Commanderpete,
Here is a rudder design that might give you that winning edge..
Commanderpete,
Here is a rudder design that might give you that winning edge..
That would just be WRONG.
Proceed with construction (but paint 'em black).
Commanderpete,
Of course I was just joking, that would be HIGHLY unethical!
But hypothetically speaking you would of course want the 20hp submersible electicric motors with hidden batteries in the keel?
Commanderpete,
Here's another subtle mod that could be done for a little extra speed
Last edited by Tim61N; 03-02-2005 at 05:14 PM.
I think that the rudder mounted motors probably would not be large enough to provide the thrust needed to dominate the SF Bay Fleet, as Bill clearly intends to do. Therefore, I propose this:
You'll note that it uses the engine from the Virgin Atlantic Global Flyer. I figure that that will be up for sale on eBay in another few days, and would be more economical to purchase than a new powerplant.
It may do better mounted on the centerline for cruising. This configuration is obviously intended to round marks to port only.
Kurt - Ariel #422 Katie Marie
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sailFar.net
Small boats, long distances...
Waterski rudder
Here are some pics of my new rudder coming together. All the bronze parts were made from siicon bronze, rods were threaded directly into the shaft. I will use my leftover 3/8 rod for rivets for shoe and strap similar to original design. Rudder shape is close to original with a little more area down low like a constellation.
New rudder looks great Tim. Did you glue the pieces together? We are building a new rudder to match the original on Cup O Tea (Commander 290). There is no evidence of glue between the mahogany pieces on my original. Ebb has suggested somewhere that resorcinal glue is the way to go and I have it on backorder from Jamestown. My carpenter pal is tired of waiting for the backorder and wants to use a System 3 product (TAG?) But - the more I think about it - I remember someone here saying that the 1/16 spaces between the pieces in their rudder filled in when the wood swelled after being in the water. If the wood is bolted and screwed to the tiller shaft and has drift pins through it, and the pieces are glued together with 7000 lb psi glue - where is the give going to happen when the wood swells?
A friend who restores classic wooden Chris Crafts says they use 5200 exclusively between the boards. Stays flexible and gives a more natural ride. Does anyone think it makes sense to use the equivalent of 1/16 or 1/32 of 5200 between the slats to allow for swelling? And will 5200 hold up over time?
If "nothing" lasted 40 years . . .
Years ago I filled the gaps on my old replacement rudder. Might have used 5200, can't remember for sure.
I think it was a bad idea, the wood just swelled and made a larger gap.
I'd leave it open. Maybe a 3/16 gap with 3 boards. Possibly a larger gap with 2 big boards.
There might even be a chart somewhere that calculates how much wood swells
Nice work there Tim. How did you machine the ends of the rudder shaft?
Last edited by commanderpete; 05-20-2005 at 08:37 AM.
That right. The traditional rudder need not be improved on in terms of method. Wouldn't you think the planks were just bedded in the old way of marrying metal and wood? If the boat is going to spend time out of the water regularly that's the way I'ld do it because you can maintain it.
If a blade put together with rubber dries out it may pull apart in a way that won't be easy to clean up. May wish you had put it together with a bedding compound you could just reef out and fill in again.
Polysulfide likes being underwater and is a longer lasting material than 5200. 5200 is so tenacious an adhesive that when a rudder dries out it is possible that the planks could crack or pull slivers of wood away at the seams. Polysulfide I believe is not as hard when cured and would be more likely to move with wood shrinkage.
So I agree with the method that leaves a seam for swelling. Seams payed with old fashioned bedding compound in a newly made plank rudder. When the boat is pulled next season for bottom paint, the squeeze out from the seams can be scraped off smooth, the rudder painted, and put back in. If the boat lives in the water, it'll remain tight.
This way you won't have to guess perfect how much to leave for the wood to swell. Fill it and scrape off the excess later. Mike may have something to say about priming the mating surfaces (the edges) with something. I might stabilize them with thinned epoxy
I guess the real problem is how to resist cinching up the long bolts too tight. One way to help keep the seams filled might be to plane the edges slightly concave. Tend to keep whatever you decide on in there. And thinned epoxy IMCO would be a great primer for the whole rudder. Befor assembly slather it on every piece all over and soak the holes.
Last edited by ebb; 05-20-2005 at 11:22 AM.
There was a real big gap once I cleaned it up and dug out the sealant.
Couldn't tighten it. Ended up cutting the drift pins and pounding them out
Project continues...next year....maybe
Yes, I did glue the two pieces of my rudder together using system 3 epoxy. This was probably not necessary from a structural aspect, but I thought it would distribute any loads on the end of the rudder a little better. I will not use any glue on the bronze through bolts, so the wood should be free to expand outward. The expansion will not likely be significant since mahogany is so dense, so it will just tighten down on the nuts. I will will just tighten the nuts to snug to allow room for expansion. I think I will use some 5200 to seal the rudder shaft in its joint with the rudder. I am still contemplating glassing the whole works, not really concerned about keeping water out so much as getting a bit stiffer and a nicer trailing edge.
The holes in the shaft were bored and threaded with a vertical mill. The hardest part was keeping them all exactly in line all along the shaft as the mill table only had about 20" of travel and the holes are spread about 36" apart. We bottom tapped the holes about 5/8" into the shaft, and I think this will make a much stronger unit than the original. The straight shaft should distribute the stress all along the length instead of at the weakest point where the topmost bolt comes through. Looking at my old shaft its easy to see why it broke. There was very little stucture after the through hole and huge countersink. I also saw alot of evidence of leaching of the rudder shaft at that point where the through bolt was totally intact. This confirms my suspicion that the shaft was probably naval (brass) and the through bolts were likely sil bronze. So my rudder has all sil bronze, most of it all from the same source (the nuts on my through bolts were made with leftover pieces of the ruddershaft), so hopefully I will eliminate most of the galvanic issues.
Tim, Nice. Like the way you matched the grain. I think it was Theis who put a rudder together similarly. I worried about the rudder trying to relieve swelling stress by cupping - he said it didn't happen. Maybe the shape of a traditional rudder has something to do with that.
Congrats on getting the long holes drilled square! Hard, very hard. And end tapping the rods into the shaft is by far the very best method, elegant! That rudder looks great!
Thanks for the feedback and photos gents. We've been wondering about two pieces pieces in favor of the original three and it looks like we're in good company. I'm wondering if the three pieces had some distribution or flex function.
My carpenter pal likes to make things TIGHT so it will be a bit of a challenge to get him to just "tighten to snug". I notice on Tim and Pete's rudders that y'all have skipped the stainless peened straps on the outside. The original positioning is so weird (out of flow) but the original sure held together for a few years.
Scott
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