Fun, fun, fun, Laser sailing...

It's been a year since i gave up on my laser racing, because i was too heavy for a laser(95 kg, and with no money for a finn) and the races were too far away, plus the slovenian sailing association is falling apart.
My race-boat remains tho. I am having lots of fun still sailing it on the lakes around Maribor(also teaching my girlfriend how to sail), and at the sea, when i go there..
..since i have certain ambitions to build my own design cabin sailboat in the future.
 Data collected from real boats is of great importance, so goals for the "big" boat can be set, also much can be learned and calculations confirmed on real boats.

had great fun, with choppy half meter waves
and a 15knot average gusty north-east wind

Over the past two days the runtastic app on my iphone was put to use, carrying it in a water-proof case while sailing.

tested the case-phone-app combo by
measuring half of my sailing on the first day

Measuring the whole route was useless if my predictions were to be confirmed by the measurments.
That is because the speed graph on the phone is not accurate enough to get speed readings for different sailing dirrections. So only stages were measured(e.g. upwind, downwind and reaching)

First my predictions, for the lwl lenght of 3,81m the hullspeed is 4,7knots, or 8,7km/h
The data below are calculated in feet and lbs:

displ/lwl ratio is about 91 which is low in comparison to anything but other dinghies.

SA/displ ratio is 22.6 which is high for boats in general, but normal or even in the lower half for dinghies.

reference, and Principles of yacht design - the bible of boat design

my thought was that laser would exceed the hullspeed by some 10% sailing upwind considering its high SA/displ ratio, and it sailing nearly flat(that is 0-10  degrees of heel), i was a bit angry because no data on the prismatic coefficient for the laser was avilvable on the internet..

Reaching, i was sure it would reach 2.5times its hullspeed, but average a speed of about 2times of the hullspeed, of course no longer in semidisplacement or displacement mode, but planning.

Downwind, my prediction was that it would sail in semi displacement to planning mode,
from 1.1 to 2 times of hullspeed, depending on the wave the boat is riding(a laser does not plan by itself in winds of around 15knots on flat water)

and the course for the data left

and the general data,
 with an average speed of 110% of the hullspeed

here is another upwind(data left and below), the shifts in wind can be seen

above again a 10% higher speed than hullspeed

above the speed is represented by the blue line, the three speed drops are the tacks

The upwind measurements were the most constant, also confirming my expectations.
There are elevation gains and loses, i am not sure why they appear maybe it is gps glitches..

reaching, averaging 1.94 times the hullspeed, close to prediction

above speed is not constant,
as the gusts affect the speed more drastically than when sailing upwind

the biggest speed drop is the gybe(course right and data above)

reaching again, the boat reached the max. speed of 2.6times the hull speed wich is even higher than expected

For some reason all the downwind sessions were lost, but i remember that the speed matched my prediction. It varied alot, depending on the wave, depending on which tack the course varied also, because it is faster to sail a negative downwind(sailng more to the lee than to luff..)


Sailing close to the coast, i had a chance to sail in flat water in a relatively constant wind, eliminating most of the drag caused by the waves:

the avg. speed increased by another two % compared to the hullspeed

That is it for now, it was very usefull to sail on a bigger stretch of water, than small lakes..
..it was lots of fun and a relief from hometown, and school.

In the next post i will be overwieving measurments taken from fila sailing with b-rigg.