Can I make Centerboard and Rudder like this?

[dougworm]

I want to make a rudder and a centerboard and I can't find how to do that ANYWHERE! It will be replicants for a 14' Lido sailboat. The Centerboard is 1" thick at thickest points and its maybe 15" wide and 4 feet long or so. The rudder is about 3/4" thick and 12" by about 30" or so.

Originals were solid one piece Mahogany which naturally warped over the years. I am thinking that I ought to laminate their replacements? If so would Teak be a good choice? I happen to have a whole pile of Teak about 2 1/2" by 1 1/4" long enough for both rudder and centerboard. Would this be good to use? If not, what then?

I gather from other posted questions that if it is okay to laminate this teak for this application, (or whatever wood would be the best) that I should use epoxy ... but should I use dowels or biscuits or something or just but them right up to each other?

For shaping them should I feed them on edge through a tilted table saw blade? I know where and how much I want these tapered to a blade an age and I can picture cutting them for one side using the non tapered side square against the fence, but once I have the one side angle cut I am not sure how to do the same to other since now I have changed my square edge! The only thing I can think of is to use the pieces I removed and hold or even tack them back where they came from to recreate a square edge ... one I have all the angles cut I can picture blending all the hard angles into soft foil shapes.

Finally I am wondering if it would be good to cover the whole rudder and centerboard in fiberglass when I am done shaping it?

This is all of what I have dreamed up on my own, but I have no idea for sure if it's a good idea(s) or if I will be wasting my time and materials .. I need advice! HELP ME!!!

Doug, in Southern California

[Eric Sponberg]

Doug,

Teak would be OK. It is resistance to worm attack, and it glues with epoxy well. Yes, you can laminate with teak, and you can cover it with fiberglass. Dry wood is better than oily wood, so use the dry pieces from your stockpile of teak.

As for shaping the trailing edge, can you change the fence on your table saw to be higher so that the centerboard flat sides (before shaping) can lay flat against the fence? That would be the simplest way to go.

Eric

[Phil Locker]

No need to biscuit or dowel them - just slop on the thickened epoxy (careful clamping it all up though, as they'll want to slide around). If pre-contouring the strips by cutting them to approximate thickness, its more crucial that you line them all up on center. Clamp with several long F clamps (or similar). Then go at it with the brute force method of your choice - grinder / power plane / sanders - and compare to templates you've made of the foil section that you are trying to achieve (probably NACA 00xx). You can find online tools to generate the template and print it out - just websurf a bit.

Or save yourself a bunch of work and send it to a guy like me to CNC machine it for you ;)

By all means skin it with fiberglass after shaping - not only does it add strength, but it helps stabilize the strips (moisture content) so that they don't cup/warp later.

You'll find some design & fabrication tips online at http://www.philsfoils.com/TechInfo.html

Cheers
Phil

[wet feet]

I saw the question and it raises further questions.You tell us that you have teak and a circular saw.This is a good start but teak will be heavy and not particularly easy to shape.It will be best if the wood is quarter sawn and as has been said, dowels or biscuits are not needed and may even be a less than good idea if they swell later and distort the surfaces.A circular saw will remove wood but the start or end of the cut will need further work on the transition from square to foil shaped.If you can sharpen and use a spokeshave you can do the job.
If you follow Phil's advice and go for a foil section,do not attempt to completely shape one side and then the other.The two sides should be roughly shaped in alternate stages and only when you are within 2mm or so of the surface should you get serious with templates.The same problem afflicts CNC machining,it is easy to machine one surface and then the other but if the residual stresses in the core cause distortion the finished foil will not be as accurate as the trajectory of the toolpath.
Glass sheathing will make the foils much more durable and long lasting because it is such a horrible business that you will take really good care of them to avoid having to do it again.

[B. Hamm]

I'd say to replicate the foils exactly like the way they came with the boat, use them as a pattern. To to otherwise and you'll have a class illegal boat. If you're not racing it that may be of little concern, but it'll most definately effect the resale value.

Bill H.

[John ilett]

Another shaping technique if the section is parallel.
Once the laminated blank is thicknessed (with a thicknesser) then cut one end clean and mark on the section shape. Using a router with a fence and maybe a 1/4" bit cut longitudinal grooves to just touch the edge of the section. You may have about 3-4 grooves forward and aft of the max thickness. These are then very accurate guides to shape down to with an electric plane.

Not too keen on the teak, soft timbers are easiest of course and it also best to use one timber rather than mix different densitys which make shaping difficult.