"Accurate foils can easily add 10% to the upwind performance of any boat"
(from http://www.storerboatplans.com/wp/wiki/index/foils-centreboards-leeboards-and-rudders/)
2001 Mac X with SS brackets:
Original rudders: length 49", width 9", thickness @ pivot bolt 1.125"
IDA rudders: length 48", width 10", thickness @ pivot bolt 1.375" N0012 foil
stock 1996 26x rudder:
length 46" width 12" top tapering to 9" at bottom, wide part of rudder starts 19" from end, approx 1" thick 3" from leading edge whole length of board. It is a symmetrical foil not sure what yet but definately one of the desirable naca profiles. Appears early rudder is superior to the later oem ruddder. approx 12" of length is not in water under boat
I read a rule of thumb for rudder area = 1 to 2% of sail area
26x 241ft^2 241ft^2x144in^2/ft^2=34704in^2
so 1%=347 and 2%=694
late stock 49x9=441in^2 and not a good foil reported by others
early 1996 26x rudder is 46"x 10.5" approx, 483 in^2, uncertain foil type but shape is better than the later
ida 48x10=480 in^2 and an optimum foil
one rudder maybe not enough when healed alot
successful oversized Ida rudder area is 12x54=648 in^2
********************************************************
26x rudder info quoted from the net...................
26X Early Vs Late Rudder
The advantages I see:
+ Solidity
+ Stability (Less loose action, noises etc...)
No bending of the brackets
Less drag when motoring. (You can motor fast without braking things)
Sailing
Steering is a lot lighter
The boat tacks faster (in a shorter turn)
Points better but that is also related with the fin or canard (another mod under the hull)
I did the mod because the older aluminum bracket system collapsed...
**********************************************************************
Re: Rudder Enlargement
do you think that the rudders require more of a surface area?
Yes. In light conditions the stock rudders are fine. Once the seas pick up a bit, however, the boat doesn't track worth squat while off the wind. You have a ton of support up front with much of the water ballast, and of course the board, but then you have a shallow super-light displacement bottom hull section which is basically a cork in the water. The bow doesn't get swept by the waves but the stern does, which means more rudder area is needed (or a skeg but I've moved on from that idea.) Also, they're lacking when beating upwind in a breeze. At that point you're not dealing with tracking problems but weather helm. Now rudders won't reduce weather helm and shouldn't be the primary resource to deal with it, however, a properly balanced boat with adequate rudder should be able to beat upwind with helm turned to leeward 5 degrees with the boat sailing straight in the groove. That's using the small amount of weather helm (which is good) to your advantage with rudders generating max lift. I was able to achieve this with my now-broken large IDA rudders (oversized 12" wide by 54" long). With the stock rudders, they need to be turned more like7-10 degrees which is way too much drag and gets them closer to stalling which will cause the boat to round up. Consequently, I'm not sailing as close to the wind as I used to. So at the end of the day, the stock rudder size seems to be too small on all points of sail in breezy conditions with chop or swell.
****************************************************************
ruddercraft macgregor (Ida)
http://www.ruddercraft.com/catalog/index.php?cPath=43
****************************************************************
head of rudder filled with resin
http://s1107.photobucket.com/user/lastgoodbye69/media/Motor/DSCN2508.jpg.html
*****************************************************************
oversized 26M Ida rudders 54"x12"
My upwind problem has been solved. Points great, sails fast, doesn't round up unless I'm not paying attention, other than the rudder failing (broke off at bracket), but hopefully the shorter replacement will do nearly as good of a job.
******************************************************************
Review Date: Thu March 23, 2006
When I purchased this boat I had never owned a boat, pulled a trailer, or sailed. This is an ideal starter boat if you are interested in sailing. It is easy to trailer and rig. One major shortcoming, however, is the factory rudder. It is very poorly designed, resulting in severe weather helm. The boat becomes overpowered and rounds up way earlier than it should. I replaced the factory rudder with an aftermarket one for 250 dollars, and it is an entirely different boat. Much easier to control at all speeds, and the weather helm is almost non-existant. I am very, very happy with this boat and would definately buy one again. It is not a blue water boat by any means, but someone of my experience shouldn't be attempting major passages anyway. I would recommend this boat to others without hesitation, just as long as you replace the rudder.
**********************************************************************
As stated earlier, the rudder is 2 thin fiberglass pieces filled with resin at the head. No real strength. You can see the foam core in the pic.
http://smg.photobucket.com/user/DoubleCross/media/NCSail002-1.jpg.html
**********************************************************************
I had a set of IDA rudders custom made which were larger than what they sell for the Mac
To date, I have broken three rudders. No impact, nothing crazy, just sheer water loads. Well, the first one broke during a broach in a 45 knot gust, but the other two were in moderate conditions, just sailing a straight course. Surmise it to say that plastic rudders, at least in that size just don't hold up. For those of you who own IDA rudders, don't panic. The broken rudders in question were 12" wide by 54" long. Odds are, yours will be just fine. So for the last several months, I've been using the stock rudders and I'm not a happy camper.
**********************************************************************
for anyone who may know .....
Are there any advantages / disadvantages to the early vs. the later rudder designs. ??
My guess would have been that the earlier shorter rudders would be better for shallow water, and with the added surface forward of the pivot, could be balanced better. remember they could be adjusted back some, to fine-tune the balance under load.
But there must have been some rationale for changing to the thinner profile longer rudders, except, ...... was it the dreaded $ ?? (shudder)
It seems on the whole about eight out of ten "improvements" have as much to do with cost savings than performance enhancements. But since I can't see a big cost savings in the new versus the old, in this case I'd guess the deeper rudder has more control surface area in "clean" water below the transom, particularly when one of the rudders is out of the water due to heeling.
Higher aspect ratio is supposedly more efficient - less drag with more lift. So that's why they're taller and skinnier, but it appears their surface areas would be similar. The old brackets couldn't even handle stresses of the old rudder design ... not sure how much the new rudders would increase stress, but at least they should have reduced drag.
I've read of numerous rudder bracket repairs, but always the aluminum version, never the stainless version. The '99 rudder brackets might be the single best example of an "improvement" that really was.
It also puts higher loads on the rudder and brackets, which may explain one of the reasons the cast aluminum brackets were upgraded to (I would guess) considerably more expensive stainless at (approximatley?) the same time.
The earlier rudders did have more fore/aft distance than the late ones. They are also more rounded. The ones on the M are even smaller. My '96 has the larger rudders.
For 2 to 6 knots the foil shape N0012 is best for laminar flow.
Reynolds number increases as chord increases.
eliptical curved bottom retains more laminar flow than flat straight edge.
Stock rudder lacks foil shape and less area is useful 'cause laminar flow is lost.
That's why an Ida is better.
***************************************************************
Keel and Rudder Design
https://www.ericwsponberg.com/wp-content/uploads/keel-and-rudder-design.pdf
http://www.ikarus342000.com/Boardsandrudders.pdf
http://www.pdracer.com/keel/
World's Cheapest Foil Chart for NACA Section Profiles:
http://www.boat-links.com/foilfaq.html
******************************************************************
N0012 Max thickness 12% at 30% chord.
http://airfoiltools.com/plotter/index?airfoil=n0012-il
http://airfoiltools.com/airfoil/details?airfoil=n0012-il
*********************************************************************
make your own rudder
CNC Foam cores
https://www.flyingfoam.com/content/quote-request
can use cheap polyester resin on Expanded Polypropylene but not Polystyrene
N0012, 12% of cord is thickness of foil, symetrical pattern
************************************************************
maddmike 26x keel, quote from the net about his keel
Basically the Keel was modified for the following reasons;
(1) The stock keel can not take a heavy off-shore passage and will eventually fail. Although the good news is that even when this happens you just turn around and go to the closest place downwind. No worry about going bottom side up as the keel is not part of the ballast system. Trying to power upwind in any sea state, even for a short distance (meaning over 20 miles)is not practical and can not be done on autopilot. This happened to me in the Anagada Passage 14 miles West of St. Martin when I hit something(who knows what) at night and it took the keel off. I had to turn around and jib sail to Virgin Gorda.
(2) The stock keel does not let the boat point very well. I replaced the stock keel at Independent boatyard on St. Thomas and as a test tacked upwind through the narrows between St. John & Tortola (usually took the boat 14 tacks to get around to Coral Bay). With the new keel I was routinely able to cut this to 7-9 tacks.
(3) While on a sea-anchor (I use a 9' paratech unit to ride out storms at sea) with the stock keel the boat sailed heavely through the wind (up to 30 degrees), on the new keed the boat stays directly to windward with out any 'sailing'. This has been done n two serious storms, one of which had gusts of up to 70 knots for 4 hrs.
The new keel w/o the 'rotating wing' I use for ballast (even with two stainless steel shafts inclosed inside) actually has negative ballast. The wing on the keel is about 100 lbs.
More later.
Not sure who this will relate to your boat/situation, but here is what I did.
The centerboard is basically a cold mold unit that was shaped from a single 8' x 3/4" marine plywood sheet which was cut in half lengthwise.
The two 4' x 6' sections were then identically shaped with a jig saw and the resulting centerboard came out 7'10" x 24" x 1.5" thick. There is a dog-leg in the design 5' 10" down from the head of the board, this is where the new centerboard extends beyond where the origional centerboard stopped. Thus, for 5'10" the board is 24" W and the remaining 2'that extends to where the origional water ballast intake was, is 15"W. Both sides of the new board were then routed out and 7' stainless steel drive shafts (salvaged from a 33' Sunseeker that unsuccessfully tried to cut across the Beef Island reef near Tortola) were placed inside. The two boards were then glued together and covered with glass & come Carbon-Fiber. Two holes were drilled through the bottom of the board, one for the uphaul line & one for the ballast wing (which 'free floats) so it can remain at a proper attitude as the centerboard is raised and lowered. Inside the centerboard 'slot' was reinforced with aluminum and a stainless steel 'U' housing (not sure what the actual name for this opart is). The result is that even with the board up, it now extends 15" below the bottom (thus, the boat does have a 'Keel"'. I will try to post some photos, but it might take a couple of days as all my shots of the boat out of the water are not here with me in Sri Lanka.
stock 26x centerboard is 761/2"x14"x13/8" = 1071 in^2
Madmike centerboard = 2040 in^2
diff=969
theoretical centerboard area is 5% of sail area or 1728 in^2
so oem is too small and madmike is enough.
possible solution is add leeboards for more area and lift rather than larger centerboard.
**********************************************************
add a leeboard
http://www.pdracer.com/keel/
http://www.boatdesign.net/forums/multihulls/leeboard-question-5944.html
http://www.duckworksmagazine.com/01/articles/leeboards/
for a leeboard max lift? http://airfoiltools.com/airfoil/details?airfoil=s1223-il
http://upcommons.upc.edu/bitstream/handle/2117/27650/15610572.pdf
http://airfoiltools.com/airfoil/details?airfoil=ch10sm-il
http://airfoiltools.com/airfoil/details?airfoil=s1210-il
http://airfoiltools.com/airfoil/details?airfoil=n6409-il
http://airfoiltools.com/airfoil/details?airfoil=naca6412-il
http://airfoiltools.com/airfoil/details?airfoil=s7055-il
http://m-selig.ae.illinois.edu/uiuc_lsat/Low-Speed-Airfoil-Data-V1.pdf
https://www.researchgate.net/publication/245429449_High-Lift_Low_Reynolds_Number_Airfoil_Design
http://docs.desktop.aero/appliedaero/airfoils2/lowresections.html
which profile do you like?
************************************************************
(from http://www.storerboatplans.com/wp/wiki/index/foils-centreboards-leeboards-and-rudders/)
2001 Mac X with SS brackets:
Original rudders: length 49", width 9", thickness @ pivot bolt 1.125"
IDA rudders: length 48", width 10", thickness @ pivot bolt 1.375" N0012 foil
stock 1996 26x rudder:
length 46" width 12" top tapering to 9" at bottom, wide part of rudder starts 19" from end, approx 1" thick 3" from leading edge whole length of board. It is a symmetrical foil not sure what yet but definately one of the desirable naca profiles. Appears early rudder is superior to the later oem ruddder. approx 12" of length is not in water under boat
I read a rule of thumb for rudder area = 1 to 2% of sail area
26x 241ft^2 241ft^2x144in^2/ft^2=34704in^2
so 1%=347 and 2%=694
late stock 49x9=441in^2 and not a good foil reported by others
early 1996 26x rudder is 46"x 10.5" approx, 483 in^2, uncertain foil type but shape is better than the later
ida 48x10=480 in^2 and an optimum foil
one rudder maybe not enough when healed alot
successful oversized Ida rudder area is 12x54=648 in^2
********************************************************
26x rudder info quoted from the net...................
26X Early Vs Late Rudder
The advantages I see:
+ Solidity
+ Stability (Less loose action, noises etc...)
No bending of the brackets
Less drag when motoring. (You can motor fast without braking things)
Sailing
Steering is a lot lighter
The boat tacks faster (in a shorter turn)
Points better but that is also related with the fin or canard (another mod under the hull)
I did the mod because the older aluminum bracket system collapsed...
**********************************************************************
Re: Rudder Enlargement
do you think that the rudders require more of a surface area?
Yes. In light conditions the stock rudders are fine. Once the seas pick up a bit, however, the boat doesn't track worth squat while off the wind. You have a ton of support up front with much of the water ballast, and of course the board, but then you have a shallow super-light displacement bottom hull section which is basically a cork in the water. The bow doesn't get swept by the waves but the stern does, which means more rudder area is needed (or a skeg but I've moved on from that idea.) Also, they're lacking when beating upwind in a breeze. At that point you're not dealing with tracking problems but weather helm. Now rudders won't reduce weather helm and shouldn't be the primary resource to deal with it, however, a properly balanced boat with adequate rudder should be able to beat upwind with helm turned to leeward 5 degrees with the boat sailing straight in the groove. That's using the small amount of weather helm (which is good) to your advantage with rudders generating max lift. I was able to achieve this with my now-broken large IDA rudders (oversized 12" wide by 54" long). With the stock rudders, they need to be turned more like7-10 degrees which is way too much drag and gets them closer to stalling which will cause the boat to round up. Consequently, I'm not sailing as close to the wind as I used to. So at the end of the day, the stock rudder size seems to be too small on all points of sail in breezy conditions with chop or swell.
****************************************************************
ruddercraft macgregor (Ida)
http://www.ruddercraft.com/catalog/index.php?cPath=43
****************************************************************
head of rudder filled with resin
http://s1107.photobucket.com/user/lastgoodbye69/media/Motor/DSCN2508.jpg.html
*****************************************************************
oversized 26M Ida rudders 54"x12"
My upwind problem has been solved. Points great, sails fast, doesn't round up unless I'm not paying attention, other than the rudder failing (broke off at bracket), but hopefully the shorter replacement will do nearly as good of a job.
******************************************************************
Review Date: Thu March 23, 2006
When I purchased this boat I had never owned a boat, pulled a trailer, or sailed. This is an ideal starter boat if you are interested in sailing. It is easy to trailer and rig. One major shortcoming, however, is the factory rudder. It is very poorly designed, resulting in severe weather helm. The boat becomes overpowered and rounds up way earlier than it should. I replaced the factory rudder with an aftermarket one for 250 dollars, and it is an entirely different boat. Much easier to control at all speeds, and the weather helm is almost non-existant. I am very, very happy with this boat and would definately buy one again. It is not a blue water boat by any means, but someone of my experience shouldn't be attempting major passages anyway. I would recommend this boat to others without hesitation, just as long as you replace the rudder.
**********************************************************************
As stated earlier, the rudder is 2 thin fiberglass pieces filled with resin at the head. No real strength. You can see the foam core in the pic.
http://smg.photobucket.com/user/DoubleCross/media/NCSail002-1.jpg.html
**********************************************************************
I had a set of IDA rudders custom made which were larger than what they sell for the Mac
**********************************************************************
for anyone who may know .....
Are there any advantages / disadvantages to the early vs. the later rudder designs. ??
My guess would have been that the earlier shorter rudders would be better for shallow water, and with the added surface forward of the pivot, could be balanced better. remember they could be adjusted back some, to fine-tune the balance under load.
But there must have been some rationale for changing to the thinner profile longer rudders, except, ...... was it the dreaded $ ?? (shudder)
It seems on the whole about eight out of ten "improvements" have as much to do with cost savings than performance enhancements. But since I can't see a big cost savings in the new versus the old, in this case I'd guess the deeper rudder has more control surface area in "clean" water below the transom, particularly when one of the rudders is out of the water due to heeling.
Higher aspect ratio is supposedly more efficient - less drag with more lift. So that's why they're taller and skinnier, but it appears their surface areas would be similar. The old brackets couldn't even handle stresses of the old rudder design ... not sure how much the new rudders would increase stress, but at least they should have reduced drag.
I've read of numerous rudder bracket repairs, but always the aluminum version, never the stainless version. The '99 rudder brackets might be the single best example of an "improvement" that really was.
It also puts higher loads on the rudder and brackets, which may explain one of the reasons the cast aluminum brackets were upgraded to (I would guess) considerably more expensive stainless at (approximatley?) the same time.
The earlier rudders did have more fore/aft distance than the late ones. They are also more rounded. The ones on the M are even smaller. My '96 has the larger rudders.
For 2 to 6 knots the foil shape N0012 is best for laminar flow.
Reynolds number increases as chord increases.
eliptical curved bottom retains more laminar flow than flat straight edge.
Stock rudder lacks foil shape and less area is useful 'cause laminar flow is lost.
That's why an Ida is better.
***************************************************************
Keel and Rudder Design
https://www.ericwsponberg.com/wp-content/uploads/keel-and-rudder-design.pdf
http://www.ikarus342000.com/Boardsandrudders.pdf
http://www.pdracer.com/keel/
World's Cheapest Foil Chart for NACA Section Profiles:
http://www.boat-links.com/foilfaq.html
******************************************************************
N0012 Max thickness 12% at 30% chord.
http://airfoiltools.com/plotter/index?airfoil=n0012-il
http://airfoiltools.com/airfoil/details?airfoil=n0012-il
*********************************************************************
make your own rudder
CNC Foam cores
https://www.flyingfoam.com/content/quote-request
can use cheap polyester resin on Expanded Polypropylene but not Polystyrene
N0012, 12% of cord is thickness of foil, symetrical pattern
************************************************************
maddmike 26x keel, quote from the net about his keel
Basically the Keel was modified for the following reasons;
(1) The stock keel can not take a heavy off-shore passage and will eventually fail. Although the good news is that even when this happens you just turn around and go to the closest place downwind. No worry about going bottom side up as the keel is not part of the ballast system. Trying to power upwind in any sea state, even for a short distance (meaning over 20 miles)is not practical and can not be done on autopilot. This happened to me in the Anagada Passage 14 miles West of St. Martin when I hit something(who knows what) at night and it took the keel off. I had to turn around and jib sail to Virgin Gorda.
(2) The stock keel does not let the boat point very well. I replaced the stock keel at Independent boatyard on St. Thomas and as a test tacked upwind through the narrows between St. John & Tortola (usually took the boat 14 tacks to get around to Coral Bay). With the new keel I was routinely able to cut this to 7-9 tacks.
(3) While on a sea-anchor (I use a 9' paratech unit to ride out storms at sea) with the stock keel the boat sailed heavely through the wind (up to 30 degrees), on the new keed the boat stays directly to windward with out any 'sailing'. This has been done n two serious storms, one of which had gusts of up to 70 knots for 4 hrs.
The new keel w/o the 'rotating wing' I use for ballast (even with two stainless steel shafts inclosed inside) actually has negative ballast. The wing on the keel is about 100 lbs.
More later.
Not sure who this will relate to your boat/situation, but here is what I did.
The centerboard is basically a cold mold unit that was shaped from a single 8' x 3/4" marine plywood sheet which was cut in half lengthwise.
The two 4' x 6' sections were then identically shaped with a jig saw and the resulting centerboard came out 7'10" x 24" x 1.5" thick. There is a dog-leg in the design 5' 10" down from the head of the board, this is where the new centerboard extends beyond where the origional centerboard stopped. Thus, for 5'10" the board is 24" W and the remaining 2'that extends to where the origional water ballast intake was, is 15"W. Both sides of the new board were then routed out and 7' stainless steel drive shafts (salvaged from a 33' Sunseeker that unsuccessfully tried to cut across the Beef Island reef near Tortola) were placed inside. The two boards were then glued together and covered with glass & come Carbon-Fiber. Two holes were drilled through the bottom of the board, one for the uphaul line & one for the ballast wing (which 'free floats) so it can remain at a proper attitude as the centerboard is raised and lowered. Inside the centerboard 'slot' was reinforced with aluminum and a stainless steel 'U' housing (not sure what the actual name for this opart is). The result is that even with the board up, it now extends 15" below the bottom (thus, the boat does have a 'Keel"'. I will try to post some photos, but it might take a couple of days as all my shots of the boat out of the water are not here with me in Sri Lanka.
stock 26x centerboard is 761/2"x14"x13/8" = 1071 in^2
Madmike centerboard = 2040 in^2
diff=969
theoretical centerboard area is 5% of sail area or 1728 in^2
so oem is too small and madmike is enough.
possible solution is add leeboards for more area and lift rather than larger centerboard.
**********************************************************
add a leeboard
http://www.pdracer.com/keel/
http://www.boatdesign.net/forums/multihulls/leeboard-question-5944.html
http://www.duckworksmagazine.com/01/articles/leeboards/
for a leeboard max lift? http://airfoiltools.com/airfoil/details?airfoil=s1223-il
http://upcommons.upc.edu/bitstream/handle/2117/27650/15610572.pdf
http://airfoiltools.com/airfoil/details?airfoil=ch10sm-il
http://airfoiltools.com/airfoil/details?airfoil=s1210-il
http://airfoiltools.com/airfoil/details?airfoil=n6409-il
http://airfoiltools.com/airfoil/details?airfoil=naca6412-il
http://airfoiltools.com/airfoil/details?airfoil=s7055-il
http://m-selig.ae.illinois.edu/uiuc_lsat/Low-Speed-Airfoil-Data-V1.pdf
https://www.researchgate.net/publication/245429449_High-Lift_Low_Reynolds_Number_Airfoil_Design
http://docs.desktop.aero/appliedaero/airfoils2/lowresections.html
which profile do you like?
************************************************************
Last edited: