A Very Good Article for You!
The following applies mainly to older wooden boats. Those boats that we're built when oil based products such as oil based paints, red lead putty, tar, etc. we're being used. In other words most likely those boats built prior to the late 1960's.
Remember, since those boats were built with oil based products, that oil has over the years penetrated the wood and is therefore very reluctant to accept anything that is synthetic.
A fatal remedy for an older wooden hull is to overlay same with fiberglass. It won't attach itself properly to the oil impregnated planks. It will delaminate, separate and cause the wooden components to rot. This happens for various reasons. The fiberglass will not allow the wood to breath properly and water will accumulate in the delaminated areas. Especially in cold climates this will be fatal. The boat is kept nice and warm inside, but due to the presence of humans, the use of showers, cooking, etc. moisture is produced. This moisture attaches itself to the inside of the hull and works it's way through the wood to the exterior of the hull. When it arrives there, due to cold temperatures on the outside, that moisture will turn into water and while trapped between the wood and the fiberglass and not having proper air circulation, will cause deterioration of the wooden components. This can happen in a very short period of time.
Another problem is 'repairs', even small ones. For the same reason as described above, do not use any products such as epoxy, or other synthetic product. If a new piece of wood is to be glued to an existing member of the vessel, use a product called 'resorcinol' or other compatible glue. To fill seams that have been caulked, I say it again, do not use anything like M5200, or other neoprene based caulking material. Instead use red lead putty, or even cement. Another product that can be used and is very compatible and above all, cheap, is something you can make yourself. Go to a hardware store and purchase a powder that is used for the finishing of drywall. Get the outside variety and instead of mixing it with water, mix it with an oil based paint into a nice thick paste. First coat the area where it is to be applied; the seam, with a coating of oil based primer paint and then apply the paste with a putty knife. This stuff will bond well and after it has cured can be sanded if necessary. You can also use this to repair scratches or indentations in the wood. If used for fairing of the hull topsides, after sanding and the application of a coat of paint, you can achieve wonderful results.
Many wooden hulls, usually power boats, have a layer of wooden sheathing fastened over top of the planking. This sheathing is usually located just above and below the waterline. It serves to protect the hull from damage when hitting debris such as logs or other flotsam but is also often installed as a decoration, especially at the bows. The sheathing consists of wooden planks, often varnished, and are fastened to the hull planking with screws or nails. It is a good idea to keep a close eye on this sheathing since sometimes it becomes slightly separated from the hull. Also, while the caulking seams in the hull may have been properly maintained, due to inaccessibility, the caulking seams underneath the sheathing may have been overlooked. As water, fresh water due to rain, runs down the hull sides, this water may have entered between the sheathing and the hull planking. When this happens it is time to inspect the situation. In order to do this the sheathing will have to be removed. If everything is okay, or if the necessary repairs have been carried out, the sheathing needs to be re-installed. The sheathing can not be directly applied over the hull planking since that will not provide a proper watertight seal. What needs to be done is this;
Apply a good heavy coating of bitumus compound, this is a tar type substance used for roofing of buildings. Then put a layer of tar paper (also used for roofing) over top of the compound while it is still wet. Subsequently, apply another coat of bitumus compound over the tarpaper and then refasten the sheathing. This will provide a good water tight seal. Anything attached to the hull, such as copper sheathing, should be treated in the same manner.
Posted in Automotive repair Post Date 04/02/2017