2017-06-11: Research, planning and insulation

Something of a slow grind since we got back from our first trip. We’ve both been very busy with work, so not much time to spend on the van.

Amy has been insulating the rear and side doors. Since these cavities hold loose wires that connect to the central locking and door catches, we don’t want to install insulation that can’t be removed if we need to fix any problems. So we’re using left over closed cell foam sheets (about an inch thick) which can be friction fitted without using any glue or expanding foam.

I’ve been drawing more layouts in Sketchup, trying to iron out all the little niggles, and figure out what we can pin down now so we can continue the build. It’s a constant struggle between getting stuff done, so we can test whether it does work, and planning things out, so we know that it will work.

 

Current draft layout. Yes, I know it doesn’t conform to the laws of physics. It will.

At this stage, while we’re trying to maintain maximum flexibility, that means a lot of shifting sand.

So we’re trying to make some decisions on the electrical system:

  • What battery technology to use
  • How much capacity we need
  • How much solar we need
  • What arrangement of panels will work best on the roof (in combination with other components like a fan or a rooflight)
  • How to run wiring through the van
  • How to charge the battery off the alternator, and what system will work for our van (voltage sensitive relay, or battery-to-battery charger)

Sizing batteries and solar panels

One of the first steps in planning the electrical system is figuring out what size battery and solar panels we need.

That depends on a few key factors, which will vary for everyone. In our case, they are:

  • Price: we are price-sensitive!
  • Level of luxury / number of appliances: we don’t want a TV, microwave, Air-condioning, hot water, etc. So our electricity needs are quite modest
  • Dependence on electricity: at the moment, we’d like to mix our fuel usage, so gas will be a big part of the mix: mostly for cooking and heating
  • How close to civilisation: we want to go wild, not stay in campsites with hookup power. That means we want to go a long time on just the battery and solar power.

Continue reading “Sizing batteries and solar panels”

Wood selection for framing and cladding: do the math

I’m evaluating different materials for cladding the walls of the van, and for building frames and panels for furniture (bed, kitchen units, etc.)

Commercial outfitters here in the UK use materials I find unappealing, whereas DIY convertors often stick to what they can find in the out-of-town DIY store. I’d like to weigh up – literally – the pros and cons of a few approaches that are in scope for me.

Absolute weights

Weight is a key factor, not least because of the payload limit of the van. But also efficiency, handling and sizing. I consulted a few sources to find out the weight of different wood types. The excellent Collins Complete Woodworker’s Manual gives ‘average dried weight’ for a range of hard and soft woods. (This is just a selection of woods that are available to me, and might be appropriate.)

Soft woods

  • Sitka and Norway spruce — 450 kg/m3
  • Pines (White, Ponderosa, Yellow) — 420 – 480 kg/m3

To verify, I weighed some 44mm square batons I bought from Wickes (the same product is also available at B&Q). It’s usually labelled as ‘whitewood’ or  spruce. It worked out at 423 kg/m3.

Hard woods

  • European beech — 720 kg/m3
  • American white ash — 670 kg/m3
  • American white oak — 770 kg/m3

Plywood

My local timber merchant also stocks lovely BB Grade Birch Plywood, and they gave me the specs for a couple of thicknesses:

  • 12 mm 8×4 sheet — 25.25kg (707 kg/m3)
  • 9 mm 8×4 sheet — 19.50kg (728 kg/m3)
  • 6 mm — extrapolated: 749 kg/m3
  • 18 mm — extrapolated: 665 kg/m3

These are the woods and panel materials that are available to me (discounting the crap I don’t want to touch).

Wall cladding

Many DIYers seem to go for either cheap plywood faced with car felt, or wooden cladding boards, made from spruce or maybe pine.

I like a wooden finish, but those cladding boards are either thin or heavy. Here’s a typical review of some 8mm spruce cladding (just labelled ‘softwood’) from a DIY store:

At least 20% of these poor quality timbers where so warped, bent or sub standard that they could not be used for the project. They are only finish sanded on one side witch means that you cant switch boards around to hide knots and holes where knots where.

Large chunks where often taken out of the tounges or groves making them incredibly hard to fit together. Every single piece is labled with an incredibly sticky label that is impossible to peel off on the face side of the board making for a enfuriating few hours of peeling and scrubbing.

This chimes with my experience too. You could go for thicker boards, but then you’re looking at some serious weight. To clad an 8′ x 4′ area with 14 mm softwood cladding would weigh about 18.8 kg. The same area in 6 mm birch ply (which has a lovely finish) would weigh about 13.4 kg.

There are other factors of course, (how well does the cladding conform to the curves of the van, does it need to bear weight or hold a screw), but the weight and aesthetics certainly point to the thin 6 mm ply as a good option.

Furniture framing

I’ve made lots of furniture out of stud timbers and that 44mm section whitewood. It’s fine, and in certain orientations and thicknesses, adequately strong.

But I’m interested in using something that cuts more cleanly, is stronger and has some flex for the construction of cabinet and bed frames. Ash looks promising here. I need to do some practical experiments – and more research, but the weight difference doesn’t look too bad, especially when you consider you could get away with smaller cross-sections of wood for many applications in the van.