Need advice on building a wooden rudder

In the process of restoring my 1953 wooden Snipe #9371, I discovered enough rot in my rudder to warrant replacement.

I'm thinking about building the replacement rudder myself, using wood construction to maintain consistency with all the other varnished woodwork I'm restoring on the boat (mast, boom, rubrails, tiller, splashguard, daggerboard handle, etc.).

I'm having a hard time finding some good guidebooks/articles on techniques and methods to do this, best types of wood to use, etc. I know I'll need to plank the boards alternating the grain pattern, plane it down and so on. I have the original rudder to use as a template, plus copies of the original snipe rudder diagrams for exact dimensions. I guess what I'm looking for is more of a description about the techniques used to join the planks, coat the rudder for strength, etc. Any ideas or firsthand advice greatly appreciated. Here's a link to my online album showing the progress and some of the problem areas: http://picasaweb.google.com/HerndonDad/Snipe9371?feat=directlink

 

Building in solid wood you may be familiar with the term, "quarter-sawn wood". This refers to how the wood is cut, and means that your pieces of wood have been cut from the inside of the tree to the outside. Every tree has several potential boards or planks that are most centered and therefore do not have a "preference" for cupping more to one side than the other. A quick check of the end grain shows which boards these are. There's no angle to the end-grain lines. They pass through the board with a slight curvature but do not angle.
These are the boards to use. The species of wood matters of course as well. If finishing "bright" you'll want to match the other wood in most cases. Mahogany, especially Honduras, is a superior boat wood due to its stability and resistance to rot. However, many woods can be used. White oak or live oak is commonly used on larger boats and it is extremely tough and rot-resistant. Again, quarter-sawn is most desirable.
Oak is very heavy, however, and mahogany is usually a best bet on a smaller boat like the Snipe, so I'll continue with that wood in mind.
Not only should you use quarter-sawn wood but pieces should be reasonably narrow unless the grain is perfectly square to the faces at the end. Reversing any angles, as you mentioned, will self-compensate cupping.
Mahogany loves epoxy so make it your adhesive of choice. Afterwards, varnish with at least ten coats and touch up religiously thereafter.
From a practical standpoint, plywood is the best all-around choice. Usually, two layers are required to get the proper thickness. Plywood also has the inherent advantage of telling you if your grinding/sanding/profiling is consistent due to the layers of crossing grain. Plywood is very stable and because it doesn't shrink/expand, you can lay some fiberglass cloth and epoxy over it and provide it with a tough outer shell that will resist abrasion as well as water ingress.
The downside is the grain, which will not match the other wood on the boat (and even if it did, it would only match on the cheeks). The edges would look horrible unless you like that sort of thing.
My fifteen foot sloop has a 1 1/2" thick rudder I made from plywood and it proves after years to be stable and easily repainted every two years. The color matches the hull and it is attractive enough.
Note: No coating provides strength. Epoxy help seal the wood and fiberglass adds abrasion resistance. Varnish on solid wood seals the wood enough to keep moisture transfer to a very slow pace, allowing internal moisture levels to be very even from side to side and elsewhere. The idea is that moisture content is not as big an issue as moisture consistency.

 

Plywood isn't a material I recommend for appendages, unless the boat is small, which a Snipe is. Plywood makes shaping the appendage fairly easy as the glue lines help you keep the shaping process relatively fair.

I prefer teak for solid plank rudders. Mahogany is pretty, but teak is too and it's neutrally buoyant, so it needs very little weight to sink with authority, unlike mahogany or other species.

Alan, what I think Smtoole is suggesting is a strip planked blade, which is my preferred method, if using wood for the appendages. Personally, I'm long since over using wood for this sort of thing, preferring inert materials that sink naturally, are absurdly tough and don't rot, but some just have to have wood, so . . .

Yes, Smtoole alternating the grain is desired and finding stock as straight grain as possible too is helpful. Square laminations are good and can keep the number of "strips" to a minimum. Use epoxy as the adhesive and consider a protective leading edge. My favorite for this is a epoxy saturated, piece of single braid, polyester line, set into a shallow groove. Fair this in with structurally thickened epoxy and you have a tough leading edge. Naturally, to finish the equation you'll want to encapsulate the blade, with a minimum of 3 coats of neat epoxy, then sheath the whole thing with cloth for abrasion protection. If looking for a "bright" finish, use 4 ounce or lighter cloth.

If the blade is going to be varnished, make the surface fair and smooth as possible before the 'glass goes on, because you can't fair it after it's on.

 

SCIRA has the plans and specifications for the rudder. A Snipe has a very restricted material and scantlings for everything. Snipes of that vintage had thin blades. Later they started using fat rudders which are more efficient.

 

Snipe rudder pictured


Instructions for build...remember the leading and trailing edge stock pieces are split in half and laminated together before the main stock is glued up.

http://mothboat.tripod.com/CMBA/Building/foils.htm

 

If it were my boat,I would go with the advice to use strips of wood glued together with a suitable adhesive.I would not be looking to use any heavy species as weight in the ends of a dinghy is known to be detrimental to performance.Unless the class rules prohibit the technique,I would use a sturdy piece of shockcord as a downhaul.

 

The class does not allow retractable blades. It is very strict. It says that "any boat that does not comply with the rules is not a Snipe" also that "anything not specifically allowed by the rules is not allowed".

 

If memory serves me, the Snipe's rudder is strip planked. If you plan on actively campaigning the boat, you'll need to follow class rules and guidelines. If not, you have an open book on your rudder. www.snipe.org is the place to start if interesting in racing the old lass.

 

Most of the Snipes I raced with wooden rudders had either a solid wood blade or a three lamination blade with a diagonal inner and vertical outer laminates.

 

Great feedback folks - I thank all of you!

 

I haven't been in one for many decades (over 4 anyway), but again I suspect the Snipe sites will have certified methods available.

 

Snipe 9371 restore update - rudder rebuild

Here's an update on this - I've cut the new rudder down to snipe rudder shape specs. Here are some photos.

Browse the whole online photo album here:
https://picasaweb.google.com/HerndonDad/Snipe9371#

 

Thanks for the update.

 

Very nicely done