January 23, 2015

Canvas oilcloth overmitts sealed with beef fat, beeswax, and linseed oil

I commute by bicycle 36km roundtrip to work most days, year round. Being in New England, some specialized gear is called for in the winter months. With a good layering system, carbide spiked ice tires, and a sanguine attitude, the hour or so it takes me each way is almost reasonable. It is nice to get some fresh air, have time to think, and it is my only form of exercise.

One key element to the winter ensemble is overmitts. For the past 10 years or so I've been using some gore-tex ones Becky bought long ago for bike commuting. Overmitts are great, because you can put them over light gloves when it is not that cold, or over heavy mitts when conditions are frigid. They typically have a long gauntlet section that can lap up over the jacket sleeve to keep wind out. These ones were roomy enough that in very cold weather I could work my thumbs up out of the thumb holes and keep them in the same compartments as my other fingers to keep them warm, while riding. All in all, very satisfactory.

Unfortunately as the weather got colder late this fall, I could not find the overmitts anywhere. Arrgh! Being at the end of the third year last fall of the No Buying Clothes challenge, this was a serious problem since I didn't just want to purchase a new set from Amazon like a normal person. 

I've often wondered how people managed in fierce outdoor conditions before gore-tex. Probably early on, one had furs rubbed on the flesh side with fat. I did think about how a pair of overmitts fashioned from a couple of home-tanned neighborhood squirrel hides would be cozy, not to mention a good conversation starter. But they city doesn't approve of trapping wildlife, I might get blood thrown on me by PETA activists, and anyway with the tanning and everything it seemed a big project to take on when what I really needed was some mittens to protect me from the rapidly plummeting temperatures.

I remember as a teenager doing some experiments using urine and brains to tan the hides of jackrabbits my mom and I shot in the dessert. I can't recall the details, but I do remember it didn't turn out all that well. That was before the internet; I'm sure the process could be developed much more efficiently now that I could just google "tan squirrel hides with brains and pee"!

Anyhow, looking at more recent times but before the polymer materials revolution of the mid and late 20th century, oilcloth or tincloth was a popular material for outerwear. This is a heavy cotton fabric, impregnated with sealants to begin with and occasionally recoated as needed. There are many recipes for sealants, but a common thread is a mixture of linseed oil and beeswax. Sometimes pine tar or other ingredients are called for.

I decided to give this a go since I could make it with materials and tools I already had on hand. To begin, Child 3 and I pulled out some cotton canvas from the fabric stash and pressed it.

 I traced around my fleece inner mitts as a starting point for a pattern, and we sewed up a test mitt with a french seam.

This mitt ended up too small, and the french seam created an annoying crumpled ridge when turned to the inside. For rev 2, the pattern was expanded and sewn with a plain seam.

These won't be laundered often (ever?), and they were to be gooped up with wax, so fraying of the seam allowance didn't seem like such a danger. Rev 2 looked like it was approaching usefulness.

To help contain potential fraying, and enhance waterproofness at the seams, I tried to fold the seam allowance to one side and stitch a length of silk ribbon over it. The serger finished edge visible here is a remnant from when I used to have a serger. I did the edges of the canvas before washing it, before it went into my stash.

This ribbon idea was not executed perfectly, but I figured it would do for a prototype. 

Concerned about gripping of handlebars, I applied some rug gripper compound to the palm and inner face of the fingerbox area. Now that I've used them a fair bit, I don't think this was actually necessary for use on the bicycle. Might help with gripping of the snow shovel handle though.

After the rubber was set, I mixed up a small amount of sealant. I decided to use mostly beeswax and linseed oil, and to throw in some beef tallow that Becky had skimmed off a pot of beef stock she had made recently.

Plus some orange oil for smell. I bought a liter of it years ago when we had a cat, to try and keep it off a couch, which didn't work all that well. Still trying to use up that bottle somehow.

  • 40g beeswax
  • 40g linseed oil
  • 10g beef fat
  • 10g orange oil
I heated it up in a beaker over a low flame, with a foil cap.

When fully melted, I painted it on to the canvas.

Next, I melted it in with a heat gun. The one on the left has been heat gunned in, the one on the right is as-painted.

After this, the fabric was very yellow and stiff, and pretty stinky (from the linseed oil I think, though the overtone of bitter orange didn't help any). I hung them up in the bathroom for the weekend.

Over a few weeks, the fabric became more soft, less yellow, and less stinky. The sealant really seemed to sink into the fabric.

I've not yet worn them in a real downpour, but they have weathered plenty of freezing drizzle and temps as low as -22C (-9F). They are working great. Not quite as waterproof as the gore-tex ones were, but perhaps they need a second coat of sealant. This pair is starting to look a little grubby after months of service. Using darker color fabric next time would help. Maybe I'll hand wash them in soap, let dry, and reseal once a year.

For rev 3, I would definitely adjust the pattern a bit. The main improvement would be to shift the position of the thumb to be wholly in the palm side pattern piece, rather than split at the middle. The outline of the finger box and the thumbhole need some tweaking. And I think a bit more flare in the gauntlet would aid in donning and doffing.

Overall this is a viable technique for outerwear. I've read that in some situations, oilcloth is still preferred over gore-tex because it can be far more durable. Like in the timber industry in the pacific northwest for instance.

Maybe when my current pair of gaiters wears out I'll make some oilcloth ones. Or even overpants or a jacket. But I'm going to milk my gore-tex garments along as far as I can, since I've got no shortage of  other pressing sewing projects to work on.

January 6, 2015

CNC cut Espalier Apple Trellis

One of the central elements that persisted throughout our many iterations of designs for the back yard was apple trees espaliered on the back fence. Having expended a lot of money and time to finally arrive at 7 baby apple trees planted in a strip of soil behind a retaining wall, positioned in front of a hopefully long lasting fence, it was time to build a trellis to train them along.

Past time, actually. I didn't reach a point where I could get the trellis done until late summer. By then, some of the shoots coming off the trees were going in an undesirable direction, and the leaders were not growing ramrod straight as I had drawn them in my CAD orchard design. Weird, right? I can't believe the trees didn't pay more attention to my drawing. Some of them even had the nerve to not sprout limbs in the right places at all for my design. I'll have to speak to them about that during their next performance review (coming up in the spring, when I'll have my grafting knife in hand...).

I spent plenty of hours while commuting on the bikepath or laying in bed at night thinking about how to build the trellis to economize on expensive materials, be relatively quick and easy to put up, and be strong enough to do the job while looking elegant and fabulous. I designed this trellis to be based around 8 upright standards: 2 ends, plus one between each pair of trees.

The profile for the support brackets was mostly done in Inkscape. The profiles were sized to put the cables about 300mm out from the fence, and such that two brackets would nest well in the 240mm wide boards I had bought for the purpose.

I eventually got the CNC router to the point where it could do a real project, and this was the first one. The inkscape file was brought into Pycam and fiddled for a good many iterations.

Once I was happy with things, I cut out 32 of these pieces. I needed 8 supports, each with two brackets, each bracket being formed from two bracket profiles. For clamping stock during cutting, I just used screws and washers down into the plywood table of the machine.

Since then, I figured out how to do support tabs in Pycam, but at the time I just tried to set the home for the Z axis so it would leave the parts lightly connected to the rest of the stock, then crack them out and sand the edges later. This proved to be moderately successful, but the red cedar did tend to sometimes peel back grain from within the outline of the part when I was freeing it from the waste.

I hadn't exactly decided on where the screw holes were going to be or for what size screws, so they didn't get cut on the CNC. Easy enough to add after the fact.

Some extra 25mm thick wood was used to make filler pieces for the sandwich of each bracket. For assembly,  I used west systems epoxy and stainless screws. When the epoxy was set, I used a 3mm roundover bit in the router to ease the exterior edges of each assembly, then sanded them all with a palm sander. I also rounded over selected edges of the two vertical members.

Aluminum bar stock from Onlinemetals was cut and drilled to act as a big washer to hold the bracket to the vertical standard and the fence behind it.

The wood elements are all made from clear red cedar, which I ordered along with all the wood to make the fence panels. The vertical member which actually holds the cables and the longer vertical piece that is screwed to the fence are both made from 25mm wood, while the supports which stretch between those elements are robotically cut from 19mm stock. I used aluminum bar stock to clamp the cables.

Each vertical trellis support was put together and then screwed to the fence with stainless lags. I put screws in specifically where the cross rails of the fence panels run, plus a few other places to keep things flat. I ended up flipping the support brackets around from the original design in order to get the top cable up higher.

I tested each one by hanging with my full 80+kg mass from the top bracket, though I didn't really try to break it by bouncing. I figure if an adult should try to climb the trellis it would be nice if it could withstand the experience. Hopefully I have accomplished that here, but I can't help but worry that maybe I should have made it a bit stronger.

The horizontal tree supporting elements are 7x7 strand 3.1mm 316 stainless steel cables from ebay, and there are 5 of them, to provide 5 rungs of limbs on the espaliered trees. About the best looking reasonable cost end fittings I could come up with were from SC&R, and I ordered a hydraulic crimper and sufficient fittings for the job.

This might seem like a gratuitous investment for putting up five pieces of cable, and I'm sure my wife would agree! But I do plan on making a number of other cable trellises around the place, and I can always sell it when I am done (though I probably won't, if we are being honest). The other obvious choice would have been big thimbles to double the cable back at the ends and direct it into screw or crimp clamps. The crimper for that wouldn't be that much cheaper though, and the screw clamps didn't appeal to my sense of style. Plus, even wrapping the cable around the radius of a typical thimble compromises the strength significantly and I would have needed slightly more complicated hardware at each termination. If you go by the specs of the arrangement I ended up using, the assembled cables can each take up to 1000kg tensile load. I'm still not convinced this is high enough and probably something would fail below that load anyway, but it may be enough.

The brackets have little strength laterally, so to withstand the tensile load from the cables at the terminal braces, I made up and installed stainless straps at each cable end. These are 1.9mm thick, 25mm wide, and 43cm long 304 stainless, ordered precut from OnlineMetals. I drilled and bent them at work one day after hours.

Each strap acts as a washer for the crimped on M6 threaded fitting at the end of each cable. The other side of each strap is screwed to the terminal fence post with two stainless lag screws.

So when all five cables are in it looks like this.

Of course this will introduce a torque on the fence post, which is a bit concerning, but I'm hoping it will be ok. The post is braced against this torque in a few ways:

  • Through bolted aluminum plate in front and channel behind (this transfers the torque to the concrete though, which is not the ideal type of stress to put on concrete...)
  • Pins of the back fence panel mortised in on one side
  • Future side fence panels (would replace the diagonal brace visible below)

I couldn't quite decide whether the cable should be clamped at each vertical support, or allowed to slip a bit to accommodate thermal expansion or other stress. In the end I decided it was too much trouble to make 40 really secure cable clamps, so I did something easy which sort of lightly clamps the cable at each crossing point. There are two stainless screws on each side of every cable crossing in the vertical aluminum bar clamps; these push the cable into a square slot in the wood member.

The trellis was put up while most of the huge Hope Black Dye sunflowers I grew in the micro-orchard bed this year were still standing, which made things a little more challenging.

Once the trellis was entirely erected, Child 3 and I went around and strapped bamboo canes and corresponding tree limbs to the cables.

This made it more obvious how I should have done my dormant pruning after planting differently... ah well live and learn. The trees look cute strapped to their forms. I hope they grow more next season.

So now we are in good shape to get the espaliers under better training next year.