need rudder shafts

[Hunky]

looking for sources for 1.5" O.D. rudder shafts in stainless. This is for a 30' catamaran and the designer has spec'd out tubing with .375 wall thickness. This is to save weight over solid. I've found 304 stainless, but from what I've read I should avoid that for salt water use and go for 316 or better (aquamet, monel, etc.). These will need to be 6' long each.

I've got in a quote request at pennstainless as it is so far all I've found.

Last resort I can go solid. My rudders are designed as kickup and I've got 1.5" sleaves already built in to the kickup cassettes - so kind of want to stay with that dimension. Suppose I could rebuild them if a good deal on equal strength but smaller shaft shows up. (I had rudders earlier but they were both ruined in a meetup with a runaway barge.)

thanks, JD

[andreas.mehlin]

I would choose AISI 329 over 316. Stronger and better against corrosion

[delmarrey]

Here, make your choice from this... Stainless Steel Alloy Duplex 2202, DX2202 - Continental Steel & Tube Company

I have no affiliation with them. But the metal can be bought from others as well.

If your rudders shafts are always in the water, you'll want the best you can get!

[Hunky]

Thanks guys, sent a quote request. /jd

I should add that these are kickup rudders so could be stored out of water to a degree. Not sure I would always do it though. /j

[UNCIVILIZED]

You're aware that the difference in weight between the specified hollow section, & a solid one is only 1.45lb/ft right? And that's if the shafts don't get any filler or epoxy inside of them. I understand how Kurt is about weight, but...

Is going with a higher grade of G10 an option? Or even G10 made with carbon fiber. And if you ask him about this, you might also inquire about other possible material choices for them as well.

BTW, sometimes you can get "shorts", or off cuts from propellor or engine shops, & or their suppliers, from when they do re-powers. Ditto on some boat manufacturers. And you might try & have any of the afore mentioned type businesses place an order for you, along with their stuff. It could save you some $, & they'll also know more (metal) suppliers too. Including ones who produce semi-custom stuff.

Check with anyone who uses a lot of stainless, & or stainless pipe. Which, a lot of metal vendors would have a list of POC's for this. And odds are good that a shop that does a lot of such work will have off cuts.

When I lived & worked in San Diego, I often did my metal shopping at Handy Metal Mart The San Diego Metal Shop - Handy Metal Mart Though that was ages ago. But give'em a ring.

You might also peruse Professional Boatbuilder's list of advertisers. And if you're building a boat it's a good periodical to read anyway www.Proboat.com

[jimbunyard]

6' x 1.5" solid 316 ss shaft.......................36.5 lbs
6' x 1.5" x 3/8" wall 316 ss tubing.............27.8 lbs

You save 8.7 lbs per side going with tubing, and may introduce corrosion issues, especially with 316L or less corrosion resistant alloys...

[Stumble]

You can use fiberglass (g10) shafts but they require a larger section than stainless does. Frankly I would go with carbon, either filament wound or spiral wrap tubes are now off the shelf options, and while the weight savings aren't critical, it's a lot easier to fabricate a rudder from CF than steel. Realistic prices for CF filament tubes this size are about $125/ft, so not cheap but not all that bad either.

I should have pointed out that the conversion is not size for size comparable. A carbon stock will also need to be larger than a stainless one, just not as much larger than a fiberglass one. A redesign of the rudder would be required. But it isn't all that complicated and I am sure KH could toss one out pretty quick.

[Hunky]

I don't have a lot of room for larger sized shafts in the rudder blade section - though I understand the shaft could probably be tapered at higher cost. My rudder cassettes have 1.5" diameter fiberglass bushings (homemade) that I will have to completely rebuild I suppose for a different dimension. Unless I was to drill them out and add some kind of off the shelf bearing. Alignment issues haunt me when considering that.

So Kurt has said I could go solid shaft and use a smaller diameter for weight saving (necessitating rebuilding those cassettes). I need to post some pics for better explanations of what I have. Here is a general picture from before the crash and I'll maybe go out and get some closeups of the rudder bushing if any ideas about changing the diameter of shaft emerge : https://www.flickr.com/photos/jdory/...7625973914417/

I got a reply back on my quote request from Continental Steel and that person said they don't make tube with .375 wall. I have to assume she meant for 316 grade or higher since I've recently bought some in 304 grade. So if I'm going to go solid, I may try the suggestions about boat yards/builders and propeller shaft cut-offs or the like.
/jd

[Hunky]

Got a quote back from Continental Steel and they said that tube with .375 wall isn't made. I suppose that is the grade because I have some 304 of that dimension. So perhaps I'll look for the propeller cutoffs or other shafts from boatyards/builders as suggested.

My cassettes have home made 1.5" diameter bushings of fiberglass and didn't really want to have to remake those, but could do it. The rudder blade as designed would have trouble with a diameter much over 1.5", unless I drilled it out and installed off the shelf rudder bearings of some sort. Alignment issues haunt me with that idea though.

Good ideas - thanks much! /jim

[delmarrey]

Have you considered titanium round bar? I once made a 4" x 6' rudder shaft for a 43' Kauri wood race boat. It weighed around 120# after machining. Titainium is highly resistant to corrosion and very strong. There are different grades which you would have to ask dealers which is best.

E.g. Titanium Supplier | Buy Titanium Metal | Titanium Processing Center

[Stumble]

Originally Posted by delmarrey

Have you considered titanium round bar? I once made a 4" x 6' rudder shaft for a 43' Kauri wood race boat. It weighed around 120# after machining. Titainium is highly resistant to corrosion and very strong. There are different grades which you would have to ask dealers which is best.

E.g. Titanium Supplier | Buy Titanium Metal | Titanium Processing Center

You can make a titanium shaft, but I wouldn't. While Ti is very strong in tensile applications, it has roughly the same stiffness as aluminium but at twice the weight. Basically a titanium rudder shaft needs to be the same size as aluminum, but will end up twice the weight and probably five times the price.

The only advantage of Ti here would be corrosion resistance, but carbon get you that, higher stiffness, and lower weight.

Now a carbon rudder with titanium fittings is a very nice option.

[delmarrey]

Originally Posted by Stumble

You can make a titanium shaft, but I wouldn't. While Ti is very strong in tensile applications, it has roughly the same stiffness as aluminium but at twice the weight. Basically a titanium rudder shaft needs to be the same size as aluminum, but will end up twice the weight and probably five times the price.

The only advantage of Ti here would be corrosion resistance, but carbon get you that, higher stiffness, and lower weight.

Now a carbon rudder with titanium fittings is a very nice option.

No! I'm sorry but titainium is very stiff. I've made plenty of F4 parts in my life to know. The stuff is hard to machine and will not bend easily. Unlike aluminum, which dents, bends and cracks w/o much effort relatively.

[Hunky]

Thanks for the titanium suggestion but afraid it would break the bank. Still have to buy all hardware, rigging, sails, systems, etc for boat on a limited budget. Kinda scraping by here.

[jimbunyard]

You can get 6' x 1.5 316L cold finish round bar for 177.50 from these people.

Order Stainless 316 Round in Small Quantities at OnlineMetals.com

I've used them for small quantities, and while their prices may not be as good as a local supplier, their willingness to cut to length rather than sell only full length (random 20's) often offsets the higher price...


Also, refineries and chemical plants often replace very high quality pump shafts at specified intervals and turnarounds, if you happen to know somebody in those industries...

[Hunky]

Neato. I'll shop a couple west coast yards for cut-offs and if no go - can fall back on onlinemetals.