Ok, Most of you guys know I dont touch IOM’s [:-yuck]
But:
Does anybody know what sections are usually used for IOM rudders and keel struts, Is it just a random ‘cos it looks fast’ section, good old NACA 0010 or another? Just though playing with foil sections could give some much bigger gains than messing with hull shapes at the level the top guys play at. For example you could use different sections in fresh water than you do in salt, and I bet you could find a potential gain or two, might not be huge, but you never know! Cant see me buying a couple of IOM’s to test it but might be worth playing with for somone…
matt
the keels are around 50 % of the lenght of the hul. so around 50 cm . the rudder is put as far aft as possible. my IOMs have the rudder around 85% from the front. as for naca number. i am still playing with that. i have found out that it make a big difference, in turning and straight line speed.
i hope this helps. we can talk over skype. if you want
cougar
long live the cup and cris dickson
<blockquote id=“quote”><font size=“1” face=“Verdana, Arial, Helvetica” id=“quote”>quote:<hr height=“1” noshade id=“quote”>Originally posted by Matthew Lingley
Does anybody know what sections are usually used for IOM rudders and keel<hr height=“1” noshade id=“quote”></blockquote id=“quote”></font id=“quote”>
Graham Bantock uses sections he commissions from a foil designer, giving a design brief of the target CL he wants, ie the width of the drag bucket. Designer uses XFOIL amongst other tools to optimise the section for the appropriate Reynolds numbers. Bantock reckons that appendage design (incl. bulb) has resulted in much greater relative performance increases (around 10 times) than improved hull lines.
I thought he would be doing somthing along those lines! I was trying to find an area of the boat that hasn’t been developed to the limit, but as you cant play with the rig there really is nothing new that you can do, apart from optimising to different conditions. What do the rules say about planform shape of the rudder/keel, how far has that been pushed (if it can be at all)?
<blockquote id=“quote”><font size=“1” face=“Verdana, Arial, Helvetica” id=“quote”>quote:<hr height=“1” noshade id=“quote”>Originally posted by Matthew Lingley
What do the rules say about planform shape of the rudder/keel, how far has that been pushed (if it can be at all)?<hr height=“1” noshade id=“quote”></blockquote id=“quote”></font id=“quote”>
The IOM class rules treat appendages very freely. Apart from weight and draft limits, you can pretty much do what you want. Do you have anything in mind for an interesting planform?