Bumper fabric - as a long-time seamstress and sailor, and now a FIRST Mentor, here’s everything you need to know about bumper fabric (for the non-sewer FIRST team member).
What has been recommended: “duck cloth” and Cordura (which is a name brand)
Problem: you’ll see descriptions including denier, weight in ounces or grams, and cotton/acrylic/nylon/polyester/blends. If you don’t sew or make sails, this means NOTHING. to you. “Cordura” is a name brand, so it’s even more confusing (and you will spend more $ for it).
What are we really looking for?
Polyester or nylon canvas that is heavy enough to take abuse. But not SO heavy that it doesn’t bend, or you can’t staple/sew through it.
Polyester and nylon have a high melting point, so you can iron-on bumper numbers.
You can “seal” the edges by using pinking shears (the toothed-edge or “zigzag” scissors)
- All the fancy water-repellent, UV coatings (like in Sunbrella and Cordura) - not needed here, and it’s an added expense.
- Acrylic… you are taking chances with it melting when you iron on numbers
- Cotton - can tolerate some abuse, but will tend to rip at the staples (because we are ALL stapling this to the bumper backing right? Of course we are). Cotton or cotton/polyester canvas is a good choice if you have nothing else.
Great, so what the heck do I want?
My advice: Nylon or Polyester canvas (also called “Pack cloth” or “sailcloth”), 7 oz/yard.
7 oz/yard is a good baseline. It is tough, durable, but still easy to work with. You can go heavier if you like, but it will be stiffer and harder to work with.
(Fabric weights are intuitive - 1 oz/yard is parachute fabric, 11 oz/yard is super heavy, stiff canvas - much heavier than denim).
example: Seattle fabrics - nylon pack cloth 7 oz/yd
Full disclosure: I made a storage sling for my Soling out of this exact fabric. It can be sewn using a regular sewing machine, punched grommets through it, and the sling is still in great shape after 4 years on my boat, outside.
Where can I get this or something like it?
Online. Your local fabric store is probably not going to have what you need.
(If you are desperate and need something NOW - head to a local fabric store and look for the heaviest polyester, poly-cotton, or nylon canvas-woven fabric you can find. Probably in the upholstery section. DO NOT USE FELT. “Rip-stop” fabric tends to be very lightweight, but if you can find it heavy-weight it could work).
Seattle fabrics has been a great source for me (for sailing) and decent prices (not affiliated with them, just a good source I’ve used). You can even get a fabric sample set from them. Sample set I have
Sample set of all weights/types nylon fabric
FYI - you’re going to see “Denier” like it’s important or something. Its really not. “Denier” is just a measure of opacity. If the fabric is white, you can “see through” 50 denier, probably can’t see through 400 denier.
Our Team laser cut our own iron-on bumper numbers. (Have heard you can use a cricut as well)
Iron-on material we used : HTVront White Heat Transfer Vinyl (it is polyurethane, I checked)
To laser cut:
Material: Whatever you do, make sure whatever you use is NOT actual “vinyl”. Vinyl can be PVC (poly vinyl chloride) and anything with “chloride” on it is not laser safe (releases chlorine gas - bad for the laser, not good for you).
Image: reverse the image. You will be cutting from the back.
Power & Speed: On our Boss 100 Watt CO2 laser, we use 13% power, 75 mm/s travel speed. This will cut through the white polyurethane, but NOT cut through the clear plastic backing. It does discolor the back slightly, but that’s the side you will put against the fabric (so it won’t show).
"Weed" the image: remove all the white polyurethane around your numbers.
The official “how to iron on” instructions are below (from the vendor).
Iron on your numbers BEFORE you make your bumpers. I have not tested Ironing on with pool noodles underneath. Iron at your own risk!
These are for ironing onto a cotton t-shirt, so I ironed the bejeesus out of ours just to be sure, right onto our 7 oz/yd Seattle Fabrics nylon pack cloth.
I probably went overboard… but so far, these numbers are not coming off.
- If using a household iron, please use the “cotton/linen” setting (usually the highest temperature setting). Make sure that the steam setting is off.
- Preheat the application area of the substrate for 10-15 seconds.
- Place the weed image (liner facing up) on the preheated material.
- (I use a pressing cloth (muslin, old clean t-shirt, pillowcase) between the iron and the plastic carrier. I don’t really know this plastic, neither do you, and I am NOT going to clean plastic gunk out of my nice iron if it melts). Press the iron, hold it firmly for 15 to 30 seconds, then pick it up and move it - repeat until you’ve ironed the whole image. Do not slide the iron.
- While the fabric is still warm, peel off the plastic carrier. If the vinyl starts to pull, put the plastic back and apply more heat.
- Use a pressing cloth between the iron and the vinyl to press again for 10 seconds, then turn the item over and press from the back for 15 seconds.
Pics of a test to see how this worked.