Deck deflection

[Mougly]

Hello all again

I have an 81 Sonic 23 and have noticed some deck deflection around the deck stepped mast (no compression post).

I can not see any visible evidence of rot in the core or any cracking. the only other evidence I have is that the rigging is loosening and there appears to be a slight dip on the deck. (all standing rigging was inspected and is in good shape).

Some people have segested adding a compression post which I can remove when I am not under sail and put it in place when I am under sail to keep the deck from compressing any further.

Has anyone done a similar fix? Or can anyone offer any ideas on the best way to re enforce the mast beam without having to open the deck up at least not this season.


You can see pictures of the interior of the boat in my profile.
Cheers

 

[Ross]

There appears to be a beam athwartships just above your galley sink. Is that under the mast step?

 

[Mougly]

There appears to be a beam athwartships just above your galley sink. Is that under the mast step?

Yes that is the cross been which supports the mast. attached to it on either side are the chain-plates.

The is no sign of the chain plates pulling out or any cracks in the gelcote on the beam

 

[Ross]

The interior appears to be freshly painted. Was there damage concealed by a coat of paint?

 

[Mougly]

no the paint is original inside .

 

[BobM]

Perhaps the rig was too tight. The other thing to do is to follow how the load from the beam is transferred to the hull. Perhaps the failure is lower down. Are the cabin sides deflecting? Are the bottoms of the bulkheads sound?

 

[Mougly]

Perhaps the rig was too tight. The other thing to do is to follow how the load from the beam is transferred to the hull. Perhaps the failure is lower down. Are the cabin sides deflecting? Are the bottoms of the bulkheads sound?

There does not seam to be any noticeable problems with the bulkheads although there are what appears to be stress cracks in the gel coat on the outside around the chain-plates.
Although they do not seam to be getting any worse from last year.

What I am thinking of doing at least for this season is to create a compression post which I can put in place while sailing, would a 2" aluminium pipe be good enough to take the pressure to the keel?

Cheers

 

[Ross]

A 2X4 would be enough. Cut it just a little too long and thump it into place. Be certain that the bottom support is equal to the task.

 

[BobM]

I looked at the interior photos of your boat and it sure doesn't appear that there are any design issues with that overhead beam. Did you sound the deck around the mast? Just tap the deck with the plastic handle of a screwdriver. Pick an area in the center of the deck far from any deck penetrations as a control. It should emit a very sharp sound, where a wet area will emit a dull thud. A sound but delaminated area is somewhere in between. If you really are in doubt I suggest you find a local surveyor who knows sailboats and who will charge you buy the hour to inspect this specific problem with his (or her) moisture meter and expertise.

 

[wonkodsane]

My Sonic's got a little deck deflection, too. I haven't noticed any active flexing under sail, but it probably has a little bit. I am moving that boat inland (giving it to my dad so he can have a boat-sized hole in his wallet.) When we unstep the mast prior to transport, I plan on sounding the deck for water and delamination.

 

[Mougly]

My Sonic's got a little deck deflection, too. I haven't noticed any active flexing under sail, but it probably has a little bit. I am moving that boat inland (giving it to my dad so he can have a boat-sized hole in his wallet.) When we unstep the mast prior to transport, I plan on sounding the deck for water and delamination.

WOW there is another Sonic owner out there , have you had any issues with the shrowds loosening due to the deck deflection?


Also do you know where I may be able to get some specs on the boat?

Cheers

 

[wonkodsane]

I thought the same thing when I saw you on the board a year ago, I friended you on fbk because of it.

http://sailboatdata.com/viewrecord.asp?class_ID=290 is the only place I've seen anything with definitive dimensions and displacement.

http://sonic23.blogspot.com/ Has some more information, including a link to the original sales brochure

http://www3.sympatico.ca/garyeaton/nautalot/res/SonicBrochure.pdf

My shrouds are in pretty good shape, I haven't noticed much slackness in them. Obviously, the leeward side will be more slack when under sail, but that's the only looseness I've noticed.

 

[Mougly]

Thank you for the links I did visit a couple of them a while back. I was hopping to get some info on the rig tuning including the shroud and stay tension.

Cheers