Topside Bulge and Buckling along Stiffener Dear Lars and All, We are currently preparing Aorangi for a new dress, and the following has arisen. There is bulging along the stiffener from midship toward the bow. Visible in photos. There is also buckling at mast level on both port and starboard which almost seems that there was excess compression.
The hole that was drilled showed the expansion foam in the stiffener to be separated from the fiberglass of the hull, and it is being considered to inject epoxy from the inside along the stiffener in question. From the outside it is deemed too invasive. Any opinions on causes, or experiences in regard would be very much welcomed. The fiberglass and the balance of the hull are in good shape overall. Thank you in advance. Jayne 47/047 Aorangi
Dear Jayne
You have a dark hull, and that increases the temperature effects, see the thread that Matteo pointed at June 2nd.
If it is worse near the mast this suggests the chainplate knees are also involved. Would suggest that you inspect the knees closely with crack detection fluid as suggested to Charles.
Are there changes to the bulges if you release the tension in the shrouds? Was going to suggest this to Charles, but he should check the coaming deflection first.
Not sure if the last photo shows that material is shaved away on the outside locally, would be advisable not to take more than the gelcoat as the topside is rather thin.
The foam inside the stringers is not structural, and there is no need to inject epoxy to glue it back to the fiberglass
Kind regards
Lars
Hi Jane, I will miss Aorangi at the rendez-vous.... I have too a very slight bulge on the topsides, much less than what I have seen on other pictures. I would suggest you, after my experience, to check too carefully the deck around the central shroud with the help of a flat board. Is there around the chainplate a bulging? In my case there was a 2-3 mm bulge. I had to disassemble in the cabin the wooden cover of the chainplate and some of the listels. I discovered that there was a crack on the fiberglass vertical rib connecting the chainplate to the keel. The repair was quite easy and quick, tensioning with a cable the chainplate to the keel, coming back to the old geometry, and fiberglassing again the rib. Anyway a lot of time spent for dismounting and remounting the interior. I hope this will not be your issue, anyway you may check easily this point from the deck, in case you have a similar problem, take care, Matteo, Grampus 47/016
Dear Lars, Thank you for your quick evaluation and response, but as always I took the leap of faith and allowed what you correctly surmised, and that is some major diving into the fiberglass on more than a few spots on the hull. (almost fainted at the hole in the hull) Still learning... They have begun rebuilding the fiberglass, and I can only hope that it will compensate for the material removed in the end. Would appreciate your thoughts on this reconstruction as to whether the new can marry the old in a satisfactory way. I will be having the crack check on the knees done next week, but the technical director of the yard is convinced that if the shrouds were lightened the bulge could have diminished at least in part. Now it is difficult, seeing all the sanding has been done to level things out. Should this still be done? There is no visible lifting on the deck, but this too will be checked at the same time as the knees (thanks Matteo for this suggestion) In any case, will report on the results of the testing next week, and agree with Matteo about the "pearl of wisdom"! That's why before undertaking any project it's good to consult the forum, and more than anything else not be shy about posting issues, or reading everything even if it's impossible to understand. Tend to be intimidated by technical info., but then Lars you bring it all down to an understandable level for those of us who are just passionate owners without a minimum of engineering knowledge! Thank you, and will be more careful in the future about the chain of events... Faithfully, Jayne 47/047 Aorangi
Dear Jayne
Thank you for the information
Slacking off the shrouds - there are reasons for and against. Would suggest that it depends on what is found in the knees, if they need repair the shrouds should be slacked.
Repairing the thinned areas of the topsides - laminate can not be added on the outside in the high areas unless spread out over a much larger area. If this is not practical the thin areas need to be cut out, and a new thicker laminate laid up with proper tapering along the edges. Epoxy resin recommended.
The white areas in the photos are filler, and it appears that the entire area along the stringer has been filled and faired earlier.
Kind regards
Lars
The bulging on Aorangi looks very similar to what is visible on the hull of Mandate. It is not easy to see, but from a certain angle there are definitely two raised sections on the hull along the stiffeners. I believe it's purely cosmetic, so I will leave it as it is for the time being. The bulging appears more on the starboard side then the port side.
I asked a surveyor and he suggested that a possible cause could be the effect of frost when the boat is stored out of the water in regions with a cold winter climate. This should mean that the stiffeners would be more moist then the rest of the hull. In freezing conditions the freezing water would lift the outside and cause the bulging.
I don't know if this is typical for 47's or if other types have the same issue.
Dear Gerrit, Beginning to understand that there are a lot of us in this club with bulging on our boats! Just in case you haven't seen the other thread from Charlie on June 1 it's quite useful and on the same subject. I think it's titled "Raised Hull". There is also a very useful thread mentioned #785 mentioned on this thread, which deals with the thermal effects playing in. Found all very useful and more than anything else comforting. Will be updating this thread with photos of the "after" as it happens just FYI Cheers, Jayne 47/047 Aorangi
Fascinated by this thread, my 47 Sarabande has the same visible lines along the topsides where the stringers are, very similar to Gerrits good photo. No issues around the deck and chain plate area I am aware of, but a previous owner had strengthened and lengthened the bolted straps where the shrouds come through the deck. As per other threads, I have re -rigged with Carbon and also race with hard modern sails which are developing a reputation for exerting more powerful forces in these areas. So far so good, but your comments and observations are warning me to keep a close eye on things. Good luck with the works on Aorangi!
Rob. Sarabande 47/029
Dear Gerrit
Your observations are correct. If one looks closely from a certain angle there are small ridges along the stiffeners on most yachts, and they are cosmetic. The surveyor's guess went astray, the reason is shrinkage in the polyester resin associated with the chemical curing process. More thickness means more shrinkage, and therefore a change of laminate thickness can be detected on a shiny surface particularly on dark hulls.
Epoxy resins have less shrinkage, but were not used at the time of building these yachts. For cosmetic repairs epoxy would be preferable.
Kind regards
Lars
Just want to wish everyone going to the Rendezvous a great time! We're still on the hard, and they are just now fairing the epoxy work getting ready for primer. (update attached) Until the next time around, fair winds and clement seas, and a great deal of fun to all!!! Jayne 047/47 Aorangi
Dear All,
While I have no idea how long the work done on the topsides will last, we are truly enjoying this moment of -undisturbed reflection-. The stringers are no longer visible, and the effect is magnificent, for however brief it will be.
A few photos of the finished effect.
Wishing everyone all the best in 2014.
Jayne
Aorangi 47/047
