Alu-Cab ModCAP Hard-sided Popup Build

[Alphamacaroon]

I also just realized that the area calculation in my cad program was excluding the window cut out.


The real square footage is 18.03, and if we take our 17.8 lbs (weight without aluminum), it ends up being 0.99 lbs per square foot. So it seems my scale is fairly accurate because it's right about where we'd expect it to be based on the JM datasheet.

TLDR; GoBoard composite panels and Carbon-Core panels are basically equal in weight according to their datasheets, and that is confirmed by real world measurements.

 

[rruff]

I have performed some very unscientific strength, stiffness and impact tests, and while I can't compare it to FRP panels (because I have none), I can say that they seem to meet the standards for my project. Only time will tell, but at $3.66 vs. $10.00 per square foot I can afford to screw up a few times

Mine are pretty unscientific also. I checked to see if stiffness was what I expected for FG and carbon hand laid skins (they were, with carbon being ~2.5x stiffer) and for strength I decided that impact... or "whack it with a hammer" tests... were the most relevant, and FG was better than carbon for similar thickness, though by weight it was probably about the same. This was a small sledge hammer and Carbon Core 4lb PVC. For most panels I have ~32oz/sq yd FG plus epoxy, and 1.5" core weighs ~1.5 lbs/sq ft. I used carbon for the base and door, where I wanted more stiffness.

Note Carbon Core's panels have PP hex core and I think 17oz/sq yd FG+resin skins, so it's a structural panel. Similar to what Aterra uses, if not identical.

I'm curious how stout the skins and foam are on the panels you have. They can be bought in 4x8 sheets and up to 2" thick, though these are not typically stocked.

 

[Alphamacaroon]

Mine are pretty unscientific also. I checked to see if stiffness was what I expected for FG and carbon hand laid skins (they were, with carbon being ~2.5x stiffer) and for strength I decided that impact... or "whack it with a hammer" tests... were the most relevant, and FG was better than carbon for similar thickness, though by weight it was probably about the same. This was a small sledge hammer and Carbon Core 4lb PVC. For most panels I have ~32oz/sq yd FG plus epoxy, and 1.5" core weighs ~1.5 lbs/sq ft.

Note Carbon Core's panels have PP hex core and I think 17oz/sq yd FG+resin skins, so it's a structural panel. Similar to what Aterra uses, if not identical.

I'm curious how stout the skins and foam are on the panels you have. They can be bought in 4x8 sheets and up to 2" thick, though these are not typically stocked.

I have a gut feeling that the Carbon-Core panels will likely be better in impact tests because of the plastic in the skin. If you hit the GoBoard hard enough it will leave an indentation, but maybe that's desirable in some cases where you'd rather it deform than to crack?

In my case I'm worried more about strength and stiffness and less about impact resistance, because these walls will only see the light of day when the vehicle is fully parked.

 

[rruff]

Oh that's right, these are only for your pop-up pieces. Much less structural concern there... after all, most are using canvas...

 

[Alphamacaroon]

The gussets arrived today from SendCutSend.



Must say they did a great job! They are quite large, but like I said in a previous post, I'd rather they be oversized at this point because I can always downsize when I know my final weight.

Before you ask, yes, the access cab doors fully open, but it's close. I designed it to be close, but would have preferred just a tad more room, but it's fine for now.

 

[Alphamacaroon]

Pretty cool to see the walls in my 3D renderings take shape in real life!

 

[Alphamacaroon]

It's been a while since my last update, but the summer has been filled with other commitments and travel and I just haven't had a lot of time to work on the project. But I do have some progress to report— the walls are functionally complete and they do seem to fold and unfold!



A few notes and thoughts on the process:

• In order for everything to work perfectly the measurements really have to be precise. I cannot stress this enough— the more precise the measurements, the easier it will be to seal against dust and water. The whole build process for the walls probably took 2-3X longer than it should have because of the constant measuring and re-measuring just to make sure everything was right before I cut. The good news is that all this extra time ended up saving me money because all my cuts were right the first time and nothing was wasted. That being said...
• When I cut and measured everything for the GoBoard panels I failed to account for the thickness of the adhesive (SikaFlex) that would bind the aluminum edging to the panels. Because of this, everything ended being 1/8" to 1/4" larger than I expected. It really didn't make that big of a difference in the end because everything was larger by an equal amount, and 1/8" to 1/4" difference isn't all that much over the span of 10 feet. But in the future I would certainly take this more into account.
• I'm really in bit of a conundrum at the moment. More likely than not I will need to make some tweaks to the frame and wall system before it's done, so I don't want to fully paint or finish anything until it's completely functional and I know how it all fits together. The problem with this approach is that it means at some point I will need to be able to completely tear the whole thing down so that painting and finishing can happen. Originally I had planned on using continuous poly hinges for the wall sections attached with VHB tape or SikaFlex, but both of those methods are relatively permanent, so I decided to abandon that route and go with stainless steel piano hinges (I found them at Home Depot) attached with self tapping machine screws into the aluminum edging. This method will allow me to detach the hinges when I'm ready to tear it down for paint and finishing. During final assembly I will probably end up going with rivets to replace the machine screws, because there isn't much bite for threading in the aluminum C-channel and it's too easy to strip them out.
• I did some initial finishing on the triangular shaped panels (the black colored ones on the above picture) just to see how it would turn out. I sprayed a couple of coats of self-etching automotive primer, followed by a couple of coats of spray can bedliner. The results look really clean IMO! The bedliner spray not only adds waterproofing (although GoBoard is waterproof already), but seems to add a nice layer of impact resistance, as the GoBoard on its own will deform if hit hard enough.
• One thing you'll probably notice is that the front and back walls are taller than the side walls— this is by design. I'm 6'1" and would prefer to be able to stand at full height when I'm inside. The challenge is that in order to fold properly, the side walls can only be as tall as half the width of the shell. Because the Tacoma isn't a full-size pickup, half the width of the bed doesn't add enough height to the top of the canopy shell to reach a height of 6'1". But, it turns out we can take advantage of a little loophole— the front and back walls can theoretically be as high as half the length of the entire frame— 5 feet vs 2.5 feet. Adding some length to the front and back walls ends up extending the interior height to 6'3"— more than enough for me. The problem however is that you can't make the front and back walls too much higher than the side walls, or you'll have a huge gap between the side walls and the roof. So the trick is to take advantage of the height of the overhang of the roof panel. When the roof is in the closed position, it needs an overhang/wall to seal up the entire unit as it sits on top of the three layers of folded walls— the overhang is roughly 4-5 inches. So we can take advantage of that overhang to account for the difference in height of the front and back walls and the side walls— the front and back walls will tuck up into the top side of the overhang, and the side walls will tuck up into the bottom side of the overhang. It should work... in theory. Which leads us to the next step.

The next step is to build the roof! But if I'm being honest I don't really have a great design for it yet. Some considerations I'm thinking about:

• So far I'm extremely happy with the way the GoBoard walls turned out— they seem to have the perfect mix of being lightweight and strong. And the wall sections need to be relatively strong and rigid because they provide structural integrity and need to be able to stand up to wind and the elements, but I'm not sure the roof will need to be as beefy. So to cut down on weight even further I'm considering fabricating an aluminum frame which will be covered by aluminum composite paneling and then insulated with XPS foam board. We'll see— by the time I do all the calculations it might not be all that much lighter than just using sections of GoBoard.
• I haven't fully figured out how I'm going to provide a good seal for dust when the popup is in the closed position. The wall edges come awfully close to the edge of the L-channel frame, and so I'm not going to have much room to provide for any sort of lip that I can seal with weather stripping. There is a small chance I may have to add a lip around the L-frame to extend it out a little further, which isn't the end of the world because it would act as a nice little rain gutter as well. We'll see...
• Really haven't decided where the gas struts are going to be mounted as there isn't a lot of options or room to mount them on the L channel.

More to come soon!

 

[The Artisan]

Looks like a lot of thermal bridging
Kevin

 

[Alphamacaroon]

Looks like a lot of thermal bridging
Kevin

Agreed it's not optimal (it's sort of the nature of the beast with these folding walls), but at the end of the day here I'm just trying to do better than the alternative— canvas. I'm by no means an expert in thermal dynamics, but my assumption is that this would have to be better than canvas when you figure in other aspects like thermal radiation, thermal retention, thermal mass, etc. But again, these are all just assumptions.

 

[The Artisan]

Agreed it's not optimal (it's sort of the nature of the beast with these folding walls), but at the end of the day here I'm just trying to do better than the alternative— canvas. I'm by no means an expert in thermal dynamics, but my assumption is that this would have to be better than canvas when you figure in other aspects like thermal radiation, thermal retention, thermal mass, etc. But again, these are all just assumptions.

Yours could actually have more condensation due to the steel. I have a patent on my hardsided poptopper topper and I make frp composite panels. Look into these panels no thermal bridging
Kevin

 

[Alphamacaroon]

Yours could actually have more condensation due to the steel. I have a patent on my hardsided poptopper topper and I make frp composite panels. Look into these panels no thermal bridging
Kevin

Where were you when I needed FRP panels (see previous posts)! 😂 The original goal was to use FRP panels, but I had no luck finding a reliable source for them in the sizes that I needed unless I ordered a huge amount in bulk (way more than I needed), so I ended up DIY.

But the issue here is not the panels (that part I've been able to reproduce pretty well with GoBoard), the issue is the edge finishing and joining pieces. I'm using aluminum (not steel), but I assume you use plastic of some sort? Do you, or do you know of a reliable source to get those non-metallic edge pieces? I would consider switching to them if I could find a good source, but I just couldn't.

 

[The Artisan]

Where were you when I needed FRP panels (see previous posts)! 😂 The original goal was to use FRP panels, but I had no luck finding a reliable source for them in the sizes that I needed unless I ordered a huge amount in bulk (way more than I needed), so I ended up DIY.

But the issue here is not the panels (that part I've been able to reproduce pretty well with GoBoard), the issue is the edge finishing and joining pieces. I'm using aluminum (not steel), but I assume you use plastic of some sort? Do you, or do you know of a reliable source to get those non-metallic edge pieces? I would consider switching to them if I could find a good source, but I just couldn't.

Never saw a post sorry, not on here to often. I actually use high density eps, xps or can use a pvc foam. I embed pvc inserts with perimeter edging then the new panels will get polyurea coated
Foam is sprayed with proprietary spray glue then roller pressed at 75psi
Kevin

 

[Cheapskate'sParadise]

Where can I find details on your FRP panel selection, shipping methods, factory pick-up option, etc? Your www.eztopper.com web presence appears to have been hacked or taken over.

 

[The Artisan]

Where can I find details on your FRP panel selection, shipping methods, factory pick-up option, etc? Your www.eztopper.com web presence appears to have been hacked or taken over.

All my domains are parked for future use. I am not ready to sell but feel free to send me a Pm and I can go over all the details and answer any questions or concerns
Kevin

 

[Alphamacaroon]

Was finally able to get some time to start working on the roof and get it connected to the folding walls. I'm happy to report that it folds and opens!

The most difficult part to getting this right is determining the length and positioning of the double hinges that connect the roof to the walls. My calculations in my cad program indicated that the hinges should be half the distance from the side wall to the front/back wall below the centerline of the front/back wall. Because that is a complicated description, here is a drawing:


That being said, it didn't really work out that way in real life (still not sure why) and ended up being closer to the center of the front/back walls. In the end I just kept opening and closing the roof and walls and kept measuring to find the point at which the hinge was the same length when it was opened as it was when it was closed.

As for the hinges I ended up cutting some leftover aluminum piano hinges I used for the side walls into 2" strips. Then I plug welded those hinges to some 2"x1/8" aluminum strips I cut to length. I was a little worried that the aluminum hinges might not be strong enough, but they seem to be plenty sturdy at the moment— only time will tell.

Next up I will need to figure out where I'm going to attach my gas struts and what amount of force they will need. The easiest way I could think to do this would be to put a crane scale on the roof section, crank it up, and read the weight. Luckily I had a fairly sturdy crane system in my garage that I formerly used to hang some kayaks. But first I was curious what the overall weight of the popup section might be, so I cranked it up until the whole frame was lifted off the ground.



The weight of the whole unit came out to 183 lbs. I think we could easily call it an even 200-220 lbs by the time the roof gets covered and insulated plus windows, hardware, etc. At first glance I was a little surprised at the weight, but then I started comparing it to the other options I've considered in the past.

Depending on the size, the AluCab ModCap tent is in the 308-359 lbs range (excluding mattress and canvas, no bedding), so I'm at least 100 lbs lighter or more.

Hiatus publishes a weight of 460-490 lbs for their mid-size truck camper. If you add the weight of my popup section plus the weight of my ModCap canopy at 176 lb, we end up with 376-396 lbs total for the unit.

In both cases I'm quite a bit lighter than the alternatives I explored in the past, so even if I do end up underestimating the additional weight that will be added by the time it's done, I think it's likely I won't be any heavier than those alternatives.

So now that I had a rough weight of the entire unit, I looked at the maximum weight required to lift the roof and wall sections.



This came out to a force needed to lift 84 lbs— let's call it an even 100 by the time the roof is covered. I'm smart enough to know that because of the direction the force is being applied and the non-linear nature of force in gas struts at different lengths, that I can't just take 100 lbs and divide it by 4. But that's about as far as my smarts go. I will likely have to leverage a calculator for gas struts as well as a lot of trial and error in mounting positions to get it right. Maybe someone with some specific knowledge can offer some advice here?

Because my frame is so low-profile, I don't really have a good way to attach struts without welding a bracket to it, so the ability for trial and error in the strut mounting positions is going be extremely difficult— I'm going to need to get creative.

It's funny because about 3 days ago I got so frustrated with the lack of some sort of t-slot mechanism in my frame, for adjustments and hardware mounting, etc., that I nearly decided to throw everything out and start over from scratch with a design based on 80/20 extrusions. But calmer heads prevailed and I realized it wasn't quite worth wasting the $1000+ I've spent on materials (at least yet). Which brings up another interesting tidbit— why didn't I start by designing the frame around off the shelf t-slot extruded aluminum like many other people do? The main reason I chose not to was primarily based on shipping costs. My frame is almost 10' long, and I didn't want to compromise strength by joining two pieces of 5' t-slot, so I really needed to order 10' lengths. Many of you may know that shipping anything over 6' in length generally adds astronomical costs because it usually means it has to be shipped via LTL (less-than-truckload) freight. So in the end I just couldn't stomach paying $1,000 in shipping for $1,000 worth of materials, so the idea was abandoned. But then I discovered something a few days ago— my local Grainger store will sell 10' lengths of t-slot extruded aluminum! The material costs are higher than most places online (typical Grainger), but because there are no shipping costs, the overall cost is MUCH more reasonable.

Anyway, I'm still committed to this design not only because it's nearing completion, but also because I think it will likely end up being much lighter than the t-slot. But now I have a possible option for a version 2.0 (if I ever get the courage to do it again).

Hopefully the next update will be a video of it opening and closing (with the assistance of gas struts) on it's own!