Corribee Technical Section - RUDDERS

Reading members' letters and various articles in the Blue Book, Magazine etc., it seems that one of the few weaknesses in the Corribee design was the method of rudder mounting. In the early design the only thing holding the rudder to the boat was the tiller headstock fitting, consisting of a pinch bolt at the rear of the headstock and a "dog" screw at the front, going into a shallow hole in the top end of the rudder stock. With a phosphor bronze stock, and a brass or aluminium tiller headstock, there is plenty of potential for wear. Later Corribees were fitted with a skeg, which supported the rudder from below. This saved it from falling off if the headstock gave way. Also some boats were fitted with a modified design of headstock, which had a bolt going transversely right through the headstock and rudder stock. This gives extra security and takes some of the load of the pinch bolt and dog screw.

I had problems with the headstock last year, which resulted in losing my rudder in Poole Harbour. The problem has now been solved by having a new rudder built using two halves of rudder "mouldings" obtained from the Baltic Wharf Boatyard (formerly The Osmosis Centre) at Totnes. I use inverted commas as the "mouldings" were actually two halves of a plug for making a new mould. Norco G.R.P. Ltd of Poole produced a new rudder by using the plug as if it were a moulding. This may seem a waste of a plug, but the alternative was to create a new female mould from the plug, then mould a new rudder from that. As the plug was in poor condition for taking moulds from, and needed considerable work to clean it up, my Insurance company would definitely not have stood the extra cost involved. The plug makes a perfectly good rudder, although it is heavier as it has much thicker GRP.

Anyway, as I was creating a new rudder, I took the opportunity to extend the rudder shaft by 11/2" upwards and incorporate a collar below the headstock fitting, secured to the shaft by an M8 through bolt. When the rudder was fitted to the boat I inserted thrust washers under the collar to spread the load on the top of the rudder tube. My other modification was to have a spigot extended from the bottom of the rudder shaft for use with a skeg - if I ever pluck up the nerve to install one! The new metalwork was all in stainless steel, being cheaper, stronger and more readily available than phosphor bronze.

The final result gives me a securely mounted rudder but, as it involved losing my original rudder, I would be loath to recommend it as a course of action.

My new rudder is 2" shorter in height and 2" longer in length than the original. This has made it slightly heavier to operate, but it doesn't wander off course quite so readily when not being held.

Derrick Thorrington's letter in the June 1999 edition of the COA Newsletter gave a method of fitting a thrust collar which didn't entail losing a rudder first. He suggested cutting a gap in the rudder tube in the stern locker, well above the waterline, and inserting a loose collar in there, fixed to the rudder stock with an M6 through bolt. The stern tube would need extra GRP reinforcing back to the bulkhead, each side of the gap. If I used this method on my boat, the gap would probably need to be carried into the bulkhead, as the rudder tube is fitted tight up to it.

Ron Lunney has a simple method of making a new rudder blade. This involves using two pieces of 3/4" marine quality ply, shaped to be the left and right halves of the blade, and hollowed out on the inside to take the rudder stock and cross members. Screw the two halves together round the rudder stock, using West resin as an adhesive. After this has set, fill the screw holes and heads to give a smooth surface finish, coat it with more resin and clad it with woven glass cloth, tamping well to remove all air bubbles. Overlap the cloth from the two sides at the edges, and sand smooth when set. Finish with epoxy paint.

As Ron has helped build some 150 Corribees in his working life, and has also used this method to replace rudder blades on other boats, his idea is very welcome

One member has met a different problem with his rudder. As it is skeg mounted it cannot fall off, but the internal cross members have given up, resulting in the rudder staying stationary when the tiller is moved. His proposed solution is to drill carefully through the rudder leading edge and the rudder stock, then insert studding or similar bars through the holes and down the internal length of the rudder blade. The holes in the leading edge will then be resealed to finish.

Alan Baker

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Rudder and stock Knuckle

Moonwisp's tiller had so much play in it that at times it used to feel as if I had lost the rudder.

My fix for last season was to pack the knuckle tiller pivot hole, which had become elliptical, with plastic metal. This proved to be a good fix for two weeks, but soon slowly the play returned.

Having visited a number of chandlers without success, I visited the London Boat Show in search of a new 1 inch knuckle and tiller fixing. At first it appeared that all chandlers and boat yards had gone metric, but on close examination of the McNulty boat stand I was able to identify a beautiful stainless steel Knuckle and Brass tiller fixing that looked as though it came from the same mould as my Corribee's aluminium set.

I was quoted approximately £100 for the complete assembly (less laminated wood tiller) but alas it turned out to be metric - 2.5cm.

Well 2.5cm is as close to an inch as one would want to get, so I got and it fitted.

It only needed the length of the rudder shaft (bronze) and the bottom of the knuckle to be fine tuned with a file to allow the horizontal lock bolt (12mm) to line up with the hole in the shaft, and hence prevent the rudder falling off.

The whole task was completed on one turn of the tide on the beach at Weston Super Mare. (work time with hand tools approx = 1 hour including transferring the tiller which did not require modification).

Mc Nulty Boats - 0191 483 4836

Hedley

PS if you want the brass look be quick! McNulty are changing it to all SS.

May 2000