Rudder Strapping

[Idon84]

My rudder is made of over 10 pieces of 2 1/2" square mahogany glued together with 3 drift bolts. Some of the planks of wood have separated from each other leaving voids in the rudder, only one has increased to about 3/16 of an inch wide (it is easily visible in the picture). Otherwise the thing seems quite strong and the bolts look to still be in good shape after about 20 years. I was able to access the drift bolts, remove the nut and inspect the threads which look to be in fine shape. The estimate to replace is in excess of $3500 for a composite/foam replacement, as is most common now.

I read several places where builders completely skip the drift bolts and just install rudder strapping to hold everything together with some glue. Straps would be 1 1/4"w X 1/8" thick, left proud, and riveted. The idea being that I don't have to replace the rudder right away and can enjoy cruising around our home waters for now until I find the time to replace the rudder myself, most probably by shaping a mahogany blank. Also by strapping I can clamp the thing back together tight and then rivet making the joints smaller.

I read places that I should use copper flat stock and rivets. The local metal shop only gets brass and assures me that brass will be fine. What is the difference? Can brass be used instead of copper? Also I can only find copper blind rivets at McMaster Carr. So it sounds like copper is the way to go...?

Thoughts? Something I'm not thinking about? I want opinions before I mail order over 15' of copper bar-stock online.

[tpl]

recommend
1. remove drift bolts & separate mahogany pieces
2. restore good parallel glue surfaces
3. add another thin piece ~1/2" to make up removal
4. glue back together with drift bolts
5. sand, shape paint to suit
pocket $3500:-)

[Rachel]

I'm curious about this, because I thought the purpose of drift bolts was to let the wood "drift," and so there wouldn't be any glue?

Or, conversely, if one were to use glue, then why drift bolts?

Maybe I'm thinking of drift pins, and that's the difference?

Rachel

[Tom Young]

I'm sure that would work but I'd be inclined to do what tpi suggested, especially if the drifts or bolts are easy to get to.

The tiller generates quite a bit of torque where it meets the rudder, especially in heavy conditions. Those bolts handle that torque keeping the tiller and rudder working as one piece without bending(much). Straps could do the same but would have to be large enough to equal the bolts strength in resisting bending.

I had to rebuild my wooden rudder last season with new bolts. After disassembling, cleaning and reassembling, the new bolts pulled it all back together as good as new.

[Idon84]

OK so I figured out that I need to be using Copper not Brass. Brass will weaken and fall apart much quicker in salt water conditions than coper so that question is answered.

As far as the deconstruction of the rudder is concerned, I did think about ripping the whole thing apart and re gluing. When I removed the nuts from the drift bolts I tried to remove the bolts to no avail. Granted I didn't spend much time working on it. Also I only see 1 bung for each bolt, meaning they are not driven completely through and then bolted on each side. So how would I remove these bolts if they have to come out the same way they went in?

Thanks as always!

[Tom Young]

The bolts may just be threaded rod Bryon and they could end short of the last piece. In that case, you may find a little dutchman sort of wood patch covering the other end. They would likely be oval shaped to leave room to turn a wrench.
Here's my rudder before reassembly. There not the same construction but the bolt or rod could be a similar set up.
The idea being you could pop off those wood covers and snug the whole thing up without even removing the rudder. Good luck!

[Quetzalsailor]

My first, and concluding, thought is to run a little flexible sealant into the gaps, paint, bed the gudgeons, rehang and go sailing.

I don't know what's to be gained by knocking it apart, gluing and reassembling 'in kind'. I certainly don't see any point in external strapping in lieu of the 'original technology' of drifts.

I think, by the way, that there are drifts and there are bolts. Drifts are pins and are driven into slightly, correctly undersized holes. I think your drift is headed by threading and a nut. I imagine that it will not be an easy thing to knock the rudder apart w/o damage to the wood. (My drifts in the coaming are not headed and the upper end is concealed under a cap.) One way to get a bolt of the right length is to start with a rod and thread the ends after wacking it to the right length. Bolts are driven into well-fitting holes.

Rachel is bang on, as usual; the wood will come and go with moisture content (though only once each way in a year). Much tougher on the wood if it has to come and go often (years or alternately sunny or wet). The drifts might allow movement reluctantly; of course, they will not re-insert themselves. The wood retained by bolts will take a couple cycles before it crushes under the washers and the joints loosen. (That's why musical instrument wind chests have springs under their screw heads. That's why the bolt heads are exposed on butcher blocks (you snug 'em up once a year). The little insert shown above in Toms pics is, by the way, how stair railings are butted and bolted.

As for buying brass, don't. Buy bronze rod, washers and nuts from McMaster-Carr or Google for other sources.

[Rachel]

I would much prefer bronze to copper or brass too, if it were me.

Alaskan Copper might be a source for bronze.

http://www.alaskancopper.com/bb_bronze.php

[georgefmys]

I'd be inclined ,if I was going to take rudder apart anyway,to glue it together with epoxy -then coat liberally until wood won't take anymore. Then smooth it ,prime and paint. Dont think it would need sheathing with glass if glue job and saturation are well done.,assuming it's a pretty small rudder, as photo seems to indicate [ Youse got a problem wit that?]

[Quetzalsailor]

Generally, I've bought into the encapsulation idea and have, over almost two decades, bought and applied a LOT of West System epoxy, especially for someone who has to draw all day. I have encapsulated a LOT of stuff: a whole Flying Dutchman sailboat, a bathroom floor; several countertops; shower door and frame components; some cabinet and framing parts in our NE 38; a teak sole in our now-sold M 27; a tiller extension and other bits.

I would not encapsulate this solid wood application because: 1, it would need to be quite dry for adhesion; 2, a simple coating would be susceptible to damage and dings - this would allow water in and lift the epoxy either by swelling the dry wood or other evil effects; 3, trapped water would tend to cause rot; 4, swelling wood would break things; 5, wrapping the part in 'glass would help to reduce the ding problem but it would still be there; 6, hard to inspect and maintain since it's in the water, and under paint.

I'm not against encapsulating a veneered structure under water because: 1, the veneers would be dry at layup; 2, the plywood, if dinged would limit the spread of damage to one flitch, since each piece would be encapsulated; 3, the assembly would be quite stable since only a few veneers could be causing/suffering a problem.

[georgefmys]

All good points ,Quetzal...but that mahogany will dry in plenty of time before spring,and holds epoxy very well. Why would this rudder be more fragile than any one of millions sheathed in gelcoat? Either way,if you ding it, or shear it off on a rock ,it's still gonna need re-fixing.....[I got to think you'd have a tougher time breaking it if it's been glued into a one-piece structure.] To inspect,think standard visual inspection should do it..any problems would start from breach to epoxy skin and ,at least at first, be local and slow to spread.
For what it's worth, when coating stuff that is going underwater for any length of time-I tend to overdo the thickness of the moisture barrier, usually using industrial 2-part epoxy over a clear epoxy like West System, The ind. stuff is used for ship bottoms and even interiors of chemical and fuel tanks. One thing I have noticed on older wood rudders is when dried out, the wood can be much softer and more porous than new wood-sometimes a little leverage in a crack or seam can bust them pretty easily-does that mean resins are leached from fibers?

[Rachel]

Why would this rudder be more fragile than any one of millions sheathed in gelcoat?

But...... millions of solid* wood rudders "sheathed" in gelcoat? I wouldn't think that would hold up between the wood moving and the gelcoat not liking to move.

My ex-Alberg 30 rudder was 99% fiberglass, but there were two wooden strips inset into it to fill a couple of molded in channels. There was gelcoat over the whole thing. The only place it had cracked was over the wooden strips where they had expanded/moved and the gelcoat hadn't.

Rachel

*i.e. strips of solid wood vs. veneers or plies

[Idon84]

Completely incapsulating wood is out of the question for me.

Larry Pardey mentions strapping his rudders with copper & rivets and not even putting drift bolts in them. He does use resorcinol glue. Why he likes copper over bronze for this purpose is beyond me and is not mentioned.

There are several areas on the rudder of soft wood or where a worm got to work. The picture shows where the prop was prematurly wore away the paint on the rudder allowing creatures in. Overall thought they are nor serious.

I guess I can just fair up those areas and reuse the rudder for the next 2-3 years while taking my time to rebuild a nice clean and fair new one.

Usually I would agree with the using bronze over copper but the cost is probative for a patch job of just a few years.

I'm going to work on removing those drifts the next time I have a helper to lift it onto my workbench.

I don't know what I'm thinking... I guess I'll build a new rudder now. I've gone through everything else...?!

Thanks for your opinions, I'll be posting some more questions here in the next few days on a few other questions I've been saving up.

[bcooke]

Some of the planks of wood have separated from each other leaving voids in the rudder, only one has increased to about 3/16 of an inch wide (it is easily visible in the picture). Otherwise the thing seems quite strong and the bolts look to still be in good shape after about 20 years.

The picture shows where the prop was prematurly wore away the paint on the rudder allowing creatures in. Overall thought they are nor serious.

So, I lost track of this discussion, why does something have to be done to this rudder? Those gaps are completely normal in a wood plank rudder and are not a cause of concern. Once the boat hits the water the planks swell up and the gaps go away.

Rudders of this type last for a long time. Why change the design? I guarantee Larry Pardey wouldn't be encapsulating or sheathing a planked rudder (and neither would I). I guess I just don't see much cause for concern here. Its just a rudder. Cosmetics are not a factor and it seems structurally sound based on the descriptions.

[Quetzalsailor]

Earlier, I'd opined that I would not mind encapsulating plywood; I meant plywood that you'd made yourself laminated with epoxy. (I've made small pieces of plywood, laminated frames and a thwart with epoxy. My FD is now something of an epoxy bonded cold moulded hull; unrestored laminations are glued with Aerolite or Weldwood Urea resin and are suspect. I don't fear for the epoxy portions but the rest...) For serious or un-inspectable places, I would not encapsulate ordinary, even marine plywood because of the potential for water making its way through the glue lines. A good example of how bad that could be is to look at CDX sheathing grade plywood after a rain: poorly laminated places will be bubbling up even though the glues are Resorcinol.

As for the rot, or missing spots in that rudder: epoxy or glue in a couple dutchmen taking care to glue to the piece that's missing something; don't glue across to the next piece. You'd just be making a short bridge where the rest of the joint is merely bedded or loose and it will break unpredictably. A dutchman would have an 8:1 scarpf or better across the grain.

For drying, I recall that the rule of thumb is 1" of thickness per year for drying in air. That is, a 2" x X" wide rough board will take two years in adequate conditions. You might gain a little something by leaning it against your furnace this winter, but you'd be risking warping it by drying one side faster than the other. Of course, the drying will occur more quickly from the ends; that's why you see the ends painted in your decent wood lumber yard.