I'm preparing to fabricate my rudder(s) for the boat and was curious to know how thick you rudder is. 1/2"? 3/4"? 1"? 1 1/2"? A general concensus would help a lot. I am especially interested in the 26 rudders also.
How thick is your rudder?
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what type of design?
As mentioned, IdaSailor's foil-type rudder is 1.5" on the leading edge. Are you planning on copying that design or fab a conventional rudder which is significantly thinner and "flatter" overall?
As mentioned, IdaSailor's foil-type rudder is 1.5" on the leading edge. Are you planning on copying that design or fab a conventional rudder which is significantly thinner and "flatter" overall?
conventional rudder?
I was thinking of going with a 1 1/2" thick rudder however; a friend of mine swears 1/2" would be fine any suggestions?
I was thinking of going with a 1 1/2" thick rudder however; a friend of mine swears 1/2" would be fine any suggestions?
rudder dimensions
The material you make the rudder from is going to have a lot to do with determining the thickness. Did you want a rudder that floats, but not too buoyant? Do you want adequate thickness for strength and enough thickness to shape the foil? Did you want the ability to thin the trailing edge without the TE being weak? Enough strength in the material to resist damage at the bolt holes? Ability to fit current rudder head without too much modification? When your rudder flexes under load, will it break across the attach points? Resistance to water immersion and saltwater corrosion? And finally, will the rudder shape you come up with actually perform any better than the original? If you break your rudder, will you have an incredible amount of money in time and materials, and be back at square one?
The material you make the rudder from is going to have a lot to do with determining the thickness. Did you want a rudder that floats, but not too buoyant? Do you want adequate thickness for strength and enough thickness to shape the foil? Did you want the ability to thin the trailing edge without the TE being weak? Enough strength in the material to resist damage at the bolt holes? Ability to fit current rudder head without too much modification? When your rudder flexes under load, will it break across the attach points? Resistance to water immersion and saltwater corrosion? And finally, will the rudder shape you come up with actually perform any better than the original? If you break your rudder, will you have an incredible amount of money in time and materials, and be back at square one?
Rudder thickness
My ida rudder is 1-3/8" thick..for my 74 Venture 25..PS far better than the old wood rudder
My ida rudder is 1-3/8" thick..for my 74 Venture 25..PS far better than the old wood rudder
well I'm not sure
I had planned on sandwitching two 3/4 inch plywoods together with epoxy, then getting my foil shape and covering it all in epoxy and fiberglass. I'm still looking at the exact shape etc. suggestions are welcome.
I had planned on sandwitching two 3/4 inch plywoods together with epoxy, then getting my foil shape and covering it all in epoxy and fiberglass. I'm still looking at the exact shape etc. suggestions are welcome.
Get a 2 x 12 and experiment.
My Venture 21 had a 1 1/2 inch thick rudder. The boat is so old, this may well have been the 4th rudder, and I have no idea what the original looked like. My solution was to make a replacement rudder out of the Spruce or Fir construction lumber available at my local Lowes or Home Depot (coincidentally 1 1/2 inch thick). It is cheap, easy to work with, and lends itself to quick experimentation. You could get a 12 foot length and make yourself 3 or 4 different rudders in a Saturday and try them all. When you hit on the right combination, get some real marine materials and make it right (a great wintertime project). My engineer's eye tells me to make it wing shaped, rounded in the front, and and tapered toward the rear. Doug
My Venture 21 had a 1 1/2 inch thick rudder. The boat is so old, this may well have been the 4th rudder, and I have no idea what the original looked like. My solution was to make a replacement rudder out of the Spruce or Fir construction lumber available at my local Lowes or Home Depot (coincidentally 1 1/2 inch thick). It is cheap, easy to work with, and lends itself to quick experimentation. You could get a 12 foot length and make yourself 3 or 4 different rudders in a Saturday and try them all. When you hit on the right combination, get some real marine materials and make it right (a great wintertime project). My engineer's eye tells me to make it wing shaped, rounded in the front, and and tapered toward the rear. Doug
Round the leading edge
I recently switched from the stock MacGregor 26-D rudder, which has a relatively sharp pointed leading edge, to an Ida Sailer rudder which has a round leading edge. The difference in handling weather helm tendencies is amazing. The stock rudder was stalling under heavy rudder loading (meaning smooth flow around it was replaced by turbulent flow which cuts it's effectiveness drastically) and allowing the boat to turn into the wind. The Ida rudder has much less of that problem. Look at the cross section shape of a light airplane wing. There is little if any sharpness to the leading edge. That reduces flow detachment tendencies at high angles of attack. That's what you need for your rudder. Also if you can put say 15% of the rudder area ahead of the rudder pivot axis that will reduce the effort required on the tiller without losing too much feel for what the boat is experiencing. P.S. The profile of the preceding post is too sharp at the leading edge.
I recently switched from the stock MacGregor 26-D rudder, which has a relatively sharp pointed leading edge, to an Ida Sailer rudder which has a round leading edge. The difference in handling weather helm tendencies is amazing. The stock rudder was stalling under heavy rudder loading (meaning smooth flow around it was replaced by turbulent flow which cuts it's effectiveness drastically) and allowing the boat to turn into the wind. The Ida rudder has much less of that problem. Look at the cross section shape of a light airplane wing. There is little if any sharpness to the leading edge. That reduces flow detachment tendencies at high angles of attack. That's what you need for your rudder. Also if you can put say 15% of the rudder area ahead of the rudder pivot axis that will reduce the effort required on the tiller without losing too much feel for what the boat is experiencing. P.S. The profile of the preceding post is too sharp at the leading edge.
Thanks for the response...
JVB, it sure sounds to me like you are describing the rudders used on the "Junk" ships of the orient. I've read in many places their rudders are superior when sailing. thanks so much!
JVB, it sure sounds to me like you are describing the rudders used on the "Junk" ships of the orient. I've read in many places their rudders are superior when sailing. thanks so much!
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