Thin IOM

How thin is to thin for an IOM? Can a 6" or 160mm one be made and if so what would be required to carry full ballast or would the bulb weight need to be reduced?


I could be wrong, but doesn’t the IOM class have a minimum weight? So if you go skinny, you will need a very deep hull in order to support the minimum required weight. It all depends on the hull design, it is doable but I’m not sure how well it will sail if the hull itself (not the keel) has to be deep enough to allow the required displacement. At the same time you could on to the next big thing in the IOM class, if you have an idea of your design parameters like where the max beam is and everything I can throw it into freeship and see what you get out of it. Just a thought.

The class rules impose a maximum hull depth from the waterline of 60mm. The minimum weight is 4000 grams and the keel/bulb combination must be between 2200 and 2500 grams.

You’d be strugling to design a hull within these restictions as narrow as 150mm.

Well the problem is I cut side profiles from the Noux design out of 1/4inch MDF to make a plug like the one shown in my attached link above. So it comes in a 160(not thinking before to measure what 20 peices would measure in at) (its to cold here -20c to think). So its an existing design, and instead of doing it all over again, do you think I could add more profiles to increase the beam. I do not have plan on racing, except with my balsa core Triple Crown I made a couple of years ago and inviting friends or co-workers. There is a few pictures of a really thin IOM I think made by someone in Germany, how is that one done?


I didn’t see a link anywhere. I know really thin One Meter boats ussually fall in the USOM category. Todd Brown built a very nice looking carbon USOM that is ultra thin. The design I have is one of his “wider” USOM designs at right about 6 inches. I also used the MDF method, very labor intensive, but with rewarding results, plus it is fun to start the sanding becuase you can see it take it’s actuall smooth shape. If only they had some intermediate thicknesses between 1/4" and 1/2". I think half inch is still too thick for my next 52" project.

Sorry Millertime here is the link,

this is that skinny IOM i think its Michael Schamers?

The skinny mdf plug on Ourwalden is a USOM. That is the design I built.

So do you think it would work to add extra prfiles to increase the beam?

Every profile would need to be adjusted to account for the new profiles, which would be a task to complete by hand. If you werent constricted by length you could add them to the center and create a longer boat with a very narrow bow. Either way it will effect the designed displacement, but if it an experiment than that can be accounted for in the weight of the boat.

Thank you Millertime,

right now there is a step of about 1.5" between each next piece so I thought is I was to trace one and enlarge it to be between each profile the I could increase the beam? hope that is explained right?

I guess in theory that would work, you might need to do some further adjusting after you increase the size, but I would say go for and just take a good long look at the lines before you start to cut them out to make sure they make sense. It is too much work to cut them all out to realize there might be some kind of issue. If I build another 1 meter boat, I think I will have the buttcks cut by laser.

thank you again,
I will try it and see, should i keep the volume in the bow or in the stern?

I think you will be forced to follow what the current lines dictate. The stern has very flat sections so you will be forced to keep them that way or you will create a ridge down the centerline of the aft sections of the boat. The bow will become a little wider theoretically offsetting the volume from the stern sections. Just a side note, while it doesn’t appear this way by the plug, this hull is as close to a hard chined design as possible without being hard chined. It def. has a very flat “bottom” and slab sides, hopefully it works out for your idea becuase i think it could be a good looking boat.

thank you again, the internet is a wonderful thing. What is the average widths of IOM’s.

I THINK somewhere in the 9" - 10" range, but I am not sure.

You’ve mentioned Michael Scharmer’s designs. They are about as narrow as an IOM gets. His topsides are slab-sided and his hulls are very flat (and therefore high-volume) athwartships down the full length of the keelson.

As for average beam - gee - I don’t know. Beams across the deck have been reducing in recent years. Where just 5 years ago a maximum deck beam of 220mm would have been considered narrow, it is quite common today. There is still a good variety though - with competitive boats falling anywhere in the 190mm - 250mm range. There are of course still plenty of TS2s racing well - a design now about 13 years old (I think) and about 300mm in beam.

A good source for comparision of designs is here:…

To follow up on Muzza’s post and a link to a different page from that wonderful Nordic IOM Site:

That first boat is really skinny.

My Ericca’s beam is around 220-230mm and it is considered a good lite air boat. My Kite has a deck to deck beam of around 240-250mm. The Kite hull can actually incorporate an IMAGE/IKON deck, which mine does in a skiff alternative. Although the deck has a rather wide beam, the beam at the waterline seems to be just slightly wider than the ericca’s. go figure.

Holy geez, that first boat is crazy, I would hope it tracks upwind quite nicely at an apparent cost of beauty.

i have been designing IOM know for over 10 years
i just have to ask you one question>? why do you want to go thin?
i have a design somewhere around that has a 5 inch beam. but the boat sits real deep in the water. and does not turn worth a damm. but in a straight line. she is fast i also have a design opposite almost 16 inch. but in a good blow. the boat will slide sideways. but it turns real well. and sits on top of the water
look around. do some surfing, download some pictures and do some research. i have over 2 gigs worth of pictures
anyboat can give me idea. that same can work for you:zbeer:
good luck

I was not planning on making a thin IOM, its just I took the side profiles of the Noux plans and cut them out of 1/4 MDF, which resulted in a 6" beam, I was just wondering if it would work like that or if I hade to add additial profiles (which i have done now) and it measures 8". Are some of your plans available through email, I would like to see the two extreme’s. Do you race them all?