Saturday, March 23, 2024

Assembly Time!

More sanding and gluing. The door and surrounds. Glued the door frame to the walls. Found out later I made a mistake on the measurement. Door was too narrow. Forgot to add on the wall thickness. Lucky for me I was able to cut the excess off. 

More laminating. More tries with epoxy. More tries with glue. Right now, I've delaminated more than I've laminated. Decided to give up with both and stick to using paint.  Laminated the underside of the roof while it was flat on the floor. Figured it would be easier than upside down.

Moved the chassis to the garage and assembled the walls and roof on it. Finally it's starting to look like a caravan.  Glued the side walls to the floor. Going to hold out on the front wall and the roof until after some of the internal fit out is completed.  

Looking from the front towards the rear doorway. Roof is on to help stabilise the walls. 

Sunday, March 3, 2024


Doesn't feel like a lot was achieved this week. Other stuff happening, meant less time for the caravan build. A few stuff ups also sent me backwards.  

Lots of cutting foam when mistakes where made. The door was glued up. I cut and glued up the wheel well sections. I cut a lot of triangle sections to frame the corners as in the image below.  They'll be glued in today and then given a light sanding in preparation for the fabric coating.

Sunday, February 25, 2024

Squaring Off

An exciting week. I gave up bashing my head trying to square off the panels. The 1200x600 XPS panels when I started weren't very square. I should have squared them all before joining them together. But it seemed a good idea to leave that until later. Now, being later, I wish I hadn't. Trying to square up the full panels was a lot harder than I thought it would be. After countless tries, with string, straight edges and not so straight edges, I gave up and asked for help.

Tom arrived with his van. We loaded it all up and took it to the Men's Shed. The plan was to use the table saw to trim off the edges. No edge being straight stopped that idea. We ended up clamping a foam panel to an MDF panel set up on a table. Line up two edges of the foam at a corner of the MDF. They had to be some overlap, as the edges weren't straight or square. Check that too much foam was not going to be removed. Then I then sanded the two sides to match the MDF panel edges. I used a right angle to check the edges as I sanded. Done! Two edges (more or less) straight and at 90 degrees to each other. Undo the clamps, move the foam, line up one of the now straight edges with an edge of the MDF. Use the a tape measure to check the dimensions. (The walls needed to be the same height. The roof needed to be 960mm wide). Clamp. Sand the edge that isn't straight to match the MDF. Unclamp, move and get the last edge lined up. Clamp. Sand. Quicker to describe than to do. Several hours of sanding to get it all done. Tom then dropped me and the foam back home again. Thank you Tom!

I did another epoxy test this week. A small test piece. I used a paint brush rather than a scraper to spread the epoxy about. This test went a lot better. For one side of a 1 sqm piece of foam, the added fabric and epoxy  weight would be 280g. I also did a test with PVA glue, that was right on 200g. Both are acceptable. Using a roller or scraper might get the epoxy weight lower. 

PVA glue is so much easier to use.

Sunday, February 18, 2024

Door Locks and Epoxy

Epoxy doesn't mix with locks.

I started the first epoxy pour on the front panel, but wasn't happy with how it turned out. The weight was higher than planned.

The fabric overlapped the edges so I could trim it later. Pulling on this, I was able to peel the epoxy impregnated fabric off.

It only pulled a small amount of foam off. Checking the weight, I was right. The epoxy impregnated fabric weighed 535g. So I was right with 100g fabric and about 440g epoxy.  Way too much epoxy.

The 1200x960mm (1.152m²) piece of foam with some epoxy still on it is 1200g. I weighed some spare pieces and 1m² of foam weighs 1.027kg. This is heavier than the 900g I was calculating on, so the panel should weigh 1184g. There is a little epoxy in the join and on the edges where the fabric wasn't.

Need to do more epoxy testing. I'm reluctant though. Thinking to change to using glue and paint only. Thinking about it. I started some test pieces. It's much easier to use. Still deciding how I'll go forward with that. I'll get the foam pieces squared off first, then coat them. This will give me more time to decide.

I cleaned up the chassis, support legs and drawbar removing rough edges. These were on the inside of the tubes.  I used rags to clean out any aluminium filings.  Also marked up the support legs to cut the adjustment slot. Need to wait for a teacher on that. They'll show me how to safely use the lathe or milling machine.

The door locks I had ordered ended up being a "captured key" type. These are for mailboxes, or cupboards where you put the key in, open the lock, but can't remove the key until you close and lock it again. Easy, I'll just drill a hole in the right place to let the key out. It worked!

Until I taped the lock. Small brass pins fell out. Locks aren't meant to do that: drop their innards out.  The lock jammed up.  As I had two locks, I decided to try drilling between the pins. But that didn't work either. Pins still fell out. Two locks stuffed. 

Saturday, February 10, 2024

First Epoxy Pour! Is it the last?

Doesn't look much, but it's the first panel to be laminated on one side with fabric and epoxy. I've been thinking and mildly stressing about it for a while. 

I was nervous mixing and applying. Worrying about the ratios and measuring them accurately. The "clock is ticking until it goes off" from the start of mixing makes it feel like it's a rush. Don't delay. But measure and mix well. I mixed two batches. I didn't want too long a gap between the batches in case the first poured onto the fabric started setting before I could finish.

It's easier to coat the foam, place the fabric over and then add more epoxy to the top. I did this at first, but once I had started, I  didn't have enough hands to keep the clean fabric off the coated fabric. So I lay all the fabric down and poured the epoxy on top. Much harder to get even coverage. I was getting dry spots. I could force the epoxy through from the top, but it's more time and work. The clock is still ticking. I used a plastic scraper to move the epoxy about and push it through the fabric. Used it like a squeegee to spread the resin out as far as possible.

Start to finish took an hour and used about 440ml of epoxy for about 1m². 

The epoxy is mixed by volume. Very inconvenient. I wanted to calculate by weight as using a scale is easier than eyeballing clear liquid into measuring containers. 

I got a packet of 250ml and 350ml(?) paper cups. Wooden knives held by the blade with the round end of the handle cut off square (to get into the corners) were used as stirrers and scrapers.  I used water and a scale before hand to mark 20ml increments on the out side of a 250ml paper cup. Then transferred the measurements to the rest with a ruler. 

With a light positioned above the cup, you can see the liquid level as a shadow on the outside to mark it read measurements. 

I poured 80ml into a cup, weighed that, then poured it into the larger cup, scraping out as much as I could with a knife scraper. 3g remained in the cup. Poured another 80ml and emptied it into the large cup. 3ml remained behind. That's 2x part A. Using a new cup and knife scraper, measured 80ml of part B and poured it into the large cup. Again 3ml remained behind. 

By the weights, that would be 87+87=174g Part A with 77g Part B. Total weight 251g

(For the second batch I used only the large cup and measured 90+90=180g part A, 80g part B. Total weight 260g.)

On pouring part B into A, I started a timer and using a new knife stirrer, started stirring for two minutes. Then scrapped the edges and bottom and mixed for another two minutes. Called it ready. That's 4 or 5 minutes of the 30 minute working time gone.

Total weight of the two batches: 511g. Not all was used on the fabric, but at least 400g was. 

That is way more than I thought it would be. 100gsm fabric, I was working on about the same weight or maybe double, of epoxy. Did I apply it too thick or did the fabric soak up when I was forcing it through? The fabric is 80% polyester and 20% cotton. 

I'll have to think about this. Besides the increased weight, I'll need a lot more epoxy. The epoxy was originally purchased to use as a glue for the foam, and as a bonus, in the smallest volume I got, seemed enough to coat the panels as well. I didn't end up using it for gluing, as a one part polyurethane glue was easier to use. 

Not sure the epoxy it's worth it. I will still need to paint the epoxy to protect it from UV. It might be better to simplify and skip the epoxy and just use paint and the fabric: also known as "Poor Man's Fibreglass". 

Wednesday, January 31, 2024

The Rational for a Bicycle Caravan Build

I would need a trailer to have enough surface area for sufficient solar panels. I thought of mounting a tool box on a trailer and then attaching a solar panel on the lid.

Problem. The size of solar panels. 100 watt solar panels are about 1 metre long. To get higher output, the size increases to about 1.5 to 1.6 metres. I wanted more than 100 watts. My tent is 1.9 metres long. If I was going to have the length about 1.5m, I might as well go longer so I could sleep on it.

I like sleeping in my tent, but finding a test site is hard. It has to be reasonably flat, no rocks, roots, prickles, grass clumps, dips, water, etc. A trailer has its downsides on the size of it, but it would be an advantage to sleep on top of it and be above all the ground problems.

I spent weeks looking at different designs from western wagons, fold out and pop top trailers, and caravans. Drawing up paper plans and examining how to build them, and the weight, and how they would work day to day. The size to tow behind a bicycle and sleep in or on it added to the challenge. Every decision has consequences and trade offs. Size, weight and cost.

The solar panel on the roof, so I'd have to sleep under it, or have it moved out of the way to sleep where it was mounted. I did consider sleeping on top of it, but couldn't get a working idea. If to move it out of the way, how and where to put it.

Ideally, I'd sleep low down, not very high off the ground for stability. One set of wheels near the middle with a metre on either side doesn't allow a lot of ground clearance going up inclines. I'm using 20" wheels. Can add more wheels, but that increases the weight. Removable wheels and having the trailer sit on the ground is possible, but I decided against that. Without single sided axle wheels, it would be inconvenient to remove and replace the wheels daily. To sleep low, it is between the wheels on the floor. Wheels axles need support. Wheel is 100mm wide at the hub, 25mm for the supports. That is 300mm of the width just for the wheel spacing. Wheelchair wheel hubs are only supported on one side, but this only saves 50mm for significantly increased wheel costs. Ultralight sleeping mats are 520mm wide, but more comfortable is 600mm. Already the trailer is 900mm wide. I'd like the trailer to be thinner, but 600mm for the bed needs a bit extra for movement, say 100mm each side, 800mm is the lowest width that I was happy with. The width of my tent interior. This is without considering the wall thickness or...

The height. Too tall and skinny and the trailer will tip easily. I liked the western wagon design as it allowed the canvas to be raised letting the wind blow through.

A width of 800mm has the wheelbase in contact with the ground at 700mm. 20" wheel axles are 260mm of the ground. The floor would be above that. To sit up in bed needs a minimum of 950mm height. This totals 1210, but ignores the floor, bed and roof thickness. The axle mounts add a bit of height as well. Don't stretch up or move upwards without ducking the head.

I really liked the western wagon design, but settled on a more conventional caravan look. Flat roof for the solar panel. The walls would be 30mm thick laminated foam panels. Plugging this into the constraints, the caravan ends up:

Width: 960mm
Height: 1500mm
Length: 2200mm (Not including the drawbar and hitch)

Width: 900mm
Height: 1200mm
Length: 2160mm

The ground height ends up at 300mm to the top of the floor inside, and 1500mm to the top of the roof.

Western wagon example But my design had two wheels only. No sheep.

Folding bicycle caravans A lot of different folding and opening options.

Peter Petersen The one that I settled on for inspiration.