An "International One Metre" Conforming Boat

Basic Class Rules:

Length Over All 100 cm

Min Weight/Displacement 4kg / 4000 cc

Max Hull Draft 60 mm

Overall draft 370 mm minimum and 420 mm maximum

Keel min weight 2.3 kg, max weight 2.5 kg

Rudder max weight 75 grams

Hull min weight 1.5 kg, but boat + keel + rudder must exceed 4kg

Positive Mold #1 - June 9^th, 2001

Constructed of Plywood and basswood

Due to spreadsheet error, this hull mold is flawed.

Length at Water Line 998.5 cm

Beam 18.7 cm

Transom Width 16 cm

Draft of Hull from theoretical waterline 4.4 cm

Theoretical displacement of hull 2791.6 cc

Theoretical wetted surface area static - 1359 cm^2

Hull shape based on increasing circular arcs based on a circular arced rocker (static depth).

This mold was made over a few days during the deluge of Tropical Storm Alison. Why am I building an IOM sailboat? I have no real clue. Partly because I want to learn boat-building skills, partly to put some of the tools we have here to use, and partly because lately every major college sailing event I have gone to has been near an IOM contest. It was designed on the basis of a brief study of a few of the "commercial" IOMs (well not really commercial, but people who will build you one for $1,000 or more). I choose the skiff / wide-transom because it provides more stability. Because of the limited amount of weight allowed for ballast, every thing else that can help keep the boat vertical the better. Besides that, I like the look… it reminds me of America's cup boats. Click on the picture for a larger view.

Positive Mold #1 Corrector Binds - June 9^th, 2001

Estimated Length at Water Line 999 cm

Beam 20.6 cm

Draft of Hull from theoretical waterline 5.3 cm

Theoretical displacement of hull 3823 cc

Theoretical wetted surface area static - 1562 cm^2

Theoretical center of buoyant force is 528 cm from stern (52% of buoyancy from displacement comes from bow of boat)

At 30 degree heel, wetted area is 1563 cm^2 and wide-transom hull alone will give 13% more lift over a narrow transom hull in the direction of fighting heel of a similar displacement/width.

Opps! When I started working on the web-page for the boat, I realized that with my playing with the spread sheet I used to create the hull lines, at some point I got over into designing for a 3000 cc displacement, which won't work with a boat that HAS to weigh 4kg. After playing with the numbers some, I found that it basically will require an addition of about 1 cm to all the current dormers, except for the bow and stern which have no effect on the water displaced in static pose). Below are the pictures of the original patterns (on grid paper) and the new patterns. Realize, though, that on the new patterns, the tops are not cut flat like the originals.(well most of them anyhow). It's amazing that you can gets another 1000 cc of water out of the way by adding to little to the boat. The 3rd and 4th pictures show 5 of 9 correction collars installed before I ran out of decent quality wood. The bow piece was removed (which is why it looks a little strange.

 New purchase: Play-doh $1.50

I couldn't get the paper to roll right around the bow of the mold, so I decided to resort to childish ways… play-doh :-) ... a fun "toy" which makes a good modeling clay. It pressed into shape quite nicely. It made a perfectly smooth, nice surface. Unfortunately I wasn’t sure about how to harden it, so I just left it to harden its normal way… and well it shrank a little and cracked… but still had about the right shape. My experimental block that I tested out another method on worked well, and I will use it next time I do this (if ever)… apply a little elmer's glue over the surface and seal out the air. It keeps the clay the same, and adds a little strength… then apply paper over that to add support and it would be fine. Only downside is this will now make the bow of the mold a little on the heavy side. I need to get some more wood to finish the last 3 collars and then the surfacing. At which point this mold will be complete and ready for the next phase… making a negative mold from it.. which will be an adventure, but I have found something that might work. And no it's not play-doh (although that would be interesting. I also need to look to see if dewalt sells a replacement pad for their random orbit sander… ours blew up last night while sanding with it… its probably over-kill anyhow for little bits of word for support systems. Also need to see if a friend of the family will make the sails for me.

Covering - June 11^th, 2001

After a trip to Michaels.. the building is back on. I cut out the last 3 correction rings and attached them. And then began to skin the mold. Just for construction bits, every of the original pattern bits are of 1/4" plywood. Most of the spacers and the correction rings are 3/16" basswood. The front sections (due to large binding needs) is 1/16" balsa-wood, and the rest is and will be 1/16" basswood. Unfortunately the CA glue that I bought was not in a very manageable dispenser, and I over used it. Unfortunately that led me to not be able to complete all the skinning. There is a high probability that I will have to make a negative mold of this one.. then a positive mold from that and then correct imperfections in smoothness and cast that to a negative mold as a final mold.

Covering Part II - June 12^th, 2001

Covering continues at a remarkably fast pace. However I feel like the people that cut the tiles for the shuttle… every piece has a very specific shape that is not exactly square. Sadly I have run out of cyanoarcylate glue again. But I managed to spare this package more. I used 4 .07 ounce tubes on the panels you see in the upper pictures (about 14) and I managed to make this last .14 oz one go about 18. A panel here refers to any piece that is tacked down on four corners. I might go back and use the "xacto" blade to shape the seams a little better. The bow sections still need a lot of work (in these pictures they were taped in an effort to glue them down, but the port bow has a crease that I am going to have to shape some more. I really want to cut this out right so I don't have to make multiple casts.

Covering Part III - June 12^th, 2001

Covering has progressed quite smoothly. At this stage all the panels are in. Now I just have to try to remove some of the square-edged-ness (if that is such a word) of this mold.. to try to make it easier to fix in the later moldings. I probably will also cover it with thin paper (save maybe the music-box drawing) to help in that end.

Big Red Boat - June 14^th, 2001

Well no, it's not a cruise ship, and no, it's not the prettiest thing in the world, but the prototype positive mold is nearly complete. The good thing about the negative mold will be the ability to "add" more to the shape, which the way this one was made took away. While it would be possible to do this with mass amounts of epoxy resin at this stage, I want to keep down the costs to a minimum at this point. A very thin coat of epoxy plus pain is bringing the boat's thin shell up to a size that can be safely sanded smooth without fear of cracking the wood pieces. Just need to fill a few small gaps and sand her smooth and this will be ready to mold… which I am not sure exactly when I will do. After I mold it, I will probably sell the positive mold as-is on ebay. So far the one of the most noticeable errors on the boat is the 80-ring is off-center by a perhaps 4 to 6 mils. It's too much to correct on this mold.. but on the negative I can hollow out the recessed side, and on the casted positive mold I can hollow out the excess side. Also the bow has changed some. The bow should be 40 mils tall, and at the moment it has grown to 47 mils… but the shape is almost perfect. At the moment I am planning a simplest deck for the final model for the original boat. If it seems to be a good design then I'll sell the prototype boat, and look at making a more technological deck line. My current desire is to get SEISA hooked on IOM boats, and perhaps sell them to SEISA schools. I can produce the hulls a lot cheaper than is currently available from out-of-US producers. Incase you are not well aquatinted to the IOM boat, they cost about $1000 or more for boats out-of-country. There is only one US producer, and his boats cost an out-of-this-world price.