanisms. I can design a simple toggle that you pre-set, once the roof is high enough the toggle falls into place at each corner and you let it back down.
To reverse the process, you re-position the weight on the toggle. Lift up and it unlatches for you, let roof down.
Hang the door on the roof section, opening out. After lift, install a 2' door section on the bottom to fill that hole, done.
It opens up those aero designs like jacobnev's or sven7's (very nice) and lets you build low and live high. Both of those designs have that 2' section of straight side for the slip.
If building for cold weather, you need at least a 2" wall insulation. making it pop up will reduce interior width 4.5", 2" each side plus .25" for clearance. Small price to pay for stand up comfort.
Use sliders made from UHMW plastic strips at the corners, installed with countersunk rivets. This stuff is very very slick and tough, and will prevent binding.
My material of choice is a XPS foam core covered with very thin veneer inside and out, layer of glass/epoxy, and finish with linear poly. That may not be in your comfort zone but it is what the really light and fast boat builders would do.

Edit 1: I would build the trailer out over the wheels, as close to the Tow vehicle width as possible. Add a center divider over the hitch tongue to keep the crosswinds from crossing over the gap. aerohead has these ideas around here somewhere and explains them well.
The XPS/veneer/epoxy/glass sandwich weighs in at 0.6 lbs per foot at 2" thickness. take off 0.08 lbs at 1.5" thickness.
5'x11' plus 2' side is about 120 feet. it would weigh in at 70~80 lbs.
Use the bluecor .25 foam and build it up, making radii as you lay it up. each layer bonded into a radius gets stronger and stronger, think motorcycle helmet.
http://building.dow.com/na/en/produc...on/bluecor.htm

[KamperBob]

Originally Posted by Ed-in-Maine

Kamperbob,-yes HF base is 4'x8', I've been thinking of widening to tire width but it's not giving much more utility. The design has a his/her door on each side. But craw over isn't that bad, had to do it on our last two boats.
That Airstream looks sharp but I was glad to be sitting down when I saw some used prices OMG Also weight becomes an issue. I have an uncle towing a Scamp 13' with a Matrix, IMHO he's nuts. I want to keep empty trailer weight under 600lbs, loaded for highway 1000lbs.

Ed, I agree those Airstream Basecamps are outrageously priced. Even if I won the lottery, rather than buy one I'd rather build a factory and make my own. LOL

Yes, weight is important. I have many camper designs swirling around my head. I've sketched up some to work out geometry and trade-off puzzles but currently lack the facilities to build anything. But I have varied skills and experiences working with a range of materials. My current favorite approach for projects of this magnitude is fiberglass coated foam board. Some years ago a gentleman used this approach to make a full slide-in camper that he said weighed only 600 pounds! Sadly, I lost the link... (pout)

[euromodder]

Originally Posted by Frank Lee

I forget, is it 36"+ where the gap really starts to hurt aero?

It's a tough situation, making it as close as possible without risking hitting the trailer when backing up, going over bumps and dips,

A splitter plate on the centerline would do the trick.
A single plate wouldn't be an issue when turning or backing up.
It can go as far forward as the hitch, but then it should angle back a bit to clear the tow vehicle.

[euromodder]

Originally Posted by Ed-in-Maine

Hi All,
I've scrounged up some power tools and will start building my truck Duck Tail and a small "Teardrop" camping trailer.

Teardrop trailers all have too much / too fast a drop on the rear .
They often end up as nearly semi-circular, the kind of shape you really need to avoid on the back end.

Basic dimensions are set at 4' wide, 4' high and 8'-10' long(could go a little longer if that helps).

Longer helps - it gives you more volume, and the teardrop can be longer / less steep / more gradual, so it more closely matches the streamline template.

[aerohead]

Originally Posted by Sven7

Here's my design in Alias. It combines space efficiency with aero efficiency and complicated surfaces with ease of construction.

I know that it would be a pain to fabricate,but to have upper edge radii could shave as much as 0.043 off the Cd.It would really reduce the roll moment as well,which knocked Sheppard's beautiful new trailer over.

[aerohead]

Originally Posted by Frank Lee

I forget, is it 36"+ where the gap really starts to hurt aero?

It's a tough situation, making it as close as possible without risking hitting the trailer when backing up, going over bumps and dips, etc. Perhaps the best solution is some sort of flexy fairing that can close or at least partially close the gap without damaging anything... I seen some attempts at that on tractor/trailers but not at the consumer level.

I'd call Sven's proposal (c)- it looks quite good... now put radii on the leading and upper edges.

In Hucho's 2nd Edition,p.180,Fig. 4.98,he shows a Morris Minor 1000 notchback,and Traveller squareback pulling a small caravan trailer.
For the notchback,the drag curve shows a maximum @ 36" gap.
For the squareback,the drag maximum is at about 39.3".
For SAE Paper 870714,with matched-height,parallel-face tug/trailer, a 21.6" gap produces only a 2.3% drag increase.
For stock cars in a 2-car draft,the trailing car,going from bumpers touching,to about a 36" gap would raise the Cd from 0.185,to 0.193,about 4.3%.
For two identical Mercedes-Benz buses,going from touching bumpers to around a 36" gap,would raise the Cd of the trailing bus from 0.167,to 0.21,about a 25% drag increase.
Since the buses don't have 'bumpers' per se,they might best reflect the significance of gap drag.
In Abbott and Von Doenhoff's Theory of Wing Sections,they depict a Clark-Y airfoil with varying degrees of gap(slots) along different positions of the cord.The Cd of the wing can vary from a minimum of 0.0152,to 0.0208,based on surface area skin friction drag.
NASA reported 19% drag for their C.O.E.semi-trailer with 31.2" gap.

[Ed-in-Maine]

aerohead- Yes the model Sven7 made is beautiful, needs to be a little farther forward in the trailer I think in order to get the departure angle high enough for our driveway. My problem is my skill set and tools are limited to plywood and lumber and basic shapes. I'm having a devil of a time trying to fit that form in to tortured plywood. WHILE being frugal, i.e. using dimensional lumber without a lot of waste. That's kind of the beauty of the original TearDrop design, 3 pieces of 1/2" 4'x8' for floor and walls.

But I'm still trying to come up with a build design that I can actually build

skyking- thanks, looking into those material.

THANKS EVERYONE No matter what I build it will be better because of this forum.
Ed


{edit} By pulling out the sides to enclose the wheels and give the slick aero plan shape and lowering cd, would the increase of an estimated 8sqft of frontal area of the trailer and the needed mirror extensions on the car offset any decrease in cd?