One problem with the current IOM class rules is that proper event measurement requires the use of a cumersome and not very accurateÂ measurement tank to check for the overall depth and hull depth. During the winter Olof GinstrÃ¶m came up with this jig to do the job - here are some pictures and comments from the first trials.
Here is the basic design of the gauge/jig. The hull is positioned between the vertical posts with the fin and keel in the middle slot.
Here is the crucial part of this measurement process: When the boat sits in the jig, the supports under the bow and the stern (wooden blocks) can be moved fore and aft. They should be positioned so that the waterline of the hull sits at the jig-waterline, indicated by the plexiglass edge. This jig can't determine where the waterline actually is, that has to be done by other means, perhaps at the time of fundamental measurement. This waterline posistion could then either be marked on the hull, or perhaps recorded in the certificate (XX mm from stern, YY mm from bow)
After this waterline position is found, using the gauge is pretty straightforward:
Check for overall length of hull. This homebuilt Lokki was actually very close to 1000mm, many of the commercial IOMs we put in the gauge were up to 7-9mm shorter (see below!).
Check for hull depth. There is a slider of plexiglass that can be positioned under the hull to check that the maximum depth from the waterline is <60mm.
Check for overall depth. The 420mm depth has been accurately trimmed by placing a piece of plexiglass where the maximum depth for a typical IOM is expected. We don't have a test for minimum depth right now -Â but competitive IOMs with anything but close to maximum depth are very rare...
One of the shorter boats we tested. This boat is actually sold as a 'meterboat', maybe the proper name should be '99cm boat' ! 😉
Finally, some examples of how different designs look when they sit in the gauge:
The designs from top to bottom and left to right: Ericca (light blue), TS2 (dark blue hull), Noux (translucent), Noux (yellow topsides), Italiko (green), Italiko (Black), Cockatoo (red), and Bagheera (Black).
To conclude, if at fundamental measurement the waterline can be found (with a tank or in the pond on a very very calm day) and recorded, then event measurement can be performed by placing the boat in a jig and aligning the previously found real waterline with a reference line on the jig. Measuring overall hull length, hull depth, and overall depth can then be done without a measurement tank and with better precision than is usually achieved with a tank.
We will trial this gauge at the upcoming IOM Nordics where we expect around 20 competitors, hopefully I can report back with more pictures and comments + any problems or issues found.