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Performance in the wind: bonded seams vs traditional felled seams?
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Home › Forums › Gear Forums › Make Your Own Gear › Performance in the wind: bonded seams vs traditional felled seams?
- This topic has 16 replies, 5 voices, and was last updated 1 day, 4 hours ago by Justin W.
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Nov 27, 2024 at 7:04 am #3823147
My next project is a solo tipi shelter, which will have vertical seams around 2m long.
I’ve been wanting to try a bonded silpoly shelter for some time – it makes for a stronger, more aesthetic and more waterproof join.
I’ve been in touch with a couple of MYOGers here in Europe who have long-term experience with bonding and their feedback has been 100% positive. One of them did a lot of strength testing in the workshop before he committed, and was impressed by the results vs sewn seams. And they’ve been using the Waker Elastosil, which Roger finds is inferior to the Permatex windshield sealer. So I’m confident that the seams will be strong and durable.
My remaining doubt is around the role that seams play in storm-worthiness. A simple overlapped bonded seam will likely be somewhat less rigid than a traditional felled seam. What effect will this have on performance in the wind?
If a more rigid seam is preferable, how could this be achieved with bonding? A second strip of fabric bonded over the seam?
There was a discussion that touched on this a few years back, but it wandered off topic and never really came to a conclusion.
My instinct is that the basic overlapped bonded seam would perform just fine, and that it would be best to keep things simple. But any advice based on practical experience or engineering insight would be most welcome.
Nov 27, 2024 at 10:10 am #3823150A friend was pretty gung ho on trying this but I never found out whether he went ahead with it not.
I’m pretty sure that you mean Wacker Elastosil. once I tried to get a hold of some in France but it was incredibly difficult for something that comes from a neighboring country.
In a previous thread, Jerry Adams explained how he uses narrow dacron tape to stiffen seams. Maybe that’s something to think about. Seam stiffness adds highly desirable structure.
Good luck with the project!
Nov 27, 2024 at 3:15 pm #3823164Jon – you’re right, I meant to type Wacker Elastosil. I can source it here in the UK, but Roger is adamant that the Permatex is superior so I guess it’s an academic issue.
I can’t find Jerry’s posting in the search. Do you have a link? Maybe it was from before the Great Reorganisation and has joined the digital angels in the sky?
I’ve been doing some googling and I’ve had a little chat with the AIs. There seems to be a real case that reinforcing the seams would be worthwhile if it doesn’t add too much weight and bulk, and if it leaves a little elasticity to absorb wind shocks.
I’ve had an idea that goes like this:
- There seems to be a consensus that a 2 cm overlap is about right for a bonded seam.
- I cut strips of around 1 cm of the same fabric as the fly.
- I bond the strip to the lower fabric, in the centre of the seam.
- I bond the top fabric over the lower fabric and the strip.
This should:
- Add a meaningful amount of rigidity
- Be 100% compatible with the glue, so it doesn’t compromise seam strength
- Only require about 20g of fabric and no extra glue
- Add very little bulk
- Be relatively easy and practical to implement in practice.
Obviously this would be something I’d test in a mockup before committing, but I’d very much welcome any insights into potential downsides, or in better suggestions.
Nov 27, 2024 at 4:37 pm #3823170this doesn’t have much to do with bonding seams, but
I got some 1/2 inch polyester grosgrain from amazon. To verify it’s polyester and not nylon, stretch a 6 foot length about 20 pounds, like a tent stake guyline force. It shouldn’t stretch more than about 1 inch. Nylon will stretch several inches.
Put that on the 4 ridges. Sew a bunch of stitches the grosgrain to the peak reinforcement, one row of stitches along the ridge, a bunch of stitches the grosgrain to the guyline loop at the bottom. Don’t stretch either the grosgrain or the ridge fabric relative to each other. I do several hand stitches at the top, bottom, in between to keep them from stretching relative to each other. Maybe the tent fabric should be stretch an inch relative to the grosgrain.
The ridges of a mid are on the bias of the panels of fabric. It stretches a lot and distorts the fabric when it does. A weakness of mids. One thing you sometimes notice is on the sides, in the middle, it gets pulled a couple inches off the ground because of this.
With the grosgrain, you can put a lot of force on it and it will be rigid. You don’t need a lot of cat cut deflection, maybe 1 inch. The tent flaps less in the wind. I think maybe the tent will then withstand a little higher windspeed. And make less noise flapping.
This is an out of box idea that I haven’t heard of anyone that’s replicated, so maybe it works for me but won’t for others.
I also successfully used a 3 inch wide silpoly strip folded over to make a 1/2 inch strip.
I saw a picture of this mid in the Antarctic where it is very windy. They had poles in all the ridges. They are heavy. This sort of accomplishes the same thing. The grosgrain weighs about 3 ounces for 4 ridges
Nov 27, 2024 at 4:48 pm #3823173since this is a bonding seams thread, I am skeptical of bonding silnylon or silpoly. I would be afraid it would fail when most needed
bonding DCF tents is fine
but it’s just an uninformed opinion of someone that hasn’t tried it
Nov 27, 2024 at 7:25 pm #3823180Jerry –
Thanks – your experiences confirm that this is an idea worth exploring, though with bonded seams I’d have to do it differently – maybe with the method I outlined above.
After all – why make our own gear if we’re just going to replicate the commercial stuff? It’s more fun to experiment.
As for the bonding, I take my shelters into some gnarly places, so I been waiting for others to do the pioneering. Two things convince me it’s time to give it a try:
- I’ve had contact with a couple of MYOGers in Germany who have long-term field experience. And they are both 100% enthusiastic about the results. One of them did extensive semi-scientific strain testing and the results were impressive. Bonded seams got significantly closer to the max strength of the fabric than traditional sewing. And they are lasting fine in use – no peeling or other problems after years in the field.
- Thom Ressler at Dutchware is switching all his hammock manufacturing to bonding. He says it’s a bit slower and more expensive, but the benefits are worth it. Imagine the customer service problems he’d be facing if the start to fail! He’s betting his business on bonding.
As I say – experimenting is fun. I’m going to give it a go. The worst that can happen is that I’ll have to sew a couple of reinforcing lines along the seams – but actual users assure me that won’t be needed.
Nov 27, 2024 at 9:04 pm #3823188There’s a bpl article where they successfully bonded silnylon with silicone. For tie-outs if i remember.
Maybe I’m a little less skeptical now
Maybe try something on scrap fabric and see what it takes to fail
A good experiment
Nov 28, 2024 at 2:23 am #3823199Glad to see you two have connected.
Permatex is obscenely expensive in France. 19€ a tube. Don’t know what the price is in the UK. I’ve had good results using K2 silicone from Poland. https://www.k2-global.com/en/products/k2-clear-silicone-204c-85-g . Same intended application as Permatex but it is not premixed to viscosity.
Nov 28, 2024 at 7:58 am #3823202when I’ve glued silnylon/poly, the edges roll up. You have to put a weight on top to get a good joint
maybe you need a strip of something that’s 8 feet long to put on top of the seam and weight that down
I buy a tube of silicone and dilute with mineral spirits. Products labeled “mineral spirits” are sometimes water based and won’t work. For waterproofing a surface maybe 1:10 dilution, but maybe much less than that to use as an adhesive
Nov 28, 2024 at 8:31 am #3823205I think that the problem with curing is more an issue if you use plain silicone sealant.
The glues are formulated differently, I think. They cure much more quicky, and bond the two surfaces at a molecular level. If my understanding is right, this is a different chemical process.
My correspondents in Germany assure me that the seams made with the Elastosil don’t need to cure under pressure. After you flatten them with a roller you just need to leave them hanging for 24 hours or so without subjecting them to any stresses.
I assume the Permatex will work in the same way, though I’ll have to do my own testing.
Luckily in the UK the Permatex is only £8.95, and as you use it thinly each tube should go a long way.
Nov 30, 2024 at 7:14 pm #3823382Tried Elastosil when it was first recommended on BPL, and found it inferior for sewn seam sealing, let alone bonded seams; so have no desire to try it for bonding. For sewn seam sealing will continue to use silicone sealer on Sil/Poly.
Realize that bonding of fabrics might be easier and simpler, but will continue to use sewn seams with lap felled flat seams, and silicone sealer on Mettler metrosene polyester thread suited to the weight of the fabric and the needle size. This is for MYOG and not for sale to the public, so am not concerned about bonded seam strengths. Have never had a MYOG sewn seam fail. Although not so with sewn seams on some marketed older tents. But now with MYOG, that is no longer an issue. Thank you BPL for these forums.
Roger Caffin recommended other threads on BPL; but I was unable to find it sold in smaller quantities in the USA; so have used the Mettler with no problems. Not sure if that is still sold in the USA, though. OK, call me a stick in the mud; but it is a bone dry mud in a tent in a storm.
Nov 30, 2024 at 8:15 pm #3823385I’ve used gutterman mara 70 thread from rsbtr without problem on silpoly and silnylon. Polyester.
I used to use gutterman sews-all from the fabric store. Occasionally a thread would break in a seam.
Sewing silpoly and silnylon is a bit tricky because they tend to slip relative to each other. (Faux) flat felled seams.
I have never sealed a seam in a mid because the seams are at angle and water flows downhill along the seam rather than going through the seam.
Nov 30, 2024 at 8:18 pm #3823386I’ve only had seams fail when I did something stupid, like having unreinforced guy line pull outs.
Nov 30, 2024 at 8:20 pm #3823387Sam – what advantages do you find with the Mettler Metrosene?
I’ve been using Gutterman Tera, but it doesn’t seem to suit my classic Singer 401 whatever I try. I’ve never been quite happy with the stitch quality I’m achieving. It’s passable, but the machine is capable of better.
I was planning on trying the popular Mara that seems to be something of a standard, but neither you or Roger seem to rate it, and you both know your stuff.
The Metrosene is available here in the UK. If you were me, which would you try next?
Edit: just after I posted, I had another search for Roger’s favoured Rasant, and it turns out they finally have an outlet offering the full range in the UK.
So for tarps, mountain ponchos and the like, I’d value your advice on the choice between Mara, Metrosene and Rasant on a high quality vintage machine.
Also, your advice on a thread for 500D pack fabric would be welcome.
I realise that we’re veering OT, but I’d like to take the opportunity to pick your brains if you can spare a moment…
Dec 1, 2024 at 12:06 am #3823394Hi Jerry,
Well, life is for learning; not to mention MYOG; but I know you knew that already.Hi Geoff,
I asked Roger, and he agreed that the Metrosene was probably the next best after the Rasant. (Roger worked professionally with fabrics.) I’ve found that the former is very strong and works fine in the 1970’s Sears machines that I use. Also, the Sears machines could be left at the local Sears store, would be quickly fixed by Sears, and returned to the store for pick-up. When Sears tanked, I bought a couple of the best machines with the best features, but they sit in my workshop because I’ve never had to use them. Haven’t tried the Mara thread, but will see if it is sold nearby. I like to see sewing materials before buying; but in the last few years, all the good sewing machine shops seem to have gone out of business. But no problem, because I have all I need for a tent or two.Pack fabrics are another material altogether, because they don’t don’t use much fabric, so weigh much less, and the shortcomings of Nylon fabrics are not a problem for me when using heavier pack materials. Heavier sil/nylon works fine for packs, if the pack bottom and lower sides are reinforced with light waterproof fabric. I’ll dig out the name of the pack fabric I use and let you know.
As far as my advice is concerned, I recall my Uncle who was an accomplished Judge and lawyer. When one of the great-grand kids asked to take a picture of him, he said OK, but you better hurry up – meaning that he might go at any minute. Unlike most judges, he had a great sense of humor. When I was a kid, he took me to his court to watch. All the defendants came to court in the early winter, and he would sentence them to jail to stay warm just for the winter, and be released when the weather warmed up and then be let go. His nickname was “Big Al,” because his son was Al Jr. So if you want to pick my brains, you better hurry up.
Happy TrailsDec 1, 2024 at 6:33 am #3823398Thanks Sam.
Given Roger’s expertise I think I’ll try the Rasant, now I can finally get my hands on it locally.
For packs I’m a great fan of Cordura, even though it’s out of fashion these days. I have a Lowe from the early ’70s that I still use as a day sack and it’s survived many hundreds of days in the hills pretty much unscathed. And there’s a pack maker near me who sells a top spec Cordura 500 and 1000. But I’d be interested to know what thread/needle combo you’d recommend.
As for judges, my father was one of the most distinguished judges of his generation here in the UK, and my uncle was a judge too!
Dec 1, 2024 at 11:18 am #3823407Interesting stuff, would be great if it works well. Please update.
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