OK, I'd like to challenge the reasoning behind the standard set up for rudders on the Hobie 16 in particular and any asymetic hull cats in general. The 'norm' seems to be to set the rudders for 3 -5 mm of toe in, this is given by both the people 'in the know' and in texts such as Rick and Mary's cat racing for the 90s, (yes I'd like to hear Ricks thoughts if your reading this).
To me this doesn't make sence, the texts say the toe in lets the windward rudder cut through the water with minimal drag as the leward rudder is angled slightly (tracking) to windward countering the sideslip. So here's my arguement to leave the rudders parallel.

A) Asymetric hulls have more sideslip than boarded designs therefore parallel rudders should help provide more resistance to the slippage. ie both rudders are working insteaqd of one.

B) The more the sideslip is resisted the lesser the amount of rudder 'angle of attack' should be required hence less drag.

Naturally I'm wrong as everyone toes them in but WHY?

Cheers Phil

107902 "Philthy Habits"

Try measuring the rudders toe in with the main sheeted in block to block.
Then compare this measurement to the one above with the main loose.
Depending on how stiff the boat, this measurements varies with the same
order of reverse magnitude. (bows toe in, sterns toe out)

You seem to have 'Cat Racing for the nineties'. Most of the information is given in the book, but you have to read carefully in several places to get the complete picture. Be sure to read the information on 'Ruddertrack'.

It's the effects of weather helm instead of side slippage that brings up the whole issue of Toe-in. It's not used to correct mechanical deficiencies, or to correct for loading problems, or phases of the moon, etc, etc. It's weather helm.

Correct me if I'm wrong but the top skippers (say Figueroa) in the H16 class
go up and down wind with with one rudder? (req's practice)

Try sheeting in & out the main on a H16, and measure how much the rudder toe in changes?
(on some boats its more than an 1/8")

Vs the Tornado (a very STIFF boat) use both rudders.

The deal with toe is is because there allways is alittle amount of slop and having a toe in the rudders are under a small amound of presure and that pushes them out and with out any movement that stops the problem with weather helm and having the rudders to stall. We all know hoe bad that is.

Discussions about Rudder toe-in always seem to open a big can of worms. While some mechanical conditions can effect rudder alignment, it doesn't explain why so many sailors in so many different classes use rudder toe-in. Folks liken rudder alignment to reasons automobile front ends use toe-in. This could be some of the truth, but not the whole story. It's been said that 16 bows can tow-in 2 1/2 inches under sheet tension before they're considered too sloppy for competition. This could effect the distance between the sterns and effect rudder alignment, but it's not the big picture. This subject probably comes up a little more with the asymmetrical boardless cats, but lots of different boats use toe-in for different reasons. However, it seems the most consistent reasons are - the leeward rudder does the work, and the windward rudder becomes a surface piercing foil.(similar to going up and down with one rudder, with less practice)

This same discussion popped up in the 'Open Forum' not too long ago. Search open forum for 'Rudder toe in)

There's been tons of discussions concerning toe-in in the 14-16 forum as well.(do search for Toe-in, toe in, etc.) Some of the contributing discussions in 'Cat Racing for the 90's also mention toe-in for their class of boat.(at end of book)

I think Bogie the question is why would you want that windward rudder as a surface piercing foil?, couldn't it be more useful in resisting the "rudder track", "weather helm", "sideslip" etc just the same as the leward blade?

Also yes I know some people advocate pulling up the windward rudder and yes I agree if its only surface piercing and not creating lift then why bother with it.
Phil

a lot of sailboating has evolved thru trial and error, sometimes theory has to catch up with practice. if the guys in my fleet are beating me upwind i try to find out why and duplicate their setup. my guess is thats why so many racers in h16s use 1/8"-1/4" of toe in. because it works. we dont have to know why it works, we just have to go fast.

I think it really comes down to the sailor because one might have more weight on the strings and dont have to worry about dropping thetravelor and just pull the main sheet on and some might have the travelor off and main on or something like that. A better example is some sailors pinch and some foot off and why do they do it because it works for THEM!!

This is one of those questions (like mast rake) where there are many different answers. All of them are probably true to some degree. I think the predominant factor is explained well by Mitch Booth in his Hobie Tiger tuning guide.

“Most boats sail with some weather helm on the rudders and subsequently you have to pull on the tiller slightly to keep the boat in a straight line going up wind. This means that you could have a few degrees of turn on the leeward rudder that is fully loaded, however the windward rudder that has very little load will only cause drag if it’s not in line with the windward centerboard.”

The way I think about it is a little different but not much. When you heal up the windward rudder has a reduced aspect ratio and becomes much less efficient as a lifting foil. For that reason you want to align it in the direction that the boat is traveling to reduce the drag. This is probably why people lift the windward rudder.

Transfer this logic to a Hobie 16 that has lots of weather helm and sideslips more than most boats and you can understand why we sail with so much-toe in.

slop is where its at we all have to re design our boats because tolerances are rec boat specs and one design is a myth all competitive sailors learn the lore and stay in tune