This time of the year there are always a lot of questions regarding the use and cost of shrink wrap vs tarps. I owned a shrink wrap company in New England (Fall River MA to Newport RI) for 4 years before I moved South. My partner still runs the company 10 years later. We wrapped over a 100 boats a year early on and he does over 150 year now. Here is my view on the benefits and downfalls of shrink wrapping.
The first issue to discuss is always the cost. If you are interested in getting a boat shrink wrapped, find an independent guy that does it vs going through a marina or boat dealer. We wrapped boats for several marinas and I can tell you that they mark up the cost to you at least 50-75%. There is no doubt that a tarp installed by an owner is the cheapest route. Even if you only get one season out of a poly tarp it will be cheaper than shrink wrapping.
The issue of mold and moisture problems on a shrunk boat are solely due to the moisture content in the boat the day it was wrapped. The most important part of the job is to ensure that on the day your boat is getting wrapped it is as dry as possible. Any water in the bilges or general dampness in the boat will just turn into it's own weather sytem under the wrap for the entire winter, it's like a terrarium. Unfortunately far too many boats are wrapped under less than ideal conditions and trust me the water in that boat the day it is wrapped will cause you problems. No matter how many vents are installed the original moisture is going to cause you problems. Basically it will "rain" inside your boat with the normal cycle of a warm day and cooling nights. It is the boat owner's job to make sure the boat is 100% dry before you let anyone wrap it and that is the challenge to ensure a dry interior throughout the winter.
Another thing to consider is where the boat will be stored. You
cannot store a shrink wrapped boat under tree cover or anything that could drop icicles on the wrap, they will most likely go right through. I once wrapped a 24 Formula and when I showed up the boat was under a big tree. I convinced the owner to move it and then wrapped the boat. Two months later in December he called to say my job had failed and his boat was full of ice and water. Went to look at it and guess what, the boat was right back under the tree that was thawing out from a freezing rain and dropped ice right throught the wrap in numerous places.
That was the only "failure" I ever had on at least 400 boats.
The other consideration is how far down the side to come. I always felt that the right way was to go right down the sides to the waterline and protect the hull finish. Shrink wrap comes in 4 foot wide increments for the most part and on even 8 foot beam boat with a T-top you need more than a 16 foot wide roll to come down the sides. Going to a 24' wide roll will only coat you $20 or so in material, labor remains the same. The cost of material is higher obviously with the wider rolls. If you take a string and hold it at your waterline then go up and over the T-top (or other highest point) and down to the opposite waterline, that string length is the width of the shrink roll that should be used. To save a couple of bucks and only go to the rub rail is not a good choice IMO. One of the benefits of shrinking is the fact that the wrap will actually shrink up to 50% of it's area as it cools. The square footage of wrap from the rub rail to the waterline actually helps to make the whole job "tighter" without worrying about putting too much heat on the wrap near a canvas T-top or other delicate parts to heat.
In snow country we never had a snow weight failure. Sometimes a wet snow may build up a bit and you will see some sagging but it will not cave in the wrap that I have ever seen. When the snow melts the wrap will go right back to it's original tightness. If the boat is wrapped right the finished product should be very tight (as in drum tight), sloped and typically will not allow snow to build up. A relatively "flat" boat like a bow rider with a low windshield is perhaps the hardest boat to wrap correctly because there is no slope. If you make a vertical 2x4 pole with a plywood base near the center of the boat and cover it with carpet we then run line or strapping from the bow to the post and then back down to the stern cleats or transom tow eyes to create the slope. Sharp things like antenna mounts, rocket launchers etc need to be covered with carpet or sometimes even just shrink wrap tape or during the shrinking process these points may poke through the wrap as it shrinks.
As an owner you need to decide if the cost has value to you just like any other money decision on boats. Add a door which will cost you about $25 and can be used over again for a few years. That will allow you access into the boat throughout the covered period if needed.
If you store in a marina chances are that the marina will not let an independent come in and shrink your boat so the cost will reflect the marina mark-up which as we know can be substantial.
We only had one boat yard that would let us direct bill customers at our normal rate, the majority would mark up our cost over 50% and bill the customer from the marina office.
We have all seen new boats travelling the interstate at 70 mph with the shrink wrap not even moving in the wind. That is the testimony to how good a wrapped boat will hold up to the weather if done right. I once wrapped a Saberline 36 hull #1 in RI for transport to the Miami boat show. The fly bridge was off and wrapped separately. The dealer told me the boat had not a tear after travelling 1200 miles at 70 mph and that thing was the shape of a barn.
Trying that with any kind of poly tarp would be futile and the tarp smacking your hull under 70 mph winds will scratch your gelcoat.
If any THT members are within 30 miles or so of Newport RI, drop me a PM and I will get a good wrapper to give you a fair price. I have no ownership, interest or take any commissions from this company. The guy just does good work at a fair price and is a boat nut like most of us so he cares.
The Hull Truth about Shrink Wrapping 
