Leaking Lapstrake below waterline

[Legasea]

Hello, I am new to the forum and a new Chris Craft boat owner. We just purchased a 1968 38' Chris Craft Corinthian Sedan a month ago. We just traveled 100 miles up the NJ coast. Along the way, we popped two fasteners below the waterline. This boat was constructed with lapstrake bottom and carvel planking from the waterline to the gunnels. I believe the lapstrake is fir or mahagony marine plywood and planking being mahagony, please advise if this is accurate. We sprung a nice leak at the strake where the garboard meets the second strake. It is leaking right at the seam which appeared to be caulked but has blown out on the trip up. I am looking for advice on the whole repair process and how to best determine if there are more weak joints and seams. I am also not sure what type and size fasteners to use, I think they are silicon bronze through bolts between the frames and silicon bronze screws into the frames, not sure what size. I also posted in the Chris Craft forum trying to gain as much info on the original construction, fasteners and how to repair. Any help is appreciated... below is a link to a photo of the leak.

http://www.infussion.com/photos/NewToy/images/P1000090.JPG


Thanks,
Todd

[Lew Barrett]

There are a couple of items of potential concern in your image, but I am having a hard time reading it to see exactly what the nature of the leak is. In any case, the wiring of the bilge pump and the other visible items is egregious. Fasteners also seem to be poking through a plank in an irregular fashion. But I can't see where the garboard and first broad are creating the problem in your image, though I don't doubt that there is one.

I am not an expert in lapstrake construction, but if the seam is caulked, it would indicate an improper repair since that seam would rely on a tight wood to wood fit for it's integrity. No caulking required in this style, in other words. This would seem to indicate that wood replacement could be in order.

[Dale Genther]

Lew - I would agree with you as far as traditional lapstrake boats are concerned. However, the Chris Craft lapstrake plywood boats were done a bit differently. The two lapstrake CC boats I have are marine plywood with a compound between the laps that I believe is similar to polysulphide caulk. The planks on mine (1964 CC Cavalier Sea Strake 27) are held together with machine screws and nuts thru the laps.

Todd - As far as your problem is concerned. If the ply planks are in good shape, you can probably loosen the screws/nuts, separate the lap enough to clean out the mating surface, recaulk in between, then reinstall and tighten the screws/nuts. I have done this and with care and patience it worked. This is what I would try before I started tearing things apart. If the plywood planks are rotten or delaminated its a different story.

[Lew Barrett]

I won't argue that Dale, as I am admittedly not an expert on these boats. The wiring does have to go, though!

[Legasea]

We intend on going through the wiring on the whole boat, starting in the bilge and using watertight butt connectors with heat shrink tubing.....getting rid of all the Home Depot hardware we may find.

As far as the leak goes, I am hoping that the strakes and frames are solid. When i knock on them, they feel pretty hard from the inside and outside. What is the best technique to locate and remove the old fasteners? I assume i need to attack this from the outside of the hull even though I see the through bolts on the inside. Do I need special bits or tools? Once I locate the old fasteners, do I drill out the bung if one exists?

Thanks for all the replies so far, I am treading slowly and don't want to do more damage than good trying to get the old fasteners out.

[Dale Genther]

Sand off all the paint on the outside and you will probably be able to see where the heads of the fasteners are. There are probably not wood bungs over the heads, just a sort of hard putty. Expose the heads and with somebody holding with a screwdriver on the outside, unscrew the nuts on the inside. Then back the screws out from the outside with somebody gently pushing them out from the inside. The problem is that the nuts have usually become partially " buried" in the wood. Again I say: care and patience. The machine screws are probably no. 8 slotted bronze. I wouldn't reuse the old one, get some new ones.

BTW- there are probably wood screws, not bolts, where the planks are fastened to floors/frames.

Lew - I agreed on the wiring. My bet is that most if not all of the wiring on the boat should be replaced.

Also, that bilge pumps is only a 500 gph unit I'd install a much larger pump, or maybe more than one.

[Peerie Maa]

What is the best technique to locate and remove the old fasteners? I assume i need to attack this from the outside of the hull even though I see the through bolts on the inside. Do I need special bits or tools? Once I locate the old fasteners, do I drill out the bung if one exists?

Strip the paint on the lands where the fasteners will be, and identify what sort of bungs or stopping has been used. Search this forum for previous threads about removing bungs or stopping. Get into the boat with an angle grinder and cut off the nuts from the lap bolts. The frames look as though they are fastened with turned nails, if so you are better to drill off the heads from out side, but again search the forum first. Punch out the fastenings with a parallel punch of the correct size so as not to damage the fastening holes. Go several fasteners beyond the extent of the leak, and gently open the seam so that it can be cleaned and dried.

Then select the most appropriate claggum, (search this forum again :D) and its primer. Source replacement fastenings, one gauge larger than those you removed. Re fasten the lands, then redo the frames. You will need a helper for refastening, plus punches and a dolly.

[jackster]

Legasea,
Congratulations on your recent purchase, very old school boat, and it seems that you had an exciting trip up the NJ coast in an unfamiliar boat, loosing two fasteners along the way. Glad everything 'came out' OK!
Sounds like you found the right person to advise, he seems to know of which he speaks.
Dale Genther,
You are an example of what I think is great about this forum:
Knowledgeable answers and advice, generously and politely offered.
A refreshing tone from too many ' I know more and have more experience than you' and 'what an idiot to have done THAT' posts.
Thank you.

[Legasea]

To give everyone a better idea of the location of this leak, I am adding another pic from the exterior. I circled the problem area in blue.

http://www.infussion.com/photos/NewToy/images/leak2.bmp

[Legasea]

Once the repair is completed and the bilge is clean and dry, what is everyone's opinion on treating the bilge with CPES? Will it do more damage than good?

[Excalibur]

Hi Todd,

Copngratulations! We have almost the same boat. Mine is a 1967. Dale is certainly correct. Assuming that all is original, the bottom is indeed marine plywood cut into strakes, and the strakes are fastened with silicon bronze screws into the frames, and bolts lap to lap. The laps have Thiokol, an early polysulphide sealant between them. 3M Marine 4200 ( not 5200! ) is a good modern substitute.

You can only use CPES on bare wood, so you would have to strip all of the CC paint first. Won't hurt, may help, but that's a lot of effort. Once you get that leak stopped, the bilges should be dry. After that I would worry about keeping rainwater out more than anything else. I just spent $25k on repairing "rot from above". Good luck and wecome!