Building a new rudder

[NevilleCat]

Don't know if you have seen Yosh from Sailing Nanji rebuilding his one after they went up on the reef... seems pretty simple...

https://www.youtube.com/watch?v=n1D63gfgW_I

https://www.youtube.com/watch?v=7L8p1ZOLwDs

[guyrj33]

I can see how red cedar will make a good core material for your new rudder.
I'd like to suggest using vacuum bag technique to drive epoxy into each individual board before final assembly if at all possible. Then after the filler boards are bolted up use the vacuum bag to again encapsulate the structure with epoxy. Finally use vacuum to attach robust layers of composite over the wood core.

[LeighWebber]

Originally Posted by Nicholson58

Wood filler - ugh!

I rebuilt our monster rudder. It was SS skeleton with foam and fiberglass, all turned to mush

I would never permanently immerse anything in water that I didn’t want saturated eventually. The first law of fluids is water leaks.

I used exclusively all materials from Fiberglass , Epoxy , Composites, Carbon Fiber - U.S. Composites, Inc.

Use 635 THIN epoxy for all layup. I built and shaped the core of 635 THIN and 3M micro balloons. 3 total gallons resin and two 4 gallon balloons Fillers

Use five gallon buckets and a drywall mixer with a heavy duty 1/2” drill. GO SLOW!

Kick time in a cool basement is hours and the cure speed lets you pour five inch thick sections. 3 days before it’s hard enough to sand.

This core is 100% waterproof forever.

After shaping, I had it vacuum bagged with carbon fiber.

See my photos
https://www.cruisersforum.com/galler...d=49581&page=3

I guess I wouldn't call it "wood filler". The rudder is made of wood, not filled with it. With appropriate paint and antifouling, there's no reason it wouldn't last as long as a wooden hull -- many decades. I'm reluctant to put fg cloth or any other kind of layer over the wood, because that would indeed create a potential delamination where water could get inside. But a solid piece of wood, suitably painted, doesn't present this risk. My rudder isn't one solid piece of wood: it's laminated using resourcinol glue, which is more waterproof than epoxy. There is very little chance that those laminations will come loose.

The possible problem areas in my case are the holes where the rods penetrate the wood. If water gets up inside those holes, it could sit there and possibly cause rot. That's why I plan to use 5200 to seal the rudder leading edge / steel post contact surface, and to fill the gap around each rod with penetrating epoxy. But perhaps it would be better to use 5200 to fill those gaps as I add each lamination layer. The 5200 should be flexible enough to accommodate the expansion/contraction differential between the rods and the wood. That's my theory, of course.

The rudder you built looks awesome! It's about the same size as mine, as far as I can tell from the pictures. The only problem area I see is the very top and bottom where the rudder meets the post. The skin wraps around the post, and the seal between the post and the epoxy will eventually fail. Water will then work its way down between the post and the skin, with crevice corrosion a possibility. OTOH, an annual inspection would reveal this, and you could repair it quickly. Besides, it would take an awful lot of crevice corrosion to weaken that SS post!

[Searles]

Cedar is fine for the core ,cedar and epoxy will make a fine light strong rudders,,avoid weight to make the steering light ,and shape to make it responsive. Good luck .⛵️👍

[Jim Cate]

I'm reluctant to put fg cloth or any other kind of layer over the wood, because that would indeed create a potential delamination where water could get inside.

Considering that my entire hull is Western Red Cedar/epoxy/glass composite, I surely hope that your worries there are unwarranted!!

Seriously, our rudder is built from timber (Silver Ash) in much the same manner that you describe, and is covered with glass/epoxy, and now at age 30 years and >100 K miles logged, still intact.

I dunno if shipworm is an issue where you sail, but if present, I reckon a bigger risk (from local failure of antifouling) than from possible rot.

And BTW, you should consider use of 2205 duplex stainless for the shaft. Much stronger than 300 series and much more resistant to crevice corrosion... and not much dearer.

Jim

[NevilleCat]

[QUOTE=LeighWebber;3249384]I'm reluctant to put fg cloth or any other kind of layer over the wood, because that would indeed create a potential delamination where water could get inside. But a solid piece of wood, suitably painted, doesn't present this risk. My rudder isn't one solid piece of wood: it's laminated using resourcinol glue, which is more waterproof than epoxy. There is very little chance that those laminations will come loose.

Given that Epoxy glassing a wood core is probably the gold standard for one-off boatbuilding I'm surprised you are concerned about this.
In any event if you built it as you are suggesting I don't see why you wouldn't glass it as well.
Surely the chance of a small leakage at the post is better than having the whole thing constantly immersed anyhow?

[mitiempo]

Originally Posted by LeighWebber

With appropriate paint and antifouling, there's no reason it wouldn't last as long as a wooden hull -- many decades. I'm reluctant to put fg cloth or any other kind of layer over the wood, because that would indeed create a potential delamination where water could get inside. But a solid piece of wood, suitably painted, doesn't present this risk. My rudder isn't one solid piece of wood: it's laminated using resourcinol glue, which is more waterproof than epoxy. There is very little chance that those laminations will come loose.

There is absolutely no reason that an outer layer of fiberglass cloth and epoxy would ever delaminate. It will also provide good protection from abrasion.

As you are doing its life will not be long.

[thruska]

I will simply add that 5200(the devils glue) is not necessarily the savior to water intrusion,
IMHO.
Good luck with your rudder. It looks as though you have researched all aspects.
I used thinned epoxy to seal up the holes I drilled in my Columbia28 ‘s rudder.
It had minor delaminations. I followed with regular mixed epoxy poured into all holes. And again after first application seeped in. Then glassed the rudder shell surface after a rough coarse sanding for good adherence . Then sanded again for bottom paint.
No longer had any water weeping from rudder after haul outs. No 5200...

[LouK]

Although I cannot speak from experience, as an architect who has build boats, I would suggest there are probably better choices for woods than cedar. Although cedar has good moisture resistance, unless it was laid up in narrow strip fashions & laminated perpendicularly to the direction of force, it won’t be very strong. Cedar is relatively soft & your rudder is trying to act something like a beam. Like your keel, it acts very much like a fulcrum and the bending stress & lateral loads are likely fairly substantial.

Unless you can find ‘select structural grade’, No. 1 & 2 grades have moderate strength and No. 3 is down right wimpy. To provide something more of a point of reference not a recommendation, cedar has about 30-50% of an equivalent section of yellow pine.

Cedar, while very light it does needs to be braced frequently as in wood strip boats. Better choices of wood would include mahogany, teak, white oak.

[DeValency]

Unclear to me how you get the final hydrodynamic shape. If the skin is made of at least 5mm thick fiberglass laminated throughout, the internal wood parts will not effect the overall strength, but mainly provide a backing to the fb skin. The internal structure sounds great with the size and number of rods planned.

[Elie]

Since you are going for a new rudder, have you ever considered the idea of a metal one?. I have done that more than 12 years ago when my rudder vas failing due to water ingress trough the cracked fiber glass attachment on the stainless steel rudder shaft. it was made of stainless steel(316L grade!), of too heavy gauge(a mistake) but it is a almost perfect solution when compared with the old original model. The shape was modernised with a good NACA profile, and it can be used as a reserve of fuel since it is equiped with all the fittings for filling it. I shall say that I never needed to use this option. It was heavyly coated with interprotect and I never had any issue with it. By the way mild steel instead of Stainless steel is in my opinion a cheaper and very good option and much easier to bend and shape!.

[ilCigno]

Rudder calculations spreadsheet is now online, see https://www.cruisersforum.com/forums...cf-241065.html

[LeighWebber]

Such helpful replies to this thread -- thank you to all. I have been persuaded to wrap the rudder in a couple of layers of fg. So my assembly/build sequence will be:

1. Use 5200 to seal the inner cedar lamination to the post. Make sure the 5200 fills the gap between the rods and their corresponding holes. Clamp securely and leave for a day or two.

2. Glue up the remaining laminations a few at a time, using Resourcinol glue and lots of clamps (I have dozens).

3. Using cardboard templates of the foil shape, use an electric plane, then belt sander, then orbital sander to shape and fair the cedar body. The smoother I get it, the less work later.

4. Wrap the body and the post with a couple of layers of biaxial cloth and epoxy.

5. When cured, apply a layer of fairing epoxy, and sand it smooth.

6. Apply a couple of barrier coats, then anti-fouling. I welcome product suggestions for the barrier coats and anti-fouling. This is a fresh-water boat, btw (Lake Superior).

[Bill O]

Leigh,
A little late to the party, but this is how we made our new rudder core out of Coosa so it will not absorb any water.

Would suggest using the router to do the initial cuts then, sand down to the "contour lines" for each routed step. This should give you a more uniform shape.

Will need to look at Timo's files (ilCigno) on his DIY rudder calculations. Not sure they are totally applicable to a skeg held rudder as in our case, but interesting none the less. Before you start your project, you should look at his calculations to see if you could design a better rudder.

[abarclay]

Originally Posted by LeighWebber

Such helpful replies to this thread -- thank you to all. I have been persuaded to wrap the rudder in a couple of layers of fg. So my assembly/build sequence will be:

1. Use 5200 to seal the inner cedar lamination to the post. Make sure the 5200 fills the gap between the rods and their corresponding holes. Clamp securely and leave for a day or two.

2. Glue up the remaining laminations a few at a time, using Resourcinol glue and lots of clamps (I have dozens).

3. Using cardboard templates of the foil shape, use an electric plane, then belt sander, then orbital sander to shape and fair the cedar body. The smoother I get it, the less work later.

4. Wrap the body and the post with a couple of layers of biaxial cloth and epoxy.

5. When cured, apply a layer of fairing epoxy, and sand it smooth.

6. Apply a couple of barrier coats, then anti-fouling. I welcome product suggestions for the barrier coats and anti-fouling. This is a fresh-water boat, btw (Lake Superior).

I would strongly encourage you to use epoxy for everything - skip the 5200, skip the resorcinol. Much easier to work with and shape, proper gap filling, no compatibility issues with your skin laminations... the list goes on. Fill any gaps around the rods with thickened epoxy while you glue up the laminations and you'll have no worries about anything moving.

100% go for the fiberglass skin. That gives you a nice, modern, epoxy composite rudder that should last another 40+ years. Without it, you have a weird semi-traditional wooden rudder construction with some laminated parts and I think you'll be very disappointed with the longevity.

A final tip: I would add a 1/2" ring of G-Flex epoxy around the shaft (set into the rudder), where it enters the blade (and at the bottom of the skeg if the shaft exits there). G-Flex will adhere very well to the shaft, and has enough flexibility to take up the differential expansion/contraction between the different materials to prevent the most common leak point (as you found with your old rudder).