Making new style rudder for old style boat

wjejr

Active Member
Thread starter #1
Hello fellow Sunfishers,

As the title of the post says, I am making a new style rudder for my Sunrish which has the old style rudder hardware. Using the class rule book and drawing it all out, when I measure the angle between the leading edge of the rudder and the perpendicular line of the transom the angle appears to be 30 degrees. Does anyone happen to have that measurement handy. I suppose it really doesn't make much of a difference as none of it will be class legal, but I was curious.

Interestingly, my old rudder seems to be swept back much more. At first I thought the rudder hardware might be the difference, but the swing down plate seems to be parallel to the transom.

Thanks in advance for the help.
 

Webfoot1

Active Member
#2
It's 120 degrees between keel and leading edge of the rudder. If the rudder was vertical it would be 90 degrees so sweeping back
the rudder would add another 30 degrees for a total of 120 degrees. I think you have the correct angle already using your method.
The old rudder did have a bit more sweep. If you get a chance, switch to the new style rudder mount, it worth the effort in every
way.
 

wjejr

Active Member
Thread starter #4
I have seen the 120 degree angle both here in the forum and in the rules directly. The thing is that the bottom of the boat from which they make that measurement isn't 90 degrees to the transom nor is it straight. As we all know the bottom of the sunfish is curved making the measurement more difficult than say a Laser whose bottom is flat. Since the bottom curves downward from the transom, it would seem the angle of the rudder should be greater than 30 degrees.

Any thoughts?
 

Webfoot1

Active Member
#5
I've built two rudders using the above mentioned plans and a protractor and
they came out just fine. Other methods would be to use a transparency projector
to scale up the plans, draw them in a CAD program or find a existing rudder to
trace over. The rudder could be anywhere between 90 degrees and 120 degrees
and you would not loose any effectiveness. You have a lot (30 degrees) of leeway
to play with. I did lay a old rudder that someone made over what I drew up on
my wood blank and they matched exactly. I assume the old rudder was copied
from a factory original.
 

signal charlie

Well-Known Member
Staff member
#6
Did you look at the specification diagram? Sunfish Specifications | SailingForums.com

It says 120 degrees minimum, that is a class rule. The angle off a plumb transom will in fact be more than 30 degrees. Since you aren't worried about class legal you can make it vertical if you want, which is still debated as being more efficient. Or measure the angle between the transom and keel, let's say it is 15 degrees, and add 30 to that to come up with a 45ish degree angle. Or take the angle off of the diagram with a protractor. Or TLAR it (That Looks About Right). Take it off the old rudder if it was OEM. Or WAG it. Or SWAG it.

Have fun! Pics or it didn't happen!

Cheers
Kent
 

Webfoot1

Active Member
#7
Wooden rudder is useless for racing using the factory cross-section shown on the plans.
Guaranteed to go Braaaattttttt. . . every time. Giving it a true airfoil shape would help
more than the rudder angle.
 

wjejr

Active Member
Thread starter #8
Wooden rudder is useless for racing using the factory cross-section shown on the plans.
Guaranteed to go Braaaattttttt. . . every time. Giving it a true airfoil shape would help
more than the rudder angle.
Yes, that's the plan. Of course that complicates things a bit as the rudder isn't the same width from top to bottom.
 

wjejr

Active Member
Thread starter #9
I have been out of the country for two weeks, so rudder progress had been slow. I got going again today, and I thought I would share my progress.

I drew up the new rudder to scale on a piece of newsprint in pencil before I left, but I did not post, as the pencil lines did not show. I went over the plan today in ink so that everyone could see. Here it is:
 

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wjejr

Active Member
Thread starter #10
The next thing to do was to put an edge on a rough sawn mahogany board with the jointer, but first checking to see if the fence was square to the table. It was
 

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wjejr

Active Member
Thread starter #11
I want to make sure the rudder doesn't cup or warp, so rather than cut the shape from one piece, I am cutting the board into 2"+ strips on the table saw. Then I will glue the strips together to make a stronger more stable rudder.
 

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wjejr

Active Member
Thread starter #12
I then ran the strips through the thickness planer. I took off only a very small fraction on each pass, as I want to be sure when I am done I am at 3/4" thickness.
 

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wjejr

Active Member
Thread starter #13
Once the strips were cut, I made marks on the boards. The purpose of that was so that I could flip every other board over and have these boards also run lengthwise the other way. The idea is to make the board more stable.
 

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wjejr

Active Member
Thread starter #14
The last thing I did today was to run the strips on the jointer to get the cleanest edge possible, then I laid the rudder plan on top.
 

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wjejr

Active Member
Thread starter #15
I then ran the strips through the thickness planer. I took off only a very small fraction on each pass, as I want to be sure when I am done I am at 3/4" thickness.
The boards are now 13/16". I will lose that 1/16 overage later on.
 

wjejr

Active Member
Thread starter #17
H i everyone,

I thought you would be interested to see how the rudder I am building compares to the rudder I am replacing. The old rudder, circa 1971, was in tough shape. Where it was cracked I cut a kerf with the radial saw and then epoxied in shims. The outside edges were terribly splintered and to fix that I eopxied them together, best I could, and then used a hand plane and rasp to but to get back to solid wood so that I could varnish. How much of the rudder had been abraded away before the I was given the boat.

It was interesting to lay the old rudder over the drawing I made for the new rudder. The new rudder is much bigger as you can see. I am curious to see if I notice any difference when sailing. I also will be fairing the blade into a proper foil shape so that will likely have an effect as well.
 

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Webfoot1

Active Member
#18
The rudder will work better but the old style bracket may not. You may
find it "pops out/up" more often when under sail. The original bracket has problems with
the faster speed of racing sail/dagger-board/rudder.
 

wjejr

Active Member
Thread starter #19
The rudder will work better but the old style bracket may not. You may find it "pops out/up" more often when under sail. The original bracket has problems with
the faster speed of racing sail/dagger-board/rudder.
Hello. That's interesting. I have never had a problem with the rudder popping up, but I have read here that others have. I guess I will find out when this project is done.

I have personally never seen anyone use the new style rudder with the old style bracket, but I am sure it has been done. Have you ever used or seen anyone else do this? I don't know much about much, but I have never have heard that the manufacturer ever produced the new rudder/old bracket combination. Am I mistaken?
 
#20
I don't know much about much, but I have never have heard that the manufacturer ever produced the new rudder/old bracket combination. Am I mistaken?
Well, at my age I don't know about much anymore either, but your comment caused what gray matter I have left to sputter to life. Back in 1972 or so, Alcort, who made the boats back then, started selling replacement blades for the old style rudder that had the new shape. A number of them have been sold on the board - here is an example Old Style Sunfish Rudder Assembly A | SailingForums.com

You will notice they also offered a reinforced rudder head - both were improvements but nothing near as good as the new style rudder fittings.

Why did you make a bigger rudder blade? More blade = more drag. You want the rudder as small as possible while still being effective. That is one thing I still remember at my age.

It will be interesting to see if you notice a difference with a hydrofoil shaped blade. That is one thing I have never heard of anyone trying.

Gotta go. Time for my evening spinach, cod liver oil and Geritol! TUM
 

wjejr

Active Member
Thread starter #21
Why did you make a bigger rudder blade? More blade = more drag. You want the rudder as small as possible while still being effective. That is one thing I still remember at my age.

Thanks you for your advice and for posting the pictures.

Since I am making the rudder to the new shape, I decided to make it to the new shape's dimensions. No other reason. Practically, it seems a good thing to have the rudder deeper in the water for a couple of reasons, and I would imagine that the rudder with the proper shape will act as a lifting surface and a least partially negate the slight increase in area.

I have a second set of hardware to put on the new rudder, so it should be easy to compare.
 

Webfoot1

Active Member
#22
I always give mine a airfoil shape just because. If you want to go all the way, leave the
trailing edge squared-off. With a rounded trailing edge there is flow separation about
two-thirds of the way towards the rear of the rudder on each side. With a square trailing
edge you get a vortex bubble that delays the separation. Hopefully, you will not get vibration.

There is one of those old bronze brackets on Ebay. Personally I'd put the money towards a new style bracket.
 

wjejr

Active Member
Thread starter #23
I always give mine a airfoil shape just because. If you want to go all the way, leave the
trailing edge squared-off. With a rounded trailing edge there is flow separation about
two-thirds of the way towards the rear of the rudder on each side. With a square trailing
edge you get a vortex bubble that delays the separation. Hopefully, you will not get vibration.


There is one of those old bronze brackets on Ebay. Personally I'd put the money towards a new style bracket.
On the trailing edge:

I will squaring off the trailing edge as you suggest. Thank you for that advice.

I am planning to model the foil shape based on the rudder that I have for my Laser. It won't be perfect, for one thing the chord length varies in the new rudder configuration, but it's supposed to be a fun project for an old (1971) non class legal boat and not for use in the Sunfish World's.

On the bracket:

The thing of it is, is that I already have the additional hardware for a second rudder, which I picked up on eBay a couple of years ago, just checked, for $9.95. The original hardware stays with the old rudder and will be used when I sail with my children. That rudder has the original length wood extension connected to the tiller, and I find that the short extension helps on cockpit space. For the new rudder, I plan to add a longer extension and use that configuration when I sail alone.

Again, I've sailed the boat in a lot of different conditions and have never had a problem with the old rudder hardware. Maybe I am doing something wrong? :)

It's certainly possible that with the new rudder, something may change, but right now the only advantage I see in the new rudder configuration is that the rudder locks in the upright position. That's certainly a great feature, but it's only been a minor annoyance in the places I sail. When I consider the amount of money it would take to convert both the old and new rudders to to the new configuration, I am guessing I could probably buy another boat.
 

wjejr

Active Member
Thread starter #24
Hello fellow Sunfishers. Here are some pictures of gluing and clamping the boards. I'm using MAS epoxy with wood flour as a thickener. Together they will form the blank from which the rudder will be cut.

1 Gluing 2 D.JPG 2 Gluing 2 before clamp D.JPG 3 Gluing 2 start clamp D.JPG 4 Gluing 2 finished clamp D.JPG 2 Boards Glued D.JPG 3 boards glued D.JPG
 

Webfoot1

Active Member
#25
The old rudder bracket clips into the fitting on the keel. The keel fitting
has a pocket where the edges wear out. You may have hardware that is
in good shape. If it works fine no worry's.

What I did was wait for the cast aluminum version of the new rudder bracket to show
up on E-Bay. Maybe I got lucky as I don't see them come up all that often. Someone
on the forum might have one to sell, they are worth about $45. Buying tiller straps/springs
/transom mount etc. I think had about $100 invested not counting labor to do the
wood work.

The new bracket actually locks the rudder in the down position. There is a angled part
of the tiller strap that fit over a angled part of the rudder mount. Works as long as
the tiller is not lifted up.
 

wjejr

Active Member
Thread starter #27
The next step was to start shaping the rudder into a foil. One challenge with the sunfish rudder is that the chord length varies. Being a bear of little brain, I never though much about it before, but I now know why blades tend to have a constant chord. There seemed two options. Option 1 was that if I wanted to use the same foil shape across the rudder top to bottom then I would need to taper the thickness: thicker at the top and thinner at the bottom. Or option 2 was to vary the foil shape. With a thinner foil at the top and a fatter one at the bottom. I chose option 2. I decided to use an NACA 0008 foil at the top, transitioning to a NACA 0010 foil at the bottom. I chose the 0008 foil as it worked with the general dimensions of the rudder where it is widest and the 0010 foil that worked best with the bottom of the rudder.

Once I decided on the shape, the next challenge was to start shaping the board. I decided the best/easiest way was to use my table saw with s dado stack. I tilted the stack 3-4 degrees and used a cutout profile so I would know how deep the cup should be. That's the picture of the paper foil glued to the stick.

Running the blank through the table saw proved a challenge since the foil shape is only starts below the head. I first made a full size model out of piece of pine and then made marks on both the blank and the saw fence so I would know just how far to go. That whole process worked remarkably well, but you may be able to notice that the trailine edge at the bottom is too fat. That's because of the changing chord. Where the chord is widest at the top, the trailing edge is thinner.

Next step is to start refining the foil shape top to bottom.

I have to admit, I did think about just putting bevels as the plans show, but where's the fun in that? Besides there's 14 inches of snow on the ground. :)
 

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wjejr

Active Member
Thread starter #29
If you had started with a larger blank, wouldn't a "pie cut" solve that problem?

View attachment 22035
Thatnk you for the suggestion.

The blank is large enough to do that, but I think it is easier to just run it through the table saw against the trailing edge. Because the 0010 foil is fatter, so in theory at least, it should not interfere with the 0008 foil further up the rudder.
 

wjejr

Active Member
Thread starter #30
As I am making this up as I go along, I decided to cut the blanks trailing edge leaving a little extra for the final trim. I ran my test blank through to see if I had the angle correct which I did. I thought I needed a little more width, so I just moved the fence over 1/4 inch. I then ran the good rudder blank through which left 1/2" Now I have just about 1/2 extra on the trailing edge.

The line on the yellow tape running lengthwise is where the maximum thickness of the foil will be.
 

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wjejr

Active Member
Thread starter #31
I am further ahead on the rudder than on posting, but the next step was to start shaping the the foil/rudder from the bottom where the cord is smaller.

1. I will be using a dado stack on my table saw tilted at about ~ 4 degrees. Because the chord is fatter at the trailing edge, the theory is that when I start the cut, the dado will cut less and less as I move up the rudder and eventually not cut at all.
2. The Foil Stick picture shows the NACA 0010 foil cutout that is glued to a scrap piece of wood using spray adhesive. I use a backer block when I run it through the stack so the paper cuts neatly
3. Shows the same stick with the dado cuts. I lower the blade a little each 3/4" that I move the table saw fence to the right.
4. The tricky part is knowing how far to cut. To do that I put reference marks on the fence and on the rudder blank. Feeding the rudder bottom first was easy. Cutting the other side was a bear as the board wanted to feed back be. S
5. Shows the dado stack and rudder blank.
 

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wjejr

Active Member
Thread starter #32
Now comes the task of final shaping. Running through the table saw with the dado head attached roughed out the shape, but a lot of work remains to get to the final shape. Not being sure of what the best tool to use, I tried them all. I used a #2 hand plane and a flat spoke shave to take out most of the dado blade marks. The problem was that where the rudder transitions into the rudder head it's hard to use smoothing planes. Here I used a round spoke shave, a low angle block plane and a shoulder plane. I also used a rasp, chisels and an old Stanley #20 gouge. Each of these tools had its advantages, but none were perfect. The result of fussing about with all of these tools is in Picture #9.

After using the planes, I started sanding with a large autobody sanding block. I started with 100 grit and for now finished with 120. I don't want to go any further since there is still work to do forming the leading edge.

If I ever make another rudder, I will be more careful in the rough shaping so that I do not have to remove as much wood, and that the transition to the rudder head is perfectly lined up.
 

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#34
Did you try talking to John at J.O. Woodworks? I think he randomly posts on this forum...
He has been making wooden Sunfish parts for years - might be able to give you some tips and tricks.
J.O. Woodworks

(Might be too late at this point...)
Oh, and I'm jealous of some of your woodworking hand tools!
 

wjejr

Active Member
Thread starter #35
Would two passes by a stationary router make the leading edge you want?
Thank you. Yes, and that is exactly what I am planning. I bought a panel raising bit when I first got the boat and used that when I rebuilt the daggerboard. I will use that same bit for this project. Remarkably it is almost a perfect match for the foil shapes.

The router table is already set to go. I just need to find the time and the courage to proceed. :)
 

wjejr

Active Member
Thread starter #36
Did you try talking to John at J.O. Woodworks? I think he randomly posts on this forum...
He has been making wooden Sunfish parts for years - might be able to give you some tips and tricks.
J.O. Woodworks

(Might be too late at this point...)
Oh, and I'm jealous of some of your woodworking hand tools!
Thank you for your suggestion. You are right though in that I am getting towards the end of the project. The rudder shape looks good and feels right when you run your hand across it. I have found it challenging to have the back of the foil gently curve. I used the #2 plane for this reason as the blade is fairly narrow. When I got to the block sanding, I used the larger size and purposefully tried to have the block curve rather than lie flat. The block sanding really helped, although I am sure it is not perfect.

On the hand tools, thank you. I just wish I had more time to use them. :)
 
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