TOPIC: Fiberglass-Deck Off the Hull, Restoration Any Boat

A few years ago I restored a 1972 Glastron GT-150. Now the reason I started this thread is because back in the late 1970’s to 1980’s I built boats for a living. I was actually in charge of the fiberglass end of it. We would pop the deck and hull out of the mold and sometimes when that happened, there would be imperfections like alligatoring and then we would repair that also. Well, a couple weeks ago I saw on here somewhere that someone was doing a deck off restoration, new stringers, transom, etc. on a GT-150 I think it was. He showed pictures of glassing the stringers in. That is not so bad. But when the plywood or sheet fiberglass floor is glassed in, I have noticed on several sites, a pretty big mistake being made when it comes to squaring up the hull. When a hull is built up in a factory, it is in the mold. It is not twisted, widened, or even elongated. There comes the mistake. When glassing in the stringers, then after it drys, the hull sets in a shape different than it was originally when it came out of the factory mold. When glassing in the floor, it is very important to first measure the width of the deck and match it to the hull. That is easy, you can just tape some thin strips of 1x2, or any wood for that matter to keep the hull from widening. If a mistake is made in the width, the hull can be squeezed together or even pulled apart (Apart is harder) when putting the deck onto the hull. The next part is more important. When a hull is out of square or “twisted”, it cannot squared back up after the glass dries and when the deck is “affixed” usually by rivets or screws, the hull will stay twisted after the boat is all put back together. However, unless it is really bad, many times the owner will not even notice it, at least until the boat is at speed, then it will be going lop-sided through the water! (Then he might just think the boat is heavy on one side)
It is very easy to keep that from happening. You need 2 straight edges about 12 inches or so wider than the beam. That way they will hang a few inches over each side. I usually use 2 perfectly straight 2x4’s. Glass in the floor. Put the straight edges/2x4’s on top of the hull. One fore and one aft. If you are doing this on a trailer like I was, you can tie the ends of them to the trailer. (Remember to have the wood strips holding the width of the hull at the correct measurement like I mentioned earlier still taped on). Get at the back of the boat with your eyes even with the top of the straight edges (front of boat is OK) and sight the 2 straight edges and make sure they are Perfectly Parallel. Like I said, tie them down to the trailer or tie them to weights. You can adjust the tension to pull more or less, thus lining up the 2 straight edges. Usually all you have to do is tie down three ends and leave the 4th one, the highest one, for last. Then pull down on it until it is right, sighting the 2 straight edges at the same time.
There you go guys! Do that, and you will have a perfectly squared up hull every time. Going through the water nice, straight and level (provided the weight is proportioned) Basically you will have a brand new boat, just like it was when it came out of the mold! Did it yourself too! Pretty good feeling! Take your family out, do some fishing... water sports, and if you braced your transom, jump a 120 feet through the air! You can be 007!
Z

I wish you had pics! I'm not visualizing it very good.

My boat is split and I want to use your technique.

Z28500 wrote:

you can just tape some thin strips of 1x2, or any wood for that matter to keep the hull from widening.

I think I get the rest of the details but can you describe "tape"?

this might be good to put on the main forum. this is not just limited to disco fiber.

I believe what he is referring to is something woodworkers call winding sticks. They are typically used to check the trueness of a board, but the same principle can be applied to hull of a boat.
Rather than tape, I just screwed a piece of scrap to hold the hull in place.
cheers
Bill