Winter Rudder Project

[tmw]

Okay, my plans are set, and I purchased materials.  The admiral will be out-of-town for a week, so I can hopefully get some work done.  I'm planning to leverage some wood pieces sanded to shape for my rudder upgrade.  Here's the simple plan:
Step 1:  Buy wood parts.
Step 2:  Glue them onto existing rudder.
Step 3:  Sand the wood down to shape.
Step 4:  Finish the wood for durability.

My materials are two 1x12 wood boards (22" long) to attach to each side of the metal plate, and a 2x2 wood board, also 22" long, to create the front blunt edge, both select pine, and marine epoxy for glue.  Still have to figure out the finishing, maybe cover with fiberglass.

The cross-section of the rudder will approximate the foil shape, but how should the bottom be?  Should it just end flatly?  If the rudder is like a wing, many airplane wings have little winglets.  I am curious if adding a short horizontal stabilizer type winglet across the bottom of the rudder would help it be more efficient?  It could also help keep the rudder in the down position too, maybe.

I'll post some pictures as the work begins.

[Duckie]

If you are using the stock rudder as the template for your foil, why not let the aluminum plate act as the leading edge and sculpt the wood just up to that?  The quarter inch plate will not break or deform if it hits something, so the wood should not be impacted at all.  I may do the same thing with my old rudder someday.  I have a manufactured foil on my 16 now, so the original is just sitting.  You may also want to through bolt the wood in a couple places just in case the glue lets go.  You can set the head and nut into the wood and epoxy over them.  If you do it this way I would recommend that you glass the whole thing and finish it bright.  I don't recommend this out of aesthetic sensibility, rather to make it so that if the wood starts to rot under the glass you will be able to spot it before it gets too bad.   If you add a 2X2 to the front of your foil you will change the lead of your leading edge which might affect the way your boat handles.  That may not be a bad thing.  I have read that doing this can help with weather helm.  I guess you would have to try it out and change the shape if it doesn't feel right.

This should be a fun little project.  Sculpting wood is one of my favorite parts of boat building.

Al

[Salty19]

If you are using the stock rudder as the template for your foil, why not let the aluminum plate act as the leading edge and sculpt the wood just up to that? .....   If you add a 2X2 to the front of your foil you will change the lead of your leading edge which might affect the way your boat handles.  That may not be a bad thing.  I have read that doing this can help with weather helm. 
Al

Extending the leading edge forward about 1 1/2" is actually one of the two main critical design improvements in this modification. The second is the foil shape.  The IDA/ruddercraft design, which has quite a bit of R&D put into it, moves the forward so that the leading edge is actually somewhat under the boat, as opposed to behind it.

You WANT the leading edge to move forward. This is what improves the weather helm.  Not doing so will lead to a lot of trouble for much less than benefit than one would expect.   Without a doubt, put that leading edge on there. 

I would not use pine here though.  Use 1088 marine plywood or solid hardwood with anti-rot qualities.  A 4'x8' 4mm sheet will cost you about $35 and should be enough to do the entire rudder with some to spare. It's lightweight, easy to laminate/sand, resists warping in temp changes, and should last a long time provided it's sealed well.   Sheath the wood in a layer or even two of 6oz fiberglass once shaped, then fill in the glass weave with more epoxy until smooth.  I would add a little thickener to the second coat..not a lot, just a little, then let cure, sand and apply a third smoothing coat.  Sand, prime, then paint.  You'll need the thickener for the lamination process anyway.

You could also extend the rudder downward a few inches to offer more surface area to bite the water. 

The devil is in the details when it comes to DIY rudders; there is a lot of info on this site to design it correctly if you search for it.

Nothing wrong with using foam too.  If I were to build one, I would probably lay foam over the metal blade behind the leading edge, then cover the foam in thin marine ply. You want about 1 1/2" of chord so calculate the thickness of foam and/or wood you need considering the thickness of the rudder.  Remember the fiberglass layer is going to add about 1/8" overall (1/16" on each side), so your raw materials should be about 1/1/4" thick at the chord before 'glassing.

It's going to want to float anyway, so might as well make it as light as possible and plan on a downhaul line, or one of the neat Com-pac rudder handles that are equipped on newer boats.

Just my opinion as a long time reader of this site.

[Bob23]

tmw:
 I did the exact project you are describing when I rebuilt my flat blade rudder into a wood foiled blade. It really transformed the feel of the boat. I have photos I can send you but the process is described in my thread "The Continuing Adventures of Koinonia"....somewhere....I'll try to find them. Meanwhile, see if this makes any sense:
http://s617.photobucket.com/user/Bob23_photo/library/Koinonia%20rudder%20project
  Some of the photos may not be pertinent to your project but some will be. I'd be happy to discuss this with you on the phone, just message me your number.
Have fun!

Bob23

[tmw]

Okay, so I began the process of glueing the wood into place, currently held by clamps.  I'm thinking to keep the wood strong, using a copper naphthenate treatment after sanding to shape.  If things go to crap, I'll have to order and IDA rudder as a replacement.

Thanks for all your comments.

[tmw]

Tonight was glue for the leading edge piece of wood.  Let's try some pictures.

Here was last night, putting the side parts on, and you can see the boards don't cover the entire existing metal rudder, but that's okay because at the trailing edge they would be sanded down to match the metal thickness anyway:


Here is tonight, attaching the front leading edge.  It's not quite as wide as the boards with the metal plate in between, but should make a smooth surface once they are fully sanded to shape:


Happily, while purchasing more glue (using marine epoxy, because it says "Marine", wait, would anyone here be offended at jarhead jokes?  I don't want to get banned already) at the Home Depot, I found the supply of fiberglass and resin, so I purchased that tonight, along with the coarse belts for shaping the rudder (hopefully tomorrow); and the copper stuff should arrive tomorrow also.  My goal is to be nearly done before the admiral returns Friday, and kicks me out of the house.


These images aren't photobucket, but rather the image url from the google photos, and it works for me so I'm hopeful they show up for others.  If the images don't show for you, let me know.  Last night photobucket was giving me fits trying to upload pictures, kept getting 98% complete and quitting on me, so I'm optimistic this method might work.

Tim

[Bob23]

I see them. I found a pic of the latest incantation of my rudder with hold down bracket. Notice it tilts quite far forward.
Bob23

[Decatur]

I'm following this with great interest!...Why Pine wood?   Pine is a soft wood, but easy to work with.   Why not a hard wood like white oak?  I bet you could get 20 years service out of oak?   Good job and great pictures!   Tim
What type of glue?   White Elmers wood glue?

[tmw]

Bob, is the rudder supposed to sit that far forward?  Also, how did you finish the top and bottom parts?  I keep thinking that a small horizontal fin (like a wing keel) across the bottom could be fun, but also scared about that option.  Anyone have guidance on the benefits of wing keels, and how that can apply to a rudder?

My reason for selecting pine was that I could readily find the size and shape needed from my local home depot, and it was pretty inexpensive.  It's also easy to work with, and hopefully sinks better than foam.  Foam would be much less expensive (have a bunch sitting around), but could lead to a floating rudder.  Light and big enough, and it could help provide buoyancy to the boat

The other reason I think pine is acceptable is that I plan to seal it. The copper naphthenate solution arrived this morning, and then encapsulate the whole think in fiberglass (hopefully helps with the softness too, maybe).

The glue I used was Loctite Marine epoxy.  I don't think Elmers wood make a good connection with the metal plate, although it could make removal pretty simple.

The sad thing is I didn't get the sail the boat before the cold weather set in, so I really don't know how much of a difference this will make, so I guess that means anything can be a success.

[Bob23]

TM:
   Mine does because I trimmed some off the top of the blade to allow it to tilt like that. The stock blade does not.
   A few notes on your project: Although you have not sailed your boat without it, the improvement will be obvious to anyone who has sailed a 16 with a stock blade. It will float! No doubt. If it's pine of foam, it will float. You will need a downhaul or better still, the Compac hold down bracket. I devised a rope downhaul and it worked ok but didn't hold the blade plumb. The bracket will. If the blade is allowed to float back even just a little, the weather helm will increase resulting in less fun and less speed.
Mine is foam around hardwood frames with 1/8" okueme plywood and fiberglass over all. The top and bottom are white oak which was from rift grain white oak flooring.
   I'd advise you to forget about the wing on the rudder. The keel and rudder, while working together really perform different functions. Your foiled blade without the wing will perform just fine.
Bob23

[tmw]

I wanted to be lazy and watch a movie, but took the time to work on the rudder while the admiral was away.  My grandfather, who loved woodworking, said he often went to the basement to make sawdust.  My wife constrains me to the shed, but my grandfather would have been pleased with the amount of sawdust created tonight.  I was power-sanding for over an hour.  I thought the 36 grit sandpaper on the belt sander might be too coarse, but no longer think that is possible with the amount of material removed.  I thought that pine being a "soft" wood would come apart easily--that wasn't true.  I can't imagine how hard it would be with a real hard wood.  It was a dusty night.

I drew some lines where it should be sanded, front center and about 4.5" back on each side, as reference points, and then tried to guestimate as best as I could.  I'm sure it's not a perfect airfoil, but looked close enough for me.

Here's a picture of the post-sanding rudder:


After sanding was completed, I treated the wood with the copper naphthenate.  I'd never used it before.  The interesting thing was hearing the wood crackle as it was soaking in.  I'm hopeful the wood remains attached.

One nice thing was the rudder has a hole for easily hanging for the treatment:


Next will be covering with fiberglass, unless I end up with a wing.  My thinking is the wing could serve a downhaul function, and still keep contemplating the idea.  Per wikipedia, the wing is helpful when side-force is required, but provides extra drag when running.  I'm guessing the rudder spends more time doing the equivalent of running than reaching, and I should listen to Bob, but I want to keep noodling about it.

Tim

[Bob23]

  Many people have made the mistake of listening to me: You may not want to join that group!  It's looking good! I really can't comment on the wing except to say maybe reserve it for your next project. Too many changes and you won't be able to tell which change is and isn't working. I can't wait to see the finished project: And just in time for Christmas- a nice gift for your boat.
Bob23
 

[tmw]

Are you sure this is the same "I DEMAND TOTAL ALLEGIANCE!!!!!" Bob23 going to the Chesapeake Bay Mid-Winter Gathering?

I've been trying to read to understand the design implications from this:
http://www.sponbergyachtdesign.com/keel%20and%20rudder%20design.pdf

Thus far, I've come up with my 13% foil thickness as percentage of chord and 33% maximum thickness location are good choices as long as the foil remains clean and smooth (e.g. break out the wax polish, no bottom paint). 

There's something about elliptical rudders generating the least vortex drag, which clearly isn't going to happen.  Hmm, still thinking about it....

[Decatur]

Wow...It sure looks nice.   What an interesting green color....Fiberglass?  I'd love to see the leading edge of rudder.  Great Job!  How much time/labor do you have in the project?  I might get motivated and make my own too!  Tim

[tmw]

The green is the copper treatment which hopefully makes the pine wood last.  It should be covered up by the time it's finished.  The boards were pre-cut to 22" length at home depot, and setting up and glueing in place was really only like 30 minutes.  The hardest part by far thus far was the sanding down to shape, which took a good 90 minutes.  I prepped the fiberglass, but opted to take a night off tonight.  I'm guessing maybe 5 sessions of 30 minutes each (side one, front edge, side two, front edge again, bottom and top?) and then however long sanding a smooth finish will take.

Ask me next week if it really did finish as planned.  I probably should have started the fiberglass tonight, while I'm still allowed to work indoors.