Hints and Tips



Sun Odyssey 35 Swing/Lift Keel

Sun Odyssey 35 lift keel review and tips by Jim Day


The mechanism for keel raising and lowering on the Sun Odyssey 35 is the identical system to the Beneteau 343, as can be seen from this Oceanis 343 drawing and the SO35 pdf download below:


Lift Keel drawing pdf


In fact the keel mechanism is a long keel with a plate pivoting out of the keel case. This is about 7ft long and acts like a long keeler in the marina. The keel has two wings which provide lift at speed, and damp the rolling motion at anchor very effectively.


The keel is wound up using a stainless long screw, which is accessed through the saloon table. You will see a small round bung in the tip. This is worked by a modified winch handle and is 102 turns. It lifts itself if you bump, but expect the screw to push the bung out of the table as it comes up really quickly. It is "quite" difficult to raise, but much easier to lower.


Below shows the casing removed when I was looking at the overflowing issue.

Draft is 1.2m plate up, loaded, and 2.1m down. Here is a photo showing the arrangement of keel and rudders.

Note the rubber boots on the bottom of the rudders. Do not lose one, as they are 70 quid a pop. They are held on with Sikaflex. The French seemed to be unaware of the correct quantity to use when building it, and I lost one. My replacement has not fallen off, as I guessed much better how much Sikaflex to use.


The rudders are about 25mm clear of the floor normally when the boat is sitting on the bottom. I have left the boat like this in the yard all winter, and it is very stable.

The boat sits well in mud, but you have to follow rules. This is Full Circle in a mud berth at Rochford, Essex.

but because there was very little water flow through that mooring, that there was a build up of mud over a month.

The issue with the mud coming into the boat by being hydraulicked through the keel box, should have been taken care of by Jeanneau's overflow system, but the flows through an outlet in the bottom of the boat near the keel. Doh.


This means that the mud won't let that water out, so it just flows into the boat. I had left the boat for 7 weeks, and I had over a 100 gallons of water in the bilges. I nearly gave up at that point, but its all OK now, no more ingress.


The fix was to put a new skin fitting/sea cock just above the waterline in the side of the hull and route the overflow to that. Problem solved. In fact I used the seacock in the bottom as my inlet for a seawater pump into the galley, so it wasn't wasted.


There has been one occasion of the keel stuck up in the box, and that was because I left it in that mud berth above fully wound up, then had her lifted out, and the mud dried in the box over winter. I cleared it with the barnacle hoe and the pressure washer in 5 minutes. The cure for that is to bring the keel up fully then back it off 5 turns to allow it to work up and down as it goes aground and rises again.


Below are images of a new mechanism - note the anode on the second photo.


The twin rudders used in the lift keel boats like the Sun Odyssey 35 need to be correctly aligned.


Marc Lombard (Designer of the Sun Odyssey 35 Lift Keel) provided the following alignment advice:


"You must set the rudders parallel, that is the "average best solution" as flow is not always parallel, but it depends upon the heel mainly, so best average result and at least as a basic reference trimming you must set them parallel the flow. To do this, with the boat ashore, you should set the boat first horizontal (the floor boards inside are horizontal, so you can put a level on the floor boards). Check with height of shear at midship with a laser level. Then trace a horizontal line on both rudders (or a mark on trailing edge and a trace on leading edge of both rudders), using a laser level. Then measure the distances between both leading edge, the between both trailing edges, at the level of the horizontal marks, they should be equal. If not proceed to adjustment and check again until the values are equal at less than 3mm differences. The rudders will then be set parallel".


The boat is not as fast as its fin keel cousin, due to the hydrodynamic drag of the keel, the wings, and the twin rudders, so do not expect sparkling performance upwind. However, on the beam, when the wind is around 14-15 knots, you will reach hull speed, around 8 and a bit knots (clean). The boat weighs 450kg more than its fin keel sister, to make the overall stability the same for the 2 versions, but also accounts for the sluggish light airs performance.


Note that Jeanneau did not alter the waterline graphics, so it sits a lot lower in the water.


Here is the Polar diagram for the SO35 lift keel, and also the stability curve.


and the stability curve.

The original saloon table is fixed, and is a weak point in the design, as it slides out to accommodate diners on the port side, but is easily broken. I am having a new table made now with drop leaves, and it means I will get another infill to make a Saloon double berth, or decent access to a single berth on the starboard side.


It is a roomy boat with a decent standard of joinery, but I have been working on mine for several seasons, and I have a long list still of things to improve. That is not a negative, as the boat works well at sea, but Jeremy Rogers is still inventing improvements to new Contessa 32s after 25 years, so its just an evolutionary thing.


I have changed the sails to Cruising Laminates, as the original Elvstrom sails were frankly rubbish.


Like all modern boats, she is best sailed flat, and reef early. 14 knots and 24 knots of wind is about right, and will see the boat whizzing then. My Cruising chute is 825sq ft, and is overpowering the boat at 15 knots.


Overall, I am still very fond of the boat, but I would never buy any new boat ever again, no matter what builder.


Jim Dew - Full Circle - Sun Odyssey 35 l/k