But our Clive Garrett is often asked what to do in an emergency so he took to his workshop to look at ways to quickly repair an air tube with minimal disruption to a holiday.
By Clive Garrett
It is important to note
1. The protective sleeve should never be opened or removed unless you are positive that the air tube is leaking and needs repair.
2. The air tube is oversized, allowing enough material to be carefully tucked back on itself at each end in order to protect the end welds.
3. That these instructions are not relevant in the rare event of a catastrophic failure of an airtube (bursting).
4. These are temporary repairs only and your local Outwell retailer should be contacted in order to organise a replacement tube.
I removed an air tube from its protective sleeve and tried to damage it. The tube proved so tough that it took a knife to puncture and slit the material.
I repaired five punctures and four slits using:
a. Tear Aid Type A (Also marketed by Storm)
b. Stormsure Tuff Tape
c. Tenacious Tape
d. Gorilla Tape
e. Ultimate Duck tape
f. Homebase Power Cloth Tape
a) to d) are from my field repair kit, e) to f) were obtained from a DIY store. All tapes chosen should provide instant repairs.
After each repair I re-inflated the air tube and left for an hour before retesting pressure. The materials that showed minimal air loss were then left overnight before I tested the pressure again. Tapes d) to f) showed varying degrees of unacceptable air loss and, due to inflexibility, distorted the air tube (image left) so were discarded – although, like c), d) may have certain value in an emergency. Tear Aid, Storm and Stormsure tapes provided perfect repairs and feature in my tent repair kit.
I also tried to damage the connecting tube. This proved impossible to split so after 15 minutes working it back and forward (image left) I resorted to shears. I then successfully mended the split using Tear Aid Type A covered by self amalgamating tape (also known as self-bonding tape) to strengthen the repair when under pressure.
I repeated the test on a longer 17cm slit crossed by a 3cm slit and immediately placed under pressure.
As to be expected, without the protection of the sleeve the split became wider (first image below) and developed a bulge when the Tear Aid stretched as the air pressure was slowly brought up to and approached 0.5 bar — yet it maintained an air tight seal.
The pressure was taken off and the air tube was returned to its protective sleeve to reinforce the repair. The air tube was then slowly brought up to 0.6 bar without any noticeable problems (second image below).
NOTE: The sleeve is a key structural element and so an air tube should never be inflated unless enclosed by the sleeve. And the sleeve should never be unzipped if the tube is inflated.
NOTE: It took a little force to push the repaired connecting tube through the sleeve grommet and this should be kept in mind when making a repair.
So, here is how I repaired an air tube in my workshop.
It will be a little different out in the field for you should be able to repair damage without removing the tube from its protective sleeve – a little like repairing a bicycle inner tube… (see Finding a leak below)
My test rig comprises a main tube to provide operational pressure and an undamaged spare air tube. I tested these before I started to ensure everything was operational (first image).
I then cut an approximate 2.5cm V-shape slit in the air tube (third image) and cut the connecting tube almost half way through (second image).
1. Clean the area with an alcohol swab to remove grease and allow to dry.
2. Cut out a patch allowing around a minimum of 2.5cm each side of the tear. Here I use Tear Aid – Type A (also available from Storm), although I have also used this technique for Tenacious Tape and Stormsure Tuff Tape.
3. Stick one edge of the tape to the air tube and gently stick down taking care to minimise air bubbles. Press down firmly.
4. Clean the connecting tube with an alcohol swab to remove grease and allow to dry. Wrap the damage in a strip of Tear Aid Type A.
5. Wrap the repair with self-amalgamating tape to provide rigidity and prevent the repair tape from distorting under pressure at this high stress point. The self-amalgamating tape should be stretched two to three times its length as it is applied and it will then bond with itself to provide a tough glue-free sheaf. This is critical to the success of the repair.
6. The repaired air tube then went on the test rig and slowly inflated by cracking the isolation ball valve to check it was air tight. Remember that in normal circumstances the air tube must be in its protective sleeve before inflation and that the inflation without the sleeve here is for test purposes only. For more info on valve maintenance click here.
• Do not inflate an air tube, repaired or otherwise, until it is in situ and protected by its sleeve – and never undo the protective sleeve when an air tube is inflated.
• Once the repaired air tube is in its sleeve slowly inflate to the lower end of the operating pressure range by cracking open the isolating ball valve.
• Regularly check air pressure to ensure minimal stress to the repair.
• The use of self-amalgamating tape is critical on repairs to the connecting tube due to the pressure and stress experienced at this point.
• Remember this is a temporary repair. Contact your supplying retailer as soon as possible to arrange a replacement tube.
Have you repaired a bicycle puncture? Then you can repair an air tube – it is very similar!
1. If an air tube appears to have lost its pressure first consider:
• Ambient temperature – if it is cold then the air pressure will diminish and an air tube will appear deflated.
ACTION: Leave – the pressure will increase as the day warms.
• Air loss from the inlet valve – sometimes dirt stops the inlet valve closing properly, leading to air loss.
ACTION: Check for air escaping and, if so, strip down and clean.
2.Try to locate the damage. Pump in more air, close inside valves if present, and look for visible damage. Try to hear air escaping or feel it against your cheek. For small punctures it might be helpful to apply a little water on the spot you suspect as small bubbles will show up.
ACTION: Mark the damaged spot.
3. Completely deflate the damaged air tube. Then open the sleeve zip until you reach the location of the leak.
ACTION: Repair as above.
1. Regularly check the air pressure. Standard operating pressure lies within 0.3 - 0.5 bar. However, warmer conditions, like those Continental temperatures experienced in summer, may require a lower pressure around 0.4 bar. ACTION: Pressure will change throughout the day and you may find you need to add air at night to compensate for falling temperatures and let air out in the morning to prevent over expansion as the pressure increases with the heat of the day.
2. If the protective sleeve swells or bulges DO NOT open the zip to check.
ACTION: Immediately reduce the air pressure.
3. In the unlikely event that the seams or zip on a protective sleeve fail then deflate the tube immediately and temporarily repair the damage using a strip of Gorilla or heavy duty Duct/Duck tape that has minimum stretch to provide tube support under pressure. Re-inflate the tube to a lower pressure to prevent stress on the repair.
4. Do not open the sleeve unless for repair – this will minimise the chance entry of abrasive/sharp contaminants.