Simple Bulb Design


Since publishing the bulb mould plans there has been a couple of requests for a drawing of only the bulb. Here it is. It's a round cross section 350mm long NACA 0010-34 bulb.

I'm using a feature of Adobe Acrobat 6.0 to attach a DXF version to the PDF file. Open the PDF in acrobat reader and access the DXF by right-clicking on the paper-clip on the right and choose "save embedded file to disk".

Laerke IOM by Søren Andresen

drawing in DXF format

Søren Andresen (DEN) sent me the plans for his own design with which he won the 2005 Nordic Championship and placed 2nd in 2004. He also sailed it into 35. place in the 2004 Euro Champs in Arcos/Spain.

The PDF file contains the sections and a drawing with the mast and keel positions but you should really download the DXF file and printout accurate sections with a CAD program if you want to build the boat.

Continue reading Laerke IOM by Søren Andresen

Arm winch sheeting arrangement


Søren Andresen (DEN) uses this interesting arm winch setup on his boat.

The idea is that by attaching the jib and mainsheet at different points wrt. the block on the arm you can get unequal travel on the sheets. As shown here the mainsail can be adjusted virtually independently of the jib sheet when close hauled.

A number of people were interested in it at the Euros in Arcos so Søren has made a detailed drawing and kindly allowed me to publish it

2004 IOM Nordic Championships, Risör, Norway


The first Nordic IOM Championships were held in the small town of Risör, ca a 2 h drive southwest from Oslo, Norway, during the weekend of 21-22 August 2004. 25 boats(3 FIN, 2 DEN and 20 NOR) in two heats using HMS completed 13 races during two days. The wind was variable in strength and very shifty on both days. Mostly no1 rig with the no2 rigs being used for a couple of races on Saturday.
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IOM mainsail geomtery


Getting the leech points correct when building a mainsail can be quite challenging.
Thomas Dreyer(GER) emailed me with this drawing+text about how to get the geometry correct when you are building an IOM (or M) mainsail.

Lester Gilbert has a similar kind of drawing at his site: "Measuring an IOM Mainsail"

Text is currently only on German, if anyone more fluent than me in German wants to send in an English translation then that would be great ! (Or someone who is good at programming could make a program that calculates the shape...)

IOM Bulb Mould plans

Update 2015-03-01: by popular demand, IGES files for the top and bottom bulb mould. Use at your own risk.

  • bulb Dated 2003-05-01. If you don't have a CAD program that opens these, you can use an online IGES viewer to view the files.

Our bulb moulds are CNC milled from aluminium and more than 15 bulbs have been made successfully from them.

Note that it could be useful to make the hole through which lead is poured in a little larger than shown on the plan.
Continue reading IOM Bulb Mould plans