On Tuesday, January 3, 2017 at 8:04:38 PM UTC-5, Joerg wrote:
Gentlemen,

Is there something stronger than the usual rubber cement in the patch
kits? Ideally something that won't dry out so fast or where multiple
cheap small tubes are available.

The reason is that I sometimes have larger holes from side wall
blow-outs. Not inch-long gashes but one or two tenths of an inch long.
The tubes I use are super thick and, therefore, expensive. $15-20 each
and that's not something to be thrown out lightly. Instead of the li'l
REMA patches I need to use thicker rubber from an older sacrified tube
but this has to be vulcanized/cemented really well.

--
Regards, Joerg

http://www.analogconsultants.com/

You can use place a second offset patch over an existing Rema patch. This way you can patch long slits using the F1 (25mm) Rema round patch. Patch one at a time, then sand the top of the patch in the direction of the patch center to the end, apply the vulcanizing fluid and apply the next. Repeat the process until the entire slit is patched.

Make sure you start and end about 15 mm beyond the slit. You may also want to cut a small circle around the ends of the slit to stop the slit from expanding when the tube is inflated.

You have not stated the tube size. This is important because the patch must fit within the width of the tube when the tube is flat. I've found I have to use the F0 (16 mm) patch for tube widths less than 25 mm. I've found the wider F1 (25 mm) patch will work with tubes with a nominal width of 28 mm and above.

It's important that the patch edges are "glued." I've found the best way to insure this is to lie the tube on a flat surface and burnish the patch onto the tube after it's applied. I use a center to outside burnishing motion. I use the rounded edge of a Rema patch kit as my burnishing tool.

There are some rubber compounds that won't work with the Rema vulcanizing fluid. It also won't work in cold temperatures or when the tube is wet. However, I've found that most of the time the reason that patches don't adhere is due to improper application - pilot error. Sand over a bigger area than you spread the vulcanizing fluid; spread the vulcanizing fluid over a bigger area than the patch. Spread a thin layer of the vulcanizing fluid and let it dry before applying the patch. Don't blow on the vulcanizing fluid to hasten its drying - the moisture in your breath will neutralize it.

If your tube has a rubber composition that will not work with the Rema vulcanizing fluid, you may want to reconsider your tube choice.

I assume the reason you opt for a thick tube is to avoid flats. However, you are paying 3 times what I pay for normal thickness tubes. At about $0.75 per flat repair, I can make a lot of them to my inexpensive tube before reaching your $15 threshold.