Making a new rudder...how hard can it be?

Hmm. Except I believe mjcoon, above, was thinking of the cylindrical steel 'spline' which goes vertically through many rudder blades, and may well need increased lateral profile to grip the inside of the blade when it's deflecting water flow. My rudder, as on most dinghies with swinging/lifting blades, doesn't have that.
 
dancrane said:
Hmm. Except I believe mjcoon, above, was thinking of the cylindrical steel 'spline' which goes vertically through many rudder blades, and may well need increased lateral profile to grip the inside of the blade when it's deflecting water flow. My rudder, as on most dinghies with swinging/lifting blades, doesn't have that.
Click to expand...

Yes, though I would have called it a "spine" if I hadn't thought that stock was the right word. (Since a spline is more specific and expensive for this application.)

From Wikipedia:
Spline (mechanical), a mating feature for rotating elements
Spline (mathematics), a mathematical function used for interpolation or smoothing

I think that I now remember the wooden slab stock on my Enterprise dinghy which was transom hung on pintles with a swinging blade.

Mike.
 
I don't think ply is the right thing to use. You used to be able to get special ply which had all the grain nearly parallel. I don't think it is available any more as nobody uses it.
An osprey rudder can be quite loaded at speed, particularly if it is a deep profile.
I think I would be happier with either solid hardwood, laminated hardwood, softwood sheathed in glass/epoxy or some sort of glass/carbon/foam.
The Cherub dinghy website has a good article on rudder building.
The technique of profiling would work just as well with wood as with a foam blank.
You may be able to pick up something secondhand, as racing boats sometimes upgrade to lighter newer rudders.
My current dinghy has a Winder carbon stock and blade, very rigid and incredibly light. Would be £550 new though!
If you start to use the performance of your Osprey, you will appreciate the control of a good rudder.
 
mjcoon said:
...
From Wikipedia:
Spline (mechanical), a mating feature for rotating elements
Spline (mathematics), a mathematical function used for interpolation or smoothing

I think that I now remember the wooden slab stock on my Enterprise dinghy which was transom hung on pintles with a swinging blade.

Mike.
Click to expand...

Spline is also a long thin bendy stick. The mathematical spline is a numerical version of the drawing office spline used to fit curves around points.
 
lw395 said:
Spline is also a long thin bendy stick. The mathematical spline is a numerical version of the drawing office spline used to fit curves around points.
Click to expand...

Yes, sorry, I did truncate the list. A long thin bendy stick would not be much use on a rudder, either! Could have other uses, though...

Mike.
 
lw395 said:
I don't think ply is the right thing to use...I think I would be happier with either solid hardwood, laminated hardwood, softwood sheathed in glass/epoxy or some sort of glass/carbon/foam.
Click to expand...

I'm wary of using a more complicated construction process than my ability is equal to. So I thought just wood, as being tolerably easy to sand/plane. I hadn't realised that ply wouldn't be ideal; certainly I won't want any warping. I don't mind shelling out for a quality piece of hardwood, then committing half the winter to perfecting the aerofoil shape...but which wood is best?

The present rudder is over 2kg weight...I'd prefer that a replacement wasn't much heavier. I guess strength matters more though. Any idea what a teak 32mm plank, 4' x 1' will cost?
 
dancrane said:
I'm wary of using a more complicated construction process than my ability is equal to. So I thought just wood, as being tolerably easy to sand/plane. I hadn't realised that ply wouldn't be ideal; certainly I won't want any warping. I don't mind shelling out for a quality piece of hardwood, then committing half the winter to perfecting the aerofoil shape...but which wood is best?

The present rudder is over 2kg weight...I'd prefer that a replacement wasn't much heavier. I guess strength matters more though. Any idea what a teak 32mm plank, 4' x 1' will cost?
Click to expand...

I suspect a lot more than you are willing to spend, and your boat is worth.
 
Dan

Don't use teak. Use a Western Red Cedar as per my previous post or for that matter foam.

But in all seriousness, the difference in weight between a carbon foam rudder and a plank will be less than the water soaked into the old girl's hull, your lazy jacks and rowlocks. Priorities sir, priorities. I'd also say that unless your existing rudder is structurally failing...why bother? You mentioned chunks are falling off it...why not just give it a very aggressive belt sanding, re sheathe it and fair it?

You will be surprised at the cost of materials to make a new rudder, and the skill required too. I would not even consider making a rudder for a boat like an osprey unless I really knew what I was doing and I vac bagged it.
 
Iain C said:
Don't use teak. Use a Western Red Cedar as per my previous post or for that matter foam.
Click to expand...

Thanks for that. And you're right, weight is no big issue for me...and I'd agree, re-sheathing the old rudder sounds a smart simple solution - except that substantial chunks have dropped off, and I don't want to end up making a new one from scratch, halfway through next summer.

mrming said:
Your what now?! This is a dinghy is it not?!!
Click to expand...

Where have you been, Mr Ming? All good ex-competitive racing dinghies were wearing LJs this year. Effortlessness is the new performance. :rolleyes: I'll dig out a photo if I can find one.
 
Iain C said:
Dan

Don't use teak. Use a Western Red Cedar as per my previous post or for that matter foam.

But in all seriousness, the difference in weight between a carbon foam rudder and a plank will be less than the water soaked into the old girl's hull, your lazy jacks and rowlocks. Priorities sir, priorities. I'd also say that unless your existing rudder is structurally failing...why bother? You mentioned chunks are falling off it...why not just give it a very aggressive belt sanding, re sheathe it and fair it?

You will be surprised at the cost of materials to make a new rudder, and the skill required too. I would not even consider making a rudder for a boat like an osprey unless I really knew what I was doing and I vac bagged it.
Click to expand...

I tend to think I'd either want to do a really god job out of carbon, or for a non-racing boat modify something secondhand.
 
lw395 said:
I tend to think I'd either want to do a really god job out of carbon, or for a non-racing boat modify something secondhand.
Click to expand...

I doubt I've the skill to do a really good job in high-tech stuff. I just don't want my crumbly-but-adequate existing rudder to fail and leave me unable to sail until I can find another...

...and considering how rarely Osprey 2nd-hand rudders are available, I need to be prepared to have a go at making one, however low-tech the material.

mrming said:
You have actually done this?! As they say on the internets, pics or it didn't happen. ;)
Click to expand...

Not sure why it sounds so unlikely. I've found the lazyjacks a huge help - just as useful as roller-furling for the genoa (which I'm also fitting).

I've never worked out why no-one else has them. They allow me to lower sail rather than slamming up the beach, (or keep it lowered until I've launched and reached clear deep water) without having 100sq ft of mainsail and a loose boom sliding round the deck...and whenever I want to stop, row or take it easy, down comes the sail without filling the cockpit.

Admittedly I'm mostly alone in the boat, and it's a big one for single-handing, so reducing the chaos which racers seem happy to put up with, was high amongst my priorities...

...hence also the reef I sewed in to the main, visible in the picture below.

View attachment 37226

Stoopid picture...why isn't it upright? It was, in my library...Not a good pic anyway...no battens in, and the sail is stretched out of shape. I was only drying it. How do I delete the old one, below?
 
Last edited:
It says "invalid attachment specified" when I try to click on it. Fair play to you though - I hadn't realised you were singlehanding. The Osprey has nearly half the sail area of my little First and no ballast. Not to be messed with.
 
Coming in a bit late here.
I made two rudders from Iroko. One for a Prelude


epoxiedblade.jpg


and one for my Seahawk 17.
Actually the one for the Seahawk was the first one I made for the Prelude. I decided it was too short so made the longer one for the Prelude and fitted the shorter one to the Seahawk which had that ugly shovel-shaped blade on the left. The pale area is the bit that was shielded by the headstock on the Prelude for a couple of months. That is because I only sealed it with epoxy and didn't varnish it. Both pivoting in the headstock.


newrudderblade.jpg

They were both lighter than the plywood ones they replaced.

I also sold the ply one from the 18ft MicroCup racer I bought

rudder.jpg
 
Last edited:
JumbleDuck said:
Teak would not be good for this: thick sections of it tend to distort horribly in damp conditions. My wee hunter came with solid teak washboards, both of which were horribly bowed. Marine ply is ideal for a rudder.
Click to expand...

Agree about the teak, but marine ply is not the most reliable material for a modern dinghy rudder.
A performance dinghy these days tends to have a deep rudder with not much chord, perhaps 3ft deep and 10 inches front to back.
Most ply is not stiff enough and will twist, and possibly snap at the base of the stock.
You could add fibreglass cloth and epoxy to get over that though.
But that's another £25 just for the epoxy....
 
It's an old dinghy which is not kept on the water. The iroko rudders I made were insitu on boats on swinging moorings for 3 years with no rot or distortion. It's an easy wood to work, light and strong. The only downside as far as I can see is that the grain runs both ways so planing and sanding has to be done carefully.
In Kendal we have a great wood supplier and if I give him a ply template he cuts and will thickness wood to shape.
 
Iroko is good, I've used bits on the Osprey already, though not for very wet duties on board. As long as it's warp-resistant, I'll have a try with that, and sheath it in glass or epoxy. Time, I have; money, less but sufficient for this, I hope. What will a 110cm x 25cm x 32mm piece run to, do you expect?

In spite of arranging a monstrously complicated but very effective 3:1 lifting tackle (and 4:1 lowering tackle, required to hold the blade down in use), plus cleats, I've still given the rudder's leading edge a battering on arrival at the beach. So I'm thinking I'll take a few inches of keel-band (required anyway, elsewhere on board :rolleyes:) to defend it. Good plan?
 
You must log in or register to reply here.

Share this page

Top