Inspecting lapstrake construction

Hello,

New member here. I signed on because I wished to know the best way to inspect a hull below the waterline, i.e. pulling fasteners, what to look for, etc.?

TIA

 

My first suggestion is to hire a reputable surveyor or boatbuilder. If you want to do it yourself, first learn about the type of construction. Also, ask about common failures on that kind of boat. Can you narrow your question more? For example give planking material, fastener alloy, framing material, etc.

 

Depends if it is in the water and how big it is. If it is a small hull, say <15ft then you are best turning it over (assuming it's on land) and then going about the inspection is the easiest. if you do this, block the hull up on the DECK EDGE. don't put any pressure on any sort of cabin (if it has one). If it's a big boat (out of the water, then chock it as standard before starting the "dry test".

The dry test: outside of hull

Wooden boats are usually easier to detect problems with than GRP boats. The things that go wrong, though are similar. First, sight along the hull, if there are any unwanted wrinkles or bubbles, there's a problem. Next go around the hull (take a pencil) and tap the hull in a 3" matrix (smaller for a smaller boat) use the pencil to mark the frames and any rot/delamination. The frames are denoted by a high pitch, and rot by a sort of dull (or squidging) sound.

The wet way: Outside of the hull

You can sight down the hull again, but scuba gear makes this a little clumsy. You can try tapping the hull for de-lamination/rot, but you can't always hear it that well. pushing and prodding is as good a method as any, but take care not to do more damage.

Inside the hull:

Life is easier and drier here, a combination of sight, sound and a good nose is all that is required along with a bit of obvious coloured tape (PVC Hazard tape is good). Mark any de-laminations or rot with a piece of hazard tape.

Actually repairing it:

Look around this forum. Often you can't do much close to the waterline with the boat in the water.

Hope this helps, my forte is really GRP but the inspection is the same,

Tim B.

 

Lap construction has some issues that can be solely found in them and most of the others that may be expected. In the water inspection requires diving and doesn't tell near as much as it would on the hard ashore. Fastener inspection at the hood ends, thru hulls, keel or skeg bolts, struts and shaft pinnings, etc. can be obvious places to look over the metals that hold things together. The condition of the planking material can be looked at closely in the bilge as can other structural members, like frames, floors and stringers.

Gonzo is correct, in that a good surveyor or boatwright is your best bet. There is a great deal of information, experience and understanding necessary for accurate assessment of any boat's structure. You could learn the material, gain some experience and have at it yourself, but this may take more time then you have to spend on this inspection.

What boat are you interested in?

 

RE: lapstrake construction

The boat is a 40' Chris Craft, not sure the year, thanks for all the info I have recieved already

 

That would be a plywood lapstrake with bolted through planks. The seams are set on lifecaulk.

 

I have a 1960 lapped Chris in my yard now. There are several locations you may find useful information in, but it may require some crawling around in areas of the boat most don't like to be. Check the engine box(s) for an identification plate. The bulkhead at the helm is another location you may find stamped or printed plates with year, model, serial number, etc. on them.

A quick check in one of the books on Chris Craft will narrow your search considerably. There are a number available from on line book sellers, for both new and used books. What is your interest in this vessel? Do you wish to buy, just curious, helping out a friend? The state registration number found on the sides of the bow (in your case NJ something, unless the boat is registered in another state) or the federal registration number (found carved or bolted to a strong, heavy structural member) will provide you with the year, model, displacement, engine, hull material, etc.

A picture and a few specific questions may serve you better in terms of responses you can use, in what ever effort is on going with this craft.