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Old 09-05-2009, 00:46   #31
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I would suggest that you trot off to HomeDepot and pick up some nice clear Cedar 2x6s. This will give you an nominal thickness of 1 5/8 inches, and epoxy them together with a truck load of pipe clamps. You could thru bolt but it might not be needed as cedar works well with epoxy, unlike Oak which really doesn't bond that well. If you are going to thru bolt, use some stainless rod and have the ends threaded.

Let it sit for 24 hrs, and then lay your old rudder over top, trace it out and get out the sawzall and cut out the blank. For shaping, a plane or if you are crazy like I am, a mini grinder with some 24 grit discs. Have at it til she looks like a rudder, and then sand with 60 grit, then 120. Apply a coat of epoxy and cloth. Add cheek pieces if you want some more beef at the top end. In this case I think marine ply would work fine. White oak is hella expensive.

I had a 30 foot cedar planked sloop with an oak rudder that had dried out soo bad the cracks between planks were getting upwards of 1/2 and inch. We couldnt fix it as it had also warped and twisted, so this is how we built the new one.

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Old 09-05-2009, 03:07   #32
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Western Red Cedar...

From memory Western red Cedar is a light, strong, soft, water resistant wood that works and glues easily. I would not recommend a rudder made from it for other than sailing in sheltered waters without approval from a competent designer.

1. Would a laminated rudder of Red Cedar work for the summer in saltwater, without glassing and epoxy?
I would not do this if it means not protecting the wood.

2. Should I dowl or through-bolt to give extra strength?
Dowls and bolts may weaken the rudder. I would not recommend through bolting to increase strength, particularly using western red cedar.

3. Do I need to use Resorcinol glue? Any tips on gluing?
From memory resourcinol glue does not fill gaps, so your woodwork would need to be absolutely top notch.

It is hard to make suggestions without more information. Can you post some photos?
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Old 09-05-2009, 08:19   #33
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Hi Mike,good to see progress.To answer you questions,
1/ is it ok to not glass it for the summer
NO, the photo of the blue Contessa shows a weak rudder design due to the prop appature and my suggestion of WRC was for use as a core in a composite structure, dont think of it as a wood rudder. The reason for the choice of WRC rather than foam is a/ cost b/ availabiliy,(you can buy it locally without shipping costs) c/ stronger than a foam core( if it was not for the prop appature you could skip the glass and go sailing with the core) d/ familiar material for most novices to use(nice low tech material)
Now,you will also notice i recomended using structural glass,not just glass cloth again due to the weak design, think about it,the only thin connecting the top to the bottom is that sliver of material behind the appature and it is in a torque situation,its being twisted every time you turn the tiller so it needs to be strong,in fact why dont you substitute a couple of sticks of nice clear honduras mahogany for those last few laminates as it glues well and will do the job better than the WRC.
2/ Should i dowel or thru bolt
no need to but you could use dowels or biscuits for easy alignment of the laminates,eliminates slipping and sliding during glueup.
3/ Do i need to use resorcinal.
no,epoxy will do fine,just dont go squeezing it all out,this is however an application where resorcinal is superior.
Now, one more thing about glueing up the blank,ideally you would stress relieve it by ripping your 2x4s into 2 or 3 pieces and rotate every other stick end for end before glueing back together, while not absolutly necessary it makes for a more stable blank.The purchased blanks are already done this way.
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Old 09-05-2009, 08:46   #34
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I just wanted to point out that it looks like your self steering gear is of the type that uses a trim tab down the trailing edge,if this is attatched to the rudder in a number of spots down the whole depth it would allieviate the torque situation so it will be easier on the rudder than steering with the tiller.
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Old 11-05-2009, 22:06   #35
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Laminated and curing

OK... thanks....

I decided to go without releasing the boards. They were all pretty darn good looking boards, clear, no knots and pretty straight. I did check the end grain and alternate and was careful to check grain against board curvature.

As I didn't have a perfectly flat surface on which to work I had to wing it a bit. I managed a relatively uniform surface, although I imagine I am going to pay the price when I get the belt sander out.

I have decided to go with the full glass job as I really want a strong rudder after all this. This job (laminating) has gotten me over my fear of sticky stuff that cures too fast. (I hate deadlines) .

Fortunately, the cost of having the boat on the hard and my desire to go sailing are pushing me through this job, and the bonus is, I am learning new skills that I am sure will be of great use to me in my sailing career.

So, thanks again!
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Old 11-05-2009, 23:28   #36
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Power planer...

I'd suggest doing the rough work with a power planer.They're pretty cheap these days. Finish up with the belt sander.

Don't forget to wear breathing protection. I believe western red cedar dust to be toxic.

I'd also suggest being careful with the fibreglass/epoxy work (that's what you're using, right?). Most of the strain is carried in the outermost layer. The wood is only there to keep the layers of fibreglass apart.
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Old 12-05-2009, 00:04   #37
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Hello OffSeason, I am just reading your thread now. Too bad, because I have a workshop in Surrey, B.C., I'm not using right now. I'm working in Kelowna. If I had seen your thread earlier I would have suggested you bring that blade into me. I have a whole freeze full of prepreg glass and carbon fibre. I also have a walk-in oven ideal for curing.

By the way, if you hear of a Contessa 32 locally pls let me know.
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Old 13-05-2009, 17:39   #38
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Hi Guys!

I have hauled her out and removed the rudder, and have brought it home. Pretty waterlogged I think! Anyway, I have 12' x 1' 11" (23") of laminated Western Red Cedar and the rudder is 9' 9" x 1' 6" x 1.5" at it's extremes.

So it looks like I am ready to go ahead and cut it out of the blank. Any ideas as to how I should position it over the laminations for best strength?

I suspect that the rudder broke because the tiller was tied off while under-way and the servo rudder on the self steering gear was in control. I can imagine the kind of turning force that little wind-vane rudder can exert.

I am kind of glad that I am replacing the rudder. Even if it isn't a pro job, Better the devil you know as they say, and I will know more about what that little servo rudder can do!

Thanks for any comments. It was a pure joy just motoring from the slip to the haul-out... I can't wait to get her out under sail!

All the best,

Mike
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Old 14-05-2009, 07:24   #39
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Think Drift Pins

Mike--

Based upon the photograph that shows the old rudder aligned with the grain direction of your laminated timbers, once the new rudder is installed, as it is turned in the water flow you will be applying bending moments across the width of the blade. The resulting torsional shear along the length of the rudder will apply a splitting load to both the longitudinal grain of the timber and your laminated joints.

To avoid the potential problems the foregoing may cause vis-ŕ-vis splitting the rudder from end-to-end, I suggest that once you have cut the shape of the rudder out of the laminate, that you set the new rudder on edge and drill 3/16" diameter holes transversely through the center of the laminate (across the grain) from what will be the leading edge so that you can install countersunk "drift pins" at roughly 12" in centers--located of course so that they won't interfere with the positioning of the pintles. (Ideally, the pins should not be perpendicular to the grain but angled to align with the water-line of the yacht when the rudder is mounted.) For the drift pins you can use 1/4" diameter bronze threaded rod as “lag bolts” counter sunk on the leading edge and ending only far enough inboard of the trailing edge to allow you to fair the trailing edge without exposing the pin. Fill the counter sink holes with teak plugs saturated with the same epoxy used to laminate the timber. By tightening up the drift pins, you'll preload the wood and relieve the splitting action of the torsional shear, minimizing the potential for problems in the future.

FWIW...
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Old 14-05-2009, 08:48   #40
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Looks like you are right on track to me. I don't think you need the drift pins if you use a sufficient amount of glass. IMHO you are building a glass rudder with a cedar core. I don't have the knowledge to recommend a layup but use roving not chopped mat and Epoxy. If you have never used epoxy get the free book from West Systems as it has a lot of information. Wear good protection.
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Old 14-05-2009, 12:50   #41
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Why not router out a couple of slots, or saw and chisel, 1/8 depth and use some stainless bar stock to reinforce the whole thing? Through bolted in place of course.
Does anyone know the construction of the original Contessa 26 rudders?
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Old 15-05-2009, 15:38   #42
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Hi guys,

I am now sculpting the rudder. Any tips on fairing the trailing edge of the Western Red Cedar core? The leading edge is pretty basic looking comparing to the old rudder, rounded corners and almost the same thickness as the 2x4s, but the trailing edge is entering an area where I am not exactly in my element.... detail work! Are there any tried and true boat building techniques that I might use to get as fair a trailing edge as possible?

Mike
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Old 15-05-2009, 15:53   #43
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If you accurately marked each side of the trailing edge along the length of the board before you started carving, you should be able to work to those lines and come out pretty good. If you didnt mark it and your parallel sides are gone, It's going to be tough to know if you are getting it done without a built-in twist. The other option is if you had a big vise you could support it in the vise with trailing edge up and the remaider resting on a table. If you have a "good eye" you then could work each side of the rudder eyeballing the trailing edge as you work.
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Old 15-05-2009, 16:53   #44
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Make up a template so you have the curve of an upper edge of an airplane wing and apply it to both sides of the trailing edge of your rudder as you sand.
I would not use roving on the rudder, just mat and cloth in two layers each with cloth being your last layer. mat, cloth, mat, cloth. 10oz cloth will bend around the leading edge but not very well around the trailing edge.
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Old 15-05-2009, 17:32   #45
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Wunibald Kamm and rudder design...

I would suspect that the trailing edge of your rudder may not have to be too sharp.

The Kamm tail came in for some discussion some years ago and it is possible that a sharp trailing edge is not necessary.

From a structural point of view a sharp edge is undesirable.

Others here may have a better idea of what can be done in fibreglass.
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