Peter Lynn

February 2002

That's it , holidays over.

Having knocked a few of the rust flakes off at the Nelson kite festival 2 weeks ago, now it's right back into overseas festival-ing with Kites on Ice in Wisconsin this weekend, Pasir Gudang in Malaysia the next and a busy dance card for the rest of the year.

Actually I've used the last month or two of the no-travel break to check out a few half decent Australian reds, fly some kites and do more kite boat development (the never ending story but more about this later),- and also to play with a few old stationary engines of course. In a final holiday diversion, last weekend a couple of vintage car enthusiasts arrived with a very interesting challenge. They had secured the rights to make an official replica of the first motor car; Carl Benz's single cylinder three wheeler of 1886- from 7kgm's of plans duly received from Mercedes Benz. It took 14 months to build and is booked for it's first outing in early February. Unfortunately, it wouldn't run.

This fits the profile of a perfect Sunday problem- that is; has moving bits, makes noises, involves being dirty, is challenging enough to be interesting and is definitely solvable. Just a sudden thought, that I'm too old to have, but no, girls don't qualify- they fail by the final criteria. The Benz' engine has a slide type inlet valve but a conventional exhaust- sort of half way between steam engine and internal combustion engine technology. It should produce 0.6kw at 250rpm on full throttle from it's one litre open crank single cylinder engine. Forget fuel injection, this engine doesn't even have a carburetor-the air intake passes through a sort of half size fuel tank, picking up some fuel vapour fuel as it does. At the start of the day there were only two or three of us but by mid afternoon rather a crowd had gathered,-many "helpful" suggestions. For hours, occasional chuffs were all, we could get but by 4pm it settled down to regular running and the proud builder pop popped off down the track at th e specification 12 km/hr- albeit with some push assist through the larger pot holes.

Directional control is so rudimentary that at the end of each run it was easier to jump off and lift the front wheel around rather than to try steering. In just 118 years this motor tricycle has morphed into 150kw/200km/hr/climate controlled/automatic everything/autobahn cruisers that cost proportionally less of an average person's discretionary spending than the barely drive-able original.- doesn't seem possible, but it has happened. I wish that kite sailing would parallel this.

Today we sailed our latest 4m single person kitesailing catamaran for the first time. Because I'd sworn at it extensively during the final stages of construction (it was behaving very annoyingly), I thought it would bite me back as soon as we were on the water. It didn't, or at least it hasn't yet- maybe it's waiting for an opportunity with more potential for violence. Maybe I better apologise now. At last, an almost perfect boat, with all the best ideas we've discovered in 15 years of kite sailing development: four rudder steering, swinging seat, pull from leeward, displacement/planing hulls. It also has a few new convenience features like an excellent hook in system, no gaps between the hulls and rudders so that lines never get caught there and an electric outboard for when you get caught kilometres offshore in a dying breeze.

It's useable by any yachting standards- easy to sail, very good wind range, high top speed (an earlier version has done over 50km/hr), excellent upwind, surf stable, 250mm draft, 40kgm, car roof-able. Since 1987, I've dreamt a lot about making kitesailing happen; have built many many silly things and some half sensible ones- the buggy boats and later monohulls were far from disasters. Can kitesailing ever catch on? This new boat works well enough for sure- it 's generations ahead of our earlier commercial offerings in every way. But will people want to do it in sufficient numbers?- Bored or retired kitesurfers maybe? Can it develop into a competition sailing class? Even just as toys for mega yacht owners would be a start.

Not that we are planning for production just yet but a problem is that as the design has become more sophisticated, it has also become more expensive to make- US $4000 is probably an achievable retail- but not less after allowing for transport, taxes and margins. Dreaming on! Peter Lynn, Ashburton Jan. 30'2002. Photos coming soon!

Arc Houskeeping. We are hearing of some asymmetrical flying/shoulder collapse problems from users of 630 Arcs, so it's timely to re-publish our understanding of the causes and the (generally simple) solutions. The incidence of this problem last year was definitely less than 1% of kites sold, and as the design construction and materials of this model hasn't changed since then any higher incidence now is therefore likely to be the result of more older kites in use and users loading their kites more heavily as they gain experience and progress to smaller boards. Firstly, asymmetrical flying and shoulder collapsing usually have the same cause, one is a pre-cursor of the other.

The cause is that the fabric in the tip trailing edge area either stretches less than or shrinks relative to the more heavily loaded fabric nearer to the leading edge. Stretching is caused by sustained loading. Higher loads and loads sustained for long periods will cause more stretching as will any load applied to a wet kite. Shrinking is caused by repeated wet/hot/dry cycles.

Because the fabric in smaller kites is proportionally more heavily loaded, they are inherently more susceptible to stretch/shrink effects than larger kites. So far we have always found that a solution is to re-stretch the kite's trailing edge. In minor cases just making the fabric thoroughly wet, stretching out the trailing edge (don't pull so hard as to risk ripping it though) and clamping it as stretched while it dries will be sufficient. In more serious cases we have taken off the trailing edge binding and then re-sewn the trailing edge without it, taking care to use minimum sewing thread tension.

Binding shrinks when it dries out in hot conditions- but this is usually only noticeable after repeated cycles. In the most extreme cases we also unstitch the reinforcing Dyneema cord along the trailing edge and resew it taking lots of care not to pull in the fabric edge while doing so. If we ever come across an Arc with stretch problems which don't respond sufficiently to the above, there are more extensive alterations that can be made. The principle is basically to identify where the stretch has occurred and to fold and sew small tapered pleats so as to take out that stretch. For appearance and aerodynamic smoothness, these pleats are best done from the inside by first opening the adjacent trailing edge seam. For stretch in the middle top section of Arcs- which will cause centre luffing not tip collapsing, this pleat can be done through the zip or velcro flap-no unpicking is required.

Sometimes it's difficult to tell from flier descriptions whether a particular problem kite has a stretched centre or a hooked tip- and it's important to correctly identify the cause before making corrections. Until fabric that is non- shrinking and non- stretching as well as impermeable, tear-resistant, super light, and UV resistant becomes available, some stretch and shrinkage as kites get older is unavoidable but fortunately only a small percentage of kites will be effected to the extent that their flying becomes unacceptable- and larger sizes are fairly much immune.

Stretch and shrinkage are not consistent so it isn't possible to change the panel shapes of the kites as made so that later stretch/shrinkage is already compensated for- or at least not without causing their flying to be unacceptable from the opposite sense in the beginning. So far we have always been able to fix any kite that has come back to us- although some of them have been so old faded and used out that the cost of doing so was probably unwarranted. Tip collapsing and asymmetrical flying can also be caused by broken or weak tip sticks- because this will allow the wing tip to form a curve when the kite is heavily loaded.

Any bending in the tip will change the tip's profile from it's original highly reflexive form to a shape that is more susceptible to tip luffing- although when everything else is in solid condition there is a fair margin designed in before any such bending causes a noticeable problem. If weak tip sticks are suspected, try swapping the sticks to see if the problem swaps also, or try stiffer sticks. A further solution for this is to move the brake attachment point forward to the 75% position as this loads the stick more evenly.

This does however require that the leash be attached to one front line rather than a brake line. Front line leashes tend to reduce spinning of the kite when the leash is engaged anyway. Another but unrelated cause of collapsing is the use of long bars on small kites- basically it is possible to oversteer any kite to the point of collapse by using a bar that is too long, but this is usually only noticeable on smaller kites.




Peter Lynn Kites Ltd
105 Alford Forest Rd

Ph: +64 (0) 3 308 4538
Fax: +64 (0) 3 308 1905