MIT IAP Kite Bar
construction details

click any picture to see a big hi-rez version


The kite bar in use

January is Independent Activities Period (IAP) at MIT. Regular classes stop and anyone can teach or take a class. We taught a bunch of folks to make surf kites. This is the example control bar for the class. That stick is 1.25" oak rod from mcmastercarr.com. Use something strong or it'll break and cost you at least one day on the water. Smaller diameter is less tiring to grip. Slippery is bad.


Making the Fairlead
When no one's looking, hack a big hunk of plastic off something military. Drill some big holes in it and saw out the rough shape. Granpappy's hoof rasp with the corncob handle is magic on plastic. Make the fairlead hole big enough to pass the line but stop the knot. Carve off anything that doesn't look like part of the bear.

Wrap sandpaper around the bar and sand a concave mating surface on the fairlead. Eric cut this particular fairlead out of 3/4" thick polyethylene plate with a computer controlled waterjet cutter. Hand tools almost as fast. Use what you've got. Round off all the edges and corners. Use lots of tools. This is a deburring tool  

Lashing on the Fairlead

Lash the damn thing on with innertube strips and go kiting. It'll outlast the season. Or several. If you'd rather get artsy, Cut off about 6ft of nylon string and soak it in water. Nylon elongates ~10% when wet and you'll get a tighter lashing this way. Unlay one end.

Get another short loop of string, lay it along the fairlead. Start wrapping everything with your long wet string. Keep wrapping. You don't have to worry too much about keeping the string tight, because it will tighten when it dries. When you feel like you've wrapped enough, use the loop thingy to pull the loose end of the long string under the lashing. Pull it tight and cut the end off short.

Measure out some epoxy. Half a stroke from each metering pump. Watch carefully and make sure you're not just pumping air. These pumps can require skill. You can also measure the epoxy with a postal scale or pouring capfuls of water into a cup and marking the proper levels. Read the epoxy directions or it won't ever set up.

Mix it by hand or with a bent coathanger in an electric drill. I like epoxy from uscomposites.com $75 for 2.5 gallon kit part#EPOX-635414
EPX-P41 4-1 Ratio Pumps $4.95 / Set of 2

Paint it on the lashings. Get the cheap brushes and gloves when you order the epoxy. Don't get epoxy on your skin or you'll develop an allergy.


Paint the rest of the bar with the extra epoxy and prop it up on nails to set up. Use less epoxy than this. These are drippy and will have to be sanded.With the right amount you'll get a nice finish without sanding. Slow hardener gives a better finish but takes an extra day. Epoxy with fast hardener needs to be washed with water before another layer of epoxy will stick to it well. Five minute epoxy is never fully waterproof and should never be used for anything.


Rigging it Up


The notch on the end is for winding the lines on. Make sure the winding notch is big enough to hold your lines. This one is too small. Tie the leaders on with slipknots. A groove keeps the leader from sliding off the end of the bar. Here's how to tie a slipknot. Tie the chicken loop with a sheet bend as shown. So it looks like this.

Chicken Cleat

Everyone's favorite chicken strap rig.

Use Clamcleat CL211 Mk1, Ronstan RF5106 or similar cleat with a built in fairlead. Poke holes through the rope and bolt the cleat on.Use the right diameter rope for the cleat. The line shown is maximum for this cleat, which barely bites it. Make the chicken strap long, so you can fully depower your kite while unhooked.

This one is a trapeze pulley cleat from a catamaran.


If the line is too small in diameter this cleat will fray it like this. Another feature of "pulley cleats" is that they get further from you when you let them out. The first kind are always right in the same place.

This waterjet cut chicken cleat didn't work at all.

Flying Lines

Make all your flying lines the same length. 100ft = 30meters is standard. Fold over 6" and tie a surgeon's knot at each end as shown here. This is 500lb spectra. Your new lines will stretch a bit when you first use them. The center lines will stretch more due to the greater load, and you'll have to re-rig. You could stretch your lines ahead of time, but we're usually in too much of a hurry.
 


The safety leash uses two rings to pull on one line to totally depower the kite when you drop the bar. The leash could clip to your harness with a plastic snap buckle if you prefer that to the wrist strap. Make the leash as short and stiff as you can without restricting your freedom of movement. That makes it less likely to tangle or strangle you.

 

Speaking of Safety,

Find the online kitesurfing accident database and spend a night reading about all the wierd ways people get hurt and killed with this stuff. I'd give you a link but it moves around. Try the florida kitesurfing assn or groups.yahoo.com


Safety is what you do, not just your gear. Some winds and places are never safe.

Now Go Kiting!

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Copyright Tim Anderson 2003