Bronze Rudder for Westsail 32

[virginia boy]

OK I was considering what to do about replacing a rudder on a westsail 32 without rebuilding with using the existing glass covered foam and had what (I hope) is a stroke of genius.

The W32's rudder is very thick (wider eventhan where it attaches at the hull) and therefore creates a significant amount of drag and is prone to becoming water logged. My solution is to eliminate that big ass rudder and replace it with a much thinner bronze rudder thereby eliminating the drag and solving the water intrusion issue.

Someone suggested that a bronze rudder may vibrate and the cost would be very high? I think it would a uniquely beautiful addition.

Here is a photo of a Westsail rudder so you can see the size and configuration.

[Surveyor]

The weight would give you good reason to carry your spare anchors in the chain locker! It would eventually turn green too...

I think that one of the W32 performance improvements that has been advertised is in fact streamlining the fore edge of the rudder.

Is your W32 on the hard in Virginia? I ask because I want to laser scan the aft 1/3, hull and cockpit, of a W32. From this I can 3D model it and analyze it for possible fabrication of a custom arch/davits/boomkin (I am a land surveyor with a laser scanner). Let me know if this is something you might be willing to let me do. I would share any info I gather and post scan ideas.

[Bloodhound]

There's a very extensive discussion on the rudder topic on the WOA website. You might start by checking out the link http://www.westsail.org/discus/messages/11/201.html?1240090660 which will provide you with a starting point and will lead you to other discussion threads.

[virginia boy]

The weight would give you good reason to carry your spare anchors in the chain locker! It would eventually turn green too...
I would love for the rudder to turn green! It would look awsome with some wooden rudder cheeks on the upper half.

There's a very extensive discussion on the rudder topic on the WOA website. You might start by checking out the link

I have reviewed every article on the westsail site including the rudder discusions (no kidding all of em) and found a lot of info about rebuilding or repairing rudders but nowhere have I heard of anyone even mentioning a metal alloy one.

The reason I ask id that I'm very close to purchasing one, would like to turn it into a one of a kind, creative masterpiece and am trying to figure refit costs.

Should I speak to a foundry about weights and strengths of bronze or who? I'm not so great at engineering. Or if ya ask my wife...not so good at thinking in general. haha

[Jim Cate]

The reason I ask id that I'm very close to purchasing one, would like to turn it into a one of a kind, creative masterpiece . [/QUOTE]

Mate, IMHO adding that much weight that far aft on a W-32 would turn it into a one of a kind disaster, besides putting you into the poorhouse,

Rethink this one yourself, or ask a naval architect for an opinion!

Cheers,
Jim

[klem]

Just a quick bit of estimation here to see how heavy this really would be:
Bronze is ~500lbs/ft^3
Assume the rudder dimensions will be 8'X2'X1"
It will weigh somewhere on the order of 666lbs which is an awful lot. This is certainly not a precise calculation but it gets you in the ball park.

And I would hate to see the cost.

[sycankiz]

I wonder what happened with this rudder idea as I too am considering to do the same out of steel, stainless steel or aluminium.

The rudder of a Westsail 32, including every bit but the bronze pins and the tiller is 70-75 kg. (1 kg = 2.2 lbs) I measureed it on a scale holding all the parts of the rudder that i have taken out and dismantled. It came out as 70 kg but since i've taken the rudder down, sandblasted it down to fiber and split it open and cut the above waterline portion of it off, i had to measure it piece by piece, hence the + 5 kg.

The below waterline area of the Westsail 32 rudder, according to my measdurement on an actual one is 115,000 square cm, which is 123.8 square foot.

Again according to my calculations I can use an 8 mm (0.315 inches) thick steel plate shaped exactly as the original rudder and have the same overall weight of the rudder but just the underwater area. If i use 7 mm thickness i can built the whole thing, above and below water portions and still be in the same total weight ballpark.

Or I can use 5mm (0.197 inches) and strengthen the whole piece by welding horizontal flat bars on each rudder cheek every 15 cm from the top to the bottom, and still have the same weight with the total original rudder.

Stainless steel has the same density with regular steel (actually quite close) but if i go aluminium, i can triple the thickness and go up to 24 mm (0.94 inches) thickness with the same weight of about 70-75 kg (154 to 165 lbs). And this thickness will be an overkill. Density of hot rolled aluminum is 1/3rd of the density of hot rolled steel.

At present I am thinking on how to attach one such steel or aluminum rudder to the W32 using the original fiberglass gudgeons and have the highest structural soundness. I can design a new type of system to attach the rudder to the boat but hey, the gudgeons are there in quite good condition and the holes for those are already drilled into the boat so why not use them, right ?

Any thoughts welcome.

[jimbunyard]

Not sure if it is enough to upset the balance, but foam/fiberglass rudders are buoyant; steel, aluminum or bronze ones are not.

Not sure about your measurement for the size either; 123.8 square feet is almost four 4' x 8' sheets of plywood...

[sycankiz]

Originally Posted by jimbunyard

Not sure if it is enough to upset the balance, but foam/fiberglass rudders are buoyant; steel, aluminum or bronze ones are not.

Not sure about your measurement for the size either; 123.8 square feet is almost four 4' x 8' sheets of plywood...

these are the dimensions of the whole thing. https://www.westsail.org/resources/S...dimensions.pdf

the waterline passes from the top portion of the uppermost notch for the bronze pins. Just below where it says 2 1/2 TYP on the drawing. The rudder is attached to the hull at an angle and sits exactly like it sits in this drawing. The waterline that passes of course passes horizantaly. So below that waterline is the wet part that actually helps steering the boat. That is the area i have calculated.

You are right on the buoyancy issue. The original rudder has some displacement because it has some volume. That displacement needs to be calculated and the new rudder weight must be adjusted accordingly.

[Pauls]

Several points:

First, it is not true that a very thin rudder creates less drag. Specifically, the thin rudder WILL create less drag when it not deflected at all. With any significant rudder angle a streamlined airfoil shape will have less drag and also create more lift (ie turning force). The reason for this is that the thin blade, when dragging thru the water at an angle, forces the water to make a very abrupt turn around the leading edge. This abrkupt turn creates more drag than the gentler, more gradual turn that a thicker airfoil shape makes. Look at serious race boats - they do not have blade rudders.

So there is a balance here, as in all things. Too thin is not good. Neither is too thick. There is an ideal between the extremes.

The cost and weight of a bronze casting will both be extreme. This is NOT a good idea.


You want to build a better rudder. Great. You have a couple good options available. One is to build a new one out of fiberglass. Good craftsmansip and design should make it free from water intrusion problems. Or alternatively, you can weld up a new rudder from steel. Steel will allow you to create any shape airfoil you desire (use120" thick plate, stainless tube/pipe for the pintles). It will never leak.

Probably the simplest solution is to cut down your existing rudder, reshape it as you wish, address the water intrusion areas and reglass. That will save you a lot of trouble and problems. For example, you have 3 pintles to align, and they need to align very well for the rudder to pivot without binding. You can reshape the rudder planform (that I the side view profile) to a more efficient, less drag inducing profile by changing the bottom edge from a radius to a straight, slightly down angled line. This will improve the lift/drag ratio measureably.

Good luck with your project.

[roverhi]

The rudder of a Westsail is against thick deadwood at the aft end of the hull. Just because the forward edge of the rudder is thick does not mean it's creating drag, in fact would probably reduce it compared to a much thinner rudder. The eddy currents of the water rushing aft along the hull would suddenly create a vacuum/drag where the water flow would have to transition from the thick deadwood to the thin rudder. Don't try and reinvent a nice round wheel that works great with a square one whose only benefit will be a lot of money wasted..

Some time before hull 163, ours, the the W32 rudder was redesigned and assume it was by Crealock who originally modified Atkins' Eric/Thistle design for build in FRP. He very well may have used NACA foil shape data to create the proper airfoil shape to make the rudder more efficient. Even if it's water logged it won't add weight to the rudder once it's in the water. Unlike like a rudder with a post like a spade rudder or through hull, there is no metal in it to corrode. Having water trapped inside will only cause problems if the boat is hauled where the water could freeze. Drilling a few holes to let the water out should solve that problem.

Our Westsail was hauled out last year. The 45 year old rudder was in good shape even after three trips to SoPac and daily use for sunset charter for the last 15 years. Our boat had the new rudder design but the old SS Gudgeons. The SS had had some issues and had needed welding and reinforcing. If you've got the FRP gudgeons and they aren't badly worn you are ahead.

Damn got suckered in again. Think I'd learn to check the date of the op's post before jumping in. The guy seems to have disappeared the same day he first posted.

[Vinton]

Hi, I found this thread about rudders and hope this question fits. I just bought a 55 year old Pearson Vanguard; it has a wood rudder. This being the first (exposed) wood rudder on a boat I've owned, it made me wonder about the longevity of it. On the one hand it seems to be in decent shape (and it has lasted 55 years), but on the other - it may go at some point in the future. If it needed to be replaced, I assume the foam/core fiberglass rebuild would be the way to proceed...is that right? If it is, does anyone have a rough idea as to what something like that would cost for a rudder this size (at home/at deck guessing roughly 2 ft x 4 ft, give or take)?