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Building an IOM

Introduction and cost

In 2020 I built my first IOM without any prior experience.  I mulled over the build material and settled on glass epoxy having seen Brad Gibson's make a plug video.  I only bought materials as I went along, just in case I failed in my quest.  I could not have imagined the end result being a strong competitive boat in local races.  Here is the story of the build.

Summary and cost of the build

To add some colour to my build.  I am a past dinghy sailor and yachtsman and have used glass a little bit in the past but nothing like making a model yacht, so I am a first time builder.     


My biggest challenge - there is a lot of information available but it is spread widely across the internet.  You can see on this web site my sources and the links to each site referenced.     


It started as a covid project last spring and I was inspired by Brad Gibson's video on building a male plug and realised I could build in stages without committing financially to the full project, just in case I was defeated at any stage in the process.    

I could have gone down the wooden route which would have been a lot cheeper but I felt that I could get a stronger lighter result with Epoxy and I have no tools for wood nor epoxy for that matter.     


So I started with 5 min epoxy, a couple of tubes of UHU POR, some red card, Brad Gibson's plans £22, a box of 600x600x100mm blue styrofoam £76, some balsa sanding boards and some sandpaper.  The first stage was to build a fair hull in foam which to my surprise I achieved.  Once I got to that point I could then order the glass mat and epoxy and soon I had a male mould.  Making the hull over the mould was relatively easy but take care of the corners at the bow and stern as you can get air gaps.  One issue was deciding the layup.  There are some clues from the boat manufacturers but I am not sure whether to believe them.  I do know you need a layup totalling 10 to 12 oz per sq metre.  On my next layup I will try 3 layers of 124g s glass which is a smidge lighter than my first boat      


Once the hull is pulled off the mould it is important to have a jig in which to rest the hull and use to measure the overall length precisely, centre the keel and rudder and make perpendicular to the centrelines.  Then it was a case of adding the internal bits and pieces and building the rig.     


The only major failure.  I forgot to reinforce the hull under the mast and nearly pushed the mast through the bottom of the boat, which would have not looked good on the water.  Other than that everything was hunky dory.     


Re the rig.  I bought a kit from Housemartin sails for the rigs, sails and fittings.  There were no instructions with the bits, but there is great documentation on how to put a rig together on Salesetc and I was able to work everything out from there.  The sails are inexpensive and very nice to set up.  You probably only need to buy an A and B rig initially.     

I bought the fin rudder and bulb and fin case off Dave Creed who I believe is the best in that business.     


Since the boat was first on the water I have made a lot of fitting refinements and I think I now have a final configured boat.  Golden rule is the simpler the better.     


The boat is competitive but I am sure it will never be as fast as the top production boats in a strong breeze.  My goal is to see how far up the ladder I can get when the ranking events start.  The boat is a regular winner at Frensham pond and on a visit to Emsworth I finished 4th after 10 races out of 15 in a fleet made up of production boats driven by some very experienced sailors.     


Regards cost and time.  I have spent approx £400 on the hull (including tools) and £900 on fittings (rig kits A,B,C £300, rmg winch plus switch £235, Radio kit £108, fin bulb and rudder £110).  I made my own boat box and rig box for less than £50.   Compare this to buying the full kit (inc A - C rig, rig box, boat stand, boat box) for £3-4000 depending on where you buy.


If this information inspires you to build a boat, you won’t be disappointed and I am always happy to offer any advice.  You can do it with patience and above all very careful planning and remember there are loads of people out there, willing to help.

Next section 

Acquire the Plan

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