[Nick Flint Posts: 4957 Status: Offline]

Gee that looks superb Dave. Love the colour choice, tho heat absorption won't be a problem for you. You'll be bomb proof!

[Eric Yeoman Posts: 740 Status: Offline]

Very neat. 

[Dave Munday Posts: 235 Status: Offline]

A little more welding this morning,  straight bits going OK, tabs will have to wait until weekend when Donna can give me a helping hand 

[Eric Yeoman Posts: 740 Status: Offline]

PM me a mailing address & I'll ship a couple of reasonably sized samples. 

[John Robertson Posts: 5198 Status: Offline WWW]

Sewing will be stronger than gluing or welding simply because it's joining the reinforcing mesh together - which is stronger than the coating bond the other methods ultimately rely on (which is why you bond a wide'ish strip to increase strength).  Sewed joints will, ultimately, fail at the thread - it being the weakest link - welded.glued joints fail at the coating-to-reinforcing mesh interface . However, sewing will leave surface thread exposed which will wear off rapidly at the contact line (you could make a composite skirt, using sewed joints everywhere except the contact area which would be welded.
PVC roofing sheet training:

http://www.youtube.com/watch?v=pXDHNjqsoRc

[John Robertson Posts: 5198 Status: Offline WWW]

What are the issues (some pics of peeled joints might help)?  Provided the gun is working OK (check air temp if you've got a meter - should be 250-500C) you should be able to easily melt PVC to the burning/smoking stage (gives off white smoke which isn't good to breath!).  Make sure you leave any welded joints to fully cool before peel testing.

I've only come across one vinyl that wouldn't weld (a scrap section of unknown origin I tried during testing).  Might be worth checking with your supplier that the material is actually hot-air weldable?


Last point is that some vinyls have a lacquer coating on one (or both) sides.  The gun needs to be hot enough to melt/evaporate the lacquer or you get a poor strength joint.


https://youtu.be/PZYB0xKq1Vg

[Nick Flint Posts: 4957 Status: Offline]

It's my understanding that the sewing line becomes the tear off line (like a stamp) ensuring when it fails- it does so in a nice straight line! Any sewed lines will also be prone, (the first) to wear.?
Im SOLD on welded skirts, (BUT so used to glueing).
Achieving the WELDS most easily is worth working out IMHO!

[Eric Yeoman Posts: 740 Status: Offline]

I'm not having any luck with my 1600W welder. My fabric is black vynil, 24 oz. Is this too heavy? Another note: what about HH-66, or similar cement, & then getting it sewed, with rot resistant cotton/twine, ??, by a tarp repairer? There are several in my area.

[Nick Flint Posts: 4957 Status: Offline]

Thanks John, Ian, Dave and Steve.
During my two weld school sessions of 5 mins per time, the effort I (personally) needed to put in seemed considerable and it's only when strength depletes does one realise how much "strength" AND joint health / comfort is taken for granted. Years ago I swam 100 lengths and felt better getting OUT. This would not happen nowadays. What is possible for "still strong people" looks sadly impossible as age raises its ugly head. I can get around MOST aspects of ageing (using levers, brains, tools, patience,) but its not always possible, without throwing "A Good Think" at it. This isn't a moan about aging, - Its a rally cry to NOT aging guys.
This nearly always elicits a solution. Ive not yet given up on remaking a new skirt, as it's so important for relaxed cruising. Going out for "a drag across fragile worn cardboard" isn't MY idea of contentment.
The spot welder looks very interesting. Is THIS worth a try? and THEN rent/ loan it out to members?
I accept Johns feelings over the big roller.
Perhaps a system could be designed to hold the work whilst being welded G clamps etc? Im just trying to find ways to carry on cruising. My skirt is currently hiding underneath the hull coldly snuggled up against my concrete flooring. Luckily, it cannot be lifted up for its service inspections yet.
When I run out of reasons to procrastinate- I shall decide on where I go from here.

[Steve Holland Posts: 1608 Status: Offline]

I agree, the actual weld time is short, most of that is waiting for the heat gun to get to temperature.
Far more time is spent making the panels correctly before welding.
The tabbed curves are tricky, even those aren't too bad with 'John's glove' technique and a follow up roll with the silicone roller.

[Ian Brooks Posts: 3564 Status: Offline]

Now just a little teaser!

https://a.aliexpress.com/_EITUgfb

I have seen this sort of thing, mounted in a chassis with pneumatic press to hold it onto the work, welding tarp material.

Whether this Chinese welder actually works is another question!

[John Robertson Posts: 5198 Status: Offline WWW]

Are there welding machines that undertake some of the muscle power needed to press the materials together?

The roller machines aren't suitable and would result in a negative workload (i.e it'd take longer and need more effort than a hand-held!).  These machines are quite heavy (the cheap ones are lighter but don't worker as well because they are lighter) and could only be used for a couple of feet at a time before having to lift (they are designed for relatively long seam joints in roofing or tarps - the machine alignment for each 'run' is quite tricky and just not worth it for short lengths.   The actual welding bit is a small part of the time required (you need to align edges, cut material, lift and manoeuvre the ever-larger/heavier skirt, etc. between each weld session ).

Total actual welding time for a skirt is probably only about 15-20minutes in 1-2min sessions so not much effort at all (and significantly less than gluing!).

[John Robertson Posts: 5198 Status: Offline WWW]

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

Welding gloves are the easiest solution for the tabs.  Use a gloved finger to fold over & press the tab down as you weld (changing fingers as they overheat - and, if a pro, swap gloved hand once you've run out of cool fingers!).  Then tidy up/check the tabs using the roller.

[Nick Flint Posts: 4957 Status: Offline]

---similar to this. Why doesn't the club buy one and loan out to members? Found on ebay search. Im sure this would create just what we need without all the physical effort of "roller welding"?
Geomembrane Welding Machine Hot Wedge Welder HDPE Sheet Plastic Pond Liner Welde

[Nick Flint Posts: 4957 Status: Offline]

Are there welding machines that undertake some of the muscle power needed to press the materials together?
Its THIS strength that I simply will not manage nowadays and even IF I DID have the strength- it wouldn't last OR/AND the hands and wrists would be damaged for a long time afterwards, in the arthritis / pain department.
Sorry it sounds naff, but knowing ones limitations is a necessary evil (end product)  of the "NOT dying bit 


To quote one grandson- "you're not dead yet pops."