"TrailTop" modular trailer topper building components

jscherb

Expedition Leader
#1
First some background info:

Over the last few years I've designed and built several off-road trailers. Starting with a trailer made from the rear halves of two Jeep tubs (the yellow one below), I decided that project was too hard for the average DIY-er so I designed and built what turned out to be the Dinoot "J-series" modular fiberglass Jeep-tub trailer kit (the black one). After that I designed and built what became the Dinoot "M-series" modular fiberglass military replica trailer kit. Both of those kits turned out to be easy to assemble and fairly affordable ways for people to DIY-build their own custom off-road trailers.



I'm always looking for ways to make these trailers more useful, so not long after I made the yellow trailer, I built a camper top version of my Jeep Safari Cab hardtop to fit on it:





While it turned out that it would have been a nice camper top, I never took it beyond the primered prototype stage and never installed windows or other features due to other projects I was involved in at the time. Since then, I've always been thinking about ways to enable DIY-ers to easily build custom on- and off-road camp trailers using fiberglass components. I'm starting this thread so I can share some design ideas and start a discussion to get your input on the idea of modular trailer building blocks.

But before I post anything about my "TrailTop" design concept, I probably need to say this: I design and build these projects as a hobby. I am not in business to sell these, and I am not an employee of any company. Sometimes companies want to market what I've designed and I license my designs to them, but I am an not employee and never will be an employee of any of those companies. I'm just a guy with who likes to design and build things as a hobby.

Next post: the design concept...
 
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jscherb

Expedition Leader
#2
The "TrailTop" idea

While I like the Safari Cab-based camper top pictured in the previous post, I've been working an different idea - a set of modular building blocks that could be used to implement a wide range of camper styles (and other trailer-topper ideas). The basic concept is a series of fiberglass framework pieces that mate together with tabs, and accept 1/4" plywood (or other material) side panels. Using these framework pieces, a teardrop, for example, could be very easily framed up, and then sheathed with plywood.

Building a "Trailtop Teardrop" for a Jeep tub would go something like this:



It isn't necessary to base the top on a Jeep tub, the framework could be used without a tub to make a dedicated camper to sit right on the trailer frame. This next illustration shows two versions of a similar teardrop - the first version is made to sit on top of a Jeep-tub trailer, and the second is a standalone camper directly on the trailer frame:



There would be a range of TrailTop framing parts, for example different radii, corners, and straight sections. They'd all mate together, so you could assemble a range of different shapes and styles of tops. Here are a few examples:



And a few concepts based on my yellow trailer:



In the examples above, the hard cover, the RTT platform/gear storage, and the cargo/utility use straight rails and 90-degree corners. The camper with the barn door uses straight rails, 90-degree corners, and 12" radius corners in the front. The teardrop uses straight rails, 12" radius corners in the front, and 36" radius corners in the back.

The parts have a curve that matches the radius of the back corner of the Jeep tub, but a Jeep tub isn't necessary in order to use these parts as shown in the teardrop example above.

I'm in the process of making the molds for the first TrailTop parts right now. I'm posting this to start a discussion about this design idea - what do you guys think of the idea of a set of modular building-block parts that could be used to implement a range of different styles and designs? Opinions, comments, questions, design ideas?... I'd really like to hear what you think.
 
#4
Jeff,

I think you have a lot of very good ideas depicted there - great flexibility. I currently have a 4.5' x 6' x 2' steel utility trailer with a metal hard lid/toneau cover. So far I mostly use it to haul our folding dog crate, baby stuff, clothing bags, etc. when we travel, so the vehicle is relatively empty. I've thought about how I might remove the lid and add some sort of camper top for occasional weekend use. Seeing your images, I'm wondering if I could use those parts to create some modular options that could be installed when needed, removed and stored flat when not. For example, I could use your hard cover for regular utility duty/traveling, but add the cargo/camper sides between the lid and my existing sides if I want more interior room for an occasional weekend camping trip where I want to stay in the trailer. I'm not sure if you were thinking of that type of modular use (vs. using the modular pieces to build a fixed design). The keys would be how the pannels assemble and fasten and whether temporary fasteners would be strucutrally sufficient. I wouldn't be likely to actually use that type of modular capability if it involved intalling/removing 87 fasteners each time.

I know your experience is in fiberglas, but I also wonder if some type of injection molding/extruded plastic would work better/cheaper to build the framing parts. And regardless of materials, do you think it could be made in up to 8' lengths to accomodate full size wood, to be able to be cut down as needed for the actual length of the trailer?

What about a framing member across the middle of the trailer lid-top, that would enable a top wider than 4' (unless you are aware of another suitable and affordable material that comes in 5' widths)? It would create a seam that could leak though.

Have you got to the point of figuring out what the material profile would look like that would accept the 1/4" plywood? You might need either a different profile, or a profile that you could modify/cut in order to use at the bottom of the panel where it interfaces with the trailer side.

I can't wait to see how these ideas develop. As your ideas mature, it would be helpful to see some dimensions - i.e. how wide is the top on the jeep tub trailer? Thanks.
 

jscherb

Expedition Leader
#5
Jeff,

I think you have a lot of very good ideas depicted there - great flexibility. I currently have a 4.5' x 6' x 2' steel utility trailer with a metal hard lid/toneau cover. So far I mostly use it to haul our folding dog crate, baby stuff, clothing bags, etc. when we travel, so the vehicle is relatively empty. I've thought about how I might remove the lid and add some sort of camper top for occasional weekend use. Seeing your images, I'm wondering if I could use those parts to create some modular options that could be installed when needed, removed and stored flat when not. For example, I could use your hard cover for regular utility duty/traveling, but add the cargo/camper sides between the lid and my existing sides if I want more interior room for an occasional weekend camping trip where I want to stay in the trailer. I'm not sure if you were thinking of that type of modular use (vs. using the modular pieces to build a fixed design). The keys would be how the pannels assemble and fasten and whether temporary fasteners would be strucutrally sufficient. I wouldn't be likely to actually use that type of modular capability if it involved intalling/removing 87 fasteners each time.
Thanks for all the good questions and comments. I'll try to answer all of your questions...

Yes, I was thinking that modular use should be an option. On a Jeep-tub trailer, the TrailTop would bolt on/come off just like a factory hardtop:



If you built a door in the side of the Jeep tub, perhaps you'd unhinge the door before taking the TrailTop off.



And if you just built a TrailTop camper to sit on a flatbed trailer, the whole thing could come off.

I know your experience is in fiberglas, but I also wonder if some type of injection molding/extruded plastic would work better/cheaper to build the framing parts. And regardless of materials, do you think it could be made in up to 8' lengths to accomodate full size wood, to be able to be cut down as needed for the actual length of the trailer?
I think the economics would work out in favor of fiberglass. Yes, it's less expensive on a per-part basis to plastic injection mold a part, but the tooling costs for fiberglass are so much lower. Amortizing the cost of injection molds over the life of product like this that would have a fairly limited volume, I'm pretty sure fiberglass would be less expensive overall.

Yes, I've already made the mold master for the straight rails, they're 8' long; you would cut the straight rails to the necessary length for your top. Here's the unfinished straight rail mold master sitting on the workbench (along with the unfinished 36" radius curve master and in the background, the unfinished 12" radius curve master):



What about a framing member across the middle of the trailer lid-top, that would enable a top wider than 4' (unless you are aware of another suitable and affordable material that comes in 5' widths)? It would create a seam that could leak though.
I'm thinking that would be wood framing, and it would go cross-wise. It's not too hard to seal something like that well.


Answers to the rest of your questions in the next post, this one's getting long :).
 

jscherb

Expedition Leader
#6
Have you got to the point of figuring out what the material profile would look like that would accept the 1/4" plywood?
The profile has a recess into which the plywood goes:



A 3.5" radius corner is shown below. The corner piece is an actual fiberglass part (the only part I've made the mold for so far), the rest of the parts are drawn in place. All of the parts have recessed flanges where the plywood goes, and the corners have tabs to connect the straight rails to them. Here's an exploded view:



The TrailTop framing pieces connected:



The plywood in place:



This illustration only shows the 3.5" radius 90-degree corner; the 12" radius and 36" radius curved pieces will look like a curved version of the straight pieces.

You might need either a different profile, or a profile that you could modify/cut in order to use at the bottom of the panel where it interfaces with the trailer side.
I've designed the bottom, but don't have a drawing I can post yet.

I can't wait to see how these ideas develop. As your ideas mature, it would be helpful to see some dimensions - i.e. how wide is the top on the jeep tub trailer? Thanks.
The Jeep tub (CJ/YJ/TJ) and the Dinoot Jeep-tub trailers are roughly 59" wide. Since the TrailTop straight sections are 8' long and designed to be cut to length, the TrailTop parts could be used to build any width trailer, if you wanted something wider or narrower than a Jeep tub. Are there any other dimensions you'd like to see at this point?
 
#8
Jeff,
Looks like you are a very popular fellow...pm box is full.

Could you PM or email me when you have a few minutes.

Chuck
 
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jscherb

Expedition Leader
#11
Here are a few design sketches showing what the interior space in an 8' version of a TrailTop-based Teardrop might look like. This sketch is based on an 8' 3"-long "Double Dinoot" Jeep-tub trailer kit, although as I said yesterday, a TrailTop doesn't require a Jeep tub as a base - the TrailTop framing parts can be used standalone without a Jeep tub, so the interior room shown below would be the same with or without a Jeep tub.

In this first sketch, the mattress is sitting on the floor. The headroom is about 52", and the mattress is full-length.



This next one has a raised floor for storage underneath, but the same height (so less headroom):



If you wanted a raised floor and more headroom, the TrailTop could be made taller with the addition of a longer straight piece in the front, and a short straight piece under the 3' radius curve in the back. In these sketches, the front straight piece is 2' long, so if that were 3' long and a 1' long piece was under the 3' curve you could end up with the same 52" headroom but a 12" storage space under the floor. That's just an example, with the TrailTop parts you could build any height or width top you wanted.

This next concept isn't really a teardrop shape, it's more rectangular. It's built directly on a Harbor Freight 4x8 frame without a Jeep tub. It uses TrailTop 12" radius curves in the front, and the 90-degree radius corners in the back. The vertical straight pieces could be cut to make the camper whatever height you wanted. In this drawing the front straight rail is about 3 1/2' long, making the top about 4 1/2' tall. I've put 30's/40's-style fenders on this one for a retro look.

 

jscherb

Expedition Leader
#13
A question as come up about whether I am "affiliated" with the company that sells the Dinoot trailers.

I design and build projects like this because I enjoy the design challenge; it's my hobby. Some guys watch football as a hobby, some guys collect stamps, some guys go hunting, I design things.

I am not an employee of or contractor to the company that sells the Dinoot trailers (or any company for that matter). I designed the fiberglass Jeep-tub trailer as an independent hobby project and after I finished it, I was approached by the company that now sells it and they asked me if I was interested in licensing the design to them, so I did. Same thing with the fiberglass military replica trailer tub kit, I did that as a hobby project. I am not designing the TrailTop parts for any company, I am designing them because I think it's a innovative idea I've come up with and it's an interesting design and construction challenge for me. I'm designing them to fit on top of my Jeep-tub trailer design, mostly because that's the trailer I have here to work with. It's not even a Dinoot trailer, it's one I fabricated from the back halves of two Jeep tubs. And the TrailTop parts don't require a Jeep-tub trailer anyway, as I've shown in concept drawings, they can be used without a Jeep tub.

It shouldn't be inferred from anything I post that what I'm doing will ever be a commercial product, and I don't work under contract to any company, everything I do is for my own hobby fun. I never, ever do work for hire.

I am always willing to talk to any company that is interested in licensing my designs, but in only one case in the last 5 years have I ever sought out a company to try to get them interested in licensing one of my designs (and that wasn't a design I posted here). I do these as a hobby to satisfy myself, and if they get interest from companies, that's nice, but if not, that's perfectly fine with me.

Sorry for the long explanation, but I want to make sure there's no misunderstanding - this isn't a commercial thread, it's my hobby.

Now back to the TrailTop discussion, let's have some fun talking about the project :)...
 

jscherb

Expedition Leader
#14
Here's an example of using the TrailTop 90-degree corners and straight rails to make a hard cover for a trailer.

An exploded view:



The TrailTop parts connected together using the tabs on each part:



The plywood in place:



In this concept view, the cover is on a small Jeep-tub trailer. It's hinged on the passenger side, and there are latches on the driver's side (shown). The tan color is the plywood.



Painted and with rack bars installed:

 

Hilldweller

SE Expedition Society
#15
Nice stuff! Thanks for posting.

I've drawn up similar ideas to this one below --- with drawers that open and slide out to the side of the trailer under the bed.