Teardrops n Tiny Travel Trailers

I’m going to build by own popup hybrid camper, and I’m leaning toward a foamie. The box will be 11ft x 6ft, 30” high, with a rear bed, front dinette, and cabinets between. The roof will be tapered with a max height of 15” (when closed), with a hinged roof and foldable hard sides. When raised, I will have over 6 ft of headroom for the section forward of the bed, where the cabinets and dinette are. I want to keep it under 1400lbs. I have my donor frame - from an old palomino popup – I think I can use it with minimal modifications.



I’ve read lots of build logs, but haven’t seen anything that addresses a couple of my concerns:

As this will essential be two open “halves”, only attached by a piano hinge at the back and lock down clamps at the front (when traveling); will foam give enough rigidity to keep it from flexing, or do you think I’d need a stick frame (say 2x2) with XPS? I will use PMF for the exterior, and probably interior as well. I think that if I have enough rigidity during traveling, it will also be rigid when popped up. And I’ll like to use 1 ½” XPS rather than 2”, as I have a lot of aluminum trim pieces that I can use (which would be incorporated into the box and roof rails, like a traditional popup.

The hardwall sides should be pretty light using 1” foam construction, but will probably have aluminum banding. I know I have a lot of water sealing to do where the box and the roof meet, and where walls meet the roof, but the donor camper had folding hardwalls and I may be able to re-use a lot of the weatherstripping trim pieces.

Any comments or suggestions are appreciated. I’m still at the design phase, but have my frame stripped and will start prototyping some of the more difficult aspects of the build soon.

There's only one manufacturer who builds these commercially, but I'm gonna do a pop-up that is about a little shy of 4 ft lower and same size over that is solid walls. Raise the outer up completely and it's hard shell no canvas. Light and insulated for weather and sounds. Keep it below tow vehicle wind profile so easier to pull. The commercial is crazy expensive.

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Sorta’ like half an A-line huh ??? Don’t think anybody’s done that in Foam around here… COOL !!

I like your design idea. Steve, are you asking about the roof rigidity or lower half or both? Lower half will be rigid by internal support from furniture elements. Roof can be made rigid by its geometry and structure. I am not sure about PMF, but the roof epoxy fiberglass sandwich in my build 1-1/2" XPS is rigid enough. Here are some other considerations.. Instead of flat sections that may sag with time, consider a slight curve in the the roof along the length of the trailer which will add rigidity and shape stability, and possibly better towing due to aerodynamics. With such roof length and small curvature there should be no need in kerfing the foam. I did all panel lamination and glue-ups in horizontal position and then assemble. I do not know if you really need aluminum banding. The reason they use it commercially is because it is faster(cheaper) than other methods of making the edges. I personally do not like aluminum banding because it is a thermal bridge between the skins, possibly additional weight, I do not like the look (but it is again only my opinion). Hope it helps and good luck with your design, keep us posted please.

Where is the door?.

I started exactly the same concept on an old PO trailer except with hinge on the front and door on the back. I used the PO box and interior. Curve your top for more rigidity, 1.5" foam and pmf will be fine. I used a wood around the bottom of the top to have something solid to screw into.

Never finished it and sold the trailer. Used for a hunting shack now.

PM , all the guys around here look at these Foamies, and all they say is “ Hunting shack “or “duck blind” , suggested was the "Popup top" …

SL139 , could be something to this eh ???

I would consider turning the floor plan around so the hinge is in front and the opening in back, if for no other reason than to avoid an accidental blow opening (while towing after forgetting to latch or a faulty latch scenario). That would have the potential to rip the roof clean off and perhaps result in other liabilities. Not that it is super likely, I'm just of the mind to make such design considerations and to incorporate as many "positive" elements early in the design as possible when there is no reason not to.

I would definitely incorporate a hard edge in the top of the bottom wall, and around the lid opening, hardwood where the hinge screws on. These areas will be the most prone to strikes from misc objects and actions, so you want them to be dent resistant; not to mention the added dimensional stability, at least during construction, if not thereafter.

Hi,

Nice design! I wish I could help you with it but it's hard to know what to say not having it in front of me to see all the construction details.

I think with foamies you need to anticipate where you need rigidity and hard points to attach things to. I can't wrap my brain around how you would do a door for a pop up.

I'll add this bit if information based on my travels with my foamy. My trailer is a little taller than my tow vehicle but I don't notice wind resistance as much as I do the hills.
I can cruise along in overdrive with gentle hills but it is the steeper ones that make the engine work in order to maintain speed. I usually slow on the steeper hills to keep from going into 4th and 3rd gears. That's the interstates and 2 lane highways in Virginia, more hills and mountains the further south and west I go. My Xterra will keep the speed up if i just give it the gas though, depends on how impatient folks (or me) are behind me.

Is there a door?

As this will essential be two open “halves”, only attached by a piano hinge at the back and lock down clamps at the front (when traveling); will foam give enough rigidity to keep it from flexing, or do you think I’d need a stick frame (say 2x2) with XPS?

For what it’s worth, here are my two cents:

I don’t worry about the closed state, nor do I consider the key question to be rigidity of the erected configuration (top raised and latched)....

Yes, it is true that a opened pop up does not have the rigidity of the classic tear drop or even that of a simple fixed box trailer, even though the two halves are latched together. This is especially true with a telescoping top because (unlike the base), the top can not have cross corner reinforcement (it has to nest over the bottom). However, my chief concern in designing the Tip Top Tier Drop was always the stability of the top during erection before it is latched to the bottom. Diagonal flexing was my major worry because the top had to be manually raised (by an elderly weakling with no assistance) and that meant holding it in the raised position with one hand while latching with the other. Finding the right balance between stability (rigidity), cost and weight was my aim and that drove me to experimenting with very marginal construction to see what I could achieve.

Manual lifting also put a limit on open height since I had to be able to reach a height clearing the latches. I knew this would be problem with camp sites that “rolled off” in the back, but what I under estimated was how often that would be the case. In fact, many camp site pads have a log back stop (which often ends up under the rear of the trailer) and a steep drop-off beyond it, creating quite a step down off the back of the trailer. We keep a stool handy for such situations, but sometimes that stool is needed just to raise the top.

Your diagrams show the reverse, the top is hinged at the rear, which has an obvious advantage in such a case. Also, your flip-up end and side walls should reduce lift weight, but there are set up exposure advantages with telescoping designs. In any case, I find clam shell designs well matched to manual erection constraints.