ETAP 22 - Replacement rudder

I would certainly recommend contacting David Morris, although I would be surprised if he has any rudders. Is it an ETAP 22 or 22i?

I have some pdfs that show the outline shape but not details which I could send you. Do you have the existing rudder to measure? If not you might need to find another boat to look at.
 
rjp594 said:
I would certainly recommend contacting David Morris, although I would be surprised if he has any rudders. Is it an ETAP 22 or 22i?

I have some pdfs that show the outline shape but not details which I could send you. Do you have the existing rudder to measure? If not you might need to find another boat to look at.
Click to expand...

Thanks for that, I called David Morris yesterday, what a mine of useful information! The value of the boat just doesn't warrant spending big money on a replacement, so building a new one looks like the way to go. I'm very lucky to have received loads of quality advice from the boat builders at Southwold Harbour in the method of fabrication. I have the top section, but am missing the blade. I do have the original handbook with the drawings, although they are a bit basic, but with these, the top section and some recent photos, I should be able to scale it.

Wish me luck!!
 
I think the Etap 22 has a transom mounted rudder and you say you have the top section so you need a new blade.
Design of a rudder is all a compromise so there is no reason for you to make one identical to original. The first thing to decide is the depth of the rudder. Deeper works better but is susceptible to damage from grounding and should be somewhat shallower than keel with a load of people in the cockpit. The area is what might be typical and seems right.
The rudder should carry some 20 t0 30 % of area in ballance ie forward of the pintle line. ie area of rudder tucked forward under the hull. This makes for a lighter helm load on your arms.
The most efficient bottom of rudder shape is eliptical. However in seeking balance you might have more area at the bottom forward. A curved leading edge bottom will be easier if it does hit the bottom.
Lastly the thickness to chord ratio. Now thicker in the forward 1/3 gives a better lift especially at low speeds but does give more drag at higher speeds. However the thickess will probably be dictated by the top section gap for the blade.
I would make the blade out of wood base with GRP over that. I would use polyester resin and fibre glass. Make the glass very thick like 6mm at least so start with quite a thin wood base. Use twill weave glass for the leading curved edge or cu the regular glass cloth on the bias. ie 45 degrees from weave. All this to enable easy wrap around the leading edge. Use extra layers vertically in the area of 1/3 chord to give the required foil shape and additioanl lateral stiffness of the blade. On my little boat with shy spin heeled at speed there can be a huge load on the rudder blade counteracting weather helm. You may not flog your boat so hard but you need strength in the blade. Obviously longer blade needs more stiffness.
I think you will find you can design and build an excellent rudder possibly better than original. Just remember best is a wooden male plug left in for a fibreglass rudder. Not a wooden rudder with fibreglass coating. If you do go to just thin glass over wood you need to use epoxy. With the thick GRP you need to apply next layers soon after first layer has hardened or "gelled" to get that chemical bond of layers. An interesting project. ol'will
 
Hi,

I have a 22i and although not near the boat at the moment, I could take some pictures and give you measurements later this week if that is any help. I'm not sure though whether the rudder for the 22i and 22 are the same - something David Morris would probably know.

Where are you based?
 
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coveman said:
Hi,

I have a 22i and although not near the boat at the moment, I could take some pictures and give you measurements later this week if that is any help. I'm not sure though whether the rudder for the 22i and 22 are the same - something David Morris would probably know.

Where are you based?
Click to expand...

Thank you Coveman,

I'm based on the east coast near Southwold, Suffolk.

I've still got the top section of the rudder with all the "mechanicals" and the beginning of the blade, so I can get the cross-section measurements. I have the drawings from the original handbook and recent photos of the rudder prior to launch, so I can use these to scale up some measurements.

Southwold Harbour boat builders have been hugely helpful in their advice with regard to how best to fabricate a new one. It's pretty obvious that purchasing a replacement is extremely unlikely, so build a new one it is!
 
Thank you William_H,

I've taken on board all you've said and will also be working closely with a local boat builder who're happy to advise me during the fabrication.

Wish me luck!
 
Y Ddraig Goch said:
Thank you Coveman,

I'm based on the east coast near Southwold, Suffolk.

I've still got the top section of the rudder with all the "mechanicals" and the beginning of the blade, so I can get the cross-section measurements. I have the drawings from the original handbook and recent photos of the rudder prior to launch, so I can use these to scale up some measurements.

Southwold Harbour boat builders have been hugely helpful in their advice with regard to how best to fabricate a new one. It's pretty obvious that purchasing a replacement is extremely unlikely, so build a new one it is!
Click to expand...

Now that's very interesting. I used to have an Etap 22 and, following a hard beat to Rum, found that the rudder blade was bent by about 30 degrees. I got it off the boat and removed the grp side pieces to reveal that at the site of the bend, almost exactly coinciding with the bottom of the side pieces, there was a crack stretching some 70% of the rudder's length, with the bend formed in the remaining 30%. Fortunately I obtained permission to use SNH's workshop and, with the blade held in a vice, application of heat from a blow torch and much hammering got it straight. I then drilled it and bolted on two pairs of gate hinges to bridge the crack. This temporary repair held perfectly until the end of the season when I took the rudder blade to a local engine restorer for welding.

It suggests to me that an owner of an Etap 22 would be well advised to remove the side pieces and have a look at the blade to see whether a crack is developing.
 
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Sounds as though you have it sorted - would you like a measurement of the total length (22i) from top to tip? or are you ok.
 
I don't know specifically abou the Etap, but many transom-hung rudders would benefit from a little more balance if making a new one. I.e. , some blade area forward of the pintle axis. The Impalas did this while I had one, it made a huge difference.
I don;t think there is much to be gained by sticking rigidly to the original profile.
 
Having very recently had to make a replacement rudder for our boat I would like to add that the IBTC at Lowestoft were exceedingly helpful with both knowledge and materials.
Well worth a chat with them or ask them for the right bit of wood.
Gordon
 
It never occurred to me that the rudder may have been made from steel as with Dave S. That to me is very poor design and cheap build. problem for OP is that if it was a steel rudder the cheeks of the top section would be too close for a decent thickness GRP rudder. But then if he has some section of rudder blade still in place it probably was not steel.
So yes rudder balde if deep does take a lot of stress sideways. More so with decent balance because you do not feel the load. OP in building a GRP rudder might well benefit by buying some carbon fibre cloth for the sides of the blade. Especially if he can find carbon with a predominance of thread in one direction. This used mainly on the area of thickest chord about 1/3 way from front. Don't assume carbon is expensive or difficult to use. it is just like glass but will not bend easily. he might also consider kevlar in the side layups. I bought some tape recently and was surprised it was not expensive. This has enormous tensile strength to go again on the area of max chord near the surface.
Yes ballance is good. The leading edge of the rudder should extend about 5 cms forward of the pintle line and cut out so it extends under the hull. ol'will
 
Thank you all for the helpful comments.

So, the plan is to have a single core of 6mm marine ply from top to bottom. The top section will then be built up with layers of bonded ply to the required thickness, less the grp covering, providing a solid mounting to the transom. The blade will be stiffened like the inside of an airplane wing, with 4 x shaped 6mm ply frames spaced horizontal and 3 x vertical. The spaces between filled with expanding foam, which will then be sanded back to meet the ply. Then all covered with 300g chopped strand, then 5 - 6 layers of 300g woven.

I'm intending to stick as close to the original as possible. I have all the measurements, except the full length, from the very top above the roller rest, to the base of the blade. I've scaled it from photos as best I can at 1580mm. If anyone can verify this I'd really appreciate it .

Thanks.
 
Will you use polyester or epoxy?
Polyester would be fine, but you need to check the foam is not going to dissolve.
Sheet foam might be easier?
The integrity of the leading and trailing edges is key, as well as not letting anything warp.
I think I'd want the aft inch or so solid GRP to avoid the possibility of damage getting to the ply.
I'm not sure how best to lay that up over a male former.....

The main strength is needed in the top half, particularly where the stock loads it.
You could use extra layers of unidirectional glass here.
 
There are a couple of guides to foil construction here;

https://www.boatpaint.co.uk/acatalog/datasheets/sp/Wooden Foil Construction.pdf

and here;

http://www.okdia.org/boat/manual/tm5_foil.php

that may give you food for thought. No doubt others are available.

While both of these guides relate to building for racing dinghies, so generally lighter duty than a yacht, bear in mind that speeds of 20 knots are not uncommon for high performance classes and at these speeds loads can be considerable - although not generally felt by the helm as the rudder should be balanced. Regardless of that, the principles will still apply with perhaps some modification to suit your application.
 
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