The glue I use on PVC is Bostik 1669. It requires some care if the repair is to be a good one.
Personally I would not bother fixing your Zodiac
. Dump it and buy a Swift, an Achilles, or some other Hypalon craft and leave the PVC in the garbage. Better still--get a Polycraft or its American equivalent if there is one.
However--to get back to patching the boat
. Once you have to patch it, it can never be inflated to the level it was with welded seams. Personally, I never inflate them hard anyway, because the sun heats them and they develop excess pressure which ruptures the hull
. There is no NEED to inflate them hard. If you want it to last--do not do so. I got five years out of mine--and it was a BASTARD on fuel
with its stick-to-the-surface inflatable
floor and keel--and a pig to row. I fitted mine with a honeycomb-glass floor I made and solved
Back to patching your PVC Zodiac.
Clean off the area you wish to patch both inside the hull
edges of the hole as well as outside using MEK or acetone. This leaves the surface a little tacky. Using a cheap
disposable brush, paint
it with the glue on the INSIDE of the hull edges of the tear or seam. Allow it to dry thoroughly.
Now prepare your patch, a piece of the same sort of PVC, by cleaning
it on the one side, and then painting it with glue and allow it also to dry completely. Do not touch either surface, and keep them free of dust.
Return to the hull and re-glue over the already dried glue. Let it dry once more. It is messy so wear disposable polyurethane
surgical examination gloves, I buy 'em by the box.
Return to the patch and apply another layer of glue. Let it also dry, not quite as thoroughly as before though Just dry to a light touch (wearing gloves).
Now you need to have a large strong paper clip or a couple of clips--the sort that you have to squeeze to open. If the repair is to be a long one--you may need two of them. Place a piece of polythene over the middle of the patch, fold it in half, and put your clamp on it so that the surfaces without glue on the back of the patch are pressed together and the glued surface is protected by plastic where the clamp holds.
Open the seam, and work your patch INSIDE the hull, holding it by the clamp so it does not drop inside the hull. Some people use string threaded through the patch and back out again to get a better grip. It does provide a couple of holes though--but these may not be a problem as they are comparatively more easily fixed. Make sure these holes are on the join in the seam.
This paper clamp does not hold strongly , so the sooner one gets this interior
patch in place the better. Ease the seam apart and gently insert the patch making sure only the plastic shield makes contact with either glued surface. As soon as one end is in place reach in with a pair of curved long nose pliers and, still holding your patch with the clip, and the other third hand behind the hull pushing from the other side, begin to peel off the plastic. The instant the glued surfaces come in contact they will try to stick together, so the seam has to be folded over the patch as the plastic is withdrawn. As soon as the end is glued, one can reach the patch from the other side of the hull to push it into place over the seam, and the clip can be removed and the seam and patch pressed together over the whole length of the opening.
Now get a hot air blower, and heat the entire patch area quite strongly while firmly pressing the patch into place from the outer side of the thoroughly deflated hull. Tap it firmly but not too firmly with a flat-faced hammer against a block of wood. Allow to cool.
Now, move to the outside patch. If you had used strings to hold your patch instead of a clip--strings being more reliable but leaving holes, you will have to patch these holes.
For this I inject a little polyurethane
glue while keeping the repair as horizontal as possible. This stuff foams and spreads--making a satisfactory sort of seal, since the air pressure of the completed hull will hold it on instead of trying to lift
it off,, The same logic as for the interior
patch. The patch should still be clean so it should stick OK.
Now to the exterior patch. This one will be much easier to do--but it is the interior one that will be the strongest in resisting impacts on the hull--the exterior one is to reinforce it, and greatly increase the bond strength as it will be in double-shear.
Pretty much the same process--but you might try THREE layers of glue instead of two--just to be certain. Heat it when you have rolled and tapped the patch into place, working from one end to the other and ensuring a good contact. Now heat it with an air gun to quite warm, put a flat block of wood over the entire sandwich and one behind it, and use three G clamps to press the whole job tightly together and leave overnight. In the morning take off the clamps and half-inflate the hull--just enough that the patch is lifted from the other side of the hull, and no internal adhesion is possible however unlikely.
Leave it for at least another day---then inflate it to about 2.5 to 3 psi no more--and test it for leaks
with detergent and a brush. If it is OK--you are good to go.