Glueing silnylon fabric versus sewing

I am planning to sew my own tent, and have purchased some very thin silnylon fabric for that purpose:

https://www.adventurexpert.com/product/10d-silnylon-fabric/

...yep, all the way from Slovenia, as couldn't source it in Australia. Remarkably, it only took a week, shipped by DHL.

This is 10D (denier) fabric, very thin, and coated both sides with silicone so also very slippery. Extremely difficult to sew, so when I watched this video on glueing silnylon, was most intrigued:

https://www.youtube.com/watch?v=_5yGxdJveZk

A snaphot from that video, showing trying to pull the glued pieces apart:

...he was unable to pull the two pieces apart.

In previous work with constructing solar water distillers, I determined that silicone sealant bonds very strongly to existing silicone sealant, so it looks promising bonding two silicone-coated fabrics together. This I had to try!

I also have a piece of ripstop nylon from Spotlight:

https://www.spotlightstores.com/sold-by-the-metre/plain-148-cm-ripstop-nylon-fabric/BP80070051002

...doesn't say that it is coated with anything, so presume not.

The silicone adhesive that the author of that video used, is expensive, but in the comments there is another one mentioned, that is, a flowable silicone sealant, Permatex Windshield and Glass sealant 81730, which is available locally, from Repco. So bought a 42g tube of that.

Experimented with both fabrics, silnylon to silnylon, and silnylon to ripstop, left 24 hours, then did the pulling test. Here is a photo of the ripstop glued to the silnylon:

Yes, a very strong bond. HOWEVER, if I grab the two pieces separately, at the ends, then they can be very easily pulled apart.

What this means is that the strength is longitudinal only. Would "longitudinal" be the correct word? Anyway, if there is any weakness at the join, a tear can start and will rapidly spread.

I found that the ripstop teared off more easily.

I then repeated the experiment with Selleys acetic-cure 401 RTV silicone sealant, this stuff:

https://www.bunnings.com.au/selleys-310g-401-rtv-engineering-grade-silicone_p1231042

Did not thin it, just spread it fairly thinly, left for 24 hours.

Same thing, it tears apart quite easily. However, the silnylon to silnylon is a noticeably stronger bond (compared to the Permatex sealant), almost to the point where I might trust it to construct a tarp. But still, once a tear starts, the tent will fall apart in strong wind.

There is one area where I think glueing is a good idea, at tie-out reinforcements, as this guy does:

https://www.youtube.com/watch?v=Ec8YhQffRj8

...the glueing could be done carefully so that there is no weak point where a tear could start.

So, conclusion is that I will still sew the tent, but consider glueing tie-outs.  

Tags: light

Test SLAR 5W 5V solar panel

Continuing the saga of testing these little photovoltaic solar panels, here is the previous test:

https://bkhome.org/news/202104/accurate-test-of-claite-10w-5v-solar-panel.html

I came across one on Aliexpress that is sold with or without the USB 5V regulator, so I bought the one without:

https://www.aliexpress.com/item/1005002251904094.html

It has a slightly thicker substrate than previous ones tested, so is more rigid. Weight is 90g. Brand name is "SLAR".

Today is Friday, May 7, 2021, and I setup the panel outside at 10.00am. Measured solar intensity at 810W/m2, ambient temperature 22 degC, blue sky, no clouds, slight breeze.

Got the measurements started at 10.15am, finished at 10.20am. Then again measured solar intensity, 820W/m2. The cell temperature, IR detector held about 50mm from surface, 46.5 degC.

Here is the plot:

The peak power point is about 4.8V @ 0.7A, which is 3.36W. Well well, this vendor is being honest, in contrast with other recent purchases. This is mid-morning on a winter day, sun low in the sky, so expect more power at midday, and in the summer.

That voltage-current curve has a very sharp knee, then rapid drop-off. This would indicate high quality cells.  

Tags: light

Bottle cap glued to portable bidet

I have posted about a "portable bidet" to use when hiking:

https://bkhome.org/news/202103/portable-bidet-for-hikers.html

It works, however there was one incident. Too enthusiastically squeezing the bottle, the bidet popped off and fell into the toilet bowl.

Someone did ask on the Aussie hiking forum, why can't you buy these with screw-on threads?

Interesting question. I followed that one up, and purchased three different bidets that come with small squeeze bottles. These all have screw-on caps. They work OK, however for hiking I want the cap size to be "28mm diameter", for compatibility with Coca Cola and many other soft plastic bottles available in shops. Those three all had larger diameter caps.

So, solution is to glue a cap on, which I did today:

...problem solved!

That cap is from one of these "BONLOX" folding TPU bottles:

https://www.aliexpress.com/item/33012014287.html

These have a 28mm screw thread, and it is pretty much the same thread as on a Coca Cola bottle, and the thread also screws OK onto the Sawyer Mini water filter.

There are a lot of these foldable TPU bottles for sale on eBay and Aliexpress, and if you are wanting to buy one, do not buy the "AONIJIE" brand -- these are 28mm but the thread is weird and the Sawyer Mini will not screw onto it. I also have another brand of water filter that will also not screw onto it.

I have tested "BONLOX" and "LIXADA" TPU folding bottles, their threads are OK.

Now for usage...

My new portable bidet can be screwed onto any (?) soft-drink bottle, including these TPU folding ones. However, I found that the 500ml TPU bottle is a bit too floppy. So have ordered the 250ml size, see if that feels better when held upside down in one hand.

Practically, a small plastic Coke bottle is good. With the TPU bottle, water starts coming out as soon as you upend the bottle -- which you could get used to I think.

These TPU bottles are great for hiking, as they are extremely light weight and fold up very small. That "BONLOX" 500ml only weighs 19g without the cap, and the cap is 13g.

So I could just use the 250ml TPU bottle for use with the bidet, sans cap. Hardly adds any weight to the backpack. Could put a Coke bottle cap on it, so as to keep the air out when rolled up -- those Coke caps weigh less than 1gm.

One technical detail: I used "plastic glue" from Bunnings. There are a couple of different brands. They are a super-glue with a separate primer stick. They will glue any types of plastic together. And being a super-glue, it grips immediately, so you have to get the position exactly right the first time -- as I found when tried to slide it slightly and it wouldn't -- but still turned out OK.

So it is looking like the hiking kit will have this new portable bidet, and probably the 250ml TPU bottle (sans cap).  

Tags: light

The best double-wall trekking pole tent

The title is really a question rather than a statement. for those who hike with trekking poles, this tent, two poles required, is looking like the best of the best:

https://durstongear.com/product/x-mid-1p

It is the Durston X-Mid, in 1P and 2P versions. Dan Durstan is a young fellow, who reconsidered the design of trekking pole tents from first principles, and came up with this design.

I first got interested in it from this thread in one of the Australian hiking forums (and Dan has also posted to this thread):

https://bushwalk.com/forum/viewtopic.php?f=15&t=28132

I don't know where it is manufactured, I would guess China, from the fairly low price. Dan gets a new lot in, and they are all sold just about straight away.

What really intrigues me is, having put up many tents with a gazillion stakes and guy lines, the ease of erection of the X-Mid. See video:

https://www.youtube.com/watch?v=U9vOLs12KQE

It is a rectangle, only requires four stakes, then you insert the two poles. Layout of the 1P:

A lesson here, a clever young person can still come up with something new and innovative.

Negative points? Well, it does require a larger flat area than most other trekking pole tents. And I don't hike with trekking poles!   

Tags: light

Wood frame for Aricxi tarp tent

I posted about erecting the Aricxi tarp tent in my back yard:

https://bkhome.org/news/202103/aricxi-tarp-erection-test.html

The tarp is 15D silnylon and just over 300g. I like it, but the inner mesh bivi that it came with is tiny, and also very awkward to get in and out of when underneath the tarp.

I purchased both together, but Aricxi also sell them separately.

Forever seeking that "perfect tent", a new project has commenced. I decided to use the Aricxi tarp as the starting point, and sew my own mesh inner tent. I have a sewing machine, and can sew, just barely. So this will be an interesting experience -- will be sewing 10D silnylon, silicone-coated both sides, so incredibly thin and slippery. Will also be sewing thin no-see-um nylon mesh.

Did some planning with SpaceSolver, however, ran into limitations with the 3D modelling. Decided that it would be good to erect the tarp and then take measurements on the real thing. This is like a dressmaker's dummy, except I am doing it with the tarp.

Today, bought three 30x15x2700mm painted pine from Bunnings, and built this:

Setup inside, can drape the tarp over it The frame is 123cm high at the front, 55.5cm high at the back, and that ridge piece is 221.5cm long.

So, will be able to work on this project inside, out of the weather. Now impatiently waiting for the 10D silnylon to arrive from China. Very difficult to source this lightweight fabric. Want nylon with silicone coating both sides -- not the breathable kind, waterproof. There are vendors in the USA and the UK, but China is the main source. alibaba.com is one place where the manufacturer's sell their goods, and they even sell small samples, but need to be a registered business to register with alibaba.com. However, I found one vendor on aliexpress.com, ordered from them.  

Tags: light

Accurate test of CLAITE 10W 5V solar panel

I tested the panel recently, and got a strangely-large short-circuit current:

https://bkhome.org/news/202104/comparison-of-claite-10w-and-se05-5w-solar-panels.html

I have had this anomaly before. What is happening is that the pulses from the switching regulator are confusing the digital multimeter. At the higher load, the output filtering capacitor is not smoothing the pulses as effectively, and the pulses are upsetting the multimeter. So that over-2A short-circuit current is wrong.

Today was sunny, at least in the morning, and tested the panel with the switching regulator removed, directly connected to resistance loads. Today is April 14, 2021, Perth Western Australia, bright blue Autumn sky. Test conducted from 10.45am to 10.50am.

Solar irradiance (intensity) measured at start was 870W/m2, at end 880W/m2. Ambient temperature was 24degC. Negligible breeze.

The panel was sitting in the sun about 5 minutes prior to testing. About midway through the test, took a reading of the temperature at front of panel, IR reader held about 100mm away, reading was 47degC.

Here are the readings, and a plot:

I estimate peak power point is about 4.8V @ 0.84A, which is 4.05W.

So, if you reckon the vendors are cheats, advertising the panel as 10 watts, you would be right.

Note however, that they are claiming 10W with a cell temperature of 25degC and solar irradiance of 1000W/m2. Power output drops as temperature rises, and if I guess -0.3% per degC rise, then the rise from 25degC to 47degC will cause a power loss of 7%.

Then there is the irradiance. If I assume power output will climb linearly with increase of irradiance, then that 4.05W would become 4.6W. Then factor in the cell temperature, and we get the power output at 1000W/m2 irradiance and 25degC as 4.97W.

Just about half what the vendor claims!

It does make it hard for those vendors on eBay and Aliexpress that do the right thing and publish correct power output.  

However, they are good photovoltaic cells, more efficient than those in my SE05 panel. So the panel is a good choice for hiking, where we are chasing lighter weight.

What the vendor does not say, is what coating is used on top of the cells. As I understand it, the cheapest is epoxy-resin, then there is PET, then better still ETFE. The cheap option, the coating will perish in the sun, whereas ETFE will give you 10 years lifetime (I think, from memory).

For someone who will take the panel hiking, perhaps perched on top of their backpack, it probably won't matter what coating is used, as hikers are only going to be out there occasionally.

However, something to think about is the switching regulator. That will be sitting on top of your backpack, right near your head. It oscillates at about 300KHz and radiates much higher frequency components. It is, effectively, a radio transmitter.

There you are, out in the pristine wilderness, living a natural life. yet you have this thing on your backpack radiating RF into your head!

It might not be doing any harm, but for me it really does not fit with being back to nature. That is one of the reasons that I intend to replace the regulator with a linear regulator. Look at earlier blog posts for my design, and soon I intend to post a design that will handle up to 2A. My regulator is small, efficient, and replaces the switching regulator, and does not radiate any RF. Watch my blog, new regulator design expected soon! Note, I found a vendor who sells a raw panel without regulator, and has PET coating, so have ordered that and will report back.   

Tags: light

Some considerations for 5V solar charging

A couple of days ago, I posted a comparison of two small 5V solar panels:

https://bkhome.org/news/202104/comparison-of-claite-10w-and-se05-5w-solar-panels.html

And I am looking at replacing the switching regulator in the CLAITE "10W" regulator with my own design linear regulator, similar to the one I constructed in 2016:

https://bkhome.org/light/solar/panels-small-2016.htm

For that regulator, I used a LM2940 LDO (Low Drop Out) regulator, 5V at 1A maximum output. This time, I would like the design to handle higher current. Not that I really need to handle higher current, as that "10W" panel is so pathetic -- I did a quick test of it today, bypassing the regulator, to find out what it is really capable of, and only got about 0.7A at the peak power point, however, sky was a bit misty and solar intensity was only 815W/m2.

Even if I can get solar intensity up to around 1000W/m2, it looks like won't be getting 1A out of that panel. Which will be under 5 watts, probably well under.

Anyway, would like to construct a linear regulator that can handle about 5V @ 1.2A. Altronics sell an LDO that is rated at 5A:

https://www.altronics.com.au/p/z0580-lm1084it-5a-5v-low-dropout-regulator/

...HOWEVER, it is not suitable. The voltage drop from input to output is at least 0.8V, which is too high. Dredging back into my memory, I see from the internal circuitry, that the high voltage drop is due to the darlington transistor configuration. Also, it does not have reverse current protection, and a schottky diode would be required to prevent current flow back into the panel -- which will cause more power loss when charging current is flowing.

Found this one, L4940V5, rated at 1.5A max., pretty much the same design circuitry as the LM2940, with even lower voltage drop, around 0.3 to 0.4V. Meaning, that if 1A is flowing through the transistor, 1x0.4 is 0.4W -- no heatsink required. It is that PNP transistor configuration that achieves the low voltage drop. Ordered it from eBay:

https://www.ebay.com.au/itm/L4940V5-ST-Microelectronics-5V-Positive-LDO-Voltage-Regulator-TO-220-GENUINE/202370864172

Also available from other vendors, such as:

https://au.rs-online.com/web/p/voltage-regulators/2988491/

In the above link to tests done in 2016, I mentioned how the Chinese phones determine if a charger is limited to 0.5A or is capable of up to 1.7A. Simply by shorting D+ and D- together marks the charger as capable of the higher current. This article explains:

https://www.eetimes.com/how-to-conform-to-chinas-new-mobile-phone-interface-standards/

...what is also very interesting in that article, is it shows details of the circuitry inside a phone.

Actually, that detail of connected D+ and D- together is a USB standard:

https://en.wikipedia.org/wiki/USB_hardware#Power

...it also mentions how the requirements for Apple phone is different.

The above article contains links to PDFs that show charging circuits, and it does look possible to satisfy both Android and Apple high-current determination, with three resistors.   

Tags: light

Comparison of CLAITE 10W and SE05 5W solar panels

I tested the SE05 "5W" 5V solar panel in 2016:

https://bkhome.org/light/solar/panels-small-2016.htm

I recently purchased the CLAITE "10W" 5V solar panel:

https://bkhome.org/news/202103/10w-solar-panel-for-usb-charging.html

It has been cloudy recently, but today the clouds cleared, just a bit of faint mistiness, so did a quick comparison of these two panels.

Date is April 5, 2021, 1.00pm, fairly clear sunny sky, solar intensity reading is 830W/m2, ambient temperature is 30 degC -- Autumn, but quite a warm day. Negligible breeze.

I used resistances to place different loads on the panels, and plotted voltage-current graphs. Here is the CLAITE "10W" panel:

Here is the graph of the SE05 "5W" panel:

...in the latter graph, see the foldback effect, which I think is a very good feature.

For the SE05, the peak power point is about 4.78V @ 0.59A, which is 2.8W. For the CLAITE panel, peak power is only about 4.86V @ 0.6A, which is 2.9W. You see why I am putting those "5W" and "10W" ratings in quotes!

Hmmm, it seems that the CLAITE panel is throttling its output. It has a short-circuit current of 2.16A, which is an indicator that this panel potentially has a much higher peak power point.

I did a quick test connecting the CLAITE panel to two Android phones, and got 0.52A and 0.57A. My 2016 post explains D+ and D- pin connections required for Android phones. Shorting D+ and D- together made no difference.

Measuring the resistances between the GND, D+, D- and 5V pin on the USB socket, there are resistors connected to D+ and D-, indicating this panel is designed to charge Apple devices, not Android devices. Here is information for Apple devices:

https://www.instructables.com/Modify-a-cheap-USB-charger-to-feed-an-iPod-iPhone/

https://learn.adafruit.com/minty-boost/icharging

Anyway, connections of the D+ and D- pins does not matter when just applying resistance loads, as I did for the above graphs. The regulator in the CLAITE panel is throttling the output. It should not be doing that.

It looks like I will have to sacrifice this panel, see if can open up that regulator, maybe replace with my own that I built in 2016 -- see link at top of this post.

EDIT 2021-04-06:
Today, just after 11am, I noticed that the clouds had cleared, just some wispy clouds off to the sides, but quite intense blue overhead. Did a very quick test with the CLAITE panel, time 11.30am, April 6, 2021, Perth, Western Australia, sun intensity 885w/m2, ambient temperature 27 degC. Negligible breeze.

I did this very quickly, didn't allow the panel to completely warm up in the sun. Just brought it out from inside, aimed it at the sun, running through an inline voltage-current digital meter, and wrote down the readings.

Charging my Huawei phone, a 2019 model that I actually purchased early 2020 (so I escaped the Google embargo), battery was at 93% and the charging was 4.90V @ 0.78A, which is 3.82W.

Then plugged in my Voltaic V15 battery bank, which is approximately 50% charged, and read 5.05V @ 0.62A, which is 3.13W.

I expected better with the stronger sunlight, but those reading are nowhere near the claimed 10W!

I need to find out what the panel is actually capable of, without the regulator getting in the way. I used a serrated kitchen knife to cut the plastic covering, exposing the regulator:

...at the bottom are the two tabs from the panel, so I should be able to remove the regulator and solder directly to those tabs. The glue is flexible, probably a silicone sealant, so should be able to pry the board off.

The main chip is "XL1410E1" and on the next line "01103". Would be interesting to find the specs on it. 

EDIT 2021-04-14:
Here is a more accurate test of the CLAITE "10W" solar panel:

https://bkhome.org/news/202104/accurate-test-of-claite-10w-5v-solar-panel.html

...hikers, note the comment about the switching regulator!   

Tags: light