Rotten Balsa cored bottom

I have a boat that somone asked me to look at for some repair

The boat is a 1970's vintage and as best as I can tell the hull outer skin and gelcoat are in good to very good shape on the outside.

The inside however is a different story, as best as I can tell the hull was layed with gelcoat in a traditional open mold. the schedule appears to be

1. Gelcoat
2. fairly thick chopper gun applied CSM
(no additional cloth ontop of CSM)
3. grid scored balsa core covering the whole boat bottom
4. mat & 24 or 30 oz roving 1 layer on top of balsa core
5. stringers solid Mahogony 1 layer roving tabed ontop Balsa outer skin

So the balsa is a black gooey rotten mess and the stringers are soft
The main concern is how can the poorly wet out and rolled out original CSM that is contaminated with 20 years worth of rot be cleaned to a point where a proper repair can be made??

Secondly since the hull will have no apparent structure once the stringers and the inner skin of roving are removed is there a pratical way to approch such a repair to make a sound new lamination and have the hull keep its shape ?
Or does it sound like one to turn and run from.

I'm sure this has been delt with before, I'm just not sure how or if I should proceded.

Thanks to all for any insight or feedback you may have

 

Never, in my life, have I seen such a laminate schedual beyond, perhaps, a shower surround. IMO, once you touch this thing, you are taking people's lives into YOUR hands. I wouldn't want it on my conscience. Sorry, but if the schedual you have relayed is correct, this is a seriosly deficient boat that has no right to exist. You state that the "hull outer skin and gelcoat are in good to very good shape on the outside". I do not see how this can be, as the water that ruined that balsa came directly through that laminate without much slowing down. It's a small boat, a little ski boat or something? Well, one could stabilize the shape, remove EVERYTHING down to the "heavy layer of CSM, grind it clean, dry it for months...oh, nevermind. Just walk away from this one.

 

Pescaloco,

When a laminate reaches this stage of deterioration- the core has turned to mush- there is, frankly, no economically viable way to repair it. Fixing the thing up will certainly cost far more, and take far more time, than you'd ever recover by selling it.

IMHO, the proper course of action in such a case (if you take it on at all) is to strip all hardware and equipment from the hull, and build a new hull from scratch. Stringer replacement is a pain, and seems to take almost as long as building a new hull; if there's balsa mush in the hull laminate itself, it will probably be cheaper, quicker and easier to start fresh.

 

Ok I definetly see what you are saying.

The owner has done the initiall excavation, so I may be wrong on the outer skin laminate schedule.

I only saw the thick mat layer in the hull bottom (where the owner cut out a large swath of glass and balsa) it is possibe maybe probabel there is cloth under it. it was just so thick and lumpy I guess I assumed.

Yes it is a small runabout type.
Let me revise a little and assume for now there is sufficient laminate in the very bottom of the hull skin

1. by what means do you clean this mess ?
2. If the layer of chopper gun applied mat has poorly wetted and packed fibers it all has to come out right ? It's a nasty job no matter what. I would just hate to get too deep and have both parties not happy. But I could really use the work right about now.

Thanks guys

 

Thanks
I was typing my reply to # 1 & 2 replies when you posted

For the sake of knowing I am still interested.
So any one please comment on how to prep such a mess if a repair were to be made

 

If a repair is to be made, you have to grind it down to substrate in which you have confidence. What appears dry matt may actually be where a bond-line pulled the matt apart in deconstruction, in which case it is a good thing (well bonded). Grind a bit with the nine inch and see what it looks like...do you get to solid glass? In any event, this is a horribl task in which you are about to partake. Good luck.

 

Thank you !

I know it looks horrible, perhaps you are right since I did'nt pull the balsa from the matt bed maybee it was the tearing loose that left the fibers white. I just assumed based on the general lack of care that shows in the assembly of the boat

I think I am about 95% decided to let this one pass on by.

Thanks to all

 

My advise:

As there are so many second hand boats around, to be picked up for a bargain, just strip this boat from its salvagable bits, then cut up the hull. This is a project which will eat up too much time to be cost efficient. You are better off finding another similar boat, perhaps with some local repair work, or a jammed engine, which can easily be turned into a nice boat in way less time.

One of my customers (a wooden boat builder) was once asked to do a restauration on an 8 meter (26ft) boat. After some poking with a screwdriver, he made up his mind: He cut out the piece of wood which held the build number, built a new boat, and scarfed in the old piece of wood, with the number. This saved him an estimated 1000 hours of labour.