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Old 28 April 2004, 11:48   #1
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glueing hypalon

may be of use,,,





Repairing the tubes
As far as the air tubes and fabrics of the boats are concerned, you first need to carefully inspect the surfaces looking for areas where the outer proofing of the fabric has been worn away, where taping and seals mayhave lifted, and any other evidence of damage or decay, especially in the more inaccessible areas. Also check such items as handholds, fender strips, bow rings and transoms. You should not be able to lift any of the joints, seams or patches when you pick at the edge with your fingernail. If you do find any areas where there is lifting or wear and tear, then mark these with a ball point pen or magic marker to ensure that they receive further attention.

You will probably be aware of whether or not the boat is leaking air during your regular use of the boat, but now is a good time to check out the air holding qualities of the tubes by inflating them hard and painting them all over with a soft brush dipped in a foamy detergent solution. As we have already mentioned, if there are any air leaks they will soon become evident because bubbles will form. Modern fabrics mostly have excellent air-holding characteristics and you shouldn't have any problems but older fabrics, particularly those where the rubber was knifed rather than calendared on to the base fabric, do sometimes suffer from porosity which will be evident as a series of pin prick leaks over an area of the surface. Other leaks will be obvious as a series of bubbles forming in a particular spot or perhaps along the edge of a seam. These should all be marked with a ball point pen which will be visible once the tube dries off. Whilst checking for fabric leaks, also paint the detergent over and around the air valves to check these for airtightness.

Now you have the marked areas which need attention around the boat you can make a start on the repairs. If the seam edges have lifted, then you will need to dry the affected areas thoroughly; again a hair dryer can be good for this. Separate the affected areas as far as possible, which means opening up a seam until you come to sound adhesive. It is possible to open up a seam or an attachment flange further by careful application of hot air from a hair drier into the gap using a fine nozzle. The heat will soften the adhesive and allow you to peel it back gently; in this way you can be sure that you have got back to a sound bond before starting the repair. Now sandpaper the exposed surfaces between the two edges of the seam, or the patch and the air tube in the case of an attachment, so that you have a good key for the adhesive. Whilst holding the surfaces apart, firstly clean them with Toluene, Acetone or a cleaning liquid supplied by adhesive manufacturers, then apply the adhesive, making sure that both surfaces are completely covered in a thin layer. Let this first coat dry for about 15 minutes and then apply a second coat of adhesive. Once this is tacky, after about 10 minutes, you can press the two surfaces together, starting from the back of the seam and working towards the edge to exclude all the air, using as much pressure as possible. It may be better to do this work with the tube deflated so that you can use a small roller to remove any air from the gap, and this will also allow you to apply good pressure to the two surfaces so that they bond properly. After a few minutes you can then clean up any excess adhesive with one of the solvents mentioned above. The adhesive will take around 48 hours to fully cure and you should then have a seam or attachment which is ready for another season's use.

These maintenance type of repairs are quite straightforward providing you can get reasonable access to the area. They are not generally critical repairs compared with those which involve a serious air leak or damage to the fabric. These can he divided into five different types all demanding a different approach:

The small repair which may be anything from a pin prick to a tear 5 cm long.
A tear up to around 25 cm in length, provided that it doesn’t go through any seam in the air tube, or cover more than one compart- ment in the air tube.
The major repair to extensive damage to the air tube which may require major surgery.
Repair to damage on the fabric floor of an inflatable where you can get to both sides with relative ease.
Repairs due to wear and tear causing chafe of the fabric.
The first of these is relatively straightforward and can usually be repaired with a single patch on the outside of the tube. The technique used is to cut a patch with rounded corners from material similar to that from which the tube is made. This can usually be obtained from the manufacturer of the boat or a service and repair agent. If the fabric has neoprene on one side and Hypalon on the other, make sure that you use the material the same way round as the way it is used in the boat, which normally means having the Hypalon on the outside. Cut the patch to extend 5 cm clear of the tear or puncture, so that you have a good overlap, place the patch on the tube and mark round its edge. Prepare both the patch and the tube by lightly sanding the surface. You can use an electric sander for this job pro- vided you use it with care and don’t take off too much of the rubber. It is vital that you achieve a fresh, clean surface otherwise the adhesive will not do its job properly. Once you have cleaned the rubber don’t touch it with your fingers because you will transmit grease to the surface, and the I Small patches on the inflatable tube. The marks are made on both the tube and patch when dry to nelp line up the patches when the adhesive is applied. adhesive won’t stick in these areas. Use a solvent to clean the sanded area thoroughly. After this you may need to re-mark the position of the patch on the air tube if the original markings have been removed; you use this mark as a guide as you apply a thin, even coat of adhesive to both the patch and the tube, allowing a small overlap on the tube. Again, allow the adhesive to dry before applying a second coat. Once this has become tacky, you can then position the patch on the tube using the marked lines as a guide. When you do this make sure the tube is lying deflated on a flat hard surface and apply the patch with a rolling motion, one side first and gradually smoothing it across the whole area so that air is forced out and doesn’t become trapped as a bubble. You only have one chance to get the patch in the right place because bonding of the adhesive is instantaneous. If you do get it wrong, careful application of heat from a hair dryer will help to release the bond, but you will probably have to apply another coat of adhesive and go through the process again. Once the patch has been applied to the air tube, flatten the surface with a small hard roller starting at the center and working outwards. A roller comprised of several discs is better than a solid roller. The aim of rolling the patch is both to improve the bond between the two components and also to help roll out any air bubbles from the adhesive area which may have become trapped. Pay particular attention to the bonding around the edge of the patch and when the patch looks firm and secure you can then clean it up with the solvent that you used before. Allow the patch to cure for at least 12 hours before inflating the tube — longer if you possibly can.

For large tears in the inflatable tube then an inside patch is necessary to give the repair adequate strength. It may sound impossible to put a patch on the inside of a tube, but it can be done with a bit of careful planning. First widen the hole to around 10 cm, if it is not already this size, so that you can get your hand inside. Now cut a patch which has an overlap of at least 5 cm and follow the same procedure as before, cleaning up the tube surfaces inside the tube and on the patch, buffing them with sand paper to get a fresh clean surface and finally cleaning them with a solvent. Now you apply adhesive to both the inside areas of the air tube and to the surface of the patch, let them become tacky as previously described, and then apply a second coat. Now you come to the tricky part where you have to get this patch inside the air tube. The best thing is to try a dummy run first without the adhesive so that you know the sort of procedure to adopt and then slide the patch into the air tube, pressing the tube firmly down on top of it. It sounds easy but is quite a tricky maneuver because as soon as any two layers of adhesive touch, they will want to stay together, and you can end up with a sticky mess unless you plan the operation carefully. You can use thin polythene sheet to cover the adhesive so that it won’t stick, and then peel it off before making the final attachment, but try one side of the tear first and then the other so that you can line them up evenly. Once in position, rub the air tube down firmly with the roller to exclude any air bubbles, leave for 12 hours or so and then try inflating the tube to a pressure of not more than 2 psi to ensure that you have a proper bond and air tightness. Now you can tackle the outside of the tube, the method here follows the same procedure as for a small tear except that you will be dealing with a larger patch which will need more careful handling but again should be applied at one end first and then gradually rolled into position along the length of the tear.

Some people recommend that, with a longer tear, it is stitched with a needle and thread to restore some of the strength of the fabric and to hold the two sides of the tear in position whilst a repair is made. Against this has to be argued that it is impossible to put on an inside patch if you adopt this technique and secondly it is almost impossible to get an even, professional-looking repair because the stitching will almost invariably show through the outside patch. With good gluing techniques and working in the right conditions this stitching should not be necessary and it is important to fix on an effective inside patch because you will then have a double seal against future air leakage from this potentially weak point.

Repairs to extensive damage are best left to service agents and boat- yards to carry out. They have the experience and expertise to do this sort of repair properly and it does require a lot of planning and patience if you are going to get the job right. However it is not impossible for the amateur to do this sort of repair work, but it will often mean opening up the seams of an air tube to get access, and SO you need to look carefully at how the boat is constructed originally and plan your tactics accordingly. It is not easy to give precise rules for these extensive repair jobs because each one may need a different approach. Opening up the air tubes can be done with the hot air blower and careful work with a knife-like tool to gradually peel the seams apart. If the seams are taped you need to take the tape off first and then tackle the seam itself, but once opened up, repairing the original damage can be relatively straightforward because you now have access to both sides of the tube. Bringing the tube hack together can be a real problem but if you work it out carefully beforehand and follow a logical sequence of work, you should have a boat which is as good as new at the end of the job. The secret of this type of more extensive repair is careful planning; always try each operation as a dry run before you carry it out with the adhesive in place.

Probably the most difficult repair of this type is one where the tear extends over a seam. Any patch you apply over the seam will tend to leak because of the small step between one side of the seam and the other due to the thickness of the material. It is almost impossible to get an effective repair without carefully tapering the edge of the fabric so that there is a smooth transition from one layer of fabric to the next. Simply trusting to the adhesive to fill this gap will rarely work effectively. Probably the worst damage of all to repair is one where it goes through the bulkhead dividing two compartments. This really is a job for the professionals, and even they can find it hard to get an effective repair.

Among the easiest types of repair, for the owner to carry out, is one in the floor fabric of an inflatable boat. here you have full access to both sides of the fabric and the patching material should he applied to both sides so as to restore full strength to the original fabric. The techniques are similar to any other repair work for this type of patch. Any patch on the surface of the inflatable tube or in the floor which comes into contact with the water, should be taped along the edges with thin neoprene or Hypalon impregnated tape. This tape is much thinner than the normal tube fabric so it provides less resistance to the water flow and is less likely to peel off under pressure

Finally in our round tip of repair techniques, the alternative type of repair which an owner might he faced with is where chafe has worn away the surface rubber or there is porosity over an area of the inflatable tube. The basic technique is very similar to that already described, but because the size of the patch is likely to be larger than with most repair jobs you need to pay careful attention to the application of the patch, applying it down one side first and then carefully rolling it down over the tear pressing it as you do so to exclude any air bubbles until you reach the other side. It is much easier to get rid of air bubbles during the process of applying the patch than it is after it is attached and a job of this type should be done by two people: one to do the rolling and one to hold the patch so that it can be applied in a controlled manner. Indeed, with most repairs except the smallest, two people can do the job much better than one, and this coordinated approach will produce much better results.

The inflation valves found in inflatable boats are generally very reliable and if replacements are required then it is generally only the insert which needs replacing which is a straightforward job. Should the whole valve need replacing, then this job can be done by the owner but it does mean opening up one of the seams of the air tube to get access to the inside. You will need to use a hot air blower to remove the existing valve before glu ing the new valve in position. After that it is a question of following the techniques already described to seal up the air tube again.

Adhesives
Adhesives come in two types: one-part and two-part. Single part adhesives are those normally supplied with a boat’s repair kit and are certainly much easier to use if you have to make emergency repairs when away from facilities. The one-part adhesive remaining in the tube or tin can be used again, although it will deteriorate more quickly once the container has been opened. With a two-part adhesive, once the two parts are mixed then you have probably about one hour before the mixture goes off and becomes unusable. However the two-part adhesive does give a far superior bond which is why the manufacturers of inflatable boats always use it. These adhesives, of which Boscoprene 2404 is one of the most popular, do have quite critical operating requirements. For the 2404 the manufacturers quote a pot life of 6 to 8 hours in a closed container once mixed, and a shelf life of 9 months from the date of manufacture. The curing time is 48 hours although the bond strength continues to increase up to a maximum of 7 days. The curing rate can be accelerated by heating to not more than 700C. The solvents used in these adhesives are similar to those used for cleaning the rubber fabrics and are usually a mixture of Toluene and Acetone. Bostik supplies its own specially developed cleaner/thinner for use with the adhesives, but the standard Toluene or Acetone solvent will do the job equally well. When using either solvents or adhesives, bear in mind that they are toxic and highly inflammable so that you need special care when using them in an enclosed space. Ideally, all repair work using adhesives should be done under controlled conditions with a temperature of at least 600F, and with low humidity In particular, high humidity is not conducive to effective repair work which is one of the reasons why repairs done outside are often much less effective than might be expected. If you have to carry out emergency repairs in poor conditions, especially damp, then try and create a mini-environment around the repair area which can be kept warm and dry for at least the critical two hours of the initial curing. For winter repair and maintenance work, a heated garage will usually provide adequate conditions for effective repair work but like everything else relating to the construction and repair of inflatables the conditions and the planning of the job are the main ingredients of success. A piece of boat fabric will look quite harmless after it has been cut and positioned unglued on the boat but that same piece of fabric will appear to have a mind of its own and want to curl up and stick to anything which comes near it once you have applied the adhesive. Simple techniques such as taping the patch to a beer can, or other cylindrical object, before you apply the adhesive means that you can keep the patch under control, and simply roll it into position. The same problems can occur when applying tape to a seam; a lightweight tape with adhesive on it will be extremely difficult to handle. Wrapping the tape around a can or similar object will help to con- trol it as you apply it to the tube. With longer pieces of tape you can put polythene between the layers to stop them sticking together and in this way application can become a simple two-handed job and not a nightmare tangle of sticky tape.
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Old 29 April 2004, 05:11   #2
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Nugent,

Many thanks for that. Most useful. I recently spent hours trawling the internet for gluing info and the best I could find was a technical sheet for Bostik 2402 on a wet-suit shop's site, - ewetsuits.com - in Glasgow. (Worth a visit)
http://www.ewetsuits.com/acatalog/bostik-2402-guide.pdf is the direct link if anyone is interested.
I recently had a tape seam start to pull away slightly. I did most of what you had said apart from the pre-cleaning with solvent. Seems to have stuck though.

Now all the info is in one place.

Much appreciated!

Mike C
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Old 29 April 2004, 05:14   #3
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took me ages to find it, as i was curious as to best way of tackling it,,
glad to be of some help,,,
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Old 26 July 2007, 04:14   #4
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Nugent, this is very informative for people but i would not recommend the use of a ballpoint pen on hypalon, on lighter coloured fabric it would be a nightmare to get off!
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Old 26 July 2007, 04:22   #5
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just need to make sure the glue is not from a "dodgy" or "out of date" batch and everything should be fine!
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Old 26 July 2007, 04:24   #6
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Quote:
Originally Posted by ribraff View Post
Nugent, this is very informative for people but i would not recommend the use of a ballpoint pen on hypalon, on lighter coloured fabric it would be a nightmare to get off!
i aggree Edd.. i posted this in 2004, waking the dead huh,,, china graph or simmilar wax crayon would be better,,
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Old 26 July 2007, 13:11   #7
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I think rubbing alcohol (isopropyl) will aid in removing ballpoint ink. I'd be a little careful about using wax or grease pencils near where you're trying to stick things down...


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Old 26 July 2007, 13:13   #8
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I use a chinograph pencil for marking cutlines etc. but you do have to make sure that it is all off prior to glueing.
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