Raised hull
Swan 411, 1978

After 8 days at sea and winds of 35-45kts, have found a raised section of glass on the starboard side, below the shrouds, about midway down the top sides. The indentation is 12x24 inches with the 24 inches running the length of the boat (photo attached).

Has anybody experienced the same thing? Can anyone provide insight as to the cause and what the remedy might be?

Raised hull

Dear Charlie,

if this is not a problem on the gelcoat surface (or an old reparation, or, in case the hull has been re-painted a problem with the primer) can you post a jpg of the same spot from the inside of the boat?

Thanks, and fair winds!

matteo (38/067 Only You)

Charlie:

Your picture does not show clearly what is going on. In the photo caption, you call it raised hull, but in the text, you call it an indentation. First, which is it? I am assuming it is an indentation, and is the result of high shroud loads on that side of the boat, either from initial tensioning or hard sailing. My guess is if you look carefully you will also see a slight raising of the deck where the shroud fitting is on the same side of the boat.

On my 411 the previous owner saw the deck lifting and had the knees and upper topsides stiffened with carbon fiber on both sides of the boat. Since I bought the boat, I keep the rig tension on the low side. Over the years, I have seen many sailboat hulls pull in at or near the chainplates when the rig gets big loads which in your case might have come from the hard sailing, not initial rig tension. Most often the hull will come back to the natural position when the load is relieved.

If I am wrong and your topsides are bulging, then I will have to think some more or we'll have to call in the professor.

Please let us know what you find, and all the best of luck -

Geoff, Corazon, 411 #41

I nave a 47, anyway I think that there a similar construction method for these hulls consisting in longitudinal omega stiffeners filled with foam. Probably the bulging comes from age and not from particular stresses. There is probably already a discussion regarding this topic.
FV
Matteo 47/016 Grampus

Please check this discussion:
http://www.classicswan.org/forum/post_thread.php?thread=785
Matteo

Hi Geoff and Matteo,
Thank you for your replies.

Geoff--
The issue I have is one of a raised hull. It is very similar to the thread forwarded by Matteo. I wonder if it is stress related as you suggest.

Matteo--
The description and picture from the thread you forwarded is very similar to my problem. Though my raised area is much shorter in length than that shown in the other thread.

The cause for the problem (ie high temperature) does not fit with my experience. I just brought the boat south from Maryland to Florida and at no time did I experience temperatures that were close to the ones required as the ones described in the other thread.

I have attached a photo of the interior and have found no visible cracks from inside.

Could my problem be stress related as suggested by Geoff but with a raised surface, not indented surface? And if so, what implications does that have on repair?

Another question: new to Florida area and need a recommendation from the forum on best yard or individual in area to do the repair?

Regards,
Charlie

Quick note: photo needs to be rotated 90 degrees.

Hi Charles, I would not bother too much. I have, in much reduced evidence, something similar on my hull. Possibly the professor will clear better.
My opinion is the following:
Statically: a hull is a complex solid structure.
The external forces in equilibrium are the pressure of the water and the weight of the boat, forgetting the wind forces.
Internally there is to add the stresses from the fore and aft stay, the shrouds and the pressure of the mast on its base. This is the reason why many boats change their shape and some time side decks, and mainly the ends of the boat, aft and fore, go up, like the ends of a banana. This means that elastic deformation becomes in some areas plastic, and in some area here can be more evidence of the deformation.
Thermically: it is also possible that some stresses come from different thermal coefficient of components of the structure. In the case of the longitudinal stringers this might be also true because we have the internal structure of closed or open cell, therefore the air ancapsulated , having a much higher thermal coefficient than the solid, will expand or reduce much more than the encapsulating structure. A similar experience is told regarding the joint between fiberglass and lead in the case of the keel
Third, external shocks. This may be more evidenced in heavy seas or simply at mooring against the fenders in case of sea swall.

I think that you have seen many times steel hulls, expecially on ships. You will notice that you can easily read the longitudinal and the cross ribs.
. In this case either the longitudinal stringers are too solid and the outside skin is deformed or the stringers will swell or reduce under thermal action. The result would be the same.
I believe that fairing ( and repainting ) will reduce the appearance for a long time ( but expensive, helas!)
I believe that you will continue with a safe naigation, which I wish to you...
FW, Matteo

I can see from your picture, as it comes out from your post, a white horizontal line and a painted crack on the stiffener.
(in reality it is a vertical crack)
Can you check better, possibly I do not see it well,
Matteo

Dear Charles
With the chainplate knee inside the topside is locally much stronger here than in other areas, but I would suggest that the chainplate knee be closely examined for cracks and deformation, particularly at the height of the outside bulge. Spotcheck crack detection fluid is recommended, works well on GRP.
Also the inner end of the knee and its support to the coaming to be examined, and the shape of the coaming to be compared with the opposite side. Has the knee and coaming deflected slightly upwards on the affected side?
Kind regards
Lars

Thanks to all for these posts, what timing! Read this thread after posting about the same issue on Aorangi, so all of this information has been helpful in trying to understand. I believe if you see the photos on my related post from today, you will note a similar situation. (though a bit more serious perhaps) Will continue to follow this thread for input. Jayne 47/047 Aorangi

Hi there
My boat is on the hard in Portugal at the moment
She has this on both sides ,from bow to stern ,but more at the chain plates ,I drilled core holes and found the fiberglass not delaminated but pulled from the foam ,that is in the stringer ,as all gives me the idea that it is not a structure problem but more an eye sore ,we will fill, fare and paint,it appeared after 32 years ,and yes she sailed round the world but not in a hurry
philip

Hello everyone!
In any case this topic is a worrying issue. We do not have the problem (yet?) on 41/022 but it makes me wonder weather it would be a good suggestion to reduce the tension of the top shrouds when the boat is not used for long periods of time like we do for the stays. Our Soeur Anne has a tall rig with single pair of spreaders, which requires a rather high tension of the top shrouds. Professor: could you give us your opinion?
Merry Christmas and Happy New Year to all!
Philippe

Dear Philippe
When your rig is pre-tensioned as recommended - on the wind the leeward shrouds just begin to slack at the normal heeling angle - the load in them with the yacht upright is about 8% of the shroud breaking strength.
The chainplate knees should be able to take this, but a careful captain can unload the shrouds by opening the rigging screws a few turns just before arriving in harbour. and noting the number of turns so they can be put back before the beginning of the next trip.
Season's Greetings to all
Lars

Hello everyone!

Very interesting matter that we directly analyzed on our 44 with our Surveyor when we bought Pippus that has a limited bulge on starboard side as showed in the pic.
Our Surveyor, with at least 40 years experience in surveying, explained us that hull (blu star & stripe color), exceeded the temperature of the polyester resin in the hull laminate. In fact the boat have been parked for many years in a Côte d'Azur port with starboard side always exposed to all day long sun rays.
He said us that is not rare in dark colored hull but in white hull is more surprising.

Alberto
Pippus 44-011