Dear Matteo
Pls note that the keel is thicker forward. Keel sections have the longitudinal CoG close to the 42% chord line shown, and with this geometry the vertical CoG is 41% down from the top. Deducting the recess moves the total CoG slighly down and forward, to the right of the last letter in KEEL.
Kind regards
Lars
As soon as I will l get to the boat I will check on the owners book, what relates to crazes of the hull at the junction lead-fiberglass.
Thank you again and best regards,
Matteo
dear Lars and all of you,
this is the text on the owners manual related to the keel, section 1, page 2:
"Often on hauling, it will be noticed that along the joint between the hull and the lead keel there is a crack in the paint.
This is caused by different thermal expansion in the materials and should cause no problems.
If the crack gets too large, it can be filled with microbaloons and faired."
I confirm that I remember that in the letter shown from Nautor to the previous owner, the cause was the same but it was suggested to use a polyurethane mastic sealer, to cope with elasticity. Unfortunately I can not find this documentation.
I believe that this position is mainly due for limiting the warranty in case of claims, and most probably tightening the nuts with a larger washer as you suggest would give better results.
Anyway It is again another job to be made in the shipyard..:(
Lars, do you think that it would be better to tighten the bolt with the keel suspended, so that it goes up squeezing the crack? Or will be the effort of the torque on the teeth of the thread too high?
I attach a few pictures showing our work around the aftmost keel bolt. As discussed, we removed all of the material in the narrow section of the hull where the aft bolt is. We took it back to the laminate - exposed the cracks which had become sodden with oily bilge water and re fibreglassed the area. We re- filled the deep V section where the long bolt is and fabricated a stainless steel wing washer shaped to fit the hull. The idea was to spread the load. The fabrication slightly interferes with the flow of water into the bilge - we left small channels. The picture shows the longest bolt and locking nut emerged through the stainless steel piece and you can see the shorter 2 nd bolt going forward.
Dear Matteo and Rob
Keel bolt tensioning is best be made with the hull resting on the keel, and the joint/crack firmly closed.
On Rob's photo a big opening in the floor is visible - this is not good, allows flexing. Such openings in this and other floors in this area should be closed using double bias reinforcements, with a hole left just for drainage and hoses, preferably on the centerline.
If you can give the height and spacing of such floors a recommendation for the laminate thickness can be given
Kind regards
Lars
Perhaps the photograph does not show the installation accurately. The Keel and hull have a completely tight join. There is no gap between the new fabrication and the hull. You may be mislead by the gap between the 2 vertical sections of the fabrication which are cross members, and the base of the steel which is in shadow ( and submerged beneath a pool of dark water) This is the gap we left to allow the flow. The 2 extended wings which are shaped to bare on the hull are secondary to the flat section around the bolt itself which is acting as a large washer.
Dear Rob
Sorry for being unclear - my comment referred to the GRP floor in the background above the shorter next bolt, and the big opening visible there.
Kind regards
Lars
Dear Lars and Rob, my boat is a mark I version, the one with the large aft cabin and the C-shaped dinette. It might be possible that you have a mark II version and that there is a different position of the bulkhead of the kitchen and chart table(more aft than mine). In my case I have a closed wall afore under the floor board. The same applies aft, where there is the latch of the wooden cage over the engine and under the stairs. There are only some holes allowing for piping and bilge water circulation . Is it possible that the mark II version has this bulkhead more abaft than the Mark I ? ( and the same with the bulkhead of the door of the aft cabin)? Anyway my boat appears different under the floor board, with full walls.
Thank you,
Dear Matteo
You are right, Sarabande is a Mk II, and the bulkheads are in different positions.
Enclosed the Mk I interior, is by the way not shown with the other Swan 47 information as presented under Swans by S&S.
Kind regards
Lars
Dear Matteo
You are right, Sarabande is a Mk II, and the bulkheads are in different positions.
Enclosed the Mk I interior, is by the way not shown with the other Swan 47 information as presented under Swans by S&S.
Kind regards
Lars
thank you very much for finding a copy of the accommodation plan mark1.
Checking the profiles of the two versions and making the confrontation of the shapes of the two engines, it looks like the engine of the Mark 1 is located around 20 cm more afore than the Mark 2, and has a lightly longer propeller shaft. It is not so easy from the low scale design, you might check better. Possibly it is the same in the real construction and the last bolt should be just afore of the low bulkhead of the engine, and under the container of the battery set .
We will see, and thank you as always,
Matteo, Grampus 47/016
Hello evryone!
This might be an old subject, but let me bring in a remark.
Lots of our darlings have a keel with a "swept back" shape and the joint with the hull is prone to suffer at the trailing edge when the boat is taken out of the water and resting on wooden blocks which ar either not horizontal or too close to the trailing edge.
As the keel is very narrow at this point its very easy to create enourmous compression stresses at junction with the hull.
As far as I am concerned on our 41 we never allow the yard to put a block under the trailing edge, but at least 20 to 30 cm away from it. In the early days we almost every year had to repair outside cracks developing at the keel joint near the trailing edge, and got rid of it it as described above.
Also its probably better to have the boat resting in a slightly nose down attitude to make sure there is not too much compression on the rear of the keel junction.
Hope this will help.
Kind regards and happy sailing in 2014 to all.
Philippe. 41/022
Hi Philippe,
your post is very interesting and made me realize something I was never aware of: all the S&S Swans designed before 1976 have the keel with a marked "swept back" trailing edge, while after that date the keel shape was changed.
In fact I thought that the difference between the 41 and the 411 was mainly in the aft underwater profile; only now I realize for the first time that also the keel shape is pretty different.
One never stops learning!
