"TrailTop" modular trailer building components

[KCStudly]

I'm going to quote myself from a recent thread where a newb asked about foamies:
"...a basic foamie is built using expanded (those little balls squeezed together) or extruded (the blue and pink construction board) polystyrene foam as a core material with a canvas (or other cotton fabric) outer skin that is adhered using glue or paint. Once adhered, the canvas weave is saturated with more paint, similar to a glass composite construction.

The inner panels can be skinned the same way; with chip board (single ply paper box); or with thin ply (hybrid). Variations include using epoxy and glass for the skins, and using more wood inside (in my mind, a hybrid).

The key is to minimize the amount of wood. Basic foamies, like GPW's little camo 4wide, and Eaglesdare's Mickey have very little wood, just some hard points around the doors, are quite basic, easy to build, and can generally cost less than a more traditional build with more features.

Atahoekid's Road Foamie has epoxy and glass skin, and IIRC, wooden cabinets. Mine has a lot of wood in the cabinets with wood inner skins (The Poet Creek Express link in my signature below). Some people even use the canvas skin over plywood outer walls, but those aren't true foamies; that is more of variation on a 'traditional' instead of using aluminum skins.

Everything you ever want to know about foamies can be learned from reading The Big Thrifty Thread, but be forewarned it is a monster and comes with a separate index thread to help navigate through it."

GPW's FoamStream build is here (I refer to him as "The Godfather of the Modern Foamie Movement".

[jscherb]

"...a basic foamie is built using expanded (those little balls squeezed together) or extruded (the blue and pink construction board) polystyrene foam as a core material... Everything you ever want to know about foamies can be learned from reading The Big Thrifty Thread, but be forewarned it is a monster and comes with a separate index thread to help navigate through it."

GPW's FoamStream build is here (I refer to him as "The Godfather of the Modern Foamie Movement".

Thanks. Lots of reading material! I'll check it out.

[jscherb]

I was asked the other day if a TrailTop-based camper could be used on a landscape trailer.

Yes .



This one as drawn would have a door in the back. A teardrop shape could also be done for a landscape trailer.

[jscherb]

I don't know how interested you all are in the process of making fiberglass parts, so I'll cover a few steps here and if nobody's interested I don't have to cover this type of detail anymore. Of course someone building a camper with TrailTop parts wouldn't care about any of this, they'd just get the finished parts and start assembling things. But in case anyone's interested in how the process of making the molds happens, here goes...

The first step in making a fiberglass part is to have a "mold master", a part that's a perfect version of what you're trying to make (some fiberglass folks use the term "plug" instead, and some use the term "model", but I like "mold master"). Anyway, once the mold master exists, a mold is made from it, and once that mold is made, fiberglass parts can be made in the mold.

The initial TrailTop design consists of 4 basic parts - 90-degree corners, 12" radius curves, 36" radius curves, and 8' straight sections (which get cut to the necessary length for whatever design someone is building). So I've made mold masters for each of those parts. Here are the masters for the three larger parts. Mold masters typically have very large flanges on them to facilitate molding; these masters are no exception. The actual finished part won't include a lot of the flange area you see in these masters.

The 12" curves:



The 36" curves:



And the 8' straight pieces:



These masters are actually not the complete form of the final fiberglass parts - these masters only have the flanges for the side/roof panel attachment on one side. The reason for that is that if the masters had recessed flanges on both sides, once the mold was made, those undercuts for the recesses would lock the master into the mold. And if you ever did get the master out of the mold, perhaps by breaking it apart, the final parts would similarly be captured in the mold. So each of these molds will have a removable form to make the second flange. Multi-part molds like these will be aren't uncommon.

In the next post: making the molds.

[jscherb]

Making the molds from the masters is a several step process.

1. Coat the master with mold release, so the fiberglass used to make the mold won't stick to it. A good practice is to use two different types of release - first mold release wax (not "car wax"), then several sprayed-on coats of polyvinyl acetate (PVA). PVA is a water-based solution that forms a "skin" over the surface to be molded.

2. Spray a thin layer of tooling gelcoat on the master. Tooling gelcoat is a special gelcoat that will form the surface of the mold; it's different from ordinary galcoat as used on final part - it's much stronger and more resistant to heat. It's also typically red/orange or black, so it contrasts with the typically white gelcoat used to make the final part; the contrast makes getting the gelcoat sprayed consistently a bit easier.

3. Once the gelcoat has cured to the proper point (usually about 2 hours), multiple layers of fiberglass mat (and sometimes also fiberglass cloth) are laid onto the gelcoated surface and saturated with polyester resin. When an appropriate thickness is built up, the work is done and the mold is left to cure.

After the moldmaking process, they looked like this:



Once everything's cured (at least overnight), the molds are "popped" off the masters (usually they literally do "pop" as they release).

They looked like this after they were removed from the masters. These are just off the masters, the ragged edges haven't been trimmed yet.

[jscherb]

After trimming and washing off the mold release, the final step for these particular molds is to make the form that creates the second flange. For a production mold, these would typically also be made of fiberglass, but for my prototype part-making purposes, I made the bolt-on forms from wood.





That's it; these molds are now ready to be polished, prepped with mold release, and parts can be made in them.

The 90-degree corner mold is also in the photos above; I made that mold a few weeks ago and I've already test molded a bunch of those corners.

[jscherb]

As soon as I mold a first set of parts, I plan to assemble a prototype TrailTop teardrop to fit on my yellow Jeep-tub trailer. I want to do the work in my nice warm workshop instead of the cold garage, but I can't get the trailer down into the basement workshop, so I've set up a simple Dinoot kit in the workshop; it's the same length as my yellow trailer out in the garage, so anything I build in the basement to fit on the Dinoot kit will also fit on the yellow trailer.

Here it is mocked up with 30's/40's style fenders, which put the wheels outside the tub so they don't take up space inside the tub with inner fenders like they normally would...





A concept:

[KCStudly]

Great run down and explanation. Thanks for taking the time.

[bdosborn]

Hi Jeff, I've been watching your trailer thread over at Expedition Portal and I really like your concepts. I wonder how much help this would be for a on-road type trailer. A lot of teardrop builders spend quite a bit of effort on upscale finishes, as opposed to the more utilitarian builds I see at the Expedition Portal. Will your design accommodate an insulated wall as well a nice looking finish on the inside? For me, bolts visible in the interior would be an immediate deal breaker. Also, how are you sealing the joint between the plywood and the fiberglass to keep water out?
Thanks,

Bruce

[jscherb]

Hi Jeff, I've been watching your trailer thread over at Expedition Portal and I really like your concepts. I wonder how much help this would be for a on-road type trailer. A lot of teardrop builders spend quite a bit of effort on upscale finishes, as opposed to the more utilitarian builds I see at the Expedition Portal. Will your design accommodate an insulated wall as well a nice looking finish on the inside? For me, bolts visible in the interior would be an immediate deal breaker. Also, how are you sealing the joint between the plywood and the fiberglass to keep water out?
Thanks,

Bruce

Bruce,

Thanks for the comments and questions. Yes, over on the Expedition Portal and JeepForum they may have a different viewpoint on how a camper gets built, that's why I started the thread here as well. I believe the TrailTop design can offer a lot to on-road camper builders, and I want to get input and questions like yours to help me make sure I get the design details right.

As for bolts, the TrailTop components can either be bolted or bonded together, bolts aren't necessary - I think that question came up early on in this thread and I covered it in a bit of detail there. Similarly, the side panels can be either bolted or bonded to the TrailTop framework. If you bond everything, that does the sealing of the joints for you. If you decide to bolt the side panels to the TrailTop framework, I'd recommend some EDPM weatherstrip to seal the joint.

Also, there's nothing about the TrailTop design that prevents either insulating the walls or doing a furniture-quality interior finish like many of the TD's I've seen here. Finishing off a TrailTop-based camper would only differ in very minor details from insulating and finishing a wood-based or other type structure.

jeff

[bdosborn]

As for bolts, the TrailTop components can either be bolted or bonded together, bolts aren't necessary - I think that question came up early on in this thread and I covered it in a bit of detail there.

Here's the detail I was looking at. The offset isn't much, it would need to be at least 1" for a typical insulated wall panel - 3/4" framing with 1/8" plywood for skins. I suppose you could bond the plywood to the fiberglass with epoxy, would that be a strong enough bond without bolts (I've never done epoxy)? A teardrop gets most of its strength from the walls, you would need a good bond. Would epoxy waterproof the connection? What about the gap between the plywood and the fiberglass, could that be filled with T trim or something similar? The gap looks like a dirt trap to me.

Bruce

[KCStudly]

That was kind of my question, as well. A version with a 1 inch offset for 3/4 thk insulation, or even greater for 1 inch or 1-1/2 inch insulation.

My thought was that you could either epoxy or seal the panels at the bolt face (like a gasket), use the bolts to pull the joint together, then remove the bolts and use thickened epoxy to fill the edge and boltholes. Then skin the whole thing in epoxy/glass, or even canvas/glue/paint, ala foamie method.

Still, the cost to cover someone's tooling and layup time, plus shipping and profit... not sure what that leaves for a market considering that it will be sold to DIYers. The majority is more likely to find their own, more thrifty way.

[grant whipp]

Don't try to over-think and over-complicate this concept! What Jeff has proposed, here, is (or can be) dead simple and easily achievable with minimal time and tools ... I can see that a pure novice could have the basic watertight shell assembled and installed on a ubiquitous HF chassis in not much more than an afternoon ... and what they do with it from there is completely up to them, their skills, and their budget. It doesn't take much imagination to see one of these as a basic lightweight utilitarian shell ... or a full-on show-quality to-the-nines stunner ... it would all depend on how much effort, time, and money you want to apply to it.

I see a lot of possibilities for this ... ...! All it will take is for a couple of creative individuals (or maybe no-so-creative) to step up to the plate and show us their visions/versions ... I've already thought of a couple of dozen, and I really haven't dedicated very much time to it. Of course, the best results will come from someone willing to think a bit outside the box ... ...!

CHEERS!

[jscherb]

Grant, thanks - you definitely get what I'm trying to accomplish: something simple enough that a DIY-er can do it in a reasonable amount of time and end up with something he/she is very proud of, but also a kit that is a credible "blank canvas" for a more experienced builder whose goal is a showpiece camper.

One other thing, by providing a decent range of basic TrailTop part shapes, to enable the assembly of a range of different camper shapes, styles and sizes, all using the same family of parts. I'll have more shapes to ask everyone's opinion of very soon, stay tuned.

Bruce, KC, thank for the detailed questions. I've been in the process of creating assembly drawings for those and other details (like the rear hatch seal, for example). The drawings are still in draft form, and they've been a back-burner project so far because I'm trying to focus on getting the parts for a first prototype molded and that prototype assembled; also I'm reserving judgement on a few of the details until I've got the prototype underway and can decide which of the methods for some of these details I like the best.

Bruce, I've got draft drawings for five ways to handle bonding/bolting/sealing the sides to the TrailTop framework, with and without insulation, and at two of them use bolts and the bolts are not visible from the inside .

Both epoxy and two-part urethane structural adhesive are excellent and very strong ways to bond and seal the sides to the TrailTop framework. For the gap between the plywood and the fiberglass that you were asking about, I prefer urethane automotive seam sealer - it's very strong, comes in a few colors, and takes paint very well. For insulation, I don't think making parts with a larger recess offset is the best way to go; with the parts as they are it isn't hard to add insulation and an interior skin of, say, 1/8" luan.

I was planning on posting a lot of those assembly details a bit later in the thread, when I have the prototype TrailTop assembly underway and can decide which of the ways I like best and I'll be able to do photos to illustrate things. But in the meantime, if you've got more questions, please fire away and I'll do my best to answer them in the meantime until I've got final drawings of those details to post.

Thanks!

[mikerueve]

I'm with Grant on this one. This looks like something that would make a great starting point for a novice.
I am one of those people who have very limited wood-working skills and felt so intimidated by the building and
assembly process that we are having one built as we speak. I think that if there had been a "kit" like this available, that I might
have seriously considered taking a chance.

I love the idea of havng one that I built myself, but have to realize my limitations. That and the fact that we would like to start
camping again sometime this decade. I will be watching this thread with MUCH interest.