Alarm bells ringing, I helped rescued a mates kite on Monday when his Dakine spreader bar hook snapped off.

Thank you VERY much for this thread, feels like synchronicity.

I was planning my first attempt at tow up jumping this weekend using a 4 year old Daikine harness.
Thanks to this thread I think ill use an industrial harness instead.

Skid said..

I'm almost afraid to ask.....What is 'tow up jumping'?

(I have a sneaking suspicion that you may be mistaking a kite for a para-sail)?

No, no mistake tow up kite jumping is exactly what the term implies, useing a kite like a para-sail.
Search youtube for "tow up kite jumping" there are more than a few examples. I think the current record is about 750 ft vertical.
I think ill start with a 50m rope, riding up to 45 degrees then droping the rope = 25m vertical. If all works ok then progress to a 100m rope.

PS: I noticed in the video of the highest jump the kiter was wearing a reserve parachute

Effing dakine.. I just got a new harness coz mine got torn off my body while carving to heelside... just lucky I was close to shore and my gear was rescued before it was blown into any obstacles. Never going dakine again, plus thats not the first issue ive had.

kitebored said..

Good idea to check all your gear, I found a crack in a chicken loop recently. Seems quite common also.

in all fairness that's an ancient bar

These spreaders will fit single webbing harnesses, dakine's also but not as neat. They are completely forged, no welds.

www.kitepower.com.au/collections/kitesurfing/Harnesses

We have some with spreader bar pads fitted to them also.

On a technical note there various forms of corrosion that can attack stainless particularly in salt water enviroments.

Intergranular corrrosion. Corrosion between the grain boundries created by heating when welding and poor stainless grades.

Stress corrosion cracking. Corrosion and cracking instigated in a place of stress typically over 55 deg c at standard salt water concentration

pitting corrosion: localised pits of corrosion caused by the break down in passive layer in the stainless.

Crevice corrosion. Similar to pitting corrosion by occurs in a crevice where salt concentrations are higher and oxygen is deprived. This can happen at temperatures as low as -10 deg c.

What does all this have to do with Kiteboarding spreader bars?

Well you kite in the sea which means you are in an enviroment where these forms of corrosion can propagate. The spreader bar is usually wrapped with neoprene or similar which creates a crevice which means salt water can sit in higher concentrations lowering the temperature at which corrosion will start. The donkey d1ck welds are a point of high stress. Then you put your salty harness and spreader bar in a car that us very hot during the day. The higher the temperature the faster the salt water will corrode stainless............

Its all a perfect storm for corrosion to take place at the weakest point. The weakest point is the grain boundries in the weld.

So.... how can you reduce the chance of this type of failure? Rinse off your bar asap to get ride of the salt water. Then dry it off as well.

DO NOT leave any stainless parts salty and wet in your hot car for hours/days on end without rinsing off the saltwater first.

Middle of melville today, whilst racing.... Got to join the snapped dakin spreader bar club.
Was less than 6months old, hadnt checked it so not sure if any cracks had developed.

just to add my two cents to the above info, most of the spreader bar cracks are fatigue cracks from having inferior weld processes(robbo's mate summed the welding side up nicely), then being cyclically loaded during a session ie. repeatedly pulled up forward, left, right etc.

In this situation the discolour you see is typically from chloride stress corrosion cracking (salt induced), this will also slightly contribute to the cracking.

A lot of these cracks will be to hard to see by eye so the best way to check for cracks on your spreader bar, dye penetrant inspection (DPI), you can do a very basic DPI at home, using contact cleaner, red (or any colour but darker the better) food dye, rag and talc powder

Clean/ spray area with contact cleaner, not anything oil based like CRC or WD40, let this thoroughly dry off

Use a small paint brush-if you have one- to coat surface of weld and 5mm of either side of weld with red food dye, leave on at least 20 minutes, recoat if it starts to look dry

Wipe off excess dye with rag, then lightly wet rag with water re wipe area til all visible food dye is gone

Puff a light amount of talc on area, not to thick of a coat, and watch for any red lines appearing.

If there is cracking the dye sucks into the crack (capillary action) and the talc draws it back out, red line = don?t use

More info http://www.ndt-ed.org/EducationResources/CommunityCollege/PenetrantTest/Principles/liquidpi.htm
www.ndt-ed.org/EducationResources/CommunityCollege/Materials/Mechanical/Fatigue.htm


if you are in the south west wa or karratha based I can give you some of the proper stuff to do this