Edge IOM homebrew

Here’s a short vid of my latest IOM design. Built from balsa and F/G, Walnut veneer decks, 2K painted hull. Rebated freeboard along the midships (edge) and a flattened, stretched foredeck. Appendages from Dave Creed sails from BG. 6.6V Life battery, BRC 280es self tensioning winch and drum, futaba s3050 rudder servo. Bare hull = 663 grams, complete IOM ‘A-C’ rigs, ready to race prior to corrector weight = 3880 grams


This vid doesn’t appear to default to 720HD so open and adjust the settings for better picture quality

Looks good - have you raced her against other IOM to see her pace yet ?

I have competed in a couple of Club races and she’s doing OK. She’s by no means faster than the other designs including Lintel, Cockatoo, Pikanto Isis and obligatory Triple Crowns. However, wether it’s my tuning or not she does point well so her VMG compared to the others is much better. Down wind she is prone to nose dive slightly sooner than the others so I do have to be very vigilant.
This Sunday is our first District Event which I’m really looking forward to. If I finish in the top half of the fleet I’ll be very happy with both my skill as a skipper designer and builder. If I don’t I’ll just blame the design ;>)

Mark it does look good. how does it behave going straight down wind? I saw a few things in the design that was impressive… How does the stern act in a blow? My new design does not have the stability that a wide stern does… what is the beam on your boat?

Hi Cougar
The Edge is my fourth IOM design. Each one hand drawn (no software here), evolving and encompassing different ideas. Learning by trial and error to put it bluntly! Although, to answer your question Edge’s on the water beam is 178mm with a transom width of 95mm. At th moment the transom is a little high in the water so I will be moving the corrector weight back until it’s resting little lower. As for her stability I haven’t noticed a lot of difference between Edge and BOR (my 3rd IOM design) which has the same beam, slightly different rocker line and a 110mm transom. My next design will probably have a beam of 170mm and transom of 100mm. Edges narrower beam doesn’t appear/feel to give enough power but on the other hand isn’t as draggy as BOR’s either!!

Hi Mark
you sound just like i was when i first started… draw a boat a year and test the stuff out of it… find out what works and what doesnt…Do you read up on any books?
I looked at the last 2 pics. and saw that you had tumblehome in it… was that on purpose? I tried that on one of mine. and didnt like it. I know they say it faster with it. I just have never found it to be…( personal Opinion)

before moving the weight back? have you tried a heavier rudder? maybe a longer one would help plus it would help in turning the boat???
keep up the good work This is My lastest boat Abracadbra

Hi Cougar
I wouldn’t say I’m an avid reader of yacht design books. I’ve skimmed through the Julian Bethwaite book an to be honest it’s put off them. I do enjoy geometry but the maths modelling, coefficients, reynolds etc etc all seems a bit ostentatious. If the maths and associated software truly worked all hulls would be identical just differing in scale! I tend to keep an open mind. Mother nature didn’t depend on a book or keyboard just millions of years and the odd prototype to develop the vast number different shaped fish, birds animals and mammals in the sea, air and on land that can all go pretty fast. (there some humour here)
I do like tumbleholme. I wouldn’t say it makes a hull faster. In fact it probably produces a little drag. But when the chine digs in and the rig is powered up the boats VMG is much improved. The chine caused by the tumbleholme helps reduce leeway, acting in a similar vein to a surfboard rail. With the Edge I have made the chine even more pronounced by rebating the freeboard. I can’t say I can notice a difference on the sticks but both visually and mentally she is pointing very well at the moment compared to my local competition.
I probably wont try a heavier rudder, but thanks for the idea. So far all my designs have used the same appendages and rigs. This just seems to help me understand the affects that just the hull design is having.
For this weekends District series Championships the wind is forecast to be light <8mph and variable in direction and strength. With this in mind I wont be adjusting the hulls trim as the level at the transom couldn’t be better for the proposed conditions.
You must be happy with your design, if you could make any changes what would you alter first?

And here’s my latest build “Vertex”. A sort of go between, between the BOR and Edge. Since taking these photo’s I have moved the 230g of corrector weight further aft. I have kept a build log here: http://soaring-sailing.blogspot.co.uk/