PDA

View Full Version : Rudder post construction/hardware?



Art Read
03-18-2002, 04:41 PM
Thinking ahead a bit to how I'm going to hang my rudder, (after I figure out how I'm going make it...) and I need a little advice. My "vague" plan is to incorporate a solid bronze rod, maybe 1 or 1 1/4 inches diameter into the leading edge of the rudder itself as the rudder post. This would be "captured" by bronze straps serving as "gudgions" with similar straps above them serving as the "pintles". (This appears to be vaguely what the plans show... Not a lot of detail there.) The top of the post would then pass through a pipe of some sort set flush with the hull at the trailing edge of the keel and finishing off at the deck. I'm thinking I'll have to get some sort of flanges fabricated to match the various angles where the pipe will pass through the keel and the deck. And I assume I'll want some sort of "bearings" fitted at the two ends of this pipe as well? Any ideas on what to use there? My other questions are: Is pipe like this available in silicon bronze? I've never seen it any of the usual places, and just called Alaskan Copper & Bronze here in Seattle. The guy I talked to didn't seem to know about it either. If not, what would be the best substitute? Copper? What wall thickness would I need? How much "play" between the inside diameter of the pipe and the rudder post should there be? Second: What would be the best approach to tying the bronze rod "post" itself to the rudder? I've seen perpendicular "drift" like appendages brazed(?) to the rod and let into the rudder. And I think I've seen the bronze straps that function as the pintles serving a similar purpose. In other words, they and the rudder post move as one, securing the rudder, and rotate inside the straps that act as the gudgions. Is this "feasible"? Where can I get work like this done localy? Also, any ideas re: a heel piece/pivot? It seems it would be a good idea having something keeping the lower end of the rudder secure, (and stray crabpot warps out!) but I have no idea what to look for or where to find it. My original idea was to just use "off the shelf" rudder/pintles in the appropriate sizes and then "capture" 'em with wooden plugs in the cutouts on the rudder's leading edge after installing the rudder. But I'll still need some way to secure the post itself to the rudder. I've even collected a few odd sized pintles with this in mind. But I'm not having much luck finding real "strap" gudgions to match 'em. Any thoughts, suggestions or warnings folks?

(This is a picture from when I was "roughing out" the deadwood to give you an idea of the keel/rudder configuration...)

http://www.imagestation.com/picture/sraid29/pc8cb97c53f37afb918a5d4083ddc5c1c/fdef50b2.jpg

[ 03-19-2002, 10:56 PM: Message edited by: Art Read ]

Thad
03-18-2002, 05:54 PM
Generally with this setup the "post" is drilled and drifts are driven through the post into the rudder. These serve to tie the pieces together as well as providing the turning moment to the blade. Straps can be laid around the post and let into the rudder but the connection between the strap and the post might not add much to the mix, though it might work to keep everything where it should be. If you had a strap on the rudder just above the gudgeon strap to the stern post/deadwood it might act as a bearing.
You might have to use brass for your pipe, it should be available. Often these were threaded and turned into the keel and a block on top of the keel. Other builders brazed flanges onto the pipe which could be screwed to the keel. A block of oak under your deck should work for a bearing. Another approach would be to block the keel to provide a surface square to the shaft and then fit a stuffing block flange and tube sized to your shaft.

Jamie Hascall
03-18-2002, 09:40 PM
Art,

When I replaced the stern tube on Victoria, I was forced to use red brass because I couldn't find bronze at the time (grrr). However a quick look in my Alaskan Copper catalog shows SAE 660 bearing bronze hollow bar stock in sizes that should work as well as 90-10 copper nickle tubing that should work. I imagine both are pretty pricey. I've got a guy working with me who is set up for TIG welding bronze and should be able to do this kind of fabrication for you. (He's also a wooden boat liveaboard so he's got a sympathetic nature.) I'm sure we can come upwith a good design. Bring pictures and some sketch paper to PSEBS and if we talk about it early in the evening you should be able to get some valuable input. Later, who knows ;) .

Jamie

Art Read
03-18-2002, 11:22 PM
Good idea, Jamie! I hadn't thought to take advantage of the collected wisdom there. I promise not to drone on and on about it all evening... The rest of your message about Alaska's catalog sounds encouraging. But I'm clueless about just what to ask for when I'm talking to these folks about these things... Hell, I barely understand some of what you said in your reply... ;) (But I'd REALLY like to meet that liveaboard, TIG welder friend of yours!)

Thad, thanks for the "drift" clarification. That makes a lot more sense. The stuffing box idea sounds interesting too... Assuming I can match the size I need and the "tube" could be made to fit the space beteen the keel and deck? Who makes that sort of thing? Edison?

[ 03-18-2002, 11:24 PM: Message edited by: Art Read ]

Thad
03-19-2002, 06:41 AM
Stuffing boxes can be had at any good chandlery, Hamilton Marine for example and lots of small shops around here, marine engineering, engine, and propellor shops too. The bronze or copper/nickel tube with the plate welded to the bottom would be great and more to the design, but then you have to make the decision. The stuffing box would be above the waterline so there would be little drip ever.

Buddy Sharpton
03-19-2002, 12:35 PM
Another thought. Is the leading edge of this rudder to be nestled right up to the deadwood or skeg, or can you have a semi balanced rudder with the stock at about 40% of the chord width aft of the leading edge? That latter configuration works even better with this suggestion. Corrosion and having/ paying someone else with welding equipment and skill to make those parts are both something you can avoid by buying carbon fiber tube for the rudder stock and fiberglass glass tube;/bearings for the rudder tube. You can use your woodworking skills and epoxy to build your parts, these composite parts are out of sight, and for that same reason, easier to maintain. No underwater seepage/corrosion problems like stainless steel and foam creations on a fiberglass boat. The carbon fiber and fiberglass tubes bond really well to the wood. An idea.

Art Read
03-19-2002, 12:52 PM
Interesting thought, Buddy. I don't really want to change the design to the extant that offseting the rudder would entail, but the carbon-fiber post/fiberglass tube idea has possibilities. Especially the idea that I can "machine" it myself! It may not be "kosher" from a traditionalist point of view, but then again, neither is my ply sub-deck or the kicker on the removeable bracket I'm gonna be keeping aboard to keep SWMBO happy... I really just want a reliable solution that won't detract from the overall "look and feel" of the boat. Would materials like this be available "off-the-shelf", or would I have to have something made to order? And again, who would carry this stuff? I'm guessing the local chandlery is out? Thanks!

(Here's a view from above of the deck blocking I've put in to take the top of the tube/rudder stock. The tube will come thru the keel just forward of the floor timber at lower right. I'm thinking that bedding another block to fit on top of the keel there is a good idea too? I've seen it done both with, and without, one.)

http://www.imagestation.com/picture/sraid29/p3a60beceac6b63ceeaa1d16bc0a04043/fdf3e107.jpg

[ 03-19-2002, 01:08 PM: Message edited by: Art Read ]

Wild Wassa
03-19-2002, 01:29 PM
Art cheers, This Aussie site has things to look at including tables and product lists. No doubt your'e well underway but an interesting site.

Composite Spars and Tubes - Carbon tube for marine applications. http://www.compositespars.com/

ps, CST export tubing to the US and advertise, promt delivery worldwide by express courier.

Warren.

[ 03-19-2002, 03:31 PM: Message edited by: Wild Wassa ]

Art Read
03-19-2002, 11:15 PM
Thanks for the link, Warren... Looks interesting. Now all I gotta do is figure out the conversion from those pesky metric measurements to our "antiquidated" fractional inches...

It looks like their carbon fiber is only available in "tube" form? No such "beasty" in a solid rod? Just thinking about about how I'd seal the ends after shaping it to fit. Obviously, weight isn't a "huge" priority for this application, but this stuff is completely alien to me...