Cobalt 232 swim platform repair

[84Ed]

I just bought a 2010 cobalt 232 with extended swim platform. There is a break or crack at the rear of the platform bottom "skin" where it meets the side in the area where the under mounted ladder would put pressure while using.

Anyone ever fix one of these ?
Thanks !

 

[alldodge]

Grind the gelcoat off, fiberglass matting and resin. Then re-gelcoat

Does the boarding ladder bolts go thru to the top

 

[84Ed]

No there is a "thread plate" within the body of the platform that ladder bolts to.
.bolts are tight so plate must be loose

 

[Scott Danforth]

the inner and outer skin are coming apart.

I would remove the swim platform, separate the two skins, clean out what ever glue failed.....then plexus them back together, clamp the halves, then re-install within an hour

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[84Ed]

I took the platform off and turned it over to examine. It looks and sounds 90% solid. (To the tap of a rubber hammer).

I can press it back into the original fit. Cobalt says its all composit in there.

I am tempted to pry open the crack enough to pump some a bunch expoxy or whatever is recommended and clamp it up tight.

Separating the inner and outer skins seems a lot more complicated to me (and for me). I am not a fiberglass guy.

Thoughts ?

 

[Scott Danforth]

tap method means nothing.

if you can mechanically clean out what failed, no reason not to be able to do what you describe. I would use plexus

the key to no mater what you do is getting the surfaces clean. and roughed up. for this reason alone, you may need to separate the whole seam

just pumping the area full of epoxy and not cleaning the dirt.grime.etc and roughing up the surface means that the epoxy glob will simply stick to the dirt

 

[84Ed]

Thanks Scott. I understand. I will probably need to open it up to see what is going on and clean/rough it up in there.

 

[84Ed]

So I cut a piece of the bottom skin out where the swim ladder bolts through the skin into the metal thread plates.
There is a dense foam filling the void between the top and bottom skins. The foam is very solid and dry.

It is cut out about 1/4" deep where the metal thread plates were glued to the foam itself. This is what came loose,, the thread plate to foam adhesion, allowing the weight put on the ladder to push on the bottom skin and break the seam at the rear edge of bottom.

They sure had a lot of faith in that adhesive holding the thread plates to the foam filler. !

Should I rough up the foam and the back of the thread plates and then use plexus with clamping ?
L

 

[alldodge]

It was a solid piece of glass with aluminum plate to spread out the load. The load is still spread out, but now most of the stress will be on the cut area.

I'm thinking taking it down thin on both pieces a few inches on each side. Then lay in CSM tabbing from center to outward. Might even think about getting a larger piece of aluminum plate to spread it out further

Hey @Woodonglass got some advice

 

[Scott Danforth]

you made more work for yourself now that you cut the skin vs separating the skin at the seam.

like AD stated, the force prior was only a few PSI over the whole surface, now its about 15 times that, concentrated over the seam you cut.

you will need to bevel back the remaining skin about 3" (throw away the piece you saved), and re-lay the area.

the core is no longer bonded to the aluminum. i would dig out the foam core in a few areas and bond the aluminum to the top side, then build up the layers of glass you cut out. first layer of CSM, then layers of 1708

this thread is proof that you dont need wood in a structure to have a 15 year design life. your swim platform lasted 12 years prior to a major repair.

 

[84Ed]

that swim platform is two levels with a lot of curves and coves. I wouldn't know how or where to split the top and bottom skins without tearing up all the bends and coves etc. Even at 1/8 " thick that bottom skin (that I cut ) was helping that much ?

I like the idea of coring out some foam and bonding the metal to the top layer in some spots.

 

[alldodge]

You could grind down to the glass and remove the edge and up the side. Lay glass in across the bottom and up the side. Smooth out and re-gel

Running bolts thru to the top will help but then the foam core will need to be solid because the load will transfer to the top skin

 

[84Ed]

Thanks for the advice guys. I am going to get some help from a local fiberglass guy.

I have put fiberglass on some structural members on my old boat, but never touched gel coat.

 

[84Ed]

I am going to bond some 3 " aluminum pieces to the the top layer, then bond the other side to the aluminum plate. I plan to use plexus ma310. Do I need the special plexus primer for bonding to the aluminum ?

Also, bonding to the top layer. I understand scuffing up the surface to help bond. Is an 80 sand paper enough or do I need to gouge out ruts to make the top fiberglass a better bond ?
This is all in prep for having a fiberglass man do the fiberglass work.

 

[Scott Danforth]

you will need to encapsulate the aluminum as aluminum tends to corrode easily

think more like 36-40 grit and less like 80 grit

 

[84Ed]

Encapsulate, as in plexus on all sides ?
The bottom and top of these 3" dia. Disc's, will be plexus coated to bond, and the sides also will bond to the foam filler.
Disc's are 3/4" thick.

 

[Scott Danforth]

bond them in, then fiberglass over them

 

[84Ed]

Ok I got it !

Thanks for your help