Dave Piercy's Canopy Repair Instructions
Firstly, whether you're repairing loose pieces or just a crack, stabilise the pieces really well from the outside
of the canopy - your favourite duck tape will do. Getting the levels wrong at this stage will come back to bite you later!
If you have cracks that are disappearing into the rest of the canopy, stop-drill the end of the crack as soon as you can -
it will continue to grow if you look at it hard!!! Be careful that you drill the hole at the end of the crack - you'll
often see holes drilled along a crack where the hole didn't intercept the end of the crack and it kept growing past the hole.
About a 2 mm or 1/16" drill will do the job - size doesn't much matter if it's in the right place!
From the inside, start cutting a deep V - groove along the length of the crack. Do this with a Dremel or similar tool, using the corner of an end mill. Don't use a round burr or similar tool, or you'll end up with a "U" shaped trench, - you need to have that "V" shaped trench. Go really deep - to half -way through the thickness of the canopy. When you get to the stop-hole, chamfer the edges of that as well.
If the working situation is awkward or your hand isn't steady, put masking tape over the canopy as close to the
trench that you've made as you like, this will avoid you dropping glue on parts of the canopy that you really
don't want to have to touch.
Get your glue ready in a dropping dispenser of some kind. I use Tensol 12 - there are others.
Lay in a THIN layer of glue covering the groove you've made.
Patience at this stage is vital. There's a great temptation to put in too much - the final result will be full of bubbles along the line of the repair if you lay in too much glue at a time.
Wait for the glue to cure, lay in some more. Repeat. Wait. Repeat. Wait. Repeat............
Eventually you will have filled the trench up.
Start on the outside. The pieces (or crack) are firmly held together by now (or should be) and you can
carefully remove the holding tape from the outside.
Now repeat everything on the outside.
When making the "V" trench, keep going deeper and deeper until you have removed all evidence of the line of the crack -
in other words, you need to be able to just intercept the cured glue you laid in from the other side.
If you don't go deep enough, the line of the crack will always be there to laugh at you, and there's a chance
of stresses between the two sides.
Don't forget to chamfer the hole(s) at the end of the cracks.
Start laying in the glue, as before. Protect the canopy, as before. Patience, patience.
If you see bubbles in the glue line, it is possible to remove them using a needle, but you'll find they can be very persistent.
Use a combination of "popping" them and dragging them to the edge.
When you've filled the trench up, wait for a number of days for the glue to really cure well,
you want it to be good and hard, right?
If you've done the job right, you'll have a line of glue with a rounded top to it,
and hopefully none or very few bubbles along the length of the original crack.
Now protect the canopy again and start rubbing down the glue line with wet and dry paper -
Start for a little while at a coarse grit of say 420, and move up rapidly through the grits
up to about 1200 or 1500 stage. Finish off the job with jeweller's rouge, Duraglit, metal polish or any similar very fine polish.
Do all that again on the other side.
You'll quickly find that you didn't lay the pieces in properly and will have to grind the
surrounding area to get red of any "step" in the repair.
You're unlikely to be able to make an invisible repair without a good deal of experience,
so practice on cracks which are not in the normal line of sight at first.
So, it's not difficult, but you do need to have good, practical hands and patience, - and some practice.