[Dave Munday Posts: 235 Status: Offline]

This welding is fun, now going to attempt the tabs.

[Ian Brooks Posts: 3564 Status: Offline]

We’ve been learning to weld today for the ATC hovercraft skirt with Gaz. He’s become pretty confident after only about half an hours practice.

[Nick Flint Posts: 4957 Status: Offline]

Oh Gosh, well done Steve.

[Steve Holland Posts: 1608 Status: Offline]

Welded/bonded. Once you do it this way you won't go back, I believe that's true of a few things in life.
Welding is quick, less smelly and permanent.
Down side is if you make a mistake it's less easy to fix, I welded the last bag joint incorrectly, I now have a line of weld at the rear of the craft where I had to cut and rejoin once the twist was removed, even doing that wasn't too bad to do.

[Nick Flint Posts: 4957 Status: Offline]

Bonded or glued?

[John Robertson Posts: 5198 Status: Offline WWW]

... and the last BTW for now is that the roller that is included free with the hot air gun is pretty junky!  If you want to make your life easier or do any serious work the buy a proper pro silicon roller (they have a good handle and ball bearings, etc.).

[John Robertson Posts: 5198 Status: Offline WWW]

SO JOHN - is THIS now the way forward for skirt fabbers or are we still in the "suck n sea zone"? 
Do you sea what I did there? 

Like everything, thorough testing is required -  that should happen over the next year or two (new materials are also involved in this case in an attempt to produce a lifetime, zero maintenance skirt).  The welding process itself is well established so, unless I've got something badly wrong, it should work as advertised. 

The skill level might make it difficult for some to master, PVC in particular often comes lacquered to keep it shiny - and it's easy to weld the lacquer together to produce a joint that looks OK but isn't very strong!

BTW anyone using one of those hot air guns should remember to turn the temp down and let it cool before turning off the fan - they won't last very long if you don't!

BTW2 I assume you bag skirt owners out there are regularly checking the skirt for wear? 


If the coating wears to expose the fabric (little white/grey spots appear) it will rapidly lose tear strength risking a disabling failure.  The skirt contact line should be re-coated every 20-40 hours or so with adhesive (contains PU which helps protect the PVC) - more often if you see wear marks (deep scratches and small patches of fabric spotting).  If you let it get to the point were large areas of fabric are exposed (which means the fabric itself is being worn away) then the skirt really needs renewed.  With reasonable maintenance, the current 910gsm PVC most use should be good for at least 300 hours with no major tears or holes (it is highly tear resistant - until the fabric is exposed that is!).  PU material is at least 5 times more wear resistant (but costs 4 times as much as PVC!).

 

[Nick Flint Posts: 4957 Status: Offline]

Nice piece of kit Al;- filed for future purchase.
SO JOHN - is THIS now the way forward for skirt fabbers or are we still in the "suck n sea zone"? 
Do you sea what I did there? 

[Al Posts: 908 Status: Offline WWW]

This is the hot air welder I have ordered: 
https://www.ebay.co.uk/itm/1080W-Plastic-Welder-Hot-Air-Welding-Gun-Heat-Torch-2-Speed-Nozzle-Roller/152709460245?ssPageName=STRK%3AMEBIDX%3AIT&_trksid=p2060353.m2749.l2649


It's cheaper for me to buy one of these than it is to buy a litre of glue and have it delivered

[John Robertson Posts: 5198 Status: Offline WWW]

1 Is this mainly for straight edges - then usually contact glue around corners i.e. 3D curves?
2 Is the "welder" just a hot air gun with a narrow spout?
3 Ive experienced a glued skirt seam peeling away under the unrelenting Scottish sun in the past,
and simply cleaned when convenient, roughened and reglued, remembering to "kick the skirt under" when stopping.
4 Is a welded heat pressurised joint better at stopping sun initiated loss of bond?
5 Is this the "recommended Otter way", and compatible with Otter materials

1. Corners are perfectly possible using the normal tab "fold over" technique (you need a thin piece of hardboard or whatever between the two sheets of fabric to avoid accidentally welding them together in the wrong place!).  I usually tack the tabs using a welding-gloved finger (unless you have three hands there isn't any other way) before completing the joint using the roller.  Then turn over and fix any small weld gaps (the small nozzle supplied with the welder works for this if flattened).
2. More or less - a 1kW or more gun is required to get enough heat & flow (output temp is around 550C!)
3. Yep
4.  There is no bond after welding - it removes any bond issues altogether which is the main reason for doing it.

I will stress again that it is quite a difficult process to master (at least I found it so!).  Too much heat or too long and you melt, burn or stretch stuff, too little heat,too fast, not vigorous enough rolling and the coating doesn't fuse.  Much practice is required!  However the results are excellent once mastered.

[John Robertson Posts: 5198 Status: Offline WWW]

It's maybe not quite as easy to do as it may seem!  I talked to a  pro roofing guy before I tried it - the process is certainly not as forgiving as gluing (the "good joint" window is very narrow for welding) but the result is much better.  TPU is very consistent for welding but PVC can be variable - some of the PVC material I've got simply won't weld reliably at all - I've no idea why).  It's worth checking with the supplier whether the material is suitable for hot air welding?

I should probably mention the main downside of welding skirt material!  It's the permanent fusing of two coatings into one therefore it is physically impossible to separate a welded joint without de-laminating the fabric (glued joints can normally be taken apart with careful application of a heat gun).  Moral of this is you need to make absolutely sure the joint is correctly positioned BEFORE you weld it!

I've also been welding TPU film onto the wear points on a bag skirt (it increases the coating thickness by around 4x which should extend the skirt life to 25 years of more) - more info once I've tested how it performs in the real world (it is incredibly difficult to weld large areas of film using a hot air welder!).

[Nick Flint Posts: 4957 Status: Offline]

Impressive Mr R   
1 Is this mainly for straight edges - then usually contact glue around corners i.e. 3D curves?
2 Is the "welder" just a hot air gun with a narrow spout?
3 Ive experienced a glued skirt seam peeling away under the unrelenting Scottish sun in the past,
and simply cleaned when convenient, roughened and reglued, remembering to "kick the skirt under" when stopping.
4 Is a welded heat pressurised joint better at stopping sun initiated loss of bond?
5 Is this the "recommended Otter way", and compatible with Otter materials?


I trust this will go into "Builders advice" areas?

[Al Posts: 908 Status: Offline WWW]

Well done John.

The video on welding a hovercraft skirt is useful.  I have some skirt material to join and was going to buy glue, but decided to buy a hot air welder instead, as cheaper than buying glue.