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WOT: Using PC7 or contact cememt to bond nylon webbing
 

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daddy-o
Joined: 12 Apr 2004
Posts: 3307
Location: Springfield

7/12/13 11:39 AM

WOT: Using PC7 or contact cememt to bond nylon webbing

I want to make an adjustable strap with nylon webbing and D rings. You know, thread the webbing through two D rings and fold it back flat on itself to hold them loosely in a loop. Instead of sewing it together I wonder if bonding it with PC7 epoxy or contact cement might be faster in man-hours for assembly (without regard to cure time) and at least as strong. It will need to hold 150 lbs.

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Evan Marks
Joined: 11 Jan 2004
Posts: 1652
Location: NYC

7/12/13 3:16 PM

Sewing *is* a PIA, but with epoxy the fabric will no longer be flexible. Does that matter?

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Jesus Saves
Joined: 16 Jun 2005
Posts: 1150
Location: South of Heaven

7/12/13 3:20 PM

Agreed

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April
Joined: 13 Dec 2003
Posts: 6593
Location: Westchester/NYC

7/12/13 5:05 PM


quote:
with epoxy the fabric will no longer be flexible. Does that matter?

I would think it might. In that flexibility of the fabric might break the epoxy bond...

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sandiway
Joined: 15 Dec 2003
Posts: 4902
Location: back in Tucson

7/12/13 7:35 PM

How about melting? Isn't that even faster?

Sandiway

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Brian Nystrom
Joined: 26 Jan 2004
Posts: 5096
Location: Nashua, NH

7/12/13 8:02 PM

Sew it

Forget about contact cement, as it's not strong enough. Epoxy might work, but I wouldn't trust it to hold anything valuable or potentially hazardous if the strap failed. Also, exposure to UV light degrades epoxy, which will weaken the bond over time.

There are reasons that commercially made straps are sewn. If you don't have access to a heavy-duty sewing machine (walking foot machines work best on webbing), take it to a local cobbler to have stitched.

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Sparky
Joined: 08 Dec 2003
Posts: 19068
Location: PDX

7/12/13 8:21 PM

Contact cement and sew...

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Nick Payne
Joined: 10 Jan 2004
Posts: 2625
Location: Canberra, Australia

7/12/13 11:51 PM

If you don't have anything heavy-enough duty to sew webbing, you could rivet it with leather/clothing rivets. I've successfully used them on webbing - in fact I think one of my very early bike helmets from about 35 years ago used rivets on the straps.

Usually sold by craft/hobby shops in small packs together with the anvil for setting them:

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daddy-o
Joined: 12 Apr 2004
Posts: 3307
Location: Springfield

7/13/13 6:06 AM

Sewing: After I posted I tried to remember any time I'd seen bonded-only straps. Never. All sewn. Some big-rig straps appear to be bonded and sewn.

Heat: Tempting, too hard to control.

Epoxy: Flexibility not important, while being used the bond would deliberately be placed on a straight run. Curing time ended up being the deciding factor (despite my earlier statement, meh)

Contact cement: Chosen. There is enough material so 9" could be lost if the experiment failed immediately. I wetted two 3" sections with a 3" dry section between them. Immediately after assembling each I pounded the new bond with a hammer a few times.

Using vice-grips I was unable to pry them apart.

The stress on the bond is very controlled and almost a shearing stress. That makes me think the vice-grips test was far more stressful than the actual use. Considering the webbing is rated at 150 lbs static I think this has better than a snowball's chance in summer of working.

Whether they will stand the test of time is another matter. However, UV exposure will be infrequent.

I'll CC: the Forum to my annual report if I ever publish one.

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Brian Nystrom
Joined: 26 Jan 2004
Posts: 5096
Location: Nashua, NH

7/16/13 6:14 AM

Contact cement also weakens in the heat

If you're satisfied that it's strong enough for your application, fine, but I would never trust it.

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Dave B
Joined: 10 Jan 2004
Posts: 4511
Location: Pittsburgh, PA

7/16/13 7:25 AM

Rivets

+1 on Nick's suggestion for two-part rivets. I've used them several times to fasten nylon webbing and they make a very strong connection. I make the holes in the webbing with a hot wire to seal the edges and prevent fraying. The rivets can be set with a hammer on any hard flat surface if appearance isn't a big deal and you don't need the "proper" rounded head. The recommended anvil makes them prettier but isn't necessary.

Tandy Leather shops carry these rivets in nickel or brass finish and in several lengths.

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Brian Nystrom
Joined: 26 Jan 2004
Posts: 5096
Location: Nashua, NH

7/20/13 6:14 AM

Rivets do work well

I've used them successfully, too. The key is to use the shortest rivet that will pass through the material. If they're too long, they'll bend to the side as you peen them.

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Sparky
Joined: 08 Dec 2003
Posts: 19068
Location: PDX

7/20/13 9:59 AM

Heat does soften glue. I use a heat gun to remove a fretboard for example. But it takes 150+ degrees and time. [or more heat an less tie]

Shoes have had glued/sewn construction for centuries.
You can even still get shoes made this way, although the price will make you cringe.

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Brian Nystrom
Joined: 26 Jan 2004
Posts: 5096
Location: Nashua, NH

7/21/13 9:00 PM

Shoes aren't glued...

...with plain old contact cement. They're typically done with something akin to Goodyear Pliobond, which is considerably stronger and bonds extremely well to leather.

Also, the amount of heat required to soft a glue bond depends on the type of glue used. How much heat is required for the bond to fail varies with the load on the joint.

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