site  contact  subhomenews

Refinements to glueing tarp

June 26, 2021 — BarryK

Continuing TreeHugger 1P Mark-2 project, previous post:

Some issues have been identified, and solutions...

Glueing reinforcements

I have glued on the tie-out reinforcements, and it has, in some of them, been unsatisfactory. These reinforcements are at the tie-out points, where webbing is to be sewed on, to spread the tension. They are just pieces of the same fabric glued onto the tarp.

The procedure is to spread silicone adhesive on a reinforcement, using the fingers, then lift it up and place it onto the appropriate place on the tarp. Getting it to lay nice and flat, and in the right place, no ridges and no bubbles, is a challenge.

There is a video on YouTube where a guy shows how to do this, that I have linked to in an earlier blog post. However, I have concluded that his method is not suitable for me. Where is that video? Ah, here:

He might have got away with it using heavier fabric, however, 10D silnylon is incredibly stretchy. Using the fingers to smooth out the piece of reinforcing, and push out bubbles, stretches it -- and here is the thing -- the underneath fabric does not stretch, or will stretch less. So, after attempting to smooth the piece of reinforcing, ridges can form in the underneath tarp. You might then battle to stretch the tarp to remove those ridges.

One factor though, in support of his method, he is using Gear Aid Seam Grip seam sealer.  In his case, the surface is PU, but for silicone surface, as for silnylon, Gear Aid have "Silnet", also known as "Seam Grip + Sil", which is a thinned silicone adhesive. Seam sealer, being thinned, is quite runny -- it is designed to seep into the sewn threads.
Silnet is far more runny that straight silicone adhesive from the tube, that you buy in a hardware store. The runny seam sealer has much less "grip" between the two surfaces, so you are more easily able to push the reinforcing around after placing it on the tarp.

Note, I have experimented with that Silnet. You buy it from camping stores, it is for seam-sealing tents. It is very runny. Also, it is much less "sticky". I found when folding the hem, that it was somewhat reluctant to stay down. The straight silicone, you fold the hem, and that's it, it is stuck.

So, using straight silicone adhesive and pushing the reinforcing around with the fingers, what you end up with is a weirdly distorted reinforcing.

Extra notes about the video:
Do not use bare fingers, as he has done in the video. Exposure to harsh chemicals may not have an immediate effect, but in the long term the body will react.
Also, I think the way that he has spread the seam sealer is inefficient -- dribble beads over the entire surface first, in roughly parallel lines, then simple sweeps with side of a finger can spread it.
Also, with care, the piece of reinforcing can be laid pretty much in the correct place, without all the wrinkles requiring to be pushed out as he has done.
He used a soldering iron and comments that it cauterizes the edge so won't fray -- however, as the reinforcing is glued to the tarp, there won't be any fraying -- besides, ripstop doesn't fray. Cauterizing will cause lots of little melted lumps -- notice, later in the video he trims some of them off. OK to cut out the circles with scissors.

I used this finger method on a few of the reinforcing pieces, then remembered that with Mark-1 I only used the fingers a little bit, then used the Uni-Pro seam roller. See photo of the seam roller here:

Yes, this is the way to do it. Hopefully, lay the piece of reinforcing down accurately, so you don't have to pull it around, then run over with the seam roller.

So, some of the reinforcing tie-out points look good, some look crappy.

Spreading adhesive

I posted about a problem with spreading the adhesive for hems and ridgeline. A dribble of adhesive along the line to be joined, then use side of a finger to spread it. But of course the adhesive will spread out, and the problem I had was the chalk mark getting erased. I posted about this problem, with a suggested workaround to draw arrows:

However, today I devised another solution. Bought 16x16x1.5mm aluminium channel from Bunnings, cut it at 45 degrees, and very carefully filed the tip so that (hopefully) a thin film of adhesive will be spread, only 13mm wide:


I filed so that an extremely thin film of adhesive will slide through. The channel is held with the index finger pressing lightly so that the sloped end slides over the fabric, following the marked chalk line, the sides keep the adhesive from spreading out. Adhesive still needs to be dribbled down the line-to-be-joined beforehand.

Length is non-critical, I cut off 14cm of channel, which fits nicely in the hand. Cut at 45 degrees because my hacksaw-jig thingy only does 22.5, 45, or 90 degrees. Perhaps a steeper angle would be even better.

A little bit of experimenting, and it works well. The great thing about this is two-fold. Firstly, the chalk line is still there, so can see where to fold the hem, or overlap the ridgeline. Secondly, no glue is wasted.

That second point is very important. I have found when constructing Mark-1 and Mark-2, that the glue can very quickly become a significant part of the weight of the tarp. I would even say, that if you apply it liberally, you could even double the weight of the tarp-sans-glue.

A little thought about the weight compared to sewn tents. They need seam-sealer, such as Silnet, and you can very easily use up a 50g tube on one tent. My glued tent does not need seam-sealing, except where the tie-outs are sewed on, and the amount of glue used could be similar to, or less, than that used to seam-seal a sewn tent. As long as there is no excessive glue applied.

The 16x16x1.5mm (13mm inside width) channel is OK for the hems. For the ridgeline, need wider channel, but the biggest that Bunnings sell is 20x20x1.5mm (so 17mm inside width). Actually, the 3cm overlap that I have done so far for the ridgeline, is probably more than needed. Will think about that. Might shop around, see if can find slightly bigger channel.

Chalk marking

I have posted about using a fabric marking pencil. Still not happy about it. It is some kind of "chalk", but is too hard, and I have to press harder on the fabric than I would like.

What I am using now is a chalk bar, designed for use on fabric:


...I bought the second one, because the first is out of stock at my local Spotlight. The inbuilt "sharpener" is a joke -- just use a blade, or any sharp edge.

I also bought some chalk from the kid's section in Kmart, but found it to be unsuitable -- too crumbly. It tends to come off in chunks rather than a nice line on the fabric. Maybe it is just the cheap brand -- "Anko", which is Kmart's own brand.

Bought 25.4x25.4x1.2mm, 0.45m long, "Connect It" rectangular aluminium extrusion from Bunnings. So that is about 23mm inside width. Cut it at 45 degrees. Here it is:


Not yet tested. I think that it would be necessary to dispense the adhesive in a zig-zag pattern along the line to be joined, to optimize even spreading.   

Tags: light